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  Subjects -> WATER RESOURCES (Total: 149 journals)
Showing 1 - 47 of 47 Journals sorted alphabetically
Acque Sotterranee - Italian Journal of Groundwater     Open Access   (Followers: 1)
Acta Limnologica Brasiliensia     Open Access   (Followers: 3)
Advances in Oceanography and Limnology     Open Access   (Followers: 11)
Advances in Water Resource and Protection     Open Access   (Followers: 11)
Advances in Water Resources     Hybrid Journal   (Followers: 43)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 13)
Agricultural Water Management     Hybrid Journal   (Followers: 38)
American Journal of Water Resources     Open Access   (Followers: 7)
American Water Works Association     Hybrid Journal   (Followers: 21)
Anales de Hidrología Médica     Open Access   (Followers: 1)
Annals of Warsaw University of Life Sciences - SGGW. Land Reclamation     Open Access  
Annual Review of Marine Science     Full-text available via subscription   (Followers: 11)
Applied Water Science     Open Access   (Followers: 8)
Aquacultural Engineering     Hybrid Journal   (Followers: 7)
Aquaculture     Hybrid Journal   (Followers: 31)
Aquaculture Environment Interactions     Open Access   (Followers: 2)
Aquaculture Research     Hybrid Journal   (Followers: 31)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 35)
Aquatic Geochemistry     Hybrid Journal   (Followers: 4)
Aquatic Living Resources     Hybrid Journal   (Followers: 11)
Aquatic Procedia     Open Access   (Followers: 2)
Aquatic Science and Technology     Open Access   (Followers: 3)
Aquatic Sciences     Hybrid Journal   (Followers: 12)
Asian Journal of Rural Development     Open Access   (Followers: 7)
Australian Journal of Water Resources     Full-text available via subscription   (Followers: 6)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 21)
Civil and Environmental Research     Open Access   (Followers: 19)
CLEAN - Soil, Air, Water     Hybrid Journal   (Followers: 20)
Computational Water, Energy, and Environmental Engineering     Open Access   (Followers: 4)
Cost Effectiveness and Resource Allocation     Open Access   (Followers: 5)
Desalination     Hybrid Journal   (Followers: 7)
Desalination and Water Treatment     Hybrid Journal   (Followers: 12)
Developments in Water Science     Full-text available via subscription   (Followers: 9)
Ecological Chemistry and Engineering S     Open Access   (Followers: 4)
Environmental Science : Water Research & Technology     Full-text available via subscription   (Followers: 6)
Environmental Toxicology     Hybrid Journal   (Followers: 9)
EQA - International Journal of Environmental Quality     Open Access   (Followers: 1)
European journal of water quality - Journal européen d'hydrologie     Full-text available via subscription   (Followers: 6)
Ground Water Monitoring & Remediation     Hybrid Journal   (Followers: 19)
Groundwater for Sustainable Development     Full-text available via subscription   (Followers: 3)
Grundwasser     Hybrid Journal  
Hydro Nepal : Journal of Water, Energy and Environment     Open Access   (Followers: 4)
Hydrology Research     Partially Free   (Followers: 12)
Hydrology: Current Research     Open Access   (Followers: 12)
IDA Journal of Desalination and Water Reuse     Hybrid Journal   (Followers: 2)
Ingeniería del agua     Open Access  
International Journal of Climatology     Hybrid Journal   (Followers: 25)
International Journal of Hydrology Science and Technology     Hybrid Journal   (Followers: 4)
International Journal of Nuclear Desalination     Hybrid Journal  
International Journal of River Basin Management     Hybrid Journal   (Followers: 1)
International Journal of Salt Lake Research     Hybrid Journal   (Followers: 2)
International Journal of Waste Resources     Open Access   (Followers: 4)
International Journal of Water     Hybrid Journal   (Followers: 14)
International Journal of Water Resources and Environmental Engineering     Open Access   (Followers: 9)
International Journal of Water Resources Development     Hybrid Journal   (Followers: 22)
International Soil and Water Conservation Research     Open Access  
Irrigation and Drainage     Hybrid Journal   (Followers: 12)
Irrigation Science     Hybrid Journal   (Followers: 4)
Journal of Aquatic Sciences     Full-text available via subscription   (Followers: 2)
Journal of Contemporary Water Resource & Education     Hybrid Journal   (Followers: 3)
Journal of Environmental Health Science & Engineering     Open Access   (Followers: 1)
Journal of Fisheries and Aquatic Science     Open Access   (Followers: 5)
Journal of Geophysical Research : Oceans     Partially Free   (Followers: 51)
Journal of Hydro-environment Research     Full-text available via subscription   (Followers: 9)
Journal of Hydroinformatics     Full-text available via subscription   (Followers: 3)
Journal of Hydrology (New Zealand)     Full-text available via subscription   (Followers: 1)
Journal of Hydrology and Hydromechanics     Open Access   (Followers: 2)
Journal of Hydrometeorology     Full-text available via subscription   (Followers: 6)
Journal of Limnology     Open Access   (Followers: 6)
Journal of Natural Resources and Development     Open Access   (Followers: 2)
Journal of the American Water Resources Association     Hybrid Journal   (Followers: 30)
Journal of Water and Climate Change     Partially Free   (Followers: 37)
Journal of Water and Health     Partially Free   (Followers: 3)
Journal of Water Chemistry and Technology     Hybrid Journal   (Followers: 9)
Journal of Water Process Engineering     Full-text available via subscription   (Followers: 4)
Journal of Water Resource and Hydraulic Engineering     Open Access   (Followers: 9)
Journal of Water Resource and Protection     Open Access   (Followers: 9)
Journal of Water Resource Engineering and Management     Full-text available via subscription   (Followers: 3)
Journal of Water Resources Planning and Management     Full-text available via subscription   (Followers: 48)
Journal of Water Reuse and Desalination     Partially Free   (Followers: 6)
Journal of Water Security     Open Access   (Followers: 1)
Journal of Water Supply : Research and Technology - AQUA     Partially Free   (Followers: 6)
Journal of Water, Sanitation and Hygiene for Development     Open Access   (Followers: 5)
La Houille Blanche     Full-text available via subscription   (Followers: 1)
Lake and Reservoir Management     Hybrid Journal   (Followers: 7)
Lakes & Reservoirs Research & Management     Hybrid Journal   (Followers: 14)
Large Marine Ecosystems     Full-text available via subscription  
Liquid Waste Recovery     Open Access  
Mangroves and Salt Marshes     Hybrid Journal   (Followers: 2)
Marine and Freshwater Behaviour and Physiology     Hybrid Journal   (Followers: 1)
Marine Ecology Progress Series MEPS     Hybrid Journal   (Followers: 24)
Marine Ecosystem Stressor Response     Open Access  
Methods in Oceanography : An International Journal     Hybrid Journal   (Followers: 4)
New Zealand Journal of Marine and Freshwater Research     Hybrid Journal   (Followers: 10)
Open Journal of Modern Hydrology     Open Access   (Followers: 4)
Osterreichische Wasser- und Abfallwirtschaft     Hybrid Journal  
Ozone Science & Engineering     Hybrid Journal   (Followers: 1)
Paddy and Water Environment     Hybrid Journal   (Followers: 9)
Research Journal of Environmental Toxicology     Open Access   (Followers: 2)
Reviews in Aquaculture     Hybrid Journal   (Followers: 9)
Revue des sciences de l'eau / Journal of Water Science     Full-text available via subscription   (Followers: 2)
RIBAGUA - Revista Iberoamericana del Agua     Open Access  
Riparian Ecology and Conservation     Open Access   (Followers: 6)
River Research and Applications     Hybrid Journal   (Followers: 16)
River Systems     Full-text available via subscription   (Followers: 3)
SA Irrigation = SA Besproeiing     Full-text available via subscription   (Followers: 1)
SABI Magazine - Tydskrif     Full-text available via subscription  
San Francisco Estuary and Watershed Science     Open Access  
Sciences Eaux & Territoires : la Revue du Cemagref     Open Access  
Scientia Marina     Open Access   (Followers: 2)
Smart Water     Open Access  
Society & Natural Resources: An International Journal     Hybrid Journal   (Followers: 18)
Sri Lanka Journal of Aquatic Sciences     Open Access   (Followers: 1)
Sustainability of Water Quality and Ecology     Hybrid Journal   (Followers: 4)
Sustainable Technologies, Systems & Policies     Open Access   (Followers: 8)
Tecnología y Ciencias del Agua     Open Access  
Texas Water Journal     Open Access   (Followers: 2)
Urban Water Journal     Hybrid Journal   (Followers: 14)
Waste Technology     Open Access   (Followers: 3)
Water     Open Access   (Followers: 6)
Water & Sanitation Africa     Full-text available via subscription   (Followers: 4)
Water and Environment Journal     Hybrid Journal   (Followers: 22)
Water Environment and Technology     Full-text available via subscription   (Followers: 16)
Water Environment Research     Full-text available via subscription   (Followers: 42)
Water International     Hybrid Journal   (Followers: 15)
Water Policy     Partially Free   (Followers: 7)
Water Practice     Full-text available via subscription   (Followers: 3)
Water Practice and Technology     Full-text available via subscription   (Followers: 14)
Water Quality Research Journal of Canada     Full-text available via subscription   (Followers: 4)
Water Research     Hybrid Journal   (Followers: 53)
Water Resources     Hybrid Journal   (Followers: 20)
Water Resources and Economics     Hybrid Journal   (Followers: 4)
Water Resources and Industry     Open Access   (Followers: 3)
Water Resources and Rural Development     Hybrid Journal   (Followers: 2)
Water Resources Management     Hybrid Journal   (Followers: 36)
Water Resources Research     Full-text available via subscription   (Followers: 81)
Water SA     Open Access  
Water Science & Technology     Partially Free   (Followers: 26)
Water Science : The National Water Research Center Journal     Open Access   (Followers: 6)
Water Science and Engineering     Open Access   (Followers: 9)
Water Science and Technology : Water Supply     Partially Free   (Followers: 22)
Water Wheel     Open Access   (Followers: 2)
Water, Air, & Soil Pollution     Hybrid Journal   (Followers: 25)
Water21     Full-text available via subscription   (Followers: 1)
Waterlines     Full-text available via subscription   (Followers: 2)
Western Indian Ocean Journal of Marine Science     Open Access   (Followers: 1)
Wetlands Ecology and Management     Hybrid Journal   (Followers: 21)
Wiley Interdisciplinary Reviews : Water     Hybrid Journal  
WMU Journal of Maritime Affairs     Hybrid Journal   (Followers: 3)

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Journal Cover Water Resources Research
  [SJR: 2.661]   [H-I: 144]   [81 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 0043-1397 - ISSN (Online) 1944-7973
   Published by AGU Homepage  [17 journals]
  • Long-term morphodynamics of muddy backbarrier basins: Fill in or empty
           out'
    • Authors: G. Mariotti; A. Canestrelli
      Abstract: The long-term (3000 years) morphodynamics of an idealized muddy backbarrier tidal basins is studied using a shallow-water hydrodynamics and wind-wave model (Deltf3D-FLOW-WAVE), modified to include fully-coupled marsh organogenic accretion, biostabilization, drag increase, and wave-induced marsh edge erosion. The latter process is implemented with a novel probabilistic algorithm. Starting from an initially empty basin with a uniform bed slope, a network of channels incise the mudflat, sediment is released, and marshes establish at the basin landward margin. If enough mud is supplied to the basin from the shelf, marsh progradation counteracts marsh edge erosion and marshes expand. Marsh expansion does not completely fill the basin, but leaves open a few km-wide channels, large enough for waves to resuspend sediment. Starting from a basin (almost) filled with marshes, a drop in the external mud supply or an increase in the rate of relative sea level rise cause the basin to empty out by marsh edge erosion, while the marsh platform, aided by reworking of the sediment released by marsh retreat and mudflat deepening, keeps pace even with fast rates (10 mm/yr) of relative sea level rise. Even if the marsh does not drown, the marsh retreats faster if the rate of sea level rise increases, because more sediment is sequestered to fill the newly created accommodation space and is thus not available for marsh progradation. This study suggests that prediction of marsh erosion requires a basin-scale sediment budget, and that edge erosion, not platform drowning, is likely to dominate marsh loss.
      PubDate: 2017-07-26T12:06:21.735195-05:
      DOI: 10.1002/2017WR020461
       
  • Homogeneity testing for spatially correlated data in multivariate regional
           frequency analysis
    • Authors: Tereza Šimková
      Abstract: Identification of homogeneous regions is a key task in regional frequency analysis (RFA) to obtain adequate quantile estimates for an event of interest. Recently, the frequently used univariate Hosking-Wallis L-moment homogeneity test was extended to the multivariate case. Multivariate L-moments are used as a tool to define the test statistic and copula models to describe the statistical behavior of the analyzed dependent variables. To avoid drawbacks in fitting a parametric joint distribution to the data and a rejection threshold which is based on simulations, its nonparametric alternatives were also proposed. Although the simulation studies performed demonstrated the usefulness of both the parametric and nonparametric tests, the powers obtained were valid only for regions without intersite dependence. Examples from practice nevertheless demonstrate that intersite correlation may be expected for some kinds of data. To overcome the problem of cross-correlation between stations, the parametric testing procedure is generalized using D-vine copulas to model intersite dependence when generating synthetic homogeneous regions during the testing procedure. Monte Carlo simulations were performed and illustrate how intersite dependence negatively impacts the multivariate L-moment homogeneity tests by significantly reducing their powers. The results of simulations also demonstrate the superiority of the proposed modification over both the original parametric and nonparametric procedures inasmuch as it improves the heterogeneity detection and avoids miscategorization of a region. The modified test is also applied in a case study for meteorological data in the Czech Republic.
      PubDate: 2017-07-26T08:50:45.233458-05:
      DOI: 10.1002/2016WR020295
       
  • Isolating roughness scales of gravel-bed patches
    • Authors: Stephane Bertin; Jane Groom, Heide Friedrich
      Abstract: There is a growing consensus that gravel-bed roughness should be parameterized based on bed-surface topography, not only sediment size. One benefit is the possible identification of various spatial scales of surface roughness and evaluation of their respective contributions to flow resistance (and also to bedload transport). The absence of relationships between roughness at the different scales is apparent in previous work, which currently limits roughness parameterization from topography and application in flow modeling. This study examines the use of moving-window detrending on gravel-bed digital elevation models (DEMs) for isolating roughness scales and their respective signatures. A large dataset of 35 water-worked gravel-bed patches from both the laboratory and the field was used for the analysis. The measured bed topography was separated into two distinct DEMs: one representing grains, the other representing small bedforms. For all DEMs, bed-elevation parameters measuring vertical roughness, imbrication, and spatial correlations were determined. Our results show distinct topographic signatures between grain and bedform DEMs. We show strong positive linear relationships between grain vertical roughness and the size of the bed-surface material. Surface sediment arrangement also determined bedform shape, with groupings of coarse sediment forming humps on the surface, and finer sediment sheltered in hollows. Patch-scale vertical roughness could not be estimated simply as the sum of grain and bedform vertical roughness. Instead, our results suggest weighted summation and the existence of universal weighting coefficients. Practical applications for studies on gravel-bed roughness and flow modeling using DEMs are discussed.
      PubDate: 2017-07-26T08:50:42.950186-05:
      DOI: 10.1002/2016WR020205
       
  • Abundance and morphometry changes across the high mountain lake-size
           gradient in the tropical Andes of Southern Ecuador
    • Authors: Pablo V. Mosquera; Henrietta Hampel, Raúl F. Vázquez, Miguel Alonso, Jordi Catalan
      Abstract: The number, size, and shape of lakes are key determinants of the ecological functionality of a lake district. The lake area scaling relationships with lake number and volume enable upscaling biogeochemical processes and spatially considering organisms' metapopulation dynamics. These relationships vary regionally depending on the geomorphological context, particularly in the range of lake area 104 m2, and 50% of the water resources are held in a few ones (ca. 10) deeper than 18 m. Therefore, mid and large lakes are by far more biogeochemically relevant than ponds and shallow lakes in this tropical mountain lake district.
      PubDate: 2017-07-26T08:50:31.863771-05:
      DOI: 10.1002/2017WR020902
       
  • Input variable sensitivity assessment for sediment transport relations
    • Authors: Roberto Fernández; Marcelo H. Garcia
      Abstract: A methodology to assess input-variable sensitivity for sediment transport relations is presented. The Mean Value First Order Second Moment Method (MVFOSM) is applied to two bedload transport equations showing that it may be used to rank all input variables in terms of how their specific variance affects the overall variance of the sediment transport estimation. In sites where data are scarce or nonexistent, the results obtained may be used to i) determine what variables would have the largest impact when estimating sediment loads in the absence of field observations and ii) design field campaigns to specifically measure those variables for which a given transport equation is most sensitive; In sites where data are readily available, the results would allow quantifying the effect that the variance associated with each input variable has on the varaince of the sediment transport estimates. An application of the method to two transport relations using data from a tropical mountain river in Costa Rica is implemented to exemplify the potential of the method in places where input data are limited. Results are compared against Monte Carlo simulations to assess the reliability of the method and validate its results. For both of the sediment transport relations used in the sensitivity analysis, accurate knowledge of sediment size was found to have more impact on sediment transport predictions than precise knowledge of other input variables such as channel slope and flow discharge.
      PubDate: 2017-07-26T08:50:28.481738-05:
      DOI: 10.1002/2016WR020249
       
  • Deriving adaptive operating rules of hydropower reservoirs using
           time-varying parameters generated by the EnKF
    • Authors: Maoyuan Feng; Pan Liu, Shenglian Guo, Liangsheng Shi, Chao Deng, Bo Ming
      Abstract: Operating rules have been used widely to decide reservoir operations because of their capacity for coping with uncertain inflow. However, stationary operating rules lack adaptability; thus, under changing environmental conditions, they cause inefficient reservoir operation. This paper derives adaptive operating rules based on time-varying parameters generated using the ensemble Kalman filter (EnKF). A deterministic optimization model is established to obtain optimal water releases, which are further taken as observations of the reservoir simulation model. The EnKF is formulated to update the operating rules sequentially, providing a series of time-varying parameters. To identify the index that dominates the variations of the operating rules, three hydrologic factors are selected: the reservoir inflow, ratio of future inflow to current available water, and available water. Finally, adaptive operating rules are derived by fitting the time-varying parameters with the identified dominant hydrologic factor. China's Three Gorges Reservoir was selected as a case study. Results show that (1) the EnKF has the capability of capturing the variations of the operating rules, (2) reservoir inflow is the factor that dominates the variations of the operating rules, and (3) the derived adaptive operating rules are effective in improving hydropower benefits compared with stationary operating rules. The insightful findings of this study could be used to help adapt reservoir operations to mitigate the effects of changing environmental conditions.
      PubDate: 2017-07-26T08:50:24.3625-05:00
      DOI: 10.1002/2016WR020180
       
  • Temporal variability in the importance of hydrologic, biotic, and climatic
           descriptors of dissolved oxygen dynamics in a shallow tidal-marsh creek
    • Authors: Natalie G. Nelson; Rafael Muñoz-Carpena, Patrick J. Neale, Maria Tzortziou, J. Patrick Megonigal
      Abstract: Due to strong abiotic forcing, dissolved oxygen (DO) in shallow tidal creeks often disobeys the conventional explanation of general aquatic DO cycling as biologically-regulated. In the present work, we seek to quantify the relative importance of abiotic (hydrologic and climatic), and biotic (primary productivity as represented by chlorophyll-a) descriptors of tidal creek DO. By fitting multiple linear regression models of DO to hourly chlorophyll-a, water quality, hydrology, and weather data collected in a tidal creek of a Chesapeake Bay marsh (Maryland, USA), temporal shifts (summer – early winter) in the relative importance of tidal creek DO descriptors were uncovered. Moreover, this analysis identified an alternative approach to evaluating tidal stage as a driver of DO by dividing stage into two DO-relevant variables: stage above and below bankfull depth. Within the hydrologic variable class, stage below bankfull depth dominated as an important descriptor, thus highlighting the role of pore water drainage and mixing as influential processes forcing tidal creek DO. Study findings suggest that tidal creek DO dynamics are explained by a balance of hydrologic, climatic, and biotic descriptors during warmer seasons due to many of these variables (i.e., chlorophyll-a, water temperature) acting as tracers of estuarine-marsh water mixing; conversely, in early winter months when estuarine and marsh waters differ less distinctly, hydrologic variables increase in relative importance as descriptors of tidal creek DO. These findings underline important distinctions in the underlying mechanisms dictating DO variability in shallow tidal marsh-creek environments relative to open water estuarine systems.
      PubDate: 2017-07-24T07:56:20.539069-05:
      DOI: 10.1002/2016WR020196
       
  • Generation of complex karstic conduit networks with a hydro-chemical model
    • Authors: Rob de Rooij; Wendy Graham
      Abstract: In this paper we present a hydro-chemical model that can be used to generate plausible karstic conduit networks that honor what is known about geology, hydrology and topography of a karst system. To make the model applicable to a range of natural karst systems, we introduce a flexible and physically realistic flow boundary condition along the land surface. Moreover, whereas comparable existing speleogenesis models use an explicit reactive-transport scheme, we propose an implicit reactive-transport scheme to permit a coarser spatial discretization of the conduit cells. An application to a real karst system illustrates that the model can generate a realistic karstic network that reproduces observed hydrologic behavior in terms of current spring flow rates, regional hydraulic head field as well as average groundwater residence times. Our model provides a useful tool to generate ensembles of possible karstic conduit networks that may be used within a stochastic framework to analyze flow and transport prediction uncertainty associated with a lack of knowledge about network geometry.
      PubDate: 2017-07-24T07:55:24.605446-05:
      DOI: 10.1002/2017WR020768
       
  • Temporal Information Partitioning Networks (TIPNets): A process network
           approach to infer ecohydrologic shifts
    • Authors: Allison E. Goodwell; Praveen Kumar
      Abstract: In an ecohydrologic system, components of atmospheric, vegetation, and root-soil subsystems participate in forcing and feedback interactions at varying time scales and intensities. The structure of this network of complex interactions varies in terms of connectivity, strength, and time scale due to perturbations or changing conditions such as rainfall, drought, or land use. However, characterization of these interactions is difficult due to multivariate and weak dependencies in the presence of noise, nonlinearities, and limited data. We introduce a framework for Temporal Information Partitioning Networks (TIPNets), in which time-series variables are viewed as nodes, and lagged multivariate mutual information measures are links. These links are partitioned into synergistic, unique, and redundant information components, where synergy is information provided only jointly, unique information is only provided by a single source, and redundancy is overlapping information. We construct TIPNets from 1 min weather station data over several hour time windows. From a comparison of dry, wet, and rainy conditions, we find that information strengths increase when solar radiation and surface moisture are present, and surface moisture and wind variability are redundant and synergistic influences, respectively. Over a growing season, network trends reveal patterns that vary with vegetation and rainfall patterns. The framework presented here enables us to interpret process connectivity in a multivariate context, which can lead to better inference of behavioral shifts due to perturbations in ecohydrologic systems. This work contributes to more holistic characterizations of system behavior, and can benefit a wide variety of studies of complex systems.
      PubDate: 2017-07-24T06:36:32.404439-05:
      DOI: 10.1002/2016WR020218
       
  • Comment on “Rescaling the complementary relationship for land surface
           evaporation” by R. Crago et al.
    • Authors: Ning Ma; Yinsheng Zhang
      Abstract: The generalized complementary relationship (GCR) model of Brutsaert (2015) has been widely applied to estimate land surface evapotranspiration (E) over Chinese eastern monsoon region, Loess Plateau and Australia. However, Crago et al. (2016, hereinafter C16) recently noted a deficiency in one of his boundary conditions and proposed a novel approach to improve it. The key of this approach is to determine the ratio (xmin) of the potential evapotranspiration (Epo) to the apparent potential evapotranspiration for an entirely dry surface (Epads) at which E tends to be vanishing. As seen, the physically reasonable range of xmin should be between 0 and 1. The present comment reports that the xmin in C16 may become invalid under conditions of relatively strong available energy but weak winds if Epads is calculated by the mass-transfer-based method, thereby causing unrealistic estimation of E. A more preferable way to determine Epads is still based on the traditional Penman-based equation with consideration of the characteristics of dry air in which Epads occurs.
      PubDate: 2017-07-22T01:35:46.806558-05:
      DOI: 10.1002/2017WR020892
       
  • Reply to comment by Ma and Zhang on “Rescaling the complementary
           relationship for land surface evaporation”
    • Authors: Richard Crago; Russell Qualls, Jozsef Szilagyi, Justin Huntington
      Abstract: Ma and Zhang (2017) note a concern they have with our rescaled Complementary Relationship (CR) for land surface evaporation when daily average wind speeds are very low (perhaps less than 1 m/s). We discuss conditions and specific formulations that lead to this concern, but ultimately argue that under these conditions, a key assumption behind the CR itself may not be satisfied at the daily time scale. Thus, careful consideration of the reliability of the CR is needed when wind speeds are very low.
      PubDate: 2017-07-22T01:35:21.59794-05:0
      DOI: 10.1002/2017WR021021
       
  • Rival framings: A framework for discovering how problem formulation
           uncertainties shape risk management tradeoffs in water resources systems
    • Authors: J. D. Quinn; P. M. Reed, M. Giuliani, A. Castelletti
      Abstract: Managing water resources systems requires coordinated operation of system infrastructure to mitigate the impacts of hydrologic extremes while balancing conflicting multi-sectoral demands. Traditionally, recommended management strategies are derived by optimizing system operations under a single problem framing that is assumed to accurately represent the system objectives, tacitly ignoring the myriad of effects that could arise from simplifications and mathematical assumptions made when formulating the problem. This study illustrates the benefits of a rival framings framework in which analysts instead interrogate multiple competing hypotheses of how complex water management problems should be formulated. Analyzing rival framings helps discover unintended consequences resulting from inherent biases of alternative problem formulations. We illustrate this on the monsoonal Red River basin in Vietnam by optimizing operations of the system's four largest reservoirs under several different multi-objective problem framings. In each rival framing, we specify different quantitative representations of the system's objectives related to hydropower production, agricultural water supply and flood protection of the capital city of Hanoi. We find that some formulations result in counterintuitive behavior. In particular, policies designed to minimize expected flood damages inadvertently increase the risk of catastrophic flood events in favor of hydropower production, while min-max objectives commonly used in robust optimization provide poor representations of system tradeoffs due to their instability. This study highlights the importance of carefully formulating and evaluating alternative mathematical abstractions of stakeholder objectives describing the multi-sectoral water demands and risks associated with hydrologic extremes.
      PubDate: 2017-07-21T08:55:53.138588-05:
      DOI: 10.1002/2017WR020524
       
  • Modeling invasive alien plant species in river systems: Interaction with
           native ecosystem engineers and effects on hydro-morphodynamic processes
    • Authors: M. van Oorschot; M.G. Kleinhans, G.W. Geerling, G. Egger, R.S.E.W. Leuven, H. Middelkoop
      Abstract: Invasive alien plant species negatively impact native plant communities by out-competing species or changing abiotic and biotic conditions in their introduced range. River systems are especially vulnerable to biological invasions, because waterways can function as invasion corridors. Understanding interactions of invasive and native species and their combined effects on river dynamics is essential for developing cost-effective management strategies. However, numerical models for simulating long-term effects of these processes are lacking. This paper investigates how an invasive alien plant species affects native riparian vegetation and hydro-morphodynamics. A morphodynamic model has been coupled to a dynamic vegetation model that predicts establishment, growth and mortality of riparian trees. We introduced an invasive alien species with life-history traits based on Japanese Knotweed (Fallopia japonica), and investigated effects of low- and high propagule pressure on invasion speed, native vegetation and hydro-morphodynamic processes. Results show that high propagule pressure leads to a decline in native species cover due to competition and the creation of unfavorable native colonization sites. With low propagule pressure the invader facilitates native seedling survival by creating favorable hydro-morphodynamic conditions at colonization sites. With high invader abundance, water levels are raised and sediment transport is reduced during the growing season. In winter, when the above-ground invader biomass is gone, results are reversed and the floodplain is more prone to erosion. Invasion effects thus depend on seasonal above- and below ground dynamic vegetation properties and persistence of the invader, on the characteristics of native species it replaces, and the combined interactions with hydro-morphodynamics.
      PubDate: 2017-07-20T08:38:42.971683-05:
      DOI: 10.1002/2017WR020854
       
  • Toward best practice framing of uncertainty in scientific publications: A
           review of Water Resources Research abstracts
    • Authors: Joseph H.A. Guillaume; Casey Helgeson, Sondoss Elsawah, Anthony J. Jakeman, Matti Kummu
      Abstract: Uncertainty is recognized as a key issue in water resources research, amongst other sciences. Discussions of uncertainty typically focus on tools and techniques applied within an analysis, e.g. uncertainty quantification and model validation. But uncertainty is also addressed outside the analysis, in writing scientific publications. The language that authors use conveys their perspective of the role of uncertainty when interpreting a claim —what we call here “framing” the uncertainty. This article promotes awareness of uncertainty framing in four ways. 1) It proposes a typology of eighteen uncertainty frames, addressing five questions about uncertainty. 2) It describes the context in which uncertainty framing occurs. This is an interdisciplinary topic, involving philosophy of science, science studies, linguistics, rhetoric, and argumentation. 3) We analyze the use of uncertainty frames in a sample of 177 abstracts from the Water Resources Research journal in 2015. This helped develop and tentatively verify the typology, and provides a snapshot of current practice. 4) Provocative recommendations promote adjustments for a more influential, dynamic science. Current practice in uncertainty framing might be described as carefully-considered incremental science. In addition to uncertainty quantification and degree of belief (present in ∼5% of abstracts), uncertainty is addressed by a combination of limiting scope, deferring to further work (∼25%) and indicating evidence is sufficient (∼40%) – or uncertainty is completely ignored (∼8%). There is a need for public debate within our discipline to decide in what context different uncertainty frames are appropriate. Uncertainty framing cannot remain a hidden practice evaluated only by lone reviewers.
      PubDate: 2017-07-20T08:36:19.431148-05:
      DOI: 10.1002/2017WR020609
       
  • Process-based interpretation of conceptual hydrological model performance
           using a multinational catchment set
    • Authors: C. Poncelet; R. Merz, B. Merz, J. Parajka, L. Oudin, V. Andréassian, C. Perrin
      Abstract: Most of previous assessments of hydrologic model performance are fragmented, based on small number of catchments, different methods or time periods and do not link the results to landscape or climate characteristics. This study uses a large-sample hydrology to identify major catchment controls on daily runoff simulations. It is based on a conceptual lumped hydrological model (GR6J), a collection of 29 catchment characteristics, a multinational set of 1103 catchments located in Austria, France and Germany and four runoff model efficiency criteria. Two analyses are conducted to assess how features and criteria are linked: (i) a one-dimensional analysis based on the Kruskal-Wallis test and (ii) a multidimensional analysis based on regression trees and investigating the interplay between features. The catchment features most affecting model performance are the flashiness of precipitation and streamflow (computed as the ratio of absolute day-to-day fluctuations by the total amount in a year), the seasonality of evaporation, the catchment area and the catchment aridity. Nonflashy, nonseasonal, large and nonarid catchments show the best performance for all the tested criteria. We argue that this higher performance is due to fewer nonlinear responses (higher correlation between precipitation and streamflow) and lower input and output variability for such catchments. Finally we show that, compared to national sets, multinational sets increase results transferability because they explore a wider range of hydro-climatic conditions.
      PubDate: 2017-07-20T08:36:16.548456-05:
      DOI: 10.1002/2016WR019991
       
  • Bringing the “social” into socio-hydrology: Conservation policy
           support in the Central Great Plains of Kansas, USA
    • Authors: Matthew R. Sanderson; Jason S. Bergtold, Jessica L. Heier Stamm, Marcellus M. Caldas, Steven M. Ramsey
      Abstract: Identifying means of empirically modeling the human component of a coupled, human-water system becomes critically important to further advances in socio-hydrology. We develop a social-psychological model of environmental decision-making that addresses four key challenges of incorporating social science into integrated models. We use the model to explain preferences for three conservation policies designed to conserve and protect water resources and aquatic ecosystems in the Smoky Hill River Basin, a semi-arid agricultural region in the Central U.S. Great Plains. Further, we compare the model's capacity to explain policy preferences among members of two groups in the River Basin: agricultural producers and members of non-farming communities. We find that financial obligation is the strongest and most consistent explanation of support for conservation policies among members of both groups. We also find that policy support is grounded in cultural values- deeply-held ideas about right and wrong. Environmental values are particularly important explanations of policy support. The constellations of values invoked to make decisions about policies, and the social-psychological pathways linking values to policy support, can vary across policies and types of agents (farmers and non-farmers). We discuss the implications of the results for future research in socio-hydrology.
      PubDate: 2017-07-20T08:35:57.11945-05:0
      DOI: 10.1002/2017WR020659
       
  • Managed aquifer recharge through off-season irrigation in agricultural
           regions
    • Authors: Richard G. Niswonger; Eric D. Morway, Enrique Triana, Justin L. Huntington
      Abstract: Options for increasing reservoir storage in developed regions are limited and prohibitively expensive. Projected increases in demand call for new long-term water storage to help sustain agriculture, municipalities, industry, and ecological services. Managed aquifer recharge (MAR) is becoming an integral component of water resources around the world. However, MAR faces challenges, including infrastructure costs, difficulty in enhancing recharge, water quality issues, and lack of available water supplies. Here we examine, through simulation modeling of a hypothetical agricultural subbasin in the western US, the potential of agricultural managed aquifer recharge (Ag-MAR) via canal seepage and off-season field irrigation. Weather phenomenon in many regions around the world exhibit decadal and other multi-year cycles of extreme precipitation. An on-going challenge is to develop approaches to store greater amounts of water during these events. Simulations presented herein incorporate Ag-MAR programs and demonstrate that there is potential to enhance regional recharge by 7-13%, increase crop consumptive use by 9-12%, and increase natural vegetation consumption by 20-30%, where larger relative increases occur for lower aquifer hydraulic conductivity and higher specific yield values. Annual Increases in groundwater levels were 7 m, and sustained levels following several years of drought were greater than 2 m. Results demonstrate that Ag-MAR has great potential to enhance long-term sustainability of water resources in agricultural basins.
      PubDate: 2017-07-20T08:35:52.415366-05:
      DOI: 10.1002/2017WR020458
       
  • Design of optimal groundwater monitoring well network using stochastic
           modelling and reduced rank spatial prediction
    • Authors: J Sreekanth; Henry Lau, Dan Pagendam
      Abstract: A method for the stochastic design of groundwater quality observation well network is presented. The method uses calibration constrained Null-space Monte Carlo analysis for the stochastic simulation of the reduction ratio of peak concentration and the time corresponding to this in an injection well field. The numerical groundwater model simulations are constrained with a limited amount of field measurements. The objective of the monitoring network design is to identify optimal monitoring locations that allow for prediction of spatial fields from the data collected at limited number of points in the spatial domain. These locations need to be robust to different possible outcomes simulated using the stochastic model runs, and result in good spatial predictions, regardless of which one of the many possibilities turned out to be the true representation of nature. Multiple simulated fields of concentration and time are used to identify a small set of empirical orthogonal functions (spatial basis functions) for reduced-rank prediction of the spatial patterns in these two fields. The Differential Evolution algorithm was used to find the monitoring locations that allowed for optimal reconstruction of all the simulated fields (potential future states of reality) from the set of empirical orthogonal functions. The applicability is demonstrated for designing a monitoring network for an injection well field. Optimal locations of 10 monitoring wells were identified. The method has the capability to simultaneously identify the optimal locations and inform optimal times for monitoring reduction ratio of peak concentration. The method is flexible to iteratively combine stochastic modelling and monitoring for optimal groundwater management
      PubDate: 2017-07-20T08:35:36.439384-05:
      DOI: 10.1002/2017WR020385
       
  • Hydrologic Impacts of changes in climate and glacier extent in the Gulf of
           Alaska watershed
    • Authors: J.P. Beamer; D.F. Hill, D. McGrath, A. Arendt, C. Kienholz
      Abstract: High-resolution regional-scale hydrologic models were used to quantify the response of late 21st century runoff from the Gulf of Alaska (GOA) watershed to changes in regional climate and glacier extent. NCEP Climate Forecast System Reanalysis data were combined with five Coupled Model Intercomparison Project Phase 5 General Circulation Models (GCM) for two representative concentration pathway (RCP) scenarios (4.5 and 8.5) to develop meteorological forcing for the period 2070–2099. A hypsographic model was used to estimate future glacier extent given assumed equilibrium line altitude (ELA) increases of 200 and 400 m. GCM predictions show an increase in annual precipitation of 12% for RCP 4.5 and 21% for RCP 8.5, and an increase in annual temperature of 2.5°C for RCP 4.5 and 4.3°C for RCP 8.5, averaged across the GOA. Scenarios with perturbed climate and glaciers predict annual GOA-wide runoff to increase by 9% for RCP4.5/ELA200 case and 14% for the RCP8.5/ELA400 case. The glacier runoff decreased by 14% for RCP4.5/ELA200 and by 34% for the RCP8.5/ELA400 case. Inter-model variability in annual runoff was found to be approximately twice the variability in precipitation input. Additionally, there are significant changes in runoff partitioning and increases in snowpack runoff are dominated by increases in rain-on-snow events. We present results aggregated across the entire GOA and also for individual watersheds to illustrate the range in hydrologic regime changes, and explore the sensitivities of these results by independently perturbing only climate forcings and only glacier cover.
      PubDate: 2017-07-20T08:35:33.013802-05:
      DOI: 10.1002/2016WR020033
       
  • Remote determination of the velocity index and mean streamwise velocity
           profiles
    • Authors: E. D. Johnson; E. A. Cowen
      Abstract: When determining volumetric discharge from surface measurements of currents in a river or open channel, the velocity index is typically used to convert surface velocities to depth-averaged velocities. The velocity index is given by, k = Ub/Usurf, where Ub is the depth-averaged velocity and Usurf is the local surface velocity. The USGS (United States Geological Survey) standard value for this coefficient, k = 0.85, was determined from a series of laboratory experiments and has been widely used in the field and in laboratory measurements of volumetric discharge despite evidence that the velocity index is site-specific. Numerous studies have documented that the velocity index varies with Reynolds number, flow depth, relative bed roughness and with the presence of secondary flows. A remote method of determining depth-averaged velocity and hence the velocity index is developed here. The technique leverages the findings of Johnson and Cowen [2017] and permits remote determination of the velocity power law exponent thereby, enabling remote prediction of the vertical structure of the mean streamwise velocity, the depth-averaged velocity and the velocity index.
      PubDate: 2017-07-20T08:35:29.211547-05:
      DOI: 10.1002/2017WR020504
       
  • Stochastic analysis of unsaturated steady flows above the water-table
    • Authors: Gerardo Severino; Maddalena Scarfato, Alessandro Comegna
      Abstract: Steady flowtakes place into a three-dimensional partially saturated porous medium where, due to their spatial variability, the saturated conductivity Ks and the relative conductivity Kr are modeled as random space functions (RSF)s. As a consequence, the flow variables (FVS), i.e. pressure-head and specific flux, are also RSFs. The focus of the present paper consists into quantifying the uncertainty of the FVS above the water-table. The simple expressions (most of which in closed form) of the second-order moments pertaining to the FVS allow one to follow the transitional behavior from the zone close to the water-table (where the FVS are non-stationary), till to their far-field limit (where the FVS become stationary RSFs). In particular, it is shown how the stationary limits (and the distance from the water-table at which stationarity is attained) depend upon the statistical structure of the RSFs Ks, Kr and the infiltrating rate. The mean pressure head kψl has been also computed, and it is expressed as kψl = ψ0(1+ψ), being ψ a characteristic heterogeneity function which modifies the zero-order approximation ψ0 of the pressure head (valid for a vadose zone of uniform soil properties) to account for the spatial variability of Ks and Kr. Two asymptotic limits, i.e. close (near field) and away (far field) from the water-table, are derived into a very general manner, whereas the transitional behavior of ψ between the near/far field can be determined after specifying the shape of the various input soil properties. Besides the theoretical interest, results of the present paper are useful for practical purposes, as well. Indeed, the model is tested against to real data, and in particular it is shown how it is possible for the specific case study to grasp the behavior of the FVS within an environment (i.e. the vadose zone close to the water-table) which is generally very difficult to access by direct inspection.
      PubDate: 2017-07-19T00:30:50.447498-05:
      DOI: 10.1002/2017WR020554
       
  • Insights into mountain precipitation and snowpack from a basin-scale
           wireless-sensor network
    • Authors: Z. Zhang; S. Glaser, R. Bales, M. Conklin, R. Rice, D. Marks
      Abstract: A spatially distributed wireless-sensor network, installed across the 2154 km2 portion of the 5311 km2 American River basin above 1500 m elevation, provided spatial measurements of temperature, relative humidity and snow depth in the Sierra Nevada, California. The network consisted of 10 sensor clusters, each with 10 measurement nodes, distributed to capture the variability in topography and vegetation cover. The sensor network captured significant spatial heterogeneity in rain versus snow precipitation for water year 2014, variability that was not apparent in the more-limited operational data. Using daily dew-point temperature to track temporal elevational changes in the rain-snow transition, the amount of snow accumulation at each node was used to estimate the fraction of rain versus snow. This resulted in an underestimate of total precipitation below the 0°C dew-point elevation, which averaged 1730 m across 10 precipitation events, indicating that measuring snow does not capture total precipitation. We suggest blending lower-elevation rain-gauge data with higher-elevation sensor-node data for each event to estimate total precipitation. Blended estimates were on average 15-30% higher than using either set of measurements alone. Using data from the current operational snow-pillow sites gives even lower estimates of basin-wide precipitation. Given the increasing importance of liquid precipitation in a warming climate, a strategy that blends distributed measurements of both liquid and solid precipitation will provide more accurate basin-wide precipitation estimates, plus spatial and temporal patters of snow accumulation and melt in a basin.
      PubDate: 2017-07-18T13:50:58.301675-05:
      DOI: 10.1002/2016WR018825
       
  • Dynamics of nitrate concentration-discharge patterns in an urban watershed
    • Authors: Jonathan M. Duncan; Claire Welty, John T. Kemper, Peter M. Groffman, Lawrence E. Band
      Abstract: Concentration-discharge (c-Q) relations have been used to infer watershed-scale processes governing solute fluxes. Prior studies have documented inconsistent concentration-discharge patterns at the storm event scale driven by changes in end-member concentrations. Other studies have evaluated c-Q data from all periods in a composite fashion to quantify chemostasis (relatively invariant changes in concentration over several orders of magnitude variation in streamflow). Here we examine three-years of high-frequency nitrate and discharge data (49,861 data points) to complement 14 years of weekly data (699 data points) for an urban stream in Baltimore, MD USA to quantify c-Q relationships. We show that these relationships are variable through time and depend on the temporal scale at which they are investigated. On a storm-event scale, the sensor data exhibit a watershed-specific dQ/Q threshold when storms switch from counter-clockwise to clockwise c-Q behavior. On a seasonal scale, we show the influence of hydrologic variability and in-stream metabolism as controls on stream nitrate concentrations and fluxes. On a composite scale, we evaluate the c-Q data for chemostasis using analysis of both c-Q slopes and CVc/CVQ, as a function of time. The slopes of c-Q data for both long-term weekly and high frequency data sets are in close agreement on an annual basis and vary between dry and wet years; the CVc/CVQ analysis is less sensitive to hydroclimate variability. This work highlights the value of both long-term and high-frequency c-Q data collection for calculating and analyzing solute fluxes.
      PubDate: 2017-07-18T13:50:42.663974-05:
      DOI: 10.1002/2017WR020500
       
  • Mapping the temporary and perennial character of whole river networks
    • Authors: A. M. González-Ferreras; J. Barquín
      Abstract: Knowledge of the spatial distribution of temporary and perennial river channels in a whole catchment is important for effective integrated basin management and river biodiversity conservation. However, this information is usually not available or is incomplete. In this study, we present a statistically-based methodology to classify river segments from a whole river network (Deva-Cares catchment, Northern Spain) as temporary or perennial. This method is based on an a priori classification of a subset of river segments as temporary or perennial, using field surveys and aerial images, and then running Random Forest models to predict classification membership for the rest of the river network. The independent variables and the river network were derived following a computer-based geospatial simulation of riverine landscapes. The model results show high values of overall accuracy, sensitivity and specificity for the evaluation of the fitted model to the training and testing dataset (≥0.9). The most important independent variables were catchment area, area occupied by broadleaf forest, minimum monthly precipitation in August, and average catchment elevation. The final map shows 7525 temporary river segments (1012.5 km) and 3731 perennial river segments (662.5 km). A subsequent validation of the mapping results using River Habitat Survey data and expert knowledge supported the validity of the proposed maps. We conclude that the proposed methodology is a valid method for mapping the limits of flow permanence that could substantially increase our understanding of the spatial links between terrestrial and aquatic interfaces, improving the research, management, and conservation of river biodiversity and functioning.
      PubDate: 2017-07-18T13:50:25.823865-05:
      DOI: 10.1002/2017WR020390
       
  • The impact of water quality in Narragansett Bay on housing prices
    • Authors: Tingting Liu; James J. Opaluch, Emi Uchida
      Abstract: We examine the impact of water quality in Narragansett Bay on housing prices in coastal towns and municipalities using a hedonic housing-price model. Unlike other hedonic studies of water quality, we test whether housing market responds to average water quality or more to extreme events. We also test the spatial and temporal extent of effects of water quality on housing prices. We find that poor coastal water quality, measured in terms of the concentration of chlorophyll, has a negative impact on housing prices that diminishes with distance from the shoreline. Furthermore, our finding suggests that housing prices are most influenced by the extreme environmental conditions, which may be accompanied by unpleasant odors, discoloration and even fish kills. We further predict potential increases in home values associated under water quality improvement scenarios and find an increase in the values of homes in coastal communities along Narragansett Bay of about $18 million up to $136 million.
      PubDate: 2017-07-17T02:40:55.898536-05:
      DOI: 10.1002/2016WR019606
       
  • Covariation in patterns of turbulence-driven hyporheic flow and
           denitrification enhances reach-scale nitrogen removal
    • Authors: Angang Li; Antoine F. Aubeneau, Diogo Bolster, Jennifer L. Tank, Aaron I. Packman
      Abstract: Co-injections of conservative tracers and nutrients are commonly used to assess travel time distributions and nutrient removal in streams. However, in-stream tracer data often lack information on long-term hyporheic storage, and removal rate coefficients are often assumed to be uniform despite plentiful evidence that microbially-mediated transformations, such as denitrification, exhibit strong spatial variability in the hyporheic zone. We used process-based particle tracking simulations to explore the coupled effects of spatial patterns in hyporheic flow and denitrification on reach-scale nitrogen removal. We simulated whole-stream nitrogen dynamics with exponential, layered, and uniform profiles of hyporheic denitrification. We also simulated nitrogen dynamics in Little Rabbit Creek, an agricultural headwater stream in the Kalamazoo River Basin (Michigan, U.S.) where vertical profiles of hyporheic denitrification were measured in situ. Covariation between porewater velocity and mixing causes rapid exchange in the near-surface bioactive region and substantially prolonged exchange in the deeper hyporheic. Patterns of hyporheic denitrification covary with patterns of hyporheic flow. This covariation directly controls tailing of in-stream breakthrough curves and hence reach-scale nutrient removal. Enhanced denitrification near the sediment-water interface strongly tempers breakthrough curve tails at timescales associated with flushing of the near-surface region, while more spatially uniform denitrification causes weaker tempering over a wider range of hyporheic exchange timescales. At the reach scale, overall nitrogen removal increases with heterogeneity of hyporheic denitrification, indicating that covariation between flow and denitrification – particularly the rapid flushing of highly bioactive regions near the sediment-water interface – controls whole-stream transformation rates.
      PubDate: 2017-07-15T03:30:53.654769-05:
      DOI: 10.1002/2016WR019949
       
  • Predictive performance of rainfall thresholds for shallow landslides in
           Switzerland from gridded daily data
    • Authors: Elena Leonarduzzi; Peter Molnar, Brian W. McArdell
      Abstract: A high-resolution gridded daily precipitation dataset was combined with a landslide inventory containing over 2000 events in the period 1972–2012 to analyze rainfall thresholds which lead to landsliding in Switzerland. We co-located triggering rainfall to landslides, developed distributions of triggering and non-triggering rainfall event properties, and determined rainfall thresholds and intensity-duration ID curves and validated their performance. The best predictive performance was obtained by the intensity-duration ID threshold curve, followed by peak daily intensity Imax and mean event intensity Imean. Event duration by itself had very low predictive power. A single country-wide threshold of Imax = 28 mm/day was extended into space by regionalization based on surface erodibility and local climate (mean daily precipitation). It was found that wetter local climate and lower erodibility led to significantly higher rainfall thresholds required to trigger landslides. However, we showed that the improvement in model performance due to regionalization was marginal and much lower than what can be achieved by having a high quality landslide database. Reference cases in which the landslide locations and timing were randomized and the landslide sample size was reduced showed the sensitivity of the Imax rainfall threshold model. Jack-knife and cross-validation experiments demonstrated that the model was robust. The results reported here highlight the potential of using rainfall I-D threshold curves and Imax threshold values for predicting the occurrence of landslides on a country or regional scale with possible applications in landslide warning systems, even with daily data.
      PubDate: 2017-07-15T03:10:37.818927-05:
      DOI: 10.1002/2017WR021044
       
  • Regional sensitivities of seasonal snowpack to elevation, aspect, and
           vegetation cover in western North America
    • Authors: Christopher J. Tennant; Adrian A. Harpold, Kathleen Ann Lohse, Sarah E. Godsey, Benjamin T. Crosby, Laurel G. Larsen, Paul D. Brooks, Robert W. Van Kirk, Nancy F. Glenn
      Abstract: In mountains with seasonal snow-cover, the effects of climate change on snowpack will be constrained by landscape-vegetation interactions with the atmosphere. Airborne lidar surveys used to estimate snow depth, topography, and vegetation were coupled with reanalysis climate products to quantify these interactions and to highlight potential snowpack sensitivities to climate and vegetation change across the western U.S. at Rocky Mountain (RM), Northern Basin and Range (NBR), and Sierra Nevada (SNV) sites. In forest and shrub areas, elevation captured the greatest amount of variability in snow depth (16-79%) but aspect explained more variability (11-40%) in alpine areas. Aspect was most important at RM sites where incoming shortwave to incoming net radiation (SW:NetR) was highest (∼0.5), capturing 17-37% of snow depth variability in forests and 32-37% in shrub areas. Forest vegetation height exhibited negative relationships with snow depth and explained 3-6% of its variability at sites with greater longwave inputs (NBR and SNV). Variability in the importance of physiography suggest differential sensitivities of snowpack to climate and vegetation change. The high SW:NetR and importance of aspect suggests RM sites may be more responsive to decreases in SW:NetR driven by warming or increases in humidity or cloud-cover. Reduced canopy-cover could increase snow depths at SNV sites, and NBR and SNV sites are currently more sensitive to shifts from snow to rain. The consistent importance of aspect and elevation suggest that changes in SW:NetR and the elevation of the rain/snow transition zone could have widespread and varied effects on western U.S. snowpacks.
      PubDate: 2017-07-15T03:10:27.056293-05:
      DOI: 10.1002/2016WR019374
       
  • Non-stationarity in Threshold Response of Stormflow in Southern
           Appalachian Headwater Catchments
    • Authors: Charles I. Scaife; Lawrence E. Band
      Abstract: Threshold behavior of stormflow response is an emergent pattern observed in several studies demonstrating subsurface storage controls on catchment rainfall-runoff dynamics. These studies demonstrate a distinct transition from negligible stormflow discharge response to rapid, linearly increasing stormflow identified by a single, uniquely-defined threshold as a basic catchment attribute that relates to geophysical properties. Utilizing precipitation, streamflow, and soil moisture data spanning 15 years from three catchments at the Coweeta Hydrologic Laboratory (CHL), we analyze how threshold behavior forms and varies at several timescales. We pose three hypotheses: (1) stormflow thresholds form at CHL as a function of antecedent soil moisture and gross precipitation, (2) thresholds vary seasonally and interannually, and (3) threshold variation through time implies greater long-term complexity of runoff controls beyond catchment geophysical properties, including forest canopy ecohydrologic feedbacks. We isolate threshold behavior of stormflow using piecewise regression analysis in short to long-term datasets with respect to antecedent soil moisture index and gross precipitation. We use this to investigate threshold variation over seasonal, interannual, and decadal timescales that encompass hydroclimatic extremes. Seasonal analysis reveals that thresholds are more variable between growing seasons than between dormant seasons. In growing seasons with greater water stress, stormflow thresholds are lower after controlling for soil moisture storage suggesting more complex, long-term rainfall-runoff relationships as a result of forest canopy response to water stress. We present a conceptual model of how vegetation-climate interactions influence long-term rainfall-runoff relationships creating interannual variability of stormflow thresholds and linear stormflow response.
      PubDate: 2017-07-15T03:10:23.360036-05:
      DOI: 10.1002/2017WR020376
       
  • Celebrating hydrologic science: The “Science is Essential”
           collection
    • Authors: Martyn P. Clark; Charles H. Luce, H. J. (Ilja) van Meerveld
      Abstract: Water Resources Research published nine commentaries in the AGU “Science is Essential” collection. The goal of these papers is to celebrate the advances in hydrologic science, to show how hydrologic science is essential for society, and to illustrate how hydrologic science has influenced policies. Here we provide a brief introduction to these papers, to encourage you to explore them in full.
      PubDate: 2017-07-13T08:15:23.1115-05:00
      DOI: 10.1002/2017WR021178
       
  • Hyporheic hot moments: Dissolved oxygen dynamics in the hyporheic zone in
           response to surface flow perturbations
    • Authors: Matthew H. Kaufman; M. Bayani Cardenas, Jim Buttles, Adam J. Kessler, Perran L. M. Cook
      Abstract: Dissolved oxygen (DO) is a key environmental variable that drives and feeds back with numerous processes. In the aquatic sediment that make up the hyporheic zone, DO may exhibit pronounced spatial gradients and complex patterns which control the distribution of a series of redox processes. Yet, little is known regarding the dynamics of hyporheic zone DO, especially under transitional flow regimes. Considering the natural tendency of rivers to be highly responsive to external forcing, these temporal dynamics are potentially just as important and pronounced as the spatial gradients. Here we use laboratory flume experiments and multiphysics flow and reactive transport modeling to investigate surface flow controls on the depth of oxygen penetration in the bed as well as the area of oxygenated sediment. We show that the hyporheic zone DO conditions respond over timescales of hours-to-days when subjected to practically instantaneous surface flow perturbations. Additionally, the flume experiments demonstrate that hyporheic zone DO conditions respond faster to surface flow acceleration than to deceleration. Finally, we found that the morphology of the dissolved oxygen plume front depends on surface flow acceleration or deceleration. This study thus shows that the highly dynamic nature of typical streams and rivers drives equally dynamic redox conditions in the hyporheic zone. Because the redox conditions and their distribution within the hyporheic zone are important from biological, ecological, and contaminant perspectives, this hyporheic redox dynamism has the potential to impact system scale aquatic chemical cycles.
      PubDate: 2017-07-13T08:11:46.186397-05:
      DOI: 10.1002/2016WR020296
       
  • An evaluation of terrain-based downscaling of fractional snow covered area
           datasets based on Lidar-derived snow data and orthoimagery
    • Authors: Nicoleta C. Cristea; Ian Breckheimer, Mark S. Raleigh, Janneke HilleRisLambers, Jessica D. Lundquist
      Abstract: Reliable maps of snow-covered areas at scales of meters to tens of meters, with daily temporal resolution, are essential to understanding snow heterogeneity, melt runoff, energy exchange, and ecological processes. Here we develop a parsimonious downscaling routine that can be applied to fractional snow covered area (fSCA) products from satellite platforms such as the Moderate Resolution Imaging Spectroradiometer (MODIS) that provide daily ∼500 m data, to derive higher resolution snow presence/absence grids. The method uses a composite index combining both the topographic position index (TPI) to represent accumulation effects and the diurnal anisotropic heat (DAH, sun exposure) index to represent ablation effects. The procedure is evaluated and calibrated using airborne-derived high-resolution datasets across the Tuolumne watershed, CA using 11 scenes in 2014 to downscale to 30-m resolution. The average matching F score was 0.83. We then tested our method's transferability in time and space by comparing against the Tuolumne watershed in water years 2013 and 2015, and over an entirely different site, Mt. Rainier, WA in 2009 and 2011, to assess applicability to other topographic and climatic conditions. For application to sites without validation data, we recommend equal weights for the TPI and DAH indices and close TPI neighborhoods (60 m and 27 m for downscaling to 30 m and 3 m, respectively), which worked well in both our study areas. The method is less effective in forested areas, which still requires site-specific treatment. We demonstrate that the procedure can even be applied to downscale to 3 m resolution, a very fine scale relevant to alpine ecohydrology research.
      PubDate: 2017-07-13T08:09:48.127485-05:
      DOI: 10.1002/2017WR020799
       
  • Quantitative mapping of solute accumulation in a soil-root system by
           Magnetic Resonance imaging
    • Authors: S. Haber-Pohlmeier; J. Vanderborght, A. Pohlmeier
      Abstract: Differential uptake of water and solutes by plant roots generates heterogeneous concentration distributions in soils. Non-invasive observations of root system architecture and concentration patterns therefore provide information about root water and solute uptake. We present the application of magnetic resonance imaging (MRI) to image and monitor root architecture and the distribution of a tracer, GdDTPA2-(Gadolinium-diethylenetriaminepentacetate) non-invasively during an infiltration experiment in a soil column planted with white lupin. We show that inversion recovery preparation within the MRI imaging sequence can quantitatively map concentrations of a tracer in a complex root-soil system. Instead of a simple T1 weighting, the procedure is extended by a wide range of inversion times to precisely map T1 and subsequently to cover a much broader concentration range of the solute. The derived concentrations patterns were consistent with mass balances and showed that the GdDTPA2- tracer represents a solute that is excluded by roots. Monitoring and imaging the accumulation of the tracer in the root zone therefore offers the potential to determine where and by which roots water is taken up.
      PubDate: 2017-07-13T08:09:45.129805-05:
      DOI: 10.1002/2017WR020832
       
  • Simulating the long-term impacts of drainage and restoration on the
           ecohydrology of peatlands
    • Authors: Dylan M. Young; Andy J. Baird, Paul J. Morris, Joseph Holden
      Abstract: Drainage alters the carbon storage and accumulation functions of peatlands, but the long-term effects of drainage ditches, and their restoration, on peatland development are poorly understood. Timescales of monitoring studies in ditch-drained and restored peatlands are typically limited to a few years, and occasionally decades. In addition, experimental studies seldom monitor spatial changes in peat structure caused by ditches, despite such changes affecting water flow and water retention in peat. Ecosystem models offer an alternative to experimental studies and can help explain how complex systems such as peatlands may respond to external disturbances. Here we report on a 2D application of a peatland development model (DigiBog) to explore how contour-parallel ditches, and their damming, affect the ecohydrology of peatlands over decades to centuries, using blanket peatlands as a case study. Drainage resulted in the rapid loss of peat due to increased oxic decay. The majority of these losses occurred in the first 100 years after the ditch was created, but water table dynamics were altered even centuries later. Restoration halted the loss of peat and encouraged net peat accumulation, although the amount lost in 100 years of drainage had not been replaced 200 years after the ditch was dammed. Restoration of ditches in sloping peatlands brought about more peat regrowth downslope of the restored ditch than further upslope. Our study demonstrates the potential for spatially-distributed, ecosystem-scale models as tools to explore complex spatiotemporal responses to disturbance, and to support land managers in making decisions about peatland drainage and restoration.
      PubDate: 2017-07-13T08:08:42.212091-05:
      DOI: 10.1002/2016WR019898
       
  • Monitoring and simulation of salinity changes in response to tide and
           storm surges in a sandy coastal aquifer system
    • Authors: S. Huizer; M.C. Karaoulis, G. H. P. Oude Essink, M. F. P. Bierkens
      Abstract: Tidal dynamics and especially storm surges can have an extensive impact on coastal fresh groundwater resources. Combined with the prospect of sea-level rise and the reliance of many people on these resources, this demonstrates the need to assess the vulnerability of coastal areas to these threats. In this study we investigated the impact of tides and storm surges on coastal groundwater at a pilot location on the Dutch coast (viz. the Sand Engine). To monitor changes in groundwater salinity under a variety of conditions, we performed automated measurements with electrical resistivity tomography for a period of two months between November 2014 and January 2015. The obtained resistivity images were converted to salinity images, and these images served effectively as observations of the impact of tidal fluctuations, saltwater overwash during storm surges, and the recovery of the freshwater lens after land-surface inundations.Most of the observed changes in groundwater head and salinity could be reproduced with a two-dimensional variable-density groundwater flow and salt transport model. This shows that groundwater models can be used to make accurate predictions of the impact of tides and storm surges on fresh groundwater resources, given a thorough understanding of the (local) system. Comparisons of measurements and model simulations also showed that morphological changes and wave run-up can have a strong impact on the extent of land-surface inundations in (low-elevation) dynamic coastal environments, and can therefore substantially affect coastal fresh groundwater resources.
      PubDate: 2017-07-13T08:08:31.713558-05:
      DOI: 10.1002/2016WR020339
       
  • Reducing equifinality using isotopes in a process-based stream nitrogen
           model highlights the flux of algal nitrogen from agricultural streams
    • Authors: William I. Ford; James F. Fox, Erik Pollock
      Abstract: The fate of bioavailable nitrogen species transported through agricultural landscapes remains highly uncertain given complexities of measuring fluxes impacting the fluvial N cycle. We present and test a new numerical model named Technology for Removable Annual Nitrogen in Streams For Ecosystem Restoration, TRANSFER, which aims to reduce model uncertainty due to erroneous parameterization, i.e., equifinality, in stream nitrogen cycle assessment and quantify the significance of transient and permanent removal pathways. TRANSFER couples nitrogen elemental and stable isotope mass balance equations with existing hydrologic, hydraulic, sediment transport, algal biomass, and sediment organic matter mass-balance sub-routines and a robust GLUE-like uncertainty analysis. We test the model in an agriculturally impacted, third-order stream reach located in the Bluegrass Region of Central Kentucky. Results of the multi-objective model evaluation for the model application highlight the ability of sediment nitrogen fingerprints including elemental concentrations and stable N isotope signatures to reduce equifinality of the stream N model. Advancements in the numerical simulations allow for illumination of the significance of algal sloughing fluxes for the first time in relation to denitrification. Broadly, model estimates suggest denitrification is slightly greater than algal N sloughing (10.7% and 6.3% of dissolved N load on average), highlighting the potential for overestimation of denitrification by 37%. We highlight the significance of the transient N pool given the potential for the N store to be regenerated to the water column in downstream reaches, leading to harmful and nuisance algal bloom development.
      PubDate: 2017-07-13T08:07:47.127291-05:
      DOI: 10.1002/2017WR020607
       
  • Estimating rainfall time series and model parameter distributions using
           model data reduction and inversion techniques
    • Authors: Ashley J. Wright; Jeffrey P. Walker, Valentijn R.N. Pauwels
      Abstract: Floods are devastating natural hazards. To provide accurate, precise and timely flood forecasts there is a need to understand the uncertainties associated within an entire rainfall time series, even when rainfall was not observed. The estimation of an entire rainfall time series, and model parameter distributions from streamflow observations in complex dynamic catchments adds skill to current areal rainfall estimation methods, allows for the uncertainty of entire rainfall input time series to be considered when estimating model parameters, and provides the ability to improve rainfall estimates from poorly gauged catchments. Current methods to estimate entire rainfall time series from streamflow records are unable to adequately invert complex non-linear hydrologic systems. This study aims to explore the use of wavelets in the estimation of rainfall time series from streamflow records. Using the Discrete Wavelet Transform (DWT) to reduce rainfall dimensionality for the catchment of Warwick, Queensland, Australia, it is shown that model parameter distributions and an entire rainfall time series can be estimated. Including rainfall in the estimation process improves streamflow simulations by a factor of up to 1.78. This is achieved whilst estimating an entire rainfall time series, inclusive of days when none was observed. It is shown that the choice of wavelet can have a considerable impact on the robustness of the inversion. Combining the use of a likelihood function that considers rainfall and streamflow errors with the use of the DWT as a model data reduction technique allows the joint inference of hydrologic model parameters along with rainfall.
      PubDate: 2017-07-13T08:07:32.847047-05:
      DOI: 10.1002/2017WR020442
       
  • Revealing the economic value of managed aquifer recharge: Evidence from a
           contingent valuation study in Italy
    • Authors: D. Damigos; G. Tentes, M. Balzarini, F. Furlanis, A. Vianello
      Abstract: Managed aquifer recharge (MAR) is a promising water management tool towards restoring groundwater balance and securing groundwater ecosystem services (i.e. water for drinking, industrial or irrigation use, control of land subsidence, maintenance of environmental flows to groundwater dependent ecosystems, etc.). Obviously, MAR projects can improve the quality of lives of the people by several ways. Thus, from a social perspective, the benefits of MAR cannot and should not be based only on market revenues or costs. Although the value of groundwater, from a social perspective, has been a subject of socio-economic research, literature on the value of MAR per se is very limited. This paper, focusing on Italy which is a country with extensive utilisation of MAR, aims to estimate the economic value of MAR and makes a first step towards filling this gap in the literature. For this purpose, the Contingent Valuation method was implemented to provide a monetary estimate and to explore the factors influencing people's attitude and willingness to pay for MAR. The results show that society holds not only use but also significant non-use values, which are a part of the total economic value (TEV) of groundwater according to related research efforts. To this end, MAR valuation highlights its social importance for groundwater conservation and provides a solid basis for incorporating its non-market benefits into groundwater management policies and assessments.
      PubDate: 2017-07-13T08:07:28.714452-05:
      DOI: 10.1002/2016WR020281
       
  • Wettability impact on supercritical CO2 capillary trapping: Pore-scale
           visualization and quantification
    • Authors: Ran Hu; Jiamin Wan, Yongman Kim, Tetsu K. Tokunaga
      Abstract: How the wettability of pore surfaces affects supercritical (sc) CO2 capillary trapping in geologic carbon sequestration (GCS) is not well understood, and available evidence appears inconsistent. Using a high-pressure micromodel-microscopy system with image analysis, we studied the impact of wettability on scCO2 capillary trapping during short-term brine flooding (80 seconds, 8 to 667 pore volumes). Experiments on brine displacing scCO2 were conducted at 8.5 MPa and 45°C in water-wet (static contact angle θ = 20° ± 8°) and intermediate-wet (θ = 94° ± 13°) homogeneous micromodels under four different flow rates (capillary number Ca ranging from 9 × 10−6 to 8 × 10−4) with a total of eight conditions (four replicates for each). Brine invasion processes were recorded and statistical analysis was performed for over two thousand images of scCO2 saturations, and scCO2 cluster characteristics. The trapped scCO2 saturation under intermediate-wet conditions is 15% higher than under water-wet conditions under the slowest flow rate (Ca ∼ 9 × 10−6). Based on the visualization and scCO2 cluster analyses, we show that the scCO2 trapping process in our micromodels is governed by bypass trapping that is enhanced by the larger contact angle. Smaller contact angles enhance cooperative pore filling and widen brine fingers (or channels), leading to smaller volumes of scCO2 being bypassed. Increased flow rates suppress this wettability effect.
      PubDate: 2017-07-13T08:07:26.437877-05:
      DOI: 10.1002/2017WR020721
       
  • Water quality and ecosystem management: Data-driven reality check of
           effects in streams and lakes
    • Authors: Georgia Destouni; Ida Fischer, Carmen Prieto
      Abstract: This study investigates nutrient-related water quality conditions and change trends in the first management periods of the EU Water Framework Directive (WFD; since 2009) and Baltic Sea Action Plan (BASP; since 2007). With mitigation of nutrients in inland waters and their discharges to the Baltic Sea being a common WFD and BSAP target, we use Sweden as a case study of observable effects, by compiling and analyzing all openly available water and nutrient monitoring data across Sweden since 2003. The data compilation reveals that nutrient monitoring covers only around 1% (down to 0.2% for nutrient loads) of the total number of WFD-classified stream and lake water bodies in Sweden. The data analysis further that the hydro-climatically driven water discharge dominates the determination of waterborne loads of both total phosphorus and total nitrogen across Sweden. Both water discharge and the related nutrient loads are in turn well correlated with the ecosystem status classification of Swedish water bodies. Nutrient concentrations do not exhibit such correlation and their changes over the study period are on average small, but concentration increases are found for moderate-to-bad status waters, for which both the WFD and the BSAP have instead targeted concentration decreases. In general, these results indicate insufficient distinction and mitigation of human-driven nutrient components in inland waters and their discharges to the sea by the internationally harmonized applications of the WFD and BSAP. The results also call for further comparative investigations of observable large-scale effects of such regulatory/management frameworks in different parts of the world.
      PubDate: 2017-07-13T08:06:00.65781-05:0
      DOI: 10.1002/2016WR019954
       
  • Environmental drivers of denitrification rates and denitrifying gene
           abundances in channels and riparian areas
    • Authors: A. A. Tomasek; J. Kozarek, M. Hondzo, N. Lurndahl, M. Sadowsky, P. Wang, C. Staley
      Abstract: Intensive agriculture in the Midwestern United States contributes to excess nitrogen in surface water and groundwater, negatively affecting human health and aquatic ecosystems. Complete denitrification removes reactive nitrogen from aquatic environments and releases inert dinitrogen gas. We examined denitrification rates and the abundances of denitrifying genes and total bacteria at three sites in an agricultural watershed and in an experimental stream in Minnesota. Sampling was conducted along transects with a gradient from always inundated (in-channel), to periodically inundated, to non-inundated conditions to determine how denitrification rates and gene abundances varied from channels to riparian areas with different inundation histories. Results indicate a coupling between environmental parameters, gene abundances, and denitrification rates at the in-channel locations, and limited to no coupling at the periodically inundated and non-inundated locations, respectively. Nutrient-amended potential denitrification rates for the in-channel locations were significantly correlated (α = 0.05) with five of six measured denitrifying gene abundances, whereas the periodically inundated and non-inundated locations were each only significantly correlated with the abundance of one denitrifying gene. These results suggest that DNA-based analysis of denitrifying gene abundances alone cannot predict functional responses (denitrification potential), especially in studies with varying hydrologic regimes. A scaling analysis was performed to develop a predictive functional relationship relating environmental parameters to denitrification rates for in-channel locations. This method could be applied to other geographic and climatic regions to predict the occurrence of denitrification hot spots.
      PubDate: 2017-07-13T08:05:56.470192-05:
      DOI: 10.1002/2016WR019566
       
  • Critical zone structure controls concentration-discharge relationships and
           solute generation in forested tropical montane watersheds
    • Authors: Adam S. Wymore; Richard L. Brereton, Daniel E. Ibarra, Kate Maher, William H. McDowell
      Abstract: Concentration-discharge (C-Q) relationships are poorly known for tropical watersheds, even though the tropics contribute a disproportionate amount of solutes to the global ocean. The Luquillo Mountains in Puerto Rico offer an ideal environment to examine C-Q relationships across a heterogeneous tropical landscape. We use 10-30 years of weekly stream chemistry data across ten watersheds to examine C-Q relationships for weathering products (SiO2(aq), Ca2+, Mg2+, Na+) and biologically-controlled solutes (dissolved organic carbon [DOC], dissolved organic nitrogen [DON], NH4+, NO3-, PO43-, K+, SO42-). We analyze C-Q relationships using power-law equations and a solute production model, and use Principal Component Analysis to test hypotheses regarding how the structure of the Critical Zone controls solute generation. Volcaniclastic watersheds had higher concentrations of weathering solutes and smaller tributaries were approximately 3-fold more efficient at generating these solutes than larger rivers. Lithology and vegetation explained a significant amount of variation in the theoretical maximum concentrations of weathering solutes (r2 = 0.43 - 0.48) and in the C-Q relationships of PO43- (r2 = 0.63) and SiO2(aq) (r2 = 0.47). However, the direction and magnitude of these relationships varied. Across watersheds various forms of N and P displayed variable C-Q relationships, while DOC was consistently enriched with increasing discharge. Results suggest that PO43- may be a useful indicator of watershed function. Relationships between C-Q and landscape characteristics indicate the extent to which the structure and function of the critical zone controls watershed solute fluxes.
      PubDate: 2017-07-13T08:05:52.076018-05:
      DOI: 10.1002/2016WR020016
       
  • An explicit, parsimonious, and accurate estimate for ponded infiltration
           into soils using the Green and Ampt Approach
    • Authors: John Selker; Shmuel Assouline
      Abstract: The Green and Ampt solution for vertical ponded infiltration is implicit in time, which makes the result often cumbersome to apply. Here we present a simple explicit solution for the position of the wetting front in time based on approximating the term describing early time behavior by means of the sum of gravitational flow and the exact solution for capillary imbibition. The result is within 1% of the exact implicit solution of vertical Green and Ampt infiltration. We also check the overall accuracy of the Green and Ampt approach, and find it to be within 15% of numerical simulation results for the same soils obtained with the Richards Equation. Hence, the proposed approximation adds essentially no error to the Green and Ampt approach, but greatly simplifies computation of infiltration. The approximation also makes explicit the role of the representation of capillarity, which can be adjusted in ways not possible with the implicit result. We find that predictions can be markedly improved by adjusting capillary versus gravitational drivers per soil texture, revealing both a limitation of the Green and Ampt approach, but also providing a potential refinement of Green and Ampt predictions per soil type (demonstrated for sandy and clayey soils). Further, the new approximation allows for simple computation of useful quantities such as flux and cumulative infiltration.
      PubDate: 2017-07-13T08:05:43.079472-05:
      DOI: 10.1002/2017WR021020
       
  • Flow of yield stress and Carreau fluids through rough-walled rock
           fractures: Prediction and experiments
    • Authors: Antonio Rodríguez de Castro; Giovanni Radilla
      Abstract: Many natural phenomena in geophysics and hydrogeology involve the flow of non-Newtonian fluids through natural rough-walled fractures. Therefore, there is considerable interest in predicting the pressure drop generated by complex flow in these media under a given set of boundary conditions. However, this task is markedly more challenging than the Newtonian case given the coupling of geometrical and rheological parameters in the flow law. The main contribution of this paper is to propose a simple method to predict the flow of commonly used Carreau and yield stress fluids through fractures. To do so, an expression relating the “in-situ” shear viscosity of the fluid to the bulk shear-viscosity parameters is obtained. Then, this “in-situ” viscosity is entered in the macroscopic laws to predict the flow rate-pressure gradient relations. Experiments with yield stress and Carreau fluids in two replicas of natural fractures covering a wide range of injection flow rates are presented and compared to the predictions of the proposed method. Our results show that the use of a constant shift parameter to relate “in-situ” and bulk shear viscosity is no longer valid in the presence of a yield stress or a plateau viscosity. Consequently, properly representing the dependence of the shift parameter on the flow rate is crucial to obtain accurate predictions. The proposed method predicts the pressure drop in a rough-walled fracture at a given injection flow rate by only using the shear rheology of the fluid, the hydraulic aperture of the fracture and the inertial coefficients as inputs.
      PubDate: 2017-07-13T08:05:40.098015-05:
      DOI: 10.1002/2017WR020520
       
  • A framework for the analysis of noncohesive bank erosion algorithms in
           morphodynamic modeling
    • Authors: G. Stecca; R. Measures, D. M. Hicks
      Abstract: In this paper we analyze the performance of several non-cohesive bank erosion algorithms to be embedded into two-dimensional models for river hydro-morphodynamics on non-moving meshes. To avoid the complexity of analyzing two-dimensional model results arising from the non-linear interaction between flow, fluvial transport and bank erosion, we develop a simplified framework. In detail, we reduce the two-dimensional morphodynamic model to a cross-sectional model under the assumption of longitudinal morphodynamic equilibrium, and apply bank erosion algorithms therein. To build candidate bank erosion models, we break down bank erosion algorithms into three modeling steps: identification of the bank, computation of sediment fluxes due to bank erosion, and bank updating. Different potential models are created by choosing different options for each step. We assess model performance against surveyed bank erosion over a flood event in the transitional Selwyn River, New Zealand. This study is preliminary to implementation of bank erosion in a fully two-dimensional setting, to model braided planform dynamics.
      PubDate: 2017-07-13T08:05:25.1788-05:00
      DOI: 10.1002/2017WR020756
       
  • Functional forms and price elasticities in a Discrete Continuous Choice
           Model of the residential water demand
    • Authors: F. A. Vásquez Lavín; J. I. Hernandez, R. D. Ponce, S.A. Orrego
      Abstract: During recent decades, water demand estimation has gained considerable attention from scholars. From an econometric perspective, the most used functional forms include log–log and linear specifications. Despite the advances in this field and the relevance for policymaking, little attention has been paid to the functional forms used in these estimations, and most authors have not provided justifications for their selection of functional forms. A discrete continuous choice model of the residential water demand is estimated using six functional forms (log–log, full-log, log-quadratic, semi-log, linear and Stone–Geary), and the expected consumption and price elasticity are evaluated. From a policy perspective, our results highlight the relevance of functional form selection for both the expected consumption and price elasticity.
      PubDate: 2017-07-10T08:57:05.847255-05:
      DOI: 10.1002/2016WR020250
       
  • Dam removal—listening in
    • Authors: M.M. Foley; J.R. Bellmore, J.E. O'Connor, J.J. Duda, A.E. East, G.E. Grant, C.W. Anderson, J.A. Bountry, M.J. Collins, P.J. Connolly, L.S. Craig, J.E. Evans, S.L. Greene, F.J. Magilligan, C.S. Magirl, J.J. Major, G.R. Pess, T.J. Randle, P.B. Shafroth, C.E. Torgersen, D. Tullos, A.C. Wilcox,
      Abstract: Dam removal is widely used as an approach for river restoration in the United States. The increase in dam removals—particularly large dams—and associated dam-removal studies over the last few decades motivated a working group at the USGS John Wesley Powell Center for Analysis and Synthesis to review and synthesize available studies of dam removals and their findings. Based on dam removals thus far, some general conclusions have emerged: (1) physical responses are typically fast, with the rate of sediment erosion largely dependent on sediment characteristics and dam-removal strategy; (2) ecological responses to dam removal differ among the affected upstream, downstream, and reservoir reaches; (3) dam removal tends to quickly reestablish connectivity, restoring the movement of material and organisms between upstream and downstream river reaches; (4) geographic context, river history, and land use significantly influence river restoration trajectories and recovery potential because they control broader physical and ecological processes and conditions; and (5) quantitative modeling capability is improving, particularly for physical and broad-scale ecological effects, and gives managers information needed to understand and predict long-term effects of dam removal on riverine ecosystems. Although these studies collectively enhance our understanding of how riverine ecosystems respond to dam removal, knowledge gaps remain because most studies have been short (< 5 years) and do not adequately represent the diversity of dam types, watershed conditions, and dam-removal methods in the U.S.
      PubDate: 2017-07-10T08:55:44.027686-05:
      DOI: 10.1002/2017WR020457
       
  • The influence of evaporation and rainfall on supratidal groundwater
           dynamics and salinity structure in a sandy beach
    • Authors: Xiaolong Geng; Michel C. Boufadel
      Abstract: Evaporation has been recognized as a major driving force affecting coastal aquifer systems. However, its effects on subsurface flow and salinity structure have not been investigated in sufficient detail. This paper presents field measurements and numerical simulations of pore-water flow and subsurface salinity structure in the supratidal zone of a sandy beach subjected to evaporation as well as rainfall. It was found that evaporation significantly increased pore-water salinity, up to 85 g/L, within a shallow layer, approximately 10 cm below the beach surface. The induced density gradient generated salt fingers near the beach surface, which caused local groundwater circulation (i.e., fingering flow). However, unlike inland aquifers, the salt fingering was significantly diminished by tidal action that prompted the horizontal mixing of salt in the beach. The subsequent precipitation (e.g., rainfall) diluted the evaporation-induced high saline plume near the beach surface, and drove the plume to migrate further downward; the plume gradually dispersed and was diluted along the groundwater pathways. The simulation results indicated that evaporation as well as precipitation at the beach surface induced complex driving mechanisms for supratidal groundwater flow. Depending on the intensity at the beach surface, evaporation and rainfall significantly altered the pore water flow and associate solute transport processes in the supratidal zone of the beach.
      PubDate: 2017-07-10T08:55:40.997358-05:
      DOI: 10.1002/2016WR020344
       
  • Fracture network created by 3-D printer and its validation using CT images
    • Authors: Anna Suzuki; Noriaki Watanabe, Kewen Li, Roland N. Horne
      Abstract: Understanding flow mechanisms in fractured media is essential for geoscientific research and geological development industries. This study used 3D printed fracture networks in order to control the properties of fracture distributions inside the sample. The accuracy and appropriateness of creating samples by the 3D printer was investigated by using a X-ray CT scanner. The CT scan images suggest that the 3D printer is able to reproduce complex three-dimensional spatial distributions of fracture networks. Use of hexane after printing was found to be an effective way to remove wax for the post-treatment. Local permeability was obtained by the cubic law and used to calculate the global mean. The experimental value of the permeability was between the arithmetic and geometric means of the numerical results, which is consistent with conventional studies. This methodology based on 3D printed fracture networks can help validate existing flow modeling and numerical methods.
      PubDate: 2017-07-06T15:53:49.781403-05:
      DOI: 10.1002/2017WR021032
       
  • Hydrologic controls on hyporheic exchange in a headwater mountain stream
    • Authors: Noah M. Schmadel; Adam S. Ward, Steven M. Wondzell
      Abstract: The spatial and temporal scales of hyporheic exchange within the stream corridor are controlled by stream discharge and groundwater inflow interacting with streambed morphology. While decades of study have resulted in a clear understanding of how morphologic form controls hyporheic exchange at the feature scale, we lack comparable predictive power related to stream discharge and the spatial structure of groundwater inflows at the reach scale, where spatial heterogeneity in both geomorphic setting and hydrologic forcing are present. In this study, we simulated vertical hyporheic exchange along a 600 m mountain stream reach under high, medium, and low stream discharge while considering groundwater inflow as negligible, spatially uniform, or proportional to upslope accumulated area. Most changes to hyporheic flow path residence time or length in response to stream discharge were small (< 5%), suggesting that discharge is a secondary control relative to morphologically-driven hyporheic exchange. Groundwater inflow was a primary control and mostly caused decreases in hyporheic flow path residence time and length. This finding generally agrees with expectations from the literature; however, flow path response was not consistent across the study reach. Instead, we found that flow paths driven by large hydraulic gradients coinciding with large morphologic features were less sensitive to changes in groundwater inflow than those driven by hydraulic gradients similar to the valley gradient. Our results indicate that consideration of heterogeneous arrangement of morphologic features is necessary to differentiate between hyporheic flow paths that persist in time and those that are sensitive to changing hydrologic conditions.
      PubDate: 2017-07-06T15:53:35.289424-05:
      DOI: 10.1002/2017WR020576
       
  • Tundra water budget and implications of precipitation underestimation
    • Authors: Anna K. Liljedahl; Larry D. Hinzman, Douglas L. Kane, Walter C. Oechel, Craig E. Tweedie, Donatella Zona
      Abstract: Difficulties in obtaining accurate precipitation measurements have limited meaningful hydrologic assessment for over a century due to performance challenges of conventional snowfall and rainfall gauges in windy environments. Here, we compare snowfall observations and bias adjusted snowfall to end-of-winter snow accumulation measurements on the ground for 16 years (1999-2014) and assess the implication of precipitation underestimation on the water balance for a low-gradient tundra wetland near Utqiagvik (formerly Barrow), Alaska (2007-2009). In agreement with other studies, and not accounting for sublimation, conventional snowfall gauges captured 23 to 56% of end-of-winter snow accumulation. Once snowfall and rainfall are bias adjusted, long-term annual precipitation estimates more than double (from 123 to 274 mm), highlighting the risk of studies using conventional or unadjusted precipitation that dramatically under-represent water balance components. Applying conventional precipitation information to the water balance analysis produced consistent storage deficits (79 to 152 mm) that were all larger than the largest actual deficit (75 mm), which was observed in the unusually low rainfall summer of 2007. Year-to-year variability in adjusted rainfall (±33 mm) was larger than evapotranspiration (±13 mm). Measured interannual variability in partitioning of snow into runoff (29% in 2008 to 68% in 2009) in years with similar end-of-winter snow accumulation (180 and 164 mm, respectively) highlights the importance of the previous summer's rainfall (25 and 60 mm, respectively) on spring runoff production. Incorrect representation of precipitation can therefore have major implications for Arctic water budget descriptions that in turn can alter estimates of carbon and energy fluxes.
      PubDate: 2017-07-06T15:52:41.93416-05:0
      DOI: 10.1002/2016WR020001
       
  • Micro-PIV measurements of multiphase flow of water and liquid CO2 in 2-D
           heterogeneous porous micromodels
    • Authors: Yaofa. Li; Farzan Kazemifar, Gianluca Blois, Kenneth T. Christensen
      Abstract: We present an experimental study of pore-scale flow dynamics of liquid CO2 and water in a two-dimensional heterogeneous porous micromodel, inspired by the structure of a reservoir rock, at reservoir-relevant conditions (80 bar, 21 °C). The entire process of CO2 infiltration into a water-saturated micromodel was captured using fluorescence microscopy and the micro-PIV method, which together reveal complex fluid displacement patterns and abrupt changes in velocity. The CO2 front migrated through the resident water in an intermittent manner, forming dendritic structures, termed fingers, in directions along, normal to, and even opposing the bulk pressure gradient. Such characteristics indicate the dominance of capillary fingering through the micromodel. Velocity burst events, termed Haines jumps, were also captured in the heterogeneous micromodel, during which the local Reynolds number was estimated to be ∼21 in the CO2 phase, exceeding the range of validity of Darcy's law. Furthermore, these drainage events were observed to be cooperative (i.e., across multiple pores simultaneously), with the zone of influence of such events extending beyond tens of pores, confirming, in a quantitative manner, that Haines jumps are non-local phenomena. After CO2 completely breaks through the porous section, shear-induced circulations caused by flowing CO2 were also observed, in agreement with previous studies using a homogeneous porous micromodel. To our knowledge, this study is the first quantitative measurement that incorporates both reservoir-relevant conditions and rock-inspired heterogeneity, and thus will be useful for pore-scale model development and validation.
      PubDate: 2017-07-06T15:52:34.978246-05:
      DOI: 10.1002/2017WR020850
       
  • Water security, risk, and economic growth: Insights from a dynamical
           systems model
    • Authors: Simon Dadson; Jim W. Hall, Dustin Garrick, Claudia Sadoff, David Grey, Dale Whittington
      Abstract: Investments in the physical infrastructure, human capital, and institutions needed for water resources management have been noteworthy in the development of most civilisations. These investments affect the economy in two distinct ways: (i) by improving the factor productivity of water in multiple economic sectors, especially those that are water intensive such as agriculture and energy; and (ii) by reducing acute and chronic harmful effects of water-related hazards like floods, droughts, and water-related diseases. The need for capital investment to mitigate risks and promote economic growth is widely acknowledged, but prior conceptual work on the relationship between water-related investments and economic growth has focused on the productive and harmful roles of water in the economy independently. Here the two influences are combined using a simple, dynamical systems model of water-related investment, risk, and growth. In cases where initial water security is low, initial investment in water-related assets enables growth. Without such investment, losses due to water-related hazards exert a drag on economic growth and may create a poverty trap. The presence and location of the poverty trap is context-specific and depends on the exposure of productive water-related assets to water-related risk. Exogenous changes in water-related risk can potentially push an economy away from a growth path towards a poverty trap. Our investigation shows that an inverted-U-shaped investment relation between the level of investment in water security and the current level of water security leads to faster rates of growth than the alternatives that we consider here, and that this relation is responsible for the ‘S'-curve that is posited in the literature. These results illustrate the importance of accounting for environmental and health risks in economic models and offer insights for the design of robust policies for investment in water-related productive assets to manage risk, in the face of environmental change.
      PubDate: 2017-07-06T15:51:03.239529-05:
      DOI: 10.1002/2017WR020640
       
  • Climatology of seasonal snowfall accumulation across the Sierra Nevada
           (USA): Accumulation rates, distributions, and variability
    • Authors: Laurie S. Huning; Steven A. Margulis
      Abstract: A detailed picture of how snowfall varies across high-elevation mountain ranges in both space and time remains a knowledge gap in understanding the montane hydrologic cycle. Previous studies generally used point-scale snow measurements in an attempt to represent the spatial variability of snowfall across a range; however, these traditional approaches provide incomplete insight into the cumulative snowfall (CS) distribution from the basin-scale to the mountain range-scale. In this study, a high-resolution, spatially-distributed snow reanalysis was utilized to characterize 31 winters (water years 1985-2015) of snowfall distributions, snowfall accumulation rates, and snowstorms across the Sierra Nevada (USA). The CS dataset (quantified in units of snow water equivalent) was verified against over 2600 station years of in situ observations. The seasonal CS was found to have mean and root-mean-squared differences of -4 cm and 12 cm, respectively, and a correlation of 0.96 with snow pillow observations. Using this novel CS information, results indicated that the CS accumulates rapidly across all 20 basins examined with, on average, at least 50% of the integrated CS accumulating in less than or equal to six days or three snowstorms over each basin. The largest (or leading) snowstorms each season yield ∼27% of the CS, on average, and most frequently last four days. Across the range, over 40% of the leading snowstorms occur in February. This study showed that the hydroclimatology of the Sierra Nevada is driven by hydrological extremes as manifested in the high inter-annual variability of its seasonally-integrated CS, 4.4-41.3 km3, during the 31 years.
      PubDate: 2017-07-06T15:50:37.264169-05:
      DOI: 10.1002/2017WR020915
       
  • Large-scale inverse model analyses employing fast randomized data
           reduction
    • Authors: Youzuo Lin; Ellen B. Le, Daniel O'Malley, Velimir V. Vesselinov, Tan Bui-Thanh
      Abstract: When the number of observations is large, it is computationally challenging to apply classical inverse modeling techniques. We have developed a new computationally-efficient technique for solving inverse problems with a large number of observations (e.g. on the order of 107 or greater). Our method, which we call the randomized geostatistical approach (RGA), is built upon the principal component geostatistical approach (PCGA). We employ a data reduction technique combined with the PCGA to improve the computational efficiency and reduce the memory usage. Specifically, we employ a randomized numerical linear algebra technique based on a so-called “sketching” matrix to effectively reduce the dimension of the observations without losing the information content needed for the inverse analysis. In this way, the computational and memory costs for RGA scale with the information content rather than the size of the calibration data. Our algorithm is coded in Julia and implemented in the MADS open-source high-performance computational framework (http://mads.lanl.gov). We apply our new inverse modeling method to invert for a synthetic transmissivity field. Compared to a standard geostatistical approach (GA), our method is more efficient when the number of observations is large. Most importantly, our method is capable of solving larger inverse problems than the standard GA and PCGA approaches. Therefore, our new model inversion method is a powerful tool for solving large-scale inverse problems. The method can be applied in any field and is not limited to hydrogeological applications such as the characterization of aquifer heterogeneity.
      PubDate: 2017-07-06T15:50:21.601744-05:
      DOI: 10.1002/2016WR020299
       
  • Information theory-based decision support system for integrated design of
           multivariable hydrometric networks
    • Authors: Jongho Keum; Paulin Coulibaly
      Abstract: Adequate and accurate hydrologic information from optimal hydrometric networks is an essential part of effective water resources management. Although the key hydrologic processes in the water cycle are interconnected, hydrometric networks (e.g., streamflow, precipitation, groundwater level) have been routinely designed individually. A decision support framework is proposed for integrated design of multi-variable hydrometric networks. The proposed method is applied to design optimal precipitation and streamflow networks simultaneously. The epsilon-dominance hierarchical Bayesian optimization algorithm was combined with Shannon entropy of information theory to design and evaluate hydrometric networks. Specifically, the joint entropy from the combined networks was maximized to provide the most information, and the total correlation was minimized to reduce redundant information. To further optimize the efficiency between the networks, they were designed by maximizing the conditional entropy of the streamflow network given the information of the precipitation network. Compared to the traditional individual variable design approach, the integrated multi-variable design method was able to determine more efficient optimal networks by avoiding the redundant stations. Additionally, four quantization cases were compared to evaluate their effects on the entropy calculations and the determination of the optimal networks. The evaluation results indicate that the quantization methods should be selected after careful consideration for each design problem since the station rankings and the optimal networks can change accordingly.
      PubDate: 2017-07-05T08:56:54.219017-05:
      DOI: 10.1002/2016WR019981
       
  • Exploring the role of trees in the evolution of meander bends: The
           Tagliamento River, Italy
    • Authors: Simone Zen; Angela M. Gurnell, Guido Zolezzi, Nicola Surian
      Abstract: To date, the role of riparian trees in the formation of scroll bars, ridges and swales during the evolution of meandering channels has been inferred largely from field observations with support from air photographs. In situ field observations are usually limited to relatively short periods of time, whereas the evolution of these morphological features may take decades. By combining field observations of inner bank morphology and overlying riparian woodland structure with a detailed historical analysis of airborne LiDAR data, panchromatic and color images, we reconstruct the spatial and temporal evolution of the morphology and vegetation across four meander bends of the Tagliamento River, Italy. Specifically we reveal (i) the appearance of deposited trees and elongated vegetated patches on the inner bank of meander bends following flood events; (ii) temporal progression from deposited trees, through small to larger elongated vegetated patches (pioneer islands), to their coalescence into long, linear vegetated features that eventually become absorbed into the continuous vegetation cover of the riparian forest; and (iii) a spatial correspondence between the resulting scrolls and ridge and swale topography, and tree cover development and persistence. We provide a conceptual model of the mechanisms by which vegetation can contribute to the formation of sequence of ridges and swales on the convex bank of meander bends.We discuss how these insights into the biomorphological processes that control meander bends advance can inform modelling activities that aim to describe the lateral and vertical accretion of the floodplain during the evolution of vegetated river meanders.
      PubDate: 2017-07-05T08:56:18.41963-05:0
      DOI: 10.1002/2017WR020561
       
  • Methane emission through ebullition from an estuarine mudflat: 2. Field
           observations and modeling of occurrence probability
    • Authors: Xi Chen; Karina VR Schäfer, Lee Slater
      Abstract: Ebullition can transport methane (CH4) at a much faster rate than other pathways, albeit over limited time and area, in wetland soils and sediments. However, field observations present large uncertainties in ebullition occurrences and statistic models are needed to describe the function relationship between probability of ebullition occurrence and water level changes. A flow-through chamber was designed and installed in a mudflat of an estuarine temperate marsh. Episodic increases in CH4 concentration signaling ebullition events were observed during ebbing tides (15 events over 456 ebbing tides) and occasionally during flooding tides (4 events over 455 flooding tides). Ebullition occurrence functions were defined using logistic regression as the relative initial and end water levels, as well as tidal amplitude were found to be the key functional variables related to ebullition events. Ebullition of methane was restricted by a surface frozen layer during winter; melting of this layer during spring thaw caused increases in CH4 concentration, with ebullition fluxes similar to those associated with large fluctuations in water level around spring tides. Our findings suggest that initial and end relative water levels, in addition to tidal amplitude, partly regulate ebullition events in tidal wetlands, modulated by the lunar cycle, storage of gas bubbles at different depths and seasonal changes in the surface frozen layer. Maximum tidal strength over a few days, rather than hourly water level, may be more closely associated with the possibility of ebullition occurrence as it represents a trade-off time-scale in between hourly and lunar periods.
      PubDate: 2017-07-05T08:56:14.988882-05:
      DOI: 10.1002/2016WR019720
       
  • Temporal dynamics in dominant runoff sources and flow paths in the Andean
           Páramo
    • Authors: Alicia Correa; David Windhorst, Doerthe Tetzlaff, Patricio Crespo, Rolando Célleri, Jan Feyen, Lutz Breuer
      Abstract: The relative importance of catchment's water provenance and flow paths varies in space and time, complicating the conceptualization of the rainfall-runoff response. We assessed the temporal dynamics in source areas, flow paths and age by End Member Mixing Analysis (EMMA), Hydrograph Separation (HS) and Inverse Transit Time Proxies (ITTPs) estimation within a headwater catchment in the Ecuadorian Andes. Twenty-two solutes, stable isotopes, the pH and electrical conductivity from a stream and twelve potential sources were analyzed. Four end members were required to satisfactorily represent the hydrological system, i.e., rainfall, spring water and water from the bottom layers of Histosols and Andosols. Water from Histosols in and near the riparian zone was the highest source contributor to runoff throughout the year (39% for the drier season, 45% for the wetter season), highlighting the importance of the water that is stored in the riparian zone. Spring water contributions to streamflow tripled during the drier season, as evidenced by geochemical signatures that are consistent with deeper flow paths rather than shallow interflow through Andosols. Rainfall exhibits low seasonal variation in this contribution. HS reveals that 94% and 84% is pre-event water in the drier and wetter seasons, respectively. From low to high flow conditions, all the sources increase their contribution except spring water. The relative age of streamwater decreased during wetter periods, when the contributing area of the riparian zone expands. The multi-method and multi-tracer approach enabled to closely study the interchanging importance of flow processes and water-source dynamics from an inter-annual perspective.
      PubDate: 2017-07-05T08:56:08.882866-05:
      DOI: 10.1002/2016WR020187
       
  • Estimating Water Retention Curves and Strength Properties of Unsaturated
           Sandy Soils from Basic Soil Gradation Parameters
    • Authors: Ji-Peng Wang; Nian Hu, Bertrand François, Pierre Lambert
      Abstract: This study proposed two pedotransfer functions (PTFs) to estimate sandy soil water retention curves. It is based on the van Genuchten's water retention model and from a semi-physical and semi-statistical approach. Basic gradation parameters of d60 as particle size at 60% passing and the coefficient of uniformity Cu are employed in the PTFs with two idealized conditions, the monosized scenario and the extremely polydisperse condition, satisfied. Water retention tests are carried out on 8 granular materials with narrow particle size distributions as supplementary data of the UNSODA database. The air entry value is expressed as inversely proportional to d60 and the parameter n, which is related to slope of water retention curve, is a function of Cu. The proposed PTFs, although have fewer parameters, have better fitness than previous PTFs for sandy soils. Furthermore, by incorporating with the suction stress definition, the proposed pedotransfer functions are imbedded in shear strength equations which provide a way to estimate capillary induced tensile strength or cohesion at a certain suction or degree of saturation from basic soil gradation parameters. The estimation shows quantitative agreement with experimental data in literature, and it also explains that the capillary induced cohesion is generally higher for materials with finer mean particle size or higher polydispersity.
      PubDate: 2017-07-05T08:56:03.845265-05:
      DOI: 10.1002/2017WR020411
       
  • HYPPS: A hybrid geostatistical modeling algorithm for subsurface modeling
    • Authors: Pejman Tahmasebi
      Abstract: Dealing with complex and geologically realistic modeling of subsurface systems requires detailed spatial datasets. Such a big data can be usually provided through an image. Despite various developments, the training image based techniques are still not well-designed for modeling multiscale and complex structures. Pixel-based methods honor the conditioning point data with poor reproduction of large-scale features, while some other techniques, termed pattern-based, represent a superior reproduction of long-range and complex structures and being biased around the conditioning data. In this paper, a new look at the geostatistical modeling using a hybrid pattern-pixel-based simulation (HYPPS) is proposed, wherein the pixel- and pattern-based techniques are used simultaneously. A perfect reproduction of the conditioning point data is achieved using the proposed HYPPS method. The algorithm is developed for single and multivariate simulations. This method is applied on different 2D/3D categorical data and the results show significant improvement over the previous techniques.
      PubDate: 2017-07-05T08:55:59.620935-05:
      DOI: 10.1002/2017WR021078
       
  • Quantifying the impacts of vegetation changes on catchment
           storage-discharge dynamics using paired catchment data
    • Authors: Lei Cheng; Lu Zhang, Francis H. S. Chiew, Josep G. Canadell, Fangfang Zhao, Ying-Ping Wang, Xianqun Hu, Kairong Lin
      Abstract: It is widely recognised that vegetation changes can significantly affect the local water availability. Methods have been developed to predict the effects of vegetation change on water yield or total streamflow. However, it is still a challenge to predict changes in base flow following vegetation change due to limited understanding of catchment storage-discharge dynamics. In this study, the power law relationship for describing catchment storage-discharge dynamics is reformulated to quantify the changes in storage-discharge relationship resulting from vegetation changes using streamflow data from six paired catchment experiments, of which two are deforestation catchments and four are afforestation catchments. Streamflow observations from the paired catchment experiments clearly demonstrate that vegetation changes have led to significant changes in catchment storage-discharge relationships, accounting for about 83–128% of the changes in groundwater discharge in the treated catchments. Deforestation has led to increases in groundwater discharge (or base flow) but afforestation has resulted in decreases in groundwater discharge. Further analysis shows that the contribution of changes in groundwater discharge to the total changes in streamflow varies greatly amongst experimental catchments ranging from 12% to 80% with a mean of 38±22% (μ±σ). This study proposed a new method to quantify the effects of vegetation changes on groundwater discharge from catchment storage and will improve our predictability about the impacts of vegetation changes on catchment water yields.
      PubDate: 2017-07-05T08:55:56.701719-05:
      DOI: 10.1002/2017WR020600
       
  • A soil column model for predicting the interaction between water table and
           evapotranspiration
    • Authors: Mathilde Maquin; Emmanuel Mouche, Claude Mügler, Marie-Claire Pierret, Daniel Viville
      Abstract: Lateral water fluxes are not realistically taken into account in soil column models, although they influence the dynamic evolution of the vertical soil moisture profile. By neglecting these fluxes, the modeling of the soil-vegetation-atmosphere continuum is incomplete, and the feedbacks between these three compartments cannot be fully simulated. These fluxes have an importance in the different fields where soil column models are used: hydrology, hydrometeorology, biogeochemical cycles, ecology, soil weathering. This paper introduces a novel Hydrological Hillslope-based Soil Column model (H2SC) that simulates the temporal evolution of the water table depth and evapotranspiration fluxes and their interaction. The interconnected processes are infiltration, evapotranspiration, vertical soil water movements, and the non-explicitly modeled lateral fluxes flowing through the soil column. These lateral fluxes are modeled as a drainage function built from physically-based equations that describe a simplified hillslope hydrology. This drainage function can be easily implemented in any soil column model without penalizing computational times. The H2SC model was validated on numerical experiments where a 2-D hillslope simulation performed with an integrated hydrologic model was compared with simulations using the H2SC 1-D model. Each of the H2SC simulations represents a specific location of a soil column along the hillslope. Different climate forcings, soil properties and geometric shapes of the hillslope were tested. The model was then applied at the locations of two piezometers in the Strengbach catchment, France. The model reproduced the temporal evolution of the water table level fairly well for both the numerical experiments and for the real test case.
      PubDate: 2017-07-05T08:55:53.828683-05:
      DOI: 10.1002/2016WR020183
       
  • Tree-based flood damage modeling of companies: Damage processes and model
           performance
    • Authors: Tobias Sieg; Kristin Vogel, Bruno Merz, Heidi Kreibich
      Abstract: Reliable flood risk analyses, including the estimation of damage, are an important prerequisite for efficient risk management. However, not much is known about flood damage processes affecting companies. Thus, we conduct a flood damage assessment of companies in Germany with regard to two aspects. Firstly, we identify relevant damage-influencing variables. Secondly, we assess the prediction performance of the developed damage models with respect to the gain by using an increasing amount of training data and a sector-specific evaluation of the data. Random Forests are trained with data from two post-event surveys after flood events occurring in the years 2002 and 2013. For a sector-specific consideration, the data set is split into four subsets corresponding to the manufacturing, commercial, financial, and service sectors. Further, separate models are derived for three different company assets: buildings, equipment, and goods and stock. Calculated variable importance values reveal different variable sets relevant for the damage estimation, indicating significant differences in the damage process for various company sectors and assets. With an increasing number of data used to build the models, prediction errors decrease. Yet, the effect is rather small and seems to saturate for a data set size of several hundred observations. In contrast, the prediction improvement achieved by a sector-specific consideration is more distinct, especially for damage to equipment and goods and stock. Consequently, sector-specific data acquisition and a consideration of sector-specific company characteristics in future flood damage assessments is expected to improve the model performance more than a mere increase in data.
      PubDate: 2017-07-05T08:55:45.713293-05:
      DOI: 10.1002/2017WR020784
       
  • The costs of delay in infrastructure investments: A comparison of 2001 and
           2014 household water supply coping costs in the Kathmandu Valley, Nepal
    • Authors: Yogendra Gurung; Jane Zhao, Bal Kumar KC, Xun Wu, Bhim Suwal, Dale Whittington
      Abstract: In 2001 we conducted a survey of 1500 randomly sampled households in Kathmandu to determine the costs people were incurring to cope with Kathmandu's poor quality, unreliable piped water supply system. From 2001 until 2014 there was little additional public investment in the municipal water supply system. In the summer of 2014 we attempted to re-interview all 1500 households in our 2001 sample to determine how they had managed to deal with the growing water shortage and the deteriorating condition of the piped water infrastructure in Kathmandu, and to compare their coping costs in 2014 with those we first estimated in 2001.Average household coping costs more than doubled in real terms over the period from 2001 to 2014, from US$5 to US$12 per month (measured in 2014 prices). The composition of household coping costs changed from 2001 to 2014, as households responded to the deteriorating condition of the piped water infrastructure by drilling more private wells, purchasing water from both tanker truck and bottled water vendors, and installing more storage tanks. These investments and expenditures resulted in a decline in the time households spend collecting water from outside the home. Our analysis suggests that the significant increase in coping costs between 2001 to 2014 may provide an opportunity for the municipal water utility to substantially increase water tariffs if the quantity and quality of piped services can be improved. However, the capital investments made by some households in private wells, pumping and treatment systems, and storage tanks in response to the delay in infrastructure investment may lock them into current patterns of water use, at least in the short run, and thus make it difficult to predict how they would respond to tariff increases for improved piped water services.
      PubDate: 2017-07-05T08:55:40.838607-05:
      DOI: 10.1002/2016WR019529
       
  • Modeling the probability distribution of peak discharge for infiltrating
           hillslopes
    • Authors: Giorgio Baiamonte; Vijay P. Singh
      Abstract: Hillslope response plays a fundamental role in the prediction of peak discharge at the basin outlet. The peak discharge for the critical duration of rainfall and its probability distribution are needed for designing urban infrastructure facilities. This study derives the probability distribution, denoted as GABS model, by coupling three models: (1) the Green-Ampt model for computing infiltration, (2) the kinematic wave model for computing discharge hydrograph from the hillslope, and (3) the intensity-duration-frequency (IDF) model for computing design rainfall intensity. The Hortonian mechanism for runoff generation is employed for computing the surface runoff hydrograph. Since the antecedent soil moisture condition (ASMC) significantly affects the rate of infiltration, its effect on the probability distribution of peak discharge is investigated. Application to a watershed in Sicily, Italy, shows that with the increase of probability, the expected effect of ASMC to increase the maximum discharge diminishes. Only for low values of probability, the critical duration of rainfall is influenced by ASMC, whereas its effect on the peak discharge seems to be less for any probability. For a set of parameters, the derived probability distribution of peak discharge seems to be fitted by the gamma distribution well. Finally, an application to a small watershed, with the aim to test the possibility to arrange in advance the rational runoff coefficient tables to be used for the rational method, and a comparison between peak discharges obtained by the GABS model with those measured in an experimental flume for a loamy-sand soil, were carried out.
      PubDate: 2017-07-05T08:55:30.443561-05:
      DOI: 10.1002/2016WR020109
       
  • Bayesian spectral likelihood for hydrological parameter inference
    • Authors: Bettina Schaefli; Dmitri Kavetski
      Abstract: This paper proposes a spectral-domain likelihood function for the Bayesian estimation of hydrological model parameters from a time series of model residuals. The spectral-domain error model is based on the Power-Density-Spectrum (PDS) of the stochastic process assumed to describe residual errors. The Bayesian Spectral Likelihood (BSL) is mathematically equivalent to the corresponding Bayesian Time-domain Likelihood (BTL) and yields the same inference when all residual error assumptions are satisfied (and all residual error parameters are inferred). However, the BSL likelihood function does not depend on the residual error distribution in the original time-domain, which offers a theoretical advantage in terms of robustness for hydrological parameter inference. The theoretical properties of BSL are demonstrated and compared to BTL and a previously proposed spectral likelihood by Montanari and Toth (2007), using a set of synthetic case studies and a real case study based on the Leaf River catchment in the US. The empirical analyses confirm the theoretical properties of BSL when applied to heteroscedastic and autocorrelated error models (where heteroscedasticity is represented using the log-transformation and autocorrelation is represented using an AR(1) process). Unlike MTL, the use of BSL did not introduce additional parametric uncertainty compared to BTL. Future work will explore the application of BSL to challenging modeling scenarios in arid catchments and “indirect” calibration with non-concomitant input/output time series.
      PubDate: 2017-07-05T08:55:23.155604-05:
      DOI: 10.1002/2016WR019465
       
  • Predicting nonstationary flood frequencies: Evidence supports an updated
           stationarity thesis in the United States
    • Authors: Adam Luke; Jasper A. Vrugt, Amir AghaKouchak, Richard Matthew, Brett F. Sanders
      Abstract: Nonstationary extreme value analysis (NEVA) can improve the statistical representation of observed flood peak distributions compared to stationary (ST) analysis, but management of flood risk relies on predictions of out-of-sample distributions for which NEVA has not been comprehensively evaluated. In this study, we apply split-sample testing to 1250 annual maximum discharge records in the United States and compare the predictive capabilities of NEVA relative to ST extreme value analysis using a log-Pearson Type III (LPIII) distribution. The parameters of the LPIII distribution in the ST and nonstationary (NS) models are estimated from the first half of each record using Bayesian inference. The second half of each record is reserved to evaluate the predictions under the ST and NS models. The NS model is applied for prediction by (1) extrapolating the trend of the NS model parameters throughout the evaluation period and (2) using the NS model parameter values at the end of the fitting period to predict with an updated ST model (uST). Our analysis shows that the ST predictions are preferred, overall. NS model parameter extrapolation is rarely preferred. However, if fitting period discharges are influenced by physical changes in the watershed, for example from anthropogenic activity, the uST model is strongly preferred relative to ST and NS predictions. The uST model is therefore recommended for evaluation of current flood risk in watersheds that have undergone physical changes. Supporting information includes a MATLAB® program that estimates the (ST/NS/uST) LPIII parameters from annual peak discharge data through Bayesian inference.
      PubDate: 2017-07-05T08:26:15.278775-05:
      DOI: 10.1002/2016WR019676
       
  • Sworn testimony of the model evidence: Gaussian Mixture Importance (GAME)
           sampling
    • Authors: Elena Volpi; Gerrit Schoups, Giovanni Firmani, Jasper A. Vrugt
      Abstract: What is the “best” model' The answer to this question lies in part in the eyes of the beholder, nevertheless a good model must blend rigorous theory with redeeming qualities such as parsimony and quality of fit. Model selection is used to make inferences, via weighted averaging, from a set of K candidate models, Mk; k = 1,…,K), and help identify which model is most supported by the observed data, Ỹ = (ỹ1, …, ỹn). Here, we introduce a new and robust estimator of the model evidence, p(Ỹ Mk), which acts as normalizing constant in the denominator of Bayes' theorem and provides a single quantitative measure of relative support for each hypothesis that integrates model accuracy, uncertainty and complexity. However, p(Ỹ Mk)$is analytically intractable for most practical modeling problems. Our method, coined GAussian Mixture importancE (GAME) sampling, uses bridge sampling of a mixture distribution fitted to samples of the posterior model parameter distribution derived from MCMC simulation. We benchmark the accuracy and reliability of GAME sampling by application to a diverse set of multivariate target distributions (up to 100 dimensions) with known values of p(Ỹ Mk) and to hypothesis testing using numerical modeling of the rainfall-runoff transformation of the Leaf River watershed in Mississippi, USA. These case studies demonstrate that GAME sampling provides robust and unbiased estimates of the evidence at a relatively small computational cost outperforming commonly used estimators. The GAME sampler is implemented in the MATLAB package of DREAM [Vrugt, 2016] and simplifies considerably scientific inquiry through hypothesis testing and model selection.
      PubDate: 2017-07-05T08:25:22.839054-05:
      DOI: 10.1002/2016WR020167
       
  • Landform features and seasonal precipitation predict shallow groundwater
           influence on temperature in headwater streams
    • Authors: Zachary C. Johnson; Craig D. Snyder, Nathaniel P. Hitt
      Abstract: Headwater stream responses to climate change will depend in part on groundwater-surface water exchanges. We used linear modeling techniques to partition likely effects of shallow groundwater seepage and air temperature on stream temperatures for 79 sites in nine focal watersheds using hourly air and water temperature measurements collected during summer months from 2012-2015 in Shenandoah National Park, Virginia, USA. Shallow groundwater effects exhibited more variation within watersheds than between them, indicating the importance of reach-scale assessments and the limited capacity to extrapolate upstream groundwater influences from downstream measurements. Boosted regression tree (BRT) models revealed intricate interactions among geomorphological landform features (stream slope, elevation, network length, contributing area, and channel confinement) and seasonal precipitation patterns (winter, spring, and summer months) that together were robust predictors of spatial and temporal variation in groundwater influence on stream temperatures. The final BRT model performed well for training data and cross-validated samples (correlation = 0.984 and 0.760, respectively). Geomorphological and precipitation predictors of groundwater influence varied in their importance between watersheds, suggesting differences in spatial and temporal controls of recharge dynamics and the depth of the groundwater source. We demonstrate an application of the final BRT model to predict groundwater effects from landform and precipitation covariates at 1075 new sites distributed at 100-m increments within focal watersheds. Our study provides a framework to estimate effects of groundwater seepage on stream temperature in unsampled locations. We discuss applications for climate change research to account for groundwater-surface water interactions when projecting future thermal thresholds for stream biota.
      PubDate: 2017-06-26T12:22:38.59306-05:0
      DOI: 10.1002/2017WR020455
       
  • On the choice of the demand and hydraulic modeling approach to WDN
           real-time simulation
    • Authors: E. Creaco; Giuseppe Pezzinga, Dragan Savic
      Abstract: This paper aims to analyse two demand modelling approaches, i.e. top-down deterministic (TDA) and bottom-up stochastic (BUA), with particular reference to their impact on the hydraulic modelling of water distribution networks (WDNs). In the applications, the hydraulic modelling is carried out through the extended period simulation (EPS) and unsteady flow modelling (UFM). Taking as benchmark the modelling conditions that are closest to the WDN's real operation (UFM+BUA), the analysis showed that the traditional use of EPS+TDA produces large pressure head and water discharge errors, which can be attenuated only when large temporal steps (up to 1 hour in the case-study) are used inside EPS. The use of EPS+BUA always yields better results. Indeed, EPS+BUA already gives a good approximation of the WDN's real operation when intermediate temporal steps (larger than 2 min in the case-study) are used for the simulation. The trade-off between consistency of results and computational burden makes EPS+BUA the most suitable tool for real-time WDN simulation, while benefitting from data acquired through smart meters for the parameterization of demand generation models.
      PubDate: 2017-06-26T08:14:51.149651-05:
      DOI: 10.1002/2016WR020104
       
  • Effects of episodic rainfall on a subterranean estuary
    • Authors: Xiayang Yu; Pei Xin, Chunhui Lu, Clare Robinson, Ling Li, D. A. Barry
      Abstract: Numerical simulations were conducted to examine the effect of episodic rainfall on nearshore groundwater dynamics in a tidally-influenced unconfined coastal aquifer, with a focus on both long- (yearly) and short-term (daily) behavior of submarine groundwater discharge (SGD) and seawater intrusion (SWI). The results showed non-linear interactions among the processes driven by rainfall, tides and density-gradients. Rainfall-induced infiltration increased the yearly averaged fresh groundwater discharge to the ocean but reduced the extents of the saltwater wedge and upper saline plume as well as the total rate of seawater circulation through both zones. Overall, the net effect of the interactions led to an increase of the SGD. The nearshore groundwater responded to individual rainfall events in a delayed and cumulative fashion, as evident in the variations of daily averaged SGD and salt stored in the saltwater wedge (quantifying the extent of SWI). A generalized linear model (GLM) along with a Gamma distribution function was developed to describe the delayed and prolonged effect of rainfall events on short-term groundwater behavior. This model, validated with results of daily averaged SGD and SWI from the simulations of groundwater and solute transport using independent rainfall datasets, performed well in predicting the behavior of the nearshore groundwater system under the combined influence of episodic rainfall, tides and density-gradients. The findings and developed GLM form a basis for evaluating and predicting SGD, SWI and associated mass fluxes from unconfined coastal aquifers under natural conditions, including episodic rainfall.
      PubDate: 2017-06-26T08:14:47.181153-05:
      DOI: 10.1002/2017WR020809
       
  • Suspended sediment and turbidity after road construction/improvement and
           forest harvest in streams of the Trask River Watershed Study, Oregon
    • Authors: Ivan Arismendi; Jeremiah D. Groom, Maryanne Reiter, Sherri L. Johnson, Liz Dent, Mark Meleason, Alba Argerich, Arne E. Skaugset
      Abstract: Transport of fine-grained sediment from unpaved forest roads into streams is a concern due to the potential negative effects of additional suspended sediment on aquatic ecosystems. Here, we compared turbidity and suspended sediment concentration (SSC) dynamics in five non-fish bearing coastal Oregon streams above and below road crossings, during three consecutive time periods (‘before', ‘after road construction/improvement', and ‘after forest harvest and hauling'). We hypothesized that the combined effects of road construction/improvement and the hauling following forest harvest would increase turbidity and SSC in these streams. We tested whether the differences between paired samples from above and below road crossing exceeded various biological thresholds, using literature values of biological responses to increases in SSC and turbidity. Overall, we found minimal increases of both turbidity and SSC after road improvement, forest harvest, and hauling. Because flow is often used as a surrogate for turbidity or SSC we examined these relationships using data from locations above road crossings that were unaffected by roads or forest harvest and hauling. In addition, we examined the association between turbidity and SSC for these background locations. We found a positive, but in some cases weak association between flow and turbidity, and between flow and SSC; the relationship between turbidity and SSC was more robust, but also inconsistent among sites over time. In these low order streams, the concentrations and transport of suspended sediment seems to be highly influenced by the variability of local conditions. Our study provides an expanded understanding of current forest road management practice effects on fine-grained sediment in streams and introduces alternative metrics using multiple thresholds to evaluate potential indicators of biological relevance.
      PubDate: 2017-06-26T08:14:44.220173-05:
      DOI: 10.1002/2016WR020198
       
  • Predicting organic matter, nitrogen and phosphorus concentrations in
           runoff from peat extraction sites using partial least squares regression
    • Authors: T. Tuukkanen; H. Marttila, B. Kløve
      Abstract: Organic matter and nutrient export from drained peatlands is affected by complex hydrological and biogeochemical interactions. Here, partial least squares regression (PLSR) was used to relate various soil and catchment characteristics to variations in chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) concentrations in runoff. Peat core samples and water quality data were collected from 15 peat extraction sites in Finland. PLSR models constructed by cross-validation and variable selection routines predicted 92, 88, and 95% of the variation in mean COD, TN, and TP concentration in runoff, respectively. The results showed that variations in COD were mainly related to net production (temperature and water-extractable dissolved organic carbon (DOC)), hydrology (topographical relief), and solubility of dissolved organic matter (peat sulfur (S) and calcium (Ca) concentrations). Negative correlations for peat S and runoff COD indicated that acidity from oxidation of organic S stored in peat may be an important mechanism suppressing organic matter leaching. Moreover, runoff COD was associated with peat aluminum (Al), P, and sodium (Na) concentrations. Hydrological controls on TN and COD were similar (i.e., related to topography), whereas degree of humification, bulk density, and water-extractable COD and Al provided additional explanations for TN concentration. Variations in runoff TP concentration were attributed to erosion of particulate P, as indicated by a positive correlation with suspended sediment concentration (SSC), and factors associated with metal-humic complexation and P adsorption (peat Al, water-extractable P, and water-extractable iron (Fe)).
      PubDate: 2017-06-26T08:14:35.003605-05:
      DOI: 10.1002/2017WR020557
       
  • Institutional change to support regime transformation: lessons from
           Australia's water sector
    • Authors: Lara Werbeloff; Rebekah Brown, Chris Cocklin
      Abstract: Institutional change is fundamental to regime transformation, and a necessary part of moving towards integrated water management. However, insight into the role of institutional change processes in such transitions is currently limited. A more nuanced understanding of institutional frameworks is necessary, both to advance understanding of institutional change in the context of transitions towards improved water management, and to inform strategies for guiding such processes. To this end, we examine two contemporary cases of transformative change in Australia's urban water sector, exploring the evolution of institutional change in each city. This paper offers insights into regime transformation, providing guidance on types of institutional structures and the ways structure-change initiatives can be sequenced to support a transition. The results reveal the importance of regulation in embedding regime change, and suggest that engagement with structural frameworks should begin early in transition processes to ensure the timely introduction of supporting regulation. Our findings also highlight the inextricable link between culture- and structure-based change initiatives, and the importance of using a diverse range of institutional change mechanisms in a mutually reinforcing way to provide a strong foundation for change. These findings provide a foundation for further scholarly examination of institutional change mechanisms, while also serving to inform the strategic activities of transition-oriented organisations and actors.
      PubDate: 2017-06-26T08:12:58.989952-05:
      DOI: 10.1002/2016WR020289
       
  • Drought impacts to water footprints and virtual water transfers of the
           Central Valley of California
    • Authors: Landon Marston; Megan Konar
      Abstract: The Central Valley of California is one of the most productive agricultural locations in the world, which is made possible by a complex and vast irrigation system. Beginning in 2012, California endured one of the worst droughts in its history. Local impacts of the drought have been evaluated, but it is not yet well understood how the drought reverberated through the global food system. Here, we quantify drought impacts to the water footprint (WF) of agricultural production and virtual water transfers (VWT) from the Central Valley of California. To do this, we utilize high-resolution spatial and temporal datasets and a crop model from pre-drought conditions (2011) through three years of exceptional drought (2012-2014). Despite a 12% reduction in harvested area, the WF of agricultural production in the Central Valley increased by 3%. This was due to greater crop water requirements from higher temperatures and a shift to more water-intensive orchard and vine crops. The groundwater WF increased from 7.00 km3 in 2011 to 13.63 km3 in 2014, predominantly in the Tulare Basin. Transfers of food commodities declined by 1% during the drought, yet total VWT increased by 3% (0.51 km3). From 2011 to 2014, groundwater VWT increased by 3.42 km3, offsetting the 0.94 km3 reduction in green VWT and the 1.96 km3 decrease in surface VWT. During the drought, local and global consumers nearly doubled their reliance on the Central Valley Aquifer. These results indicate that drought may strengthen the telecoupling between groundwater withdrawals and distant consumers of agricultural commodities.
      PubDate: 2017-06-23T07:41:01.995525-05:
      DOI: 10.1002/2016WR020251
       
  • Environmental hedging: Theory and method for reconciling reservoir
           operations for downstream ecology and water supply
    • Authors: L. E. Adams; J. R. Lund, P. B. Moyle, R. M. Quiñones, J. D. Herman, T. A. O'Rear
      Abstract: Building reservoir release schedules to manage engineered river systems can involve costly tradeoffs between storing and releasing water. As a result, the design of release schedules requires metrics that quantify the benefit and damages created by releases to the downstream ecosystem. Such metrics should support making operational decisions under uncertain hydrologic conditions, including drought and flood seasons. This study addresses this need and develops a reservoir operation rule structure and method to maximize downstream environmental benefit while meeting human water demands. The result is a general approach for hedging downstream environmental objectives. A multi-stage stochastic mixed-integer non-linear program with Markov Chains, identifies optimal "environmental hedging," releases to maximize environmental benefits subject to probabilistic seasonal hydrologic conditions, current, past, and future environmental demand, human water supply needs, infrastructure limitations, population dynamics, drought storage protection, and the river's carrying capacity. Environmental hedging ‘hedges bets' for drought by reducing releases for fish, sometimes intentionally killing some fish early to reduce the likelihood of large fish kills and storage crises later. This approach is applied to Folsom reservoir in California to support survival of fall-run Chinook salmon in the Lower American River for a range of carryover and initial storage cases. Benefit is measured in terms of fish survival; maintaining self-sustaining native fish populations is a significant indicator of ecosystem function. Environmental hedging meets human demand and outperforms other operating rules, including the current Folsom operating strategy, based on metrics of fish extirpation and water supply reliability.
      PubDate: 2017-06-23T07:40:30.059204-05:
      DOI: 10.1002/2016WR020128
       
  • The effect of flooding on mental health: Lessons learned for building
           resilience
    • Authors: Sébastien Foudi; Nuria Osés-Eraso, Ibon Galarraga
      Abstract: Risk management and climate adaptation literature focuses mainly on reducing the impacts of, exposure to and vulnerability to extreme events such as floods and droughts. Posttraumatic stress disorder is one of the most important impacts related to these events, but also a relatively under-researched topic outside original psychopathological contexts. We conduct a survey to investigate the mental stress caused by floods. We focus on hydrological, individual and collective drivers of posttraumatic stress. We assess stress with flood-specific health scores and the GHQ-12 General Health Questionnaire. Our findings show that the combination of water depth and flood velocity measured via a Hazard Class Index is an important stressor; and that mental health resilience can be significantly improved by providing the population with adequate information. More specifically, the paper shows that psychological distress can be reduced by i) coordinating awareness of flood risks and flood protection and prevention behaviour; ii) developing the ability to protect oneself from physical, material and intangible damage; iii) designing simple insurance procedures and protocols for fast recovery; and iv) learning from previous experiences.
      PubDate: 2017-06-23T07:40:21.872846-05:
      DOI: 10.1002/2017WR020435
       
  • Comment on “Beyond the SCS-CN method: A theoretical framework for
           spatially lumped rainfall-runoff response” by M.S. Bartlett, A.J.
           Parolari, J.J. McDonnell and A. Porporato
    • Authors: Fred L. Ogden; Richard “Pete” Hawkins, M. Todd Walter, David C. Goodrich
      Abstract: Bartlett et al. [2016] performed a re-interpretation and modification of the space-time lumped USDA NRCS (formerly SCS) Curve Number (CN) method to extend its applicability to forested watersheds. We believe that the well documented limitations of the CN method severely constrains the applicability of the modifications proposed by Bartlett et al. [2016]. This forward-looking comment urges the research communities in hydrologic science and engineering to consider the CN method as a stepping stone that has outlived its usefulness in research. The CN method fills a narrow niche in certain settings as a parsimonious method having utility as an empirical equation to estimate runoff from a given amount of rainfall, which originated as a static functional form that fits rainfall-runoff data sets. Sixty five years of use and multiple reinterpretations have not resulted in improved hydrological predictability using the method. We suggest that the research community should move forward by (1) identifying appropriate dynamic hydrological model formulations for different hydro-geographic settings, (2) specifying needed model capabilities for solving different classes of problems (e.g. flooding, erosion/sedimentation, nutrient transport, water management, etc.) in different hydro-geographic settings, and (3) expanding data collection and research programs to help ameliorate the so-called “over-parameterization” problem in contemporary modeling. Many decades of advances in geo-spatial data and processing, computation, and understanding are being squandered on continued focus on the static CN regression method. It is time to truly “move beyond” the Curve Number method.
      PubDate: 2017-06-22T13:10:25.93796-05:0
      DOI: 10.1002/2016WR020176
       
  • Modeling the isotopic evolution of snowpack and snowmelt: Testing a
           spatially distributed parsimonious approach
    • Authors: Pertti Ala-aho; Doerthe Tetzlaff, James P. McNamara, Hjalmar Laudon, Patrick Kormos, Chris Soulsby
      Abstract: Use of stable water isotopes has become increasingly popular in quantifying water flow paths and travel times in hydrological systems using tracer-aided modeling. In snow-influenced catchments snow melt produces a traceable isotopic signal, which differs from original snowfall isotopic composition because of isotopic fractionation in the snowpack. These fractionation processes in snow are relatively well-understood, but representing their spatiotemporal variability in tracer-aided studies remains a challenge. We present a novel, parsimonious modeling method to account for the snowpack isotope fractionation and estimate isotope ratios in snowmelt water in a fully spatially distributed manner. Our model introduces two calibration parameters that alone account for the isotopic fractionation caused by sublimation from interception and ground snow storage, and snowmelt fractionation progressively enriching the snowmelt runoff. The isotope routines are linked to a generic process-based snow interception-accumulation-melt model facilitating simulation of spatially distributed snowmelt runoff. We use a synthetic modeling experiment to demonstrate the functionality of the model algorithms in different landscape locations and under different canopy characteristics. We also provide a proof-of-concept model test and successfully reproduce isotopic ratios in snowmelt runoff sampled with snowmelt lysimeters in two long-term experimental catchment with contrasting winter conditions. To our knowledge the method is the first such tool to allow estimation of the spatially distributed nature of isotopic fractionation in snowpacks and the resulting isotope ratios in snowmelt runoff. The method can thus provide a useful tool for tracer-aided modeling to better understand the integrated nature of flow, mixing and transport processes in snow-influenced catchments.
      PubDate: 2017-06-21T03:35:26.386532-05:
      DOI: 10.1002/2017WR020650
       
  • Reply to Comment on “Beyond the SCS-CN method: A theoretical framework
           for spatially lumped rainfall-runoff response”
    • Authors: M. S. Bartlett; A. J. Parolari, J. J. McDonnell, A. Porporato
      PubDate: 2017-06-21T03:30:50.236238-05:
      DOI: 10.1002/2017WR020456
       
  • Doing Ecohydrology Backward: Inferring Wetland Flow and Hydroperiod from
           Landscape Patterns
    • Authors: Subodh Acharya; David A. Kaplan, James W. Jawitz, Matthew J. Cohen
      Abstract: Human alterations to hydrology have globally impacted wetland ecosystems. Preventing or reversing these impacts is a principal focus of restoration efforts. However, restoration effectiveness is often hampered by limited information on historical landscape properties and hydrologic regime. To help address this gap, we developed a novel statistical approach for inferring flows and inundation frequency (i.e., hydroperiod, HP) in wetlands where changes in spatial vegetation and geomorphic patterns have occurred due to hydrologic alteration. We developed an analytical expression for HP as a transformation of the landscape-scale stage-discharge relationship. We applied this model to the Everglades “ridge-slough” (RS) landscape, a patterned, lotic peatland in southern Florida that has been drastically degraded by compartmentalization, drainage and flow diversions. The new method reliably estimated flow and HP for a range of RS landscape patterns. Crucially, ridge-patch anisotropy and elevation above sloughs were strong drivers of flow-HP relationships. Increasing ridge heights markedly increased flow required to achieve sufficient HP to support peat accretion. Indeed, ridge heights inferred from historical accounts would require boundary flows three to four times greater than today, which agrees with restoration flow estimates from more complex, spatially distributed models. While observed loss of patch anisotropy allows HP targets to be met with lower flows, such landscapes likely fail to support other ecological functions. This work helps inform restoration flows required to restore stable ridge-slough patterning and positive peat accretion in this degraded ecosystem, and, more broadly, provides tools for exploring interactions between landscape and hydrology in lotic wetlands and floodplains.
      PubDate: 2017-06-21T03:30:32.206325-05:
      DOI: 10.1002/2017WR020516
       
  • Inferring subsurface heterogeneity from push-drift tracer tests
    • Authors: Scott K. Hansen; Velimir V. Vesselinov, Paul W. Reimus, Zhiming Lu
      Abstract: We consider the late-time tailing in a tracer test performed with a push-drift methodology (i.e., quasi-radial injection followed by drift under natural gradient). Numerical simulations of such tests are performed on 1000 multi-Gaussian 2D log-hydraulic conductivity field realizations of varying heterogeneity, each under eight distinct mean flow directions. The ensemble pdfs of solute return times are found to exhibit power law tails for each considered variance of the log-hydraulic conductivity field, σln⁡K2. The tail exponent is found to relate straightforwardly to EQσln⁡K2 and, within the parameter space we explored, to be independent of push-phase pumping rate, pumping duration, and local-scale dispersivity. We conjecture that individual push-drift tracer tests in wells with screened intervals much greater than the vertical correlation length of the aquifer will exhibit quasi-ergodicity and that their tail exponent may be used to infer EQσln⁡K2. We calibrate a predictive relationship of this sort from our Monte Carlo study, and apply it to data from a push-drift test performed at a site of approximately known heterogeneity—closely matching the existing best estimate of heterogeneity.
      PubDate: 2017-06-19T17:06:52.938569-05:
      DOI: 10.1002/2017WR020852
       
  • The foam drainage equation for drainage dynamics in unsaturated porous
           media
    • Authors: P. Lehmann; F. Hoogland, S. Assouline, D. Or
      Abstract: Similarity in liquid-phase configuration and drainage dynamics of wet foam and gravity drainage from unsaturated porous media expands modeling capabilities for capillary flows and supplements the standard Richards equation representation. The governing equation for draining foam (or a soil variant termed the soil foam drainage equation – SFDE) obviates the need for macroscopic unsaturated hydraulic conductivity function by an explicit account of diminishing flow pathway sizes as the medium gradually drains. The study provides new and simple analytical expressions for drainage rates and volumes from unsaturated porous media subjected to different boundary conditions. Two novel analytical solutions for saturation profile evolution were derived and tested in good agreement with a numerical solution of the SFDE. The study and the proposed solutions rectify the original formulation of foam drainage dynamics of Or and Assouline [2013]. The new framework broadens the scope of methods available for quantifying unsaturated flow in porous media, where the intrinsic conductivity and geometrical representation of capillary drainage could improve understanding of colloid and pathogen transport. The explicit geometrical interpretation of flow pathways underlying the hydraulic functions used by the Richards equation offers new insights that benefit both approaches.
      PubDate: 2017-06-19T16:46:20.09647-05:0
      DOI: 10.1002/2017WR020361
       
  • Quantifying the distribution of tracer discharge from boreal catchments
           under transient flow using the kinematic pathway approach
    • Authors: S. S. Soltani; V. Cvetkovic
      Abstract: This focuses on solute discharge from boreal catchments with relatively shallow groundwater table and topography-driven groundwater flow. We explore whether a simplified semi-analytical approach can be used for predictive modeling of the statistical distribution of tracer discharge. The approach is referred to as the ‘kinematic pathways approach‘(KPA). This approach uses hydrological and tracer inputs, and topographical and hydrogeological information; the latter regards average aquifer depth to the less permeable bedrock. A characteristic velocity of water flow through the catchment is further obtained from the overall water balance in the catchment. For the waterborne tracer transport through the catchment, morphological dispersion is accounted for by topographical analysis of the distribution of pathway lengths to the catchment outlet. Macro-dispersion is accounted for heuristically by assuming an effective Péclet number. Distribution of water travel times through the catchment reflect the dispersion on both levels and are derived in both a forward mode (transit time from input to outlet) and a backward mode (water age when arriving at outlet arrival). The forward distribution of water travel times is further used for the tracer discharge modeling by convolution. The approach is applied to modeling of a 23 year long chloride data series for a specific catchment Kringlan (Sweden), and for generic modeling to better understand the dependence of the tracer discharge distribution on different dispersion aspects. The KPA is found to provide reasonable estimates of tracer discharge distribution, and particularly of extreme values, depending on method for determining the pathway length distribution. As a possible alternative analytical model of tracer transport through a catchment, the reservoir approach generally results in large tracer dispersion. This implies that tracer discharge distributions obtained from a mixed reservoir approach and from KPA are only compatible under large dispersion conditions.
      PubDate: 2017-06-19T16:46:12.596101-05:
      DOI: 10.1002/2016WR020326
       
  • Residence time-based classification of surface water systems
    • Authors: Allan E. Jones; Ben R. Hodges, James W. McClelland, Amber K. Hardison, Kevan B. Moffett
      Abstract: Defining surface water systems as lentic or lotic is an important first step in linking hydrology and ecology. Existing approaches for classifying surface water as lentic (reservoir-like) or lotic (river-like) use qualitative observations, solitary snapshot measurements in time and space, or ecologic metrics that are not broadly repeatable. This study introduces the Freshwater Continuum Classification (FCC), a quantitative method to consistently and objectively classify lentic/lotic systems based on integrated residence time (iTR), the time incoming water would take to exit the system given observed temporal variations in the system's discharge and volume. Lentic/lotic classification is determined from comparison of median iTR with critical flow thresholds related to key timescales such as zooplankton generation. Some systems switch between lentic and lotic behaviors over time, which are additionally defined in the FCC as oscillic. Pilot application of the FCC to 15 tidally-influenced river segments along the Texas Gulf Coast produced good agreement with previous methods of determining lentic/lotic character. The FCC defined 8 of 15 tidal reaches as primarily lentic, 6 as intermediate, and 1 as lotic between October 2007 and March 2015. Of the 15 reaches, 9 were also oscillic, characterized in this climate by short-lived lotic character during flash floods. The FCC provides a broadly applicable, repeatable, quantitative method to classify surface water bodies as lentic/intermediate/lotic and oscillic/non-oscillic regardless of size or nature (e.g., river or reservoir) based on system volume and flow characteristics.
      PubDate: 2017-06-19T16:46:03.410343-05:
      DOI: 10.1002/2016WR019928
       
  • Radial solute transport in highly heterogeneous aquifers: Modeling and
           experimental comparison
    • Authors: Mariaines Di Dato; Aldo Fiori, Felipe P. J. de Barros, Alberto Bellin
      Abstract: We analyze solute transport in a radially converging 3-D flow field in a porous medium with spatially heterogeneous hydraulic conductivity (K). The aim of the paper is to analyze the impact of heterogeneity and the mode of injection on BreakThrough Curves (BTCs) detected at a well pumping a contaminated aquifer. The aquifer is conceptualized as an ensemble of blocks of uniform but contrasting K and the analysis makes use of the travel time approach. Despite the approximations introduced, the model reproduces a laboratory experiment without calibration of transport parameters. Our results also show excellent agreement with numerical simulations for different levels of heterogeneity. We focus on the impact on the BTC of both heterogeneity in K and solute release conditions. It is shown that the injection mode matters, and the differences in the BTCs between uniform and flux proportional injection increase with the heterogeneity of the K-field. Furthermore, we study the effect of heterogeneity and mode of injection on early and late arrivals at the well.
      PubDate: 2017-06-19T16:45:58.619054-05:
      DOI: 10.1002/2016WR020039
       
  • Fracturing-induced release of radiogenic 4He and 234U into groundwater
           during the last deglaciation: An alternative source to crustal helium
           fluxes in periglacial aquifers
    • Authors: Pauline Méjean; Daniele L. Pinti, Bassam Ghaleb, Marie Larocque
      Abstract: External 4He sources have been invoked to explain 4He concentrations in groundwater greater than those expected from in situ U and Th production. In a fractured aquifer of Ordovician age located in the St. Lawrence Lowlands (Quebec, Canada), 4He concentrations of up to 4.48 x 10−5 cm3 STP gH20-1 were measured. Such concentrations are ca. 1000 times higher than would be expected from in situ production. A concomitant increase in 4He concentration and 234U/238U activity ratio is shown, suggesting a common release process in groundwater for 234U and 4He. This process has tentatively been identified as glaciation-induced rock fracturing following the Laurentide Ice Sheet retreat. The resulting increase in exposed grain surface facilitates 234U release by α-recoil, and that of radiogenic 4He by diffusion. Using a model of helium diffusion from a spherical grain, it is shown that rock fracturing facilitated the release of accumulated 4He at rates ranging from 4.2 x 10−10 cm3STP gH20-1 yr−1 to 1.06 x 10−8 cm3STP gH20-1 yr−1. These release rates are between 1,000 and 30,000 times higher than the local U and Th steady-state production rate, of 3.5±1.4 x 10−13 cm3STP grock-1 yr−1. Integration of 4He release rates over time yields a radiogenic 4He concentration of between 3.85 x 10−6 cm3STP gH20-1 and 7.12x 10−5 cm3STP gH20-1, in the range of concentrations measured in the St. Lawrence Lowlands fractured aquifers. Results support the occurrence of a local radiogenic helium source to explain the excesses measured in groundwater without requiring a significant external He crustal flux.
      PubDate: 2017-06-19T16:25:27.247488-05:
      DOI: 10.1002/2016WR020014
       
  • Fine particle retention within stream storage areas at baseflow and in
           response to a storm event
    • Authors: J. D. Drummond; L. G. Larsen, R. González-Pinzón, A. I. Packman, J. W. Harvey
      Abstract: Fine particles (1-100 µm), including particulate organic carbon (POC) and fine sediment, influence stream ecological functioning because they may contain or have a high affinity to sorb nitrogen and phosphorus. These particles are immobilized within stream storage areas, especially hyporheic sediments and benthic biofilms. However, fine particles are also known to remobilize under all flow conditions. This combination of downstream transport and transient retention, influenced by stream geomorphology, controls the distribution of residence times over which fine particles influence stream ecosystems. The main objective of this study was to quantify immobilization and remobilization rates of fine particles in a third-order sand-and-gravel bed stream (Difficult Run, Virginia, USA) within different geomorphic units of the stream (i.e., pool, lateral cavity, thalweg). During our field injection experiment, a thunderstorm-driven spate allowed us to observe fine particle dynamics during both baseflow and in response to increased flow. Solute and fine particles were measured within stream surface waters, porewaters, sediment cores, and biofilms on cobbles. Measurements were taken at four different subsurface locations with varying geomorphology and at multiple depths. Approximately 68% of injected fine particles were retained during baseflow until the onset of the spate. Retention was evident even after the spate, with 15.4% of the baseflow-deposited fine particles retained within benthic biofilms on cobbles and 14.9% within hyporheic sediment after the spate. Thus, through the combination of short-term remobilization and long-term retention, fine particles can serve as sources of carbon and nutrients to downstream ecosystems over a range of timescales.
      PubDate: 2017-06-16T05:40:59.488498-05:
      DOI: 10.1002/2016WR020202
       
  • Impact of spatially correlated pore-scale heterogeneity on drying porous
           media
    • Authors: Oshri Borgman; Paolo Fantinel, Wieland Lühder, Lucas Goehring, Ran Holtzman
      Abstract: We study the effect of spatially-correlated heterogeneity on isothermal drying of porous media. We combine a minimal pore-scale model with microfluidic experiments with the same pore geometry. Our simulated drying behavior compare favorably with experiments, considering the large sensitivity of the emergent behavior to the uncertainty associated with even small manufacturing errors. We show that increasing the correlation length in particle sizes promotes preferential drying of clusters of large pores, prolonging liquid connectivity and surface wetness and thus higher drying rates for longer periods. Our findings improve our quantitative understanding of how pore-scale heterogeneity impacts drying, which plays a role in a wide range of processes ranging from fuel cells to curing of paints and cements to global budgets of energy, water and solutes in soils.
      PubDate: 2017-06-16T05:40:52.219906-05:
      DOI: 10.1002/2016WR020260
       
  • Steady-State Supercritical CO2 and Brine Relative Permeability in Berea
           Sandstone at Different Temperature and Pressure Conditionsa
    • Authors: Xiongyu Chen; Shuang Gao, Amir Kianinejad, David A. DiCarlo
      Abstract: We measure steady-state two-phase supercritical CO2-brine relative permeabilities in a 61-cm-long Berea sandstone core at three different conditions (40°C and 12.41 MPa, 40°C and 8.27 MPa, and 60°C and 12.41 MPa) under primary drainage. We use pressure taps to obtain pressure drops of individual sections of the core, and X-ray Computed Tomography (CT) to obtain in situ saturation profiles, which together help to mitigate the capillary end effect. We include previously measured relative permeabilities at 20°C and 10.34 MPa, and compare all the data using both an eye-test and a statistical test. We find no appreciable temperature and pressure dependence of CO2 relative permeability within 20-60°C and 8.27-12.41 MPa. We find slight changes in the brine relative permeability between supercritical CO2 conditions (40-60°C and 8.27-12.41 MPa) and the liquid CO2 condition (20°C and 10.34 MPa). The temperature and pressure independence of CO2 relative permeability has been previously recognized and reassured in this work using a capillary-effect-free method. This allows one to use a single CO2 relative permeability curve in modeling two-phase CO2 flow within 20-60°C and 8.27-12.41 MPa.
      PubDate: 2017-06-15T09:20:26.240344-05:
      DOI: 10.1002/2017WR020810
       
  • A binomial modeling approach for upscaling colloid transport under
           unfavorable conditions: Emergent prediction of extended tailing
    • Authors: Markus Hilpert; Anna Rasmuson, William P. Johnson
      Abstract: Colloid transport in saturated porous media is significantly influenced by colloidal interactions with grain surfaces. Near-surface fluid domain colloids experience relatively low fluid drag and relatively strong colloidal forces that slow their down-gradient translation relative to colloids in bulk fluid. Near surface fluid domain colloids may re-enter into the bulk fluid via diffusion (nanoparticles) or expulsion at rear flow stagnation zones, they may immobilize (attach) via primary minimum interactions, or they may move along a grain-to-grain contact to the near surface fluid domain of an adjacent grain. We introduce a simple model that accounts for all possible permutations of mass transfer within a dual pore and grain network. The primary phenomena thereby represented in the model are mass transfer of colloids between the bulk and near-surface fluid domains and immobilization. Colloid movement is described by a Markov chain, i.e., a sequence of trials in a 1D network of unit cells, which contain a pore and a grain. Using combinatorial analysis, which utilizes the binomial coefficient, we derive the residence time distribution, i.e., an inventory of the discrete colloid travel times through the network and of their probabilities to occur. To parameterize the network model, we performed mechanistic pore-scale simulations in a single unit cell that determined the likelihoods and timescales associated with the above colloid mass transfer processes. We found that inter-grain transport of colloids in the near surface fluid domain can cause extended tailing, which has traditionally been attributed to hydrodynamic dispersion emanating from flow tortuosity of solute trajectories.
      PubDate: 2017-06-15T09:20:20.513892-05:
      DOI: 10.1002/2016WR020123
       
  • Water and growth: An econometric analysis of climate and policy impacts
    • Authors: Hassaan Furqan Khan; Bernard J Morzuch, Casey M Brown
      Abstract: Water-related hazards such as floods, droughts and disease cause damage to an economy through the destruction of physical capital including property and infrastructure, the loss of human capital and the interruption of economic activities, like trade and education. The question for policy makers is whether the impacts of water-related risk accrue to manifest as a drag on economic growth at a scale suggesting policy intervention. In this study, the average drag on economic growth from water-related hazards faced by society at a global level is estimated. We use panel regressions with various specifications to investigate the relationship between economic growth and hydroclimatic variables at the country-river basin level. In doing so, we make use of surface water runoff variables never used before. The analysis of the climate variables shows that water availability and water hazards have significant effects on economic growth, providing further evidence beyond earlier studies finding that precipitation extremes were at least as important or likely more important than temperature effects. We then incorporate a broad set of variables representing the areas of infrastructure, institutions and information to identify the characteristics of a region that determine its vulnerability to water-related risks. The results identify water scarcity, governance and agricultural intensity as the most relevant measures affecting vulnerabilities to climate variability effects.
      PubDate: 2017-06-14T12:45:36.937331-05:
      DOI: 10.1002/2016WR020054
       
  • Mutiscale pore structure and its effect on gas transport in organic-rich
           shale
    • Authors: Tianhao Wu; Xiang Li, Junliang Zhao, Dongxiao Zhang
      Abstract: A systematic investigation of multiscale pore structure in organic-rich shale by means of the combination of various imaging techniques is presented, including the state-of-the-art Helium-Ion-Microscope (HIM). The study achieves insight into the major features at each scale and suggests the affordable techniques for specific objectives from the aspects of resolution, dimension and cost. The pores, which appear to be isolated, are connected by smaller pores resolved by higher resolution imaging. This observation provides valuable information, from the microscopic perspective of pore structure, for understanding how gas accumulates and transports from where it is generated. A comprehensive workflow is proposed based on the characteristics acquired from the multiscale pore structure analysis to simulate the gas transport process. The simulations are completed with three levels: the microscopic mechanisms should be taken into consideration at level I; the spatial distribution features of organic matter, inorganic matter, and macropores constitute the major issue at level II; and the micro-fracture orientation and topological structure are dominant factors at level III. The results of apparent permeability from simulations agree well with the values acquired from experiments. By means of the workflow, the impact of various gas transport mechanisms at different scales can be investigated more individually and precisely than conventional experiments.
      PubDate: 2017-06-14T12:45:35.892598-05:
      DOI: 10.1002/2017WR020780
       
  • Earthworms and tree roots: A model study of the effect of preferential
           flow paths on runoff generation and groundwater recharge in steep,
           saprolitic, tropical lowland catchments
    • Authors: Yanyan Cheng; Fred L. Ogden, Jianting Zhu
      Abstract: Preferential flow paths (PFPs) affect the hydrological response of humid tropical catchments but have not received sufficient attention. We consider PFPs created by tree roots and earthworms in a near-surface soil layer in steep, humid, tropical lowland catchments and hypothesize that observed hydrological behaviors can be better captured by reasonably considering PFPs in this layer. We test this hypothesis by evaluating the performance of four different physically-based distributed model structures without and with PFPs in different configurations. Model structures are tested both quantitatively and qualitatively using hydrological, geophysical, and geochemical data both from the Smithsonian Tropical Research Institute, Agua Salud Project experimental catchment(s) in central Panama and other sources in the literature. The performance of different model structures is evaluated using runoff volume error and three Nash-Sutcliffe efficiency measures against observed total runoff, storm- and baseflows along with visual comparison of simulated and observed hydrographs. Two of the four proposed model structures which include both lateral and vertical PFPs are plausible, but the one with explicit simulation of PFPs performs the best. A small number of vertical PFPs that fully extend below the root zone allow the model to reasonably simulate deep groundwater recharge, which plays a crucial role in baseflow generation. Results also show that the shallow lateral PFPs are the main contributor to the observed high flow characteristics. Their number and size distribution are found to be more important than the depth distribution. Our model results are corroborated by geochemical and geophysical observations.
      PubDate: 2017-06-14T12:45:31.481261-05:
      DOI: 10.1002/2016WR020258
       
  • How uncertainty analysis of streamflow data can reduce costs and promote
           robust decisions in water management applications
    • Authors: Hilary McMillan; Jan Seibert, Asgeir Petersen-Overleir, Michel Lang, Paul White, Ton Snelder, Kit Rutherford, Tobias Krueger, Robert Mason, Julie Kiang
      Abstract: Streamflow data are used for important environmental and economic decisions, such as specifying and regulating minimum flows, managing water supplies, and planning for flood hazards. Despite significant uncertainty in most flow data, the flow series for these applications are often communicated and used without uncertainty information. In this commentary, we argue that proper analysis of uncertainty in river flow data can reduce costs and promote robust conclusions in water management applications. We substantiate our argument by providing case studies from Norway and New Zealand where streamflow uncertainty analysis has uncovered economic costs in the hydropower industry, improved public acceptance of a controversial water management policy, and tested the accuracy of water quality trends. We discuss the need for practical uncertainty assessment tools that generate multiple flow series realizations rather than simple error bounds. Although examples of such tools are in development, considerable barriers for uncertainty analysis and communication still exist for practitioners, and future research must aim to provide easier access and usability of uncertainty estimates. We conclude that flow uncertainty analysis is critical for good water management decisions.
      PubDate: 2017-06-14T12:45:29.792919-05:
      DOI: 10.1002/2016WR020328
       
  • Patterns of glacier ablation across North-Central Chile: Identifying the
           limits of empirical melt models under sublimation-favorable conditions
    • Authors: A. Ayala; F. Pellicciotti, S. MacDonell, J. McPhee, P. Burlando
      Abstract: We investigate the energy balance and ablation regimes of glaciers in high-elevation, dry environments using glacio-meteorological data collected on six glaciers in the semiarid Andes of North-Central Chile (29-34°S, 3127-5324 m). We use a point-scale physically-based energy balance (EB) model and an enhanced Temperature-Index (ETI) model that calculates melt rates only as a function of air temperature and net shortwave radiation. At all sites, the largest energy inputs are net shortwave and incoming longwave radiation, which are controlled by surface albedo and elevation, respectively. Turbulent fluxes cancel each other out at the lower sites, but as elevation increases, cold, dry and wind-exposed conditions increase the magnitude of negative latent heat fluxes, associated with large surface sublimation rates. In midsummer (January), ablation rates vary from 67.9 mm w.e. d−1 at the lowest site (∼100% corresponding to melt), to 2.3 mm w.e. d−1 at the highest site (>85% corresponding to surface sublimation). At low-elevation, low-albedo, melt-dominated sites, the ETI model correctly reproduces melt using a large range of possible parameters, but both the performance and parameter transferability decrease with elevation for two main reasons: i) the air temperature threshold approach for melt onset does not capture the diurnal variability of melt in cold and strong irradiated environments and ii) energy losses decrease the correlation between melt and net shortwave radiation. We summarize our results by means of an elevation profile of ablation components that can be used as reference in future studies of glacier ablation in the semiarid Andes.
      PubDate: 2017-06-14T12:45:28.407617-05:
      DOI: 10.1002/2016WR020126
       
  • Pore-scale water dynamics during drying and the impacts of structure and
           surface wettability
    • Authors: Brian C. Cruz; Jessica M. Furrer, Yi-Syuan Guo, Daniel Dougherty, Hector F. Hinestroza, Jhoan S. Hernandez, Daniel J. Gage, Yong Ku Cho, Leslie M. Shor
      Abstract: Plants and microbes secrete mucilage into soil during dry conditions, which can alter soil structure and increase contact angle. Structured soils exhibit a broad pore size distribution with many small and many large pores, and strong capillary forces in narrow pores can retain moisture in soil aggregates. Meanwhile, contact angle determines the water repellency of soils, which can result in suppressed evaporation rates. Although they are often studied independently, both structure and contact angle influence water movement, distribution, and retention in soils. Here, drying experiments were conducted using soil micromodels patterned to emulate different aggregation states of a sandy loam soil. Micromodels were treated to exhibit contact angles representative of those in bulk soil (8.4° ± 1.9°) and the rhizosphere (65° ± 9.2°). Drying was simulated using a lattice Boltzmann single component, multi-phase model. In our experiments, micromodels with higher contact angle surfaces took four times longer to completely dry versus micromodels with lower contact angle surfaces. Microstructure influenced drying rate as a function of saturation and controlled the spatial distribution of moisture within micromodels. Lattice Boltzmann simulations accurately predicted pore scale moisture retention patterns within micromodels with different structures and contact angles.
      PubDate: 2017-06-14T12:45:24.737953-05:
      DOI: 10.1002/2016WR019862
       
  • How Jordan and Saudi Arabia are avoiding a tragedy of the commons over
           shared groundwater
    • Authors: Marc F. Müller; Michèle C. Müller-Itten, Steven M. Gorelick
      Abstract: Transboundary aquifers are ubiquitous and strategically important to global food and water security. Yet these shared resources are being depleted at an alarming rate. Focusing on the Disi aquifer, a key non-renewable source of groundwater shared by Jordan and Saudi Arabia, this study develops a two-stage game with incomplete that evaluates optimal transboundary strategies of common-pool resource exploitation under various assumptions. The analysis relies on estimates of agricultural water use from satellite imagery, which were obtained using three independent remote sensing approaches. Drawdown response to pumping is simulated using a 2D regional aquifer model. Jordan and Saudi Arabia developed a buffer-zone strategy with a prescribed minimum distance between each country's pumping centers. We show that by limiting the marginal impact of pumping decisions on the other country's pumping costs, this strategy will likely avoid an impeding tragedy of the commons for at least 60 years. Our analysis underscores the role played by distance between wells and disparities in groundwater exploitation costs on common-pool overdraft. In effect, if pumping centers are distant enough, a shared aquifer no longer behaves as a common-pool resource and a tragedy of the commons can be avoided. The 2015 Disi aquifer pumping agreement between Jordan and Saudi Arabia, which in practice relies on a joint technical commission to enforce exclusion zones, is the first agreement of this type between sovereign countries and has a promising potential to avoid conflicts or resolve potential transboundary groundwater disputes over comparable aquifer systems elsewhere.
      PubDate: 2017-06-14T12:45:21.556015-05:
      DOI: 10.1002/2016WR020261
       
  • Forest thinning impacts on the water balance of Sierra Nevada
           mixed-conifer headwater basins
    • Authors: P. C. Saksa; M. H. Conklin, J. J. Battles, C. L. Tague, R. C. Bales
      Abstract: Headwater catchments in the mixed-conifer zone of the American and Merced River basins were selectively thinned in 2012 to reduce the risk of high-intensity wildfire. Distributed observations of forest vegetation thinning, precipitation, snowpack storage, soil-water storage, energy balance and stream discharge from 2010 to 2013 were used to calculate the water balance and constrain a hydro-ecologic model. Using the spatially calibrated RHESSys model, we assessed thinning effects on the water balance. In the central-Sierra American River headwaters, there was a mean annual runoff increase of 14% in response to the observed thinning patterns, which included heterogeneous reductions in Leaf Area Index (-8%), canopy cover (-3%), and shrub cover (-4%). In the southern-Sierra Merced River headwaters, thinning had little impact on forest structure or runoff, as vegetation growth in areas not thinned offset reductions from thinning. Observed thinning effects on runoff could not be confirmed in either basin by measurements alone, in part because of the high variability in precipitation during the measurement period. Modeling results show that when thinning is intensive enough to change forest structure, low-magnitude vegetation reductions have greater potential to modify the catchment-scale water balance in the higher-precipitation central Sierra Nevada versus in the more water-limited southern Sierra Nevada. Hydrologic modeling, constrained by detailed, multi-year field measurements, provides a useful tool for analyzing catchment response to forest thinning.
      PubDate: 2017-06-14T12:45:19.536429-05:
      DOI: 10.1002/2016WR019240
       
  • The citation impact of hydrology journals
    • Authors: Martyn P. Clark; R. Brooks Hanson
      Abstract: We examine a suite of journal-level productivity and citation statistics for six leading hydrology journals in order to help authors understand the robustness and meaning of journal impact factors. The main results are (1) the probability distribution of citations is remarkably homogenous across hydrology journals; (2) hydrology papers tend to have a long-lasting impact, with a large fraction of papers cited after the 2 year window used to calculate the journal impact factor; and (3) journal impact factors are characterized by substantial year-to-year variability (especially for smaller journals), primarily because a small number of highly cited papers have a large influence on the journal impact factor. Consequently, the ranking of hydrology journals with respect to the journal impact factor in a given year does not have much information content. These results highlight problems in using citation data to evaluate hydrologic science. We hope that this analysis helps authors better understand journal-level citation statistics, and also helps improve research assessments in institutions and funding agencies.
      PubDate: 2017-06-13T09:00:01.02151-05:0
      DOI: 10.1002/2017WR021125
       
  • Evaluating topography-based predictions of shallow lateral groundwater
           discharge zones for a boreal lake–stream system
    • Authors: J. A. Leach; W. Lidberg, L. Kuglerová, A. Peralta-Tapia, A. Ågren, H. Laudon
      Abstract: Groundwater discharge along streams exerts an important influence on biogeochemistry and thermal regimes of aquatic ecosystems. A common approach for predicting locations of shallow lateral groundwater discharge is to use digital elevation models (DEMs) combined with upslope contributing area algorithms. We evaluated a topography-based prediction of subsurface discharge zones along a 1500 m headwater stream reach using temperature and water isotope tracers. We deployed fibre-optic distributed temperature sensing instrumentation to monitor stream temperature at 0.25 m intervals along the reach. We also collected samples of stream water for the analysis of its water isotope composition at 50 m intervals on five occasions representing distinct streamflow conditions before, during and after a major rain event. The combined tracer evaluation showed that topography-predicted locations of groundwater discharge were generally accurate; however, predicted magnitude of groundwater inflows estimated from upslope contributing area did not always agree with tracer estimates. At the catchment scale, lateral inflows were an important source of streamflow at baseflow and peak flow during a major rain event; however, water from a headwater lake was the dominant water source during the event hydrograph recession. Overall, this study highlights potential utility and limitations of predicting locations and contributions of lateral groundwater discharge zones using topography-based approaches in humid boreal regions.
      PubDate: 2017-06-09T09:50:34.478984-05:
      DOI: 10.1002/2016WR019804
       
  • High-frequency dissolved organic carbon and nitrate measurements reveal
           differences in storm hysteresis and loading in relation to land cover and
           seasonality
    • Authors: M. C. H. Vaughan; W. B. Bowden, J. B. Shanley, A. Vermilyea, R. Sleeper, A. J. Gold, S. Pradhanang, S. P. Inamdar, D. F. Levia, A. S. Andres, F. Birgand, A. W. Schroth
      Abstract: Storm events dominate riverine loads of dissolved organic carbon (DOC) and nitrate, and are expected to increase in frequency and intensity in many regions due to climate change. We deployed three high-frequency (15-minute) in-situ absorbance spectrophotometers to monitor DOC and nitrate concentration for 126 storms in three watersheds with agricultural, urban, and forested land use/land cover. We examined intrastorm hysteresis and the influences of seasonality, antecedent conditions, storm size, and dominant land use/land cover on storm DOC and nitrate loads. DOC hysteresis was generally anti-clockwise at all sites, indicating distal and plentiful sources for all three streams despite varied DOC character and sources. Nitrate hysteresis was generally clockwise for urban and forested sites, but anti-clockwise for the agricultural site, indicating an exhaustible, proximal source of nitrate in the urban and forested sites, and more distal and plentiful sources of nitrate in the agricultural site. The agricultural site had significantly higher storm nitrate yield per water yield and higher storm DOC yield per water yield than the urban or forested sites. Seasonal effects were important for storm nitrate yield in all three watersheds and farm management practices likely caused complex interactions with seasonality at the agricultural site. Hysteresis indices did not improve predictions of storm nitrate yields at any site. We discuss key lessons from using high-frequency in-situ optical sensors.
      PubDate: 2017-06-09T09:50:31.617115-05:
      DOI: 10.1002/2017WR020491
       
  • Effect of sampling time in the laboratory investigation of braided rivers
    • Authors: R. Vesipa; C. Camporeale, L. Ridolfi
      Abstract: We focus on the measurement of the bed-elevation of braided-networks in flume experiments. In particular, the effect of the survey frequency on the measurement accuracy is studied. To this aim, an innovative measurement system is adopted. It consists of a laser-ultrasonic sensor and can survey the bed elevation under owing water. This measurement system was used to profile a flume transect with a frequency of 4 minutes, without stopping the water discharge.By this technique, the topography of a single transect was continuously acquired during the evolution of a braided river model. Twelve braided rivers generated with different experimental conditions were studied.The main results are: (i) there exists a threshold survey-frequency (4-8 minutes in our analysis) which guarantees that the morphological evolution of the braiding channels is fully measured; (ii) if this threshold frequency of survey is exceeded, significant errors occur in the balance of the eroded/deposited sediments and in the evaluation of the bed-elevation dynamics; and (iii) these errors depend on the river stream-power.
      PubDate: 2017-06-09T09:50:28.794377-05:
      DOI: 10.1002/2017WR020474
       
  • Investigating water use over the Choptank River Watershed using a
           multisatellite data fusion approach
    • Authors: Liang Sun; Martha C. Anderson, Feng Gao, Christopher Hain, Joseph G. Alfieri, Amirreza Sharifi, Gregory W. McCarty, Yun Yang, Yang Yang, William P. Kustas, Lynn McKee
      Abstract: The health of the Chesapeake Bay ecosystem has been declining for several decades due to high levels of nutrients and sediments largely tied to agricultural production systems. Therefore, monitoring of agricultural water use and hydrologic connections between crop lands and Bay tributaries has received increasing attention. Remote sensing retrievals of actual evapotranspiration (ET) can provide valuable information in support of these hydrologic modeling efforts, spatially and temporally describing consumptive water use by crops and natural vegetation and quantifying response to expansion of irrigated area occurring with Bay watershed. In this study, a multi-sensor satellite data fusion methodology, combined with a multi-scale ET retrieval algorithm, was applied over the Choptank River watershed located within the Lower Chesapeake Bay region on the Eastern Shore of Maryland, USA to produce daily 30-m resolution ET maps. ET estimates directly retrieved on Landsat satellite overpass dates have high accuracy with relative error (RE) of 9%, as evaluated using flux tower measurements. The fused daily ET time series have reasonable errors of 18% at the daily time step - an improvement from 27% errors using standard Landsat-only interpolation techniques. Annual water consumption by different land cover types was assessed, showing reasonable distributions of water use with cover class. Seasonal patterns in modeled crop transpiration and soil evaporation for dominant crop types were analyzed, and agree well with crop phenology at field scale. Additionally, effects of irrigation occurring during a period of rainfall shortage were captured by the fusion program. These results suggest that the ET fusion system will have utility for water management at field and regional scales over the Eastern Shore. Further efforts are underway to integrate these detailed water use datasets into watershed-scale hydrologic models to improve assessments of water quality and inform best management practices to reduce nutrient and sediment loads to the Chesapeake Bay.
      PubDate: 2017-06-09T09:50:27.080051-05:
      DOI: 10.1002/2017WR020700
       
  • Near-surface turbulence as a missing link in modeling
           evapotranspiration-soil moisture relationships
    • Authors: Erfan Haghighi; James W. Kirchner
      Abstract: Despite many efforts to develop evapotranspiration (ET) models with improved parametrizations of resistance terms for water vapor transfer into the atmosphere, estimates of ET and its partitioning remain prone to bias. Much of this bias could arise from inadequate representations of physical interactions near non-uniform surfaces from which localized heat and water vapor fluxes emanate. This study aims to provide a mechanistic bridge from land-surface characteristics to vertical transport predictions, and proposes a new physically based ET model that builds on a recently developed bluff-rough bare soil evaporation model incorporating coupled soil moisture-atmospheric controls. The newly developed ET model explicitly accounts for (1) near-surface turbulent interactions affecting soil drying and (2) soil-moisture-dependent stomatal responses to atmospheric evaporative demand that influence leaf (and canopy) transpiration. Model estimates of ET and its partitioning were in good agreement with available field-scale data, and highlight hidden processes not accounted for by commonly used ET schemes. One such process, nonlinear vegetation-induced turbulence (as a function of vegetation stature and cover fraction) significantly influences ET-soil moisture relationships. Our results are particularly important for water resources and land use planning of semiarid sparsely vegetated ecosystems where soil surface interactions are known to play a critical role in land-climate interactions. This study potentially facilitates a mathematically tractable description of the strength (i.e., the slope) of the ET-soil moisture relationship, which is a core component of models that seek to predict land-atmosphere coupling and its feedback to the climate system in a changing climate.
      PubDate: 2017-06-09T09:50:20.764662-05:
      DOI: 10.1002/2016WR020111
       
  • Synthetic fracture network characterization with transdimensional
           inversion
    • Authors: Márk Somogyvári; Mohammadreza Jalali, Santos Jimenez Parras, Peter Bayer
      Abstract: Fracture network geometry is crucial for transport in hard rock aquifers, but it can only be approximated in models. While fracture orientation, spacing and intensity can be obtained from borehole logs, core images and outcrops, the characterization of in-situ fracture network geometry requires the interpretation of spatially distributed hydraulic and transport experiments. In this study we present a novel concept using a transdimensional inversion method (reversible jump Markov Chain Monte Carlo, rjMCMC) to invert a two-dimensional cross-well discrete fracture network (DFN) geometry from tracer tomography experiments. The conservative tracer transport is modelled via a fast finite difference model neglecting matrix diffusion. The proposed DFN inversion method iteratively evolves DFN variants by geometry updates to fit the observed tomographic data evaluated by the Metropolis-Hastings-Green acceptance criteria. A main feature is the varying dimensions of the inverse problem, which allows for the calibration of fracture geometries and numbers. This delivers an ensemble of thousands of DFN realizations that can be utilized for probabilistic identification of fractures in the aquifer. In the presented hypothetical and outcrop-based case studies, cross-sections between boreholes are investigated. The procedure successfully identifies major transport pathways in the investigated domain and explores equally probable DFN realizations, which are analyzed in fracture probability maps and by multidimensional scaling.
      PubDate: 2017-06-07T09:50:34.93269-05:0
      DOI: 10.1002/2016WR020293
       
  • A spatial Markov model for the evolution of the joint distribution of
           groundwater age, arrival time, and velocity in heterogeneous media
    • Authors: Arash Massoudieh; Marco Dentz, Jamal Alikhani
      Abstract: The evolution of the joint distribution of groundwater age, velocity and arrival times based on a Markov model for the velocities of fluid particles in heterogeneous porous media has been quantified. An explicit evolution equation for the joint distribution of age, arrival time and particle velocity is derived, which is equivalent to a continuous time random walk for age, velocity and arrival time. The approach is fully parameterized by the correlation model and the distribution of groundwater flow velocities. The transition probability for subsequent particle velocities along streamlines is implemented by a Copula, which is an efficient method to generate a correlated velocity series with prescribed marginal distribution. We discuss different solution methods based on finite-differences and random walk particle tracking. The latter is based on continuous time random walks, whose transition times are obtained kinematically from the flow velocities. Specifically, we discuss a renormalization scheme to accelerate the particle tracking simulations based on the definition of aggregate particle transitions while at the same time renormalizing velocity correlation. The impact of velocity correlation and velocity distribution on the evolution of age at different distances from the inlet plane is also studied. At distances of the order of the correlation length, persistent particle velocities give the same behavior as stochastic streamtube models. For velocity distributions which give rise to transition times with finite variance, the age distributions evolve towards an inverse Gaussian. For heavy-tailed weighting times, they evolve towards stable distribution as the distance from the inlet increases.
      PubDate: 2017-06-07T09:50:33.235098-05:
      DOI: 10.1002/2017WR020578
       
  • Role of air-water interfaces in colloid transport in porous media: A
           review
    • Authors: Markus Flury; Surachet Aramrak
      Abstract: Air-water interfaces play an important role in unsaturated porous media, giving rise to phenomena like capillarity. Less recognized and understood are interactions of colloids with the air-water interface in porous media and the implications of these interactions for fate and transport of colloids. In this review, we discuss how colloids, both suspended in the aqueous phase and attached at pore walls, interact with air-water interfaces in porous media. We discuss the theory of colloid/air-water interface interactions, based on the different forces acting between colloids and the air-water interface (DLVO, hydrophobic, capillary forces) and based on thermodynamic considerations (Gibbs free energy). Subsurface colloids are usually electrostatically repelled from the air-water interface because most subsurface colloids and the air-water are negatively charged. However, hydrophobic interactions can lead to attraction to the air-water interface. When colloids are at the air-water interface, capillary forces are usually dominant over other forces. Moving air-water interfaces are effective in mobilizing and transporting colloids from surfaces. Thermodynamic considerations show that, for a colloid, the air-water interface is the favored state as compared with the suspension phase, except for hydrophilic colloids in the nanometer size range. Experimental evidence indicates that colloid mobilization in soils often occurs through macropores, although matrix transport is also prevalent in absence of macropores. Moving air-water interfaces, e.g., occurring during infiltration, imbibition, or drainage, have been shown to scour colloids from surfaces and translocate colloids. Colloids can also be pinned to surfaces by thin water films and capillary menisci at the air-water-solid interface line, causing colloid retention and immobilization. Air-water interfaces thus can both mobilize or immobilize colloids in porous media, depending on hydrodynamics and colloid and surface chemistry.
      PubDate: 2017-06-07T09:50:30.769993-05:
      DOI: 10.1002/2017WR020597
       
  • Development of a land surface model with coupled snow and frozen soil
           physics
    • Authors: Lei Wang; Jing Zhou, Jia Qi, Litao Sun, Kun Yang, Lide Tian, Yanluan Lin, Wenbin Liu, Maheswor Shrestha, Yongkang Xue, Toshio Koike, Yaoming Ma, Xiuping Li, Yingying Chen, Deliang Chen, Shilong Piao, Hui Lu
      Abstract: Snow and frozen soil are important factors that influence terrestrial water and energy balances through snowpack accumulation and melt and soil freeze-thaw. In this study, a new land surface model (LSM) with coupled snow and frozen soil physics was developed based on a hydrologically improved LSM (HydroSiB2). First, an energy-balance-based 3-layer snow model was incorporated into HydroSiB2 (hereafter HydroSiB2-S) to provide an improved description of the internal processes of the snow pack. Second, a universal and simplified soil model was coupled with HydroSiB2-S to depict soil water freezing and thawing (hereafter HydroSiB2-SF). In order to avoid the instability caused by the uncertainty in estimating water phase changes, enthalpy was adopted as a prognostic variable instead of snow/soil temperature in the energy balance equation of the snow/frozen soil module. The newly developed models were then carefully evaluated at two typical sites of the Tibetan Plateau (TP) (one snow-covered and the other snow-free, both with underlying frozen soil). At the snow-covered site in northeastern TP (DY), HydroSiB2-SF demonstrated significant improvements over HydroSiB2-F (same as HydroSiB2-SF but using the original single-layer snow module of HydroSiB2), showing the importance of snow internal processes in 3-layer snow parameterization. At the snow-free site in southwestern TP (Ngari), HydroSiB2-SF reasonably simulated soil water phase changes while HydroSiB2-S did not, indicating the crucial role of frozen soil parameterization in depicting the soil thermal and water dynamics. Finally, HydroSiB2-SF proved to be capable of simulating upward moisture fluxes towards the freezing front from the underlying soil layers in winter.
      PubDate: 2017-06-07T09:50:27.108646-05:
      DOI: 10.1002/2017WR020451
       
  • Application of analytical diffusion models to outcrop observations:
           Implications for mass transport by fluid flow through fractures
    • Authors: M. Antonellini; P. N. Mollema, L. Del Sole
      Abstract: A pavement outcrop with excellent exposure of spatial relationships among joints, veins, small offset normal faults and associated alteration halos (redox fronts) provided an opportunity to compare predictions of analytical models for reaction front propagation in a fracture–matrix system with a real field situation. The results have important implications for fluid flow and pollutant transport through a fractured medium. The alteration halos observed suggest that all joints of different sets and most small faults are conductive to meteoric water at shallow depth. On the other hand, veins are local barriers to mass transport by diffusion. By using petrologic and petrophysical data, analytical modeling, and the width of the alteration halos, it was possible to estimate when the fracture network was open to fluid flow. The inferred time for fluid flow and diffusion through the fracture network is sensitive to the porosity n of the rock matrix used in the analytical solutions: 2200 ± 500 years with n = 0.08, 4600 ± 900 years with n = 0.05, and 16000 ± 4000 with n = 0.02. The second and third age determinations are consistent with the landscape evolution of the area since the end of the last Wűrmian ice age and with the timing required to fill the fractures observed in outcrop. We suggest that analytical modeling is an important tool for the determination of transport and reaction time scales in fractured formations where it is constrained by a robust petrophysical and chemical properties dataset.
      PubDate: 2017-06-07T09:50:25.250565-05:
      DOI: 10.1002/2016WR019864
       
  • Field validation of thermal tracer tomography for reconstruction of
           aquifer heterogeneity
    • Authors: Márk Somogyvári; Peter Bayer
      Abstract: In the summer of 2015, a series of thermal tracer tests were conducted at the Widen field site in northeast Switzerland to validate travel time-based thermal tracer tomography for reconstruction of aquifer heterogeneity. Repeated thermal tracer tests and distributed temperature observations were used to obtain a multi-source/multi-receiver tomographic experimental setup. After creating forced hydraulic gradient conditions, heated water was injected as a pulse temperature signal via a double packer system. With this solution, long temperature recovery periods were not required between the repeated injections at the expense of smaller observed temperatures. The recorded temperature breakthrough curves delivered a tomographic travel time dataset that was inverted assuming advection-dominated condition. The obtained hydraulic conductivity tomogram for a small aquifer profile is validated with the results of the findings from previous field investigations at the same site. The reconstructed profile confirms the presence of a thin sand layer with low-permeability, and reveals a previously unknown low-permeable zone close to the bottom of the aquifer. The inverted hydraulic conductivity values also correspond with those from previous tracer tests. Thus, the results of this study demonstrate the potential of thermal tracer tomography for resolving structures and transport characteristics of heterogeneous aquifers.
      PubDate: 2017-06-07T09:50:21.477629-05:
      DOI: 10.1002/2017WR020543
       
  • Appreciation of peer reviewers for 2016
    • Authors: Alberto Montanari; Jean Bahr, Günter Blöschl, Ximing Cai, D. Scott Mackay, Anna Michalak, Harihar Rajaram, Xavier Sanchez-Vila
      Abstract: On behalf of the journal, the American Geophysical Union, and the scientific community, the editors would like to sincerely thank those who reviewed manuscripts for Water Resources Research in 2016. Their time spent reading and commenting on manuscripts not only improves the manuscripts themselves but also increases the scientific rigor of future research in the field. Many of those listed below went above and beyond and reviewed three or more manuscripts for our journal, and those are indicated in italics. Together, they contributed 3674 individual reviews of manuscripts submitted to Water Resources Research for consideration, of which 562 were eventually published. Thank you again. We look forward to a 2017 of exciting advances in the field and communicating those advances to our community and to the broader public.
      PubDate: 2017-06-07T09:50:19.614438-05:
      DOI: 10.1002/2017WR021235
       
  • Modeling meander morphodynamics over self-formed heterogeneous floodplains
    • Authors: Manuel Bogoni; Mario Putti, Stefano Lanzoni
      Abstract: This work addresses the signatures embedded in the planform geometry of meandering rivers consequent to the formation of floodplain heterogeneities as the river bends migrate. Two geomorphic features are specifically considered: scroll bars produced by lateral accretion of point bars at convex banks and oxbow lake fills consequent to neck cutoffs. The sedimentary architecture of these geomorphic units depends on the type and amount of sediment, and controls bank erodibility as the river impinges on them, favoring or contrasting the river migration. The geometry of numerically generated planforms obtained for different scenarios of floodplain heterogeneity is compared to that of natural meandering paths. Half meander metrics and spatial distribution of channel curvatures are used to disclose the complexity embedded in meandering geometry. Fourier Analysis, Principal Component Analysis, Singular Spectrum Analysis and Multivariate Singular Spectrum Analysis are used to emphasize the subtle but crucial differences which may emerge between apparently similar configurations. A closer similarity between observed and simulated planforms is attained when fully coupling flow and sediment dynamics (fully-coupled models) and when considering self-formed heterogeneities that are less erodible than the surrounding floodplain.
      PubDate: 2017-06-02T07:25:34.607799-05:
      DOI: 10.1002/2017WR020726
       
  • Determination of hyporheic travel-time distributions and other parameters
           from concurrent conservative and reactive tracer tests by local-in-global
           optimization
    • Authors: Julia L.A. Knapp; Olaf A. Cirpka
      Abstract: The complexity of hyporheic flow paths requires reach-scale models of solute transport in streams that are flexible in their representation of the hyporheic passage. We use a model that couples advective-dispersive in-stream transport to hyporheic exchange with a shape-free distribution of hyporheic travel times. The model also accounts for two-site sorption and transformation of reactive solutes. The coefficients of the model are determined by fitting concurrent stream-tracer tests of conservative (fluorescein) and reactive (resazurin/resorufin) compounds. The flexibility of the shape-free models give rise to multiple local minima of the objective function in parameter estimation, thus requiring global-search algorithms, which is hindered by the large number of parameter values to be estimated. We present a local-in-global optimization approach, in which we use a Markov-Chain Monte Carlo method as global-search method to estimate a set of in-stream and hyporheic parameters. Nested therein, we infer the shape-free distribution of hyporheic travel times by a local Gauss-Newton method. The overall approach is independent of the initial guess and provides the joint posterior distribution of all parameters. We apply the described local-in-global optimization method to recorded tracer breakthrough curves of three consecutive stream sections, and infer section-wise hydraulic parameter distributions to analyze how hyporheic exchange processes differ between the stream sections.
      PubDate: 2017-06-02T07:20:53.460923-05:
      DOI: 10.1002/2017WR020734
       
  • Land-use change impacts on floods at the catchment scale – Challenges
           and opportunities for future research
    • Authors: M. Rogger; M. Agnoletti, A. Alaoui, J.C. Bathurst, G. Bodner, M. Borga, V. Chaplot, F. Gallart, G. Glatzel, J. Hall, J. Holden, L. Holko, R. Horn, A. Kiss, S. Kohnová, G. Leitinger, B. Lennartz, J. Parajka, R. Perdigão, S. Peth, L. Plavcová, J.N. Quinton, M. Robinson, J. L. Salinas, A. Santoro, J. Szolgay, S. Tron, J.J.H. van den Akker, A. Viglione, G. Blöschl
      Abstract: Research gaps in understanding flood changes at the catchment scale caused by changes in forest management, agricultural practices, artificial drainage and terracing are identified. Potential strategies in addressing these gaps are proposed, such as complex systems approaches to link processes across time scales, long-term experiments on physical-chemical-biological process interactions, and a focus on connectivity and patterns across spatial scales. It is suggested that these strategies will stimulate new research that coherently addresses the issues across hydrology, soil and agricultural sciences, forest engineering, forest ecology and geomorphology.
      PubDate: 2017-06-02T07:15:39.46577-05:0
      DOI: 10.1002/2017WR020723
       
  • Have Chinese water pricing reforms reduced urban residential water
           demand?
    • Authors: B. Zhang; K.H. Fang, K.A. Baerenklau
      Abstract: China continues to deal with severe levels of water scarcity and water pollution. To help address this situation, in 2002 the Chinese central government initiated urban water pricing reforms that emphasized the adoption of increasing block rate (IBR) price structures in place of existing uniform rate structures. ……By combining urban water use records with micro-level data from the Chinese Urban Household Survey, this research investigates the effectiveness of this national policy reform. Specifically, we compare the household water consumption in 28 cities that adopted IBR tariffs during 2002-2009, with that of 110 cities that had not yet done so. Based on difference-in-differences models, our results show that the policy reform reduced annual residential water demand by 3-4% in the short-run and 5% in the longer-term. These relatively modest reductions are consistent with the typically generous nature of the IBR tariffs that Chinese cities have chosen to implement, and imply that more efforts are needed to address China's persistent urban water scarcity challenges.
      PubDate: 2017-06-02T07:15:37.042271-05:
      DOI: 10.1002/2017WR020463
       
  • Confounding factors in determining causal soil moisture-precipitation
           feedback
    • Authors: S. E. Tuttle; G. D. Salvucci
      Abstract: Identification of causal links in the land-atmosphere system is important for construction and testing of land surface and general circulation models. However, the land and atmosphere are highly coupled and linked by a vast number of complex, interdependent processes. Statistical methods, such as Granger causality, can help to identify feedbacks from observational data, independent of the different parameterizations of physical processes and spatiotemporal resolution effects that influence feedbacks in models. However, statistical causal identification methods can easily be misapplied, leading to erroneous conclusions about feedback strength and sign. Here, we discuss three factors that must be accounted for in determination of causal soil moisture-precipitation feedback in observations and model output: seasonal and interannual variability, precipitation persistence, and endogeneity. The effect of neglecting these factors is demonstrated in simulated and observational data. The results show that long timescale variability and precipitation persistence can have a substantial effect on detected soil moisture-precipitation feedback strength, while endogeneity has a smaller effect that is often masked by measurement error and thus is more likely to be an issue when analyzing model data or highly accurate observational data.
      PubDate: 2017-06-02T07:15:33.779668-05:
      DOI: 10.1002/2016WR019869
       
  • Calculation of in situ acoustic sediment attenuation using off-the-shelf
           horizontal ADCPs in low concentration settings
    • Authors: Dan Haught; Jeremy G. Venditti, Scott Wright
      Abstract: The use of ‘off-the-shelf' acoustic Doppler velocity profilers (ADCPs) to estimate suspended sediment concentration and grain size in rivers requires robust methods to estimate sound attenuation by suspended sediment. Theoretical estimates of sediment attenuation require a priori knowledge of the concentration and grain size distribution (GSD), making the method impractical to apply in routine monitoring programs. In-situ methods use acoustic backscatter profile slope to estimate sediment attenuation, and are a more attractive option. However, the performance of in-situ sediment attenuation methods has not been extensively compared to theoretical methods. We used three collocated horizontally mounted ADCPs in the Fraser River at Mission, British Columbia and 298 observations of concentration and GSD along the acoustic beams to calculate theoretical and in-situ sediment attenuation. Conversion of acoustic intensity from counts to decibels is influenced by the instrument noise floor, which affects the backscatter profile shape and therefore in-situ attenuation. We develop a method that converts counts to decibels to maximize profile length, which is useful in rivers where cross-channel acoustic profile penetration is a fraction of total channel width. Nevertheless, the agreement between theoretical and in-situ attenuation is poor at low concentrations because cross-stream gradients in concentration, sediment size or GSD can develop, which affect the backscatter profiles. We establish threshold concentrations below which in-situ attenuation is unreliable in Fraser River. Our results call for careful examination of cross-stream changes in suspended sediment characteristics and acoustic profiles across a range of flows before in-situ attenuation methods are applied in river monitoring programs.
      PubDate: 2017-05-30T11:20:32.53729-05:0
      DOI: 10.1002/2016WR019695
       
  • The Kühtai data set: 25 years of lysimetric, snow pillow, and
           meteorological measurements
    • Authors: P. Krajči; R. Kirnbauer, J. Parajka, J. Schöber, G. Blöschl
      Abstract: Snow measurements at the Kühtai station in Tirol, Austria, (1920m a.s.l.) are described. The data set includes snow water equivalent from a 10 m2 snow pillow, snow melt outflow from a 10 m2 snow lysimeter placed at the same location as the pillow, meteorological data (precipitation, incoming short wave radiation, reflected short wave radiation, air temperature, relative air humidity and wind speed), and other data (snow depths, snow temperatures at seven heights) from the period October, 1990 – May, 2015. All data have been quality checked, and gaps in the meteorological data have been filled in. The data set is unique in that all data are available at a temporal resolution of 15 minutes over a period of 25 years with minimal changes in the experimental setup. The data set can therefore be used to analyse snow pack processes over a long time period, including their extremes and long term changes, in an Alpine climate. Analyses may benefit from the combined measurement of snow water equivalent, lysimeter outflow and precipitation at a wind-sheltered alpine site. An example use of data shows the temporal variability of daily and April 1st snow water equivalent observed at the Kühtai site. The results indicate that the snow water equivalent maximum varies between 200 to more than 500 mm w.e., but there is no statistically significant temporal trend in the period 1990-2015.
      PubDate: 2017-05-26T20:10:48.363168-05:
      DOI: 10.1002/2017WR020445
       
  • Are our dynamic water quality models too complex? A comparison of a new
           parsimonious phosphorus model, SimplyP, and INCA-P
    • Authors: L.A. Jackson-Blake; J.E. Sample, A.J. Wade, R.C. Helliwell, R.A. Skeffington
      Abstract: Catchment-scale water quality models are increasingly popular tools for exploring the potential effects of land management, land use change and climate change on water quality. However, the dynamic, catchment-scale nutrient models in common usage are complex, with many uncertain parameters requiring calibration, limiting their usability and robustness. A key question is whether this complexity is justified. To explore this, we developed a parsimonious phosphorus model, SimplyP, incorporating a rainfall-runoff model and a biogeochemical model able to simulate daily streamflow, suspended sediment, and particulate and dissolved phosphorus dynamics. The model's complexity was compared to one popular nutrient model, INCA-P, and the performance of the two models was compared in a small rural catchment in northeast Scotland. For three land use classes, less than six SimplyP parameters must be determined through calibration, the rest may be based on measurements, whilst INCA-P has around 40 unmeasurable parameters. Despite substantially simpler process-representation, SimplyP performed comparably to INCA-P in both calibration and validation and produced similar long-term projections in response to changes in land management. Results support the hypothesis that INCA-P is overly complex for the study catchment. We hope our findings will help prompt wider model comparison exercises, as well as debate amongst the water quality modelling community as to whether today's models are fit for purpose. Simpler models such as SimplyP have the potential to be useful management and research tools, building blocks for future model development (prototype code is freely available), or benchmarks against which more complex models could be evaluated.
      PubDate: 2017-05-26T20:05:26.138012-05:
      DOI: 10.1002/2016WR020132
       
  • On the use of a snow aridity index to predict remotely sensed forest
           productivity in the presence of bark beetle disturbance
    • Authors: John F. Knowles; Leanne R. Lestak, Noah P. Molotch
      Abstract: We used multiple sources of remotely sensed and ground based information to evaluate the spatio-temporal variability of snowpack accumulation, potential evapotranspiration (PET), and Normalized Difference Vegetation Index (NDVI) throughout the Southern Rocky Mountain ecoregion, USA. Relationships between these variables were used to establish baseline values of expected forest productivity given water and energy inputs. Although both the snow water equivalent (SWE) and a snow aridity index (SAI), which used SWE to normalize PET, were significant predictors of the long-term (1989 – 2012) NDVI, SAI explained 11% more NDVI variability than SWE. Deviations from these relationships were subsequently explored in the context of widespread forest mortality due to bark beetles. Over the entire study area, NDVI was lower per unit SAI in beetle-disturbed compared to undisturbed areas during snow-related drought; however, both SAI and NDVI were spatially heterogeneous within this domain. As a result, we selected three focus areas inside the larger study area within which to isolate the relative impacts of SAI and disturbance on NDVI using multivariate linear regression. These models explained 66%-85% of the NDVI and further suggested that both SAI and disturbance effects were significant, although the disturbance effect was generally greater. These results establish the utility of SAI as a measure of moisture limitation in snow-dominated systems, and demonstrate a reduction in forest productivity due to bark beetle disturbance that is particularly evident during drought conditions resultant from low snow accumulation during the winter.
      PubDate: 2017-05-26T09:10:39.266124-05:
      DOI: 10.1002/2016WR019887
       
  • Biogeochemical hotspots: Role of small water bodies in landscape nutrient
           processing
    • Authors: Frederick Y. Cheng; Nandita B. Basu
      Abstract: Increased loading of nitrogen (N) and phosphorus (P) from agricultural and urban intensification has led to severe degradation of inland and coastal waters. Lakes, reservoirs, and wetlands (lentic systems) retain these nutrients, thus regulating their delivery to downstream waters. While the processes controlling N and P retention are relatively well-known, there is a lack of quantitative understanding of how these processes manifest across spatial scales. We synthesized data from 600 lentic systems across the world to gain insight into the relationship between hydrologic and biogeochemical controls on nutrient retention. Our results indicate that the first-order reaction rate constant, k [T−1], is inversely proportional to the hydraulic residence time, τ [T], across six orders of magnitude in residence time for total N, total P, nitrate, and phosphate. We hypothesized that the consistency of the relationship points to a strong hydrologic control on biogeochemical processing, and validated our hypothesis using a sediment-water model that links major nutrient removal processes with system size. Our results indicate that the nutrient removal potential lost is greater when smaller wetlands are lost compared to larger wetlands given the same total area. Finally, the k-τ relationships were upscaled to the landscape scale using a wetland size-frequency distribution. Results suggest the disproportionately large role of small wetlands in landscape scale nutrient processing – 50% of nitrogen removal occurs in wetlands smaller than 102.5 m2 in our example. Our study highlights the need for a stronger focus on small lentic systems as major nutrient sinks in the landscape.
      PubDate: 2017-05-26T09:10:35.2467-05:00
      DOI: 10.1002/2016WR020102
       
  • Woody plant encroachment reduces annual runoff and shifts runoff
           mechanisms in the tallgrass prairie, USA
    • Authors: Lei Qiao; Chris B. Zou, Elaine Stebler, Rodney E. Will
      Abstract: Woody plant encroachment into semiarid and subhumid rangelands is a global phenomenon with important hydrological implications. Observational and experimental results reported both increases and decreases in annual runoff for encroached watersheds and little is known regarding the underlying runoff generation mechanisms. To systematically study the effect of woody plant encroachment on runoff generation processes, seven experimental watersheds were instrumented in 2010, three on grassland sites and four on adjacent sites that were heavily encroached by eastern redcedar (Juniperus virigiana) in the southern Great Plains, USA. Results showed that the runoff coefficient was 1.4± 0.6% in eastern redcedar encroached watersheds, significantly lower than 4.4 ± 0.7% in grassland watersheds for the four water years from 2011 to 2014. Eastern redcedar encroachment resulted in reduction of both surface and subsurface flows and the magnitude of reduction depended on annual precipitation. While there were nearly equal contributions between overland flow and subsurface flow, 87% of the total runoff from grassland watersheds occurred under saturated or nearly saturated soil condition, while 86% of runoff under encroached watersheds was generated under unsaturated soil condition, suggesting a shift from saturation excess overland flow to infiltration excess overland flow. These results permitted reconciliation of observed difference of streamflow responses associated with Juniperus spp. encroachment in the region and provided insights to better predict change in water resources under vegetation changes in subhumid regions of the south-central USA.
      PubDate: 2017-05-26T09:10:30.737736-05:
      DOI: 10.1002/2016WR019951
       
  • A vegetation-focused soil-plant-atmospheric-continuum model to study
           hydrodynamic soil-plant water relations
    • Authors: Zijuan Deng; Huade Guan, John Hutson, Michael A. Forster, Yunquan Wang, Craig T. Simmons
      Abstract: A novel simple soil-plant-atmospheric-continuum model that emphasizes the vegetation's role in controlling water transfer (v-SPAC) has been developed in this study. The v-SPAC model aims to incorporate both plant and soil hydrological measurements into plant water transfer modeling. The model is different from previous SPAC models in that v-SPAC uses (1) a dynamic plant resistance system in the form of a vulnerability curve that can be easily obtained from sap flow and stem xylem water potential time series and; (2) a plant capacitance parameter to buffer the effects of transpiration on root water uptake. The unique representation of root resistance and capacitance allows the model to embrace SPAC hydraulic pathway from bulk soil, to soil-root interface, to root xylem and finally to stem xylem where the xylem water potential is measured. The v-SPAC model was tested on a native tree species in Australia, Eucalyptus crenulata saplings, with controlled drought treatment. To further validate the robustness of the v-SPAC model, it was compared against a soil-focused SPAC model, LEACHM. The v-SPAC model simulation results closely matched the observed sap flow and stem water potential time series, as well as the soil moisture variation of the experiment. The v-SPAC model was found to be more accurate in predicting measured data than the LEACHM model, underscoring the importance of incorporating root resistance into SPAC models and the benefit of integrating plant measurements to constrain SPAC modeling.
      PubDate: 2017-05-26T09:10:27.844502-05:
      DOI: 10.1002/2017WR020467
       
  • Multivariate Copula Analysis Toolbox (MvCAT): Describing dependence and
           underlying uncertainty using a Bayesian framework
    • Authors: Mojtaba Sadegh; Elisa Ragno, Amir AghaKouchak
      Abstract: We present a newly developed Multivariate Copula Analysis Toolbox (MvCAT) which includes a wide range of copula families with different levels of complexity. MvCAT employs a Bayesian framework with a residual-based Gaussian likelihood function for inferring copula parameters, and estimating the underlying uncertainties. The contribution of this paper is threefold: (a) providing a Bayesian framework to approximate the predictive uncertainties of fitted copulas, (b) introducing a hybrid-evolution Markov Chain Monte Carlo (MCMC) approach designed for numerical estimation of the posterior distribution of copula parameters, and (c) enabling the community to explore a wide range of copulas and evaluate them relative to the fitting uncertainties. We show that the commonly used local optimization methods for copula parameter estimation often get trapped in local minima. The proposed method, however, addresses this limitation and improve describing the dependence structure. MvCAT also enables evaluation of uncertainties relative to the length of record, which is fundamental to a wide range of applications such as multivariate frequency analysis.
      PubDate: 2017-05-24T09:10:40.052032-05:
      DOI: 10.1002/2016WR020242
       
  • Increased sediment oxygen flux in lakes and reservoirs: the impact of
           hypolimnetic oxygenation
    • Authors: Kevin A. Bierlein; Maryam Rezvani, Scott A. Socolofsky, Lee D. Bryant, Alfred Wüest, John C. Little
      Abstract: Hypolimnetic oxygenation is an increasingly common lake management strategy for mitigating hypoxia/anoxia and associated deleterious effects on water quality. A common effect of oxygenation is increased oxygen consumption in the hypolimnion and predicting the magnitude of this increase is the crux of effective oxygenation system design. Simultaneous measurements of sediment oxygen flux (JO2) and turbulence in the bottom boundary layer of two oxygenated lakes were used to investigate the impact of oxygenation on JO2. Oxygenation increased JO2 in both lakes by increasing the bulk oxygen concentration, which in turn steepens the diffusive gradient across the diffusive boundary layer. At high flow rates, the diffusive boundary layer thickness decreased as well. A transect along one of the lakes showed JO2 to be spatially quite variable, with near-field and far-field JO2 differing by a factor of four. Using these in situ measurements, physical models of interfacial flux were compared to microprofile-derived JO2 to determine which models adequately predict JO2 in oxygenated lakes. Models based on friction velocity, turbulence dissipation rate, and the integral scale of turbulence agreed with microprofile-derived JO2 in both lakes. These models could potentially be used to predict oxygenation-induced oxygen flux and improve oxygenation system design methods for a broad range of reservoir systems.
      PubDate: 2017-05-24T09:10:31.376572-05:
      DOI: 10.1002/2016WR019850
       
  • Development of a Copula-based Particle Filter (CopPF) Approach for
           Hydrologic Data Assimilation under Consideration of Parameter
           Interdependence
    • Authors: Y.R. Fan; G.H. Huang, B.W. Baetz, Y.P. Li, K. Huang
      Abstract: In this study, a copula-based particle filter (CopPF) approach was developed for sequential hydrological data assimilation by considering parameter correlation structures. In CopPF, multivariate copulas are proposed to reflect parameter interdependence before the resampling procedure with new particles then being sampled from the obtained copulas. Such a process can overcome both particle degeneration and sample impoverishment. The applicability of CopPF is illustrated with three case studies using a two-parameter simplified model and two conceptual hydrologic models. The results for the simplified model indicate that model parameters are highly correlated in the data assimilation process, suggesting a demand for full description of their dependence structure. Synthetic experiments on hydrologic data assimilation indicate that CopPF can rejuvenate particle evolution in large spaces and thus achieve good performances with low sample size scenarios. The applicability of CopPF is further illustrated through two real case studies. It is shown that, compared with traditional particle filter (PF) and particle Markov chain Monte Carlo (PMCMC) approaches, the proposed method can provide more accurate results for both deterministic and probabilistic prediction with a sample size of 100. Furthermore, the sample size would not significantly influence the performance of CopPF. Also, the copula resampling approach dominates parameter evolution in CopPF, with more than 50% of particles sampled by copulas in most sample size scenarios.
      PubDate: 2017-05-24T09:10:30.047386-05:
      DOI: 10.1002/2016WR020144
       
  • Introduction and evaluation of a Weibull hydraulic conductivity - pressure
           head relationship for unsaturated soils
    • Authors: Shmuel Assouline; John Selker
      Abstract: Analytical and numerical solutions for flow through partially saturated soils typically require functional relationships between water content, pressure, and hydraulic conductivity. Here we propose a Weibull-type function to describe the hydraulic conductivity-pressure head function. We show that this is a more flexible function that has the ability to address air entry pressure, while retaining the ease of integration and differentiation that facilitates many important computations which have to this point favoured the Gardner exponential function (which is a special case of the proposed function). The ability to fit measured values is shown to be better than commonly employed functions of similar simplicity. Strong relationships were found between the parameters of the proposed function and the corresponding soil water retention curve, thus providing predictive capability. A simple relationship was also found between the parameters of the function and the wetting front pressure, ψf. Applying the proposed function to estimate ψf improves the accuracy of predictions for infiltration using the Green and Ampt model.
      PubDate: 2017-05-24T09:10:28.679389-05:
      DOI: 10.1002/2017WR020796
       
  • Tradeoff between cost and accuracy in large-scale surface water dynamic
           modeling
    • Authors: Augusto Getirana; Christa Peters-Lidard, Matthew Rodell, Paul D. Bates
      Abstract: Recent efforts have led to the development of the local inertia formulation (INER) for an accurate but still cost-efficient representation of surface water dynamics, compared to the widely used kinematic wave equation (KINE). In this study, both formulations are evaluated over the Amazon basin in terms of computational costs and accuracy in simulating streamflows and water levels through synthetic experiments and comparisons against ground-based observations. Varying time steps are considered as part of the evaluation and INER at 60-second time step is adopted as the reference for synthetic experiments. Five hybrid (HYBR) realizations are performed based on maps representing the spatial distribution of the two formulations that physically represent river reach flow dynamics within the domain. Maps have fractions of KINE varying from 35.6% to 82.8%. KINE runs show clear deterioration along the Amazon river and main tributaries, with maximum RMSE values for streamflow and water level reaching 7827m3.s−1 and 1379cm near the basin's outlet. However, KINE is at least 25% more efficient than INER with low model sensitivity to longer time steps. A significant improvement is achieved with HYBR, resulting in maximum RMSE values of 3.9-292m3.s−1 for streamflows and 1.1-28.5cm for water levels, and cost reduction of 6-16%, depending on the map used. Optimal results using HYBR are obtained when the local inertia formulation is used in about one third of the Amazon basin, reducing computational costs in simulations while preserving accuracy. However, that threshold may vary when applied to different regions, according to their hydrodynamics and geomorphological characteristics.
      PubDate: 2017-05-24T09:10:24.026037-05:
      DOI: 10.1002/2017WR020519
       
  • Analytical estimation show low depth-independent water loss due to vapor
           flux from deep aquifers
    • Authors: John Selker
      Abstract: Recent articles have provided estimates of evaporative flux from water tables in deserts that span five orders of magnitude. In this paper we present an analytical calculation that indicates aquifer vapor flux to be limited to 0.01 mm/yr for sites where there is negligible recharge and the water table is well over 20 m below the surface. This value arises from the geothermal gradient, and therefore is nearly independent of the actual depth of the aquifer. The value is in agreement with several numerical studies, but is 500 times lower than recently reported experimental values, and 100 times larger than an earlier analytical estimate.
      PubDate: 2017-05-24T09:10:21.724697-05:
      DOI: 10.1002/2017WR021014
       
  • Lags in hydrologic recovery following an extreme drought: Assessing the
           roles of climate and catchment characteristics
    • Authors: Yuting Yang; Tim R. McVicar, Randall J. Donohue, Yongqiang Zhang, Michael L. Roderick, Francis H.S. Chiew, Lu Zhang, Junlong Zhang
      Abstract: Drought, generally characterized by below-average water supply, propagates through the hydrologic system with consequent ecological and societal impacts. Compared with other drought aspects, the recovery of drought especially in the hydrological components, which directly relates to the recovery of water resources for agricultural, ecological and human needs, is less-understood. Here, taking the Millennium drought in southeast Australia (∼1997-2009) as an illustrating case, we comprehensively examined multiple aspects of the meteorological (i.e., precipitation) and hydrological (i.e., streamflow and baseflow) droughts across 130 unimpaired catchments using long-term hydro-meteorological observations. Results show that the duration and intensity of the meteorological drought are both lengthened and amplified in the hydrological drought, suggesting a nonstationarity in the rainfall-runoff relationship during a prolonged drought. Additionally, we find a time lag commonly exists between the end of the meteorological droughts and the end of the hydrological drought, with the recovery of baseflow showing a longer lag than the recovery of streamflow. The recovery rate of precipitation after drought was found to be the dominant factor that controls the recovery of hydrological droughts while catchment landscape (i.e., valley bottom flatness) plays an important but secondary role in controlling the lags in the hydrological recovery. Other hydro-climatic factors and catchment properties appear to have only minor influences governing hydrological drought recovery. Our findings highlight a delayed response in the terrestrial components of the hydrological cycle to precipitation after prolonged drought, and provide valuable scientific guidance to water resources management and water security assessment in regions facing future droughts.
      PubDate: 2017-05-23T14:45:23.382632-05:
      DOI: 10.1002/2017WR020683
       
  • Dynamic linear models to explore time-varying suspended sediment-discharge
           rating curves
    • Authors: Kuk-Hyun Ahn; Brian Yellen, Scott Steinschneider
      Abstract: This study presents a new method to examine long-term dynamics in sediment yield using time-varying sediment-discharge rating curves. Dynamic linear models (DLMs) are introduced as a time series filter that can assess how the relationship between streamflow and sediment concentration or load changes over time in response to a wide variety of natural and anthropogenic watershed disturbances or long-term changes. The filter operates by updating parameter values using a recursive Bayesian design that responds to one-day-ahead forecast errors while also accounting for observational noise. The estimated time series of rating curve parameters can then be used to diagnose multi-scale (daily-decadal) variability in sediment yield after accounting for fluctuations in streamflow. The technique is applied in a case study examining changes in turbidity load, a proxy for sediment load, in the Esopus Creek watershed, part of the New York City drinking water supply system. The results show that turbidity load exhibits a complex array of variability across time scales. The DLM highlights flood event-driven positive hysteresis, where turbidity load remained elevated for months after large flood events, as a major component of dynamic behavior in the rating curve relationship. The DLM also produces more accurate one-day-ahead loading forecasts compared to other static and time-varying rating curve methods. The results suggest that DLMs provide a useful tool for diagnosing changes in sediment-discharge relationships over time and may help identify variability in sediment concentrations and loads that can be used to inform dynamic water quality management.
      PubDate: 2017-05-22T08:20:31.187143-05:
      DOI: 10.1002/2017WR020381
       
  • Hindered erosion: The biological mediation of non-cohesive sediment
           behaviour
    • Authors: X. D. Chen; C. K. Zhang, D. M. Paterson, C. E. L. Thompson, I. H. Townend, Z. Gong, Z. Zhou, Q. Feng
      Abstract: Extracellular polymeric substances (EPS) are ubiquitous on tidal flats but their impact on sediment erosion has not been fully understood. Laboratory-controlled sediment beds were incubated with Bacillus subtilis for 5, 10, 16 and 22 days before the erosion experiments, to study the temporal and spatial variations in sediment stability caused by the bacterial secreted EPS. We found the bio-sedimentary systems showed different erosional behaviour related to biofilm maturity and EPS distribution. In the first stage (5 days), the bio-sedimentary bed was more easily eroded than the clean sediment. With increasing growth period, bound EPS became more widely distributed over the vertical profile resulting in bed stabilisation. After 22 days, the bound EPS was highly concentrated within a surface biofilm, but a relatively high content also extended to a depth of 5 mm and then decayed sharply with depth. The biofilm increased the critical shear stress of the bed and furthermore, it enabled the bed to withstand threshold conditions for an increased period of time as the biofilm degraded before eroding. After the loss of biofilm protection, the high EPS content in the sub-layers continued to stabilise the sediment (hindered erosion) by binding individual grains, as visualized by electron microscopy. Consequently, the bed strength did not immediately revert to the abiotic condition but progressively adjusted, reflecting the depth profile of the EPS. Our experiments highlight the need to treat the EPS-sediment conditioning as a bed-age associated and depth-dependent variable that should be included in the next generation of sediment transport models.
      PubDate: 2017-05-22T08:20:27.079239-05:
      DOI: 10.1002/2016WR020105
       
  • Replenishing an unconfined coastal aquifer to control seawater intrusion:
           Injection or infiltration?
    • Authors: Chunhui Lu; Wenlong Shi, Pei Xin, Jichun Wu, Adrian D. Werner
      Abstract: In this study, we compare the performances of well injection and pond infiltration in controlling seawater intrusion in an unconfined coastal aquifer through two scenario groups: (1) a single injection well vs. an elliptic infiltration pond, and (2) an injection-extraction well pair system vs. an elliptic infiltration pond-extraction well system. Comparison is based on quantitative indicators that include the interface toe location, saltwater volume, and maximum net extraction rate (for scenario 2). We introduce a method to determine the maximum net extraction rate for cases where the locations of stagnation points cannot be easily derived. Analytical analysis shows that the performances of injection and infiltration are the same, provided that the pond shape is circular. The examination of scenario group (1) suggests that the shape of the infiltration pond has a minor effect on the interface toe location as well as the reduction in the saltwater volume, given the same total recharge rate. The investigation of scenario group (2) indicates, by contrast, that the maximum net extraction rate increases significantly with the increasing ratio of b to a, where a and b are semi-axes of the ellipse parallel and perpendicular to the coastline, respectively. Specifically, for a typical aquifer assumed, an increase of 40% is obtained for the maximum net extraction when b/a increases from 1/200 to 200. Despite that the study is based on a simplified model, the results provide initial guidance for practitioners when planning to use an aquifer recharge strategy to restore a salinized unconfined coastal aquifer.
      PubDate: 2017-05-19T09:05:57.062423-05:
      DOI: 10.1002/2016WR019625
       
  • Periodic sediment shift in migrating ripples influences benthic microbial
           activity
    • Authors: Sanja Zlatanovic; Jenny Fabian, Clara Mendoza-Lera, K. Benjamin Woodward, Katrin Premke, Michael Mutz
      Abstract: Migrating bedforms have high levels of particulate organic matter and high rates of pore water exchange, causing them to be proposed as hot spots of carbon turnover in rivers. However, the shifting of sediments and associated mechanical disturbance within migrating bedforms, such as ripples, may stress and abrade microbial communities, reducing their activity. In a microcosm experiment, we replicated the mechanical disturbances caused by the periodic sediment shift within ripples under oligotrophic conditions. We assessed the effects on fungal and bacterial biomass ratio (F:B), microbial community respiration (CR), and bacterial production (BCP) and compared with stable undisturbed sediments. Interactions between periodic mechanical disturbance and sediment-associated particulate organic matter (POM) were tested by enriching sediments collected from migrating ripples with different qualities of POM (fish feces, leaf litter fragments and no addition treatments). F:B and BCP were affected by an interaction between mechanical disturbance and POM quality. Fish feces enriched sediments showed increased F:B and BCP compared to sediments with lower POM quality and responded with a decrease of F:B and BCP to sediment disturbance. In the other POM treatments F:B and BCP were not affected by disturbance. Microbial respiration was however reduced by mechanical disturbance to similar low activity levels regardless of POM qualities added, whereas fish feces enriched sediment showed short temporary boost of CR. With the worldwide proliferation of migrating sand ripples due to massive catchment erosion, suppressed mineralization of POM will increasingly affect stream metabolism, downstream transport of POM and carbon cycling from reach to catchment scale.
      PubDate: 2017-05-19T09:05:52.965713-05:
      DOI: 10.1002/2017WR020656
       
  • Induced heterogeneity of soil water content and chemical properties by
           treated wastewater irrigation and its reclamation by freshwater irrigation
           
    • Authors: Matan Rahav; Naaran Brindt, Uri Yermiyahu, Rony Wallach
      Abstract: The recognition of treated wastewater (TWW) as an alternative water resource is expanding in areas with a shortage of freshwater (FW) resources. Today, most orchards in Israel are irrigated with TWW. While the benefits of using TWW for irrigation are apparent, evidence of its negative effects on soil, trees and yield is accumulating. This study, performed in a commercial TWW-irrigated citrus orchard in central Israel, examined the effects of (1) soil-wettability decrease due to prolonged TWW irrigation on the spatial and temporal distribution of water content and associated chemical properties in the root zone; (2) the conversion of irrigation in half of the TWW-irrigated research plot to FW (2012) for soil reclamation. Electrical resistivity tomography surveys in the substantially water repellent soils revealed that water flow is occurring along preferential flow paths in both plots, leaving behind a considerably nonuniform water-content distribution. This was despite the gradual relief in soil water repellency measured in the FW plots. Four soil-sampling campaigns (spring and fall, 2014–2016), performed in 0–20 and 20–40 cm layers of the research plot, revealed bimodal gravimetrically measured water-content distribution. The preferential flow led to uneven chemical-property distribution, with substantially high concentrations in the dry spots, and lower concentrations in the wet spots along the preferential flow paths. The average salt and nutrient concentrations, which were initially high in both plots, gradually dispersed with time, as concentrations in the FW plots decreased. Nevertheless, the efficiency of reclaiming TWW soil by FW irrigation appears low.
      PubDate: 2017-05-19T09:05:48.879466-05:
      DOI: 10.1002/2016WR019860
       
  • Concentration-discharge relationships during an extreme event: Contrasting
           behavior of solutes and changes to chemical quality of dissolved organic
           material in the Boulder Creek Watershed during the September 2013 flood
    • Authors: Garrett P. Rue; Nathan D. Rock, Rachel S. Gabor, John Pitlick, Malak Tfaily, Diane M. McKnight
      Abstract: During the week of September 9-15, 2013, about 44 cm of rain fell across Boulder County, Colorado, USA, representing a very rare precipitation event. The resultant stream flows corresponded to an extreme event not seen since the historical flood of 1894. For the Boulder Creek Critical Zone Observatory (BcCZO), this event provided an opportunity to study the effect of extreme rainfall on solute concentration-discharge relationships and biogeochemical processes. We measured weathering-derived lithologic solutes (Ca, Mg, Na, K, and Si) and dissolved organic carbon (DOC) concentrations at two sites on Boulder Creek during the recession of peak flow. We also isolated four distinct fractions of dissolved organic matter (DOM) for chemical characterization. At the upper and lower sites, all solutes had their highest concentration at peak flow. At the upper site, which represented a mostly forested catchment, the concentrations of lithologic solutes decreased slightly during flood recession. In contrast, DOC and K concentrations decreased by a factor of three. At the lower site within the urban corridor, concentration of lithologic solutes decreased substantially for a few days before rebounding, whereas the DOC and K concentrations continued to decrease. Additionally, we found spatiotemporal trends in the chemical quality of DOM that were consistent with a limited reservoir of soluble organic matter in surficial soils becoming depleted and deeper layers of the Critical Zone contributing DOM during the flood recession. Overall, these results suggest that despite the extreme flood event, concentration-discharge relationships were similar to typical snowmelt periods in this Rocky Mountain region.
      PubDate: 2017-05-19T09:05:47.469953-05:
      DOI: 10.1002/2016WR019708
       
  • Observations of the impact of rock heterogeneity on solute spreading and
           mixing
    • Authors: Maartje Boon; Branko Bijeljic, Sam Krevor
      Abstract: Rock heterogeneity plays an important role in solute spreading and mixing in hydrogeologic systems. Few observations, however, have been made that can spatially resolve these processes in 3-D, in consolidated rocks. We make observations of the spatially resolved steady state concentration of a sodium iodide solute while flowing brine through cylindrical rock cores using X-ray CT imaging. Three rocks with an increasing level of heterogeneity are chosen: Berea sandstone, Ketton carbonate and Indiana carbonate. The impact of heterogeneity on solute transport is analyzed by: 1., quantifying spreading and mixing using metrics such as the transverse dispersion coefficient, the dilution index, the reactor ratio and the scalar dissipation rate, and 2., visualizing and analyzing flow structures such as meandering, flow-focusing and flow-splitting using iso-concentration contour maps. The transverse dispersion coefficient, Dt, and the variation in Dt throughout the rock core, increases with Peclét number (Pe) and rock heterogeneity. The reactor ratio indicates that mixing is Fickian for the Berea sandstone and Ketton carbonate, but diverges for the Indiana carbonate. The temporal evolution of the scalar dissipation rate, a measure of the mixing rate, remains close to that of Fickian mixing for the Berea and Ketton rocks but not for the Indiana. Heterogeneous rock features are observed to cause meandering, focusing or splitting of the plume depending on Pe.
      PubDate: 2017-05-19T09:05:45.564374-05:
      DOI: 10.1002/2016WR019912
       
  • Time scales of relaxation dynamics during transient conditions in
           two-phase flow
    • Authors: Steffen Schlüter; Steffen Berg, Tianyi Li, Hans-Jörg Vogel, Dorthe Wildenschild
      Abstract: The relaxation dynamics towards a hydrostatic equilibrium after a change in phase saturation in porous media is governed by fluid reconfiguration at the pore scale. Little is known whether a hydrostatic equilibrium in which all interfaces come to rest is ever reached and which microscopic processes govern the time scales of relaxation. Here we apply fast synchrotron-based X-ray tomography (X-ray CT) to measure the slow relaxation dynamics of fluid interfaces in a glass bead pack after fast drainage of the sample. The relaxation of interfaces triggers internal redistribution of fluids, reduces the surface energy stored in the fluid interfaces and relaxes the contact angle towards the equilibrium value while the fluid topology remains unchanged. The equilibration of capillary pressures occurs in two stages: (i) a quick relaxation within seconds in which most of the pressure drop that built up during drainage is dissipated, a process that is to fast to be captured with fast X-ray CT, and (ii) a slow relaxation with characteristic time scales of 1-4 h which manifests itself as a spontaneous imbibition process that is well described by the Washburn equation for capillary rise in porous media. The slow relaxation implies that a hydrostatic equilibrium is hardly ever attained in practice when conducting two-phase experiments in which a flux boundary condition is changed from flow to no-flow. Implications for experiments with pressure boundary conditions are discussed.
      PubDate: 2017-05-17T11:30:45.529344-05:
      DOI: 10.1002/2016WR019815
       
  • Chemical mass transport between fluid fine tailings and the overlying
           water cover of an oil sands end pit lake
    • Authors: Kathryn A. Dompierre; S. Lee Barbour, Rebecca L. North, Sean K. Carey, Matthew B.J. Lindsay
      Abstract: Fluid fine tailings (FFT) are a principal by-product of the bitumen extraction process at oil sands mines. Base Mine Lake (BML) – the first full-scale demonstration oil sands end pit lake (EPL) – contains approximately 1.9 x108 m3 of FFT stored under a water cover within a decommissioned mine pit. Chemical mass transfer from the FFT to the water cover can occur via two key processes: (1) advection-dispersion driven by tailings settlement; and (2) FFT disturbance due to fluid movement in the water cover. Dissolved chloride (Cl) was used to evaluate the water cover mass balance and to track mass transport within the underlying FFT based on field sampling and numerical modeling. Results indicated that FFT was the dominant Cl source to the water cover and that the FFT is exhibiting a transient advection-dispersion mass transport regime with intermittent disturbance near the FFT-water interface. The advective pore water flux was estimated by the mass balance to be 0.002 m3 m−2 d−1, which represents 0.73 m of FFT settlement per year. However, the FFT pore water Cl concentrations and corresponding mass transport simulations indicated that advection rates and disturbance depths vary between sample locations. The disturbance depth was estimated to vary with location between 0.75 and 0.95 m. This investigation provides valuable insight for assessing the geochemical evolution of the water cover and performance of EPLs as an oil sands reclamation strategy.
      PubDate: 2017-05-17T11:25:34.802655-05:
      DOI: 10.1002/2016WR020112
       
  • Nonparametric triple collocation
    • Authors: Grey S. Nearing; Soni Yatheendradas, Wade T. Crow, David D. Bosch, Michael H. Cosh, David C. Goodrich, Mark S. Seyfried, Patrick J. Starks
      Abstract: Triple collocation has found widespread application in the hydrological sciences because it provides information about the errors in our measurements without requiring that we have any direct access to the true value of the variable being measured. Triple collocation derives variance-covariance relationships between three or more independent measurement sources and an indirectly observed truth variable in the case where the measurement operators are additive. We generalize that theory to arbitrary observation operators by deriving nonparametric analogues to the total error and total correlation statistics as integrations of divergences from conditional to marginal probability ratios. The nonparametric solution to the full measurement problem is under-determined, and we therefore retrieve conservative bounds on the theoretical total nonparametric error and correlation statistics. We examine the application of both linear and nonlinear triple collocation to synthetic examples and to a real-data test case related to evaluating space-borne soil moisture retrievals using sparse monitoring networks and dynamical process models.
      PubDate: 2017-05-17T11:25:27.284272-05:
      DOI: 10.1002/2017WR020359
       
  • Geological entropy and solute transport in heterogeneous porous media
    • Authors: Marco Bianchi; Daniele Pedretti
      Abstract: We propose a novel approach to link solute transport behavior to the physical heterogeneity of the aquifer, which we fully characterize with two measurable parameters: the variance of the log K values (σY2), and a new indicator (HR) that integrates multiple properties of the K field into a global measure of spatial disorder or geological entropy. From the results of a detailed numerical experiment considering solute transport in K fields representing realistic distributions of hydrofacies in alluvial aquifers, we identify empirical relationship between the two parameters and the first three central moments of the distributions of arrival times of solute particles at a selected control plane. The analysis of experimental data indicates that the mean and the variance of the solutes arrival times tend to increase with spatial disorder (i.e, HR increasing), while highly skewed distributions are observed in more orderly structures (i.e, HR decreasing) or at higher σY2. We found that simple closed-form empirical expressions of the bivariate dependency of skewness on HR and σY2 can be used to predict the emergence of non-Fickian transport in K fields considering a range of structures and heterogeneity levels, some of which based on documented real aquifers. The accuracy of these predictions and in general the results from this study indicate that a description of the global variability and structure of the K field in terms of variance and geological entropy offers a valid and broadly applicable approach for the interpretation and prediction of transport in heterogeneous porous media.
      PubDate: 2017-05-17T03:26:20.105264-05:
      DOI: 10.1002/2016WR020195
       
  • A new unconditionally stable and consistent quasi-analytical in-stream
           water quality solution scheme for CSTR-basedwater quality simulators
    • Authors: Befekadu Taddesse Woldegiorgis; Ann van Griensven, Fernando Pereira, Willy Bauwens
      Abstract: Most common numerical solutions used in CSTR-based in-stream water quality simulators are susceptible to instabilities and/or solution inconsistencies. Usually, they cope with instability problems by adopting computationally expensive small time steps. However, some simulators use fixed computation time steps and hence do not have the flexibility to do so. This paper presents a novel quasi-analytical solution for CSTR-based water quality simulators of an unsteady system. The robustness of the new method is compared with the commonly used fourth order Runge-Kutta methods, the Euler method and three versions of the SWAT model (SWAT2012, SWAT-TCEQ and ESWAT). The performance of each method is tested for different hypothetical experiments. Besides the hypothetical data, a real case study is used for comparison. The growth factors we derived as stability measures for the different methods and the R-factor -considered as a consistency measureturned out to be very useful for determining the most robust method. The new method outperformed all the numerical methods used in the hypothetical comparisons. The application for the Zenne River (Belgium) shows that the new method provides stable and consistent BOD simulations whereas the SWAT2012 model is shown to be unstable for the standard daily computation time step. The new method unconditionally simulates robust solutions. Therefore, it is a reliable scheme for CSTR-based water quality simulators that use first order reaction formulations.
      PubDate: 2017-05-16T05:40:34.380907-05:
      DOI: 10.1002/2016WR019558
       
  • Beaver-mediated lateral hydrologic connectivity, fluvial carbon and
           nutrient flux, and aquatic ecosystem metabolism
    • Authors: Pam Wegener; Tim Covino, Ellen Wohl
      Abstract: River networks that drain mountain landscapes alternate between narrow and wide valley segments. Within the wide segments, beaver activity can facilitate the development and maintenance of complex, multi-thread planform. Because the narrow segments have limited ability to retain water, carbon, and nutrients, the wide, multi-thread segments are likely important locations of retention. We evaluated hydrologic dynamics, nutrient flux, and aquatic ecosystem metabolism along two adjacent segments of a river network in the Rocky Mountains, Colorado: 1) a wide, multi-thread segment with beaver activity; and, 2) an adjacent (directly upstream) narrow, single-thread segment without beaver activity. We used a mass balance approach to determine the water, carbon, and nutrient source-sink behavior of each river segment across a range of flows. While the single-thread segment was consistently a source of water, carbon, and nitrogen, the beaver impacted multi-thread segment exhibited variable source-sink dynamics as a function of flow. Specifically, the multi-thread segment was a sink for water, carbon, and nutrients during high flows, and subsequently became a source as flows decreased. Shifts in river-floodplain hydrologic connectivity across flows related to higher and more variable aquatic ecosystem metabolism rates along the multi-thread relative to the single-thread segment. Our data suggest that beaver activity in wide valleys can create a physically complex hydrologic environment that can enhance hydrologic and biogeochemical buffering, and promote high rates of aquatic ecosystem metabolism. Given the widespread removal of beaver, determining the cumulative effects of these changes is a critical next step in restoring function in altered river networks.
      PubDate: 2017-05-15T20:45:43.052119-05:
      DOI: 10.1002/2016WR019790
       
  • Reexamining ultrafiltration and solute transport in groundwater
    • Authors: C. E. Neuzil; Mark Person
      Abstract: Geologic ultrafiltration – slowing of solutes with respect to flowing groundwater – poses a conundrum: it is consistently observed experimentally in clay-rich lithologies, but has been difficult to identify in subsurface data. Resolving this could be important for clarifying clay and shale transport properties at large scales as well as interpreting solute and isotope patterns for applications ranging from nuclear waste repository siting to understanding fluid transport in tectonically active environments. Simulations of one-dimensional NaCl transport across ultrafiltering clay membrane strata constrained by emerging data on geologic membrane properties showed different ultrafiltration effects than have often been envisioned. In relatively high permeability advection-dominated regimes, salinity increases occurred mostly within membrane units while their effluent salinity initially fell and then rose to match solute delivery. In relatively low permeability diffusion-dominated regimes, salinity peaked at the membrane upstream boundary and effluent salinity remained low. In both scenarios, however, only modest salinity changes (up to ∼ 3 g l−1) occurred because of self-limiting tendencies; membrane efficiency declines as salinity rises, and although sediment compaction increases efficiency, it is also decreases permeability and allows diffusive transport to dominate. It appears difficult for ultrafiltration to generate brines as speculated, but widespread and less extreme ultrafiltration effects in the subsurface could be unrecognized. Conditions needed for ultrafiltration are present in settings that include topographically-driven flow systems, confined aquifer systems subjected to injection or withdrawal, compacting basins, and accretionary complexes.
      PubDate: 2017-05-15T20:45:40.203796-05:
      DOI: 10.1002/2017WR020492
       
  • Parameterization and prediction of manoparticles transport in porous
           media: A reanalysis using artificial neural network
    • Authors: Peyman Babakhani; Jonathan Bridge, Ruey-an Doong, Tanapon Phenrat
      Abstract: The continuing rapid expansion of industrial and consumer processes based on nanoparticles (NP) necessitates a robust model for delineating their fate and transport in groundwater. An ability to reliably specify the full parameter set for prediction of NP transport using continuum models is crucial. In this paper we report the reanalysis of a dataset of 493 published column experiment outcomes together with their continuum modelling results. Experimental properties were parametrized into 20 factors which are commonly available. They were then used to predict 5 key continuum model parameters as well as the effluent concentration via artificial neural network (ANN)-based correlations. The Partial Derivatives (PaD) technique and Monte Carlo method were used for the analysis of sensitivities and model-produced uncertainties, respectively. The outcomes shed light on several controversial relationships between the parameters, e.g., it was revealed that the trend of Katt with average pore water velocity was positive. The resulting correlations, despite being developed based on a ‘black-box' technique, (ANN), were able to explain the effects of theoretical parameters such as critical deposition concentration (CDC), even though these parameters were not explicitly considered in the model. Porous media heterogeneity was considered as a parameter for the first time, and showed sensitivities higher than those of dispersivity. The model performance was validated well against subsets of the experimental data and was compared with current models. The robustness of the correlation matrices was not completely satisfactory, since they failed to predict the experimental breakthrough curves (BTCs) at extreme values of ionic strengths.
      PubDate: 2017-05-13T03:47:11.235226-05:
      DOI: 10.1002/2016WR020358
       
  • Hyporheic zone influences on concentration-discharge relationships in a
           headwater sandstone stream
    • Authors: Beth Hoagland; Tess A. Russo, Xin Gu, Lillian Hill, Jason Kaye, Brandon Forsythe, Susan L. Brantley
      Abstract: Complex subsurface flow dynamics impact the storage, routing, and transport of water and solutes to streams in headwater catchments. Many of these hydrogeologic processes are indirectly reflected in observations of stream chemistry responses to rain events, also known as concentration-discharge (CQ) relations. Identifying the relative importance of subsurface flows to stream CQ relationships is often challenging in headwater environments due to spatial and temporal variability. Therefore, this study combines a diverse set of methods, including tracer injection tests, cation exchange experiments, geochemical analyses, and numerical modeling, to map groundwater-surface water interactions along a first-order, sandstone stream (Garner Run) in the Appalachian Mountains of central Pennsylvania. The primary flowpaths to the stream include preferential flow through the unsaturated zone (“interflow”), flow discharging from a spring, and groundwater discharge. Garner Run stream inherits geochemical signatures from geochemical reactions occurring along each of these flowpaths. In addition to end-member mixing effects on CQ, we find that the exchange of solutes, nutrients, and water between the hyporheic zone and main stream channel is a relevant control on the chemistry of Garner Run. CQ relationships for Garner Run were compared to prior results from a nearby headwater catchment overlying shale bedrock (Shale Hills). At the sandstone site, solutes associated with organo-mineral associations in the hyporheic zone influence CQ, while CQ trends in the shale catchment are affected by preferential flow through hillslope swales. The difference in CQ trends document how the lithology and catchment hydrology control CQ relationships.
      PubDate: 2017-05-12T19:50:41.249598-05:
      DOI: 10.1002/2016WR019717
       
  • A theoretically consistent stochastic cascade for temporal disaggregation
           of intermittent rainfall
    • Authors: F. Lombardo; E. Volpi, D. Koutsoyiannis, F. Serinaldi
      Abstract: Generating fine-scale time series of intermittent rainfall that are fully consistent with any given coarse-scale totals is a key and open issue in many hydrological problems. We propose a stationary disaggregation method that simulates rainfall time series with given dependence structure, wet/dry probability, and marginal distribution at a target finer (lower-level) time scale, preserving full consistency with variables at a parent coarser (higher-level) time scale. We account for the intermittent character of rainfall at fine time scales by merging a discrete stochastic representation of intermittency and a continuous one of rainfall depths. This approach yields a unique and parsimonious mathematical framework providing general analytical formulations of mean, variance, and autocorrelation function (ACF) for a mixed-type stochastic process in terms of mean, variance, and ACFs of both continuous and discrete components, respectively. To achieve the full consistency between variables at finer and coarser time scales in terms of marginal distribution and coarse-scale totals, the generated lower-level series are adjusted according to a procedure that does not affect the stochastic structure implied by the original model. To assess model performance, we study rainfall process as intermittent with both independent and dependent occurrences, where dependence is quantified by the probability that two consecutive time intervals are dry. In either case, we provide analytical formulations of main statistics of our mixed-type disaggregation model and show their clear accordance with Monte Carlo simulations. An application to rainfall time series from real world is shown as a proof of concept.
      PubDate: 2017-05-12T19:30:35.923673-05:
      DOI: 10.1002/2017WR020529
       
  • Editorial: A vision for Water Resources Research
    • Authors: Martyn P. Clark; Jean A. Bahr, Marc F. P. Bierkens, Ximing Cai, Terri S. Hogue, Charles H. Luce, Jessica D. Lundquist, D. Scott Mackay, H.J. (Ilja) van Meerveld, Harihar Rajaram, Xavier Sanchez-Vila, Peter A. Troch
      Abstract: Water Resources Research (WRR) continues to evolve as the team of international editors begins a new 4-year term of service. In this Editorial we summarize the importance of WRR in the hydrologic sciences, the challenges ahead, and the plans for the future of the journal.
      PubDate: 2017-05-12T08:53:20.580489-05:
      DOI: 10.1002/2017WR021050
       
  • Valuing environmental services provided by local stormwater management
    • Authors: Daniel A. Brent; Lata Gangadharan, Allison Lassiter, Anke Leroux, Paul A. Raschky
      Abstract: The management of stormwater runoff via distributed green infrastructures delivers a number of environmental services that go beyond the reduction of flood risk, which has been the focus of conventional stormwater systems. Not all of these services may be equally valued by the public, however. This paper estimates households' willingness to pay (WTP) for improvements in water security, stream health, recreational and amenity values, as well as reduction in flood risk and urban heat island effect. We use data from nearly 1,000 personal interviews with residential homeowners in Melbourne and Sydney, Australia. Our results suggest that the WTP for the highest levels of all environmental services is A$799 per household per year. WTP is mainly driven by residents valuing improvements in local stream health, exemptions in water restrictions, the prevention of flash flooding, and decreased peak urban temperatures respectively at A$297, A$244, A$104 and A$65 per year. We further conduct a benefit transfer analysis and find that the WTP and compensating surplus are not significantly different between the study areas. Our findings provide additional support that stormwater management via green infrastructures have large non-market benefits and that, under certain conditions, benefit values can be transferred to different locations.
      PubDate: 2017-05-08T08:51:35.875623-05:
      DOI: 10.1002/2016WR019776
       
  • Using Dual-Domain Advective-Transport Simulation to Reconcile Multiple
           Tracer Ages and Estimate Dual-Porosity Transport Parameters
    • Authors: Ward E. Sanford; L. Niel Plummer, Gerolamo Casile, Ed Busenberg, David L. Nelms, Peter Schlosser
      Abstract: Dual-domain transport is an alternative conceptual and mathematical paradigm to advection-dispersion for describing the movement of dissolved constituents in groundwater. Here we test the use of a dual-domain algorithm combined with advective pathline tracking to help reconcile environmental tracer concentrations measured in springs within the Shenandoah Valley, USA. The approach also allows for the estimation of the three dual-domain parameters: mobile porosity, immobile porosity, and a domain exchange rate constant. Concentrations of CFC-113, SF6, 3H, and 3He were measured at 28 springs emanating from carbonate rocks. The different tracers give three different mean composite piston-flow ages for all the springs that vary from 5 to 18 years. Here we compare four algorithms that interpret the tracer concentrations in terms of groundwater age: piston flow, old-fraction mixing, advective-flowpath modeling, and dual-domain modeling. Whereas the second two algorithms made slight improvements over piston flow at reconciling the disparate piston-flow age estimates, the dual-domain algorithm gave a very marked improvement. Optimal values for the three transport parameters were also obtained, although the immobile porosity value was not well constrained. Parameter correlation and sensitivities were calculated to help quantify the uncertainty. Although some correlation exists between the three parameters being estimated, a watershed simulation of a pollutant breakthrough to a local stream illustrates that the estimated transport parameters can still substantially help to constrain and predict the nature and timing of solute transport. The combined use of multiple environmental tracers with this dual-domain approach could be applicable in a wide variety of fractured-rock settings. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-30T03:46:06.967303-05:
      DOI: 10.1002/2016WR019469
       
  • Issue Information
    • Pages: 4527 - 4529
      PubDate: 2017-07-18T04:48:01.046398-05:
      DOI: 10.1002/wrcr.22253
       
 
 
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