for Journals by Title or ISSN
for Articles by Keywords

 A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z  

              [Sort by number of followers]   [Restore default list]

  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: 20)
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: 32)
Aquaculture Environment Interactions     Open Access   (Followers: 2)
Aquaculture Research     Hybrid Journal   (Followers: 31)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 34)
Aquatic Geochemistry     Hybrid Journal   (Followers: 3)
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: 18)
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: 11)
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: 1)
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: 1)
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: 49)
Journal of Hydro-environment Research     Full-text available via subscription   (Followers: 9)
Journal of Hydroinformatics     Full-text available via subscription   (Followers: 2)
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 the American Water Resources Association     Hybrid Journal   (Followers: 29)
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: 46)
Journal of Water Reuse and Desalination     Partially Free   (Followers: 6)
Journal of Water Science & Environment Technologies     Open Access   (Followers: 2)
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: 7)
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: 10)
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: 13)
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: 41)
Water International     Hybrid Journal   (Followers: 14)
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: 13)
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: 35)
Water Resources Research     Full-text available via subscription   (Followers: 80)
Water SA     Open Access  
Water Science & Technology     Partially Free   (Followers: 25)
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: 21)
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: 20)
Wiley Interdisciplinary Reviews : Water     Hybrid Journal  
WMU Journal of Maritime Affairs     Hybrid Journal   (Followers: 3)

              [Sort by number of followers]   [Restore default list]

Journal Cover Water Resources Research
  [SJR: 2.661]   [H-I: 144]   [80 followers]  Follow
   Full-text available via subscription Subscription journal
   ISSN (Print) 0043-1397 - ISSN (Online) 1944-7973
   Published by AGU Homepage  [17 journals]
  • 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
  • Fluxes of particulates and nutrients during hyrologically-defined seasonal
           periods in an ice-affected great Arctic River, the Mackenzie
    • Authors: Jolie A.L. Gareis; Lance F. W. Lesack
      Abstract: Large circumpolar rivers influence the biogeochemistry of coastal shelf ecosystems and Arctic Ocean circulation. From 2007-2010, Mackenzie River nutrients were measured immediately upstream of the Mackenzie Delta. Total suspended sediment (TSS), and the dissolved and particulate fractions of carbon, nitrogen, and phosphorus, were measured throughout the water-year, stratified by hydrologically-defined seasonal periods. Sampling was most frequent during the ice-breakup and freshet periods to capture changes in sediment and nutrient concentrations that occurred with rapidly changing discharge. Our four-year sampling coverage yielded constituent-specific concentration-discharge relationships that differed among seasonal hydrological periods for six of twelve constituents. Results revealed that having data from the rising-water-freshet, when ice-effects drive much higher water levels for a given discharge than during open-water, had a surprisingly modest effect on annual flux calculations for most constituents. The rising-freshet, however, was dominated by high relative levels of C-rich DOM, P-rich particles, and N-rich inorganic nutrients. Comparisons with fluxes based on volume-weighted means of sample concentrations revealed that most, though not all, river fluxes were strongly driven by short-term concentration-discharge dynamics rather than by total annual discharge. Comparisons with fluxes derived for the Mackenzie discharge record, where results from other years are available, suggest that concentration-discharge relations may not be robust beyond the observation period in this system. Constituent fluxes herein differ from previously published fluxes for the Mackenzie (e.g. lower TSS, higher dissolved organic carbon), likely reflecting more frequent measurements, more representative characterization of differing hydrological periods, and possible changes in concentration-discharge relations during the longer-term Mackenzie record.
      PubDate: 2017-06-19T16:55:29.033371-05:
      DOI: 10.1002/2017WR020623
  • The foam drainage equation for drainage dynamics in unsaturated porous
    • 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
    • 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
  • Smoothing-based compressed state Kalman filter for joint state-parameter
           estimation: Applications in reservoir characterization and CO2 storage
    • Authors: Y. J. Li; Amalia Kokkinaki, Eric F. Darve, Peter K. Kitanidis
      Abstract: The operation of most engineered hydrogeological systems relies on simulating physical processes using numerical models with uncertain parameters and initial conditions. Predictions by such uncertain models can be greatly improved by Kalman-filter techniques that sequentially assimilate monitoring data. Each assimilation constitutes a nonlinear optimization, which is solved by linearizing an objective function about the model prediction and applying a linear correction to this prediction. However, if model parameters and initial conditions are uncertain, the optimization problem becomes strongly nonlinear and a linear correction may yield unphysical results. In this paper, we investigate the utility of one-step ahead smoothing, a variant of the traditional filtering process, to eliminate non-physical results and reduce estimation artifacts caused by nonlinearities. We present the smoothing-based compressed state Kalman filter (sCSKF), an algorithm that combines one step ahead smoothing, in which current observations are used to correct the state and parameters one step back in time, with a non-ensemble covariance compression scheme, that reduces the computational cost by efficiently exploring the high-dimensional state and parameter space. Numerical experiments show that when model parameters are uncertain and the states exhibit hyperbolic behavior with sharp fronts, as in CO2 storage applications, one-step ahead smoothing reduces overshooting errors and, by design, gives physically consistent state and parameter estimates. We compared sCSKF with commonly used data assimilation methods and showed that for the same computational cost, combining one step ahead smoothing and non-ensemble compression is advantageous for real time characterization and monitoring of large-scale hydrogeological systems with sharp moving fronts.
      PubDate: 2017-06-16T05:40:40.783584-05:
      DOI: 10.1002/2016WR020168
  • 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
    • 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
    • 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
  • Complex networks of functional connectivity in a wetland reconnected to
           its floodplain
    • Authors: L. G. Larsen; S. Newman, C. Saunders, J. W. Harvey
      Abstract: Disturbances such as fire or flood, in addition to changing the local magnitude of ecological, hydrological, or biogeochemical processes, can also change their functional connectivity—how those processes interact in space. Complex networks offer promise for quantifying functional connectivity in watersheds. The approach resolves connections between nodes in space based on statistical similarities in perturbation signals (derived from solute time series) and is sensitive to a wider range of timescales than traditional mass-balance modeling. We use this approach to test hypotheses about how fire and flood impact ecological and biogeochemical dynamics in a wetland (Everglades, FL, USA) that was reconnected to its floodplain. Reintroduction of flow pulses after decades of separation by levees fundamentally reconfigured functional connectivity networks. The most pronounced expansion was that of the calcium network, which reflects periphyton dynamics and may represent an indirect influence of elevated nutrients, despite the comparatively smaller observed expansion of phosphorus networks. With respect to several solutes, periphyton acted as a “biotic filter,” shifting perturbations in water-quality signals to different timescales through slow but persistent transformations of the biotic community. The complex-networks approach also revealed portions of the landscape that operate in fundamentally different regimes with respect to dissolved oxygen, separated by a threshold in flow velocity of 1.2 cm/s, and suggested that complete removal of canals may be needed to restore connectivity with respect to biogeochemical processes. Fire reconfigured functional connectivity networks in a manner that reflected localized burn severity, but had a larger effect on the magnitude of solute concentrations.
      PubDate: 2017-06-09T09:50:24.115526-05:
      DOI: 10.1002/2017WR020375
  • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
  • Interactive genetic algorithm for user-centered design of distributed
           conservation practices in a watershed: An examination of user preferences
           in objective space and user behavior
    • Authors: Adriana Debora Piemonti; Meghna Babbar-Sebens, Snehasis Mukhopadhyay, Austin Kleinberg
      Abstract: Interactive Genetic Algorithms (IGA) are advanced human-in-the-loop optimization methods that enable humans to give feedback, based on their subjective and unquantified preferences and knowledge, during the algorithm's search process. While these methods are gaining popularity in multiple fields, there is a critical lack of data and analyses on (a) the nature of interactions of different humans with interfaces of decision support systems (DSS) that employ IGA in water resources planning problems and on (b) the effect of human feedback on the algorithm's ability to search for design alternatives desirable to end-users. In this paper, we present results and analyses of observational experiments in which different human participants (surrogates and stakeholders) interacted with an IGA-based, watershed DSS called WRESTORE to identify plans of conservation practices in a watershed. The main goal of this paper is to evaluate how the IGA adapts its search process in the objective space to a user's feedback, and identify whether any similarities exist in the objective space of plans found by different participants. Some participants focused on the entire watershed, while others focused only on specific local subbasins. Additionally, two different hydrology models were used to identify any potential differences in interactive search outcomes that could arise from differences in the numerical values of benefits displayed to participants. Results indicate that stakeholders, in comparison to their surrogates, were more likely to use multiple features of the DSS interface to collect information before giving feedback, and dissimilarities existed among participants in the objective space of design alternatives.
      PubDate: 2017-05-31T13:00:28.424619-05:
      DOI: 10.1002/2016WR019987
  • 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
    • 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
    • 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
    • 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
    • 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
  • Urban responses to restrictive conservation policy during drought
    • Authors: Joseph Palazzo; Owen R. Liu, Timbo Stillinger, Runsheng Song, Ying Wang, Elizabeth Hiroyasu, Jose Zenteno, Sarah Anderson, Christina Tague
      Abstract: With climate change, the extent, severity, and frequency of droughts around the world are expected to increase. This study analyzed the ability of water districts to meet mandatory urban water conservation targets, which are a common policy response to drought. During California's recent record-breaking drought, a 25% state-wide use reduction objective was set and met. However, only 50% of urban water districts analysed in this study reached their individual conservation target, which offers an opportunity to evaluate the factors associated with successful water use reduction. The findings show that the inclusion of water districts in the polycentric import structure may improve water conservation, but that source diversity may offer water districts a perceived buffer from the need for immediate water use reductions. Drought severity and lower median incomes are associated with greater water conservation, and conservation varies by hydrologic region. This analysis offers insights into institutional design and suggests that local biophysical and economic conditions shape responses in systematic ways that should be addressed by public policy responses to drought.
      PubDate: 2017-05-22T08:20:23.233721-05:
      DOI: 10.1002/2016WR020136
  • 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
    • 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
    • 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
  • Partitioning into hazard subregions for regional peaks-over-threshold
           modeling of heavy precipitation
    • Authors: J. Carreau; P. Naveau, L. Neppel
      Abstract: The French Mediterranean is subject to intense precipitation events occurring mostly in autumn. These can potentally cause flash floods, the main natural danger in the area. The distribution of these events follows specific spatial patterns, i.e. some sites are more likely to be affected than others. The peaks-over-threshold approach consists in modeling extremes, such as heavy precipitation, by the generalized Pareto (GP) distribution. The shape parameter of the GP controls the probability of extreme events and can be related to the hazard level of a given site. When interpolating across a region, the shape parameter should reproduce the observed spatial patterns of the probability of heavy precipitation. However, the shape parameter estimators have high uncertainty which might hide the underlying spatial variability. As a compromise, we choose to let the shape parameter vary in a moderate fashion. More precisely, we assume that the region of interest can be partitioned into sub-regions with constant hazard level. We formalize the model as a conditional mixture of GP distributions. We develop a two-step inference strategy based on probability weighted moments and put forward a cross-validation procedure to select the number of sub-regions. A synthetic data study reveals that the inference strategy is consistent and not very sensitive to the selected number of sub-regions. An application on daily precipitation data from the French Mediterranean shows that the conditional mixture of GPs outperforms two interpolation approaches (with constant or smoothly varying shape parameter).
      PubDate: 2017-05-17T11:30:33.961973-05:
      DOI: 10.1002/2017WR020758
  • 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
  • Improved characterization of heterogeneous permeability in saline aquifers
           from transient pressure data during freshwater injection
    • Authors: Peter K. Kang; Jonghyun Lee, Xiaojing Fu, Seunghak Lee, Peter K. Kitanidis, Ruben Juanes
      Abstract: Managing recharge of freshwater into saline aquifers requires accurate estimation of the heterogeneous permeability field for maximizing injection and recovery efficiency. Here, we present a methodology for subsurface characterization in saline aquifers that takes advantage of the density difference between the injected freshwater and the ambient saline groundwater. We combine high resolution forward modeling of density-driven flow with an efficient Bayesian geostatistical inversion algorithm.In the presence of a density difference between the injected and ambient fluids due to differences in salinity, the pressure field is coupled to the spatial distribution of salinity. This coupling renders the pressure field transient: the time evolution of the salinity distribution controls the density distribution which then leads to a time-evolving pressure distribution.We exploit this coupling between pressure and salinity to obtain an improved characterization of the permeability field without multiple pumping tests or additional salinity measurements. We show that the inversion performance improves with an increase in the mixed convection ratio–the relative importance between viscous forces from injection and buoyancy forces from density difference. Our work shows that measuring transient pressure data at multiple sampling points during freshwater injection into saline aquifers can be an effective strategy for aquifer characterization, key to the successful management of aquifer recharge.
      PubDate: 2017-05-17T11:20:48.52963-05:0
      DOI: 10.1002/2016WR020089
  • In situ characterization of wettability alteration and displacement
           mechanisms governing recovery enhancement due to low-salinity
    • Authors: M. Khishvand; A.H. Alizadeh, I. Oraki Kohshour, M. Piri, R.S. Prasad
      Abstract: A series of micro-scale core-flooding experiments were performed on reservoir core samples at elevated temperature and pressure conditions to develop better insights into wettability alteration and pore-scale displacement mechanisms taking place during low-salinity waterflooding. Two individual miniature core samples were cut from a preserved reservoir whole core, saturated to establish initial reservoir fluid saturation conditions, and subsequently waterflooded with low- and high-salinity brines. A third miniature sister core sample was also cut, solvent-cleaned, and subjected to a dynamic wettability restoration process (to reestablish native state wettability) and then a low-salinity waterflood. All samples were imaged during the experiments using a micro-CT scanner to obtain fluid occupancy maps and measure in-situ oil-water contact angles.The results of the experiments performed on the preserved core samples show a significantly improved performance of low-salinity waterflooding (LSWF) compared to that of high-salinity waterflooding (HSWF). Pore-scale contact angle measurements provide direct evidence of wettability alteration from weakly oil-wet toward weakly water-wet conditions during LSWF, whereas contact angles measured during HSWF remain unchanged. We believe that the reduction in oil-water contact angles toward increased water-wetness lowers the threshold water pressure needed to displace oil from some medium-sized pore elements. Contact angles measured during the dynamic wettability restoration process show an equilibrium wettability state very similar to the initial one observed in the preserved samples. This indicates that drilling fluid contaminants had a negligible effect on the reservoir rock wettability. The experimental results also reveal similarities between saturation trends for the preserved- and restored-LSWF tests.
      PubDate: 2017-05-17T11:20:39.803368-05:
      DOI: 10.1002/2016WR020191
  • 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
  • How are streamflow responses to the El Nino Southern Oscillation affected
           by watershed characteristics?
    • Authors: Joshua S. Rice; Ryan E. Emanuel
      Abstract: Understanding the factors that influence how global climate phenomena, such as the El-Nino Southern Oscillation (ENSO), affect streamflow behavior is an important area of research in the hydrologic sciences. While large scale patterns in ENSO-streamflow relationships have been thoroughly studied, and are relatively well-understood, information is scarce concerning factors that affect variation in ENSO responses from one watershed to another. To this end, we examined relationships between variability in ENSO activity and streamflow for 2731 watersheds across the conterminous U.S. from 1970 to 2014 using a novel approach to account for the intermediary role of precipitation. We applied an ensemble of regression techniques to describe relationships between variability in ENSO activity and streamflow as a function of watershed characteristics including: hydroclimate, topography, geomorphology, geographic location, land cover, soil characteristics, bedrock geology, and anthropogenic influences. We found that variability in watershed scale ENSO – streamflow relationships was strongly related to factors including: precipitation timing and phase, forest cover, and interactions between watershed topography and geomorphology. These, and other influential factors, share in common the ability to affect the partitioning and movement of water within watersheds. Our results demonstrate that the conceptualization of watersheds as signal filters for hydroclimate inputs, commonly applied to short-term rainfall-runoff responses, also applies to long-term hydrologic responses to sources of recurrent climate variability. These results also show that watershed processes, which are typically studied at relatively fine spatial scales, are also critical for understanding continental scale hydrologic responses to global climate.
      PubDate: 2017-05-16T05:40:40.256882-05:
      DOI: 10.1002/2016WR020097
  • 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
  • Improving degradation of benzotriazoles by applying chaotic advection in
           Managed Aquifer Recharge in randomly heterogeneous porous media
    • Authors: P. Rodríguez-Escales; D. Fernández-García, J. Drechsel, A. Folch, X. Sanchez-Vila
      Abstract: Improving degradation rates of emerging organic compounds (EOCs) in groundwater is still a challenge. Although their degradation is not fully understood, it has been observed that some substances are preferably degraded under specific redox conditions. The coupling of Managed Aquifer Recharge with soil aquifer remediation treatment, by placing a reactive layer containing organic matter at the bottom of the infiltration pond, is a promising technology to improve the rate of degradation of EOCs. Its success is based on assuming that recharged water and groundwater get well mixed, which is not always true. It has been demonstrated that mixing can be enhanced by inducing chaotic advection through extraction-injection-engineering. In this work we analyze how chaotic advection might enhance the spreading of redox conditions with the final aim of improving degradation of a mix of benzotriazoles: benzotriazole, 5-methyl-benzotriazole, and 5-chloro-benzotriazole. The degradation of the first two compounds was fastest under aerobic conditions whereas the third compound was best degraded under denitrification conditions. We developed a reactive transport model that describes how a recharged water rich in organic matter mixes with groundwater, how this organic matter is oxidized by different electron acceptors, and how the benzotriazoles are degraded attending for the redox state. The model was tested in different scenarios of recharge, both in homogenous and in heterogenous media. It was found that chaotic flow increases the spreading of the plume of recharged water. Consequently, different redox conditions coexist at a given time, facilitating the degradation of EOCs.
      PubDate: 2017-05-12T19:35:42.388198-05:
      DOI: 10.1002/2016WR020333
  • Raindrop interaction in interrill erosion for steady rainfalls: A
           probabilistic approach
    • Authors: A. Nouhou Bako; F. Darboux, F. James, C. Lucas
      Abstract: The main processes involved in interrill erosion are soil particles detachment and transport. Detachment is caused by shear stresses created by the impacts of raindrops. After sediments are lifted in the water layer, they are transported over a distance that depends on their settling velocities and the water flow velocity. This study calculates the probabilities of interactions between raindrops during soil detachment, and between raindrops and particles during their sedimentation. Raindrops are assumed to be consistent with the Poisson process and their densities are described by raindrop size distribution functions (Marshall-Palmer, Gamma and Lognormal laws). Interaction probabilities are calculated based on characteristic time and length scales of the shear stresses and the perturbation created by the raindrop impact inside the water layer.Under the hypothesis of a constant rainfall intensity, the results show that, during soil detachment, raindrops are almost independent. Thus, the total amount of soil detached by a rainfall is practically the sum of soil detached by its individual raindrops. Whereas during sediment transport, the probability of interaction between raindrops and settling particles is very high whatever the rainfall intensity and particle size, emphasizing the need to study further the interaction between raindrops and settling particles.
      PubDate: 2017-05-12T19:35:33.479914-05:
      DOI: 10.1002/2017WR020568
  • 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
  • High-resolution flow characterization close to the sediment-water
           interface in a run of the river reservoir
    • Authors: Andreas Brand; Christian Noss
      Abstract: A bistatic high-resolution acoustic profiler was used in order to characterize the lowermost boundary layer of a run of the river reservoir. The profiler allows determining the statistics of the three-dimensional flow field at a single point (sweet spot) as well as the measurement of the time averaged flow velocity profiles at 1 mm resolution around the sweet spot. Therefore, in addition to the flow statistics provided by single point acoustic Doppler profilers, mixing coefficients as well as production of turbulent kinetic energy can be calculated using a single device. Fitting of semiempirical relations to observed cospectra allowed eliminating artifacts as they result from coordinate system rotation during calculation of Reynolds stress profiles at millimeter resolution. While most parameters showed characteristics of a constant stress layer, length scales indicated anisotropy of the turbulent flow. Under these anisotropic near wall conditions, we found that the use of the commonly accepted Kolmogorov constants for the determination of dissipation rates using the inertial dissipation method is not valid any more. Instead, these constants vary with distance from the sediment water interface. We provide evidence that coefficients determined by numerical simulations are the appropriate choice also in field applications. In addition we resolved the viscous boundary layer close to the sediment-water interface in high resolution (1 mm) profiles and identified a double logarithmic layer above 1.5 cm at one location. The discrepancy of the scales as well as the double logarithmic layer suggests the existence of roughness elements upstream of the measurement sites.
      PubDate: 2017-05-12T10:35:37.002689-05:
      DOI: 10.1002/2016WR020203
  • 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
  • Validating a universal model of particle transport lengths with laboratory
           measurements of suspended grain motions
    • Authors: Suleyman Naqshband; Brandon McElroy, Robert C. Mahon
      Abstract: The mechanics of sediment transport are of fundamental importance for fluvio-deltaic morphodynamics. The present study focuses on quantifying particle motions and trajectories across a wide range of flow conditions. In particular, a continuous model is presented that predicts particle travel distances for saltation and suspension based on Rouse number and relative grain roughness. By utilizing a series of 8 video cameras in a plexiglass flume direct measurements of the distributions of particle travel distances (excursion lengths) were obtained. To this end, experiments were carried out in dark under black lights with fluorescent painted plastic and quartz sand particles. For relatively high Rouse numbers indicating bed load dominant transport regime (P ≥ 2.5), particle motion is governed by the effect of gravitational forces (settling velocities) and measured excursion lengths closely follow a Gaussian distribution. For P = 2.5, particle motion is equally subjected to both gravitational and turbulent forces. Consequently, measured excursion lengths exhibit a bi-modal distribution with two distinct peaks. As turbulent fluctuations increase and dominate particle motion over gravity (P 
      PubDate: 2017-05-08T08:52:04.005955-05:
      DOI: 10.1002/2016WR020024
  • Processes governing arsenic retardation on Pleistocene sediments:
           Adsorption experiments and model-based analysis
    • Authors: Bhasker Rathi; Harald Neidhardt, Michael Berg, Adam Siade, Henning Prommer
      Abstract: In many countries of south/south-east Asia, reliance on Pleistocene aquifers for the supply of low-arsenic groundwater has created the risk of inducing migration of high-arsenic groundwater from adjacent Holocene aquifers. Adsorption of arsenic onto mineral surfaces of Pleistocene sediments is an effective attenuation mechanism. However, little is known about the sorption under anoxic conditions, in particular the behavior of arsenite. We report the results of anoxic batch experiments investigating arsenite (1–25 µmol/L) adsorption onto Pleistocene sediments under a range of field-relevant conditions. The sorption of arsenite was non-linear and decreased with increasing phosphate concentrations (3–60 µmol/L) while pH (range 6–8) had no effect on total arsenic sorption. To simulate the sorption experiments, we developed surface complexation models of varying complexity. The simulated concentrations of arsenite, arsenate and phosphate were in good agreement for the isotherm and phosphate experiments while secondary geochemical processes affected the pH experiments. For the latter, the model-based analysis suggests that the formation of solution complexes between organic buffers and Mn(II) ions promoted the oxidation of arsenite involving naturally-occurring Mn-oxides. Upscaling the batch experiment model to a reactive transport model for Pleistocene aquifers demonstrates strong arsenic retardation and could have useful implications in the management of arsenic-free Pleistocene aquifers.
      PubDate: 2017-05-08T08:51:44.912294-05:
      DOI: 10.1002/2017WR020551
  • 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
  • Inferring hydraulic properties of alpine aquifers from the propagation of
           diurnal snowmelt signals
    • Authors: B. L. Kurylyk; M. Hayashi
      Abstract: Alpine watersheds source major rivers throughout the world and supply essential water for irrigation, human consumption, and hydroelectricity. Coarse depositional units in alpine watersheds can store and transmit significant volumes of groundwater and thus augment stream discharge during the dry season. These environments are typically data scarce, which has limited the application of physically-based models to investigate hydrologic sensitivity to environmental change.This study focuses on a coarse alpine talus unit within the Lake O'Hara watershed in the Canadian Rockies. We investigate processes controlling the hydrologic functioning of the talus unit using field observations and a numerical groundwater flow model driven with a distributed snowmelt model. The model hydraulic parameters are adjusted to investigate how these properties influence the propagation of snowmelt-induced diurnal signals. The model results expectedly demonstrate that diurnal signals at the talus outlet are progressively damped and lagged with lower hydraulic conductivity and higher specific yield. The simulations further indicate that the lag can be primarily controlled by a higher hydraulic conductivity upper layer, whereas the damping can be strongly influenced by a lower hydraulic conductivity layer along the base of the talus. The simulations specifically suggest that the talus slope can be represented as a two layer system with a high conductivity zone (0.02 m s−1) overlying a 10 cm thick lower conductivity zone (0.002 m s−1). This study demonstrates that diurnal signals can be used to elucidate the hydrologic functioning and hydraulic properties of shallow aquifers and thus aid in the parameterization of hydrological models.
      PubDate: 2017-05-08T08:51:28.464843-05:
      DOI: 10.1002/2016WR019651
  • A process-based insight into nonstationarity of the probability
           distribution of annual runoff
    • Authors: Cong Jiang; Lihua Xiong, Shenglian Guo, Jun Xia, Chong-Yu Xu
      Abstract: In this paper, a process-based analytical derivation approach is proposed to perform a nonstationary analysis for annual runoff distribution by taking into account the information of nonstationarities in both hydrological inputs and runoff generation processes. Under the Budyko hypothesis, annual runoff is simulated as a formulation of hydrological inputs (annual precipitation and potential evaporation) using an annual runoff model based on the Fu equation with a parameter w accounting for the runoff generation processes. The nonstationarity of the runoff generation process is captured by the dynamic Fu-equation parameter w. Then the multivariate joint probability distribution among the hydrological inputs, the Fu-equation parameter w, and the runoff model error k is constructed based on the nonstationary analysis for both the hydrological inputs and w. Finally, the annual runoff distribution is derived by integrating the multivariate joint probability density function. The derived distribution by the process-based analytical derivation approach performs well in fitting distributions of the annual runoffs from both the Yangtze River and Yellow River, China. For most study watersheds in these two basins, the derived annual runoff distributions are found to be nonstationary, due to the nonstationarities in hydrological inputs (mainly potential evaporation) or the Fu-equation parameter w.
      PubDate: 2017-05-08T08:51:23.564882-05:
      DOI: 10.1002/2016WR019863
  • Evaluating the role of watershed properties in long-term water balance
           through a Budyko equation based on two-stage partitioning of precipitation
    • Authors: Yin Tang; Dingbao Wang
      Abstract: In this paper, a four-parameter Budyko equation is derived for mean annual water balance by applying the proportionality relationship to a two-stage partitioning of precipitation. The four dimensionless parameters include the Horton index (H, defined as the ratio of evaporation to total wetting) and λ (the ratio of initial evaporation to total wetting) for slow runoff, and β (the ratio of initial wetting to total wetting) and γ (the ratio of total wetting to its potential) for fast runoff. The derived four-parameter equation balances model parsimony and representation of dominant hydrologic processes, and provides a framework to disentangle the roles of climate variability, vegetation, soil and topography on long-term water balance in gauged watersheds. The four parameters are determined for 165 watersheds by using observations of precipitation, potential evaporation, streamflow, and soil properties. Based on the principal component regression analysis, average time interval between rainfall events, slope, normalized difference vegetation index, and wilting point are identified as the dominant controlling factors on H and λ; saturated hydraulic conductivity and the difference between field capacity and residual soil moisture are identified as the dominant controlling factors on β; and γ is controlled by effective soil water storage capacity, frequency of rainfall events, and climate seasonality. The combination of four-parameter Budyko equation and the principal component regression equations provides a model to assess the long-term responses of evaporation and runoff to climate and watershed property changes in ungauged watersheds.
      PubDate: 2017-05-08T08:51:05.432207-05:
      DOI: 10.1002/2016WR019920
  • The Role of Rating Curve Uncertainty in Real-Time Flood Forecasting
    • Authors: David Ocio; Nataliya Le Vine, Ida Westerberg, Florian Pappenberger, Wouter Buytaert
      Abstract: Data assimilation has been widely tested for flood forecasting, although its use in operational systems is mainly limited to a simple statistical error correction. This can be due to the complexity involved in making more advanced formal assumptions about the nature of the model and measurement errors. Recent advances in the definition of rating curve uncertainty allow estimating a flow measurement error that includes both aleatory and epistemic uncertainties more explicitly and rigorously than in the current practice. The aim of this study is to understand the effect such a more rigorous definition of the flow measurement error has on real-time data assimilation and forecasting. This study, therefore, develops a comprehensive probabilistic framework that considers the uncertainty in model forcing data, model structure, and flow observations. Three common data assimilation techniques are evaluated: 1) Autoregressive error correction, 2) Ensemble Kalman Filter, and 3) Regularised Particle Filter, and applied to two locations in the flood-prone Oria catchment in the Basque Country, northern Spain. The results show that, although there is a better match between the uncertain forecasted and uncertain true flows, there is a low sensitivity for the threshold exceedances used to issue flood warnings. This suggests that a standard flow measurement error model, with a spread set to a fixed flow fraction, represents a reasonable trade-off between complexity and realism. Standard models are therefore recommended for operational flood forecasting for sites with well-defined stage–discharge curves that are based on a large range of flow observations.
      PubDate: 2017-05-08T08:50:58.935094-05:
      DOI: 10.1002/2016WR020225
  • Characterizing hyporheic exchange processes using high frequency
           electrical conductivity-discharge relationships on sub-hourly to
           interannual timescales
    • Authors: Joel G. Singley; Adam N. Wlostowski, Anna J. Bergstrom, Eric R. Sokol, Christa L. Torrens, Chris Jaros, Colleen E. Wilson, Patrick J. Hendrickson, Michael N. Gooseff
      Abstract: Concentration-discharge (C-Q) relationships are often used to quantify source water contributions and biogeochemical processes occurring within catchments, especially during discrete hydrological events. Yet, the interpretation of C-Q hysteresis is often confounded by complexity of the critical zone, such as numerous source waters and hydrochemical non-stationarity. Consequently, researchers must often ignore important runoff pathways and geochemical sources/sinks, especially the hyporheic zone because it lacks a distinct hydrochemical signature. Such simplifications limit efforts to identify processes responsible for the transience of C-Q hysteresis over time. To address these limitations, we leverage the hydrologic simplicity and long-term, high-frequency Q and electrical conductivity (EC) data from streams in the McMurdo Dry Valleys, Antarctica. In this two end-member system, EC can serve as a proxy for the concentration of solutes derived from the hyporheic zone. We utilize a novel approach to decompose loops into sub-hysteretic EC-Q dynamics to identify individual mechanisms governing hysteresis across a wide range of timescales. We find that hydrologic and hydraulic processes govern EC response to diel and seasonal Q variability and that the effects of hyporheic mixing processes on C-Q transience differ in short and long streams. We also observe that variable hyporheic turnover rates govern EC-Q patterns at daily to interannual timescales. Lastly, sub-hysteretic analysis reveals a period of interannual freshening of glacial meltwater streams related to the effects of unsteady flow on hyporheic exchange. The sub-hysteretic analysis framework we introduce may be applied more broadly to constrain the processes controlling C-Q transience and advance understanding of catchment evolution.
      PubDate: 2017-05-08T08:50:48.049312-05:
      DOI: 10.1002/2016WR019739
  • The effect of sampling effort on estimates of methane ebullition from peat
    • Authors: Jorge A. Ramirez; Andy J. Baird, Tom J. Coulthard
      Abstract: We investigated the effect of sample size and sampling duration on methane bubble flux (ebullition) estimates from peat using a computer model. A field scale (10 m), seasonal (> 100 days) simulation of ebullition from a two-dimensional structurally-varying peat profile was modelled at fine spatial resolution (1 mm × 1 mm). The spatial and temporal scale of this simulation was possible because of the computational efficiency of the reduced complexity approach that was implemented, and patterns of simulated ebullition were consistent with those found in the field and laboratory. The simulated ebullition from the peat profile suggested that decreases in peat porosity – which cause increases in gas storage – produce ebullition that becomes increasingly patchy in space and erratic in time. By applying different amounts of spatial and temporal sampling effort it was possible to determine the uncertainty in ebullition estimates from the peatland. The results suggest that traditional methods to measure ebullition can equally overestimate and underestimate flux by 20% and large ebullition events can lead to large overestimations of flux when sampling effort is low. Our findings support those of field studies, and we recommend that ebullition should be measured frequently (hourly to daily) and at many locations (n > 14).
      PubDate: 2017-05-08T08:50:38.892488-05:
      DOI: 10.1002/2017WR020428
  • Quantifying model structural error: Efficient Bayesian calibration of a
           regional groundwater flow model using surrogates and a data-driven error
    • Authors: Tianfang Xu; Albert J. Valocchi, Ming Ye, Feng Liang
      Abstract: Groundwater model structural error is ubiquitous, due to simplification and/or misrepresentation of real aquifer systems. During model calibration, the basic hydrogeological parameters may be adjusted to compensate for structural error. This may result in biased predictions when such calibrated models are used to forecast aquifer responses to new forcing. We investigate the impact of model structural error on calibration and prediction of a real-world groundwater flow model, using a Bayesian method with a data-driven error model [Xu and Valocchi, 2015a] to explicitly account for model structural error. The error-explicit Bayesian method jointly infers model parameters and structural error and thereby reduces parameter compensation. In this study, Bayesian inference is facilitated using high performance computing and fast surrogate models (based on machine learning techniques) as a substitute for the computationally expensive groundwater model. We demonstrate that with explicit treatment of model structural error, the Bayesian method yields parameter posterior distributions that are substantially different from those derived using classical Bayesian calibration that does not account for model structural error. We also found that the error-explicit Bayesian method gives significantly more accurate prediction along with reasonable credible intervals. Finally, through variance decomposition we provide a comprehensive assessment of prediction uncertainty contributed from parameter, model structure, and measurement uncertainty. The results suggest that the error-explicit Bayesian approach provides a solution to real-world modeling applications for which data support the presence of model structural error, yet model deficiency cannot be specifically identified or corrected.
      PubDate: 2017-05-08T08:50:33.034177-05:
      DOI: 10.1002/2016WR019831
  • Effects of spatially distributed sectoral water management on the
           redistribution of water resources in an integrated water model
    • Authors: Nathalie Voisin; Mohamad Hejazi, Ruby Leung, Lu Liu, Maoyi Huang, Hong-Yi Li, Teklu Tesfa
      Abstract: Realistic representations of sectoral water withdrawals and consumptive demands and their allocation to surface and groundwater sources are important for improving modeling of the integrated water cycle. To inform future model development, we enhance the representation of sectoral water management in a regional Earth system (ES) model with a spatially distributed allocation of sectoral water demands simulated by a regional integrated assessment (IA) model to surface and groundwater systems. The integrated modeling framework (IA-ES) is evaluated by analyzing the simulated regulated flow and sectoral supply deficit in major hydrologic regions of the conterminous U.S, which differ from ES studies looking at water storage variations. Decreases in historical supply deficit are used as metrics to evaluate IA-ES model improvement in representating the complex sectoral human activities for assessing future adaptation and mitigation strategies. We also assess the spatial changes in both regulated flow and unmet demands, for irrigation and non-irrigation sectors, resulting from the individual and combined additions of groundwater and return flow modules. Results show that groundwater use has a pronounced regional and sectoral effect by reducing water supply deficit. The effects of sectoral return flow exhibit a clear east-west contrast in the hydrologic patterns, so the return flow component combined with the IA sectoral demands is a major driver for spatial redistribution of water resources and water deficits in the U.S. Our analysis highlights the need for spatially distributed sectoral representation of water management to capture the regional differences in inter-basin redistribution of water resources and deficits.
      PubDate: 2017-05-08T08:35:37.70385-05:0
      DOI: 10.1002/2016WR019767
  • Forward and back diffusion through argillaceous formations
    • Authors: Minjune Yang; Michael D. Annable, James W. Jawitz
      Abstract: The exchange of solutes between aquifers and lower-permeability argillaceous formations is of considerable interest for solute and contaminant fate and transport. We present a synthesis of analytical solutions for solute diffusion between aquifers and single aquitard systems, validated in well-controlled experiments, and applied to several datasets from laboratory and field-scale problems with diffusion time and length scales ranging from 10−2-108 years and 10−2-102 m. One-dimensional diffusion models were applied using the method of images to consider the general cases of a finite aquitard bounded by two aquifers at the top and bottom, or a semi-infinite aquitard bounded by an aquifer. The simpler semi-infinite equations are appropriate for all domains with dimensionless relative diffusion length, ZD 
      PubDate: 2017-05-03T18:55:28.593317-05:
      DOI: 10.1002/2016WR019874
  • Geochemical evolution of the Critical Zone across variable time scales
           informs concentration-discharge relationships: Jemez River Basin Critical
           Zone Observatory
    • Authors: Jennifer C. McIntosh; Courtney Schaumberg, Julia Perdrial, Adrian Harpold, Angélica Vázquez-Ortega, Craig Rasmussen, David Vinson, Xavier Zapata-Rios, Paul D. Brooks, Thomas Meixner, Jon Pelletier, Louis Derry, Jon Chorover
      Abstract: This study investigates the influence of water, carbon and energy fluxes on solute production and transport through the Jemez Critical Zone (CZ) and impacts on C-Q relationships over variable spatial and temporal scales. Chemical depletion-enrichment profiles of soils, combined with regolith thickness and groundwater data indicate the importance to stream hydrochemistry of incongruent dissolution of silicate minerals during deep bedrock weathering, which is primarily limited by water fluxes, in this highly fractured, young volcanic terrain. Under high flow conditions (e.g., spring snowmelt), wetting of soil and regolith surfaces and presence of organic acids promote mineral dissolution and provide a constant supply of base cations, Si, and DIC to soil water and groundwater. Mixing of waters from different hydrochemical reservoirs in the near stream environment during ‘wet' periods leads to the chemostatic behavior of DIC, base cations, and Si in stream flow. Metals transported by organic matter complexation (i.e., Ge, Al) and/or colloids (i.e., Al) during periods of soil saturation and lateral connectivity to the stream display a positive relationship with Q. Variable Si-Q relationships, under all but the highest flow conditions, can be explained by non-conservative transport and precipitation of clay minerals, which influences long- versus short-term Si weathering fluxes. By combining measurements of the CZ obtained across different spatial and temporal scales, we were able to constrain weathering processes in different hydrological reservoirs that may be flushed to the stream during hydrologic events, thereby informing C-Q relationships.
      PubDate: 2017-05-02T19:35:37.307325-05:
      DOI: 10.1002/2016WR019712
  • Ephemeral and intermittent runoff generation processes in a low relief,
           highly weathered catchment
    • Authors: Margaret A. Zimmer; Brian L. McGlynn
      Abstract: Most field-based approaches that address runoff generation questions have been conducted in steep landscapes with shallow soils. Runoff generation processes in low relief landscapes with deep soils remain less understood. We addressed this by characterizing dominant runoff generating flowpaths by monitoring the timing and magnitude of precipitation, runoff, shallow soil moisture, and shallow and deep groundwater dynamics in a 3.3 hectare ephemeral-to-intermittent drainage network in the Piedmont region of North Carolina, USA. This Piedmont region is gently sloped with highly weathered soils characterized by shallow impeding layers due to decreases in saturated hydraulic conductivity with depth. Our results indicated two dominant catchment storage states driven by seasonal evapotranspiration. Within these states, distinct flowpaths were activated, resulting in divergent hydrograph recessions. Groundwater dynamics during precipitation events with different input characteristics and contrasting storage states showed distinct shallow and deep groundwater flowpath behavior could produce similar runoff magnitudes. During an event with low antecedent storage, activation of a shallow, perched, transient water table dominated runoff production. During an event with high antecedent storage, the deeper water table activated shallow flowpaths by rising into the shallow transmissive soil horizons. Despite these differing processes, the relationship between active surface drainage length (ASDL) and runoff was consistent. Hysteretic behavior between ASDL and runoff suggested that while seasonal ASDLs can be predicted based on runoff, the mechanisms and source areas producing flow can be highly variable and not easily estimated from runoff alone. These processes and flowpaths have significant implications for stream chemistry across seasons and storage states.
      PubDate: 2017-05-02T19:30:58.387939-05:
      DOI: 10.1002/2016WR019742
  • A two-dimensional analytical model of vapor intrusion involving vertical
    • Authors: Yijun Yao; Iason Verginelli, Eric M. Suuberg
      Abstract: In this work, we present an analytical chlorinated vapor intrusion (CVI) model that can estimate source-to-indoor air concentration attenuation by simulating two-dimensional (2-D) vapor concentration profile in vertically heterogeneous soils overlying a homogenous vapor source. The analytical solution describing the 2-D soil gas transport was obtained by applying a modified Schwarz–Christoffel mapping method. A partial field validation showed that the developed model provides results (especially in terms of indoor emission rates) in line with the measured data from a case involving a building overlying a layered soil. In further testing, it was found that the new analytical model can very closely replicate the results of three-dimensional (3-D) numerical models at steady state in scenarios involving layered soils overlying homogenous groundwater sources. By contrast, by adopting a two-layer approach (capillary fringe and vadose zone) as employed in the EPA implementation of the Johnson and Ettinger model, the spatially and temporally averaged indoor concentrations in the case of groundwater sources can be higher than the ones estimated by the numerical model up to two orders of magnitude. In short, the model proposed in this work can represent an easy-to-use tool that can simulate the subsurface soil gas concentration in layered soils overlying a homogenous vapor source while keeping the simplicity of an analytical approach that requires much less computational effort.
      PubDate: 2017-05-02T10:59:26.275321-05:
      DOI: 10.1002/2016WR020317
  • A geostatistics-informed hierarchical sensitivity analysis method for
           complex groundwater flow and transport modeling
    • Authors: Heng Dai; Xingyuan Chen, Ming Ye, Xuehang Song, John M. Zachara
      Abstract: Sensitivity analysis is an important tool for development and improvement of mathematical models, especially for complex systems with a high dimension of spatially correlated parameters. Variance-based global sensitivity analysis has gained popularity because it can quantify the relative contribution of uncertainty from different sources. However, its computational cost increases dramatically with the complexity of the considered model and the dimension of model parameters. In this study we developed a new sensitivity analysis method that integrates the concept of variance-based method with a hierarchical uncertainty quantification framework. Different uncertain inputs are grouped and organized into a multi-layer framework based on their characteristics and dependency relationships to reduce the dimensionality of the sensitivity analysis. A set of new sensitivity indices are defined for the grouped inputs using the variance decomposition method. Using this methodology, we identified the most important uncertainty source for a dynamic groundwater flow and solute transport model at the Department of Energy (DOE) Hanford site. The results indicate that boundary conditions and permeability field contribute the most uncertainty to the simulated head field and tracer plume, respectively. The relative contribution from each source varied spatially and temporally. By using a geostatistical approach to reduce the number of realizations needed for the sensitivity analysis, the computational cost of implementing the developed method was reduced to a practically manageable level. The developed sensitivity analysis method is generally applicable to a wide range of hydrologic and environmental problems that deal with high-dimensional spatially-distributed input variables.
      PubDate: 2017-04-29T12:00:11.82816-05:0
      DOI: 10.1002/2016WR019756
  • Hydrologic controls on junction angle of river networks
    • Authors: Milad Hooshyar; Arvind Singh, Dingbao Wang
      Abstract: The formation and growth of river channels and their network evolution are governed by the erosional and depositional processes operating on the landscape due to the movement of water. The branching angles, i.e., the angle between two adjoining channels, in drainage networks are important features related to the network topology and contain valuable information about the forming mechanisms of the landscape. Based on the channel networks extracted from 1 m Digital Elevation Models of 120 catchments with minimal human impacts across the United States, we show that the junction angles have two distinct modes with α1-≈49.5° and α2-≈75.0°. The observed angles are physically explained as the optimal angles that result in minimum energy dissipation and are linked to the exponent characterizing the slope-area curve. Our findings suggest that the flow regimes, debris-flow dominated or fluvial, have distinct characteristic angles which are functions of the scaling exponent of the slope-area curve. These findings enable us to understand the geomorphic signature of hydrologic processes on drainage networks and develop more refined landscape evolution models.
      PubDate: 2017-04-29T10:24:26.417507-05:
      DOI: 10.1002/2016WR020267
  • Ecohydrological interfaces as hotspots of ecosystem processes
    • Authors: Stefan Krause; Jörg Lewandowski, Nancy B. Grimm, David M. Hannah, Gilles Pinay, Karlie McDonald, Eugènia Martí, Alba Argerich, Laurent Pfister, Julian Klaus, Tom Battin, Scott T. Larned, Jacob Schelker, Jan Fleckenstein, Christian Schmidt, Michael O Rivett, Glenn Watts, Francesc Sabater, Albert Sorolla, Valentina Turk
      Abstract: The movement of water, matter, organisms, and energy can be altered substantially at ecohydrological interfaces, the dynamic transition zones that often develop within ecotones or boundaries between adjacent ecosystems. Interdisciplinary research over the last two decades has indicated that ecohydrological interfaces are often “hotspots” of ecological, biogeochemical, and hydrological processes and may provide refuge for biota during extreme events. Ecohydrological interfaces can have significant impact on global hydrological and biogeochemical cycles, biodiversity, pollutant removal, and ecosystem resilience to disturbance. The organisational principles (i.e., the drivers and controls) of spatially and temporally variable processes at ecohydrological interfaces are poorly understood and require the integrated analysis of hydrological, biogeochemical, and ecological processes. Our rudimentary understanding of the interactions between different drivers and controls critically limits our ability to predict complex system responses to change.In this paper we explore similarities and contrasts in the functioning of diverse freshwater ecohydrological interfaces across spatial and temporal scales. We use this comparison to develop an integrated, interdisciplinary framework, including a roadmap for analysing ecohydrological processes and their interactions in ecosystems. We argue that, in order to fully account for their non-linear process dynamics, ecohydrological interfaces need to be conceptualised as unique, spatially and temporally dynamic entities, which represents a step change from their current representation as boundary conditions at investigated ecosystems.
      PubDate: 2017-04-29T10:24:20.299483-05:
      DOI: 10.1002/2016WR019516
  • Evaluating climate and soil effects on regional soil moisture spatial
           variability using EOFs
    • Authors: Tiejun Wang; Trenton E. Franz, Ruopu Li, Jinsheng You, Martha D. Shulski, Chittaranjan Ray
      Abstract: Soil moisture is an important state variable in terrestrial water cycles; however, only few studies are available on regional soil moisture spatial variability (SMSV), which yielded inconsistent findings about regional controls on SMSV. Here, long-term soil moisture data were obtained from the Automated Weather Data Network and Soil Climate Analysis Network in three regions with different climate regimes across the continental U.S. Comprehensive datasets were compiled to examine regional controls on SMSV using the method of Empirical Orthogonal Function. One dominant spatial structure (EOF1) of soil moisture was found in the study regions, which explained over 75%, 67%, and 86% of the spatial variance in soil moisture in Nebraska, Utah, and the Southeast U.S., respectively. Despite the significant spatial variability in precipitation and potential evapotranspiration in all the study regions, the results showed that meteorological forcings had limited effects on regional SMSV in those regions with different climatic conditions, which differed from the traditional notion that SMSV is mainly controlled by meteorological forcings at the scale from 50 to 400 km. Instead, local factors related to soil (e.g., sand and clay fractions) were found to have significant correlations with EOF1, although the effects of other local factors (e.g., topography and vegetation) were generally negligible. This study provides strong field evidence that soil can exert much stronger impacts on regional SMSV than previously thought, which can override the effects of meteorological forcings. Future studies are still needed to elaborate on the relative roles of climate and soil in affecting regional SMSV.
      PubDate: 2017-04-29T10:02:32.572717-05:
      DOI: 10.1002/2017WR020642
  • Simulating seasonal variations of tile drainage discharge in an
           agricultural catchment
    • Authors: G. De Schepper; R. Therrien, J. C. Refsgaard, X. He, C. Kjaergaard, B. V. Iversen
      Abstract: Seasonal variations of tile drainage discharge were simulated in the 6 km2 Fensholt catchment, Denmark, with the coupled surface and subsurface HydroGeoSphere model. The catchment subsurface is represented in the model by 3 m of topsoil and clay, underlain by a heterogeneous distribution of sand and clay units. Two subsurface drainage networks were represented as nodal sinks. The spatial distribution of the heterogeneous units was generated stochastically and their hydraulic properties were calibrated to reproduce drainage discharge for one network and verified with drainage discharge for the other network. Simulated discharge was compared to that of another model for which the heterogeneous sand and clay units were replaced by a homogeneous unit, whose hydraulic conductivity was the mean value of the heterogeneous model. With the homogeneous model, drainage dynamics were correctly simulated but drainage discharge was less accurate compared to the heterogeneous model. Simulated discharge was also compared to that a larger scale model created with the MIKE SHE code, built with the same heterogeneous model. HydroGeoSphere and MIKE SHE generated drainage discharge that was significantly different, with better simulated groundwater dynamics data produced by HydroGeoSphere. Nodal sinks in HydroGeoSphere reproduced drain flow peaks more accurately. Calibration against drainage discharge data suggests that drain flow is controlled primarily by geological heterogeneities included in the model and, to a lesser extent, by the nature of the soil units located between the drains and ground surface.
      PubDate: 2017-04-27T18:31:01.861163-05:
      DOI: 10.1002/2016WR020209
  • The importance and challenge of hyporheic mixing
    • Authors: Erich T. Hester; M. Bayani Cardenas, Roy Haggerty, Sourabh V. Apte
      Abstract: The hyporheic zone is the interface beneath and adjacent to streams and rivers where surface water and groundwater interact. The hyporheic zone presents unique conditions for reaction of solutes from both surface water and groundwater, including reactions which depend upon mixing of source waters. Some models assume that hyporheic zones are well-mixed and conceptualize the hyporheic zone as a surface water-groundwater mixing zone. But what are the controls on and effects of hyporheic mixing? What specific mechanisms cause the relatively large (>∼1m) mixing zones suggested by subsurface solute measurements? In this commentary, we explore the various processes that might enhance mixing in the hyporheic zone relative to deeper groundwater, and pose the question whether the substantial mixing suggested by field studies may be due to the combination of fluctuating boundary conditions and multi-scale physical and chemical spatial heterogeneity. We encourage investigation of hyporheic mixing using numerical modeling and laboratory experiments to ultimately inform field investigations.
      PubDate: 2017-04-27T18:30:51.377076-05:
      DOI: 10.1002/2016WR020005
  • Evaluating the impacts of farmers' behaviors on a hypothetical
           agricultural water market based on double auction
    • Authors: Erhu Du; Ximing Cai, Nicholas Brozović, Barbara Minsker
      Abstract: Agricultural water markets are considered effective instruments to mitigate the impacts of water scarcity and to increase crop production. However, previous studies have limited understanding of how farmers' behaviors affect the performance of water markets. This study develops an agent-based model to explicitly incorporate farmers' behaviors, namely irrigation behavior (represented by farmers' sensitivity to soil water deficit λ) and bidding behavior (represented by farmers' rent seeking μ and learning rate β), in a hypothetical water market based on a double auction. The model is applied to the Guadalupe River Basin in Texas to simulate a hypothetical agricultural water market under various hydrological conditions. It is found that the joint impacts of the behavioral parameters on the water market are strong and complex. In particular, among the three behavioral parameters, λ affects the water market potential and its impacts on the performance of the water market are significant under most scenarios. The impacts of μ or β on the performance of the water market depend on the other two parameters. The water market could significantly increase crop production only when the following conditions are satisfied: (1) λ is small, and (2) μ is small and/or β is large. The first condition requires efficient irrigation scheduling, and the second requires well-developed water market institutions that provide incentives to bid true valuation of water permits.
      PubDate: 2017-04-27T18:28:30.723561-05:
      DOI: 10.1002/2016WR020287
  • Dynamic hyporheic and riparian flow path geometry through base flow
           recession in two headwater mountain stream corridors
    • Authors: Adam S. Ward; Noah M. Schmadel, Steven M. Wondzell, Michael N. Gooseff, Kamini Singha
      Abstract: The hydrologic connectivity between streams and their valley bottoms (stream corridor) is a critical determinant of their ecological function. Ecological functions are known to be spatially and temporally variable, but spatial dimensions of the problem are not easily quantified and thus they are usually overlooked. To estimate the spatial patterns of connectivity, and how connectivity varies with changes in discharge, we developed the Hyporheic Potential Model. We used the model to interpret a series of solute tracer injections in two headwater mountain streams with contrasting valley bottom morphologies to estimate connectivity in the stream corridor. The distributions of flowpath origination locations and the lengths of hyporheic flow paths appear to vary with baseflow recession, even in cases where transport timescales are apparently unchanged. The modeled distribution of origination locations further allowed us to define a spatial analogue to the temporal window of detection associated with solute tracer studies, and enables assessment of connectivity dynamics between streams and their corridors. Altogether, the reduced complexity Hyporheic Potential Model provides an easy way anticipate the spatial distribution and origination locations of hyporheic flow paths from a basic understanding of the valley bottom characteristics and solute transport timescales.
      PubDate: 2017-04-26T11:30:35.745422-05:
      DOI: 10.1002/2016WR019875
  • Rainfall variability in the Himalayan orogen and its relevance to erosion
    • Authors: Eric Deal; Anne-Catherine Favre
      Abstract: Rainfall is an important driver of erosion processes. The mean rainfall rate is often used to account for the erosive impact of a particular climate. However, for some erosion processes, erosion rate is a nonlinear function of rainfall, e.g. due to a threshold for erosion. When this is the case, it is important to take into account the full distribution of rainfall, instead of just the mean. In light of this, we have characterized the variability of daily rainfall over the Himalayan orogen using high spatial and temporal resolution rainfall data sets. We find significant variations in rainfall variability over the Himalayan orogen, with increasing rainfall variability to the west and north of the orogen. By taking into account variability of rainfall in addition to mean rainfall rate, we find a pattern of rainfall that, from a geomorphological perspective, is significantly different from mean rainfall rate alone. Using these findings we argue that short-term rainfall variability may help explain observed short and long term erosion rates in the Himalayan orogen.
      PubDate: 2017-04-26T11:21:42.662329-05:
      DOI: 10.1002/2016WR020030
  • Technical report: The design and evaluation of a basin-scale wireless
           sensor network for mountain hydrology
    • Authors: Ziran Zhang; Steven D. Glaser, Roger C. Bales, Martha Conklin, Robert Rice, Danny G. Marks
      Abstract: A network of sensors for spatially representative water-balance measurements was developed and deployed across the 2000 km2 snow-dominated portion of the upper American River basin, primarily to measure changes in snowpack and soil-water storage, air temperature and humidity. This wireless sensor network (WSN) consists of 14 sensor clusters, each with 10 measurement nodes that were strategically placed within a 1­km2 area, across different elevations, aspects, slopes and canopy covers. Compared to existing operational sensor installations, the WSN reduces hydrologic uncertainty in at least three ways. First, redundant measurements improved estimation of lapse rates for air and dew-point temperature. Second, distributed measurements captured local variability and constrained uncertainty in air and dew-point temperature, snow accumulation and derived hydrologic attributes important for modeling and prediction. Third, the distributed relative-humidity measurements offer a unique capability to monitor upper-basin patterns in dew-point temperature and characterize elevation gradient of water vapor-pressure deficit across steep, variable topography. Network statistics during the first year of operation demonstrated that the WSN was robust for cold, wet and windy conditions in the basin. The electronic technology used in the WSN reduced adverse effects, such as high current consumption, multipath signal fading and clock drift, seen in previous remote WSNs.
      PubDate: 2017-04-26T11:16:04.63207-05:0
      DOI: 10.1002/2016WR019619
  • Concentration-discharge relationships in headwater streams of the Sierra
           Nevada, California
    • Authors: Carolyn T. Hunsaker; Dale W. Johnson
      Abstract: We examined streamwater concentration-discharge relationships for eight small, forest watersheds ranging in elevation from 1,485 to 2,465 m in the southern Sierra Nevada. These headwater streams revealed nearly chemostatic behavior by current definitions for K+, Ca2+, Mg2+, Na+, Cl- and SO42- in most cases but not for NH4+. NO3-, or ortho-P. The latter ions were somewhat enriched during high flows. All ions studied showed a dilution process at lower flows (< 50 l sec−1) with the concentration-discharge relationship being more chemostatic at higher flows. While previous studies in the Sierra Nevada have reported peak concentrations of NH4+, NO3-, and SO42- during snowmelt, the headwater systems of the Kings River Experimental Watersheds experience peak concentrations of these ions during the fall rains after the dry summer. These forested watersheds span the rain-snow transition zone, are 49 to 228 ha in size, and have soils derived from granite. A statistically significant relationship between soils and streamwater concentrations for ortho-P, Ca2+, and Na+ strongly suggests that soil chemistry has a major influence on streamwater chemistry. Factors controlling streamwater NH4+, NO3-, and SO42- concentrations are less clear, but one possible source of spikes in these ions during storm events is input from O-horizon runoff where high concentrations were measured. Overall, streamwater concentation-discharge relationships for these Sierran watersheds are similar to those found in other watershed systems (nearly chemostatic); however, the dominant processes controlling these relationships are probably localized because of different watershed characteristics like soil chemistry, vegetation cover, hydrologic flow paths, and weather patterns.
      PubDate: 2017-04-25T10:50:47.401121-05:
      DOI: 10.1002/2016WR019693
  • Similarities and differences between three coexisting spaceborne radars in
           global rainfall and snowfall estimation
    • Authors: Guoqiang Tang; Yixin Wen, Jinyu Gao, Di Long, Yingzhao Ma, Wei Wan, Yang Hong
      Abstract: Precipitation is one of the most important components in the water and energy cycles. Radars are considered the best available technology for observing the spatial distribution of precipitation either from the ground since the 1980s or from space since 1998. This study, for the first time ever, compares and evaluates the only three existing spaceborne precipitation radars, i.e., the Ku-band precipitation radar (PR), the W-band Cloud Profiling Radar (CPR), and the Ku/Ka-band Dual-frequency Precipitation Radar (DPR). The three radars are matched up globally and intercompared in the only period which they co-exist: 2014-2015. In addition, for the first time ever, TRMM PR and GPM DPR are evaluated against hourly rain gauge data in Mainland China. Results show that DPR and PR agree with each other and correlate very well with gauges in Mainland China. However, both show limited performance in the Tibetan Plateau (TP) known as the Earth's third pole. DPR improves light precipitation detectability, when compared with PR, whereas CPR performs best for light precipitation and snowfall. DPR snowfall has the advantage of higher sampling rates than CPR; however, its accuracy needs to be improved further. The future development of spaceborne radars is also discussed in two complementary categories: (1) multi-frequency radar instruments on a single platform and (2) constellations of many small cube radar satellites, for improving global precipitation estimation. This comprehensive intercomparison of PR, CPR, and DPR sheds light on spaceborne radar precipitation retrieval and future radar design.
      PubDate: 2017-04-21T11:32:41.24204-05:0
      DOI: 10.1002/2016WR019961
  • A modeling approach to identify the effective forcing exerted by wind on a
           pre-alpine lake surrounded by a complex topography
    • Authors: G. Valerio; A. Cantelli, P. Monti, G. Leuzzi
      Abstract: The representation of spatial wind distribution is recognized as a serious difficulty when modeling the hydrodynamics of lakes surrounded by a complex topography. To address this issue, we propose to force a 3D lake model with the wind field simulated by a high-resolution atmospheric model, considering as a case study a 61 km2 pre-alpine lake surrounded by mountain ranges that reach 1800 m above the lake's surface, where a comprehensive data set was available in the stratified season. The improved distributed description of the wind stress over the lake surface led to a significant enhancement in the representation of the main basin-scale internal wave motions, and hence provided a reference solution to test the use of simplified approaches. Moreover, the analysis of the power exerted by the computed wind field enabled us to identify measuring stations that provide suitable wind data to be applied uniformly on the lake surface in long-term simulations. Accordingly, the proposed methodology can contribute to reducing the uncertainties associated with the definition of wind forcing for modeling purposes and can provide a rational criterion for installing representative measurement locations in pre-alpine lakes.
      PubDate: 2017-04-19T13:53:24.408967-05:
      DOI: 10.1002/2016WR020335
  • Machine learning algorithms for modeling groundwater level changes in
           agricultural regions of the United States
    • Authors: S. Sahoo; T. A. Russo, J. Elliott, I. Foster
      Abstract: Climate, groundwater extraction, and surface water flows have complex nonlinear relationships with groundwater level in agricultural regions. To better understand the relative importance of each driver, and predict groundwater level change, we develop a new ensemble modeling framework based on spectral analysis, machine learning, and uncertainty analysis, as an alternative to complex and computationally expensive physical models. We apply and evaluate this new approach in the context of two aquifer systems supporting agricultural production in the United States: the High Plains aquifer (HPA) and the Mississippi River Valley alluvial aquifer (MRVA). We select input datasets by using a combination of mutual information, genetic algorithms, and lag analysis, and then use the selected datasets in a Multilayer Perceptron network architecture to simulate seasonal groundwater level change. As expected, model results suggest that irrigation demand has the highest influence on groundwater level change for a majority of the wells. The subset of groundwater observations not used in model training or cross-validation correlates strongly (R > 0.8) with model results for 88% and 83% of the wells in the HPA and MRVA, respectively. In both aquifer systems, the error in the modeled cumulative groundwater level change during testing (2003 to 2012) was less than 2 m over a majority of the area. We conclude that our modeling framework can serve as an alternative approach to simulating groundwater level change and water availability, especially in regions where subsurface properties are unknown.
      PubDate: 2017-04-19T13:53:16.126975-05:
      DOI: 10.1002/2016WR019933
  • Changes in floodplain inundation under nonstationary hydrology for an
           adjustable, alluvial river channel
    • Authors: B.C. Call; P. Belmont, J.C. Schmidt, P. R. Wilcock
      Abstract: Predicting the frequency and aerial extent of flooding in river valleys is essential for infrastructure design, environmental management, and risk assessment. Conventional flood prediction relies on assumptions of stationary flood distributions and static channel geometries. However, non-stationary flow regimes are increasingly observed and changes in flow and/or sediment supply are known to alter the geometry and flood conveyance of alluvial channels. Systematic changes in flows and/or channel geometry may amplify or attenuate the frequency and/or extent of flood inundation in unexpected ways. We present a stochastic, reduced complexity model to investigate such dynamics. The model routes a series of annual peak-discharges through a simplified reach-averaged channel-floodplain cross-section. Channel width, depth, and slope are permitted to adjust annually by a user-specified fraction towards equilibrium geometries predicted based on each year's peak-discharge and sediment supply. Modeled channel adjustments are compared with empirical observations for two rivers in Minnesota, USA that have experienced multiple large floods over the past six-years. The model is then run using six-hypothetical scenarios simulating non-stationary flow regimes with temporal adjustments in the mean and/or variance of the governing peak-flow distributions. Each scenario is run repeatedly while varying parameters that control the amount of fractional adjustment that channel geometries can make annually. Results indicate that the intra-annual mean horizontal width of floodplain inundation primarily depends on the governing peak-flow distribution's coefficient of variation, but the intra-annual frequency of floodplain inundation (i.e. the fraction of modeled years with inundation) primarily depends on the amount of channel adjustment permitted annually.
      PubDate: 2017-04-19T13:38:10.547136-05:
      DOI: 10.1002/2016WR020277
  • Physical effects of thermal pollution in lakes
    • Authors: Love Råman Vinnå; Alfred Wüest, Damien Bouffard
      Abstract: Anthropogenic heat emissions into inland waters influence water temperature and affect stratification, heat and nutrient fluxes, deep-water renewal and biota. Given the increased thermal stress on these systems by growing cooling demands of riparian/costal infrastructures in combination with climate warming, the question arises on how to best monitor and manage these systems. In this study, we investigate local and system-wide physical effects on the medium-sized perialpine Lake Biel (Switzerland), influenced by point-source cooling-water emission from an upstream nuclear power plant (heat emission ∼700 MW, ∼18 W m−2 lake-wide). We use one-dimensional (SIMSTRAT) and three-dimensional (Delft3D-Flow) hydrodynamic numerical simulations and provide model resolution guidelines for future studies of thermal pollution. The effects on Lake Biel by the emitted excess heat are summarized as: (i) clear seasonal trend in temperature increase, locally up to 3.4°C and system-wide volume-mean ∼0.3°C, which corresponds to one decade of regional surface water climate warming, (ii) the majority of supplied thermal pollution (∼60%) leaves this short residence time (∼58 days) system via the main outlet, whereas the remaining heat exits to the atmosphere, (iii) increased length of stratified period due to the stabilizing effects of additional heat, (iv) system-wide effects such as warmer temperature, prolonged stratified period and river-caused epilimnion flushing are resolved by both models whereas local raised temperature and short-circuiting was only identifiable with the three-dimensional model approach. This model-based method provides an ideal tool to assess man-made impacts on lakes and their downstream outflows.
      PubDate: 2017-04-13T11:33:39.247943-05:
      DOI: 10.1002/2016WR019686
  • Ambient groundwater flow diminishes nitrate processing in the hyporheic
           zone of streams
    • Authors: Morvarid Azizian; Fulvio Boano, Perran L.M. Cook, Russell L. Detwiler, Megan A. Rippy, Stanley B. Grant
      Abstract: Modeling and experimental studies demonstrate that ambient groundwater flow reduces the flux of water through the hyporheic zone, but the implications of this observation for stream N-cycling is not yet clear. Here we utilize a simple process-based model (the Pumping and Streamline Segregation or PASS model) to evaluate N-cycling over two scales of hyporheic exchange (fluvial ripples and riffle-pool sequences), ten ambient groundwater and stream flow scenarios (five gaining and losing conditions and two stream discharges), and three biogeochemical settings (identified based on a principal component analysis of previously published measurements in streams throughout the U.S.). Model-data comparisons indicate that our model provides realistic estimates for direct denitrification of stream nitrate, but over-predicts nitrification and coupled nitrification-denitrification. Riffle-pool sequences are responsible for most of the N-processing, despite the fact that fluvial ripples generate 3 to 11 times more hyporheic exchange flux. Across all scenarios, hyporheic exchange flux and the Damköhler Number emerge as primary controls on stream N-cycling; the former regulates trafficking of nutrients and oxygen across the sediment-water interface, while the latter quantifies the relative rates of organic carbon mineralization and advective transport in streambed sediments. Vertical groundwater flux modulates both of these master variables in ways that tend to diminish stream N-cycling. Thus, anthropogenic perturbations of ambient groundwater flows (e.g., by urbanization, agricultural activities, groundwater mining, and/or climate change) may compromise some of the key ecosystem services provided by streams.
      PubDate: 2017-04-11T08:15:34.118278-05:
      DOI: 10.1002/2016WR020048
  • Little impact of Three Gorges Dam on recent decadal lake decline across
           China's Yangtze Plain
    • Authors: Jida Wang; Yongwei Sheng, Yoshihide Wada
      Abstract: The ubiquitous lakes across China's Yangtze Plain (YP) are indispensable freshwater resources sustaining ecosystems and socioeconomics for nearly half a billion people. Our recent survey revealed a widespread net decline in the total YP lake inundation area during 2000–2011 (a cumulative decrease of ∼10%), yet its mechanism remains contentious. Here, we uncover the impacts of climate variability and anthropogenic activities including i) Yangtze flow and sediment alterations by the Three Gorges Dam (TGD) and ii) human water consumption in agricultural, industrial, and domestic sectors throughout the downstream Yangtze Basin. Results suggest that climate variability is the dominant driver of this decadal lake decline, whereas studied human activities, despite varying seasonal impacts that peak in fall, contribute marginal fraction (∼10–20% or less) to the interannual lake area decrease. Given that the TGD impacts on the total YP lake area and its seasonal variation are both under ∼5%, we also dismiss the speculation that the TGD might be responsible for evident downstream climate change by altering lake surface extent and thus open water evaporation. Nevertheless, anthropogenic impacts exhibited a strengthening trend during the past decade. Although the TGD has reached its full-capacity water regulation, the negative impacts of human water consumption and TGD-related net channel erosion are already comparable to that of TGD's flow regulation, and may continue to grow as crucial anthropogenic factors to future YP lake conservation.
      PubDate: 2017-04-06T15:06:18.231566-05:
      DOI: 10.1002/2016WR019817
  • Let hydrologists learn the latest computer science by working with
           Research Software Engineers (RSEs) and not reinvent the waterwheel
           ourselves. A comment to “Most Computational Hydrology is not
           Reproducible, so is it Really Science?”
    • Authors: R. W. Hut; N. C. van de Giesen, N. Drost
      Abstract: The suggestions by Hutton et al. might not be enough to guarantee reproducible computational hydrology. Archiving software code and research data alone will not be enough. We add to the suggestion of Hutton et al. that hydrologists not only document their (computer) work, but that hydrologists use the latest best practices in designing research software, most notably the use of containers and open interfaces. To make sure hydrologists know of these best practices we urge close collaboration with Research Software Engineers (RSEs).
      PubDate: 2017-03-31T18:10:33.767783-05:
      DOI: 10.1002/2017WR020665
  • 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
  • Groundwater similarity across a watershed derived from time-warped and
           flow-corrected time series
    • Authors: M. Rinderer; B. L. McGlynn, H.J. van Meerveld
      Abstract: Information about catchment-scale groundwater dynamics is necessary to understand how catchments store and release water and why water quantity and quality varies in streams. However, groundwater level monitoring is often restricted to a limited number of sites. Knowledge of the factors that determine similarity between monitoring sites can be used to predict catchment-scale groundwater storage and connectivity of different runoff source areas. We used distance-based and correlation-based similarity measures to quantify the spatial and temporal differences in shallow groundwater similarity for 51 monitoring sites in a Swiss pre-alpine catchment. The 41 months long time series were pre-processed using dynamic time-warping and a flow-corrected time transformation to account for small timing differences and bias towards low-flow periods. The mean distance-based groundwater similarity was correlated to topographic indices, such as upslope contributing area, Topographic Wetness Index and local slope. Correlation-based similarity was less related to landscape position but instead revealed differences between seasons. Analysis of Variance and Partial Mantel tests showed that landscape position, represented by the Topographic Wetness Index, explained 52% of the variability in mean distance-based groundwater similarity, while spatial distance, represented by the Euclidean distance, explained only 5%. The variability in distance-based similarity and correlation-based similarity between groundwater and streamflow time series was significantly larger for midslope locations than for other landscape positions. This suggests, that groundwater dynamics at these midslope sites, which are important in order to understand runoff source areas and hydrological connectivity at the catchment-scale, are most difficult to predict. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-02T12:30:25.364245-05:
      DOI: 10.1002/2016WR019856
  • Issue Information
    • Pages: 3523 - 3526
      PubDate: 2017-06-17T18:03:08.107918-05:
      DOI: 10.1002/wrcr.22252
  • Geological storage of captured carbon dioxide as a large-scale carbon
           mitigation option
    • Authors: Michael A. Celia
      Pages: 3527 - 3533
      Abstract: Carbon capture and storage (CCS), involves capture of CO2 emissions from power plants and other large stationary sources and subsequent injection of the captured CO2 into deep geological formations. This is the only technology currently available that allows continued use of fossil fuels while simultaneously reducing emissions of CO2 to the atmosphere. Although the subsurface injection and subsequent migration of large amounts of CO2 involve a number of challenges, many decades of research in the earth sciences, focused on fluid movement in porous rocks, provides a strong foundation on which to analyze the system. These analyses indicate that environmental risks associated with large CO2 injections appear to be manageable.
      PubDate: 2017-05-02T10:11:00.688142-05:
      DOI: 10.1002/2017WR020841
  • Water and life from snow: A trillion dollar science question
    • Authors: Matthew Sturm; Michael A. Goldstein, Charles Parr
      Pages: 3534 - 3544
      Abstract: Snow provides essential resources/services in the form of water for human use, and climate regulation in the form of enhanced cooling of the Earth. In addition, it supports a thriving winter outdoor recreation industry. To date, the financial evaluation of the importance of snow is incomplete and hence the need for accelerated snow research is not as clear as it could be. With snow cover changing worldwide in several worrisome ways, there is pressing need to determine global, regional, and local rates of snow cover change, and to link these to financial analyses that allow for rational decision making, as risks related to those decisions involve trillions of dollars.
      PubDate: 2017-05-02T10:01:12.102274-05:
      DOI: 10.1002/2017WR020840
  • Science, politics, and rationality in a partisan era
    • Authors: James W. Kirchner
      Pages: 3545 - 3549
      Abstract: Science plays an essential role in public policy by outlining the factual foundations of policy debates. As a result, science often becomes a political football, with partisans dismissing or misrepresenting scientific findings that conflict with their political views. Here I argue that scientists can most effectively speak out, not as activists supporting particular political causes, but instead as advocates for a fundamentally rational public discourse, one that starts from the facts—not from whatever one might choose to believe—and then explores how society should respond to the challenges that they pose.
      PubDate: 2017-05-02T10:01:00.695667-05:
      DOI: 10.1002/2017WR020882
  • The food-energy-water nexus: Transforming science for society
    • Authors: Bridget R. Scanlon; Ben L. Ruddell, Patrick M. Reed, Ruth I. Hook, Chunmiao Zheng, Vince C. Tidwell, Stefan Siebert
      Pages: 3550 - 3556
      Abstract: Emerging interdisciplinary science efforts are providing new understanding of the interdependence of food, energy, and water (FEW) systems. These science advances, in turn, provide critical information for coordinated management to improve the affordability, reliability, and environmental sustainability of FEW systems. Here we describe the current state of the FEW nexus and approaches to managing resource conflicts through reducing demand and increasing supplies, storage, and transport. Despite significant advances within the past decade, there are still many challenges for the scientific community. Key challenges are the need for interdisciplinary science related to the FEW nexus; ground-based monitoring and modeling at local-to-regional scales; incorporating human and institutional behavior in models; partnerships among universities, industry, and government to develop policy relevant data; and systems modeling to evaluate trade-offs associated with FEW decisions.
      PubDate: 2017-05-04T06:15:47.508032-05:
      DOI: 10.1002/2017WR020889
  • Modeling blowing snow accumulation downwind of an obstruction: The Ohara
           Eulerian particle distribution equation
    • Authors: N. J. Kinar
      Pages: 3557 - 3564
      Abstract: An equation was proposed to model the height of blowing snow accumulation downwind of an obstacle such as vegetation, a snow fence, a building, or a topographic feature. The equation does not require aerodynamic flow condition parameters such as wind speed, allowing for the spatial distribution of snow to be determined at locations where meteorological data is not available. However, snow particle diffusion, drift, and erosion coefficients must be estimated for application of the equation. These coefficients can be used to provide insight into the relative magnitude of blowing snow processes at a field location. Further research is required to determine efficient methods for coefficient estimation. The equation could be used with other models of wind-transported snow to predict snow accumulation downwind of an obstacle without the need for wind speed adjustments or correction equations. Applications for this equation include the design of snow fences, and the use of this equation with other hydrological models to predict snow distribution, climate change, drought, flooding, and avalanches.
      PubDate: 2017-05-09T23:50:27.372681-05:
      DOI: 10.1002/2017WR020731
  • Uncertainty analysis and risk-based design of detention basin without
           damage function
    • Authors: Yeou-Koung Tung
      Pages: 3576 - 3598
      Abstract: Risk-based analysis provides an economically defensible framework for determining the optimal design of hydrosystems with the minimum total cost including project cost (installation plus operation/maintenance/repair) and failure-induced expected damage cost. However, failure-related damage function with good quality may not be widely available in practical applications for assessing annual expected damage cost. In addition to aleatory uncertainty representing natural randomness of hydrologic events, there exists a variety of epistemic uncertainties due to knowledge deficiency from the use of inadequate models, inaccurate model parameters, etc. The presence of epistemic uncertainties could affect the loads and capacity of hydrosystem facilities which, in turn, would affect the value of failure-induced physical performance indicators. Using detention basin design as an example, this paper presents a systematic framework to integrate aleatory and epistemic uncertainties for the risk-based design under the condition of no monetary damage function. For illustration, aleatory uncertainty due to randomness of rainfall intensity and epistemic uncertainties caused by runoff coefficient and curve number are considered in risk-based design of an example detention basin.
      PubDate: 2017-05-02T10:10:24.30542-05:0
      DOI: 10.1002/2016WR020079
  • Noble gas signatures in the Island of Maui, Hawaii: Characterizing
           groundwater sources in fractured systems
    • Authors: Yi Niu; M. Clara Castro, Chris M. Hall, Stephen B. Gingerich, Martha A. Scholl, Rohit B. Warrier
      Pages: 3599 - 3614
      Abstract: Uneven distribution of rainfall and freshwater scarcity in populated areas in the Island of Maui, Hawaii, renders water resources management a challenge in this complex and ill-defined hydrological system. A previous study in the Galapagos Islands suggests that noble gas temperatures (NGTs) record seasonality in that fractured, rapid infiltration groundwater system rather than the commonly observed mean annual air temperature (MAAT) in sedimentary systems where infiltration is slower thus, providing information on recharge sources and potential flow paths. Here we report noble gas results from the basal aquifer, springs, and rainwater in Maui to explore the potential for noble gases in characterizing this type of complex fractured hydrologic systems. Most samples display a mass-dependent depletion pattern with respect to surface conditions consistent with previous observations both in the Galapagos Islands and Michigan rainwater. Basal aquifer and rainwater noble gas patterns are similar and suggest direct, fast recharge from precipitation to the basal aquifer. In contrast, multiple springs, representative of perched aquifers, display highly variable noble gas concentrations suggesting recharge from a variety of sources. The distinct noble gas patterns for the basal aquifer and springs suggest that basal and perched aquifers are separate entities. Maui rainwater displays high apparent NGTs, incompatible with surface conditions, pointing either to an origin at high altitudes with the presence of ice or an ice-like source of undetermined origin. Overall, noble gas signatures in Maui reflect the source of recharge rather than the expected altitude/temperature relationship commonly observed in sedimentary systems.
      PubDate: 2017-05-02T10:10:15.147748-05:
      DOI: 10.1002/2016WR020172
  • Continuous monitoring of snowpack dynamics in alpine terrain by
           aboveground neutron sensing
    • Authors: Paul Schattan; Gabriele Baroni, Sascha E. Oswald, Johannes Schöber, Christine Fey, Christoph Kormann, Matthias Huttenlau, Stefan Achleitner
      Pages: 3615 - 3634
      Abstract: The characteristics of an aboveground cosmic-ray neutron sensor (CRNS) are evaluated for monitoring a mountain snowpack in the Austrian Alps from March 2014 to June 2016. Neutron counts were compared to continuous point-scale snow depth (SD) and snow-water-equivalent (SWE) measurements from an automatic weather station with a maximum SWE of 600 mm (April 2014). Several spatially distributed Terrestrial Laser Scanning (TLS)-based SD and SWE maps were additionally used. A strong nonlinear correlation is found for both SD and SWE. The representative footprint of the CRNS is in the range of 230–270 m. In contrast to previous studies suggesting signal saturation at around 100 mm of SWE, no complete signal saturation was observed. These results imply that CRNS could be transferred into an unprecedented method for continuous detection of spatially averaged SD and SWE for alpine snowpacks, though with sensitivity decreasing with increasing SWE. While initially different functions were found for accumulation and melting season conditions, this could be resolved by accounting for a limited measurement depth. This depth limit is in the range of 200 mm of SWE for dense snowpacks with high liquid water contents and associated snow density values around 450 kg m−3 and above. In contrast to prior studies with shallow snowpacks, interannual transferability of the results is very high regardless of presnowfall soil moisture conditions. This underlines the unexpectedly high potential of CRNS to close the gap between point-scale measurements, hydrological models, and remote sensing of the cryosphere in alpine terrain.
      PubDate: 2017-05-02T10:10:31.615724-05:
      DOI: 10.1002/2016WR020234
  • A Kolmogorov-Brutsaert structure function model for evaporation into a
           turbulent atmosphere
    • Authors: Gabriel Katul; Heping Liu
      Pages: 3635 - 3644
      Abstract: In 1965, Brutsaert proposed a model that predicted mean evaporation rate E¯ from rough surfaces to scale with the 3/4 power law of the friction velocity (u∗) and the square-root of molecular diffusivity (Dm) for water vapor. In arriving at these results, a number of assumptions were made regarding the surface renewal rate describing the contact durations between eddies and the evaporating surface, the diffusional mass process from the surface into eddies, and the cascade of turbulent kinetic energy sustaining the eddy renewal process itself. The working hypothesis explored here is that E¯∼Dmu∗3/4 is a direct outcome of the Kolmogorov scaling for inertial subrange eddies modified to include viscous cutoff thereby bypassing the need for a surface renewal assumption. It is demonstrated that Brutsaert's model for E¯ may be more general than its original derivation implied.
      PubDate: 2017-05-02T10:10:36.706005-05:
      DOI: 10.1002/2016WR020006
  • Mineralogical and transport controls on the evolution of porous media
           texture using direct numerical simulation
    • Authors: Sergi Molins; David Trebotich, Gregory H. Miller, Carl I. Steefel
      Pages: 3645 - 3661
      Abstract: The evolution of porous media due to mineral dissolution and precipitation can change the bulk properties of subsurface materials. The pore-scale structure of the media, including its physical and mineralogical heterogeneity, exerts controls on porous media evolution via transport limitations to reactive surfaces and mineral accessibility. Here we explore how these controls affect the evolution of the texture in porous media at the pore scale. For this purpose, a pore-scale flow and reactive transport model is developed that explicitly tracks mineral surfaces as they evolve using a direct numerical simulation approach. Simulations of dissolution in single-mineral domains provide insights into the transport controls at the pore scale, while the simulation of a fracture surface composed of bands of faster-dissolving calcite and slower-dissolving dolomite provides insights into the mineralogical controls on evolution. Transport-limited conditions at the grain-pack scale may result in unstable evolution, a situation in which dissolution is focused in a fast-flowing, fast-dissolving path. Due to increasing velocities, the evolution in these regions is like that observed under conditions closer to strict surface control at the pore scale. That is, grains evolve to have oblong shapes with their long dimensions aligning with the local flow directions. Another example of an evolving reactive transport regime that affects local rates is seen in the evolution of the fracture surface. As calcite dissolves, the diffusive length between the fracture flow path and the receding calcite surfaces increases. Thus, the calcite dissolution reaction becomes increasingly limited by diffusion.
      PubDate: 2017-05-02T10:10:57.451786-05:
      DOI: 10.1002/2016WR020323
  • Big Ship Data: Using vessel measurements to improve estimates of
           temperature and wind speed on the Great Lakes
    • Authors: Kevin Fries; Branko Kerkez
      Pages: 3662 - 3679
      Abstract: The sheer size of many water systems challenges the ability of in situ sensor networks to resolve spatiotemporal variability of hydrologic processes. New sources of vastly distributed and mobile measurements are, however, emerging to potentially fill these observational gaps. This paper poses the question: How can nontraditional measurements, such as those made by volunteer ship captains, be used to improve hydrometeorological estimates across large surface water systems' We answer this question through the analysis of one of the largest such data sets: an unprecedented collection of one million unique measurements made by ships on the North American Great Lakes from 2006 to 2014. We introduce a flexible probabilistic framework, which can be used to integrate ship measurements, or other sets of irregular point measurements, into contiguous data sets. The performance of this framework is validated through the development of a new ship-based spatial data product of water temperature, air temperature, and wind speed across the Great Lakes. An analysis of the final data product suggests that the availability of measurements across the Great Lakes will continue to play a large role in the confidence with which these large surface water systems can be studied and modeled. We discuss how this general and flexible approach can be applied to similar data sets, and how it will be of use to those seeking to merge large collections of measurements with other sources of data, such as physical models or remotely sensed products.
      PubDate: 2017-05-02T10:10:44.49818-05:0
      DOI: 10.1002/2016WR020084
  • Implementation of a physiographic complexity-based multiresolution snow
           modeling scheme
    • Authors: Elisabeth Baldo; Steven A. Margulis
      Pages: 3680 - 3694
      Abstract: Using a uniform model resolution over a domain is not necessarily the optimal approach for simulating hydrologic processes when considering both model error and computational cost. Fine-resolution simulations at 100 m or less can provide fine-scale process representation, but can be costly to apply over large domains. On the other hand, coarser spatial resolutions are more computationally inexpensive, but at the expense of fine-scale model accuracy. Defining a multiresolution (MR) grid spanning from fine resolutions over complex mountainous areas to coarser resolutions over less complex regions can conceivably reduce computational costs, while preserving the accuracy of fine-resolution simulations on a uniform grid. A MR scheme was developed using a physiographic complexity metric (CM) that combines surface heterogeneity in forested fraction, elevation, slope, and aspect. A data reduction term was defined as a metric (relative to a uniform fine-resolution grid) related to the available computational resources for a simulation. The focus of the effort was on the snowmelt season where physiographic complexity is known to have a significant signature. MR simulations were run for different data reduction factors to generate melt rate estimates for three representative water years over a test headwater catchment in the Colorado River Basin. The MR approach with data reductions up to 47% led to negligible cumulative snowmelt differences compared to the fine-resolution baseline case, while tests with data reductions up to 60% showed differences lower than 2%. Large snow-dominated domains could therefore benefit from a MR approach to be more efficiently simulated while mitigating error.
      PubDate: 2017-05-02T10:10:49.59237-05:0
      DOI: 10.1002/2016WR020021
  • Tropical river suspended sediment and solute dynamics in storms during an
           extreme drought
    • Authors: Kathryn E. Clark; James B. Shanley, Martha A. Scholl, Nicolas Perdrial, Julia N. Perdrial, Alain F. Plante, William H. McDowell
      Pages: 3695 - 3712
      Abstract: Droughts, which can strongly affect both hydrologic and biogeochemical systems, are projected to become more prevalent in the tropics in the future. We assessed the effects of an extreme drought during 2015 on stream water composition in the Luquillo Mountains of Puerto Rico. We demonstrated that drought base flow in the months leading up to the study was sourced from trade-wind orographic rainfall, suggesting a resistance to the effects of an otherwise extreme drought. In two catchments (Mameyes and Icacos), we sampled a series of four rewetting events that partially alleviated the drought. We collected and analyzed dissolved constituents (major cations and anions, organic carbon, and nitrogen) and suspended sediment (inorganic and organic matter (particulate organic carbon and particulate nitrogen)). The rivers appeared to be resistant to extreme drought, recovering quickly upon rewetting, as (1) the concentration-discharge (C-Q) relationships deviated little from the long-term patterns; (2) “new water” dominated streamflow during the latter events; (3) suspended sediment sources had accumulated in the channel during the drought flushed out during the initial events; and (4) the severity of the drought, as measured by the US drought monitor, was reduced dramatically after the rewetting events. Through this interdisciplinary study, we were able to investigate the impact of extreme drought through rewetting events on the river biogeochemistry.
      PubDate: 2017-05-03T00:40:46.779128-05:
      DOI: 10.1002/2016WR019737
  • Early formation of preferential flow in a homogeneous snowpack observed by
    • Authors: Francesco Avanzi; Giacomo Petrucci, Margret Matzl, Martin Schneebeli, Carlo De Michele
      Pages: 3713 - 3729
      Abstract: We performed X-ray microtomographic observations of wet-snow metamorphism during controlled continuous melting and melt-freeze events in the laboratory. Three blocks of snow were sieved into boxes and subjected to cyclic, superficial heating or heating-cooling to reproduce vertical water infiltration patterns in snow similarly to natural conditions. Periodically, samples were taken at different heights and scanned. Results suggest that wet-snow metamorphism dynamics are highly heterogeneous even in an initially homogeneous snowpack. Consistent with previous work, we observed an increase with time in the thickness of the ice structure, which is a measure of grain size. However, this was coupled with large temporal scatter between consecutive measurements of the specific surface area and of the statistical moments of grain thickness distributions. Because of marked differences in the right tail, grain thickness distributions did not show shape invariance with time, contrary to previous analyses. In our experiments, wet-snow metamorphism showed two strikingly different patterns: homogeneous coarsening superimposed by faster heterogeneous coarsening in areas that were affected by preferential percolation of water. Liquid water movement in snow and fast structural evolution may be thus intrinsically coupled by early formation of preferential flow at local scale. These observations suggest that further experiments are highly needed to fully understand wet-snow metamorphism and infiltration patterns in a natural snowpack.
      PubDate: 2017-05-04T06:11:32.197476-05:
      DOI: 10.1002/2016WR019502
  • An efficient and stable hydrodynamic model with novel source term
           discretization schemes for overland flow and flood simulations
    • Authors: Xilin Xia; Qiuhua Liang, Xiaodong Ming, Jingming Hou
      Pages: 3730 - 3759
      Abstract: Numerical models solving the full 2-D shallow water equations (SWEs) have been increasingly used to simulate overland flows and better understand the transient flow dynamics of flash floods in a catchment. However, there still exist key challenges that have not yet been resolved for the development of fully dynamic overland flow models, related to (1) the difficulty of maintaining numerical stability and accuracy in the limit of disappearing water depth and (2) inaccurate estimation of velocities and discharges on slopes as a result of strong nonlinearity of friction terms. This paper aims to tackle these key research challenges and present a new numerical scheme for accurately and efficiently modeling large-scale transient overland flows over complex terrains. The proposed scheme features a novel surface reconstruction method (SRM) to correctly compute slope source terms and maintain numerical stability at small water depth, and a new implicit discretization method to handle the highly nonlinear friction terms. The resulting shallow water overland flow model is first validated against analytical and experimental test cases and then applied to simulate a hypothetic rainfall event in the 42 km2 Haltwhistle Burn, UK.
      PubDate: 2017-05-05T00:40:49.92941-05:0
      DOI: 10.1002/2016WR020055
  • Time-dependent velocity-field controls on anomalous chemical transport in
           porous media
    • Authors: Alon Nissan; Ishai Dror, Brian Berkowitz
      Pages: 3760 - 3769
      Abstract: Temporal variations in the subsurface velocity field are often (if not always) present in the real world to at least some degree. However, an accounting of their effects on chemical transport has been largely neglected. Here we demonstrate experimentally the effects of a time-varying velocity field on conservative chemical tracer transport in porous media, as compared to constant velocity conditions. We find that velocity-field fluctuations increase chemical tracer spreading and residence time, which intensify the anomalous nature of the transport. This behavior is modeled by a continuous time random walk particle tracking method formulated to account for time-dependent velocity fields. The model matches the experimental results with a parsimonious and consistent set of parameters. The model is then applied to study the effects of different magnitudes in velocity-field fluctuations, as well as different degrees of porous media heterogeneity, on 1-D and 2-D spatiotemporal propagation of an injected, point-source, chemical plume. Increased intensity of velocity-field fluctuations, and increased porous medium heterogeneity, each serve to increase the extent of chemical spreading and anomalous behavior.
      PubDate: 2017-05-05T00:45:45.329039-05:
      DOI: 10.1002/2016WR020143
  • Lattice Boltzmann simulation of immiscible two-phase flow with capillary
           valve effect in porous media
    • Authors: Zhiyuan Xu; Haihu Liu, Albert J. Valocchi
      Pages: 3770 - 3790
      Abstract: A new algorithm for imposing the contact angle on solid surfaces is proposed in the Lattice Boltzmann color-gradient model. The capability and accuracy of this algorithm are validated by simulation of contact angles for a droplet resting on a flat surface and on a cylindrical surface. The color-gradient model with the proposed contact angle algorithm is then used to study the capillary valve effect in porous media. As a preliminary study, the capillary valve effect is explained by simulating immiscible two-phase displacement within a single-pore geometry. It is shown that the capillary valve effect is accurately captured by the present simulations. Further simulations of drainage and imbibition are also conducted to understand the capillary valve effect in an experiment-matched pore-network micromodel. The simulated results are found to agree quantitatively with the experimental results reported in literature, except for a few differences which result from the exclusion of contact angle hysteresis in the proposed algorithm.
      PubDate: 2017-05-05T04:12:16.639404-05:
      DOI: 10.1002/2017WR020373
  • Inferring reservoir operating patterns across the Mekong Basin using only
           space observations
    • Authors: Matthew Bonnema; Faisal Hossain
      Pages: 3791 - 3810
      Abstract: This study explores the operating pattern of artificial reservoirs by examining their impact on streamflow through two parameters, residence time and flow alteration, using a purely satellite-based technique for the Mekong Basin. Overall residence times of individual reservoirs ranged from 0.09 to 4.04 years, while streamflow was altered between 11 and 130% of its natural variability. The current set of reservoirs appears to have increased the residence time of the entire Mekong basin by about 1 month. However, if subbasin variability is considered, the satellite-based method depicts a different picture. Residence time increases to 4 months when only regulated flows are considered. If low residence time reservoirs on major rivers are excluded and reservoirs on higher stream-order rivers considered, residence time increases to 1.3 years. Predictable strong seasonal patterns emerged in residence time, where reservoirs experience higher residence time in the dry season and lower residence time in the wet season and residence time varies inversely with precipitation. High variability in reservoir effects on streamflow between reservoirs could not be explained by any reservoir properties (e.g., size, use, location, etc.), highlighting the variability in the human decisions operating these reservoirs. The take-home message of this study is that satellite observations, in combination with physical models forced with satellite data, can elucidate the spatiotemporal variability of reservoir behavior in ungauged basins of the developing world. We demonstrate in this study that the requirement for ground data to monitor current or historical behavior of dams is not necessary.
      PubDate: 2017-05-09T23:55:31.86635-05:0
      DOI: 10.1002/2016WR019978
  • Characterizing landscape-scale erosion using 10Be in detrital fluvial
           sediment: Slope-based sampling strategy detects the effect of widespread
    • Authors: Lucas J. Reusser; Paul R. Bierman, Donna M. Rizzo, Eric W. Portenga, Dylan H. Rood
      Pages: 4476 - 4486
      Abstract: Concentrations of in situ 10Be measured in detrital fluvial sediment are frequently used to estimate long-term erosion rates of drainage basins. In many regions, basin-averaged erosion rates are positively correlated with basin average slope. The slope dependence of erosion allows model-based erosion rate estimation for unsampled basins and basins where human disturbance may have biased cosmogenic nuclide concentrations in sediment. Using samples collected from southeastern North America, we demonstrate an approach that explicitly considers the relationship between average basin slope and erosion rate. Because dams and reservoirs are ubiquitous on larger channels in the field area, we selected 36 undammed headwater subbasins (average area 10.6 km2) from which we collected river sand samples and measured 10Be concentrations. We used these data to train a predictive model that relates average basin slope and 10Be-inferred erosion rate. Applying our model to 28 basins in the same region previously studied with 10Be, we find that the model successfully predicts erosion rates for basins of different sizes if they are undammed or if samples were collected>25 km downstream of dams. For samples collected closer to dams, measured erosion rates exceed modeled erosion rates for two-thirds of the samples. In three of four cases where paired samples were collected upstream of reservoirs and downstream of the impounding dam, 10Be concentrations were lower downstream. This finding has implications for detrital cosmogenic studies, whether or not samples were collected directly downstream of dams, because dams obstruct most major rivers around the world, effectively trapping sediment that originated upstream.
      PubDate: 2017-05-04T06:16:13.424782-05:
      DOI: 10.1002/2016WR019774
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
Home (Search)
Subjects A-Z
Publishers A-Z
Your IP address:
About JournalTOCs
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2016