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  Subjects -> WATER RESOURCES (Total: 148 journals)
Showing 1 - 47 of 47 Journals sorted alphabetically
Acque Sotterranee - Italian Journal of Groundwater     Open Access  
Acta Limnologica Brasiliensia     Open Access   (Followers: 2)
Advances in Oceanography and Limnology     Open Access   (Followers: 10)
Advances in Water Resource and Protection     Open Access   (Followers: 7)
Advances in Water Resources     Hybrid Journal   (Followers: 30)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 12)
Agricultural Water Management     Hybrid Journal   (Followers: 28)
American Journal of Water Resources     Open Access   (Followers: 4)
American Water Works Association     Hybrid Journal   (Followers: 18)
Anales de Hidrología Médica     Open Access  
Annals of Warsaw University of Life Sciences - SGGW. Land Reclamation     Open Access  
Annual Review of Marine Science     Full-text available via subscription   (Followers: 10)
Applied Water Science     Open Access   (Followers: 5)
Aquacultural Engineering     Hybrid Journal   (Followers: 6)
Aquaculture     Hybrid Journal   (Followers: 31)
Aquaculture Environment Interactions     Open Access   (Followers: 2)
Aquaculture Research     Hybrid Journal   (Followers: 30)
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  
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: 20)
Civil and Environmental Research     Open Access   (Followers: 16)
CLEAN - Soil, Air, Water     Hybrid Journal   (Followers: 18)
Computational Water, Energy, and Environmental Engineering     Open Access   (Followers: 4)
Cost Effectiveness and Resource Allocation     Open Access   (Followers: 5)
Desalination     Hybrid Journal   (Followers: 6)
Desalination and Water Treatment     Hybrid Journal   (Followers: 9)
Developments in Water Science     Full-text available via subscription   (Followers: 8)
Ecological Chemistry and Engineering S     Open Access   (Followers: 2)
Environmental Science : Water Research & Technology     Full-text available via subscription   (Followers: 2)
Environmental Toxicology     Hybrid Journal   (Followers: 7)
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: 5)
Ground Water Monitoring & Remediation     Hybrid Journal   (Followers: 17)
Groundwater for Sustainable Development     Full-text available via subscription  
Grundwasser     Hybrid Journal  
Hydro Nepal : Journal of Water, Energy and Environment     Open Access   (Followers: 3)
Hydrology Research     Partially Free   (Followers: 11)
Hydrology: Current Research     Open Access   (Followers: 10)
IDA Journal of Desalination and Water Reuse     Hybrid Journal   (Followers: 1)
Ingeniería del agua     Open Access  
International Journal of Climatology     Hybrid Journal   (Followers: 24)
International Journal of Hydrology Science and Technology     Hybrid Journal   (Followers: 5)
International Journal of Nuclear Desalination     Hybrid Journal  
International Journal of River Basin Management     Hybrid Journal   (Followers: 2)
International Journal of Salt Lake Research     Hybrid Journal   (Followers: 2)
International Journal of Waste Resources     Open Access   (Followers: 3)
International Journal of Water     Hybrid Journal   (Followers: 12)
International Journal of Water Resources and Environmental Engineering     Open Access   (Followers: 6)
International Journal of Water Resources Development     Hybrid Journal   (Followers: 22)
International Soil and Water Conservation Research     Open Access  
Irrigation and Drainage     Hybrid Journal   (Followers: 10)
Irrigation Science     Hybrid Journal   (Followers: 3)
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: 6)
Journal of Geophysical Research : Oceans     Partially Free   (Followers: 42)
Journal of Hydro-environment Research     Full-text available via subscription   (Followers: 9)
Journal of Hydroinformatics     Full-text available via subscription   (Followers: 1)
Journal of Hydrology (New Zealand)     Full-text available via subscription   (Followers: 1)
Journal of Hydrology and Hydromechanics     Open Access   (Followers: 1)
Journal of Hydrometeorology     Full-text available via subscription   (Followers: 5)
Journal of Limnology     Open Access   (Followers: 6)
Journal of the American Water Resources Association     Hybrid Journal   (Followers: 28)
Journal of Water and Climate Change     Partially Free   (Followers: 35)
Journal of Water and Health     Partially Free   (Followers: 3)
Journal of Water Chemistry and Technology     Hybrid Journal   (Followers: 8)
Journal of Water Process Engineering     Full-text available via subscription   (Followers: 4)
Journal of Water Resource and Hydraulic Engineering     Open Access   (Followers: 7)
Journal of Water Resource and Protection     Open Access   (Followers: 9)
Journal of Water Resource Engineering and Management     Full-text available via subscription   (Followers: 2)
Journal of Water Resources Planning and Management     Full-text available via subscription   (Followers: 42)
Journal of Water Reuse and Desalination     Partially Free   (Followers: 7)
Journal of Water Science & Environment Technologies     Open Access  
Journal of Water Security     Open Access   (Followers: 1)
Journal of Water Supply : Research and Technology - AQUA     Partially Free   (Followers: 7)
Journal of Water, Sanitation and Hygiene for Development     Open Access   (Followers: 4)
La Houille Blanche     Full-text available via subscription   (Followers: 1)
Lake and Reservoir Management     Hybrid Journal   (Followers: 6)
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: 22)
Marine Ecosystem Stressor Response     Open Access  
Methods in Oceanography : An International Journal     Hybrid Journal   (Followers: 5)
New Zealand Journal of Marine and Freshwater Research     Hybrid Journal   (Followers: 6)
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: 8)
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: 15)
River Systems     Full-text available via subscription   (Followers: 3)
SA Irrigation = SA Besproeiing     Full-text available via subscription  
SABI Magazine - Tydskrif     Full-text available via subscription  
San Francisco Estuary and Watershed Science     Open Access   (Followers: 1)
Sciences Eaux & Territoires : la Revue du Cemagref     Open Access  
Scientia Marina     Open Access   (Followers: 2)
Society & Natural Resources: An International Journal     Hybrid Journal   (Followers: 16)
Sri Lanka Journal of Aquatic Sciences     Open Access   (Followers: 1)
Sustainability of Water Quality and Ecology     Hybrid Journal   (Followers: 2)
Sustainable Technologies, Systems & Policies     Open Access   (Followers: 9)
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: 3)
Water and Environment Journal     Hybrid Journal   (Followers: 18)
Water Environment and Technology     Full-text available via subscription   (Followers: 15)
Water Environment Research     Full-text available via subscription   (Followers: 37)
Water International     Hybrid Journal   (Followers: 12)
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: 12)
Water Quality Research Journal of Canada     Full-text available via subscription   (Followers: 5)
Water Research     Hybrid Journal   (Followers: 49)
Water Resources     Hybrid Journal   (Followers: 17)
Water Resources and Economics     Hybrid Journal   (Followers: 3)
Water Resources and Industry     Open Access   (Followers: 3)
Water Resources and Rural Development     Hybrid Journal   (Followers: 2)
Water Resources Management     Hybrid Journal   (Followers: 29)
Water Resources Research     Full-text available via subscription   (Followers: 70)
Water SA     Open Access  
Water Science & Technology     Partially Free   (Followers: 24)
Water Science : The National Water Research Center Journal     Open Access   (Followers: 5)
Water Science and Engineering     Open Access   (Followers: 7)
Water Science and Technology : Water Supply     Partially Free   (Followers: 21)
Water Wheel     Open Access   (Followers: 2)
Water, Air, & Soil Pollution     Hybrid Journal   (Followers: 22)
Water21     Full-text available via subscription  
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: 22)
Wiley Interdisciplinary Reviews : Water     Hybrid Journal  
WMU Journal of Maritime Affairs     Hybrid Journal   (Followers: 2)

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Journal Cover Water Resources Research
  [SJR: 2.661]   [H-I: 144]   [70 followers]  Follow
   Full-text available via subscription Subscription journal
   ISSN (Print) 0043-1397 - ISSN (Online) 1944-7973
   Published by AGU Homepage  [17 journals]
  • Nonstationary decision model for flood risk decision scaling
    • Authors: Caitlin M. Spence; Casey M. Brown
      Abstract: Hydroclimatic stationarity is increasingly questioned as a default assumption in flood risk management (FRM), but successor methods are not yet established. Some potential successors depend on estimates of future flood quantiles, but methods for estimating future design storms are subject to high levels of uncertainty. Here we apply a Nonstationary Decision Model (NDM) to flood risk planning within the decision scaling framework. The NDM combines a nonstationary probability distribution of annual peak flow with optimal selection of flood management alternatives using robustness measures. The NDM incorporates structural and nonstructural FRM interventions and valuation of flows supporting ecosystem services to calculate expected cost of a given FRM strategy. A search for the minimum-cost strategy under incrementally varied representative scenarios extending across the plausible range of flood trend and value of the natural flow regime discovers candidate FRM strategies that are evaluated and compared through a decision scaling analysis (DSA). The DSA selects a management strategy that is optimal or close to optimal across the broadest range of scenarios or across the set of scenarios deemed most likely to occur according to estimates of future flood hazard. We illustrate the decision framework using a stylized example flood management decision based on the Iowa City flood management system, which has experienced recent unprecedented high flow episodes. The decision scaling analysis indicates a preference for combining infrastructural and non-structural adaptation measures to manage flood risk and makes clear that options-based approaches cannot be assumed to be “no” or “low regret.” This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-17T17:51:00.820067-05:
      DOI: 10.1002/2016WR018981
  • Transferability of hydrological models and ensemble averaging methods
           between contrasting climatic periods
    • Authors: Ciaran Broderick; Tom Matthews, Robert L. Wilby, Satish Bastola, Conor Murphy
      Abstract: Understanding hydrological model predictive capabilities under contrasting climate conditions enables more robust decision making. Using Differential Split Sample Testing (DSST) we analyse the performance of six hydrological models for 37 Irish catchments under climate conditions unlike those used for model training. Additionally, we consider four ensemble averaging techniques when examining inter-period transferability. DSST is conducted using two/three-year non-continuous blocks of (i) the wettest/driest years on record based on precipitation totals, and (ii) years with a more/less pronounced seasonal precipitation regime. Model transferability between contrasting regimes was found to vary depending on the testing scenario, catchment and evaluation criteria considered. As expected, the ensemble average outperformed most individual ensemble members. However, averaging techniques differed considerably in the number of times they surpassed the best individual model-member. Bayesian Model Averaging (BMA) and the Granger-Ramanathan (GRA) method were found to outperform the simple arithmetic mean (SAM) and Akaike Information Criteria Averaging (AICA). Here, GRA performed better than the best individual model in 51% to 86% of cases (according to the Nash-Sutcliffe criterion). When assessing model predictive skill under climate change conditions we recommend (i) setting up DSST to select the best available analogues of expected annual mean and seasonal climate conditions; (ii) applying multiple performance criteria; (iii) testing transferability using a diverse set of catchments and; (iv) using a multi-model ensemble in conjunction with an appropriate averaging technique. Given the computational efficiency and performance of GRA relative to BMA, the former is recommended as the preferred ensemble averaging technique for climate assessment. This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-17T17:50:55.800496-05:
      DOI: 10.1002/2016WR018850
  • Numerical homogenization of the Richards equation for unsaturated water
           flow through heterogeneous soils
    • Authors: Na Li; Xingye Yue, Li Ren
      Abstract: Homogenized equations and the corresponding effective constitutive relations are generally necessary for numerically modeling large-scale unsaturated flow processes in soils. Recently, based on the Kirchhoff transformation and the two-scale convergence theory, a homogenization method for the Richards equation with the Mualem-van Genuchten model has been proposed, with a constant model parameter α relating to the inverse of the air-entry pressure and the soil pore size distribution. The homogenized model is computationally efficient and convenient to use because of its explicit expression. In this study, we generalize this method, allowing α to be a spatially distributed random field and proposing a homogenized Richards equation in the mixed form (θ/h) under the condition that the effective hydraulic conductivity tensor is diagonal. This generalization eliminates the limitation of a constant α in practical applications; the proposed homogenized model is meaningful in most situations because the flow problems are influenced mainly by the diagonal terms of conductivity and the off-diagonal terms are often neglected. Two-dimensional numerical tests are conducted in soil profiles with different degrees of spatial heterogeneity structure to illustrate that the homogenized model can capture the fine-scale flow behaviors on coarse grids effectively. Homogenization for the Richards equation with other two commonly used constitutive relations - the Brooks-Corey model and the Gardner-Russo model - is also illustrated in this study. This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-13T03:30:55.145593-05:
      DOI: 10.1002/2015WR018508
  • Validating reconstruction of snow water equivalent in California's Sierra
           Nevada using measurements from the NASA Airborne Snow Observatory
    • Authors: Edward H. Bair; Karl Rittger, Robert E. Davis, Thomas H. Painter, Jeff Dozier
      Abstract: Accurately estimating basin-wide snow water equivalent (SWE) is the most important unsolved problem in mountain hydrology. Models that rely on remotely sensed inputs are especially needed in ranges with few surface measurements. The NASA Airborne Snow Observatory (ASO) provides estimates of SWE at 50-meter spatial resolution in several basins across the Western US during the melt season. Primarily, water managers use this information to forecast snowmelt runoff into reservoirs; another impactful use of ASO measurements lies in validating and improving satellite-based snow estimates or models that can scale to whole mountain ranges, even those without ground-based measurements. We compare ASO measurements from 2013 to 2015 to four methods that estimate spatially distributed SWE: two versions of a SWE reconstruction method, spatial interpolation from snow pillows and courses, and NOAA's Snow Data Assimilation System (SNODAS). SWE reconstruction downscales energy forcings to compute potential melt, then multiplies those values by satellite-derived estimates of fractional snow-covered area to calculate snowmelt. The snowpack is then built in reverse from the date the snow is observed to disappear. The two SWE reconstruction models tested include one that employs an energy balance calculation of snowmelt, and one that combines net radiation and degree-day approaches to estimate melt. Our full energy balance model, without ground observations, performed slightly better than spatial interpolation from snow pillows, having no systematic bias and 26% mean absolute error when compared to SWE from ASO. Both reconstruction models and interpolation were more accurate than SNODAS. This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-13T03:30:47.034519-05:
      DOI: 10.1002/2016WR018704
  • Connectivity, permeability and channeling in randomly-distributed and
           kinematically-defined discrete fracture network models
    • Authors: J. Maillot; P. Davy, R. Le Goc, C. Darcel, J.R. de Dreuzy
      Abstract: A major use of DFN models for industrial applications is to evaluate permeability and flow structure in hardrock aquifers from geological observations of fracture networks. The relationship between the statistical fracture density distributions and permeability has been extensively studied, but there has been little interest in the spatial structure of DFN models, which is generally assumed to be spatially random (i.e. Poisson). In this paper, we compare the predictions of Poisson DFNs to new DFN models where fractures result from a growth process defined by simplified kinematic rules for nucleation, growth and fracture arrest (Davy et al, 2010, 2013). This so-called ‘kinematic fracture model' is characterized by a large proportion of T-intersections, and a smaller number of intersections per fracture. Several kinematic models were tested and compared with Poisson DFN models with the same density, length and orientation distributions. Connectivity, permeability and flow distribution were calculated for 3D networks with a self-similar power-law fracture length distribution. For the same statistical properties in orientation and density, the permeability is systematically and significantly smaller by a factor of 1.5 to 10 for kinematic than for Poisson models. In both cases, the permeability is well described by a linear relationship with the areal density p32, but the threshold of kinematic models is 50% larger than of Poisson models. Flow channeling is also enhanced in kinematic DFN models. This analysis demonstrates the importance of choosing an appropriate DFN organization for predicting flow properties from fracture network parameters. This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-13T03:26:05.914626-05:
      DOI: 10.1002/2016WR018973
  • Variation of organic matter quantity and quality in streams at critical
           zone observatory watersheds
    • Authors: Matthew P. Miller; Elizabeth W. Boyer, Diane M. McKnight, Michael G. Brown, Rachel S. Gabor, Carolyn T. Hunsaker, Lidiia Iavorivska, Shreeram Inamdar, Dale W. Johnson, Louis A. Kaplan, Henry Lin, William H. McDowell, Julia N. Perdrial
      Abstract: The quantity and chemical composition of dissolved organic matter (DOM) in surface waters influence ecosystem processes and anthropogenic use of freshwater. However, despite the importance of understanding spatial and temporal patterns in DOM, measures of DOM quality are not routinely included as part of large scale ecosystem monitoring programs and variations in analytical procedures can introduce artifacts. In this study, we used consistent sampling and analytical methods to meet the objective of defining variability in DOM quantity and quality and other measures of water quality in streamflow issuing from small forested watersheds located within five Critical Zone Observatory sites representing contrasting environmental conditions. Results show distinct separations among sites as a function of water quality constituents. Relationships among rates of atmospheric deposition, water quality conditions, and stream DOM quantity and quality are consistent with the notion that areas with relatively high rates of atmospheric nitrogen and sulfur deposition and high concentrations of divalent cations result in selective transport of DOM derived from microbial sources, including in-stream microbial phototrophs. We suggest that the critical zone as a whole strongly influences the origin, composition, and fate of DOM in streams. This study highlights the value of consistent DOM characterization methods included as part of long-term monitoring programs for improving our understanding of interactions among ecosystem processes as controls on DOM biogeochemistry. This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-13T03:25:59.092479-05:
      DOI: 10.1002/2016WR018970
  • Diel discharge cycles explained through viscosity fluctuations in riparian
    • Authors: Michael Schwab; Julian Klaus, Laurent Pfister, Markus Weiler
      Abstract: Diel (also called diurnal) discharge patterns with minima in the afternoon are generally explained by the daily cycle of evapotranspiration, while maxima in the afternoon are often linked to freeze-thaw cycles. In a schistose and forested headwater catchment in Luxembourg, we observed daily discharge maxima in the afternoon, although temperatures remained persistently above zero and vegetation was still in a dormant state. We show that diel water temperature fluctuations - and therefore viscosity fluctuations - in the upper layer of the riparian zone can be an explanation for the observed daily discharge maxima in the afternoon during the dormant season. In the transition period between the dormant and the growing season, the counteracting viscosity and evapotranspiration processes cancel each other out. Subsequently, during the growing season, evapotranspiration is the dominant process guiding the diel discharge pattern; nevertheless, the viscosity effect might still be present, but invisible. We believe this finding also to be of relevance when analyzing daily fluctuations of biogeochemicals in stream water. This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-11T10:30:44.15629-05:0
      DOI: 10.1002/2016WR018626
  • Global estimation of effective plant rooting depth: Implications for
           hydrological modelling
    • Authors: Yuting Yang; Randall J. Donohue, Tim R. McVicar
      Abstract: Plant rooting depth (Zr) is a key parameter in hydrological and biogeochemical models, yet the global spatial distribution of Zr is largely unknown due to the difficulties in its direct measurement. Additionally, Zr observations are usually only representative of a single plant or several plants, which can differ greatly from the effective Zr over a modelling unit (e.g., catchment or grid-box). Here, we provide a global parameterization of an analytical Zr model that balances the marginal carbon cost and benefit of deeper roots, and produce a climatological (i.e., 1982-2010 average) global Zr map. To test the Zr estimates, we apply the estimated Zr in a highly transparent hydrological model (i.e., the Budyko-Choudhury-Porporato (BCP) model) to estimate mean annual actual evapotranspiration (E) across the globe. We then compare the estimated E with both water balance-based E observations at 32 major catchments and satellite grid-box retrievals across the globe. Our results show that the BCP model, when implemented with Zr estimated herein, optimally reproduced the spatial pattern of E at both scales (i.e., R2=0.94, RMSD=74 mm yr−1 for catchments, and R2=0.90, RMSD=125 mm yr−1 for grid-boxes) and provides improved model outputs when compared to BCP model results from two already existing global Zr datasets. These results suggest that our Zr estimates can be effectively used in state-of-the-art hydrological models, and potentially biogeochemical models, where the determination of Zr currently largely relies on biome type-based look-up tables. This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-11T10:30:42.238109-05:
      DOI: 10.1002/2016WR019392
  • A hydro-economic modelling framework for optimal integrated management of
           forest and water
    • Authors: Alberto García-Prats; Antonio D. del Campo, Manuel Pulido-Velazquez
      Abstract: Forests play a determinant role in the hydrologic cycle, with water being the most important ecosystem service they provide in semiarid regions. However, this contribution is usually neither quantified nor explicitly valued. The aim of this study is to develop a novel hydro-economic modelling framework for assessing and designing the optimal integrated forest and water management for forested catchments. The optimization model explicitly integrates changes in water yield in the stands (increase in groundwater recharge) induced by forest management, and the value of the additional water provided to the system. The model determines the optimal schedule of silvicultural interventions in the stands of the catchment in order to maximize the total net benefit in the system. Canopy cover and biomass evolution over time were simulated using growth and yield allometric equations specific for the species in Mediterranean conditions. Silvicultural operation costs according to stand density and canopy cover were modelled using local cost databases. Groundwater recharge was simulated using HYDRUS, calibrated and validated with data from the experimental plots. In order to illustrate the presented modelling framework a case study was carried out in a planted pine forest (Pinus halepensis Mill.) located in south-western Valencia province (Spain).The optimized scenario increased groundwater recharge. This novel modelling framework can be used in the design of a “payment for environmental services” scheme in which water beneficiaries could contribute to fund and promote efficient forest management operations. This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-11T10:30:39.341762-05:
      DOI: 10.1002/2015WR018273
  • Drainage mechanisms in porous media: From piston-like invasion to
           formation of corner flow networks
    • Authors: Frouke Hoogland; Peter Lehmann, Rajmund Mokso, Dani Or
      Abstract: Water drainage from porous media is a highly dynamic process often marked by rapid piston-like air invasion events at the front and other rapid interfacial reconfigurations. Liquid phase entrapped behind the moving front drains at significantly slower rates often via gravity driven flow through corners and crevices. This distribution of slowly draining residual water phase determines the plant available water and biological functioning of soils. The study aims to determine the conditions for the flow regime transition from piston-like invasion at a drainage front to slower corner and film-dominated flow at the pore and sample scale. This transition was observed experimentally for sand and glass beads with fast X-ray tomography, revealing water fragmentation into clusters of full pores interconnected by water in films and corners. The observed liquid morphology at the transition from piston to corner flow was reproduced by a quasi-static pore network model and predicted by percolation theory. The amount of capillary-retained water at flow transition controlling the subsequent drainage dynamics could be reproduced by an idealized star shaped pore whose geometry is deduced from macroscopic properties of the porous medium. Predictions of water content thresholds at flow transitions were in agreement with other critical saturation values associated with cessation of solute diffusion and of internal drainage (at field capacity) highlighting the criticality of water phase continuity disruption for formation of relatively stable unsaturated conditions controlled by slow corner flow that support life in soil. This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-11T08:45:54.455873-05:
      DOI: 10.1002/2016WR019299
  • Drainage dynamics controlled by corner flow: Application of the foam
           drainage equation
    • Authors: Frouke Hoogland; Peter Lehmann, Dani Or
      Abstract: In fast drainage processes water is retained behind the front, defining the plant available water and hydraulic properties of the unsaturated region. In this study we show that the foam drainage equation (FDE) can be applied to predict macroscopic drainage dynamics behind the front because a network of liquid channels controls the liquid flow in both foams and crevices of the pore space. To predict drainage rates at the Darcy scale the FDE is solved numerically after adapting channel geometries and boundary conditions to experimental conditions. The FDE results were in good agreement with measured flow rates behind a drainage front in coarse and fine sand. A notable exception was rapid drainage from fine sand where saturated pore clusters persisted after front passage and drained faster compared to FDE predictions. The dominance of corner capillary flows implied by the good agreement with the FDE formulation could improve the scientific underpinning of the unsaturated hydraulic conductivity function and offers a more realistic view of the geometry of pathways for colloid and pathogen transport in unsaturated media. This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-11T08:45:52.999391-05:
      DOI: 10.1002/2016WR019477
  • On the value of surface saturated area dynamics mapped with thermal
           infrared imagery for modeling the hillslope-riparian-stream continuum
    • Authors: B. Glaser; J. Klaus, S. Frei, J. Frentress, L. Pfister, L. Hopp
      Abstract: The highly dynamic processes within a hillslope-riparian-stream (HRS) continuum are known to affect streamflow generation, but are yet not fully understood. Within this study, we simulated a headwater HRS continuum in western Luxembourg with an integrated hydrologic surface subsurface model (HydroGeoSphere). The model was set up with thorough consideration of catchment-specific attributes and we performed a multi criteria model evaluation (4 years) with special focus on the temporally varying spatial patterns of surface saturation. We used a portable thermal infrared (TIR) camera to map surface saturation with a high spatial resolution and collected 20 panoramic snapshots of the riparian zone (approx. 10 m x 20 m) under different hydrologic conditions. Qualitative and quantitative comparison of the processed TIR panoramas and the corresponding model output panoramas revealed a good agreement between spatiotemporal dynamic model and field surface saturation patterns. A double logarithmic linear relationship between surface saturation extent and discharge was similar for modeled and observed data. This provided confidence in the capability of an integrated hydrologic surface subsurface model to represent temporal and spatial water flux dynamics at small (HRS continuum) scales. However, model scenarios with different parameterizations of the riparian zone showed that discharge and surface saturation were controlled by different parameters and hardly influenced each other. Surface saturation only affected very fast runoff responses with a small volumetric contribution to stream discharge, indicating that the dynamic surface saturation in the riparian zone does not necessarily imply a major control on runoff generation. This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-07T10:35:27.975624-05:
      DOI: 10.1002/2015WR018414
  • Reliable long-range ensemble streamflow forecasts by combining dynamical
           climate forecasts: A conceptual runoff model and a staged error model
    • Authors: James C. Bennett; QJ Wang, Ming Li, David Robertson, Andrew Schepen
      Abstract: We present a new streamflow forecasting system called forecast guided stochastic scenarios (FoGSS). FoGSS makes use of ensemble seasonal precipitation forecasts from a coupled ocean-atmosphere general circulation model (CGCM). The CGCM forecasts are post-processed with the method of calibration, bridging and merging (CBaM) to produce ensemble precipitation forecasts over river catchments. CBaM corrects biases and removes noise from the CGCM forecasts, and produces highly reliable ensemble precipitation forecasts. The post-processed CGCM forecasts are used to force the Wapaba monthly rainfall-runoff model. Uncertainty in the hydrological modelling is accounted for with a 3-stage error model. Stage 1 applies the log-sinh transformation to normalize residuals and homogenize their variance; Stage 2 applies a conditional bias-correction to correct biases and help remove negative forecast skill; Stage 3 applies an autoregressive model to improve forecast accuracy at short lead-times and propagate uncertainty through the forecast. FoGSS generates ensemble forecasts in the form of time series for the coming 12-months.In a case study of two catchments, FoGSS produces reliable forecasts at all lead-times. Forecast skill with respect to climatology is evident to lead-times of about 3 months. At longer lead-times, forecast skill approximates that of climatology forecasts; that is, forecasts become like stochastic scenarios. Because forecast skill is virtually never negative at long lead-times, forecasts of accumulated volumes can be skillful. Forecasts of accumulated 12-month streamflow volumes are significantly skillful in several instances, and ensembles of accumulated volumes are reliable. We conclude that FoGSS forecasts could be highly useful to water managers. This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-07T10:30:41.396303-05:
      DOI: 10.1002/2016WR019193
  • The role of water treatment abstraction in the flux and greenhouse gas
           emissions from organic carbon and nitrogen within UK rivers
    • Authors: Finlay N.C; Johnson K, F. Worrall
      Abstract: The fate of organic matter through watersheds has been shown to be an important component of the global carbon cycle and processes in rivers can rapidly transfer carbon from the terrestrial biosphere to the atmosphere. However, the role of water abstraction in diverting organic matter from freshwater has not been considered. This study used two methods to estimate the amount of organic carbon removed by water treatment processes, firstly, by estimating the amount of carbon that has to be removed given the abstracted volumes and the freshwater composition; and, secondly, estimated from reports of the production and composition of water treatment residuals from water companies. For the UK, the median total organic carbon removed by water abstraction was 46 ktonnes C/yr, this equates to a median per capita value of 0.76 kg C/ca/yr. The median total organic nitrogen removed was 4.0 ktonnes N/yr, equivalent to 0.07 kg N/ca/yr. The removal of TOC by water abstraction represents 1.5% of the total removal rate across UK watersheds. The release of greenhouse gases from UK rivers is now estimated to be between 12754 – 32332 ktonnes CO2eq/yr equivalent to between 55 and 127 tonnes CO2eq/km2/yr with fluvial organic matter between 8800 and 15116 ktonnes CO2eq/yr in the proportion 6:86:8 N2O:CO2:CH4. The emissions factor for 1 tonne of organic carbon entering the UK fluvial network has a median value of 2.95 tonnes CO2eq/yr with a 5th to 95th percentile range of 2.55 to 3.59 tonnes CO2eq/yr. Globally, a per capita values for countries with municipal treated water supply would be 0.8 to 0.86 kg C/ca/yr. This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-04T10:25:48.623944-05:
      DOI: 10.1002/2016WR019362
  • Irrigation water policy analysis using a business simulation game
    • Authors: M. Buchholz; G. Holst, O. Musshoff
      Abstract: Despite numerous studies on farmers' responses to changing irrigation water policies, uncertainties remain about the potential of water pricing schemes and water quotas to reduce irrigation. Thus far, policy impact analysis is predominantly based upon rational choice models that assume behavioral assumptions, such as a perfectly rational profit-maximizing decision maker. Also, econometric techniques are applied which could lack internal validity due to uncontrolled field data. Furthermore, such techniques are not capable of identifying ill-designed policies prior to their implementation. With this in mind, we apply a business simulation game for ex ante policy impact analysis of irrigation water policies at the farm level. Our approach has the potential to reveal the policy-induced behavioral change of the participants in a controlled environment. To do so, we investigate how real farmers from Germany, in an economic experiment, respond to a water pricing scheme and a water quota intending to reduce irrigation. In the business simulation game, the participants manage a ‘virtual' cash-crop farm for which they make crop allocation and irrigation decisions during several production periods, while facing uncertain product prices and weather conditions. The results reveal that a water quota is able to reduce mean irrigation applications, while a water pricing scheme does not have an impact, even though both policies exhibit equal income effects for the farmers. However, both policies appear to increase the variation of irrigation applications. Compared to a perfectly rational profit-maximizing decision maker, the participants apply less irrigation on average, both when irrigation is not restricted and when a water pricing scheme applies. Moreover, the participants' risk attitude affects the irrigation decisions. This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-04T03:31:22.384391-05:
      DOI: 10.1002/2016WR018857
  • Spatial downscaling of precipitation using adaptable random forests
    • Authors: Xiaogang He; Nathaniel W. Chaney, Marc Schleiss, Justin Sheffield
      Abstract: This paper introduces Prec-DWARF (Precipitation Downscaling With Adaptable Random Forests), a novel machine-learning based method for statistical downscaling of precipitation. Prec-DWARF sets up a nonlinear relationship between precipitation at fine resolution and covariates at coarse/fine resolution, based on the advanced binary tree method known as Random Forests (RF). In addition to a single RF, we also consider a more advanced implementation based on two independent RFs which yield better results for extreme precipitation. Hourly gauge-radar precipitation data at 0.125° from NLDAS-2 are used to conduct synthetic experiments with different spatial resolutions (0.25°, 0.5° and 1°). Quantitative evaluation of these experiments demonstrates that Prec-DWARF consistently outperforms the baseline (i.e., bi-linear interpolation in this case) and can reasonably reproduce the spatial and temporal patterns, occurrence and distribution of observed precipitation fields. However, Prec-DWARF with a single RF significantly underestimates precipitation extremes and often cannot correctly recover the fine-scale spatial structure, especially for the 1° experiments. Prec-DWARF with a double RF exhibits improvement in the simulation of extreme precipitation as well as its spatial and temporal structures, but variogram analyses show that the spatial and temporal variability of the downscaled fields are still strongly underestimated. Covariate feature importance analysis shows that the most important predictors for the downscaling are the coarse scale precipitation values over adjacent grid cells as well as the distance to the closest dry grid cell (i.e., the dry drift). The encouraging results demonstrate the potential of Prec-DWARF and machine-learning based techniques in general for the statistical downscaling of precipitation. This article is protected by copyright. All rights reserved.
      PubDate: 2016-10-03T18:20:43.602251-05:
      DOI: 10.1002/2016WR019034
  • Colloids and Organic Matter Complexation Control Trace Metal
           Concentration‐Discharge Relationships in Marshall Gulch Stream Waters
    • Authors: Kyle D. Trostle; J. Ray Runyon, Michael A. Pohlmann, Shelby E. Redfield, Jon Pelletier, Jennifer McIntosh, Jon Chorover
      Abstract: This study combined concentration‐discharge analyses (filtration at 0.45 μm), cascade filtrations (at 1.2 μm, 0.4 μm, 0.025 μm) and asymmetrical flow field flow fractionation (AF4) to probe the influence of colloidal carriers (dissolved organic matter and inorganic nanoparticles) on observed concentration‐discharge relationships for trace metals in a 155 hectare forested catchment of the Santa Catalina Mountains Critical Zone Observatory (SCM CZO), Arizona, USA. Many major elements (Na, Mg, Si, K, Ca) show no colloidal influence, and concentration‐discharge relationships for these species are explained by previous work. However, the majority of trace metals (Al, Ti, V, Mn, Fe, Cu, Y, REE, U) show at least some influence of colloids on chemistry when filtered at the standard 0.45 μm cutoff. Concentration‐discharge slopes of trace metals with modest colloidal influence are shallow (∼0.3) similar to that measured for dissolved organic carbon (DOC, 0.24), whereas elements with greater colloidal influence have steeper concentration‐discharge slopes approaching that of Al (0.76), the element with the largest colloidal influence in this study (on average 68%). These findings are further supported by AF4 measurements that show distinct and resolvable pools of low hydrodynamic diameter DOC‐sized material coexistent with larger diameter inorganic colloids, and the ratio of these carriers changes systematically with discharge because the DOC pool has a concentration‐discharge relationship with shallower slope than the inorganic colloidal pool. Together these datasets illustrate that positive concentration‐discharge slopes of trace metals in stream waters may be explained as the relative partitioning of trace metals between DOC and inorganic colloids, with contributions of the latter likely increasing as a result of increased prevalence of macropore flow. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-29T10:03:39.962985-05:
      DOI: 10.1002/2016WR019072
  • Bayesian analysis of stage‐fall‐discharge rating curves and
           their uncertainties
    • Authors: V. Mansanarez; J. Le Coz, B. Renard, M. Lang, G. Pierrefeu, P. Vauchel
      Abstract: Stage‐fall‐discharge (SFD) rating curves are traditionally used to compute streamflow records at sites where the energy slope of the flow is variable due to variable backwater effects. We introduce a model with hydraulically interpretable parameters for estimating SFD rating curves and their uncertainties. Conventional power functions for channel and section controls are used. The transition to a backwater‐affected channel control is computed based on a continuity condition, solved either analytically or numerically. The practical use of the method is demonstrated with two real twin‐gauge stations, the Rhône River at Valence, France, and the Guthusbekken stream at station 0003⋅0033, Norway. Those stations are typical of a channel control and a section control, respectively, when backwater‐unaffected conditions apply. The performance of the method is investigated through sensitivity analysis to prior information on controls and to observations (i.e., available gaugings) for the station of Valence. These analyses suggest that precisely identifying SFD rating curves requires adapted gauging strategy and/or informative priors. The Madeira River, one of the largest tributaries of the Amazon, provides a challenging case typical of large, flat, tropical river networks where bed roughness can also be variable in addition to slope. In this case, the difference in staff gauge reference levels must be estimated as another uncertain parameter of the SFD model. The proposed Bayesian method is a valuable alternative solution to the graphical and empirical techniques still proposed in hydrometry guidance and standards.
      PubDate: 2016-09-29T08:25:59.986293-05:
      DOI: 10.1002/2016WR018916
  • Cumulative Relative Reactivity: A Concept for Modeling Aquifer‐Scale
           Reactive Transport
    • Authors: Matthias Loschko; Thomas Wöhling, David L. Rudolph, Olaf A. Cirpka
      Abstract: We simulate aquifer‐scale reactive transport using an approach based on travel times and relative reactivity. The latter quantifies the intensity of the chemical reaction relative to a reference reaction rate with identical concentrations and can be interpreted as the strength of electron‐donor (or electron‐acceptor) release by the matrix, scaled by a reference release. In general, the relative reactivity is a spatially variable property reflecting the geology of the formation. In the proposed approach, we track the path of individual water parcels through the aquifer and evaluate the age of the water parcels and the relative reactivity integrated along their trajectories. By switching from spatial discretization to cumulative relative reactivity, advective‐reactive transport can be simulated by solving a single system of ordinary differential equations for each combination of concentrations in the inflow. We test the validity of the approach in a two‐dimensional test case of steady‐state groundwater flow and reactive transport involving aerobic respiration and denitrification. Here we compare steady‐state concentration distributions of the spatially explicit virtual truth, accounting for dispersive mixing, with the approximation based on cumulative relative reactivity and show that the errors introduced by neglecting dispersive mixing are minor if the target quantities are the mass fluxes crossing a control plane or being collected by a well. We further demonstrate the efficiency of the approach in a synthetic three‐dimensional case study. The proposed approach is computationally so efficient, that ensemble runs to assess statistical distributions of concentration time series of reactive solutes become feasible, which is not practical with a spatially explicit model. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-29T03:47:14.178739-05:
      DOI: 10.1002/2016WR019080
  • Flow reconstructions in the Upper Missouri River Basin using riparian tree
    • Authors: Derek M. Schook; Jonathan M. Friedman, Sara L. Rathburn
      Abstract: River flow reconstructions are typically developed using tree rings from montane conifers that cannot reflect flow regulation or hydrologic inputs from the lower portions of a watershed. Incorporating lowland riparian trees may improve the accuracy of flow reconstructions when these trees are physically linked to the alluvial water table. We used riparian plains cottonwoods (Populus deltoides, ssp. monilifera) to reconstruct discharge for three neighboring rivers in the Upper Missouri River Basin: the Yellowstone (n = 389 tree cores), Powder (n = 408), and Little Missouri Rivers (n = 643). We used the Regional Curve Standardization approach to reconstruct log‐transformed discharge over the four months in early summer that most highly correlated to tree ring growth. The reconstructions explained at least 57% of the variance in historical discharge and extended back to 1742, 1729 and 1643. These are the first flow reconstructions for the Lower Yellowstone and Powder Rivers, and they are the furthest downstream among Rocky Mountain rivers in the Missouri River Basin. Although mostly free‐flowing, the Yellowstone and Powder Rivers experienced a shift from early‐ to late‐summer flows within the last century. This shift is concurrent with increasing irrigation and reservoir storage, and it corresponds to decreased cottonwood growth. Low‐frequency flow patterns revealed wet conditions from 1870‐1980, a period that includes the majority of the historical record. The 1816‐1823 and 1861‐1865 droughts were more severe than any recorded, revealing that drought risks are underestimated when using the instrumental record alone. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-29T03:41:06.716445-05:
      DOI: 10.1002/2016WR018845
  • Importance of soil heating, liquid water loss, and vapor flow enhancement
           for evaporation
    • Authors: Michael D. Novak
      Abstract: Field measurements conducted by Cahill and Parlange [1998] are reanalyzed to verify if their conclusion that daytime peak values of 60–70 W m−2 of latent heat flux divergence occurred in the 7–10 cm soil layer of a drying Yolo silt loam when maximum values of surface latent heat flux are estimated to have been about 100 W m−2. The new analyses, as similar to theirs as possible, are validated using a numerical simulation of coupled soil moisture and heat flow based on Philip and de Vries [1957] as a test bed. The numerical simulation is extended to include the flow of air induced by diurnal soil heating and evaporative water loss to verify the flux divergence calculations reported in Parlange et al. [1998] that explained the findings of Cahill and Parlange [1998]. It is shown that the conclusions of both of these papers are in error, so that the original version of the Philip and de Vries [1957] theory is consistent with their field measurements after all and the effects of air flow associated with soil heating and liquid water loss (and low frequency barometric pressure variations also considered) are negligible in practice. In an additional investigation enhancement of diffusive vapor flow (first postulated by Philip and de Vries [1957]) and discussed extensively in the literature since is shown to have negligible effects on cumulative evaporation under field conditions. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-28T03:21:31.101672-05:
      DOI: 10.1002/2016WR018874
  • Excess warming of a central European lake driven by solar brightening
    • Authors: M. Schmid; O. Köster
      Abstract: Recent trends in summer surface temperatures of many lakes exceed the corresponding air temperature trends. This disagrees with expectations from lake surface heat budgets, which predict that lake surface temperatures should increase by 75 to 90% of the increase in air temperatures. Here we investigate the causes for this excess warming for Lower Lake Zurich, a representative deep and stratified Central European lake, by a combined data analysis and modelling approach. Lake temperatures are simulated using a one‐dimensional vertical model driven by 33 years of homogenized meteorological data. The model is calibrated and validated using an equally long time series of monthly water temperature profiles. The effects of individual forcing parameters are investigated by scenarios where the trends of single variables are retained while those of all other forcing variables are removed. The results show that ∼60% of the observed warming of spring and summer lake surface temperatures were caused by increased air temperature and ∼40% by increased solar radiation. The effects of the trends of all other forcing variables were small. Following projections of climate models, the increasing trends in solar radiation, and consequently the excess warming of lake surface temperatures, are not likely to continue in the future. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-28T03:21:30.038867-05:
      DOI: 10.1002/2016WR018651
  • Characterization of reactive transport by 3D electrical resistivity
           tomography (ERT) under unsaturated conditions
    • Authors: Markus Wehrer; Andrew Binley, Lee D. Slater
      Abstract: The leaching of nitrate from intensively used arable soil is of major concern in many countries. In this study we show how time lapse electrical resistivity tomography (ERT) can be used to characterize spatially heterogeneous processes of ion production, consumption and transport in soils. A controlled release fertilizer was introduced into an undisturbed soil core in a laboratory lysimeter and subjected to infiltration events. The production of ions resulting from processes associated with nitrification and their transport through the soil core was observed by time lapse ERT and analysis of seepage water samples from a multicompartment sampler. ERT images show development and propagation of a high conductivity plume from the fertilizer source zone. Molar amounts of nitrate produced in and exported from the soil core could be well reproduced by time lapse ERT using a spatial moment analysis. Furthermore, we observed that several shape measures of local breakthrough‐curves (BTCs) of seepage water conductivity and nitrate derived by effluent analyses and BTCs of bulk conductivity derived by ERT are highly correlated, indicating the preservation of spatial differences of the plume breakthrough in the ERT data. Also differences between nitrate breakthrough and a conservative tracer breakthrough can be observed by ERT. However, the estimation of target ion concentrations by ERT is errorbound and the smoothing algorithm of the inversion masks spatial conductivity differences. This results in difficulties reproducing spatial differences of ion source functions and variances of travel times. Despite the observed limitations, we conclude that time lapse ERT can be qualitatively and quantitatively informative with respect to processes affecting the fate of nitrate in arable soils. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-28T03:21:28.575394-05:
      DOI: 10.1002/2016WR019300
  • Most computational hydrology is not reproducible, so is it really
    • Authors: Christopher Hutton; Thorsten Wagener, Jim Freer, Dawei Han, Chris Duffy, Berit Arheimer
      Abstract: Reproducibility is a foundational principle in scientific research. Yet in computational hydrology, the code and data that actually produces published results is not regularly made available, inhibiting the ability of the community to reproduce and verify previous findings. In order to overcome this problem we recommend that re‐useable code and formal workflows, which unambiguously reproduce published scientific results, are made available for the community alongside data, so that we can verify previous findings, and build directly from previous work. In cases where reproducing large‐scale hydrologic studies is computationally very expensive and time‐consuming, new processes are required to ensure scientific rigour. Such changes will strongly improve the transparency of hydrological research, and thus provide a more credible foundation for scientific advancement and policy support. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-28T03:21:25.081114-05:
      DOI: 10.1002/2016WR019285
  • Optimizing embedded sensor network design for catchment‐scale
           snow‐depth estimation using LiDAR and machine learning
    • Authors: C. A. Oroza; Z. Zheng, S. D. Glaser, D. Tuia, R. C. Bales
      Abstract: We evaluate the accuracy of a machine‐learning algorithm that uses LiDAR data to identify optimal ground‐based sensor placements for catchment‐scale snow measurements. Sampling locations that best represent catchment physiographic variables are identified with the Expectation Maximization algorithm for a Gaussian mixture model. A Gaussian process is then used to model the snow depth in a 1‐km2 area surrounding the network, and additional sensors are placed to minimize the model uncertainty. The aim of the study is to determine the distribution of sensors that minimizes the bias and RMSE of the model. We compare the accuracy of the snow‐depth model using the proposed placements to an existing sensor network at the Southern Sierra Critical Zone Observatory. Each model is validated with a 1‐m2 LiDAR‐derived snow‐depth raster from March 14th, 2010. The proposed algorithm exhibits higher accuracy with fewer sensors (8 sensors, RMSE 38.3 cm, bias = 3.49 cm) than the existing network (23 sensors, RMSE 53.0 cm, bias = 15.5 cm) and randomized placements (8 sensors, RMSE 63.7 cm, bias = 24.7 cm). We then evaluate the spatial and temporal transferability of the method using 14 LiDAR scenes from two catchments within the JPL Airborne Snow Observatory. In each region, optimal sensor placements are determined using the first available snow raster for the year. The accuracy in the remaining LiDAR surveys is then compared to 100 configurations of sensors selected at random. We find the error statistics (bias and RMSE) to be more consistent across the additional surveys than the average random configuration. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-27T18:01:20.525896-05:
      DOI: 10.1002/2016WR018896
  • Merging radar and in situ rainfall measurements: An assessment of
           different combination algorithms
    • Authors: Mohammad Mahadi Hasan; Ashish Sharma, Fiona Johnson, Gregoire Mariethoz, Alan Seed
      Abstract: Merging radar and gauge rainfall estimates is an area of active research. Since rain gauges alone are often limited at representing the complete spatial distribution of rainfall, a combination of radar derived rainfall with spatially interpolated gauge estimates using alternate weighting approaches is investigated. This paper examines several merging methods that differ in the consideration of correlation among the estimation errors, their distribution and the application of dynamic and static weighting. The merging process has been applied to the radar data from Terrey Hills radar located in Sydney, Australia and spatially interpolated gauge rainfall on the same area. The performance of the merging methods is assessed by comparing the combined estimate with the gauge observation. It is however clear from our findings that rainfall estimation from any of the combination approaches assessed contains less error than any of the non‐combination approaches. The results show that the correlation between these two rainfall estimation errors plays a significant role in the performance of the merging methods. The combination method should be chosen depending on the purpose, accuracy of the estimate and complexity of the method. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-27T18:01:18.824985-05:
      DOI: 10.1002/2015WR018441
  • Runoff of small rocky headwater catchments: Field observations and
           hydrological modeling
    • Authors: C. Gregoretti; M. Degetto, M. Bernard, G. Crucil, A. Pimazzoni, G. Devido, M. Berti, A. Simoni, S. Lanzoni
      Abstract: In dolomitic headwater catchments, intense rainstorms of short duration produce runoff discharges that often trigger debris flows on the scree slopes at the base of rock cliffs. In order to measure these discharges, we placed a measuring facility at the outlet (elevation 1770 m a.s.l.) of a small, rocky headwater catchment (area ∼ 0.032 km2, average slope ∼ 320%) located in the Venetian Dolomites (North Eastern Italian Alps). The facility consists of an approximately rectangular basin, ending with a sharp‐crested weir. Six runoff events were recorded in the period 2011‐2014, providing a unique opportunity for characterizing the hydrological response of the catchment. The measured hydrographs display impulsive shapes, with an abrupt raise up to the peak, followed by a rapidly decreasing tail, until a nearly constant plateau is eventually reached. This behavior can be simulated by means of a distributed hydrological model if the excess rainfall is determined accurately. We show that using the Soil Conservation Service Curve‐Number (SCS‐CN) method and assuming a constant routing velocity invariably results in an underestimated peak flow and a delayed peak time. A satisfactory prediction of the impulsive hydrograph shape including peak value and timing is obtained only by combining the SCS‐CN procedure with a simplified version of the Horton equation, and simulating runoff routing along the channel network through a matched diffusivity kinematic wave model. The robustness of the proposed methodology is tested through a comparison between simulated and observed timings of runoff or debris flow occurrence in two neighboring alpine basins. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-27T17:56:12.899359-05:
      DOI: 10.1002/2016WR018675
  • Particle selectivity of sediment deposited over grass barriers and the
           effect of rainfall
    • Authors: Chengzhong Pan; Lan Ma, John Wainwright
      Abstract: Particle selectivity of the sediment deposited over vegetative barriers is of importance to predict sediment transport and particulate pollutant load into surface waters. Grassed barriers with 20%, 40%, 60%, 70% and 90% covers at 15° slope were subjected to silt‐laden inflows in the presence and absence of simulated rainfalls to investigate the sediment deposition processes. The results show that re‐grass of steep croplands can effectively trap eroded sediment from upslope, and the rowed grass barriers can strengthen sediment deposition. The deposition order of sediment particle sizes (μm) follows (>50)> (25‐50)>(10‐25)=((2‐10), and the particle selectivity weakens with increasing grass covers. Clay particles had a similar deposition efficiency to overall sediment, implying the effectiveness of re‐grass in controlling soil nutrient loss. The contribution of grass to total overland flow resistance is almost equivalent to the percentage of grass cover. For steep grassed slopes, raindrop impact significantly decreases sediment deposition, but limitedly affects particle selectivity of deposited sediment and overland flow hydraulics. Both raindrop kinetic energy and stream power available for surface soil contribute to sediment deposition in net deposition areas of grass barriers. These imply that rainfall effect on sediment delivery over vegetated barriers derives from the additional raindrop energy, rather than the variation in runoff hydraulics. These results can help to clarify the effect of raindrop impact on sediment transport and to evaluate the benefit of re‐vegetation in decreasing sediment yield and its particulate nutrient load into surface waters. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-27T03:25:50.590579-05:
      DOI: 10.1002/2016WR019010
  • Accounting for the influence of vegetation and landscape improves model
           transferability in a tropical savannah region
    • Authors: Hongkai Gao; Markus Hrachowitz, Nutchanart Sriwongsitanon, Fabrizio Fenicia, Shervan Gharari, Hubert H. G. Savenije
      Abstract: Understanding which catchment characteristics dominate hydrologic response and how to take them into account remains a challenge in hydrological modeling, particularly in ungaged basins. This is even more so in non‐temperate and non‐humid catchments, where ‐ due to the combination of seasonality and the occurrence of dry spells ‐ threshold processes are more prominent in rainfall runoff behavior. An example is the tropical savannah, the second largest climatic zone, characterized by pronounced dry and wet seasons and high evaporative demand. In this study, we investigated the importance of landscape variability on the spatial variability of stream flow in tropical savannah basins. We applied a stepwise modeling approach to 23 sub‐catchments of the Upper Ping River in Thailand, where gradually more information on landscape was incorporated. The benchmark is represented by a classical lumped model (FLEXL), which does not account for spatial variability. We then tested the effect of accounting for vegetation information within the lumped model (FLEXLM), and subsequently two semi‐distributed models: one accounting for the spatial variability of topography‐based landscape features alone (FLEXT), and another accounting for both topographic features and vegetation (FLEXTM). In cross‐validation, each model was calibrated on one catchment, and then transferred with its fitted parameters to the remaining catchments. We found that when transferring model parameters in space, the semi‐distributed models accounting for vegetation and topographic heterogeneity clearly outperformed the lumped model. This suggests that landscape controls a considerable part of the hydrological function and explicit consideration of its heterogeneity can be highly beneficial for prediction in ungaged basins in tropical savannah. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-27T03:25:45.389296-05:
      DOI: 10.1002/2016WR019574
  • Valley and channel networks extraction based on local topographic
           curvature and K‐means clustering of contours
    • Authors: Milad Hooshyar; Dingbao Wang, Seoyoung Kim, Stephen C. Medeiros, Scott C. Hagen
      Abstract: A method for automatic extraction of valley and channel networks from high‐resolution digital elevation models (DEMs) is presented. This method utilizes both positive (i.e., convergent topography) and negative (i.e., divergent topography) curvature to delineate the valley network. The valley and ridge skeletons are extracted using the pixels' curvature and the local terrain conditions. The valley network is generated by checking the terrain for the existence of at least one ridge between two intersecting valleys. The transition from unchannelized to channelized sections (i.e., channel head) in each 1st‐order valley tributary is identified independently by categorizing the corresponding contours using an unsupervised approach based on K‐means clustering. The method does not require a spatially constant channel initiation threshold (e.g., curvature or contributing area). Moreover, instead of a point attribute (e.g., curvature), the proposed clustering method utilizes the shape of contours, which reflects the entire cross‐sectional profile including possible banks. The method was applied to three catchments: Indian Creek and Mid Bailey Run in Ohio, and Feather River in California. The accuracy of channel head extraction from the proposed method is comparable to state‐of‐the‐art channel extraction methods. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-27T03:21:34.325634-05:
      DOI: 10.1002/2015WR018479
  • Flipping the thin film model: Mass transfer by hyporheic exchange in
           gaining and losing streams
    • Authors: Alexander H. McCluskey; Stanley B. Grant, Michael J. Stewardson
      Abstract: The exchange of mass between a stream and its hyporheic zone, or “hyporheic exchange”, is central to many important ecosystem services. In this paper we show that mass transfer across the streambed by linear mechanisms of hyporheic exchange in a gaining or losing stream can be represented by a thin film model in which: (a) the mass transfer coefficient is replaced with the average Darcy flux of water downwelling into the sediment; and (b) the driving force for mass transfer is “flipped” from normal to the surface (concentration difference across a boundary layer) to parallel to the surface (concentration difference across downwelling and upwelling zones). Our analysis is consistent with previously published analytical, computational, and experimental studies of hyporheic exchange in the presence of stream‐groundwater interactions, and links stream network, advection‐dispersion, and stochastic descriptions of solute fate and transport in rivers. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-26T10:45:29.172894-05:
      DOI: 10.1002/2016WR018972
  • Evaluation of mercury cycling and hypolimnetic oxygenation in
           mercury‐impacted seasonally stratified reservoirs in the Guadalupe River
           watershed, California
    • Authors: Stephen A. McCord; Marc W. Beutel, Stephen R. Dent, S. Geoffrey Schladow
      Abstract: Surface water reservoirs trap inorganic mercury delivered from their watersheds, create conditions that convert inorganic mercury to highly toxic methylmercury (MeHg), and host sportfish in which MeHg bioaccumulates. The Santa Clara Valley Water District (District) actively manages and monitors four mercury‐impaired reservoirs that help to serve communities in South San Francisco Bay, California. The Guadalupe River watershed, which contains three of those reservoirs, also includes the New Almaden mercury‐mining district, the largest historic mercury producer in North America. Monthly vertical profiles of field measurements and grab samples in years 2011‐2013 portray annual cycling of density stratification, dissolved oxygen (DO), and MeHg. Monitoring results highlight the role that hypolimnetic hypoxia plays in MeHg distribution in the water column, as well as the consistent, tight coupling between MeHg in ecological compartments (water, zooplankton and bass) across the four reservoirs. Following the 2011‐2013 monitoring period, the District designed and installed hypolimnetic oxygenation systems (HOS) in the four reservoirs in an effort to repress MeHg buildup in bottom waters and attain regulatory targets for MeHg in water and fish tissue. Initial HOS operation in Calero Reservoir in 2014 enhanced bottom water DO and depressed hypolimnetic buildup of MeHg, but did not substantially decrease mercury levels in zooplankton or small fish. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-26T10:45:28.044209-05:
      DOI: 10.1002/2016WR019061
  • The direct and indirect effects of watershed land use and soil type on
           stream water metal concentrations
    • Authors: M. Taka; J. Aalto, J. Virkanen, M. Luoto
      Abstract: Identifying the factors controlling stream water pollutants is challenged by the diversity of potential sources, pathways, and processes. This study tests the effects of watershed characteristics on stream water metal concentrations across environmental gradients. By using an extensive data set of 83 watersheds in southern Finland and structural equation modeling (SEM), the direct and indirect effects of land use and soil type on metal concentrations were explored. Both land use and soil type resulted in statistically significant direct effects on metals; for example land use was found to control dissolved metal concentrations, whereas soil type had the strongest links for total metal concentrations. The consideration of indirect correlation further strengthened the effects of soil type up to 50%, thus suggesting the dominant role of soil across land use intensities. Moreover, the results indicate that modified landscapes mediate the effect of natural soil processes in controlling stream metal concentrations. This work highlights the benefits of structural equation model framework, as the underlying paths for water quality are more likely to be identified, compared to traditional regression methods. Thus the implementation of SEM on water quality studies is highly encouraged. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-26T10:45:24.293872-05:
      DOI: 10.1002/2016WR019226
  • Modeling multidomain hydraulic properties of shrink‐swell soils
    • Authors: Ryan D. Stewart; Majdi R. Abou Najm, David E. Rupp, John S. Selker
      Abstract: Shrink‐swell soils crack and become compacted as they dry, changing properties such as bulk density and hydraulic conductivity. Multi‐domain models divide soil into independent realms that allow soil cracks to be incorporated into classical flow and transport models. Incongruously, most applications of multi‐domain models assume that the porosity distributions, bulk density, and effective saturated hydraulic conductivity of the soil are constant. This study builds on a recently derived soil shrinkage model to develop a new multi‐domain, dual‐permeability model that can accurately predict variations in soil hydraulic properties due to dynamic changes in crack size and connectivity. The model only requires estimates of soil gravimetric water content and a minimal set of parameters, all of which can be determined using laboratory and/or field measurements. We apply the model to eight clayey soils, and demonstrate its ability to quantify variations in volumetric water content (as can be determined during measurement of a soil water characteristic curve) and transient saturated hydraulic conductivity, Ks (as can be measured using infiltration tests). The proposed model is able to capture observed variations in Ks of one to more than two orders of magnitude. In contrast, other dual‐permeability models assume that Ks is constant, resulting in the potential for large error when predicting water movement through shrink‐swell soils. Overall, the multi‐domain model presented here successfully quantifies fluctuations in the hydraulic properties of shrink‐swell soil matrices, and are suitable for use in physical flow and transport models based on Darcy's Law, the Richards Equation, and the advection‐dispersion equation. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-26T10:45:20.848349-05:
      DOI: 10.1002/2016WR019336
  • Using web‐based observations to identify thresholds of a person's
           stability in a flow
    • Authors: L. Milanesi; M. Pilotti, B. Bacchi
      Abstract: Flood risk assessment and mitigation are important tasks that should take advantage of rational vulnerability models to increase their effectiveness. These models are usually identified through a relevant set of laboratory experiments. However, there is growing evidence that these tests are not fully representative of the variety of conditions that characterize real flood hazard situations. This paper suggests a citizen science based and innovative approach to obtain information from web resources for the calibration of people's vulnerability models.A comprehensive study employing commonly‐used web engines allowed the collection of a wide set of documents showing real risk situations for people impacted by flood, classified according to the stability of the involved subjects. A procedure to extrapolate the flow depth and velocity from the video frames is developed and its reliability is verified by comparing the results with observation. The procedure is based on the statistical distribution of the population height employing a direct uncertainty propagation method. The results complement the experimental literature data and conceptual models. The growing availability of online information will progressively increase the sample size of the sample on which the procedure is based and will eventually lead to the identification of a probability surface describing the transition between stability and instability conditions of individuals in a flow. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-26T01:50:28.44812-05:0
      DOI: 10.1002/2016WR019182
  • An extended JBN method of determining unsteady state two‐phase
           relative permeability
    • Authors: Xiongyu Chen; Amir Kianinejad, David A. DiCarlo
      Abstract: Relative permeability is the reduction of permeability of porous media when subjected to multi‐phase flow and a key parameter in subsurface hydrology. The JBN method [Welge, 1952; Johnson et al., 1959] is a well‐known method of obtaining relative permeability, which measures the overall pressure drop and the effluent phase ratio versus time during two‐phase displacements. By assuming no capillary pressure or gravity, the JBN method obtains the relative permeabilities to both phases at the core outlet. Since data across a range of saturations are acquired in a relatively short time, this method is widely used. This work extends the JBN method by having (1) section‐wise pressure drop measurements between the core inlet, four pressure taps on the core and the outlet, (2) local saturation measurements, and (3) local phase fluxes. With these data, the extended JBN method can determine relative permeabilities to both phases at each pressure tap of the core (not just at the core outlet). The JBN extension is shown using a data set where CO2 invades a brine‐filled core. From this it is found that the advantages of the extended JBN method over the regular JBN method are: (1) four times more data are obtained, and (2) data are more accurate because the capillary end effect is experimentally avoided. Avoiding the end effect results in tripling the saturation range, and obtaining relative permeabilities that are consistent with steady‐state measurements and roughly 40% higher than those from the regular JBN method. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-26T01:50:25.5365-05:00
      DOI: 10.1002/2016WR019204
  • Vertical dispersion in vegetated shear flows
    • Authors: Simonetta Rubol; Ilenia Battiato, Felipe P. J. de Barros
      Abstract: Canopy layers control momentum and solute transport to and from the overlying water surface layer. These transfer mechanisms strongly dependent on canopy geometry, affect the amount of solute in the river, the hydrological retention and availability of dissolved solutes to organisms located in the vegetated layers and are critical to improve water quality. In this work we consider steady‐state transport in a vegetated channel under fully‐developed flow conditions. Under the hypothesis that the canopy layer can be described as an effective porous medium with prescribed properties, i.e. porosity and permeability, we model solute transport above and within the vegetated layer with an advection‐dispersion equation with a spatially variable dispersion coefficient (diffusivity). By means of the Generalized Integral Transform Technique, we derive a semi‐analytical solution for the concentration field in submerged vegetated aquatic systems. We show that canopy layer's permeability affects the asymmetry of the concentration profile, the effective vertical spreading behavior, and the magnitude of the peak concentration. Due to its analytical features, the model has a low computational cost. The proposed solution successfully reproduces previously published experimental data. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-26T01:50:24.250521-05:
      DOI: 10.1002/2016WR018907
  • Two and a half years of country‐wide rainfall maps using radio links
           from commercial cellular telecommunication networks
    • Authors: A. Overeem; H. Leijnse, R. Uijlenhoet
      Abstract: Although rainfall estimation employing microwave links from cellular telecommunication networks is recognized as a new promising measurement technique, its potential for long‐term large‐scale operational rainfall monitoring remains to be demonstrated. This study contributes to this endeavor by deriving a continuous series of rainfall maps from a large 2.5 year microwave link data set of, on average, 3383 links (2044 link paths) covering The Netherlands (∼3.5 × 104 km2), a midlatitude country (∼5° E, ∼52° N) with a temperate climate. Maps are extensively verified against an independent gauge‐adjusted radar rainfall data set for different temporal (15 min, 1 hour, 1 day, 1 month) and spatial (0.9, 74 km2) scales. The usefulness of different steps in the rainfall retrieval algorithm, i.c. a wet‐dry classification method and a filter to remove outliers, is systematically assessed. A novel dew filter is developed to correct for dew‐induced wet antenna attenuation, which, although a relative underestimation of 6% to 9% is found, generally yields good results. The microwave link rainfall estimation technique performs well for the summer months (June, July, August), even outperforming interpolation of automatic rain gauge data (with a density of ∼1 gauge per 1000 km2), but large deviations are found for the winter months (December, January, February). These deviations are generally expected to be related to frozen or melting precipitation. Hence, our results show the potential of commercial microwave links for long‐term large‐scale operational rainfall monitoring. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-21T03:50:35.071759-05:
      DOI: 10.1002/2016WR019412
  • Adaptive mixed finite element methods for Darcy flow in fractured porous
    • Authors: Huangxin Chen; Amgad Salama, Shuyu Sun
      Abstract: In this paper, we propose adaptive mixed finite element methods for simulating the single‐phase Darcy flow in two‐dimensional fractured porous media. The reduced model that we use for the simulation is a discrete fracture model coupling Darcy flows in the matrix and the fractures, and the fractures are modeled by one‐dimensional entities. The Raviart‐Thomas mixed finite element methods are utilized for the solution of the coupled Darcy flows in the matrix and the fractures. In order to improve the efficiency of the simulation, we use adaptive mixed finite element methods based on novel residual‐based a posteriori error estimators. In addition, we develop an efficient upscaling algorithm to compute the effective permeability of the fractured porous media. Several interesting examples of Darcy flow in the fractured porous media are presented to demonstrate the robustness of the algorithm. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-21T03:50:24.871236-05:
      DOI: 10.1002/2015WR018450
  • Mapping high‐resolution soil moisture and properties using distributed
           temperature sensing data and an adaptive Particle Batch Smoother
    • Authors: Jianzhi Dong; Susan C. Steele‐Dunne, Tyson E. Ochsner, Christine E. Hatch, Chadi Sayde, John Selker, Scott Tyler, Michael H. Cosh, Nick van de Giesen
      Abstract: This study demonstrated a new method for mapping high resolution (spatial: 1 m, and temporal: 1 hour) soil moisture by assimilating distributed temperature sensing (DTS) observed soil temperatures at intermediate scales. In order to provide robust soil moisture and property estimates, we first proposed an adaptive particle batch smoother algorithm (APBS). In the APBS, a tuning factor, which can avoid severe particle weight degeneration, is automatically determined by maximizing the reliability of the soil temperature estimates of each batch window. A multiple truth synthetic test was used to demonstrate the APBS can robustly estimate soil moisture and properties using observed soil temperatures at two shallow depths. The APBS algorithm was then applied to DTS data along a 71 m transect, yielding an hourly soil moisture map with meter resolution. Results show the APBS can draw the prior guessed soil hydraulic and thermal properties significantly closer to the field measured reference values. The improved soil properties in turn remove the soil moisture biases between the prior guessed and reference soil moisture, which was particularly noticeable at depth above 20 cm. This high resolution soil moisture map demonstrates the potential of characterizing soil moisture temporal and spatial variability and reflects patterns consistent with previous studies conducted using intensive point scale soil moisture samples. The intermediate scale high spatial resolution soil moisture information derived from the DTS may facilitate remote sensing soil moisture product calibration and validation. In addition, the APBS algorithm proposed in this study would also be applicable to general hydrological data assimilation problems for robust model state and parameter estimation. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-21T03:50:20.334108-05:
      DOI: 10.1002/2016WR019031
  • A Bayesian hierarchical nonhomogeneous hidden Markov model for multisite
           streamflow reconstructions
    • Authors: C. Bracken; B. Rajagopalan, C. Woodhouse
      Abstract: In many complex water supply systems, the next generation of water resources planning models will require simultaneous probabilistic streamflow inputs at multiple locations on an interconnected network. To make use of the valuable multi‐century records provided by tree‐ring data, reconstruction models must be able to produce appropriate multisite inputs. Existing streamflow reconstruction models typically focus on one site at a time, not addressing intersite dependencies and potentially misrepresenting uncertainty. To this end, we develop a model for multisite streamflow reconstruction with the ability to capture intersite correlations. The proposed model is a hierarchical Bayesian nonhomogeneous hidden Markov model (NHMM). A NHMM is fit to contemporary streamflow at each location using lognormal component distributions. Leading principal components of tree rings are used as covariates to model nonstationary transition probabilities and the parameters of the lognormal component distributions. Spatial dependence between sites is captured with a Gaussian elliptical copula. Parameters of the model are estimated in a fully Bayesian framework, in that marginal posterior distributions of all the parameters are obtained. The model is applied to reconstruct flows at 20 sites in the Upper Colorado River Basin (UCRB) from 1473‐1906. Many previous reconstructions are available for this basin, making it ideal for testing this new method. The results show some improvements over regression‐based methods in terms of validation statistics. Key advantages of the Bayesian NHMM over traditional approaches are a dynamic representation of uncertainty and the ability to make long multisite simulations that capture at‐site statistics and spatial correlations between sites. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-20T18:45:22.261841-05:
      DOI: 10.1002/2016WR018887
  • Analyses of infrequent (quasi‐decadal) large groundwater recharge events
           in the northern Great Basin: Their importance for groundwater
           availability, use, and management
    • Authors: Melissa D. Masbruch; Christine A. Rumsey, Subhrendu Gangopadhyay, David D. Susong, Tom Pruitt
      Abstract: There has been a considerable amount of research linking climatic variability to hydrologic responses in the western United States. Although much effort has been spent to assess and predict changes in surface‐water resources, little has been done to understand how climatic events and changes affect groundwater resources. This study focuses on characterizing and quantifying the effects of large, multi‐year, quasi‐decadal groundwater recharge events in the northern Utah portion of the Great Basin for the period 1960 to 2013. Annual groundwater level data were analyzed with climatic data to characterize climatic conditions and frequency of these large recharge events. Using observed water‐level changes and multivariate analysis, five large groundwater recharge events were identified with a frequency of about 11 to 13 years. These events were generally characterized as having above‐average annual precipitation and snow water equivalent and below‐average seasonal temperatures, especially during the spring (April through June). Existing groundwater flow models for several basins within the study area were used to quantify changes in groundwater storage from these events. Simulated groundwater storage increases per basin from a single recharge event ranged from about 115 Mm3 to 205 Mm3. Extrapolating these amounts over the entire northern Great Basin indicates that a single large quasi‐decadal recharge event could result in billions of cubic meters of groundwater storage. Understanding the role of these large quasi‐decadal recharge events in replenishing aquifers and sustaining water supplies is crucial for long‐term groundwater management. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-19T18:30:24.787137-05:
      DOI: 10.1002/2016WR019060
  • Inferring changes in water cycle dynamics of intensively managed
           landscapes via the theory of time‐variant travel time distributions
    • Authors: Mohammad Danesh‐Yazdi; Efi Foufoula‐Georgiou, Diana L. Karwan, Gianluca Botter
      Abstract: Climatic trends and anthropogenic changes in land cover and land‐use are impacting the hydrology and water quality of streams at the field, watershed, and regional scales in complex ways. In poorly drained agricultural landscapes, subsurface drainage systems have been successful in increasing crop productivity by removing excess soil moisture. However, their hydro‐ecological consequences are still debated in view of the observed increased concentrations of nitrate, phosphorus, and pesticides in many streams, as well as altered runoff volumes and timing. In this study we employ the recently developed theory of time‐variant travel time distributions within the storage selection function framework to quantify changes in water cycle dynamics resulting from the combined climate and land‐use changes. Our results from analysis of a sub‐basin in the Minnesota River Basin indicate a significant decrease in the mean travel time of water in the shallow subsurface layer during the growing season under current conditions compared to the pre‐1970's conditions. We also find highly damped year‐to‐year fluctuations in the mean travel time, which we attribute to the “homogenization” of the hydrologic response due to artificial drainage. The dependence of the mean travel time on the spatial heterogeneity of some soil characteristics as well as on the basin scale is further explored via numerical experiments. Simulations indicate that the mean travel time is independent of scale for spatial scales larger than approximately 200 km2, suggesting that hydrologic data from larger basins may be used to infer the average of smaller‐scale driven changes in water cycle dynamics. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-19T10:51:31.826679-05:
      DOI: 10.1002/2016WR019091
  • Laboratory flume experiments with the Swiss plate geophone bedload
           monitoring system. Part I: Impulse counts and particle size identification
    • Authors: Carlos R. Wyss; Dieter Rickenmann, Bruno Fritschi, Jens M. Turowski, Volker Weitbrecht, Robert M. Boes
      Abstract: We performed systematic flume experiments using natural bedload particles to quantify the effect of different parameters on the signal registered by the Swiss plate geophone, a bedload surrogate monitoring system. It was observed that the number of impulses computed from the raw signal clearly depends on bed particle size, mean flow velocity, bed roughness, and to a minor extent on particle shape. The centroid frequency of the signal resulting from the collision of a bedload particle against the geophone plate was found to be inversely related to particle size but to be less sensitive to variations in mean flow velocity and bed roughness than the signal amplitude, which is also related to particle size. Combining frequency and amplitude information resulted in a more robust identification of the transported particles size over a wide range of sizes than using amplitude information alone. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-16T18:15:39.333529-05:
      DOI: 10.1002/2015WR018555
  • Analytical approximations for effective relative permeability in the
           capillary limit
    • Authors: Avinoam Rabinovich; Boxiao Li, Louis J. Durlofsky
      Abstract: We present an analytical method for calculating two‐phase effective relative permeability, krjeff, where j designates phase (here CO2 and water), under steady state and capillary limit assumptions. These effective relative permeabilities may be applied in experimental settings and for upscaling in the context of numerical flow simulations, e.g., for CO2 storage. An exact solution for effective absolute permeability, keff, in two‐dimensional log‐normally distributed isotropic permeability (k) fields is the geometric mean. We show that this does not hold for since log normality is not maintained in the capillary limit phase permeability field (kkrj) when capillary pressure, and thus the saturation field, is varied. Nevertheless, the geometric mean is still shown to be suitable for approximating krjeff when the variance of ln k is low. For high variance cases, we apply a correction to the geometric‐average gas effective relative permeability using a Winsorized mean, which neglects large and small Kj values symmetrically. The analytical method is extended to anisotropically correlated log‐normal permeability fields using power law averaging. In these cases the Winsorized mean treatment is applied to the gas curves for cases described by negative power law exponents (flow across incomplete layers). The accuracy of our analytical expressions for is demonstrated through extensive numerical tests, using low‐ and high‐variance permeability realizations with a range of correlation structures. We also present integral expressions for geometric‐mean and power law average krjeff for the systems considered, which enable derivation of closed‐form series solutions for without generating permeability realizations. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-16T18:15:37.563752-05:
      DOI: 10.1002/2016WR019234
  • On river‐floodplain interaction and hydrograph skewness
    • Authors: Ayan Fleischmann; Rodrigo C. D. Paiva, Walter Collischonn, Mino V. Sorribas, Paulo R. M. Pontes
      Abstract: Understanding hydrological processes occurring within a basin by looking at its outlet hydrograph can improve and foster comprehension of ungauged regions. In this context, we present an extensive examination of the roles that floodplains play on driving hydrograph shapes. Observations of many river hydrographs with large floodplain influence are carried out and indicate that a negative skewness of the hydrographs is present among many of them. Through a series of numerical experiments and analytical reasoning, we show how the relationship between flood wave celerity and discharge in such systems is responsible for determining the hydrograph shapes. The more water inundates the floodplains upstream of the observed point, the more negatively skewed is the observed hydrograph. A case study is performed in the Amazon River Basin, where major rivers with large floodplain attenuation (e.g. Purus, Madeira and Juruá) are identified with higher negative skewness in the respective hydrographs. Finally, different wetland types could be distinguished by using this feature, e.g., wetlands maintained by endogenous processes, from wetlands governed by overbank flow (along river floodplains). A metric of hydrograph skewness was developed to quantify this effect, based on the time derivative of discharge. Together with the skewness concept, it may be used in other studies concerning the relevance of floodplain attenuation in large, ungauged rivers, where remote sensing data (e.g., satellite altimetry) can be very useful. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-16T10:11:08.598416-05:
      DOI: 10.1002/2016WR019233
  • Improving the realism of hydrologic model functioning through multivariate
           parameter estimation
    • Authors: O. Rakovec; R. Kumar, S. Attinger, L. Samaniego
      Abstract: Increased availability and quality of near real‐time observations provide the opportunity to improve understanding of predictive skills of hydrologic models. Recent studies have shown the limited capability of river discharge data alone to adequately constrain different components of distributed model parameterizations. In this study, the GRACE satellite‐based total water storage (TWS) anomaly is used to complement the discharge data with the aim to improve the fidelity of mesoscale hydrologic model (mHM) through multivariate parameter estimation. The study is conducted on 83 European basins covering a wide range of hydro‐climatic regimes. The model parameterization complemented with the TWS anomalies leads to statistically significant improvements in (1) discharge simulations during low‐flow period, and (2) evapotranspiration estimates which are evaluated against independent data (FLUXNET). Overall, there is no significant deterioration in model performance for the discharge simulations when complemented by information from the TWS anomalies. However, considerable changes in the partitioning of precipitation into runoff components are noticed by in‐/exclusion of TWS during the parameter estimation. Introducing monthly averaged TWS data only improves the dynamics of streamflow on monthly or longer time scales, which mostly addresses the dynamical behavior of the baseflow reservoir. A cross‐evaluation test carried out to assess the transferability of the calibrated parameters to other locations further confirms the benefit of complementary TWS data. In particular, the evapotranspiration estimates show more robust performance when TWS data are incorporated during the parameter estimation, in comparison with the benchmark model constrained against discharge only. This study highlights the value for incorporating multiple data sources during parameter estimation to improve the overall realism of hydrologic models and their applications over large domains. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-16T10:11:02.959422-05:
      DOI: 10.1002/2016WR019430
  • Laboratory flume experiments with the Swiss plate geophone bedload
           monitoring system. Part II: Application to field sites with direct bedload
    • Authors: Carlos R. Wyss; Dieter Rickenmann, Bruno Fritschi, Jens M. Turowski, Volker Weitbrecht, Eric Travaglini, Eric Bardou, Robert M. Boes
      Abstract: The Swiss plate geophone is a bedload surrogate monitoring system that had been calibrated in several gravel‐bed streams through field calibration measurements. Field calibration measurements are generally expensive and time consuming, therefore we investigated the possibility to replace it by a flume‐based calibration approach. We applied impulse‐diameter relations for the Swiss plate geophone obtained from systematic flume experiments to field calibration measurements in four different gravel‐bed streams. The flume‐based relations were successfully validated with direct bedload samples from field measurements, by estimating the number of impulses based on observed bedload masses per grain size class. We estimated bedload transport mass by developing flume‐based and stream‐dependent calibration procedures for the Swiss plate geophone system using an additional empirical function. The estimated masses are on average in the range of ±90% of measured bedload masses in the field, but the accuracy is generally improved for larger transported bedload masses. We discuss the limitations of the presented flume‐based calibration approach. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-16T10:11:01.636038-05:
      DOI: 10.1002/2016WR019283
  • Water pollution and income relationship: A seemingly unrelated partially
           linear analysis
    • Authors: Mahesh Pandit; Krishna P. Paudel
      Abstract: We used a seemingly unrelated partially linear model (SUPLM) to address a potential correlation between pollutants (nitrogen, phosphorous, dissolved oxygen and mercury) in an environmental Kuznets curve study. Simulation studies show that the SUPLM performs well to address potential correlation among pollutants. We find that the relationship between income and pollution follows an inverted U‐shaped curve for nitrogen and dissolved oxygen and a cubic shaped curve for mercury. Model specification tests suggest that a SUPLM is better specified compared to a parametric model to study the income‐pollution relationship. Results suggest a need to continually assess policy effectiveness of pollution reduction as income increases. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-16T10:10:56.01019-05:0
      DOI: 10.1002/2016WR018655
  • Measuring spatio‐temporal variation in snow optical grain size under a
           subalpine forest canopy using contact spectroscopy
    • Authors: Noah P. Molotch; David M. Barnard, Sean P. Burns, Thomas H. Painter
      Abstract: The distribution of forest cover exerts strong controls on the spatio‐temporal distribution of snow accumulation and snowmelt. The physical processes that govern these controls are poorly understood given a lack of detailed measurements of snow states. In this study, we address one of many measurement gaps by using contact spectroscopy to measure snow optical grain size at high spatial resolution in trenches dug between tree boles in a subalpine forest. Trenches were collocated with continuous measurements of snow depth and vertical profiles of snow temperature and supplemented with manual measurements of snow temperature, geometric grain size, grain type, and density from trench walls. There was a distinct difference in snow optical grain size between winter and spring periods. In winter and early spring, when facetted snow crystal types were dominant, snow optical grain size was 6% larger in canopy gaps versus under canopy positions; a difference that was smaller than the measurement uncertainty. By mid‐spring, the magnitude of snow optical grain size differences increased dramatically and patterns of snow optical grain size became highly directional with 34% larger snow grains in areas south versus north of trees. In winter, snow temperature gradients were up to 5 ‐ 15 °C m−1 greater under the canopy due to shallower snow accumulation. However, in canopy gaps, snow depths were greater in fall and early winter and therefore more significant kinetic growth metamorphism occurred relative to under canopy positions, resulting in larger snow grains in canopy gaps. Our findings illustrate the novelty of our method of measuring snow optical grain size, allowing for future studies to advance the understanding of how forest and meteorological conditions interact to impact snowpack evolution. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-16T10:10:41.467383-05:
      DOI: 10.1002/2016WR018954
  • Carbon dynamics in the hyporheic zone of a headwater mountain stream in
           the Cascade Mountains, Oregon
    • Authors: Hayley A. Corson‐Rikert; Steven M. Wondzell, Roy Haggerty, Mary V. Santelmann
      Abstract: We investigated carbon dynamics in the hyporheic zone of a steep, forested, headwater catchment western Oregon, USA. Water samples were collected monthly from the stream and a well network during baseflow periods. We examined the potential for mixing of different source waters to explain concentrations of DOC and DIC. We did not find convincing evidence that either inputs of deep groundwater or lateral inputs of shallow soil water influenced carbon dynamics. Rather, carbon dynamics appeared to be controlled by local processes in the hyporheic zone and overlying riparian soils. DOC concentrations were low in stream water (0.04 to 0.09 mM), and decreased with nominal travel time through the hyporheic zone (0.02 to 0.04 mM lost over 100 hr). Conversely, stream water DIC concentrations were much greater than DOC (0.35 to 0.7 mM) and increased with nominal travel time through the hyporheic zone (0.2 to 0.4 mM gained over 100 hr). DOC in stream water could only account for 10% of the observed increase in DIC. In‐situ metabolic processing of buried particulate organic matter as well as advection of CO2 from the vadose zone likely accounted for the remaining 90% of the increase in DIC. Overall, the hyporheic zone was a source of DIC to the stream. We suggest that, in mountain stream networks, hyporheic exchange facilitates the transformation of particulate organic carbon buried in floodplains and transports the DIC that is produced back to the stream where it can be evaded to the atmosphere. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-16T10:10:35.683823-05:
      DOI: 10.1002/2016WR019303
  • Real‐Time Estimation of Snow Water Equivalent in the Upper Colorado
           River Basin using MODIS‐based SWE Reconstructions and SNOTEL data
    • Authors: Dominik Schneider; Noah P. Molotch
      Abstract: Changes in climate necessitate improved snowpack information to better represent anomalous distributions of snow water equivalent (SWE) and improve water resource management. We estimate the spatial distribution of SWE for the Upper Colorado River basin weekly from January to June 2001‐2012 in quasi‐real‐time by two regression techniques: a baseline regression of in situ operationally measured point SWE using only physiographic information and regression of these in situ points combining both physiographic information and historical SWE patterns from a remote sensing‐based SWE reconstruction model. We compare the baseline regression approach to our new regression in the context of spatial snow surveys and operational snow measuring stations. When compared to independent distributed snow surveys, the new regression reduces the bias of SWE estimates from ‐5.5% to 0.8%, and RMSE of the SWE estimates by 8% from 0.25 m to 0.23 m. Notable improvements were observed in alpine terrain with bias declining from ‐38% to only 3.4%, and RMSE was reduced by 13%, from 0.47 m to 0.41 m. The mean increase in cross‐validated r2 for the new regression compared to the baseline regression is from 0.22 to 0.33. The largest increase in r2 in any one year is 0.19, an 83% improvement. The new regression estimates, on average, 31% greater SWE depth than the baseline regression in areas above 3000 m elevation, which contributes up to 66% of annual SWE volume in the driest year. This indicates that the historical SWE patterns from the reconstruction adds information to the interpolation beyond the physiographic conditions represented by the SNOTEL network. Given that previous works using SWE reconstructions were limited to retrospective analyses by necessity, the work presented here represents an important contribution in that it extends SWE reconstructions to real‐time applications and illustrates that doing so significantly improves the accuracy of SWE estimates. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-16T10:10:28.610859-05:
      DOI: 10.1002/2016WR019067
  • Percolation theory for solute transport in porous media: Geochemistry,
           geomorphology, and carbon cycling
    • Authors: Allen. G. Hunt; Behzad Ghanbarian
      Abstract: Understanding the time‐dependent scaling of chemical weathering has been a significant research goal for over a decade. A percolation theoretical treatment of non‐reactive solute transport that was previously shown compatible with the scaling of chemical weathering rates, is here shown to be compatible with soil formation rates, and with C and N sequestration rates in the soil as well. In this theoretical framework, the percolation backbone fractal dimensionality, which generates the long‐time tail of the solute arrival time distribution, also predicts the scaling of the reaction rates, while laboratory proportionality to the fluid flow velocity translates to an analogous relevance of the vertical infiltration rate in the field. The predicted proportionality of solute transport to net infiltration generates simultaneously the variability in soil formation rates across four orders of magnitude of precipitation and 12 orders of magnitude of time scales. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-15T08:20:39.607935-05:
      DOI: 10.1002/2016WR019289
  • The effect of losing and gaining flow conditions on hyporheic exchange in
           heterogeneous streambeds
    • Authors: A. Fox; G. Laube, C. Schmidt, J. H. Fleckenstein, S. Arnon
      Abstract: Bed form‐induced hyporheic exchange flux (qH) is increasingly viewed as a key process controlling water fluxes and biogeochemical processes in river networks. Despite the fact that streambeds are inherently heterogeneous, the majority of bed form flume scale studies were done on homogeneous systems. We conducted salt and dye tracer experiments to study the effects of losing and gaining flow conditions on qH using a laboratory recirculating flume system packed with a heterogeneous streambed, and equipped with a drainage system that enabled us to apply losing or gaining fluxes. We found that when either losing or gaining fluxes increased (regardless of whether the flux was upward or downward), qH followed an exponential decline, the volume of the hyporheic flow cell drastically reduced, and the mean residence times declined moderately. A numerical flow model for the heterogeneous streambed was set up and fitted against the experimental data in order to test whether an equivalent homogeneous case exists. The measured qH were accurately predicted with the heterogeneous model, while it was underestimated using a homogeneous model characterized by the geometric mean of the hydraulic conductivity. It was also shown that in order to produce the results of the heterogeneous model with an equivalent hydraulic conductivity, the latter had to be increased as the losing or gaining fluxes increase. The results strongly suggest that it is critical to adequately account for the heterogeneous streambed structure in order to accurately predict the effect of vertical exchange fluxes between the stream and groundwater on hyporheic exchange. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-15T08:20:38.312487-05:
      DOI: 10.1002/2016WR018677
  • Sharing the cost of a river basin adaptation portfolios to climate change:
           Insights from social justice and cooperative game theory
    • Authors: Corentin Girard; Jean‐Daniel Rinaudo, Manuel pulido‐velazquez
      Abstract: The adaptation of water resource systems to the potential impacts of climate change requires mixed portfolios of supply and demand adaptation measures. The issue is not only to select efficient, robust and flexible adaptation portfolios but also to find equitable strategies of cost allocation among the stakeholders. Our work addresses such cost allocation problems by applying two different theoretical approaches: social justice and cooperative game theory in a real case study. First of all, a cost‐effective portfolio of adaptation measures at the basin scale is selected using a least‐cost optimization model. Cost allocation solutions are then defined based on economic rationality concepts from cooperative game theory (the Core). Secondly, interviews are conducted to characterize stakeholders' perceptions of social justice principles associated with the definition of alternatives cost allocation rules. The comparison of the cost allocation scenarios leads to contrasted insights in order to inform the decision making process at the river basin scale and potentially reap the efficiency gains from cooperation in the design of river basin adaptation portfolios. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-15T08:20:37.02322-05:0
      DOI: 10.1002/2016WR018757
  • Sequential ensemble‐based optimal design for parameter estimation
    • Authors: Jun Man; Jiangjiang Zhang, Weixuan Li, Lingzao Zeng, Laosheng Wu
      Abstract: The ensemble Kalman filter (EnKF) has been widely used in parameter estimation for hydrological models. The focus of most previous studies was to develop more efficient analysis (estimation) algorithms. On the other hand, it is intuitively understandable that a well‐designed sampling (data‐collection) strategy should provide more informative measurements and subsequently improve the parameter estimation. In this work, a Sequential Ensemble‐based Optimal Design (SEOD) method, coupled with EnKF, information theory and sequential optimal design, is proposed to improve the performance of parameter estimation. Based on the first‐ and second‐order statistics, different information metrics including the Shannon entropy difference (SD), degrees of freedom for signal (DFS) and relative entropy (RE) are used to design the optimal sampling strategy, respectively. The effectiveness of the proposed method is illustrated by synthetic one‐ and two‐dimensional unsaturated flow case studies. It is shown that the designed sampling strategies can provide more accurate parameter estimation and state prediction compared with conventional sampling strategies. Optimal sampling designs based on various information metrics perform similarly in our cases. The effect of ensemble size on the optimal design is also investigated. Overall, larger ensemble size improves the parameter estimation and convergence of optimal sampling strategy. Although the proposed method is applied to unsaturated flow problems in this study, it can be equally applied in any other hydrological problems. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-15T08:20:30.846668-05:
      DOI: 10.1002/2016WR018736
  • Cooperative drought adaptation: Integrating infrastructure development,
           conservation, and water transfers into adaptive policy pathways
    • Authors: Harrison B. Zeff; Jonathan D. Herman, Patrick M. Reed, Gregory W. Characklis
      Abstract: A considerable fraction of urban water supply capacity serves primarily as a hedge against drought. Water utilities can reduce their dependence on firm capacity and forestall the development of new supplies using short‐term drought management actions, such as conservation and transfers. Nevertheless, new supplies will often be needed, especially as demands rise due to population growth and economic development. Planning decisions regarding when and how to integrate new supply projects are fundamentally shaped by the way in which short‐term adaptive drought management strategies are employed. To date, the challenges posed by long‐term infrastructure sequencing and adaptive short‐term drought management are treated independently, neglecting important feedbacks between planning and management actions. This work contributes a risk‐based framework that uses continuously updating risk‐of‐failure (ROF) triggers to capture the feedbacks between short term drought management actions (e.g., conservation and water transfers) and the selection and sequencing of a set of regional supply infrastructure options over the long term. Probabilistic regional water supply pathways are discovered for four water utilities in the ‘Research Triangle' region of North Carolina. Furthermore, this study distinguishes the status‐quo planning path of independent action (encompassing utility‐specific conservation and new supply infrastructure only) from two cooperative formulations: ‘weak' cooperation, which combines utility‐specific conservation and infrastructure development with regional transfers, and ‘strong' cooperation, which also includes jointly developed regional infrastructure to support transfers. Results suggest that strong cooperation aids utilities in meeting their individual objectives at substantially lower costs and with less overall development. These benefits demonstrate how an adaptive, rule‐based decision framework can coordinate integrated solutions that would not be identified using more traditional optimization methods. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-12T10:20:36.330362-05:
      DOI: 10.1002/2016WR018771
  • Quantifying and reducing leakage errors in the JPL RL05M GRACE Mascon
    • Authors: David N. Wiese; Felix W. Landerer, Michael M. Watkins
      Abstract: Recent advances in processing data from the Gravity Recovery and Climate Experiment (GRACE) have led to a new generation of gravity solutions constrained within a Bayesian framework to remove correlated errors rather than relying on empirical filters. The JPL RL05M mascon solution is one such solution, solving for mass variations using spherical cap mass concentration elements (mascons), while relying on external information provided by near‐global geophysical models to constrain the solution. This new gravity solution is fundamentally different than the traditional spherical harmonic gravity solution, and as such, requires different care when postprocessing. Here, we discuss two classes of postprocessing considerations for the JPL RL05M GRACE mascon solution: (1) reducing leakage errors across land/ocean boundaries, and (2) scaling the solutions to account for leakage errors introduced through parameterizing the gravity solution in terms of mascons. A Coastline Resolution Improvement (CRI) filter is developed to reduce leakage errors across coastlines. Synthetic simulations reveal a reduction in leakage errors of ∼50%, such that residual leakage errors are ∼1 cm equivalent water height (EWH) averaged globally. A set of gain factors is derived to reduce leakage errors for continental hydrology applications. The combined effect of the CRI filter coupled with application of the gain factors, is shown to reduce leakage errors when determining the mass balance of large (>160,000 km2) hydrological basins from 11% ‐ 30% (0.6‐1.5 mm EWH) averaged globally, with local improvements up to 8% ‐ 81% (9‐19 mm EWH). This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-12T04:30:52.743486-05:
      DOI: 10.1002/2016WR019344
  • On the turbulent flow structure around an instream structure with
           realistic geometry
    • Authors: Seokkoo Kang; Craig Hill, Fotis Sotiropoulos
      Abstract: We investigate the flow dynamics around a rock vane, a widely‐used instream structure for stream restoration, by conducting laboratory flume experiments, and carrying out high‐resolution Large Eddy Simulation (LES) taking advantage of parallel computing. The flume experiments are conducted under fixed‐ and mobile‐bed conditions, where the velocities and bed elevations are measured, respectively. The LES is carried out for the fixed‐bed experiment by directly resolving the details of the rocks that constitute the vane and the individual roughness elements on the channel bed. The LES‐computed mean flow statistics show good agreement with the measurements, and the analysis of the computed flow field reveals the existence of two counter‐rotating secondary flow cells downstream of the vane, which originate from the plunging of the three‐dimensional streamlines onto a lower part of the sidewall downstream of the vane. To further examine the role of the secondary flow cells under a mobile‐bed condition, the LES results are compared with the equilibrium bed elevation measured in the mobile bed experiment. The mobile‐bed experiment reveals the existence of an oblique sand ridge downstream of the vane that is aligned with the line of flow convergence caused by the collision of the two secondary flow cells. The results indicate that the two counter‐rotating cells downstream of the rock vane has a profound impact on the mean flow and bed shear stress as well as on the bed morphodynamics. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-10T10:00:31.873447-05:
      DOI: 10.1002/2016WR018688
  • Inverse Modeling of Unsaturated Flow Using Clusters of Soil Texture and
           Pedotransfer Functions
    • Authors: Yonggen Zhang; Marcel G. Schaap, Alberto Guadagnini, Shlomo P. Neuman
      Abstract: Characterization of heterogeneous soil hydraulic parameters of deep vadose zones is often difficult and expensive, making it necessary to rely on other sources of information. Pedotransfer functions (PTFs) based on soil texture data constitute a simple alternative to inverse hydraulic parameter estimation, but their accuracy is often modest. Inverse modeling entails a compromise between detailed description of subsurface heterogeneity and the need to restrict the number of parameters. We propose two methods of parameterizing vadose zone hydraulic properties using a combination of k‐means clustering of kriged soil texture data, PTFs and model inversion. One approach entails homogeneous and the other heterogeneous clusters. Clusters may include subdomains of the computational grid that need not be contiguous in space. The first approach homogenizes within‐cluster variability into initial hydraulic parameter estimates that are subsequently optimized by inversion. The second approach maintains heterogeneity through multiplication of each spatially varying initial hydraulic parameter by a scale factor, estimated a posteriori through inversion. This allows preserving heterogeneity without introducing a large number of adjustable parameters. We use each approach to simulate a 95‐day infiltration experiment in unsaturated layered sediments at a semiarid site near Phoenix, Arizona, over an area of 50 × 50 m2 down to a depth of 14.5 m. Results show that both clustering approaches improve simulated moisture contents considerably in comparison to those based solely on PTF estimates. Our calibrated models are validated against data from a subsequent 295‐day infiltration experiment at the site. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-10T10:00:25.110705-05:
      DOI: 10.1002/2016WR019016
  • The Henry problem: New semi‐analytical solution for
           velocity‐dependent dispersion
    • Authors: Marwan Fahs; Behzad Ataie‐Ashtiani, Anis Younes, Craig T. Simmons, Philippe Ackerer
      Abstract: A new semi‐analytical solution is developed for the velocity‐dependent dispersion Henry problem using the Fourier‐Galerkin method (FG). The integral arising from the velocity‐dependent dispersion term is evaluated numerically using an accurate technique based on an adaptive scheme. Numerical integration and nonlinear dependence of the dispersion on the velocity render the semi‐analytical solution impractical. To alleviate this issue, and to obtain the solution at affordable computational cost, a robust implementation for solving the nonlinear system arising from the FG method is developed. It allows for reducing the number of attempts of the iterative procedure and the computational cost by iteration. The accuracy of the semi‐analytical solution is assessed in terms of the truncation orders of the Fourier series. An appropriate algorithm based on the sensitivity of the solution to the number of Fourier modes is used to obtain the required truncation levels. The resulting Fourier series are used to analytically evaluate the position of the principal isochlors and metrics characterizing the saltwater wedge. They are also used to calculate longitudinal and transverse dispersive fluxes and to provide physical insight into the dispersion mechanisms within the mixing zone. The developed semi‐analytical solutions are compared against numerical solutions obtained using an in house code based on variant techniques for both space and time discretization. The comparison provides better confidence on the accuracy of both numerical and semi‐analytical results. It shows that the new solutions are highly sensitive to the approximation techniques used in the numerical code which highlights their benefits for code benchmarking. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-10T10:00:22.296813-05:
      DOI: 10.1002/2016WR019288
  • Disaster Loss and Social Media: Can Online Information Increase Flood
    • Authors: Maura C. Allaire
      Abstract: When confronted with natural disasters, individuals around the world increasingly use online resources to become informed of forecasted conditions and advisable actions. This study tests the effectiveness of online information and social media in enabling households to reduce disaster losses. The 2011 Bangkok flood is utilized as a case study since it was one of the first major disasters to affect a substantial population connected to social media. The role of online information is investigated with a mixed methods approach. Both quantitative (propensity score matching) and qualitative (in‐depth interviews) techniques are employed. The study relies on two data sources – survey responses from 469 Bangkok households and in‐depth interviews with twenty‐three internet users who are a subset of the survey participants.Propensity score matching indicates that social media enabled households to reduce flood losses by an average of 37% (USD 3,708 per household), using a nearest neighbor estimator. This reduction is substantial when considering that household flood losses for the matched sample averaged USD 8,278. Social media offered information not available from other sources, such as localized and nearly real‐time updates of flood location and depth. With this knowledge, households could move belongings to higher ground before floodwaters arrived. These findings suggest that utilizing social media users as sensors could better inform populations during disasters. Overall, the study reveals that online information can enable effective disaster preparedness and reduce losses. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-09T10:16:59.956136-05:
      DOI: 10.1002/2016WR019243
  • A numerical model for water and heat transport in freezing soils with
           non‐equilibrium ice‐water interfaces
    • Authors: Zhenyang Peng; Fuqiang Tian, Jingwei Wu, Jiesheng Huang, Hongchang Hu, Christophe Darnault
      Abstract: A one‐dimensional numerical model of heat and water transport in freezing soils is developed by assuming that ice‐water interfaces are not necessarily in equilibrium. The Clapeyron equation, which is derived from a static ice‐water interface using the thermal equilibrium theory, cannot be readily applied to a dynamic system, such as freezing soils. Therefore, we handled the redistribution of liquid water with the Richard's equation. In this application, the sink term is replaced by the freezing rate of pore water, which is proportional to the extent of super‐cooling and available water content for freezing by a coefficient, β. Three short‐term laboratory column simulations show reasonable agreement with observations, with standard error of simulation on water content ranging between 0.007 cm3cm−3 and 0.011 cm3cm−3, showing improved accuracy over other models that assume equilibrium ice‐water interfaces. Simulation results suggest that when the freezing front is fixed at a specific depth, deviation of the ice‐water interface from equilibrium, at this location, will increase with time. However, this deviation tends to weaken when the freezing front slowly penetrates to a greater depth, accompanied with thinner soils of significant deviation. The coefficient, β, plays an important role in the simulation of heat and water transport. A smaller β results in a larger deviation in the ice‐water interface from equilibrium, and backward estimation of the freezing front. It also leads to an underestimation of water content in soils that were previously frozen by a rapid freezing rate, and an overestimation of water content in the rest of the soils. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-09T10:15:56.931833-05:
      DOI: 10.1002/2016WR019116
  • Time‐lapse gravity data for monitoring and modeling artificial recharge
           through a thick unsaturated zone
    • Authors: Jeffrey R. Kennedy; Ty P.A. Ferré, Benjamin Creutzfeldt
      Abstract: Groundwater‐level measurements in monitoring wells or piezometers are the most common, and often the only, hydrologic measurements made at artificial recharge facilities. Measurements of gravity change over time provide an additional source of information about changes in groundwater storage, infiltration, and for model calibration. We demonstrate that for an artificial recharge facility with a deep groundwater table, gravity data are more sensitive to movement of water through the unsaturated zone than are groundwater levels. Groundwater levels have a delayed response to infiltration, change in a similar manner at many potential monitoring locations, and are heavily influenced by high‐frequency noise induced by pumping; in contrast, gravity changes start immediately at the onset of infiltration and are sensitive to water in the unsaturated zone. Continuous gravity data can determine infiltration rate, and the estimate is only minimally affected by uncertainty in water‐content change. Gravity data are also useful for constraining parameters in a coupled groundwater‐unsaturated zone model [Modflow‐NWT model with the Unsaturated Zone Flow (UZF) package]. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-08T09:40:23.140839-05:
      DOI: 10.1002/2016WR018770
  • Direct prediction of spatially and temporally varying physical properties
           from time‐lapse electrical resistance data
    • Authors: Hermans Thomas; Oware Erasmus, Caers Jef
      Abstract: Time‐lapse applications of electrical methods have grown significantly over the last decade. However, the quantitative interpretation of tomograms in terms of physical properties, such as salinity, temperature or saturation, remains difficult. In many applications, geophysical models are transformed into hydrological models, but this transformation suffers from spatially and temporally varying resolution resulting from the regularization used by the deterministic inversion. In this study, we investigate a prediction‐focused approach (PFA) to directly estimate subsurface physical properties with electrical resistance data, circumventing the need for classic tomographic inversions. First, we generate a prior set of resistance data and physical property forecast through hydrogeological and geophysical simulations mimicking the field experiment. We reduce the dimension of both the data and the forecast through principal component analysis in order to keep the most informative part of both sets in a reduced dimension space. Then, we apply canonical correlation analysis to explore the relationship between the data and the forecast in their reduced dimension space. If a linear relationship can be established, the posterior distribution of the forecast can be directly sampled using a Gaussian process regression where the field data scores are the conditioning data. In this paper, we demonstrate PFA for various physical property distributions. We also develop a framework to propagate the estimated noise level in the reduced dimension space. We validate the results by a Monte Carlo study on the posterior distribution and demonstrate that PFA yields accurate uncertainty for the cases studied. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-08T04:15:23.659218-05:
      DOI: 10.1002/2016WR019126
  • Yosemite hydroclimate network: Distributed stream and atmospheric data for
           the Tuolumne River watershed and surroundings
    • Authors: Jessica D. Lundquist; James W. Roche, Harrison Forrester, Courtney Moore, Eric Keenan, Gwyneth Perry, Nicoleta Cristea, Brian Henn, Karl Lapo, Bruce McGurk, Daniel R. Cayan, Michael D. Dettinger
      Abstract: Regions of complex topography and remote wilderness terrain have spatially‐varying patterns of temperature and streamflow, but due to inherent difficulties of access, are often very poorly sampled. Here we present a dataset of distributed stream stage, streamflow, stream temperature, barometric pressure, and air temperature from the Tuolumne River Watershed in Yosemite National Park, Sierra Nevada, California, U.S.A. for water years 2002 to 2015, as well as a quality‐controlled hourly meteorological forcing time series for use in hydrologic modeling. We also provide snow data and daily inflow to the Hetch Hetchy Reservoir for 1970 to 2015. This paper describes data collected using low‐visibility and low‐impact installations for wilderness locations and can be used alone or as a critical supplement to ancillary datasets collected by cooperating agencies, referenced herein. This dataset provides a unique opportunity to understand spatial patterns and scaling of hydroclimatic processes in complex terrain and can be used to evaluate downscaling techniques or distributed modeling. The paper also provides an example methodology and lessons learned in conducting hydroclimatic monitoring in remote wilderness. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-06T10:45:27.802899-05:
      DOI: 10.1002/2016WR019261
  • Comment on “Climate and agricultural land use change impacts on
           streamflow in the upper midwestern United States” by Satish C. Gupta et
    • Authors: Efi Foufoula‐Georgiou; Patrick Belmont, Peter Wilcock, Karen Gran, Jacques C. Finlay, Praveen Kumar, Jonathan A. Czuba, Jon Schwenk, Zeinab Takbiri
      Abstract: This comment cautions against dismissing agricultural practices as a significant cause of hydrologic change in Midwestern agricultural landscapes. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-06T04:16:35.0909-05:00
      DOI: 10.1002/2015WR018494
  • Reply to comments on ‘Climate and agricultural land use change impacts
           on streamflow in the upper Midwestern United States’ by
           Foufoula‐Georgiou et al.
    • Authors: Satish C. Gupta; Andrew C. Kessler, Melinda K. Brown, William M. Schuh
      Abstract: This reply addresses concerns raised by Foufoula‐Georgiou et al. [2016] on Gupta et al. [2015] through additional regression analysis of streamflow and base flow and with description of the water quality conditions in the Minnesota River prior to European settlements in 1850s. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-06T04:16:30.666243-05:
      DOI: 10.1002/2016WR019003
  • Pore‐space structure and average dissolution rates: A simulation
    • Authors: J. P. Pereira Nunes; B. Bijeljic, M. J. Blunt
      Abstract: We study the influence of the pore‐space geometry on sample‐averaged dissolution rates in millimetre‐scale carbonate samples undergoing reaction‐controlled mineral dissolution upon the injection of a CO_2 saturated brine. The representation of the pore‐space is obtained directly from micro‐CT images with a resolution of a few microns. Simulations are performed with a particle tracking approach on images of three porous rocks of increasing pore‐space complexity: a beadpack, a Ketton oolite and an Estaillades limestone.Reactive transport is simulated with a hybrid approach that combines a Lagrangian method for transport and reaction with the Eulerian flow field obtained by solving the incompressible Navier‐Stokes equations directly on the voxels of three‐dimensional images. Particle advection is performed with a semi‐analytical streamline method and diffusion is simulated via a random walk. Mineral dissolution is defined in terms of the particle flux through the pore‐solid interface, which can be related analytically to the batch (intrinsic) reaction rate.The impact of the flow heterogeneity on reactive transport is illustrated in a series of simulations performed at different flow rates. The average dissolution rates depend on both the heterogeneity of the sample and on the flow rate. The most heterogeneous rock may exhibit a decrease of up to two orders of magnitude in the sample‐averaged reaction rates in comparison with the batch rate. Furthermore, we provide new insights for the dissolution regime that would be traditionally characterised as uniform. In most cases, at the pore scale, dissolution preferentially enlarges fast‐flow channels which greatly restricts the effective surface available for reaction. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-06T04:16:29.633969-05:
      DOI: 10.1002/2016WR019313
  • A novel method to estimate the maximization ratio of the Probable Maximum
           Precipitation (PMP) using regional climate model output
    • Authors: Hassan Rouhani; Robert Leconte
      Abstract: The moisture maximization approach to estimate the Probable Maximum Precipitation (PMP) has a simple technique for controlling the risk of overestimating PMP: the maximization ratio is limited by an upper bound. The upper bound limit depends on storm records and watershed characteristics. However, it is not readily available in many watersheds. A robust scientific justification for limiting the maximization ratio is missing. In this paper, a novel approach is proposed to estimate the maximization ratio which does not impose an upper limit to the ratio. The new approach, which uses regional climate model data, is based on constructing annual maximum precipitable water time series with precipitable water values for which atmospheric variables are similar to the original event to be maximized. These time series are then used to estimate the 100‐year return period precipitable water value required to calculate the maximization ratio. The new approach was tested in three watersheds in the province of Québec, Canada. Results showed that maximization ratio values were lower than the proposed upper bound value for these watersheds. In comparison to the approach using an upper bound, this proposed approach reduced PMP in these watersheds by 11%. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-06T04:16:26.12581-05:0
      DOI: 10.1002/2016WR018603
  • Tree population dynamics on a floodplain: A tradeoff between tree
           mortality and seedling recruitment induced by stochastic floods
    • Authors: Hitoshi Miyamoto; Ryo Kimura
      Abstract: This paper proposes a stochastic evaluation method for examining tree population states in a river cross section using an integrated model with Monte Carlo simulation. The integrated model consists of four processes as sub‐models, i.e., tree population dynamics, flow discharge stochasticity, stream hydraulics, and channel geomorphology. A floodplain of the Kako River in Japan was examined as a test site, which is currently well vegetated and features many willows that have been growing in both individual size and overall population over the last several decades. The model was used to stochastically evaluate the effects of hydrologic and geomorphologic changes on tree population dynamics through the Monte Carlo simulation. The effects including the magnitude of flood impacts and the relative change in the floodplain level are examined using very simple scenarios for flow regulation, climate change, and channel form changes. The stochastic evaluation method revealed a tradeoff point in floodplain levels, at which the tendency of a fully vegetated state switches to that of a bare floodplain under small impacts of flood. It is concluded from these results that the states of tree population in a floodplain can be determined by the mutual interactions among flood impacts, seedling recruitment, tree growth, and channel geomorphology. These interactions make it difficult to obtain a basic understanding of tree population dynamics from a field study of a specific floodplain. The stochastic approach used in this paper could constitute an effective method for evaluating fundamental channel characteristics for a vegetated floodplain. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-06T04:16:22.804483-05:
      DOI: 10.1002/2015WR018528
  • Precipitation estimation using L‐Band and C‐band soil moisture
    • Authors: Randal D. Koster; Luca Brocca, Wade T. Crow, Mariko S. Burgin, Gabrielle J. M. De Lannoy
      Abstract: An established methodology for estimating precipitation amounts from satellite‐based soil moisture retrievals is applied to L‐band products from the Soil Moisture Active Passive (SMAP) and Soil Moisture and Ocean Salinity (SMOS) satellite missions and to a C‐band product from the Advanced Scatterometer (ASCAT) mission. The precipitation estimates so obtained are evaluated against in situ (gauge‐based) precipitation observations from across the globe. The precipitation estimation skill achieved using the L‐band SMAP and SMOS datasets is higher than that obtained with the C‐band product, as might be expected given that L‐band is sensitive to a thicker layer of soil and thereby provides more information on the response of soil moisture to precipitation. The square of the correlation coefficient between the SMAP‐based precipitation estimates and the observations (for aggregations to ∼100 km and 5 days) is on average about 0.6 in areas of high rain gauge density. Satellite missions specifically designed to monitor soil moisture thus do provide significant information on precipitation variability, information that could contribute to efforts in global precipitation estimation. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-06T04:16:20.411826-05:
      DOI: 10.1002/2016WR019024
  • Mapping daily and seasonal evapotranspiration from irrigated crops using
           global climate grids and satellite imagery: Automation and methods
    • Authors: Trent W. Biggs; Michael Marshall, Alex Messina
      Abstract: The surface energy balance algorithm for land (SEBAL) estimates land surface evapotranspiration (ET) from radiometric surface temperature (TR), but requires manual selection of calibration pixels, which can be impractical for mapping seasonal ET. Here, pixel selection is automated and SEBAL implemented using global climate grids and satellite imagery. SEBAL is compared with the MOD16 algorithm, which uses remotely sensed data on vegetation condition to constrain reference ET from the Penman‐Monteith equation. The difference between the evaporative fraction (Λ, range 0‐1) from SEBAL and six eddy flux correlation towers was less than 0.10 for three of six towers, and less than 0.24 for all towers. SEBAL ET was moderately sensitive to surface roughness length and implementation over regions smaller than ∼10,000 km2 provided lower error than larger regions. Pixel selection based on TR had similar errors as those based on a vegetation index. For maize, MOD16 had lower error in mean seasonal evaporative fraction (‐0.02) compared to SEBAL Λ (0.23), but MOD16 significantly underestimated the evaporative fraction from rice (‐0.52) and cotton fields (‐0.67) compared with SEBAL (‐0.09 rice, ‐0.09 cotton). MOD16 had the largest error over short crops in the early growing season when vegetation cover was low but land surface was wet. Temperature‐based methods like SEBAL can be automated and likely outperform vegetation‐based methods in irrigated areas, especially under conditions of low vegetation cover and high soil evaporation. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-06T04:15:30.698639-05:
      DOI: 10.1002/2016WR019107
  • Transient forcing effects on mixing of two fluids for a stable
    • Authors: María Pool; Marco Dentz, Vincent E.A. Post
      Abstract: Mixing and dispersion in coastal aquifers are strongly influenced by periodic temporal flow fluctuations on multiple time‐scales ranging from days (tides), seasons (pumping and recharge) to glacial cycles (regression and transgressions). Transient forcing effects lead to a complex space‐ ant time‐dependent flow response which induces enhanced spreading and mixing of dissolved substances. We study effective mixing and solute transport in temporally fluctuating one‐dimensional flow for a stable stratification of two fluids of different density using detailed numerical simulation as well as accurate column experiments. We quantify the observed transport behaviors and interface evolution by a time‐averaged model that is obtained from a two‐scale expansion of the full transport problem, and derive explicit expressions for the center of mass and width of the mixing zone between the two fluids. We find that the magnitude of transient‐driven mixing is mainly controlled by the hydraulic diffusivity, the period and the initial interface location. At an initial time regime, mixing can be characterized by an effective dispersion coefficient and both the interface position and width evolve linearly in time. At larger times, the spatial variability of the flow velocity leads to a deceleration of the interface and a compression of its width, which is manifested by a subdiffusive evolution of its width as t1/2. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-02T10:35:30.496949-05:
      DOI: 10.1002/2016WR019181
  • Seasonal variations of halite saturation in the Dead Sea
    • Authors: Ido Sirota; Ali Arnon, Nadav Lensky
      Abstract: Hypersaline lakes and seas were common in the past, precipitating thick evaporitic salt deposits. The only modern analogue for the paleo‐limnology of deep salt‐saturated aquatic environments exists in the Dead Sea. In this study we present new insights from the Dead Sea on the role of seasonal thermohaline stratification and water balance on the seasonal and depth variations of the degree of saturation of halite (salt) and the rate of halite growth along the water column. We developed methodologies to accurately determine the empirical degree of halite saturation of the lake based on high accuracy densitometry, and to quantify halite growth rate along the water column. During summer, the epilimnion is undersaturated and halite is dissolved, whereas during winter the entire water column is supersaturated and crystallizes halite. This result is not trivial because the variations in the water balance suggest the opposite; summer is associated with higher loss of water by evaporation from the lake compared to the winter. Hence, the thermal effect overcomes the hydrological balance effect and thus governs the seasonal saturation cycle. The hypolimnion is supersaturated with respect to halite and crystallizes throughout the year, with higher super saturation and higher crystallization rates during winter. During summer, simultaneous opposing environments coexist – an under‐saturated epilimnion that dissolves halite and a supersaturated hypolimnion that crystallizes halite, which results in focusing of halite deposits in the deep hypolimnetic parts of the evaporitic basins and thinning the shallow epilimnetic deposits. This article is protected by copyright. All rights reserved.
      PubDate: 2016-09-01T04:15:36.413936-05:
      DOI: 10.1002/2016WR018974
  • A new method to partition climate and catchment effect on the mean annual
           runoff based on the Budyko complementary relationship
    • Authors: Sha Zhou; Bofu Yu, Lu Zhang, Yuefei Huang, Ming Pan, Guangqian Wang
      Abstract: Effect of climate change and catchment change on the long‐term water balance is of considerable interest at a range of spatial scales. The total differential of runoff within the Budyko framework, which has been widely used to attribute the change in runoff to the effect of climate and catchment changes, is not precise in that there is always some residual between the observed and estimated change in runoff. The objective of this study is to propose and evaluate a new partition method based on the Budyko complementary relationship for runoff. Algebraic identities have ensured that the change in runoff can be decomposed into two components precisely without any residuals using this complementary method. In addition, the complementary method allows estimation of the upper and lower bounds of the climate effect and catchment effect. The new method was compared with the total differential method and an extrapolation method for 15 catchments in Australia. Results show that the average range of the catchment effect using the complementary method was 6.7 mm for 14 of the 15 catchments, which is much smaller than that estimated with the total differential method (51.5mm). The average of the upper and lower bounds was shown to be in good agreement with the effect of climate and catchment changes estimated using the extrapolation method (R2 = 0.98 for both). Correlation analysis indicates that the average of these bounds is the best estimate of the magnitude of the climate and catchment effect for the 15 catchments examined. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-29T04:05:38.464449-05:
      DOI: 10.1002/2016WR019046
  • Analytical and numerical investigations of spontaneous imbibition in
           porous media
    • Authors: Hasan A. Nooruddin; Martin J. Blunt
      Abstract: We present semi‐analytical solutions for co‐current displacements with some degree of counter‐current flow. The solution assumes a one‐dimensional horizontal displacement of two immiscible incompressible fluids with arbitrary viscosities and saturation‐dependent relative permeability and capillary pressures. We address the impact of the system length on the degree of counter‐current flow when there is no pressure drop in the non‐wetting phase across the system, assuming negligible capillary back pressure at the inlet boundary of the system. It is shown that in such displacements, the fractional flow can be used to determine a critical water saturation, from which regions of both co‐current and counter‐current flow are identified. This critical saturation changes with time as the saturation front moves into the porous medium. Furthermore, the saturation profile in the approach presented here is not necessarily a function of distance divided by the square root of time. We also present approximate solutions using a perturbative approach, which is valid for a wide range of flow conditions. This approach requires less computational power and is much easier to implement than the implicit integral solutions used in previous work. Finally, a comprehensive comparison between analytical and numerical solutions is presented. Numerical computations are performed using traditional finite‐difference formulations and convergence analysis shows a generally slow convergence rate for water imbibition rates and saturation profiles. This suggests that most coarsely‐gridded simulations give a poor estimate of imbibition rates, while demonstrating the value of these analytical solutions as benchmarks for numerical studies, complementing Buckley‐Leverett analysis. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-25T05:10:40.510083-05:
      DOI: 10.1002/2015WR018451
  • Isoscapes of δ18O and δ2H reveal climatic forcings on Alaska and
           Yukon precipitation
    • Authors: Matthew S. Lachniet; Daniel E. Lawson, Haroon Stephen, Alison R. Sloat, William P. Patterson
      Abstract: Spatially‐extensive Arctic stable isotope data are sparse, inhibiting the climatic understanding required to interpret paleoclimate proxy records. To fill this need, we constrained the climatic and physiographic controls on δ18O and δD values of stream waters across Alaska and the Yukon to derive interpolated isoscape maps. δ18O is strongly correlated to winter temperature parameters and similarity of the surface water line (δ2H = 8.0 × δ18O + 6.4) to the Global Meteoric Water Line suggests stream waters are a proxy for meteoric precipitation. We observe extreme orographic δ18O decreases and a trans‐Alaskan continental gradient of ‐8.3 ‰ 1000 km−1. Continental gradients are high in coastal zones and low in the interior. Localized δ18O increases indicate inland air mass penetration via topographic lows. Using observed δ18O/temperature gradients, we show that δ18O decreases in a ∼24 ka permafrost ice wedge relative to the late Holocene indicate mean annual and coldest quarter temperature reductions of 8.9 ± 1.7°C and 17.2 ± 3.2°C, respectively. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-16T12:15:32.471323-05:
      DOI: 10.1002/2016WR019436
  • 3D Dense distributed temperature sensing for measuring layered
           thermohaline systems
    • Authors: K.P. Hilgersom; N.C. van de Giesen, P.G.B. de Louw, M. Zijlema
      Abstract: Distributed temperature sensing has proven a useful technique for geoscientists to obtain spatially distributed temperature data. When studies require high‐resolution temperature data in three spatial dimensions, current practices to enhance the spatial resolution do not suffice. For example, double‐diffusive phenomena induce sharp and small‐scale temperature patterns in water bodies subject to thermohaline gradients. This article presents a novel approach for a 3D dense distributed temperature sensing setup, the design of which can be customized to the required spatial resolution in each dimension. Temperature is measured along fiber‐optic cables that can be arranged as needed. In this case, we built a dense cage of very thin (1.6 mm) cables to ensure that interference with flow patterns was minimal. Application in water bodies with double‐diffusion induced sharp temperature gradients shows that the setup is well able to capture small‐scale temperature patterns and even detects small unsuspected seeps and potential salt‐fingers. However, the potential effect of the setup on the flow patterns requires further study. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-16T12:01:37.75714-05:0
      DOI: 10.1002/2016WR019119
  • Joint identification of contaminant source location, initial release time
           and initial solute concentration in an aquifer via ensemble Kalman
    • Authors: Teng Xu; J. Jaime Gómez‐Hernández
      Abstract: When a contaminant is detected in a drinking well, source location, initial contaminant release time and initial contaminant concentration are, in many cases, unknown; the responsible party may have disappeared and the identification of when and where the contamination happened may become difficult. Although contaminant source identification has been studied extensively in the last decades, we propose —to our knowledge, for the first time— the use of the ensemble Kalman filter (EnKF), which has proven to be a powerful algorithm for inverse modeling. The EnKF is tested in a two‐dimensional synthetic deterministic aquifer, identifying, satisfactorily, the source location, the release time, and the release concentration, together with an assessment of the uncertainty associated with this identification. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-16T12:00:22.506412-05:
      DOI: 10.1002/2016WR019111
  • An analytical solution of Richards' equation providing the physical basis
           of SCS curve number method and its proportionality relationship
    • Authors: Milad Hooshyar; Dingbao Wang
      Abstract: The empirical proportionality relationship, which indicates that the ratio of cumulative surface runoff and infiltration to their corresponding potentials are equal, is the basis of the extensively used Soil Conservation Service Curve Number (SCS‐CN) method. The objective of this paper is to provide the physical basis of the SCS‐CN method and its proportionality hypothesis from the infiltration excess runoff generation perspective. To achieve this purpose, an analytical solution of Richards' equation is derived for ponded infiltration in shallow water table environment under the following boundary conditions: 1) the soil is saturated at the land surface; and 2) there is a no‐flux boundary which moves downward. The solution is established based on the assumptions of negligible gravitational effect, constant soil water diffusivity, and hydrostatic soil moisture profile between the no‐flux boundary and water table. Based on the derived analytical solution, the proportionality hypothesis is a reasonable approximation for rainfall partitioning at the early stage of ponded infiltration in areas with a shallow water table for coarse textured soils. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-16T11:40:38.917713-05:
      DOI: 10.1002/2016WR018885
  • Landscape controls on spatiotemporal discharge variability in a boreal
    • Authors: R.H. Karlsen; T. Grabs, K. Bishop, I. Buffam, H. Laudon, J. Seibert
      Abstract: Improving the understanding of how stream flow dynamics are influenced by landscape characteristics, such as soils, vegetation and terrain, is a central endeavor of catchment hydrology. Here we investigate how spatial variability in stream flow is related to landscape characteristics using specific discharge time series from 14 partly nested sub‐catchments in the Krycklan basin (0.12 – 68 km2). Multivariate principal component analyses combined with univariate analyses showed that while variability in landscape characteristics and specific discharge were strongly related, the spatial patterns varied with season and wetness conditions. During spring snowmelt and at the annual scale, specific discharge was positively related to the sum of wetland and lake area. During summer, when flows are lowest, specific discharge was negatively related to catchment tree volume, but positively related to deeper sediment deposits and catchment area. The results indicate how more densely forested areas on till soils become relatively drier during summer months, while wet areas and deeper sediment soils maintain a higher summer baseflow. Annual and seasonal differences in specific discharge can therefore be explained to a large extent by expected variability in evapotranspiration fluxes and snow accumulation. These analyses provide an organizing principle for how specific discharge varies spatially across the boreal landscape, and how this variation is manifested for different wetness conditions, seasons and time scales. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-16T11:40:37.900402-05:
      DOI: 10.1002/2016WR019186
  • Capillary pressure‐saturation relations in quartz and carbonate sands:
           Limitations for correlating capillary and wettability influences on air,
           oil, and supercritical CO2 trapping
    • Authors: Shibo Wang; Tetsu K. Tokunaga, Jiamin Wan, Wenming Dong, Yongman Kim
      Abstract: Capillary pressure (Pc) – saturation (Sw) relations are essential for predicting equilibrium and flow of immiscible fluid pairs in soils and deeper geologic formations. In systems that are difficult to measure, behavior is often estimated based on capillary scaling of easily measured Pc–Sw relations (e.g., air‐water, and oil‐water), yet the reliability of such approximations needs to be examined. In this study, seventeen sets of brine drainage and imbibition curves were measured with air‐brine, decane‐brine, and supercritical (sc) CO2‐brine in homogeneous quartz and carbonate sands, using porous plate systems under ambient (0.1 MPa, 23 ˚C) and reservoir (12.0 MPa, 45 ˚C) conditions. Comparisons between these measurements showed significant differences in residual nonwetting phase saturation, Snw,r. Through applying capillary scaling, changes in interfacial properties were indicated, particularly wettability. With respect to the residual trapping of the nonwetting phases, Snwr, CO2 > Snwr, decane > Snwr, air. Decane‐brine and scCO2‐brine Pc–Sw curves deviated significantly from predictions assuming hydrophilic interactions. Moreover, neither the scaled capillary behavior nor Snw,r for scCO2‐brine were well represented by decane‐brine, apparently because of differences in wettability and viscosities, indicating limitations for using decane (and other organic liquids) as a surrogate fluid in studies intended to apply to geological carbon sequestration. Thus, challenges remain in applying scaling for predicting capillary trapping and multiphase displacement processes across such diverse fields as vadose zone hydrology, enhanced oil recovery, and geologic carbon sequestration. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-16T11:40:31.253229-05:
      DOI: 10.1002/2016WR018816
  • Water flow and multicomponent solute transport in drip irrigated
    • Authors: Iael Raij; Jirka Šimůnek, Alon Ben‐Gal, Naftali Lazarovitch
      Abstract: Controlled experiments and modeling are crucial components in the evaluation of the fate of water and solutes in environmental and agricultural research. Lysimeters are commonly used to determine water and solute balances and assist in making sustainable decisions with respect to soil reclamation, fertilization or irrigation with low quality water. While models are cost‐effective tools for estimating and preventing environmental damage by agricultural activities, their value is highly dependent on the accuracy of their parameterization, often determined by calibration. The main objective of this study was to use measured major ion concentrations collected from drip irrigated lysimeters to calibrate the variably‐saturated water flow model HYDRUS‐(2D/3D) coupled with the reactive transport model UNSATCHEM. Irrigation alternated between desalinated and brackish waters. Lysimeter drainage and soil solution samples were collected for chemical analysis and used to calibrate the model. A second objective was to demonstrate the potential use of the calibrated model to evaluate lower boundary design options of lysimeters with respect to leaching fractions determined using drainage water fluxes, chloride concentrations and overall salinity of drainage water, and exchangeable sodium percentage (ESP) in the profile. The model showed that, in the long term, leaching fractions calculated with electrical conductivity values would be affected by the lower boundary condition pressure head, while those calculated with chloride concentrations and water fluxes would not be affected. In addition, clear dissimilarities in ESP profiles were found between lysimeters with different lower boundary conditions, suggesting a potential influence on hydraulic conductivities and flow patterns. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-16T11:40:26.269905-05:
      DOI: 10.1002/2016WR018930
  • A synthetic study to evaluate the utility of hydrological signatures for
           calibrating a baseflow separation filter
    • Authors: Chun‐Hsu Su; Tim J. Peterson, Justin F. Costelloe, Andrew W. Western
      Abstract: Estimation of baseflow from streamflow hydrographs has been a major challenge in hydrology for decades, leading to developments of baseflow separation filters. When without tracer or groundwater data to calibrate the filters, the standard approach to apply these filters in practice involves some degrees of subjectivity in choosing the filter parameters. This paper investigates the use of signature‐based calibration in implementing baseflow filtering by testing seven possible hydrological signatures of baseflow against modelled daily baseflow produced by Li et al. [2014] for a range of synthetic catchments simulated with HydroGeoSphere. Our evaluation demonstrates that such a calibration method with few selected signatures as objectives is capable of calibrating a filter ‐ Eckhardt filter ‐ to yield satisfactory baseflow estimates at daily, monthly and long‐term time scales, outperforming the standard approach. The best performing signatures can be readily derived from streamflow timeseries. While their performance depends on the catchment characteristics, the catchments where the signature method performs can be distinguished using commonly‐used descriptors of flow dynamics. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-10T09:15:26.196483-05:
      DOI: 10.1002/2015WR018177
  • Fate and transport of dissolved methane and ethane in cretaceous shales of
           the Williston Basin, Canada
    • Authors: M. Jim Hendry; S. Lee Barbour, Erin E. Schmeling, Scott O.C. Mundle, M. Huang
      Abstract: Baseline characteristics of dissolved methane (CH4) and ethane (C2H6) and their stable isotopes in thick, low hydraulic conductivity, Cretaceous shales were determined using high‐resolution core profiling at four sites in the Williston Basin (WB), Canada. Positive correlations with the conservative natural tracer Cl‐ reflected a lack of measureable production or consumption of gases in the shale to the depth investigated (150 m below ground, BG) and suggest CH4 and C2H6 concentrations near the interface with overlying Quaternary sediments are controlled by lateral migration and dilution in permeable zones. Curvilinear increasing concentrations with depth in the shale at all sites coupled with 1‐D solute transport modelling suggest long‐term (over millions of years) upward diffusion of CH4 and C2H6 from deeper WB sources, likely the Second White Speckled Shale Formation (SWSS; ∼790 m BG). δ13C‐CH4 profiles in the shale are consistent with upward diffusional fractionation of isotopes from the SWSS. Distinct CH4 and C2H6 isotope values of gases in the shales vs. 13C‐enriched thermogenic isotopic signatures of CH4 and C2H6 in deeper oil‐producing WB intervals could be used to identify fugitive gases originating deeper in the Basin. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-08T10:13:26.181026-05:
      DOI: 10.1002/2016WR019047
  • Fracture size and transmissivity correlations: Implications for transport
           simulations in sparse three‐dimensional discrete fracture networks
           following a truncated power law distribution of fracture size
    • Authors: J. D. Hyman; G. Aldrich, H. Viswanathan, N. Makedonska, S. Karra
      Abstract: We characterize how different fracture size‐transmissivity relationships influence flow and transport simulations through sparse three‐dimensional discrete fracture networks. Although it is generally accepted that there is a positive correlation between a fracture's size and its transmissivity/aperture, the functional form of that relationship remains a matter of debate. Relationships that assume perfect correlation, semi‐correlation, and non‐correlation between the two have been proposed. To study the impact that adopting one of these relationships has on transport properties, we generate multiple sparse fracture networks composed of circular fractures whose radii follow a truncated power law distribution. The distribution of transmissivities are selected so that the mean transmissivity of the fracture networks are the same and the distributions of aperture and transmissivity in models that include a stochastic term are also the same. We observe that adopting a correlation between a fracture size and its transmissivity leads to earlier breakthrough times and higher effective permeability when compared to networks where no correlation is used. While fracture network geometry plays the principal role in determining where transport occurs within the network, the relationship between size and transmissivity controls the flow speed. These observations indicate DFN modelers should be aware that breakthrough times and effective permeabilities can be strongly influenced by such a relationship in addition to fracture and network statistics. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-06T03:10:59.528861-05:
      DOI: 10.1002/2016WR018806
  • LPMLE3: A novel 1‐D approach to study water flow in streambeds using
           heat as a tracer
    • Authors: U. Schneidewind; M. van Berkel, C. Anibas, G. Vandersteen, C. Schmidt, I. Joris, P. Seuntjens, O. Batelaan, H.J. Zwart
      Abstract: We introduce LPMLE3, a new 1D approach to quantify vertical water flow components at streambeds using temperature data collected in different depths. LPMLE3 solves the partial differential equation for coupled water flow and heat transport in the frequency domain. Unlike other 1D approaches it does not assume a semi‐infinite halfspace with the location of the lower boundary condition approaching infinity. Instead it uses local upper and lower boundary conditions. As such, the streambed can be divided into finite sub‐domains bound at the top and bottom by a temperature‐time series. Information from a third temperature sensor within each sub‐domain is then used for parameter estimation. LPMLE3 applies a low order local polynomial to separate periodic and transient parts (including the noise contributions) of a temperature‐time series and calculates the frequency response of each sub‐domain to a known temperature input at the streambed top. A maximum likelihood estimator is used to estimate the vertical component of water flow, thermal diffusivity and their uncertainties for each streambed sub‐domain and provides information regarding model quality. We tested the method on synthetic temperature data generated with the numerical model STRIVE and demonstrate how the vertical flow component can be quantified for field data collected in a Belgian stream. We show that by using the results in additional analyses, non‐vertical flow components could be identified and by making certain assumptions they could be quantified for each sub‐domain. LPMLE3 performed well on both simulated and field data and can be considered a valuable addition to the existing 1D methods. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-05T03:30:34.497983-05:
      DOI: 10.1002/2015WR017453
  • The effect of the water tariff structures on the water consumption in
           Mallorcan hotels
    • Authors: Bartolomé Deyà‐Tortella; Celso Garcia, William Nilsson, Dolores Tirado
      Abstract: Tourism increases water demand, especially in coastal areas and on islands, and can also cause water shortages during the dry season and the degradation of the water supply. The aim of this study is to evaluate the impact of water price structures on hotel water consumption on the island of Mallorca (Spain). All tourist municipalities on the island use different pricing structures, such as flat or block rates, and different tariffs. This exogenous variation is used to evaluate the effect of prices on water consumption for a sample of 134 hotels. The discontinuity of the water tariff structure and the fixed rate, which depends on the number of hotel beds, generate endogeneity problems. We propose an econometric model, an instrumental variable quantile regression for within artificial blocks transformed data, to solve both problems. The coefficients corresponding to the price variables are not found to be significantly different from zero. The sign of the effect is negative, but the magnitude is negligible: a 1% increase in all prices would reduce consumption by an average of only 0.024%. This result is probably due to the small share of water costs with respect to the total hotel operational costs (around 4%). Our regression model concludes that the introduction of water‐saving initiatives constitutes an effective way to reduce consumption. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-05T03:26:04.706687-05:
      DOI: 10.1002/2016WR018621
  • An upscaling procedure for fractured reservoirs with embedded grids
    • Authors: Alessio Fumagalli; Luca Pasquale, Stefano Zonca, Stefano Micheletti
      Abstract: Upscaling of geological models for reservoir simulation is an active and important area of research. In particular, we are interested in reservoirs where the rock matrix exhibits an intricate network of fractures, which usually acts as a preferential path to the flow. Accounting for fractures' contribution in the simulation of a reservoir is of paramount importance. Here, we have focused on obtaining effective parameters (e.g. transmissibility) on a $3D$computational grid on the reservoir scale, that account for the presence, at a finer spatial scale, of fractures, and a network of fractures. We have, essentially, followed the idea illustrated in Karimi‐Fard et al. [2006], yet this work has some notable aspects of innovation in the way the procedure has been implemented, and in its capability to consider rather general corner‐point grids, like the ones normally used in reservoir simulations in the industry, and complex and realistic fracture networks, possibly not fully connected inside the coarse cells. In particular, novel contribution is the employment of an Embedded Discrete Fracture Model (EDFM) for computing fracture‐fracture and matrix‐fracture transmissibilities, with a remarkable gain in speed‐up. The output is in the form of transmissibility that, although obtained by considering single‐phase flow, can be used for coarse‐scale multiphase reservoir simulations, also via industrial softwares, such as Eclipse, Intersect, or GPRS. The results demonstrate the effectiveness and computational efficiency of the numerical procedure which is now ready for further testing and industrialization. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-05T03:25:58.261644-05:
      DOI: 10.1002/2015WR017729
  • Land‐surface controls on near‐surface soil moisture dynamics:
           Traversing remote sensing footprints
    • Authors: Nandita Gaur; Binayak P. Mohanty
      Abstract: In this new era of remote sensing based hydrology, a major unanswered question is how to incorporate the impact of land‐surface based heterogeneity on soil moisture dynamics at remote sensing scales. The answer to this question is complicated since 1) soil moisture dynamics that vary with support, extent and spacing scales are dependent on land‐surface based heterogeneity and 2) land‐surface based heterogeneity itself is scale‐specific and varies with hydro‐climates. Land‐surface factors such as soil, vegetation and topography affect soil moisture dynamics by redistributing the available soil moisture on the ground. In this study, we determined the contribution of these bio‐physical factors to redistribution of near‐surface soil moisture across a range of remote sensing scales varying from an (airborne) remote sensor footprint (1.6 km) to a (satellite) footprint scale (25.6 km). Two‐dimensional non‐decimated wavelet transform was used to extract the support scale information from the spatial signals of the land‐surface and soil moisture variables. The study was conducted in three hydro‐climates: humid (Iowa), sub‐humid (Oklahoma) and semi‐arid (Arizona). The dominance of soil on soil moisture dynamics typically decreased from airborne to satellite footprint scales whereas the influence of topography and vegetation increased with increasing support scale for all three hydro‐climates. The distinct effect of hydro‐climate was identifiable in the soil attributes dominating the soil moisture dynamics. The near‐surface soil moisture dynamics in Arizona (semi‐arid) can be attributed more to the clay content which is an effective limiting parameter for evaporation whereas in Oklahoma (humid), sand content (limiting parameter for drainage) was the dominant soil attribute. The findings from this study can provide a deeper understanding of the impact of heterogeneity on soil moisture dynamics and the potential improvement of hydrological models operating at footprints' scales. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-05T03:25:51.797734-05:
      DOI: 10.1002/2015WR018095
  • How does reach‐scale stream‐hyporheic transport vary with discharge?
           Insights from rSAS analysis of sequential tracer injections in a headwater
           mountain stream
    • Authors: C. J. Harman; A. S. Ward, A. Ball
      Abstract: The models of stream reach hyporheic exchange that are typically used to interpret tracer data assume steady‐flow conditions, and impose further assumptions about transport processes on the interpretation of the data. Here we show how rank StorAge Selection (rSAS) functions can be used to extract ‘process‐agnostic’ information from tracer breakthrough curves about the time‐varying turnover of reach storage. A sequence of seven slug injections was introduced to a small stream at baseflow over the course of a diel fluctuation in stream discharge, providing breakthrough curves at discharges ranging from 0.7 ‐ 1.2 L/s. Shifted gamma distributions, each with three parameters varying stepwise in time, were used to model the rSAS function and calibrated to reproduce each breakthrough curve with Nash‐Sutcliffe efficiencies in excess of 0.99. Variations in the fitted parameters over time suggested that storage within the reach does not uniformly increase its turnover rate when discharge increases. Rather, changes in transit time are driven by both changes in the average rate of turnover (external variability) and changes in the relative rate that younger and older water contribute to discharge (internal variability). Specifically, at higher discharge the turnover rate increased for the youngest part of the storage (corresponding to approximately 5 times the volume of the channel), while discharge from the older part of the storage remained steady, or declined slightly. The method is shown to be extensible as a new approach to modeling reach‐scale solute transport that accounts for the time‐varying, discharge‐dependent turnover of reach storage. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-05T03:25:49.362354-05:
      DOI: 10.1002/2016WR018832
  • A comparison of watershed storage trends over the eastern and upper
           Midwestern regions of the United States, 2003‐2015
    • Authors: Brian F. Thomas; Felix W. Landerer, David N. Wiese, James S. Famiglietti
      Abstract: Basin‐scale groundwater storage trends calculated from long‐term streamflow records provide insight into the evolution of watershed behaviors. Our study presents the first spatially‐relevant validation of recession‐based trend approaches by comparing three independent storage trend estimates using GRACE‐derived groundwater storage, in‐situ groundwater elevation observations and recession‐based approaches for the time period of 2003‐2015. Results documented consistent agreement between spatially‐interpolated groundwater observation trends and recession‐based storage trends, while GRACE‐derived groundwater trends were found to exhibit variable, poor comparisons. A decreasing trend in watershed storage was identified in the southeastern U.S. while increasing trends were identified in the northeast and upper Midwest estimated from recession‐based approaches. Our recession‐based approach conducted using nested watershed streamflow records identified variable watershed storage trends at scales directly applicable for comparative hydrology studies and for assisting in watershed‐based water resources management decisions. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-05T03:25:38.898223-05:
      DOI: 10.1002/2016WR018617
  • River gauging at global scale using optical and passive microwave remote
    • Authors: Albert I.J.M. Van Dijk; G. Robert Brakenridge, Albert J. Kettner, Hylke E. Beck, Tom De Groeve, Jaap Schellekens
      Abstract: Recent discharge observations are lacking for most rivers globally. Discharge can be estimated from remotely sensed floodplain and channel inundation area, but there is currently no method that can be automatically extended to many rivers. We examined whether automated monitoring is feasible by statistically relating inundation estimates from moderate to coarse (>0.05°) resolution remote sensing to monthly station discharge records. Inundation extents were derived from optical MODIS data and passive microwave sensors, and compared to monthly discharge records from over 8000 gauging stations and satellite altimetry observations for 442 reaches of large rivers. An automated statistical method selected grid cells to construct ‘satellite gauging reaches' (SGRs). MODIS SGRs were generally more accurate than passive microwave SGRs, but there were complementary strengths. The rivers widely varied in size, regime and morphology. As expected performance was low (R0.6. The best results (R>0.9) were obtained for large unregulated lowland rivers, particularly in tropical and boreal regions. Relatively poor results were obtained in arid regions, where flow pulses are few and recede rapidly, and in temperate regions, where many rivers are modified and contained. Where discharge variations produce clear changes in inundated area and gauge records are available for part of the satellite record, SGRs can retrieve monthly river discharge values back to around 1998 and up to present. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-05T03:25:36.052621-05:
      DOI: 10.1002/2015WR018545
  • Physical complexity to model morphological changes at a natural channel
    • Authors: M. Guan; N.G. Wright, P.A. Sleigh, S. Ahilan, R. Lamb
      Abstract: This study developed a two‐dimensional (2D) depth‐averaged model for morphological changes at natural bends by including a secondary flow correction. The model was tested in two laboratory‐scale events. A field study were further adopted to demonstrate the capability of the model in predicting bed deformation at natural bends. Further, a series of scenarios with different setups of sediment‐related parameters were tested to explore the possibility of a 2D model to simulate morphological changes at a natural bend, and to investigate how much physical complexity is needed for reliable modelling. The results suggest that a 2D depth‐averaged model can reconstruct the hydrodynamic and morphological features at a bend reasonably provided that the model addresses a secondary flow correction, and reasonably parameterise grain‐sizes within a channel in a pragmatic way. The factors, such as sediment transport formula and roughness height, have relatively less significance on the bed change pattern at a bend. The study reveals that the secondary flow effect and grain‐size parameterisation should be given a first priority among other parameters when modelling bed deformation at a natural bend using a 2D model. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-05T03:25:31.734679-05:
      DOI: 10.1002/2015WR017917
  • A multiscale multilayer vertically integrated model with vertical dynamics
           for CO2 sequestration in layered geological formations
    • Authors: Bo Guo; Karl W. Bandilla, Jan M. Nordbotten, Michael A. Celia, Eirik Keilegavlen, Florian Doster
      Abstract: Efficient computational models are desirable for simulation of large‐scale geological CO$_2$sequestration. Vertically integrated models, which take advantage of dimension reduction, offer one type of computationally efficient model. The dimension reduction is usually achieved by vertical integration based on the vertical equilibrium (VE) assumption, which assumes that CO$_2$and brine segregate rapidly in the vertical due to strong buoyancy and quickly reach pressure equilibrium. However, the validity of the VE assumption requires small time scales of fluid segregation, which may not always be fulfilled, especially for heterogeneous geological formations with low vertical permeability. Recently,\citet{guo2014vertically} developed a multiscale vertically integrated model, referred to as the dynamic reconstruction (DR) model, that relaxes the VE assumption by including the vertical two‐phase flow dynamics of CO$_2$and brine as fine‐scale one‐dimensional problems in the vertical direction. Although the VE assumption can be relaxed, that model was limited to homogeneous geological formations. Here, we extend the dynamic reconstruction model for layered heterogeneous formations, which is of much more practical interest for saline aquifers in sedimentary basins. We develop a new coarse‐scale pressure equation to couple the different coarse‐scale (vertically integrated) layers, and use the fine‐scale dynamic reconstruction algorithm in\citet{guo2014vertically} within each individual layer. Together, these form a multiscale multilayer dynamic reconstruction algorithm. Simulation results of the CO$_2$plume from the new model are in excellent agreement with full three‐dimensional models, with the new algorithm being much more computationally efficient than conventional full three‐dimensional models. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-05T03:20:44.952163-05:
      DOI: 10.1002/2016WR018714
  • Spatial Bayesian hierarchical modeling of precipitation extremes over a
           large domain
    • Authors: C. Bracken; B. Rajagopalan, L. Cheng, Will Kleiber, Subhrendu Gangopadhyay
      Abstract: We propose a Bayesian hierarchical model for spatial extremes on a large domain. In the data layer a Gaussian elliptical copula having generalized extreme value (GEV) marginals is applied. Spatial dependence in the GEV parameters is captured with a latent spatial regression with spatially varying coefficients. Using a composite likelihood approach, we are able to efficiently incorporate a large precipitation dataset, which includes stations with missing data. The model is demonstrated by application to fall precipitation extremes at approximately 2600 stations covering the western United States, ‐125E to ‐100E longitude and 30N to 50N latitude. The hierarchical model provides GEV parameters on a 1/8th degree grid and, consequently, maps of return levels and associated uncertainty. The model results indicate that return levels and their associated uncertainty have a well‐defined spatial structure. Maps of return levels provide information about the spatial variations of the risk of extreme precipitation in the western US, and is expected to be useful for infrastructure planning. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-05T03:20:40.621127-05:
      DOI: 10.1002/2016WR018768
  • A probabilistic prediction network for hydrological drought identification
           and environmental flow assessment
    • Authors: Zhiyong Liu; Tobias Törnros, Lucas Menzel
      Abstract: A general probabilistic prediction network is proposed for hydrological drought examination and environmental flow assessment. This network consists of three major components. First, we present the joint streamflow drought indicator (JSDI) to describe the hydrological dryness/wetness conditions. The JSDI is established based on a high‐dimensional multivariate probabilistic model. In the second part, a drought‐based environmental flow assessment method is introduced, which provides dynamic risk‐based information about how much flow (the environmental flow target) is required for drought recovery and its likelihood under different hydrological drought initial situations. The final part involves estimating the conditional probability of achieving the required environmental flow under different precipitation scenarios according to the joint dependence structure between streamflow and precipitation. Three watersheds from different countries (Germany, China, and United States) with varying sizes from small to large were used to examine the usefulness of this network. The results show that the JSDI can provide an assessment of overall hydrological dryness/wetness conditions and performs well in identifying both drought onset and persistence. This network also allows quantitative prediction of targeted environmental flow required for hydrological drought recovery and estimation of the corresponding likelihood. Moreover, the results confirm that the general network can estimate the conditional probability associated with the required flow under different precipitation scenarios. The presented methodology offers a promising tool for water supply planning and management and for drought‐based environmental flow assessment. The network has no restrictions that would prevent it from being applied to other basins worldwide. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-29T10:10:22.010356-05:
      DOI: 10.1002/2016WR019106
  • Modeling cosmic‐ray neutron field measurements
    • Authors: Mie Andreasen; Karsten H. Jensen, Marek Zreda, Darin Desilets, Heye Bogena, Majken C. Looms
      Abstract: The cosmic‐ray neutron method was developed for intermediate‐scale soil moisture detection, but may potentially be used for other hydrological applications. The neutron signal of different hydrogen pools is poorly understood and separating them is difficult based on neutron measurements alone. Including neutron transport modeling may accommodate this shortcoming. However, measured and modeled neutrons are not directly comparable. Neither the scale nor energy ranges are equivalent, and the exact neutron energy sensitivity of the detectors is unknown. Here, a methodology to enable comparability of the measured and modeled neutrons is presented. The usual cosmic‐ray soil moisture detector measures moderated neutrons by means of a proportional counter surrounded by plastic, making it sensitive to epithermal neutrons. However, that configuration allows for some thermal neutrons to be measured. The thermal contribution can be removed by surrounding the plastic with a layer of cadmium, which absorbs neutrons with energies below 0.5 eV. Likewise, cadmium‐shielding of a bare detector allows for estimating the epithermal contribution. First, the cadmium difference method is used to determine the fraction of thermal and epithermal neutrons measured by the bare and plastic‐shielded detectors, respectively. The cadmium difference method results in linear correction models for measurements by the two detectors, and has the greatest impact on the neutron intensity measured by the moderated detector at the ground surface. Next, conversion factors are obtained relating measured and modeled neutron intensities. Finally, the methodology is tested by modeling the neutron profiles at an agricultural field site and satisfactory agreement to measurements is found. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-29T10:05:40.168005-05:
      DOI: 10.1002/2015WR018236
  • Modeling early in situ wetting of a compacted bentonite buffer installed
           in low permeable crystalline bedrock
    • Authors: B. Dessirier; A. Frampton, Å. Fransson, J. Jarsjö
      Abstract: The repository concept for geological disposal of spent nuclear fuel in Sweden and Finland is planned to be constructed in sparsely fractured crystalline bedrock and with an engineered bentonite buffer to embed the waste canisters. An important stage in such a deep repository is the post‐closure phase following the deposition and the backfilling operations when the initially unsaturated buffer material gets hydrated by the groundwater delivered by the natural bedrock. We use numerical simulations to interpret observations on buffer wetting gathered during an in situ campaign, the Bentonite Rock Interaction Experiment, in which unsaturated bentonite columns were introduced into deposition holes in the floor of a 417 m deep tunnel at the Äspö Hard Rock Laboratory in Sweden. Our objectives are to assess the performance of state‐of‐the‐art flow models in reproducing the buffer wetting process and to investigate to which extent dependable predictions of buffer wetting times and saturation patterns can be made based on information collected prior to buffer insertion. This would be important for preventing insertion into unsuitable bedrock environments. Field data and modeling results indicate the development of a de‐saturated zone in the rock and show that in most cases, the presence or absence of fractures and flow heterogeneity are more important factors for correct wetting predictions than the total inflow. For instance, for an equal open‐hole inflow value, homogeneous inflow yields much more rapid buffer wetting than cases where fractures are represented explicitly thus creating heterogeneous inflow distributions. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-29T10:05:38.936829-05:
      DOI: 10.1002/2016WR018678
  • Patch‐based iterative conditional geostatistical simulation using
           graph cuts
    • Authors: Xue Li; Gregoire Mariethoz, DeTang Lu, Niklas Linde
      Abstract: Training image‐based geostatistical methods are increasingly popular in groundwater hydrology even if existing algorithms present limitations that often make real‐world applications difficult. These limitations include a computational cost that can be prohibitive for high‐resolution 3D applications, the presence of visual artifacts in the model realizations, and a low variability between model realizations due to the limited pool of patterns available in a finite‐size training image. In this paper, we address these issues by proposing an iterative patch‐based algorithm which adapts a graph cuts methodology that is widely used in computer graphics. Our adapted graph cuts method optimally cuts patches of pixel values borrowed from the training image and assembles them successively, each time accounting for the information of previously stitched patches. The initial simulation result might display artifacts, which are identified as regions of high cost. These artifacts are reduced by iteratively placing new patches in high‐cost regions. In contrast to most patch‐based algorithms, the proposed scheme can also efficiently address point conditioning. An advantage of the method is that the cut process results in the creation of new patterns that are not present in the training image, thereby increasing pattern variability. To quantify this effect, a new measure of variability is developed, the merging index, quantifies the pattern variability in the realizations with respect to the training image. A series of sensitivity analyses demonstrates the stability of the proposed graph cuts approach, which produces satisfying simulations for a wide range of parameters values. Applications to 2D and 3D cases are compared to state‐of‐the‐art multiple‐point methods. The results show that the proposed approach obtains significant speedups and increases variability between realizations. Connectivity functions applied to 2D models transport simulations in 3D models are used to demonstrate that pattern continuity is preserved. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-29T10:05:33.024114-05:
      DOI: 10.1002/2015WR018378
  • River bank geomorphology controls groundwater arsenic concentrations in
           aquifers adjacent to the Red River, Hanoi Vietnam
    • Authors: Mason O. Stahl; Charles F. Harvey, Alexander van Geen, Jing Sun, Pham Thi Kim Trang, Vi Mai Lan, Thao Mai Phuong, Pham Hung Viet, Benjamin C. Bostick
      Abstract: Many aquifers that are highly contaminated by arsenic in South and Southeast Asia are in the floodplains of large river networks. Under natural conditions, these aquifers would discharge into nearby rivers; however large‐scale groundwater pumping has reversed the flow in some areas so that rivers now recharge aquifers. At a field site near Hanoi Vietnam, we find river water recharging the aquifer becomes high in arsenic, reaching concentrations above 1000 μg/L, within the upper meter of recently (< ∼10 yrs) deposited riverbed sediments as it is drawn into a heavily pumped aquifer along the Red River. Groundwater arsenic concentrations in aquifers adjacent to the river are largely controlled by river geomorphology. High (> 50 μg/L) aqueous arsenic concentrations are found in aquifer regions adjacent to zones where the river has recently deposited sediment and low arsenic concentrations are found in aquifer regions adjacent to erosional zones. High arsenic concentrations are even found adjacent to a depositional river reach in a Pleistocene aquifer, a type of aquifer sediment which generally hosts low arsenic water. Using geochemical and isotopic data we estimate the in‐situ rate of arsenic release from riverbed sediments to be up to 1000 times the rates calculated on inland aquifer sediments in Vietnam. Geochemical data for riverbed porewater conditions indicate that the reduction of reactive, poorly crystalline iron oxides controls arsenic release. We suggest that aquifers in these regions may be susceptible to further arsenic contamination where riverine recharge drawn into aquifers by extensive groundwater pumping flows through recently deposited river sediments before entering the aquifer. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-29T10:05:29.694816-05:
      DOI: 10.1002/2016WR018891
  • Integrating desalination to reservoir operation to increase redundancy for
           more secure water supply
    • Authors: Rashi Bhushan; Tze Ling Ng
      Abstract: We investigate the potential of integrating desalination to existing reservoir systems to mitigate supply uncertainty. Desalinated seawater and wastewater are relatively reliable but expensive. Water from natural resources like reservoirs is generally cheaper but climate sensitive. We propose combining the operation of a reservoir, and seawater and wastewater desalination plants for an overall system that is less vulnerable to scarcity and uncertainty, while constraining total cost. The joint system is modeled as a multi‐objective optimization problem with the double objectives of minimizing risk and vulnerability, subject to a minimum limit on resilience. The joint model is applied to two cases, one based on the climate and demands of a location in India and the other of a location in California. The results for the Indian case indicate it possible for the joint system to reduce risk and vulnerability to zero given a budget increase of 20‐120% under current climate conditions and 30‐150% under projected future conditions. For the Californian case, this would require budget increases of 20‐80% and 30‐140% under current and future conditions respectively. Further, our analysis shows a two‐way interaction between the reservoir and desalination plants where the optimal operation of the former is just as much affected by the latter as the latter by the former. This highlights the importance of an integrated management approach. This study contributes to a greater quantitative understanding of desalination as a redundancy measure for adapting water supply infrastructures for a future of greater scarcity and uncertainty. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-29T10:05:26.318876-05:
      DOI: 10.1002/2015WR018373
  • Conceptualizing sociohydrological drought processes: The case of the Maya
    • Authors: Linda Kuil; Gemma Carr, Alberto Viglione, Alexia Prskawetz, Günter Blöschl
      Abstract: With population growth, increasing water demands and climate change the need to understand the current and future pathways to water security is becoming more pressing. To contribute to addressing this challenge, we examine the link between water stress and society through socio‐hydrological modeling. We conceptualize the interactions between an agricultural society with its environment in a stylized way. We apply the model to the case of the ancient Maya, a population that experienced a peak during the Classic Period (AD 600‐830) and then declined during the ninth century. The hypothesis that modest drought periods played a major role in the society's collapse is explored. Simulating plausible feedbacks between water and society we show that a modest reduction in rainfall may lead to an 80% population collapse.Population density and crop sensitivity to droughts, however, may play an equally important role. The simulations indicate that construction of reservoirs results in less frequent drought impacts, but if the reservoirs run dry, drought impact may be more severe and the population drop may be larger. Index terms: 1812 Drought (4303) 1834 Human impacts (4323) 4330 Vulnerability. Keywords: socio‐hydrology, Ancient Maya, drought, vulnerability. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-25T18:05:35.078243-05:
      DOI: 10.1002/2015WR018298
  • Interactions among hydraulic conductivity distributions, subsurface
           topography, and transport thresholds revealed by a multitracer hillslope
           irrigation experiment
    • Authors: C. Rhett Jackson; Enhao Du, Julian Klaus, Natalie A. Griffiths, Menberu Bitew, Jeffrey J. McDonnell
      Abstract: Interactions among hydraulic conductivity distributions, subsurface topography, and lateral flow are poorly understood. We applied 407 mm of water and a suite of tracers over 51 hours to a 12 by 16.5 m forested hillslope segment to determine interflow thresholds, preferential pathway pore velocities, large‐scale conductivities, the time series of event water fractions, and the fate of dissolved nutrients. The 12% hillslope featured loamy sand A and E horizons overlying a sandy clay loam Bt at 1.25 m average depth. Interflow measured from two drains within an interception trench commenced after 131 and 208 mm of irrigation. Cumulative interflow equaled 49% of applied water. Conservative tracer differences between the collection drains indicated differences in flow paths and storages within the plot. Event water fractions rose steadily throughout irrigation, peaking at 50% sixteen hours after irrigation ceased. Data implied that tightly held water exchanged with event water throughout the experiment and a substantial portion of pre‐event water was released from the argillic layer. Surface‐applied dye tracers bypassed the matrix, with peak concentrations measured shortly after flow commencement, indicating preferential network conductivities of 864 to 2240 mm/h, yet no macropore flow was observed. Near steady‐state flow conditions indicated average conductivities of 460 mm/h and 2.5 mm/h for topsoils and the Bt horizon, respectively. Low ammonium and phosphorus concentrations in the interflow suggested rapid uptake or sorption, while higher nitrate concentrations suggested more conservative transport. These results reveal how hydraulic conductivity variation and subsurface topographic complexity explain otherwise paradoxical solute and flow behaviors. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-22T10:20:24.209352-05:
      DOI: 10.1002/2015WR018364
  • Transit time distributions and StorAge Selection functions in a sloping
           soil lysimeter with time‐varying flow paths: Direct observation of
           internal and external transport variability
    • Authors: Minseok Kim; Luke Pangle, Charléne Cardoso, Marco Lora, Till Volkmann, Yadi Wang, Ciaran Harman, Peter Troch
      Abstract: Transit times through hydrologic systems vary in time, but the nature of that variability is not well understood. Transit times variability was investigated in a 1 m3 sloping lysimeter, representing a simplified model of a hillslope receiving periodic rainfall events for 28 days. Tracer tests were conducted using an experimental protocol that allows time‐variable transit time distributions (TTDs) to be calculated from data. Observed TTDs varied with the storage state of the system, and the history of inflows and outflows. We propose that the observed time variability of the TTDs can be decomposed into two parts: ‘internal' variability associated with changes in the arrangement of, and partitioning between, flow pathways; and ‘external' variability driven by fluctuations in the flow rate along all flow pathways. These concepts can be defined quantitatively in terms of rank StorAge Selection (rSAS) functions, which is a theory describing lumped transport dynamics. Internal variability is associated with temporal variability in the rSAS function, while external is not. The rSAS function variability was characterized by an ‘inverse storage effect', whereby younger water is released in greater proportion under wetter conditions than drier. We hypothesize that this effect is caused by the rapid mobilization of water in the unsaturated zone by the rising water table. Common approximations used to model transport dynamics that neglect internal variability were unable to reproduce the observed breakthrough curves accurately. This suggests that internal variability can play an important role in hydrologic transport dynamics, with implications for field data interpretation and modeling. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-22T10:15:26.760708-05:
      DOI: 10.1002/2016WR018620
  • Closed‐flow column experiments: A numerical sensitivity analysis of
           reactive transport and parameter uncertainty
    • Authors: Thomas Ritschel; Kai Uwe Totsche
      Abstract: The identification of transport parameters by inverse modeling often suffers from equifinality or parameter correlation when models are fitted to measurements of the solute breakthrough in column outflow experiments. This parameter uncertainty can be approached by performing multiple experiments with different sets of boundary conditions, each provoking observations that are uniquely attributable to the respective transport processes. A promising approach to further increase the information potential of the experimental outcome is the closed‐flow column design. It is characterized by the recirculation of the column effluent into the solution supply vessel that feeds the inflow, which results in a damped sinusoidal oscillation in the breakthrough curve. In order to reveal the potential application of closed‐flow experiments, we present a comprehensive sensitivity analysis using common models for adsorption and degradation. We show that the sensitivity of inverse parameter determination with respect to the apparent dispersion can be controlled by the experimenter. For optimal settings, a decrease in parameter uncertainty as compared to classical experiments by an order of magnitude is achieved. In addition, we show a reduced equifinality between rate‐limited interactions and apparent dispersion. Furthermore, we illustrate the expected breakthrough curve for equilibrium and nonequilibrium adsorption, the latter showing strong similarities to the behavior found for completely mixed batch reactor experiments. Finally, breakthrough data from a reactive tracer experiment is evaluated using the proposed framework with excellent agreement of model and experimental results. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-22T10:10:25.162622-05:
      DOI: 10.1002/2015WR018388
  • A proposal of optimal sampling design using a modularity strategy
    • Authors: A. Simone; O. Giustolisi, D.B. Laucelli
      Abstract: In real water distribution networks (WDNs) are present thousands nodes and optimal placement of pressure and flow observations is a relevant issue for different management tasks. The planning of pressure observations in terms of spatial distribution and number is named sampling design and it was faced considering model calibration. Nowadays, the design of system monitoring is a relevant issue for water utilities e.g. in order to manage background leakages, to detect anomalies and bursts, to guarantee service quality, etc. In recent years, the optimal location of flow observations related to design of optimal district metering areas (DMAs) and leakage management purposes has been faced considering optimal network segmentation and the modularity index using a multi‐objective strategy. Optimal network segmentation is the basis to identify network modules by means of optimal conceptual cuts, which are the candidate locations of closed gates or flow meters creating the DMAs. Starting from the WDN‐oriented modularity index, as a metric for WDN segmentation, this paper proposes a new way to perform the sampling design, i.e. the optimal location of pressure meters, using newly developed sampling‐oriented modularity index. The strategy optimizes the pressure monitoring system mainly based on network topology and weights assigned to pipes according to the specific technical tasks. A multi‐objective optimization minimizes the cost of pressure meters while maximizing the sampling‐oriented modularity index. The methodology is presented and discussed using the Apulian and Exnet networks. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-22T10:05:25.677572-05:
      DOI: 10.1002/2016WR018944
  • Identification of temporal consistency in rating curve data: Bidirectional
           Reach (BReach)
    • Authors: Katrien Van Eerdenbrugh; Stijn Van Hoey, Niko E.C. Verhoest
      Abstract: In this paper, a methodology is developed to identify consistency of rating curve data based on a quality analysis of model results. This methodology, called Bidirectional Reach (BReach), evaluates results of a rating curve model with randomly sampled parameter sets in each observation. The combination of a parameter set and an observation is classified as non‐acceptable if the deviation between the accompanying model result and the measurement exceeds observational uncertainty. Based on this classification, conditions for satisfactory behavior of a model in a sequence of observations are defined. Subsequently, a parameter set is evaluated in a data point by assessing the span for which it behaves satisfactory in the direction of the previous (or following) chronologically sorted observations. This is repeated for all sampled parameter sets and results are aggregated by indicating the endpoint of the largest span, called the maximum left (right) reach. This temporal reach should not be confused with a spatial reach (indicating a part of a river). The same procedure is followed for each data point and for different definitions of satisfactory behavior. Results of this analysis enable the detection of changes in data consistency. The methodology is validated with observed data and various synthetic stage‐discharge data sets and proves to be a robust technique to investigate temporal consistency of rating curve data. It provides satisfying results despite of low data availability, errors in the estimated observational uncertainty and a rating curve model that is known to cover only a limited part of the observations. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-22T10:05:24.562282-05:
      DOI: 10.1002/2016WR018692
  • Model simulations of flood and debris flow timing in steep catchments
           after wildfire
    • Authors: F. K. Rengers; L. A. McGuire, J. W. Kean, D. M. Staley, D. E. J. Hobley
      Abstract: Debris flows are a typical hazard on steep slopes after wildfire, but unlike debris flows that mobilize from landslides, most post‐wildfire debris flows are generated from water runoff. The majority of existing debris‐flow modeling has focused on landslide‐triggered debris flows. In this study we explore the potential for using process‐based rainfall‐runoff models to simulate the timing of water flow and runoff‐generated debris flows in recently burned areas. Two different spatially distributed hydrologic models with differing levels of complexity were used: the full shallow water equations and the kinematic wave approximation. Model parameter values were calibrated in two different watersheds, spanning two orders of magnitude in drainage area. These watersheds were affected by the 2009 Station Fire in the San Gabriel Mountains, CA, USA. Input data for the numerical models were constrained by time series of soil moisture, flow stage, and rainfall collected at field sites, as well as high‐resolution lidar‐derived digital elevation models. The calibrated parameters were used to model a third watershed in the burn area, and the results show a good match with observed timing of flow peaks. The calibrated roughness parameter (Manning's $n$) was generally higher when using the kinematic wave approximation relative to the shallow water equations, and decreased with increasing spatial scale. The calibrated effective watershed hydraulic conductivity was low for both models, even for storms occurring several months after the fire, suggesting that wildfire‐induced changes to soil‐water infiltration were retained throughout that time. Overall the two model simulations were quite similar suggesting that a kinematic wave model, which is simpler and more computationally efficient, is a suitable approach for predicting flood and debris flow timing in steep, burned watersheds. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-15T04:20:31.572887-05:
      DOI: 10.1002/2015WR018176
  • Spatial statistical network models for stream and river temperature in New
           England, USA
    • Authors: Naomi E. Detenbeck; Alisa Morrison, Ralph W. Abele, Darin Kopp
      Abstract: Watershed managers are challenged by the need for predictive temperature models with sufficient accuracy and geographic breadth for practical use. We described thermal regimes of New England rivers and streams based on a reduced set of metrics for the May to September growing season (July or August median temperature, diurnal rate of change, and magnitude and timing of growing season maximum) chosen through principal component analysis of 78 candidate metrics. We then developed and assessed spatial statistical models for each of these metrics, incorporating spatial autocorrelation based on both distance along the flow network and Euclidean distance between points. Calculation of spatial autocorrelation based on travel or retention time in place of network distance yielded tighter‐fitting Torgegrams with less scatter but did not improve overall model prediction accuracy. We predicted monthly median July or August stream temperatures as a function of median air temperature, estimated urban heat island effect, shaded solar radiation, main channel slope, watershed storage (percent lake and wetland area), percent coarse‐grained surficial deposits, and presence or maximum depth of a lake immediately upstream, with an overall root‐mean‐square prediction error of 1.4 and 1.5○ C, respectively. Growing season maximum water temperature varied as a function of air temperature, local channel slope, shaded August solar radiation, imperviousness, and watershed storage. Predictive models for July or August daily range, maximum daily rate of change, and timing of growing season maximum were statistically significant but explained a much lower proportion of variance than the above models (5‐14% of total) . This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-14T09:26:31.163676-05:
      DOI: 10.1002/2015WR018349
  • Accurate early and late time modelling of countercurrent spontaneous
    • Authors: Rafael March; Florian Doster, Sebastian Geiger
      Abstract: Spontaneous counter‐current imbibition into a finite porous medium is an important physical mechanism for many applications, included but not limited to irrigation, CO2 storage and oil recovery. Symmetry considerations that are often valid in fractured porous media allow us to study the process in a one‐dimensional domain. In 1D, the onset of imbibition can be captured by self‐similar solutions and the imbibed volume scales with . At later times, the imbibition rate decreases and the finite size of the medium has to be taken into account. This requires numerical solutions. Here, we present a new approach to approximate the whole imbibition process semi‐analytically. While the onset is captured by a semi‐analytical solution. We also provide an a priori estimate of the time until which the imbibed volume scales with . This time is significantly longer than the time it takes until the imbibition front reaches the model boundary. The remainder of the imbibition process is obtained from a self‐similarity solution. We test our approach against numerical solutions that employ parametrizations relevant for oil recovery and CO2 sequestration. We show that this concept improves common first order approaches that heavily underestimate early‐time behaviour and note that it can be readily included into dual porosity models. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-14T09:15:36.934337-05:
      DOI: 10.1002/2015WR018456
  • Groundwater depletion in Central Mexico: Use of GRACE and InSAR to support
           water resources management
    • Authors: Pascal Castellazzi; Richard Martel, Alfonso Rivera, Jianliang Huang, Pavlic Goran, Angus I. Calderhead, Estelle Chaussard, Jaime Garfias, Javier Salas
      Abstract: Groundwater deficits occur in several areas of Central Mexico, where water resource assessment is limited by the availability and reliability of field data. In this context, GRACE and InSAR are used to remotely assess groundwater storage loss in one of Mexico's most important watersheds in terms of size and economic activity: the Lerma‐Santiago‐Pacifico (LSP). In situ data and Land Surface Models are used to subtract soil moisture and surface water storage changes from the total water storage change measured by GRACE satellites. As a result, groundwater mass change time‐series are obtained for a 12 years period. ALOS‐PALSAR images acquired from 2007 to 2011 were processed using the SBAS‐InSAR algorithm to reveal areas subject to ground motion related to groundwater over‐exploitation. In the perspective of providing guidance for groundwater management, GRACE and InSAR observations are compared with official water budgets and field observations.InSAR‐derived subsidence mapping generally agrees well with official water budgets, and shows that deficits occur mainly in cities and irrigated agricultural areas. GRACE does not entirely detect the significant groundwater losses largely reported by official water budgets, literature and InSAR observations. The difference is interpreted as returns of wastewater to the groundwater flow systems, which limits the watershed scale groundwater depletion but suggests major impacts on groundwater quality. This phenomenon is enhanced by ground fracturing as noticed in the field. Studying the fate of the extracted groundwater is essential when comparing GRACE data with higher resolution observations, and particularly in the perspective of further InSAR/GRACE combination in hydrogeology. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-14T09:10:26.37054-05:0
      DOI: 10.1002/2015WR018211
  • Extending theis' solution: Using transient pumping tests to estimate
           parameters of aquifer heterogeneity
    • Authors: Alraune Zech; Sebastian Müller, Juliane Mai, Falk Heße, Sabine Attinger
      Abstract: A framework for interpreting transient pumping tests in heterogeneous transmissivity fields is developed to infer the overall geostatistical parameters of the medium without reconstructing the specific heterogeneous structure point wise. The methodology of Radial Coarse Graining is applied to deduce an effective radial description of multi‐Gaussian transmissivity. It was used to derive an Effective Well Flow Solution for transient flow conditions including not only the storativity, but also the geometric mean, the variance, and the correlation length of log‐transmissivity. This solution is shown to be appropriate to characterize the pumping test drawdown behavior in heterogeneous transmissivity fields making use of ensembles of simulated pumping tests with multiple combinations of statistical parameters. Based on the Effective Well Flow Solution, a method is developed for inferring heterogeneity parameters from transient pumping test drawdown data by inverse estimation. Thereby, the impact of statistical parameters on the drawdown is analyzed, allowing to determine the dependence of reliability of parameter estimates on location and number of measurements. It is shown, that the number of measurements can be reduced compared to steady state pumping tests. Finally, a sampling strategy for single aquifer analysis is developed, which allows to estimate the statistical parameters, in particular variance and correlation length for individual heterogeneous transmissivity fields making use of transient pumping test measurements at multiple locations. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-29T10:50:26.072949-05:
      DOI: 10.1002/2015WR018509
  • Assimilation of temperature and hydraulic gradients for quantifying the
           spatial variability of streambed hydraulics
    • Authors: Xiang Huang; Charles B. Andrews, Jie Liu, Yingying Yao, Chuankun Liu, Scott W. Tyler, John S. Selker, Chunmiao Zheng
      Abstract: Understanding the spatial and temporal characteristics of water flux into or out of shallow aquifers is imperative for water resources management and eco‐environmental conservation. In this study, the spatial variability in the vertical specific fluxes and hydraulic conductivities in a streambed were evaluated by integrating distributed temperature sensing (DTS) data and vertical hydraulic gradients into an ensemble Kalman filter (EnKF) and smoother (EnKS) and an empirical thermal‐mixing model. The formulation of the EnKF/EnKS assimilation scheme is based on a discretized 1D advection‐conduction equation of heat transfer in the streambed. We first systematically tested a synthetic case and performed quantitative and statistical analyses to evaluate the performance of the assimilation schemes. Then a real‐world case was evaluated to calculate assimilated specific flux. An initial estimate of the spatial distributions of the vertical hydraulic gradients was obtained from an empirical thermal‐mixing model under steady‐state conditions using a constant vertical hydraulic conductivity. Then, this initial estimate was updated by repeatedly dividing the assimilated specific flux by estimates of the vertical hydraulic gradients to obtain a refined spatial distribution of vertical hydraulic gradients and vertical hydraulic conductivities.Our results indicate that optimal parameters can be derived with fewer iterations but greater simulation effort using the EnKS compared with the EnKF. For the field application in a stream segment of the Heihe River Basin in northwest China, the average vertical hydraulic conductivities in the streambed varied over three orders of magnitude (5 × 10−1 to 5 × 102 m/d). The specific fluxes ranged from near zero (qz 
      PubDate: 2016-06-29T10:50:25.077859-05:
      DOI: 10.1002/2015WR018408
  • Assessment of a numerical model to reproduce event‐scale erosion and
           deposition distributions in a braided river
    • Authors: R.D. Williams; R. Measures, M. Hicks, J. Brasington
      Abstract: Numerical morphological modelling of braided rivers, using a physics‐based approach, is increasingly used as a technique to explore controls on river pattern and, from an applied perspective, to simulate the impact of channel modifications. This paper assesses a depth averaged non‐uniform sediment model (Delft3D) to predict the morphodynamics of a 2.5 km long reach of the braided Rees River, New Zealand, during a single high‐flow event. Evaluation of model performance primarily focused upon using high‐resolution Digital Elevation Models (DEMs) of Difference, derived from a fusion of terrestrial laser scanning and optical empirical bathymetric mapping, to compare observed and predicted patterns of erosion and deposition, and reach scale sediment budgets. For the calibrated model, this was supplemented with planform metrics (e.g. braiding intensity). Extensive sensitivity analysis of model functions and parameters was executed, including consideration of numerical scheme for bedload component calculations, hydraulics, bed composition, bedload transport and bed slope effects, bank erosion and frequency of calculations. Total predicted volumes of erosion and deposition corresponded well to those observed. The difference between predicted and observed volumes of erosion was less than the factor of two that characterises the accuracy of the Gaeuman et al. bedload transport formula. Grain size distributions were best represented using two‐phi intervals. For unsteady flows, results were sensitive to the morphological time scale factor. The approach of comparing observed and predicted morphological sediment budgets shows the value of using natural experiment datasets for model testing. Sensitivity results are transferable to guide Delft3D applications to other rivers. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-20T11:00:34.465962-05:
      DOI: 10.1002/2015WR018491
  • Issue Information
    • Pages: 5705 - 5707
      PubDate: 2016-09-20T01:20:54.987004-05:
      DOI: 10.1002/wrcr.21699
  • Stochastic simulation of soil particle‐size curves in heterogeneous
           aquifer systems through a Bayes space approach
    • Authors: A. Menafoglio; A. Guadagnini, P. Secchi
      Pages: 5708 - 5726
      Abstract: We address the problem of stochastic simulation of soil particle‐size curves (PSCs) in heterogeneous aquifer systems. Unlike traditional approaches that focus solely on a few selected features of PSCs (e.g., selected quantiles), our approach considers the entire particle‐size curves and can optionally include conditioning on available data. We rely on our prior work to model PSCs as cumulative distribution functions and interpret their density functions as functional compositions. We thus approximate the latter through an expansion over an appropriate basis of functions. This enables us to (a) effectively deal with the data dimensionality and constraints and (b) to develop a simulation method for PSCs based upon a suitable and well defined projection procedure. The new theoretical framework allows representing and reproducing the complete information content embedded in PSC data. As a first field application, we demonstrate the quality of unconditional and conditional simulations obtained with our methodology by considering a set of particle‐size curves collected within a shallow alluvial aquifer in the Neckar river valley, Germany.
      PubDate: 2016-08-02T05:25:20.171375-05:
      DOI: 10.1002/2015WR018369
  • Travel times in the vadose zone: Variability in space and time
    • Authors: Matthias Sprenger; Stefan Seeger, Theresa Blume, Markus Weiler
      Pages: 5727 - 5754
      Abstract: Water travel times reflect hydrological processes, yet we know little about how travel times in the unsaturated zone vary with time. Using the soil physical model HYDRUS‐1D, we derived time variable travel time distributions for 35 study sites within the Attert catchment in Luxembourg. While all sites experience similar climatic forcing, they differ with regard to soil types (16 Cambisols, 12 Arenosols, and 7 Stagnosols) and the vegetation cover (29 forest and 6 grassland). We estimated site specific water flow and transport parameters by fitting the model simulations to observed soil moisture time series and depth profiles of pore water stable isotopes. With the calibrated model, we tracked the water parcels introduced with each rainfall event over a period of several years. Our results show that the median travel time of water from the soil surface to depths down to 200 cm is mainly driven by the subsequent rainfall amounts. The median time until precipitation is taken up by roots is governed by the seasonality of evapotranspiration rates. The ratio between the amount of water that leaves the soil profile by on the one hand and evaporation and transpiration on the other hand also shows an annual cycle. This time variable response due to climatic forcing is furthermore visible in the multimodal nature of the site specific master transit time distribution representing the flow‐averaged probability density for rainwater to become recharge. The spatial variability of travel times is mainly driven by soil texture and structure, with significant longer travel times for the clayey Stagnosols than for the loamy to sandy Cambisols and Arenosols.
      PubDate: 2016-08-05T07:50:06.124043-05:
      DOI: 10.1002/2015WR018077
  • Simulation of root water uptake under consideration of nonequilibrium
           dynamics in the rhizosphere
    • Authors: Eva Kroener; Mohsen Zarebanadkouki, Marco Bittelli, Andrea Carminati
      Pages: 5755 - 5770
      Abstract: The narrow region of soil around roots, the so‐called rhizosphere, defers in its hydraulic properties from the bulk soil. The rhizosphere hydraulic properties primarily depend on the drying and wetting rate of mucilage, a polymeric gel exuded by plant roots. Under equilibrium conditions mucilage increases the water holding capacity. Upon drying mucilage turns hydrophobic and makes the rhizosphere temporarily water repellent. There are several models of root water uptake, from analytical models of water flow to a single root to complex numerical models that consider the root architecture. Most of these models, however, do not account for the specific hydraulic properties of the rhizosphere. Here we describe a single‐root model that includes the altered hydraulic properties of the rhizosphere due to mucilage exudation. We use the model to reproduce existing experiments reporting unexpected and puzzling hysteresis in the rhizosphere, which could not be explained under the assumption of homogeneous hydraulic properties. In our model the hydraulic properties depend on the concentration of mucilage. This enables a continuous transition from the bulk soil to the root surface. We assumed that: (a) mucilage increases the water holding capacity in equilibrium conditions, (b) hydrophobicity, swelling and shrinking of mucilage cause a nonequilibrium relation between water content and water potential and (c) mucilage reduces the mobility of water molecules in the liquid phase resulting in a lower hydraulic conductivity at a given water content. Our model reproduces well the experiments and suggests that mucilage softens drought stress in plants during severe drying events.
      PubDate: 2016-08-05T09:19:47.629903-05:
      DOI: 10.1002/2015WR018579
  • Compositional data analysis as a robust tool to delineate hydrochemical
           facies within and between gas‐bearing aquifers
    • Authors: D. Des. R. Owen; V. Pawlowsky‐Glahn, J. J. Egozcue, A. Buccianti, J. M. Bradd
      Pages: 5771 - 5793
      Abstract: Isometric log ratios of proportions of major ions, derived from intuitive sequential binary partitions, are used to characterize hydrochemical variability within and between coal seam gas (CSG) and surrounding aquifers in a number of sedimentary basins in the USA and Australia. These isometric log ratios are the coordinates corresponding to an orthonormal basis in the sample space (the simplex). The characteristic proportions of ions, as described by linear models of isometric log ratios, can be used for a mathematical‐descriptive classification of water types. This is a more informative and robust method of describing water types than simply classifying a water type based on the dominant ions. The approach allows (a) compositional distinctions between very similar water types to be made and (b) large data sets with a high degree of variability to be rapidly assessed with respect to particular relationships/compositions that are of interest. A major advantage of these techniques is that major and minor ion components can be comprehensively assessed and subtle processes—which may be masked by conventional techniques such as Stiff diagrams, Piper plots, and classic ion ratios—can be highlighted. Results show that while all CSG groundwaters are dominated by Na, HCO3, and Cl ions, the proportions of other ions indicate they can evolve via different means and the particular proportions of ions within total or subcompositions can be unique to particular basins. Using isometric log ratios, subtle differences in the behavior of Na, K, and Cl between CSG water types and very similar Na‐HCO3 water types in adjacent aquifers are also described. A complementary pair of isometric log ratios, derived from a geochemically‐intuitive sequential binary partition that is designed to reflect compositional variability within and between CSG groundwater, is proposed. These isometric log ratios can be used to model a hydrochemical pathway associated with methanogenesis and/or to delineate groundwater associated with high gas concentrations.
      PubDate: 2016-08-05T07:47:12.176071-05:
      DOI: 10.1002/2015WR018386
  • Impact of topography on groundwater salinization due to ocean surge
    • Authors: Xuan Yu; Jie Yang, Thomas Graf, Mohammad Koneshloo, Michael A. O'Neal, Holly A. Michael
      Pages: 5794 - 5812
      Abstract: Sea‐level rise and increases in the frequency and intensity of ocean surges caused by climate change are likely to exacerbate adverse effects on low‐lying coastal areas. The landward flow of water during ocean surges introduces salt to surficial coastal aquifers and threatens groundwater resources. Coastal topographic features (e.g., ponds, dunes, barrier islands, and channels) likely have a strong impact on overwash and salinization processes, but are generally highly simplified in modeling studies. To understand topographic impacts on groundwater salinization, we modeled a theoretical overwash event and variable‐density groundwater flow and salt transport in 3‐D using the fully coupled surface and subsurface numerical simulator, HydroGeoSphere. The model simulates the coastal aquifer as an integrated system considering overland flow, coupled surface and subsurface exchange, variably saturated flow, and variable‐density groundwater flow. To represent various coastal landscape types, we simulated both synthetic fields and real‐world coastal topography from Delaware, USA. The groundwater salinization assessment suggested that the topographic connectivity promoting overland flow controls the volume of aquifer that is salinized. In contrast, the amount of water that can be stored in surface depressions determines the amount of seawater that infiltrates the subsurface and the time for seawater to flush from the aquifer. Our study suggests that topography has a significant impact on groundwater salinization due to ocean surge overwash, with important implications for coastal land management and groundwater vulnerability assessment.
      PubDate: 2016-08-05T07:43:38.523867-05:
      DOI: 10.1002/2016WR018814
  • Biofilm effect on soil hydraulic properties: Experimental investigation
           using soil‐grown real biofilm
    • Authors: Elazar Volk; Sascha C. Iden, Alex Furman, Wolfgang Durner, Ravid Rosenzweig
      Pages: 5813 - 5828
      Abstract: Understanding the influence of attached microbial biomass on water flow in variably saturated soils is crucial for many engineered flow systems. So far, the investigation of the effects of microbial biomass has been mainly limited to water‐saturated systems. We have assessed the influence of biofilms on the soil hydraulic properties under variably saturated conditions. A sandy soil was incubated with Pseudomonas Putida and the hydraulic properties of the incubated soil were determined by a combination of methods. Our results show a stronger soil water retention in the inoculated soil as compared to the control. The increase in volumetric water content reaches approximately 0.015 cm3 cm−3 but is only moderately correlated with the carbon deficit, a proxy for biofilm quantity, and less with the cell viable counts. The presence of biofilm reduced the saturated hydraulic conductivity of the soil by up to one order of magnitude. Under unsaturated conditions, the hydraulic conductivity was only reduced by a factor of four. This means that relative water conductance in biofilm‐affected soils is higher compared to the clean soil at low water contents, and that the unsaturated hydraulic conductivity curve of biofilm‐affected soil cannot be predicted by simply scaling the saturated hydraulic conductivity. A flexible parameterization of the soil hydraulic functions accounting for capillary and noncapillary flow was needed to adequately describe the observed properties over the entire wetness range. More research is needed to address the exact flow mechanisms in biofilm‐affected, unsaturated soil and how they are related to effective system properties.
      PubDate: 2016-08-05T07:45:19.578085-05:
      DOI: 10.1002/2016WR018866
  • Hydrograph variances over different timescales in hydropower production
    • Authors: Nicholas Zmijewski; Anders Wörman
      Pages: 5829 - 5846
      Abstract: The operation of water reservoirs involves a spectrum of timescales based on the distribution of stream flow travel times between reservoirs, as well as the technical, environmental, and social constraints imposed on the operation. In this research, a hydrodynamically based description of the flow between hydropower stations was implemented to study the relative importance of wave diffusion on the spectrum of hydrograph variance in a regulated watershed. Using spectral decomposition of the effluence hydrograph of a watershed, an exact expression of the variance in the outflow response was derived, as a function of the trends of hydraulic and geomorphologic dispersion and management of production and reservoirs. We show that the power spectra of involved time‐series follow nearly fractal patterns, which facilitates examination of the relative importance of wave diffusion and possible changes in production demand on the outflow spectrum. The exact spectral solution can also identify statistical bounds of future demand patterns due to limitations in storage capacity. The impact of the hydraulic description of the stream flow on the reservoir discharge was examined for a given power demand in River Dalälven, Sweden, as function of a stream flow Peclet number. The regulation of hydropower production on the River Dalälven generally increased the short‐term variance in the effluence hydrograph, whereas wave diffusion decreased the short‐term variance over periods of
      PubDate: 2016-08-05T07:40:41.262138-05:
      DOI: 10.1002/2015WR017775
  • Change in streamflow response in unregulated catchments in Sweden over the
           last century
    • Authors: Anna Åkesson; Anders Wörman, Joakim Riml, Jan Seibert
      Pages: 5847 - 5867
      Abstract: A Fourier spectral analysis of daily discharge time series over the last century in 79 unregulated catchments in Sweden reveals a significant gradual steepening of the discharge power spectrum slope over time. Where historical meteorological observations are available (the 41 southernmost catchments), the results of our analyses indicate that local land use changes within the catchments have affected discharge power spectra to a greater extent than have changes in precipitation patterns. 1‐D distributed routing analysis based on current and historical maps and scenario modeling in the Törnestorp Catchment suggests that changes in stream network properties have led to increases in the hydraulic Péclet number (Pe) and subsequent decreases in the discharge power spectrum over short periods. The analysis displays analytically how a change in stream network properties can result in changes in the power spectra, where the relative importance of the geomorphological and hydrodynamic dispersion effects determines the shape of the streamflow response. The lowering of the discharge power spectrum over short periods observed for many Swedish catchments is likely caused by increasing Pe (a decrease in dispersion) over time, resulting in higher peak values, especially for rapid streamflow responses (i.e., over short periods), demonstrated empirically for the Törnestorp case study. The finding that the discharge power spectrum can change significantly over time highlights the need for hydrological models to account for the effect of the nonstationarity of parameters that result from temporal change caused by land use change and/or climate change that is due to anthropogenic or natural causes.
      PubDate: 2016-08-05T09:32:13.305964-05:
      DOI: 10.1002/2015WR018116
  • Minimizing the effects of filtering on catchment scale GRACE solutions
    • Authors: Bramha Dutt Vishwakarma; Balaji Devaraju, Nico Sneeuw
      Pages: 5868 - 5890
      Abstract: The Gravity Recovery and Climate Experiment (grace) satellite mission has provided time variable gravity information since its launch in 2002. Due to short‐wavelength noise, the total water storage variations over a catchment observed from grace are usable only after filtering. Filtering smooths both the signal and the noise, inevitably changing the nature of the estimated total water storage change. The filtered estimates suffer from attenuation and leakage, which changes the signal characteristics. Several studies have mainly focused on correcting the changed amplitude with the aid of hydrological models. In this study, it is demonstrated that in addition to the amplitude loss, also significant phase change in the time series of total water storage over a region can occur. The phase change due to leakage from nearby catchments can be around 20° to 30° for catchments with moderate size, which makes it difficult to retrieve signal by only scaling. We propose a strategy to approach the true time series with improved phase and amplitude. The strategy is independent of any hydrological model. It is first demonstrated in a closed‐loop environment over 32 catchments, where we show that the performance of our method is consistent and better than other model‐dependent approaches. Then we also discuss the limitations of our approach. Finally we apply our method to the grace level 2 products for 32 catchments.
      PubDate: 2016-08-06T09:11:12.751705-05:
      DOI: 10.1002/2016WR018960
  • Tap water isotope ratios reflect urban water system structure and dynamics
           across a semiarid metropolitan area
    • Authors: Yusuf Jameel; Simon Brewer, Stephen P. Good, Brett J. Tipple, James R. Ehleringer, Gabriel J. Bowen
      Pages: 5891 - 5910
      Abstract: Water extraction for anthropogenic use has become a major flux in the hydrological cycle. With increasing demand for water and challenges supplying it in the face of climate change, there is a pressing need to better understand connections between human populations, climate, water extraction, water use, and its impacts. To understand these connections, we collected and analyzed stable isotopic ratios of more than 800 urban tap water samples in a series of semiannual water surveys (spring and fall, 2013–2015) across the Salt Lake Valley (SLV) of northern Utah. Consistent with previous work, we found that mean tap water had a lower 2H and 18O concentration than local precipitation, highlighting the importance of nearby montane winter precipitation as source water for the region. However, we observed strong and structured spatiotemporal variation in tap water isotopic compositions across the region which we attribute to complex distribution systems, varying water management practices and multiple sources used across the valley. Water from different sources was not used uniformly throughout the area and we identified significant correlation between water source and demographic parameters including population and income. Isotopic mass balance indicated significant interannual and intra‐annual variability in water losses within the distribution network due to evaporation from surface water resources supplying the SLV. Our results demonstrate the effectiveness of isotopes as an indicator of water management strategies and climate impacts within regional urban water systems, with potential utility for monitoring, regulation, forensic, and a range of water resource research.
      PubDate: 2016-08-06T02:59:22.30577-05:0
      DOI: 10.1002/2016WR019104
  • Aquifer heterogeneity controls on adverse human health effects and the
           concept of the hazard attenuation factor
    • Authors: F. P. J. de Barros; A. Bellin, V. Cvetkovic, G. Dagan, A. Fiori
      Pages: 5911 - 5922
      Abstract: We analyze the probability distribution of the hazard attenuation factor for a noncarcinogenic reactive compound captured by a well in heterogeneous porous formations. The hazard attenuation factor is defined as the ratio between the hazard index HI at a detection well and at the source. Heterogeneity of the aquifer is represented through the multi‐indicator model (a collection of blocks of independent permeability) while flow and transport are solved by the means of the self‐consistent approach that is able to deal with any degree of heterogeneity. Due to formation heterogeneity, HI is a random variable and similar for hazard attenuation index. The latter can be fully characterized by its cumulative distribution function (CDF), which in turn can be related to the statistics of the travel time of solute particles, from the source to the detection well. The approach is applied to the case of a solute which undergoes decay and a well with a screen much smaller than the correlation scale of hydraulic conductivity. The results show that the probability of exceeding a given acceptable threshold of the hazard index is significantly affected by the level of heterogeneity comparable to the one observed for the MADE site, and the distance between the source and the well.
      PubDate: 2016-08-06T05:16:07.561543-05:
      DOI: 10.1002/2016WR018933
  • Large earthquakes create vertical permeability by breaching aquitards
    • Authors: Chi‐Yuen Wang; Xin Liao, Lee‐Ping Wang, Chung‐Ho Wang, Michael Manga
      Pages: 5923 - 5937
      Abstract: Hydrologic responses to earthquakes and their mechanisms have been widely studied. Some responses have been attributed to increases in the vertical permeability. However, basic questions remain: How do increases in the vertical permeability occur? How frequently do they occur? Is there a quantitative measure for detecting the occurrence of aquitard breaching? We try to answer these questions by examining data from a dense network of ∼50 monitoring stations of clustered wells in a sedimentary basin near the epicenter of the 1999 M7.6 Chi‐Chi earthquake in western Taiwan. While most stations show evidence that confined aquifers remained confined after the earthquake, about 10% of the stations show evidence of coseismic breaching of aquitards, creating vertical permeability as high as that of aquifers. The water levels in wells without evidence of coseismic breaching of aquitards show tidal responses similar to that of a confined aquifer before and after the earthquake. Those wells with evidence of coseismic breaching of aquitards, on the other hand, show distinctly different postseismic tidal response. Furthermore, the postseismic tidal response of different aquifers became strikingly similar, suggesting that the aquifers became hydraulically connected and the connection was maintained many months thereafter. Breaching of aquitards by large earthquakes has significant implications for a number of societal issues such as the safety of water resources, the security of underground waste repositories, and the production of oil and gas. The method demonstrated here may be used for detecting the occurrence of aquitard breaching by large earthquakes in other seismically active areas.
      PubDate: 2016-08-06T02:59:09.943446-05:
      DOI: 10.1002/2016WR018893
  • Does resolution of flow field observation influence apparent habitat use
           and energy expenditure in juvenile coho salmon?
    • Authors: Desirée Tullos; Cara Walter, Jason Dunham
      Pages: 5938 - 5950
      Abstract: This study investigated how the resolution of observation influences interpretation of how fish, juvenile Coho Salmon (Oncorhynchus kisutch), exploit the hydraulic environment in streams. Our objectives were to evaluate how spatial resolution of the flow field observation influenced: (1) the velocities considered to be representative of habitat units; (2) patterns of use of the hydraulic environment by fish; and (3) estimates of energy expenditure. We addressed these objectives using observations within a 1:1 scale physical model of a full‐channel log jam in an outdoor experimental stream. Velocities were measured with Acoustic Doppler Velocimetry at a 10 cm grid spacing, whereas fish locations and tailbeat frequencies were documented over time using underwater videogrammetry. Results highlighted that resolution of observation did impact perceived habitat use and energy expenditure, as did the location of measurement within habitat units and the use of averaging to summarize velocities within a habitat unit. In this experiment, the range of velocities and energy expenditure estimates increased with coarsening resolution (grid spacing from 10 to 100 cm), reducing the likelihood of measuring the velocities locally experienced by fish. In addition, the coarser resolutions contributed to fish appearing to select velocities that were higher than what was measured at finer resolutions. These findings indicate the need for careful attention to and communication of resolution of observation in investigating the hydraulic environment and in determining the habitat needs and bioenergetics of aquatic biota.
      PubDate: 2016-08-08T08:05:38.775217-05:
      DOI: 10.1002/2015WR018501
  • Analysis of reach‐scale elevation distribution in braided rivers:
           Definition of a new morphologic indicator and estimation of mean
    • Authors: M. Redolfi; M. Tubino, W. Bertoldi, J. Brasington
      Pages: 5951 - 5970
      Abstract: Understanding the role of external controls on the morphology of braided rivers is currently limited by the dearth of robust metrics to quantify and distinguish the diversity of channel form. Most existing measures are strongly dependent on river stage and unable to account for the three‐dimensional complexity that is apparent in digital terrain models of braided rivers. In this paper, we introduce a simple, stage‐independent morphological indicator that enables the analysis of reach‐scale regime morphology as a function of slope, discharge, sediment size, and degree of confinement. The index is derived from the bed elevation frequency distribution and characterizes a statistical width‐depth curve averaged longitudinally over multiple channel widths. In this way, we define a “synthetic channel” described by a simple parameter that embeds information about the river morphological complexity. Under the assumption of uniform flow, this approach can be extended to provide estimates of the reach‐averaged shear stress distribution, bed load flux, and at‐a‐station‐variability of wetted width. We test this approach using data from a wide range of labile channels including 58 flume experiments and three gravel bed braided rivers. Results demonstrate a strong relationship between the unit discharge and the shape of the elevation distribution, which varies between a U shape for typical single‐thread confined channels and a Y shape for multithread reaches. Finally, we discuss the use of the metric as a diagnostic index of river condition that may be used to support inferences about the river morphological trajectory.
      PubDate: 2016-08-10T08:02:57.079298-05:
      DOI: 10.1002/2015WR017918
  • An adaptive Gaussian process‐based method for efficient Bayesian
           experimental design in groundwater contaminant source identification
    • Authors: Jiangjiang Zhang; Weixuan Li, Lingzao Zeng, Laosheng Wu
      Pages: 5971 - 5984
      Abstract: Surrogate models are commonly used in Bayesian approaches such as Markov Chain Monte Carlo (MCMC) to avoid repetitive CPU‐demanding model evaluations. However, the approximation error of a surrogate may lead to biased estimation of the posterior distribution. This bias can be corrected by constructing a very accurate surrogate or implementing MCMC in a two‐stage manner. Since the two‐stage MCMC requires extra original model evaluations after surrogate evaluations, the computational cost is still high. If the information of measurement is incorporated, a locally accurate surrogate can be adaptively constructed with low computational cost. Based on this idea, we integrate Gaussian process (GP) and MCMC to adaptively construct locally accurate surrogates for Bayesian experimental design in groundwater contaminant source identification problems. Moreover, the uncertainty estimate of GP approximation error is incorporated in the Bayesian formula to avoid over‐confident estimation of the posterior distribution. The proposed approach is tested with a numerical case study. Without sacrificing the estimation accuracy, the new approach achieves about 200 times of speed‐up compared to our previous work which implemented MCMC in a two‐stage manner.
      PubDate: 2016-08-10T08:02:17.35949-05:0
      DOI: 10.1002/2016WR018598
  • Practices and perceptions on water resource sustainability in ecovillages
    • Authors: Flavia Brunale Vilela de Moura Leite; Lídia Sanches Bertolo, Rozely Ferreira Santos
      Pages: 6004 - 6017
      Abstract: In many areas of the world, groups of people have attempted to create urban landscapes that follow the principles of environmental sustainability. To this end, groups have devised alternative models, such as ecovillages, where low‐impact handling is used and a way of life different from that of large population centers is adopted. Although these villages exist, their efficiency in the conservation of natural resources has not been effectively evaluated. This study evaluated the practices used by two Brazilian ecovillages to conserve water resources to assess whether this new concept of living is indeed successful in meeting sustainability goals. We selected 25 indicators of water sustainability, and using the compromise programming method, we quantified the distance between those landscapes self‐referenced as sustainable and an ideal hypothetical scenario. We also interpreted the communities perceptions using the distance between the current situations and the envisioned scenario. We concluded that both ecovillage are far from technically ideal scenario, but the communities have a strong sense of their limitations in implementing water resources conservation. The communities attributed this fact primarily to deficiencies in the shared management.
      PubDate: 2016-08-11T02:06:29.62161-05:0
      DOI: 10.1002/2015WR018117
  • Integrated surface/subsurface permafrost thermal hydrology: Model
           formulation and proof‐of‐concept simulations
    • Authors: Scott L. Painter; Ethan T. Coon, Adam L. Atchley, Markus Berndt, Rao Garimella, J. David Moulton, Daniil Svyatskiy, Cathy J. Wilson
      Pages: 6062 - 6077
      Abstract: The need to understand potential climate impacts and feedbacks in Arctic regions has prompted recent interest in modeling of permafrost dynamics in a warming climate. A new fine‐scale integrated surface/subsurface thermal hydrology modeling capability is described and demonstrated in proof‐of‐concept simulations. The new modeling capability combines a surface energy balance model with recently developed three‐dimensional subsurface thermal hydrology models and new models for nonisothermal surface water flows and snow distribution in the microtopography. Surface water flows are modeled using the diffusion wave equation extended to include energy transport and phase change of ponded water. Variation of snow depth in the microtopography, physically the result of wind scour, is modeled phenomenologically with a diffusion wave equation. The multiple surface and subsurface processes are implemented by leveraging highly parallel community software. Fully integrated thermal hydrology simulations on the tilted open book catchment, an important test case for integrated surface/subsurface flow modeling, are presented. Fine‐scale 100 year projections of the integrated permafrost thermal hydrological system on an ice wedge polygon at Barrow Alaska in a warming climate are also presented. These simulations demonstrate the feasibility of microtopography‐resolving, process‐rich simulations as a tool to help understand possible future evolution of the carbon‐rich Arctic tundra in a warming climate.
      PubDate: 2016-08-11T02:07:07.395375-05:
      DOI: 10.1002/2015WR018427
  • Using practical and social information to influence flood adaptation
    • Authors: Maura C. Allaire
      Pages: 6078 - 6093
      Abstract: As the prospect for more frequent and severe extreme weather events gains scientific support, many nations are evaluating mitigation and adaptation options. Insurance and home retrofits could reduce household welfare losses due to flood events. Yet even after disasters, households often fail to take risk mitigation actions. This paper presents the first randomized field experiment that tests the effect of information provision on household uptake of flood insurance and home retrofits. A sample of 364 flood‐prone households in Bangkok was randomly split into treatment and control groups. The treatment group received practical details on home retrofits and flood insurance as well as social information regarding the insurance purchase decisions of peers. Results indicate that the information intervention increased insurance purchases by about five percentage points, while no effect was detected for home retrofits. This effect is nearly equal to the increase in uptake that the national insurance program in Thailand has achieved through all other means since its establishment in 2012. If scaled up to include all uninsured, flood‐prone households in Bangkok, nearly 70,000 additional households could be insured. The results suggest that well‐designed information interventions could increase uptake of flood insurance, without additional premium subsidies or mandates.
      PubDate: 2016-08-11T02:06:13.737754-05:
      DOI: 10.1002/2015WR018258
  • Characterization of non‐Gaussian conductivities and porosities with
           hydraulic heads, solute concentrations, and water temperatures
    • Authors: Teng Xu; J. Jaime Gómez‐Hernández
      Pages: 6111 - 6136
      Abstract: Reliable characterization of hydraulic parameters is important for the understanding of groundwater flow and solute transport. The normal‐score ensemble Kalman filter (NS‐EnKF) has proven to be an effective inverse method for the characterization of non‐Gaussian hydraulic conductivities by assimilating transient piezometric head data, or solute concentration data. Groundwater temperature, an easily captured state variable, has not drawn much attention as an additional state variable useful for the characterization of aquifer parameters. In this work, we jointly estimate non‐Gaussian aquifer parameters (hydraulic conductivities and porosities) by assimilating three kinds of state variables (piezometric head, solute concentration, and groundwater temperature) using the NS‐EnKF. A synthetic example including seven tests is designed, and used to evaluate the ability to characterize hydraulic conductivity and porosity in a non‐Gaussian setting by assimilating different numbers and types of state variables. The results show that characterization of aquifer parameters can be improved by assimilating groundwater temperature data and that the main patters of the non‐Gaussian reference fields can be retrieved with more accuracy and higher precision if multiple state variables are assimilated.
      PubDate: 2016-08-11T02:08:20.239505-05:
      DOI: 10.1002/2016WR019011
  • Comment on “Climate and agricultural land use change impacts on
           streamflow in the upper midwestern United States” by Satish C. Gupta et
    • Authors: Shawn Schottler; Jason Ulrich, Daniel Engstrom
      Pages: 6691 - 6698
      Abstract: We challenge the assertions of the study by Gupta et al. (doi:10.1002/2015WR017323) that land use, land cover change (LULC) has had minimal or no effect on hydrology in Minnesota's rivers. Statistical analyses actually demonstrate that something other than changes in precipitation (and soil moisture) must be contributing to increases in runoff ratio and flow. The analysis presented by Gupta et al. (doi:10.1002/2015WR017323) fails to directly address the fundamental purpose and mechanism of artificial drainage, which is to reduce water residence time on the landscape, thereby reducing ET (and soil wetness) and routing this water to rivers instead.
      PubDate: 2016-08-05T07:50:38.389896-05:
      DOI: 10.1002/2015WR018497
  • Reply to comment by Schottler et al. on “Climate and agricultural land
    • Authors: Satish C. Gupta; Andrew C. Kessler, Melinda K. Brown, William M. Schuh
      Pages: 6699 - 6705
      Abstract: In their comments, Schottler et al. (doi:10.1002/2015WR018482) raised concerns about our technique for deciphering climate and land use land cover (LULC) change impacts on streamflow in the upper Midwestern United States. In this reply, we further explain the underpinnings of our statistical technique and point out criticism on the procedures that Schottler et al. (doi:10.1002/2015WR018482; doi:10.1002/hyp.9738) used in their comment.
      PubDate: 2016-08-05T08:21:26.515883-05:
      DOI: 10.1002/2016WR018827
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