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  Subjects -> WATER RESOURCES (Total: 147 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: 8)
Advances in Water Resource and Protection     Open Access   (Followers: 6)
Advances in Water Resources     Hybrid Journal   (Followers: 29)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 12)
Agricultural Water Management     Hybrid Journal   (Followers: 26)
American Journal of Water Resources     Open Access   (Followers: 3)
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: 9)
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: 33)
Aquatic Geochemistry     Hybrid Journal   (Followers: 1)
Aquatic Living Resources     Hybrid Journal   (Followers: 10)
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: 19)
Civil and Environmental Research     Open Access   (Followers: 16)
CLEAN - Soil, Air, Water     Hybrid Journal   (Followers: 17)
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: 8)
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: 1)
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: 15)
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  
Ingeniería del agua     Open Access  
International Journal of Climatology     Hybrid Journal   (Followers: 23)
International Journal of Hydrology Science and Technology     Hybrid Journal   (Followers: 4)
International Journal of Nuclear Desalination     Hybrid Journal  
International Journal of River Basin Management     Hybrid Journal   (Followers: 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: 29)
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: 34)
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: 39)
Journal of Water Reuse and Desalination     Partially Free   (Followers: 6)
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: 20)
Marine Ecosystem Stressor Response     Open Access  
Methods in Oceanography : An International Journal     Hybrid Journal   (Followers: 2)
New Zealand Journal of Marine and Freshwater Research     Hybrid Journal   (Followers: 6)
Open Journal of Modern Hydrology     Open Access   (Followers: 3)
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: 5)
River Research and Applications     Hybrid Journal   (Followers: 14)
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: 13)
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: 47)
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: 25)
Water Resources Research     Full-text available via subscription   (Followers: 67)
Water SA     Open Access  
Water Science & Technology     Partially Free   (Followers: 22)
Water Science : The National Water Research Center Journal     Open Access   (Followers: 5)
Water Science and Engineering     Open Access   (Followers: 6)
Water Science and Technology : Water Supply     Partially Free   (Followers: 20)
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: 1)

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Journal Cover Water Resources Research
  [SJR: 2.189]   [H-I: 121]   [67 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 0043-1397 - ISSN (Online) 1944-7973
   Published by AGU Homepage  [17 journals]
  • A computationally efficient parallel Levenberg‐Marquardt algorithm
           for highly parameterized inverse model analyses
    • Authors: Youzuo Lin; Daniel O'Malley, Velimir V. Vesselinov
      Abstract: Inverse modeling seeks model parameters given a set of observations. However, for practical problems because the number of measurements is often large and the model parameters are also numerous, conventional methods for inverse modeling can be computationally expensive. We have developed a new, computationally‐efficient parallel Levenberg‐Marquardt method for solving inverse modeling problems with a highly parameterized model space. Levenberg‐Marquardt methods require the solution of a linear system of equations which can be prohibitively expensive to compute for moderate to large‐scale problems. Our novel method projects the original linear problem down to a Krylov subspace, such that the dimensionality of the problem can be significantly reduced. Furthermore, we store the Krylov subspace computed when using the first damping parameter and recycle the subspace for the subsequent damping parameters. The efficiency of our new inverse modeling algorithm is significantly improved using these computational techniques. We apply this new inverse modeling method to invert for random transmissivity fields in 2D and a random hydraulic conductivity field in 3D. Our algorithm is fast enough to solve for the distributed model parameters (transmissivity) in the model domain. The algorithm is coded in Julia and implemented in the MADS computational framework (http://mads.lanl.gov). By comparing with Levenberg‐Marquardt methods using standard linear inversion techniques such as QR or SVD methods, our Levenberg‐Marquardt method yields a speed‐up ratio on the order of ∼101 to ∼102 in a multi‐core computational environment. Therefore, our new inverse modeling method is a powerful tool for characterizing subsurface heterogeneity for moderate‐ to large‐scale problems. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-19T09:30:20.488029-05:
      DOI: 10.1002/2016WR019028
       
  • A bottom‐up approach to identifying the maximum operational adaptive
           capacity of water resource systems to a changing climate
    • Authors: S. Culley; S. Noble, A. Yates, M. Timbs, S. Westra, H.R. Maier, M. Giuliani, A. Castelletti
      Abstract: Many water resource systems have been designed assuming that the statistical characteristics of future inflows are similar to those of the historical record. This assumption is no longer valid due to large‐scale changes in the global climate, potentially causing declines in water resource system performance, or even complete system failure. Upgrading system infrastructure to cope with climate change can require substantial financial outlay, so it might be preferable to optimize existing system performance when possible. This paper builds on decision scaling theory by proposing a bottom‐up approach to designing optimal feedback control policies for a water system exposed to a changing climate. This approach not only describes optimal operational policies for a range of potential climatic changes, but also enables an assessment of a system's upper limit of its operational adaptive capacity, beyond which upgrades to infrastructure become unavoidable. The approach is illustrated using the Lake Como system in Northern Italy—a regulated system with a complex relationship between climate and system performance. By optimizing system operation under different hydrometeorological states, it is shown that the system can continue to meet its minimum performance requirements for more than three times as many states as it can under current operations. Importantly, a single management policy, no matter how robust, cannot fully utilize existing infrastructure as effectively as an ensemble of flexible management policies that are updated as the climate changes. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-18T06:16:22.383666-05:
      DOI: 10.1002/2015WR018253
       
  • Regionalization of land‐use impacts on streamflow using a network of
           paired catchments
    • Abstract: Quantifying the impact of land use and cover (LUC) change on catchment hydrological response is essential for land‐use planning and management. Yet hydrologists are often not able to present consistent and reliable evidence to support such decision‐making. The issue tends to be twofold: a scarcity of relevant observations, and the difficulty of regionalizing any existing observations. This study explores the potential of a paired catchment monitoring network to provide statistically robust, regionalized predictions of LUC change impact in an environment of high hydrological variability. We test the importance of LUC variables to explain hydrological responses and to improve regionalized predictions using 24 catchments distributed along the Tropical Andes. For this, we calculate first 50 physical catchment properties, and then select a subset based on correlation analysis. The reduced set is subsequently used to regionalize a selection of hydrological indices using multiple linear regression. Contrary to earlier studies, we find that incorporating LUC variables in the regional model structures increases significantly regression performance and predictive capacity for 66% of the indices. For the runoff ratio, baseflow index, and slope of the flow duration curve, the mean absolute error reduces by 53% and the variance of the residuals by 79%, on average. We attribute the explanatory capacity of LUC in the regional model to the pairwise monitoring setup, which increases the contrast of the land‐use signal in the dataset. As such, it may be a useful strategy to optimize data collection to support watershed management practices and improve decision‐making in data‐scarce regions. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-18T06:16:10.721249-05:
      DOI: 10.1002/2016WR018596
       
  • Impacts of three‐dimensional nonuniform flow on quantification of
           groundwater‐surface water interactions using heat as a tracer
    • Authors: Jonathan Reeves; Christine E. Hatch
      Abstract: Use of heat‐as‐a‐tracer is a common method to quantify surface water‐groundwater interactions (SW‐GW). However, the method relies on assumptions likely violated in natural systems. Numerical studies have explored violation of fundamental assumptions such as heterogeneous streambed properties, two‐dimensional groundwater flow fields and uncertainty in thermal parameters for the 1D heat‐as‐a‐tracer method. Few studies to date have modeled complex, fully three‐dimensional groundwater flows to address the impacts of non‐uniform, 3D flow vectors on use of heat‐as‐a‐tracer to quantify SW‐GW interactions. COMSOL Multiphysics was used to model scenarios in a fully three‐dimensional flow field in homogeneous, isotropic sand with a sinusoidal temperature upper boundary where vertical flows are deliberately disrupted by large and varied horizontal flows from two directions. Resulting temperature time series from multiple depths were used to estimate vertical Darcy flux and compared with modeled fluxes to assess the performance of the 1D thermal methods to quantify multi‐dimensional groundwater flows. In addition, apparent effective thermal diffusivity was calculated from synthetic temperature time series, and compared to model input diffusivity. Both increasingly non‐uniform and non‐vertical groundwater flow fields resulted in increasing errors for both the temperature‐derived flux and temperature‐derived effective thermal diffusivity. For losing (downward) flow geometries, errors in temperature‐derived effective thermal diffusivity were highly correlated with errors in temperature‐derived flux and were used to identify how and when underlying assumptions necessary for heat‐as‐a‐tracer for quantifying groundwater flows were violated. Specifically, non‐uniform flow fields (with flow lines that converge or diverge) produced the largest errors in simulated fluxes. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-17T03:30:31.521128-05:
      DOI: 10.1002/2016WR018841
       
  • 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
           filtering
    • 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
       
  • Reply to comments by Belmont et al. on “Climate and agricultural
           land use change impacts on streamflow in the upper midwestern United
           States”
    • Authors: Satish C. Gupta; Andrew C. Kessler, Melinda K. Brown, William M. Schuh
      Abstract: The reply addresses concerns raised by Belmont et al. [2016] on Gupta et al. [2015] through additional analysis of streamflow vs. precipitation relationships for the Whetstone and the Redwood Rivers and with data on available soil moisture in prechange and postchange periods in the Cottonwood River watershed. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-16T11:40:41.968117-05:
      DOI: 10.1002/2016WR018926
       
  • 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
           catchment
    • 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
       
  • Comment on “Climate and agricultural land use change impacts on
           streamflow in the upper midwestern United States” by Satish C. Gupta
           et al.
    • Authors: Patrick Belmont; John R. Stevens, Jonathan A. Czuba, Karthik Kumarasamy, Sara A. Kelly
      Abstract: The paper “Climate and agricultural land use change impacts on streamflow in the upper midwestern United States” by Satish C. Gupta, Andrew C. Kessler, Melinda K. Brown, and Francis Zvomuya (hereafter referred to as Gupta et al.) purports to evaluate “the relative importance of changes in precipitation and LULC (land use, land cover) on streamflow in 29 Hydrologic Unit Code 008 watersheds in the Upper Midwestern United States.” However, as we report here, the approach used by Gupta et al. is wholly inadequate for making such an evaluation. Gupta et al. use strong language to criticize other studies and imply a level of certainty that goes well beyond, and in some cases is entirely unsupported by, the results they have presented. We take this opportunity to point out several critical flaws in their study. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-16T11:40:29.739431-05:
      DOI: 10.1002/2015WR018476
       
  • Water flow and multicomponent solute transport in drip irrigated
           lysimeters
    • 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
    • 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
    • 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 fuzzy Bayesian approach to flood frequency estimation with imprecise
           historical information
    • Abstract: This paper presents a novel framework that links imprecision (through a fuzzy approach) and stochastic uncertainty (through a Bayesian approach) in estimating flood probabilities from historical flood information and systematic flood discharge data. The method exploits the linguistic characteristics of historical source material to construct membership functions, which may be wider or narrower, depending on the vagueness of the statements. The membership functions are either included in the prior distribution or the likelihood function to obtain a fuzzy version of the flood frequency curve. The viability of the approach is demonstrated by three case studies that differ in terms of their hydromorphological conditions (from an Alpine river with bedrock profile to a flat lowland river with extensive flood plains) and historical source material (including narratives, town and county meeting protocols, flood marks and damage accounts). The case studies are presented in order of increasing fuzziness (the Rhine at Basel, Switzerland; the Werra at Meiningen, Germany; and the Tisza at Szeged, Hungary). Incorporating imprecise historical information is found to reduce the range between the 5% and 95% Bayesian credibility bounds of the 100yr floods by 45% and 61% for the Rhine and Werra case studies, respectively. The strengths and limitations of the framework are discussed relative to alternative (non‐fuzzy) methods. The fuzzy Bayesian inference framework provides a flexible methodology that fits the imprecise nature of linguistic information on historical floods as available in historical written documentation. This article is protected by copyright. All rights reserved.
      PubDate: 2016-08-05T03:25:41.379796-05:
      DOI: 10.1002/2016WR019177
       
  • 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
           sensing
    • 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
           bend
    • 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
    • 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
    • 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
       
  • Practices and perceptions on water resource sustainability in ecovillages
    • 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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-27T05:55:29.750395-05:
      DOI: 10.1002/2015WR018117
       
  • Characterization of non‐Gaussian conductivities and porosities with
           hydraulic heads, solute concentrations, and water temperatures
    • 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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-25T18:05:41.253742-05:
      DOI: 10.1002/2016WR019011
       
  • Conceptualizing sociohydrological drought processes: The case of the Maya
           collapse
    • 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
    • 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
       
  • 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
      Abstract: We analyze the probability distribution of the hazard attenuation factor for a non‐carcinogenic 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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-18T03:40:34.57679-05:0
      DOI: 10.1002/2016WR018933
       
  • An adaptive Gaussian process‐based method for efficient Bayesian
           experimental design in groundwater contaminant source identification
           problems
    • Authors: Jiangjiang Zhang; Weixuan Li, Lingzao Zeng, Laosheng Wu
      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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-18T03:40:31.326595-05:
      DOI: 10.1002/2016WR018598
       
  • Large earthquakes create vertical permeability by breaching aquitards
    • 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 post‐seismic tidal response. Furthermore, the post‐seismic 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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-18T03:40:26.025618-05:
      DOI: 10.1002/2016WR018893
       
  • 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
       
  • Using practical and social information to influence flood adaptation
           behavior
    • Authors: Maura C. Allaire
      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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-15T04:16:37.280565-05:
      DOI: 10.1002/2015WR018258
       
  • Integrated surface/subsurface permafrost thermal hydrology: Model
           formulation and proof‐of‐concept simulations
    • Authors: Scott L. Painter; Ethan T. Coon, Adam Atchley, Markus Berndt, Rao Garimella, David Moulton, Daniil Svyatskiy, Cathy J. Wilson
      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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-15T04:16:10.265394-05:
      DOI: 10.1002/2015WR018427
       
  • 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
           imbibition
    • 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
       
  • 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
      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 to 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 inter‐ 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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-14T09:10:31.961417-05:
      DOI: 10.1002/2016WR019104
       
  • 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
       
  • Change in streamflow response in unregulated catchments in Sweden over the
           last century
    • 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. 1D 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 non‐stationarity of parameters that result from temporal change caused by land use change and/or climate change that is due to anthropogenic or natural causes. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-05T04:25:34.306344-05:
      DOI: 10.1002/2015WR018116
       
  • Impact of topography on groundwater salinization due to ocean surge
           inundation
    • Authors: Xuan Yu; Jie Yang, Thomas Graf, Mohammad Koneshloo, Michael A. O'Neal, Holly A. Michael
      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 3D 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 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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-05T04:25:31.025333-05:
      DOI: 10.1002/2016WR018814
       
  • Hydrograph variances over different timescales in hydropower production
           networks
    • 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: 2016-07-05T04:25:25.106557-05:
      DOI: 10.1002/2015WR017775
       
  • Does resolution of flow field observation influence apparent habitat use
           and energy expenditure in juvenile coho salmon?
    • 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, 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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-05T04:25:23.873775-05:
      DOI: 10.1002/2015WR018501
       
  • Comment on “Advective transport in heterogeneous aquifers: Are proxy
           models predictive?” by A. Fiori, A. Zarlenga, H. Gotovac, I.
           Jankovic, E.Volpi, V.Cvetkovic, and G. Dagan
    • Authors: Shlomo P. Neuman
      Abstract: Fiori et al. [2015] examine the predictive capabilities of (among others) two “proxy” non‐Fickian transport models, MRMT (Multi‐RateMassTransfer) and CTRW (Continuous‐Time Random Walk). In particular, they compare proxy model predictions of mean breakthrough curves (BTCs) at a sequence of control planes with near‐ergodic BTCs generated through two‐ and three‐dimensional simulations of nonreactive, mean‐uniform advective transport in single realizations of stationary, randomly heterogeneous porous media. The authors find fitted proxy model parameters to be nonunique and devoid of clear physical meaning. This notwithstanding, they conclude optimistically that “i. Fitting the proxy models to match the BTC at [one control plane] automatically ensures prediction at downstream control planes [and thus] ii. … the measured BTC can be used directly for prediction, with no need to use models underlain by fitting.” I show that (a) the authors' findings follow directly from (and thus confirm) theoretical considerations discussed earlier by Neuman and Tartakovsky [2009], which (b) additionally demonstrate that proxy models will lack similar predictive capabilities under more realistic, non‐Markovian flow and transport conditions that prevail under flow through nonstationary (e.g. multiscale) media in the presence of boundaries and/or nonuniformly distributed sources, and/or when flow/transport are conditioned on measurements. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-04T18:45:29.884988-05:
      DOI: 10.1002/2016WR019093
       
  • Reply to the comment by S.P. Neuman on “Advective transport in
           heterogeneous aquifers: Are proxy models predictive?”by A.
           Fiori, A. Zarlenga, H. Gotovac, I. Jankovic, E.Volpi, V.Cvetkovic, and G.
           Dagan
    • Authors: Aldo Fiori; Antonio Zarlenga, Hrvoje Gotovac, Hrvoje Gotovac, Hrvoje Gotovac, Vladimir Cvetkovic, Gedeon Dagan
      PubDate: 2016-07-04T18:45:27.611851-05:
      DOI: 10.1002/2016WR019209
       
  • A copula‐based nonstationary frequency analysis for the
           2012‐2015 drought in California
    • Abstract: Using a multi‐century reconstruction of drought, we investigate how rare the 2012‐2015 California drought is. A Bayesian approach to a nonstationary, bivariate probabilistic model, including the estimation of Copula parameters is used to assess the time varying return period of the current drought. Both the duration and severity of drought exhibit similar multi‐century trends. The period from 800‐1200 AD was perhaps more similar to the recent period than the period from 1200 to 1800 AD. The median return period of the recent drought accounting for both duration and severity, varies from approximately 667 to 2652 years, if the model parameters from the different time periods are considered. However, we find that the recent California drought is of unprecedented severity, especially given the relatively modest duration of the drought. The return period of the severity of the recent drought given its 4‐year duration is estimated to be nearly 21,000 years. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-04T18:45:24.798036-05:
      DOI: 10.1002/2016WR018959
       
  • Minimizing the effects of filtering on catchment scale GRACE solutions
    • Authors: Bramha Dutt Vishwakarma; Balaji Devaraju, Nico Sneeuw
      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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-04T10:40:30.819732-05:
      DOI: 10.1002/2016WR018960
       
  • A comparison of regional flood frequency analysis approaches in a
           simulation framework
    • Authors: D. Ganora; F. Laio
      Abstract: Regional frequency analysis (RFA) is a well‐established methodology to provide an estimate of the flood frequency curve at ungauged (or scarcely gauged) sites. Different RFA approaches exist, depending on the way the information is transferred to the site of interest, but it is not clear in the literature if a specific method systematically outperforms the others. The aim of this study is to provide a framework wherein carrying out the intercomparison by building up a virtual environment based on synthetically generated data. The considered regional approaches include: (i) a unique regional curve for the whole region; (ii) a multiple‐region model where homogeneous subregions are determined through cluster analysis; (iii) a Region‐of‐Influence model which defines a homogeneous subregion for each site; (iv) a spatially‐smooth estimation procedure where the parameters of the regional model vary continuously along the space. Virtual environments are generated considering different patterns of heterogeneity, including step change and smooth variations. If the region is heterogeneous, with the parent distribution changing continuously within the region, the spatially‐smooth regional approach outperforms the others, with overall errors 10%‐50% lower than the other methods. In the case of a step‐change, the spatially‐smooth and clustering procedures perform similarly if the heterogeneity is moderate, while clustering procedures work better when the step‐change is severe. To extend our findings, an extensive sensitivity analysis has been performed to investigate the effect of sample length, number of virtual stations, return period of the predicted quantile, variability of the scale parameter of the parent distribution, number of predictor variables and different parent distribution. Overall, the spatially‐smooth approach appears as the most robust approach as its performances are more stable across different patterns of heterogeneity, especially when short records are considered. This article is protected by copyright. All rights reserved.
      PubDate: 2016-07-01T03:25:54.796162-05:
      DOI: 10.1002/2016WR018604
       
  • Mean age distribution of inorganic soil‐nitrogen
    • Authors: Dong K. Woo; Praveen Kumar
      Abstract: Excess reactive nitrogen in soils of intensively managed landscapes causes adverse environmental impact, and continues to remain a global concern. Many novel strategies have been developed to provide better management practices and, yet, the problem remains unresolved. The objective of this study is to develop a model to characterize the “age” of inorganic soil‐nitrogen (nitrate, and ammonia/ammonium). We use the general theory of age, which provides an assessment of the time elapsed since inorganic nitrogen has been introduced into the soil system. We analyze a corn‐corn‐soybean rotation, common in the Midwest United States, as an example application. We observe two counter‐intuitive results: (1) the mean nitrogen age in the topsoil layer is relatively high; and (2) mean nitrogen age is lower under soybean cultivation compared to corn although no fertilizer is applied for soybean cultivation. The first result can be explained by cation‐exchange of ammonium that retards the leaching of nitrogen, resulting in an increase in the mean nitrogen age near the soil surface. The second result arises because the soybean utilizes the nitrogen fertilizer left from the previous year, thereby removing the older nitrogen and reducing mean nitrogen age. Estimating the mean nitrogen age can thus serve as an important tool to disentangle complex nitrogen dynamics by providing a nuanced characterization of the time scales of soil‐nitrogen transformation and transport processes. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-29T10:56:18.457528-05:
      DOI: 10.1002/2015WR017799
       
  • Extending theis' solution: Using transient pumping tests to estimate
           parameters of aquifer heterogeneity
    • 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
       
  • The two‐phase flow IPTT method for measurement of
           nonwetting‐wetting liquid interfacial areas at higher nonwetting
           saturations in natural porous media
    • Authors: Hua Zhong; Asma El Ouni, Dan Lin, Bingguo Wang, Mark L Brusseau
      Abstract: Interfacial areas between nonwetting‐wetting (NW‐W) liquids in natural porous media were measured using a modified version of the interfacial partitioning tracer test (IPTT) method that employed simultaneous two‐phase flow conditions, which allowed measurement at NW saturations higher than trapped residual saturation. Measurements were conducted over a range of saturations for a well‐sorted quartz sand under three wetting scenarios of primary drainage (PD), secondary imbibition (SI), and secondary drainage (SD). Limited sets of experiments were also conducted for a model glass‐bead medium and for a soil. The measured interfacial areas were compared to interfacial areas measured using the standard IPTT method for liquid‐liquid systems, which employs residual NW saturations. In addition, the theoretical maximum interfacial areas estimated from the measured data are compared to specific solid surface areas measured with the N2/BET method and estimated based on geometrical calculations for smooth spheres. Interfacial areas increase linearly with decreasing water saturation over the range of saturations employed. The maximum interfacial areas determined for the glass beads, which have no surface roughness, are 32±4 and 36±5 cm−1 for PD and SI cycles, respectively. The values are similar to the geometric specific solid surface area (31±2 cm−1) and the N2/BET solid surface area (28±2 cm−1). The maximum interfacial areas are 274±38, 235±27, and 581±160 cm−1 for the sand for PD, SI, and SD cycles, respectively, and ∼7625 cm−1 for the soil for PD and SI. The maximum interfacial areas for the sand and soil are significantly larger than the estimated smooth‐sphere specific solid surface areas (107±8 cm−1 and 152±8 cm−1, respectively), but much smaller than the N2/BET solid surface area (1387±92 cm−1 and 55224 cm−1, respectively). The NW‐W interfacial areas measured with the two‐phase flow method compare well to values measured using the standard IPTT method. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-29T03:50:58.461144-05:
      DOI: 10.1002/2016WR018783
       
  • 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
      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 non‐capillary 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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-29T03:50:54.127706-05:
      DOI: 10.1002/2016WR018866
       
  • Structural controls on anomalous transport in fractured porous rock
    • Authors: Yaniv Edery; Sebastian Geiger, Brian Berkowitz
      Abstract: Anomalous transport is ubiquitous in a wide range of disordered systems, notably in fractured porous formations. We quantitatively identify the structural controls on anomalous tracer transport in a model of a real fractured geological formation that was mapped in an outcrop. The transport, determined by a continuum scale mathematical model, is characterized by breakthrough curves (BTCs) that document anomalous (or “non‐Fickian”) transport, which is accounted for by a power‐law distribution of local transition times ψ(t) within the framework of a continuous time random walk (CTRW). We show that the determination of ψ(t) is related to fractures aligned approximately with the macroscopic direction of flow. We establish the dominant role of fracture alignment, and assess the statistics of these fractures by determining a concentration‐visitation weighted residence time histogram. We then convert the histogram to a probability density function (pdf) that coincides with the CTRW ψ(t) and hence anomalous transport. We show that the permeability of the geological formation hosting the fracture network has a limited effect on the anomalous nature of the transport; rather, it is the fractures transverse to the flow direction that play the major role in forming the long BTC tail associated with anomalous transport. This is a remarkable result, given the complexity of the flow field statistics as captured by concentration transitions. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-29T03:50:44.923388-05:
      DOI: 10.1002/2016WR018942
       
  • Multiscale pore‐network representation of heterogeneous carbonate
           rocks
    • Authors: Tannaz Pak; Ian B. Butler, Sebastian Geiger, Marinus I.J. van Dijke, Zeyun Jiang, Rodrigo Surmas
      Abstract: A multi‐scale network integration approach introduced by Jiang et al. [2013] is used to generate a representative pore‐network for a carbonate rock with a pore‐size distribution across several orders of magnitude. We predict the macroscopic flow parameters of the rock utilising i) 3D images captured by X‐ray computed micro‐tomography and ii) pore‐network flow simulations. To capture the multi‐scale pore‐size distribution of the rock we imaged four different rock samples at different resolutions and integrated the data to produce a pore‐network model that combines information at several length‐scales that cannot be recovered from a single tomographic image. A workflow for selection of the number and length‐scale of the required input networks for the network integration process, as well as fine tuning the model parameters is presented. Mercury injection capillary‐pressure data were used to evaluate independently the multi‐scale networks. We explore single‐scale, two‐scale, and three‐scale network models and discuss their representativeness by comparing simulated capillary‐pressure versus saturation curves with laboratory measurements. We demonstrate that for carbonate rocks with wide pore‐size distributions, it may be required to integrate networks extracted from two or three discrete tomographic data sets in order to simulate macroscopic flow parameters. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-27T12:21:29.295435-05:
      DOI: 10.1002/2016WR018719
       
  • Compositional data analysis as a robust tool to delineate hydrochemical
           facies within and between gas‐bearing aquifers
    • Abstract: Isometric log ratios of proportions of major ions, derived from intuitive sequential binary partitions, are used to characterise 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 behaviour 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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-27T03:45:36.854916-05:
      DOI: 10.1002/2015WR018386
       
  • On the deterministic and stochastic use of hydrologic models
    • Authors: William H. Farmer; Richard M. Vogel
      Abstract: Environmental simulation models, such as precipitation‐runoff watershed models, are increasingly used in a deterministic manner for environmental and water resources design, planning, and management. In operational hydrology, simulated responses are now routinely used to plan, design, and manage a very wide class of water resource systems. However, all such models are calibrated to existing data sets and retain some residual error. This residual, typically unknown in practice, is often ignored, implicitly trusting simulated responses as if they are deterministic quantities. In general, ignoring the residuals will result in simulated responses with distributional properties that do not mimic those of the observed responses. This discrepancy has major implications for the operational use of environmental simulation models as is shown here. Both a simple linear model and a distributed‐parameter precipitation‐runoff model are used to document the expected bias in the distributional properties of simulated responses when the residuals are ignored. The systematic reintroduction of residuals into simulated responses in a manner that produces stochastic output is shown to improve the distributional properties of the simulated responses. Every effort should be made to understand the distributional behavior of simulation residuals and to use environmental simulation models in a stochastic manner. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-27T03:45:30.024226-05:
      DOI: 10.1002/2016WR019129
       
  • Simulation of root water uptake under consideration of
           non‐equilibrium dynamics in the rhizosphere
    • Authors: Eva Kroener; Mohsen Zarebanadkouki, Marco Bittelli, Andrea Carminati
      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 non‐equilibrium 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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-27T03:40:53.199512-05:
      DOI: 10.1002/2015WR018579
       
  • Heat as a tracer for understanding transport processes in fractured media:
           theory and field assessment from multi‐scale thermal push‐pull
           tracer tests
    • Authors: Maria V. Klepikova; Tanguy Le Borgne, Olivier Bour, Marco Dentz, Rebecca Hochreutener, Nicolas Lavenant
      Abstract: The characterization and modeling of heat transfer in fractured media is particularly challenging as the existence of fractures at multiple scales induces highly localized flow patterns. From a theoretical and numerical analysis of heat transfer in simple conceptual models of fractured media, we show that flow channeling has a significant effect on the scaling of heat recovery in both space and time. The late time tailing of heat recovery under channeled flow is shown to diverge from the T(t) ∝ t−1.5 behavior expected for the classical parallel plate model and follow the scaling T(t) ∝ 1/t (log t)2 for a simple channel modeled as a tube. This scaling, which differs significantly from known scalings in mobile‐immobile systems, is of purely geometrical origin: late time heat transfer from the matrix to a channel corresponds dimensionally to a radial diffusion process, while heat transfer from the matrix to a plate may be considered as a one‐dimensional process. This phenomenon is also manifested on the spatial scaling of heat recovery as flow channeling affects the decay of the thermal breakthrough peak amplitude and the increase of the peak time with scale. These findings are supported by the results of a field experimental campaign performed on the fractured rock site of Ploemeur. The scaling of heat recovery in time and space, measured from thermal breakthrough c urves measured through a series of push‐pull tests at different scales, shows a clear signature of flow channeling. The whole data‐set can thus be successfully represented by a multi‐channel model parametrized by the mean channel density and aperture. These findings, which bring new insights on the effect of flow channeling on heat transfer in fractured rocks, show how heat recovery in geothermal tests may be controlled by fracture geometry. In addition, this highlights the interest of thermal push‐pull tests as a complement to solute tracers tests to infer fracture aperture and geometry. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-24T22:43:52.031778-05:
      DOI: 10.1002/2016WR018789
       
  • Stochastic Simulation of Soil Particle‐Size Curves in Heterogeneous
           Aquifer Systems through a Bayes space approach
    • Authors: A. Menafoglio; A. Guadagnini, P. Secchi
      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 [Menafoglio et al, 2014,2015] 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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-24T03:31:53.852377-05:
      DOI: 10.1002/2015WR018369
       
  • Instability of canopy flows
    • Authors: Giuseppe A. Zampogna; Franck Pluvinage, Azeddine Kourta, Alessandro Bottaro
      Abstract: Honami and monami waves are caused by large‐scale coherent vortex structures which form in shear layers generated by canopies. In order to reach new insights on the onset of such waves, the instability of these shear layers is studied. Two different approach are used. In the first approach the presence of the canopy is modeled via a drag coefficient, taken to vary along the canopy as by experimental indications. The second approach considers the canopy as a porous medium and different governing equations for the fluid flow are deduced. In this second case the anisotropy of the canopy, composed by rigid cylindrical elements, is accounted for via an apparent permeability tensor. The results obtained with the latter approach approximate better experimental correlations for the synchronous oscillations of the canopy. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-22T03:56:10.761586-05:
      DOI: 10.1002/2016WR018915
       
  • A new device for characterizing fracture networks and measuring
           groundwater and contaminant fluxes in fractured rock aquifers
    • Authors: Harald Klammler; Kirk Hatfield, Mark A. Newman, Jaehyun Cho, Michael D. Annable, Beth L. Parker, John A. Cherry, Irina Perminova
      Abstract: This paper presents the fundamental theory and laboratory test results on a new device that is deployed in boreholes in fractured rock aquifers to characterize vertical distributions of water and contaminant fluxes, aquifer hydraulic properties, and fracture network properties (e.g., active fracture density and orientation). The device, a fractured rock passive flux meter (FRPFM), consists of an inflatable core assembled with upper and lower packers that isolate the zone of interest from vertical gradients within the borehole. The outer layer of the core consists of an elastic fabric mesh equilibrated with a visible dye which is used to provide visual indications of active fractures and measures of fracture location, orientation, groundwater flux, and the direction of that flux. Beneath the outer layer is a permeable sorbent that is preloaded with known amounts of water soluble tracers which are eluted at rates proportional to groundwater flow. This sorbent also captures target contaminants present in intercepted groundwater. The mass of contaminant sorbed is used to quantify cumulative contaminant flux; whereas, the mass fractions of resident tracers lost are used to provide measures of water flux. In this paper, the FRPFM is bench tested over a range of fracture velocities (2‐20 m/day) using a single fracture flow apparatus (fracture aperture = 0.5 mm). Test results show a discoloration in visible dye corresponding to the location of the active fracture. The geometry of the discoloration can be used to discern fracture orientation as well as direction and magnitude of flow in the fracture. Average contaminant fluxes were measured within 16% and water fluxes within 25% of known imposed fluxes. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-22T03:56:07.222125-05:
      DOI: 10.1002/2015WR018389
       
  • Three‐dimensional numerical simulations of methane gas migration
           from decommissioned hydrocarbon production wells into shallow aquifers
    • Abstract: Three‐dimensional numerical simulations are used to provide insight into the behavior of methane as it migrates from a leaky decommissioned hydrocarbon well into a shallow aquifer. The conceptual model includes gas‐phase migration from a leaky well, dissolution into groundwater, advective‐dispersive transport and biodegradation of the dissolved methane plume. Gas‐phase migration is simulated using the DuMux multi‐phase simulator, while transport and fate of the dissolved phase is simulated using the BIONAPL/3D reactive transport model. Methane behavior is simulated for two conceptual models: first in a shallow confined aquifer containing a decommissioned leaky well based on a monitored field site near Lindbergh, Alberta, Canada, and secondly on a representative unconfined aquifer based loosely on the Borden, Ontario, field site. The simulations show that the Lindbergh site confined aquifer data are generally consistent with a 2‐year methane leak of 2 to 20 m3/d, assuming anaerobic (sulfate‐reducing) methane oxidation and with maximum oxidation rates of 1 × 10−5 to 1 × 10−3 kg/m3/d. Under the highest oxidation rate, dissolved methane decreased from solubility (110 mg/L) to the threshold concentration of 10 mg/L within 5 years. In the unconfined case with the same leakage rate, including both aerobic and anaerobic methane oxidation, the methane plume was less extensive compared to the confined aquifer scenarios. Unconfined aquifers may therefore be less vulnerable to impacts from methane leaks along decommissioned wells. At other potential leakage sites, site‐specific data on the natural background geochemistry would be necessary to make reliable predictions on the fate of methane in groundwater. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-22T03:55:47.462434-05:
      DOI: 10.1002/2016WR018686
       
  • Comparison of fluid‐fluid interfacial areas measured with
           X‐ray microtomography and interfacial partitioning tracer tests for
           the same samples
    • Authors: Kieran McDonald; Kenneth C. Carroll, Mark L. Brusseau
      Abstract: Two different methods are currently used for measuring interfacial areas between immiscible fluids within 3‐D porous media, high‐resolution microtomographic imaging and interfacial partitioning tracer tests (IPTT). Both methods were used in this study to measure non‐wetting/wetting interfacial areas for a natural sand. The microtomographic imaging was conducted on the same packed columns that were used for the IPTTs. This is in contrast to prior studies comparing the two methods, for which in all cases different samples were used for the two methods. In addition, the columns were imaged before and after the IPTTs to evaluate the potential impacts of the tracer solution on fluid configuration and attendant interfacial area. The interfacial areas measured using IPTT are ∼5 times larger than the microtomographic‐measured values, which is consistent with previous work. Analysis of the image data revealed no significant impact of the tracer solution on NAPL configuration or interfacial area. Other potential sources of error were evaluated, and all were demonstrated to be insignificant. The disparity in measured interfacial areas between the two methods is attributed to the limitation of the microtomography method to characterize interfacial area associated with microscopic surface roughness due to resolution constraints. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-22T03:51:47.316108-05:
      DOI: 10.1002/2016WR018775
       
  • Bayesian nitrate source apportionment to individual groundwater wells in
           the Central Valley by use of elemental and isotopic tracers
    • Abstract: Groundwater quality is a concern in alluvial aquifers that underlie agricultural areas, such as in the San Joaquin Valley of California. Shallow domestic wells (less than 150 m deep) in agricultural areas are often contaminated by nitrate. Agricultural and rural nitrate sources include dairy manure, synthetic fertilizers, and septic waste. Knowledge of the relative proportion that each of these sources contributes to nitrate concentration in individual wells can aid future regulatory and land management decisions. We show that nitrogen and oxygen isotopes of nitrate, boron isotopes, and iodine concentrations are a useful, novel combination of groundwater tracers to differentiate between manure, fertilizers, septic waste, and natural sources of nitrate. Furthermore, in this work, we develop a new Bayesian mixing model in which these isotopic and elemental tracers were used to estimate the probability distribution of the fractional contributions of manure, fertilizers, septic waste, and natural sources to the nitrate concentration found in an individual well. The approach was applied to 56 nitrate‐impacted private domestic wells located in the San Joaquin Valley. Model analysis found that some domestic wells were clearly dominated by the manure source and suggests evidence for majority contributions from either the septic or fertilizer source for other wells. But, predictions of fractional contributions for septic and fertilizer sources were often of similar magnitude, perhaps because modeled uncertainty about the fraction of each was large. For validation of the Bayesian model, fractional estimates were compared to surrounding landuse and estimated source contributions were broadly consistent with nearby landuse types. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-22T03:51:40.547227-05:
      DOI: 10.1002/2015WR018523
       
  • Mechanisms for trapping and mobilization of residual fluids during
           capillary‐dominated three‐phase flow in porous rock
    • Authors: J. O. Helland; E. Jettestuen
      Abstract: We use a multiphase level set approach to simulate capillary‐controlled motions of isolated fluid ganglia surrounded by two other continuous fluids (i.e., double displacements) during three‐phase flow on 3‐D porous rock geometries. Double displacements and three‐phase snap‐off mechanisms are closely related. Water snap‐off on gas/oil interfaces can initiate double displacements that mobilize isolated oil ganglia in water‐wet rock, but it can also terminate ongoing double displacements and trap oil in water. The multiphase level set approach allows for calculating the evolution of disconnected‐phase pressure during the motion. In the events of pore filling by double displacement of oil ganglia, and water snap‐off on gas/oil interfaces, we find that the local gas/oil capillary pressure drops, while local oil/water capillary pressure increases, by a similar magnitude as observed for the capillary pressure drops during single‐pore filling events in dynamic pore‐scale experiments of two‐phase drainage. We also find that oil ganglia decrease their surface area, and achieve a more compact shape, when the gas/oil interfacial area decreases at the expense of increased oil/water interfacial area during double displacement. By comparison with similar two‐phase gas/water simulations, we find that the level of the gas/water capillary pressure curves, including hysteresis loops, are smaller when a mobile, disconnected oil is present, which suggests double displacement of oil is more favorable than direct gas/water displacement. We also present cases in which phase trapping occurred in the three‐phase simulations, but not in the corresponding two‐phase simulations, supporting the view that more trapping is possible in three‐phase flow. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-22T03:51:29.819057-05:
      DOI: 10.1002/2016WR018912
       
  • 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
       
  • Transferring measured discharge time series: Large‐scale comparison
           of Top‐kriging to geomorphology‐based inverse modeling
    • Abstract: Few methods directly transfer streamflow measurements for continuous prediction of ungauged catchments. Top‐kriging has been used mainly to predict the statistical properties of runoff, but has been shown to outperform traditional regionalization approaches of rainfall‐runoff models. We applied the Top‐kriging approach across the Loire river basin and compared predictions to a geomorphology‐based approach. Whereas Top‐kriging uses spatial correlation, the other approach has the advantage of being more physically‐based by using a well‐known geomorphology‐based hydrological model (WFIUH) and its inversion. Both approaches require an equal degree of calibration and provide similar performances. We also demonstrate that the Ghosh distance, which considers the nested nature of catchments, can be used efficiently to calculate weights and to identify the suitability of gauged catchments for use as donor catchments. This result is particularly relevant for catchments with Strahler orders above five, i.e., where donor catchments are more strongly nested. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-17T18:25:37.061179-05:
      DOI: 10.1002/2016WR018716
       
  • Linking high‐frequency DOC dynamics to the age of connected water
           sources
    • Authors: C. Tunaley; D. Tetzlaff, J. Lessels, C. Soulsby
      Abstract: We combined high‐frequency dissolved organic matter fluorescence (FDOM) data with stable isotope observations to identify the sources and ages of runoff that cause temporal variability in dissolved organic carbon (DOC) within a peat‐dominated Scottish catchment. FDOM was strongly correlated (r2 ∼ 0.8) with DOC, allowing inference of a 15 minute time series. We captured 34 events over a range of hydrological conditions. Along with marked seasonality, different event responses were observed during summer depending on dry or wet antecedent conditions. The majority of events exhibited anticlockwise hysteresis as a result of the expansion of the riparian saturation zone, mobilizing previously unconnected DOC sources. Water ages from the main runoff sources were extracted from a tracer–aided hydrological model. Particularly useful were ages of overland flow, which were negatively correlated with DOC concentration. Overland flow age, which ranged between 0.2 and 360 days, reflected antecedent conditions, with younger water generally mobilizing the highest DOC concentrations in summer events. During small events with dry antecedent conditions, DOC response was proportionally higher due to the displacement and mixing of small volumes of previously unconnected highly‐concentrated riparian soil waters by new precipitation. During large events with wet antecedent conditions, the riparian saturation zone expands to organic layers on the hillslopes causing peaks in DOC. However, these peaks were limited by dilution and supply. This study highlights the utility of linking high‐frequency DOC measurements with other tracers, allowing the effects of hydrologic connectivity and antecedent conditions on delivery of DOC to streams to be assessed. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-15T04:05:29.878672-05:
      DOI: 10.1002/2015WR018419
       
  • Dual assimilation of satellite soil moisture to improve streamflow
           prediction in data‐scarce catchments
    • Abstract: This paper explores the use of active and passive microwave satellite soil moisture products for improving streamflow prediction within 4 large (>5,000km2) semi‐arid catchments in Australia. We use the probability distributed model (PDM) under a data‐scarce scenario and aim at correcting two key controlling factors in the streamflow generation: the rainfall forcing data and the catchment wetness condition. The soil moisture analysis rainfall tool (SMART) is used to correct a near‐real time satellite rainfall product (forcing correction scheme) and an ensemble Kalman filter is used to correct the PDM soil moisture state (state correction scheme). These two schemes are combined in a dual correction scheme and we assess the relative improvements of each. Our results demonstrate that the quality of the satellite rainfall product is improved by SMART during moderate‐to‐high daily rainfall events, which in turn leads to improved streamflow prediction during high flows. When employed individually, the soil moisture state correction scheme generally outperforms the rainfall correction scheme, especially for low flows. Overall, the combined dual correction scheme further improves the streamflow predictions (reduction in root mean square error and false alarm ratio, and increase in correlation coefficient and Nash‐Sutcliffe efficiency). Our results provide new evidence of the value of satellite soil moisture observations within data‐scarce regions. We also identify a number of challenges and limitations within the schemes. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-14T18:00:57.561918-05:
      DOI: 10.1002/2015WR018429
       
  • Comparative assessment of three‐phase oil relative permeability
           models
    • Authors: Ehsan Ranaee; Monica Riva, Giovanni M. Porta, Alberto Guadagnini
      Abstract: We assess the ability of eleven models to reproduce three‐phase oil relative permeability (kro) laboratory data obtained in a water‐wet sandstone sample. We do so by considering model performance when (i) solely two‐phase data are employed to render predictions of kro, and (ii) two‐ and three‐phase data are jointly used for model calibration. In the latter case a Maximum Likelihood (ML) approach is used to estimate model parameters. The tested models are selected amongst (i) classical models routinely employed in practical applications and implemented in commercial reservoir softwares and (ii) relatively recent models which are considered to allow overcoming some drawbacks of the classical formulations. Amongst others, the latter set of models includes the formulation recently proposed by Ranaee et al. [2015], which has been shown to embed the critical effects of hysteresis, including the reproduction of oil remobilization induced by gas injection in water‐wet media. We employ formal model discrimination criteria to rank models according to their skill to reproduce the observed data and use ML Bayesian Model Averaging to provide model averaged estimates (and associated uncertainty bounds) of kro by taking advantage of the diverse interpretive abilities of all models analyzed. The occurence of elliptic regions is also analyzed for selected models in the framework of the classical fractional flow theory of displacement. Our study confirms that model outcomes based on channel flow theory and classical saturation‐weighted interpolation models do not generally yield accurate reproduction of kro data, especially in the regime associated with low oil saturations, where water alternating gas injection (WAG) techniques are usually employed for enhanced oil recovery. This negative feature is not observed in the model of Ranaee et al. [2015] due to its ability to embed key effects of pore scale phase distributions, such as hysteresis effects and cycle dependency, for modeling kro observed during WAG. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-14T18:00:54.168613-05:
      DOI: 10.1002/2016WR018872
       
  • Attribution of regional flood changes based on scaling fingerprints
    • Abstract: Changes in the river flood regime may be due to atmospheric processes (e.g. increasing precipitation), catchment processes (e.g. soil compaction associated with land‐use change), and river system processes (e.g. loss of retention volume in the flood plains). This paper proposes a new framework for attributing flood changes to these drivers based on a regional analysis. We exploit the scaling characteristics (i.e., fingerprints) with catchment area of the effects of the drivers on flood changes. The estimation of their relative contributions is framed in Bayesian terms. Analysis of a synthetic, controlled case suggests that the accuracy of the regional attribution increases with increasing number of sites and record lengths, decreases with increasing regional heterogeneity, increases with increasing difference of the scaling fingerprints, and decreases with an increase of their prior uncertainty. The applicability of the framework is illustrated for a case study set in Austria, where positive flood trends have been observed at many sites in the past decades. The individual scaling fingerprints related to the atmospheric, catchment and river system processes are estimated from rainfall data and simple hydrological modelling. Although the distributions of the contributions are rather wide, the attribution identifies precipitation change as the main driver of flood change in the study region. Overall, it is suggested that the extension from local attribution to a regional framework, including multiple drivers and explicit estimation of uncertainty, could constitute a similar shift in flood change attribution as the extension from local to regional flood frequency analysis. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-14T18:00:42.08565-05:0
      DOI: 10.1002/2016WR019036
       
  • Response of the hyporheic zone to transient groundwater fluctuations on
           the annual and storm event time scales
    • Authors: Jonathan M. Malzone; Christopher S. Lowry, Adam S. Ward
      Abstract: The volume of the water stored in and exchanged with the hyporheic zone is an important factor in stream metabolism and biogeochemical cycling. Previous studies have identified groundwater direction and magnitude as one key control on the volume of the hyporheic zone, suggesting that fluctuation in the riparian water table could induce large changes under certain seasonal conditions. In this study, we analyze the transient drivers that control the volume of the hyporheic zone by coupling the Brinkman‐Darcy equation to the Navier‐Stokes equations to simulate annual and storm induced groundwater fluctuations. The expansion and contraction of the hyporheic zone was quantified based on temporally dynamic scenarios simulating annual groundwater fluctuations in a humid temperate climate. The amplitude of the groundwater signal was varied between scenarios to represent a range of annual hydrologic forcing. Storm scenarios were then superimposed on the annual scenario to simulate the response to short term storm signals. Simulations used two different groundwater storm responses; one in‐phase with the surface water response and one 14 hours out‐of‐phase with the surface water response to represent our observed site conditions. Results show that annual groundwater fluctuation is a dominant control on the volume of the hyporheic zone, where increasing groundwater fluctuation increases the amount of annual variation. Storm responses depended on the antecedent conditions determined by annual scenarios, where the time of year dictated the duration and magnitude of the storm induced response of the hyporheic zone. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-13T03:20:36.838663-05:
      DOI: 10.1002/2015WR018056
       
  • Validating a mass balance accounting approach to using 7Be measurements to
           estimate event‐based erosion rates over an extended period at the
           catchment scale
    • Authors: Paolo Porto; Des E. Walling, Vanessa Cogliandro, Giovanni Callegari
      Abstract: Use of the fallout radionuclides cesium‐137 and excess lead‐210 offers important advantages over traditional methods of quantifying erosion and soil redistribution rates. However, both radionuclides provide information on longer‐term (i.e. 50‐100 years) average rates of soil redistribution. Beryllium‐7, with its half‐life of 53 days, can provide a basis for documenting short‐term soil redistribution and it has been successfully employed in several studies. However, the approach commonly used introduces several important constraints related to the timing and duration of the study period. A new approach proposed by the authors that overcomes these constraints has been successfully validated using an erosion plot experiment undertaken in southern Italy. Here, a further validation exercise undertaken in a small (1.38 ha) catchment is reported. The catchment was instrumented to measure event sediment yields and beryllium‐7 measurements were employed to document the net soil loss for a series of 13 events that occurred between November 2013 and June 2015. In the absence of significant sediment storage within the catchment's ephemeral channel system and of a significant contribution from channel erosion to the measured sediment yield, the estimates of net soil loss for the individual events could be directly compared with the measured sediment yields to validate the former. The close agreement of the two sets of values is seen as successfully validating the use of beryllium‐7 measurements and the new approach to obtain estimates of net soil loss for a sequence of individual events occurring over an extended period at the scale of a small catchment. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-13T03:20:27.982256-05:
      DOI: 10.1002/2015WR018136
       
  • Scalable subsurface inverse modeling of huge data sets with an application
           
    • Authors: Jonghyun Lee; Hongkyu Yoon, Peter K. Kitanidis, Charles J. Werth, Albert J. Valocchi
      Abstract: Characterizing subsurface properties is crucial for reliable and cost‐effective groundwater supply management and contaminant remediation. With recent advances in sensor technology, large volumes of hydro‐geophysical and geochemical data can be obtained to achieve high‐resolution images of subsurface properties. However, characterization with such a large amount of information requires prohibitive computational costs associated with “big data” processing and numerous large‐scale numerical simulations. To tackle such difficulties, the Principal Component Geostatistical Approach (PCGA) has been proposed as a “Jacobian‐free” inversion method that requires much smaller forward simulation runs for each iteration than the number of unknown parameters and measurements needed in the traditional inversion methods. PCGA can be conveniently linked to any multi‐physics simulation software with independent parallel executions. In this paper, we extend PCGA to handle a large number of measurements (e.g. 106 or more) by constructing a fast preconditioner whose computational cost scales linearly with the data size. For illustration, we characterize the heterogeneous hydraulic conductivity (K) distribution in a laboratory‐scale 3‐D sand box using about 6 million transient tracer concentration measurements obtained using magnetic resonance imaging. Since each individual observation has little information on the K distribution, the data was compressed by the zero‐th temporal moment of breakthrough curves, which is equivalent to the mean travel time under the experimental setting. Only about 2,000 forward simulations in total were required to obtain the best estimate with corresponding estimation uncertainty, and the estimated K field captured key patterns of the original packing design, showing the efficiency and effectiveness of the proposed method. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-09T18:42:41.716776-05:
      DOI: 10.1002/2015WR018483
       
  • A multiscale approach to determine hydraulic conductivity in thick
           claystone aquitards using field, laboratory, and numerical modeling
           methods
    • Authors: L. A. Smith; S. L. Barbour, M. J. Hendry, K. Novakowski, G. van der Kamp
      Abstract: Characterizing the hydraulic conductivity (K) of aquitards is difficult due to technical and logistical difficulties associated with field‐based methods as well as the cost and challenge of collecting representative and competent core samples for laboratory analysis. The objective of this study was to produce a multi‐scale comparison of vertical and horizontal hydraulic conductivity (Kv and Kh, respectively) of a regionally extensive Cretaceous clay‐rich aquitard in southern Saskatchewan. Ten vibrating wire pressure transducers were lowered into place at depths between 25 and 325 m, then the annular was space was filled with a cement‐bentonite grout. The in situ Kh was estimated at the location of each transducer by simulating the early‐time pore pressure measurements following setting of the grout using a 2D axisymmetric, finite element, numerical model. Core samples were collected during drilling for conventional laboratory testing for Kv to compare with the transducer‐determined in situ Kh. Results highlight the importance of scale and consideration of the presence of possible secondary features (e.g. fractures) in the aquitard. The proximity of the transducers to an active potash mine (∼1 km) where depressurization of an underlying aquifer resulted in drawdown through the aquitard provided a unique opportunity to model the current hydraulic head profile using both the Kh and Kv estimates. Results indicate that the transducer‐determined Kh estimates would allow for the development of the current hydraulic head distribution, and that simulating the pore pressure recovery can be used to estimate moderately low in situ Kh (
      PubDate: 2016-06-08T10:45:32.467166-05:
      DOI: 10.1002/2015WR018448
       
  • Water velocity at water‐air interface is not zero: Comment on
           “Three‐dimensional quantification of soil hydraulic properties
           using X‐ray computed tomography and image‐based
           modeling” By Tracy SR et al.
    • Authors: X.X. Zhang; X.Y. Fan, Z.Y. Li
      PubDate: 2016-06-07T05:26:10.849719-05:
      DOI: 10.1002/2015WR018432
       
  • Using expert elicitation to quantify catchment water balances and their
           uncertainties
    • Authors: E. Sebok; J. C. Refsgaard, J. J. Warmink, S. Stisen, K. H. Jensen
      Abstract: Expert elicitation with the participation of 35 experts was used to estimate a water balance for the nested Ahlergaarde and Holtum catchments in Western Denmark. Average annual values of precipitation, evapotranspiration and surface runoff as well as subsurface outflow and recharge and their uncertainty were estimated in a multi‐step elicitation, where experts first gave their opinion on the probability distribution of their water balance component of interest, then the average annual values and uncertainty of water balance components and catchment‐scale water balances were obtained by reaching consensus during group discussions. The obtained water balance errors for the 1055 km2 Ahlergaarde catchment and 120 km2 Holtum catchment were ‐5 mm/year and ‐62 mm/year, respectively, with an uncertainty of 66 mm/year and 86 mm/year, respectively. As an advantage of the expert elicitation, drawing on the intuitive experience and capabilities of experts to assess complex, site‐specific problems, the contribution of independent sources of uncertainties to the total uncertainty was also evaluated similarly to the subsurface outflow component, which traditionally is estimated as the residual of the water balance. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-06T19:20:35.001525-05:
      DOI: 10.1002/2015WR018461
       
  • On the failure of upscaling the single collector efficiency to the
           transport of colloids in an array of collectors
    • Authors: Francesca Messina; Tiziana Tosco, Rajandrea Sethi
      Abstract: Defining the removal efficiency of a filter is a key aspect for colloid transport in porous media. Several efforts were devoted to derive accurate correlations for the single collector removal efficiency, but its up‐scaling to the entire porous medium is still a challenging topic. A common approach involves the assumption of deposition being independent of the history of transport, that is, the collector efficiency is uniform along the porous medium. However, this approach was shown inadequate under unfavorable deposition conditions. In this work, the authors demonstrate that it is not adequate even in the simplest case of favorable deposition. Computational Fluid Dynamics (CFD) simulations were run in a vertical array of 50 identical spherical collectors. Particle transport was numerically solved by analyzing a broad range of parameters. The results evidenced that, when particle deposition is not controlled by Brownian diffusion, non‐exponential concentration profiles are retrieved, in contrast with the assumption of uniform efficiency. If sedimentation and interception dominate, the efficiency of the first sphere is significantly higher compared to the others, and then declines along the array down to an asymptotic value. Finally, a correlation for the up‐scaled removal efficiency of the entire array was derived. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-06T03:41:01.741948-05:
      DOI: 10.1002/2016WR018592
       
  • Response to: “Water velocity at water‐air interface is not
           zero: Comment on “Three dimensional quantification of soil hydraulic
           properties using X‐ray Computed Tomography and image based
           modelling””
    • Authors: Saoirse R. Tracy; Keith R. Daly, Craig J. Sturrock, Neil M. J. Crout, Sacha J. Mooney, Tiina Roose
      Abstract: In response to the comment raised by Zhang et al (2016) we explore the differences in average velocity computed using slip and no‐slip boundary conditions at the air water interface. We consider a porous medium in which the air phase acts to impede the movement of water rather than to lubricate it, a case closer to the observed distribution of water in our CT images. We find that, whilst the slip boundary condition may be a more accurate approximation, in cases where the air phase is seen to impede water movement the differences between the two approaches are negligible. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-06T03:40:43.652604-05:
      DOI: 10.1002/2016WR018699
       
  • Role of meteorological controls on interannual variations in
           wet‐period characteristics of wetlands
    • Authors: Yanlan Liu; Mukesh Kumar
      Abstract: Many ecological functions of wetlands are influenced by wet‐periods, i.e., the time interval when groundwater table (GWT) is continuously near the land surface. Hence, there is a crucial need to understand the controls on interannual variations of wet‐periods. Given the scarcity of long term measurements of GWT in wetlands, understanding variations in wet‐periods using a measurement approach alone is challenging. Here we used a physically‐based, fully‐distributed hydrologic model, in synergy with publicly available hydrologic data, to simulate long term wet‐period variations in ten inland forested wetlands in a southeastern US watershed. A Bayesian regression and variable selection framework was then implemented to: (a) evaluate the extent to which the simulated wet‐periods can be estimated and predicted by precipitation (Ppt) and potential evapotranspiration (PET); and (b) infer the relative roles of seasonal Ppt and PET. Our results indicate that wet‐period start date and duration could vary by more than 6 months during the 32 year simulation period. Remarkably, 60\% to 90\% of these variations could be captured using regressions based on seasonal Ppt and PET in most wetlands. Effects of seasonal meteorological conditions on wet‐period variations were found to be non‐uniform, which indicate that the annual variables may not explain interannual variations in wet‐periods. The Bayesian framework was able to predict wet‐period variations with errors smaller than 1 month at a 90\% confidence level. The presented framework provides a minimalistic approach for estimating and predicting wet‐period variations in wetlands, and may be used to understand the future responses of associated ecological functions in wetlands. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-06T03:40:35.44722-05:0
      DOI: 10.1002/2015WR018493
       
  • Dynamic groundwater flows and geochemistry in a sandy nearshore aquifer
           over a wave event
    • Authors: Spencer Malott; Denis M. O'Carroll, Clare E. Robinson
      Abstract: Dynamic coastal forcing influence the transport of pollutants in nearshore aquifers and their ultimate flux to coastal waters. In this study, field data is presented that shows, for the first time, the influence of a period of intensified wave conditions (wave event) on nearshore groundwater flows and geochemistry in a sandy beach. Field measurements at a freshwater beach allow wave effects to be quantified without other complex forcing that are present along marine shorelines (e.g. tides). Pressure transducer data obtained over an isolated wave event reveal the development of transient groundwater flow recirculations. The groundwater flows were simulated in FEFLOW using a phase‐averaged wave setup approach to represent waves acting on the sediment‐water interface. Comparison of measured and simulated data indicate that consideration of wave setup alone is able to adequately capture wave‐induced perturbations in groundwater flows. While prior studies have shown sharp pH and redox spatial zonations in nearshore aquifers, this study reveals rapid temporal variations in conductivity, pH and redox (ORP) in shallow sediments (up to 0.5 m depth) in response to varying wave conditions. Comparison of head gradients with calculated conductivity and pH mixing ratios indicates the controlling effect of the wave‐induced water exchange and flows in driving the observed geochemical dynamics. While we are not able to conclusively determine the extent to which temporal variations are caused by conservative mixing versus reactive processes, the pH and ORP variations observed will have significant implications for the fate of reactive pollutants discharging through sandy nearshore aquifers. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-03T03:40:26.678999-05:
      DOI: 10.1002/2015WR017537
       
  • Travel times in the vadose zone: Variability in space and time
    • Authors: Matthias Sprenger; Stefan Seeger, Theresa Blume, Markus Weiler
      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, 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 multi‐modal nature of the site specific master transit time distribution representing the flow averaged probability density for rain water 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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-03T03:36:09.329548-05:
      DOI: 10.1002/2015WR018077
       
  • Improving Budyko curve‐based estimates of long‐term water
           partitioning using hydrologic signatures from GRACE
    • Authors: Kuai Fang; Chaopeng Shen, Joshua B. Fisher, Jie Niu
      Abstract: The Budyko hypothesis provides a first‐order estimate of water partitioning into runoff (Q) and evapotranspiration (E). Observations, however, often show significant departures from the Budyko curve; moreover, past improvements to Budyko curve tend to lose predictive power when migrated between regions or to small scales. Here, to estimate departures from the Budyko curve, we use hydrologic signatures extracted from Gravity Recovery And Climate Experiment (GRACE) terrestrial water storage anomalies. The signatures include GRACE amplitude as a fraction of precipitation (A/P), inter‐annual variability, and 1‐month‐lag auto‐correlation. We created a group of linear models embodying two alternate hypotheses that departures can be predicted by (a) Taylor series expansion based on deviation of physical characteristics (seasonality, snow fraction and vegetation index) from reference conditions; and (b) surrogate indicators co‐varying with E, e.g., A/P. These models are fitted using a mesoscale USA dataset (HUC4) and then evaluated using world datasets and USA basins 1000 km2 and, according to comparison with other global datasets, is suitable for data fusion purposes, with GRACE error as estimates of uncertainty. This article is protected by copyright. All rights reserved.
      PubDate: 2016-06-02T10:42:34.240945-05:
      DOI: 10.1002/2016WR018748
       
  • Measurement and modeling of engineered nanoparticle transport and aging
           dynamics in a reactive porous medium
    • Authors: Aviv Naftaly; Ishai Dror, Brian Berkowitz
      Abstract: A continuous time random walk particle tracking (CTRW‐PT) method was employed to model flow cell experiments that measured transport of engineered nanoparticles (ENPs) in a reactive porous medium. The experiments involved a water‐saturated medium containing negatively‐charged, polyacrylamide beads, resembling many natural soils and aquifer materials, and having the same refraction index as water. Negatively‐ and positively‐charged ENPs were injected into a uniform flow field in a 3‐D horizontal flow cell, and the spatial and temporal concentrations of the evolving ENP plumes were obtained via image analysis. As a benchmark, and to calibrate the model, Congo red tracer was employed in 1‐D column and 3‐D flow cell experiments, containing the same beads. Negatively‐charged Au and Ag ENPs demonstrated migration patterns resembling those of the tracer, but were slightly more dispersive; the transport was well represented by the CTRW‐PT model. In contrast, positively‐charged AgNPs displayed an unusual behavior: establishment of an initial plume of essentially immobilized ENPs, followed by development of a secondary, freely‐migrating plume. The mobile plume was found to contain ENPs that, with aging, exhibited aggregation and charge inversion, becoming negatively charged and mobile. In this case, the CTRW‐PT model was modified to include a probabilistic law for particle immobilization, to account for the decreasing tendency (over distance and time) of the positively‐charged AgNPs to attach to the porous medium. The agreement between experimental results and modeling suggests that the CTRW‐PT framework can account for the non‐Fickian and surface charge dependent transport and aging exhibited by ENPs in porous media. This article is protected by copyright. All rights reserved.
      PubDate: 2016-05-30T03:45:33.650412-05:
      DOI: 10.1002/2016WR018780
       
  • Reply to comments by Keith E. Schilling on “Climate and agricultural
           land use change impacts on streamflow in the upper midwestern United
           States”
    • Authors: Satish C. Gupta; Andrew C. Kessler, Melinda K. Brown, William M. Schuh
      Abstract: The reply addresses concerns raised by Schilling [2015] claiming that Gupta et al. [2015a,b] mischaracterized his research on the impact of land use change on streamflow. We disagree with his interpretation. In the reply we show that our interpretation of his work on lack of climate impact on streamflow is consistent with interpretation by others in the literature including some of his co‐authors (Xu, Scanlon, Schilling, and Sun, 2013) who stated that Schilling [2005] and Zhang and Schilling [2006] studies concluded that land surface change played a dominant role compared to climate change. Our writing may have been too explicit but is similar to that of Ryberg et al. [2014]. We are convinced that a clarification was needed. Furthermore, we provide additional analysis of the Raccoon River flows in Iowa and show that both annual streamflow and baseflow are mainly controlled by precipitation not only in a given year but also by precipitation in the previous year. This article is protected by copyright. All rights reserved.
      PubDate: 2016-05-23T11:14:44.158726-05:
      DOI: 10.1002/2016WR018656
       
  • Comment on “Climate and agricultural land use change impacts on
           streamflow in the upper midwestern United States” by Gupta et al.
    • Authors: Keith E. Schilling
      Abstract: Increasing precipitation and land use/land cover (LU/LC) change have contributed to increasing streamflow and baseflow in many Midwestern rivers but the relative importance of causal factors is open to debate. The dominant LULC change in the agricultural Midwest is the emergence of soybean production that occurred in the mid‐ to late‐20th Century that replaced many sod‐based rotations and increased total row crop area devoted to annual maize and soybean crops. Increasing precipitation may be a more important factor for increasing total discharge whereas LULC changes contributed more to baseflow changes. This article is protected by copyright. All rights reserved.
      PubDate: 2016-05-23T11:14:41.919372-05:
      DOI: 10.1002/2015WR018482
       
  • Trends and sensitivities of low streamflow extremes to discharge timing
           and magnitude in Pacific Northwest mountain streams
    • Authors: Patrick R. Kormos; Charles H. Luce, Seth J. Wenger, Wouter R. Berghuijs
      Abstract: Path analyses of historical streamflow data from the Pacific Northwest indicate that the precipitation amount has been the dominant control on the magnitude of low streamflow extremes compared to the air temperature‐affected timing of snowmelt runoff. The relative sensitivities of low streamflow to precipitation and temperature changes have important implications for adaptation planning because global circulation models produce relatively robust estimates of air temperature changes but have large uncertainties in projected precipitation amounts in the Pacific Northwest. Quantile regression analyses indicate that low streamflow extremes from the majority of catchments in this study have declined from 1948 to 2013, which may significantly affect terrestrial and aquatic ecosystems, and water resource management. Trends in the 25th percentile of mean annual streamflow have declined and the center of timing has occurred earlier. We quantify the relative influences of total precipitation and air temperature on the annual low streamflow extremes from 42 stream gauges using mean annual streamflow as a proxy for precipitation amount effects and streamflow center of timing as a proxy for temperature effects on low flow metrics, including 7q10 summer (the minimum 7‐day flow during summer with a 10‐year return probability), mean August, mean September, mean summer, 7q10 winter, and mean winter flow metrics. These methods have the benefit of using only readily available streamflow data, which makes our results robust against systematic errors in high elevation distributed precipitation data. Winter low flow metrics are weakly tied to both mean annual streamflow and center of timing. This article is protected by copyright. All rights reserved.
      PubDate: 2016-05-23T03:45:33.915467-05:
      DOI: 10.1002/2015WR018125
       
  • Analysis of reach‐scale elevation distribution in braided rivers:
           Definition of a new morphologic indicator and estimation of mean
           quantities
    • Authors: M. Redolfi; M. Tubino, W. Bertoldi, J. Brasington
      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, to a Y‐shape for multi‐thread 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. This article is protected by copyright. All rights reserved.
      PubDate: 2016-05-23T03:45:30.900295-05:
      DOI: 10.1002/2015WR017918
       
  • Reply to comments on “Climate and agricultural land use change
           impacts on streamflow in the upper Midwestern United States” by
           Schottler et al.
    • Authors: Satish C. Gupta; Andrew C. Kessler, Melinda K. Brown, William M. Schuh
      PubDate: 2016-05-06T10:15:26.970528-05:
      DOI: 10.1002/2016WR018827
       
  • Comment on “Climate and agricultural land use change impacts on
           streamflow in the upper Midwestern United States”
    • Authors: Shawn Schottler; Jason Ulrich, Daniel Engstrom
      PubDate: 2016-05-06T10:10:32.825478-05:
      DOI: 10.1002/2015WR018497
       
  • Modeling nonlinear responses of DOC transport in boreal catchments in
           Sweden
    • Authors: Ville Kasurinen; Knut Alfredsen, Anne Ojala, Jukka Pumpanen, Gesa A. Weyhenmeyer, Martyn N. Futter, Hjalmar Laudon, Frank Berninger
      Abstract: Stream water dissolved organic carbon (DOC) concentrations display high spatial and temporal variation in boreal catchments. Understanding and predicting these patterns is a challenge with great implications for water quality projections and carbon balance estimates. Although several biogeochemical models have been used to estimate stream water DOC dynamics, model biases common during both rain and snow melt driven events. The parsimonious DOC‐model, K‐DOC, with ten calibrated parameters, uses a non‐linear discharge and catchment water storage relationship including soil temperature dependencies of DOC release and consumption. K‐DOC was used to estimate the stream water DOC concentrations over five years for eighteen nested boreal catchments having total area of 68 km2 (varying from 0.04 to 67.9 km2). The model successfully simulated DOC concentrations during base flow conditions, as well as, hydrological events in catchments dominated by organic and mineral soils reaching NSEs from 0.46 to 0.76. Our semi‐mechanistic model was parsimonious enough to have all parameters estimated using statistical methods. We did not find any clear differences between forest and mire dominated catchments that could be explained by soil type or tree species composition. However, parameters controlling slow release and consumption of DOC from soil water behaved differently for small headwater catchments (less than 2 km2) than for those that integrate larger areas of different ecosystem types (10‐68 km2). Our results emphasize that it is important to account for non‐linear dependencies of both, soil temperature and catchment water storage, when simulating DOC dynamics of boreal catchments This article is protected by copyright. All rights reserved.
      PubDate: 2016-04-25T19:03:55.980175-05:
      DOI: 10.1002/2015WR018343
       
  • Channel morphology and flow structure of an abandoned channel under
           varying stages
    • Authors: Katie H. Costigan; Joseph E. Gerken
      Abstract: Abandoned channels are those channels left behind as meandering rivers migrate over their floodplains but remain among the most enigmatic features of the riverscape, especially related to their hydraulics and geomorphology. Abandoned channels are being considered and implemented as restoration and rehabilitation strategies for large rivers but we do not yet have a sound understanding of their hydromorphodynamics. The overall objectives of this work were to assess the bed morphology and flow structure of a large, dynamically connected abandoned channel (e.g., the channel is inundated during annual or decadal floods through bank overflow) under varying stages. Here we document the hydromorphodynamics of an abandoned channel during 3.4, 9.2, and 37.9 return interval discharges using an acoustic Doppler current profiler. Flow separation was observed along the channel entrance during the lowest flow surveying campaign but was not seen during the higher flow campaign. Width to depth ratio and channel width at the exit both progressively decreased from the first surveying campaign, despite the final campaign having the highest measured discharge. Large zones of flow stagnation and recirculation were observed, with depth averaged velocity vectors not aligning in one direction, in the abandoned channel where water from the entrance was meeting water coming up from the exit during moderate discharges. The abandoned channel has been maintained for at least 25 years due to its low diversion angle and it being perched above the Kansas River. Results of this study provide insights of how flow hydraulics and physical characteristics of abandoned channel change under varying stages. This article is protected by copyright. All rights reserved.
      PubDate: 2016-04-19T10:36:31.999154-05:
      DOI: 10.1002/2015WR017601
       
  • Issue Information
    • Pages: 4967 - 4969
      PubDate: 2016-08-19T13:08:06.695392-05:
      DOI: 10.1002/wrcr.21698
       
  • Scale dependence of the hydraulic properties of a fractured aquifer
           estimated using transfer functions
    • Pages: 5008 - 5024
      Abstract: We present an investigation of the scale dependence of hydraulic parameters in fractured media based on the concept of transfer functions (TF). TF methods provide an inexpensive way to perform aquifer parameter estimation, as they relate the fluctuations of an observation time series (hydraulic head fluctuations) to an input function (aquifer recharge) in frequency domain. Fractured media are specially sensitive to this approach as hydraulic parameters are strongly scale‐dependent, involving nonstationary statistical distributions. Our study is based on an extensive data set, involving up to 130 measurement points with periodic head measurements that in some cases extend for more than 30 years. For each point, we use a single‐porosity and dual‐continuum TF formulation to obtain a distribution of transmissivities and storativities in both mobile and immobile domains. Single‐porosity TF estimates are compared with data obtained from the interpretation of over 60 hydraulic tests (slug and pumping tests). Results show that the TF is able to estimate the scale dependence of the hydraulic parameters, and it is consistent with the behavior of estimates from traditional hydraulic tests. In addition, the TF approach seems to provide an estimation of the system variance and the extension of the ergodic behavior of the aquifer (estimated in approximately 500 m in the analyzed aquifer). The scale dependence of transmissivity seems to be independent from the adopted formulation (single or dual‐continuum), while storativity is more sensitive to the presence of multiple continua.
      PubDate: 2016-07-02T03:10:12.174416-05:
      DOI: 10.1002/2016WR018660
       
  • Modeling relative permeability of water in soil: Application of
           effective‐medium approximation and percolation theory
    • Authors: Behzad Ghanbarian; Muhammad Sahimi, Hugh Daigle
      Pages: 5025 - 5040
      Abstract: Accurate prediction of the relative permeability to water under partially saturated condition has broad applications and has been studied intensively since the 1940s by petroleum, chemical, and civil engineers, as well as hydrologists and soil scientists. Many models have been developed for this purpose, ranging from those that represent the pore space as a bundle of capillary tubes, to those that utilize complex networks of interconnected pore bodies and pore throats with various cross‐section shapes. In this paper, we propose an approach based on the effective‐medium approximation (EMA) and percolation theory in order to predict the water relative permeability. The approach is general and applicable to any type of porous media. We use the method to compute the water relative permeability in porous media whose pore‐size distribution follows a power law. The EMA is invoked to predict the relative permeability from the fully saturated pore space to some intermediate water saturation that represents a crossover from the EMA to what we refer to as the “critical region.” In the critical region below the crossover water saturation Swx, but still above the critical water saturation Swc (the residual saturation or the percolation threshold of the water phase), the universal power law predicted by percolation theory is used to compute the relative permeability. To evaluate the accuracy of the approach, data for 21 sets of undisturbed laboratory samples were selected from the UNSODA database. For 14 cases, the predicted relative permeabilities are in good agreement with the data. For the remaining seven samples, however, the theory underestimates the relative permeabilities. Some plausible sources of the discrepancy are discussed.
      PubDate: 2016-07-02T03:09:38.114027-05:
      DOI: 10.1002/2015WR017903
       
  • Scale‐dependency of effective hydraulic conductivity on
           fire‐affected hillslopes
    • Authors: Christoph Langhans; Patrick N. J. Lane, Petter Nyman, Philip J. Noske, Jane G. Cawson, Akiko Oono, Gary J. Sheridan
      Pages: 5041 - 5055
      Abstract: Effective hydraulic conductivity (Ke) for Hortonian overland flow modeling has been defined as a function of rainfall intensity and runon infiltration assuming a distribution of saturated hydraulic conductivities (Ks). But surface boundary condition during infiltration and its interactions with the distribution of Ks are not well represented in models. As a result, the mean value of the Ks distribution ( KS¯), which is the central parameter for Ke, varies between scales. Here we quantify this discrepancy with a large infiltration data set comprising four different methods and scales from fire‐affected hillslopes in SE Australia using a relatively simple yet widely used conceptual model of Ke. Ponded disk (0.002 m2) and ring infiltrometers (0.07 m2) were used at the small scales and rainfall simulations (3 m2) and small catchments (ca 3000 m2) at the larger scales. We compared KS¯ between methods measured at the same time and place. Disk and ring infiltrometer measurements had on average 4.8 times higher values of KS¯ than rainfall simulations and catchment‐scale estimates. Furthermore, the distribution of Ks was not clearly log‐normal and scale‐independent, as supposed in the conceptual model. In our interpretation, water repellency and preferential flow paths increase the variance of the measured distribution of Ks and bias ponding toward areas of very low Ks during rainfall simulations and small catchment runoff events while areas with high preferential flow capacity remain water supply‐limited more than the conceptual model of Ke predicts. The study highlights problems in the current theory of scaling runoff generation.
      PubDate: 2016-07-02T03:09:47.463911-05:
      DOI: 10.1002/2016WR018998
       
  • Extraordinary sediment delivery and rapid geomorphic response following
           the 2008–2009 eruption of Chaitén Volcano, Chile
    • Pages: 5075 - 5094
      Abstract: The 10 day explosive phase of the 2008–2009 eruption of Chaitén volcano, Chile, draped adjacent watersheds with a few cm to >1 m of tephra. Subsequent lava‐dome collapses generated pyroclastic flows that delivered additional sediment. During the waning phase of explosive activity, modest rainfall triggered an extraordinary sediment flush which swiftly aggraded multiple channels by many meters. Ten kilometer from the volcano, Chaitén River channel aggraded 7 m and the river avulsed through a coastal town. That aggradation and delta growth below the abandoned and avulsed channels allow estimates of postdisturbance traction‐load transport rate. On the basis of preeruption bathymetry and remotely sensed measurements of delta‐surface growth, we derived a time series of delta volume. The initial flush from 11 to 14 May 2008 deposited 0.5–1.5 × 106 m3 of sediment at the mouth of Chaitén River. By 26 May, after channel avulsion, a second delta amassed about 2 × 106 m3 of sediment; by late 2011 it amassed about 11 × 106 m3. Accumulated sediment consists of low‐density vesicular pumice and lithic rhyolite sand. Rates of channel aggradation and delta growth, channel width, and an assumed deposit bulk density of 1100–1500 kg m−3 indicate mean traction‐load transport rate just before and shortly after avulsion (∼14–15 May) was very high, possibly as great as several tens of kg s−1 m−1. From October 2008 to December 2011, mean traction‐load transport rate declined from about 7 to 0.4 kg−1 m−1. Despite extraordinary sediment delivery, disturbed channels recovered rapidly (a few years).
      PubDate: 2016-07-02T03:08:49.72459-05:0
      DOI: 10.1002/2015WR018250
       
  • A hybrid statistical‐dynamical framework for meteorological drought
           prediction: Application to the southwestern United States
    • Pages: 5095 - 5110
      Abstract: Improving water management in water stressed‐regions requires reliable seasonal precipitation predication, which remains a grand challenge. Numerous statistical and dynamical model simulations have been developed for predicting precipitation. However, both types of models offer limited seasonal predictability. This study outlines a hybrid statistical‐dynamical modeling framework for predicting seasonal precipitation. The dynamical component relies on the physically based North American Multi‐Model Ensemble (NMME) model simulations (99 ensemble members). The statistical component relies on a multivariate Bayesian‐based model that relates precipitation to atmosphere‐ocean teleconnections (also known as an analog‐year statistical model). Here the Pacific Decadal Oscillation (PDO), Multivariate ENSO Index (MEI), and Atlantic Multidecadal Oscillation (AMO) are used in the statistical component. The dynamical and statistical predictions are linked using the so‐called Expert Advice algorithm, which offers an ensemble response (as an alternative to the ensemble mean). The latter part leads to the best precipitation prediction based on contributing statistical and dynamical ensembles. It combines the strength of physically based dynamical simulations and the capability of an analog‐year model. An application of the framework in the southwestern United States, which has suffered from major droughts over the past decade, improves seasonal precipitation predictions (3–5 month lead time) by 5–60% relative to the NMME simulations. Overall, the hybrid framework performs better in predicting negative precipitation anomalies (10–60% improvement over NMME) than positive precipitation anomalies (5–25% improvement over NMME). The results indicate that the framework would likely improve our ability to predict droughts such as the 2012–2014 event in the western United States that resulted in significant socioeconomic impacts.
      PubDate: 2016-07-02T03:08:55.93164-05:0
      DOI: 10.1002/2015WR018547
       
  • Impact of river regulation on a Mediterranean delta: Assessment of managed
           versus unmanaged scenarios
    • Pages: 5132 - 5148
      Abstract: This work addresses the effects of the construction of a reservoir 19 km from the mouth on the dynamics of the Guadalfeo delta (southern Spain), a Mediterranean delta in a semiarid and high‐mountain basin. The sediment volume transported as bed load and accumulated in the delta was estimated under two scenarios by means of a calibrated hydrological model: a managed scenario, considering the flows drained by the dam, and an unmanaged scenario, considering the absence of such infrastructure. Bathymetric and topographic measurements were analyzed and correlated with the fluvial and maritime forcing agents. Results indicate that the reservoir has significantly modified the dynamics downstream: the coast has lost almost 0.3 hm3 of sediments since the entry into operation of the dam, generating a 1.4 km coastline retreat around the mouth, with a maximum retreat of 87 m (92% of the initial). The beach profile decreased by up to 820 m2, whereas the average decrease around the mouth was equal to 214 m2. Under unmanaged conditions, more than 2 hm3 of bed load would have reached the coast. Based on the results, three new management scenarios of flows drained by the dam, in combination with bypassed sediment from the reservoir, were proposed to prevent more severe consequences in the delta and the silting of the reservoir. The proposed methodology for new management scenarios can be extended to other worldwide deltas, especially to those in semiarid and Mediterranean basins, and it represents an advanced tool for decision making.
      PubDate: 2016-07-02T03:09:02.859569-05:
      DOI: 10.1002/2015WR018395
       
  • Scale dependence of Hortonian rainfall‐runoff processes in a
           semiarid environment
    • Authors: L. Chen; S. Sela, T. Svoray, S. Assouline
      Pages: 5149 - 5166
      Abstract: Scale dependence of Hortonian rainfall‐runoff processes has received much attention in the literature but has not been fully resolved. To further explore this issue, a recently developed model was applied to simulate rainfall‐infiltration‐runoff processes at multiple spatial scales. The model consists of the coupling between a two‐dimensional runoff routing module and a two‐layer infiltration module, thus accounting for spatial variability in soil properties, soil surface sealing, topography, and partial vegetation cover. A 76 m2 semiarid experimental plot with sparse cover of vegetation patches and a sealed soil surface in inter‐patch bare areas was used as a representative elementary area (REA). A series of four larger artificial plots of different areas was created based on this REA to examine the scale dependence of rainfall‐runoff relationships in the case of stationary heterogeneity. Results show that runoff depth (or runoff coefficient) decreases with increasing scale. This trend is more prominent at scales less than 10 times the REA length. Power law relationships can quantitatively describe the scaling law. The major mechanism of the scale effect is run‐on infiltration. However, rainfall intensity and soil properties can both affect the scaling trend through their interaction with run‐on. Higher intensity and less temporal variability of rainfall can both reduce the scale effect. Temporally intermittent rainfall may produce spatially oscillating infiltration rates at large scales. Vegetation patterns are another factor that may affect the scaling. Random‐vegetation patterns, compared with regular patterns with similar statistical properties, change the spatial distributions, but do not significantly change either the total amount and statistical properties of infiltration and runoff or the scale dependence of the rainfall‐runoff process.
      PubDate: 2016-07-02T03:03:44.405125-05:
      DOI: 10.1002/2015WR018315
       
  • Infiltration experiments demonstrate an explicit connection between
           heterogeneity and anomalous diffusion behavior
    • Authors: N. Filipovitch; K. M. Hill, A. Longjas, V. R. Voller
      Pages: 5167 - 5178
      Abstract: Transport in systems containing heterogeneity distributed over multiple length scales can exhibit anomalous diffusion behaviors, where the time exponent, determining the spreading length scale of the transported scalar, differs from the expected value of n=12. Here we present experimental measurements of the infiltration of glycerin, under a fixed pressure head, into a Hele‐Shaw cell containing a 3‐D printed distribution of flow obstacles; a system that is an analog for infiltration into a porous medium. In support of previously presented direct simulation results, we experimentally demonstrate that, when the obstacles are distributed as a fractal carpet with fractal dimension H 
      PubDate: 2016-07-02T03:09:21.910085-05:
      DOI: 10.1002/2016WR018667
       
  • Actively heated high‐resolution fiber‐optic‐distributed
           temperature sensing to quantify streambed flow dynamics in zones of strong
           groundwater upwelling
    • Authors: Martin A. Briggs; Sean F. Buckley, Amvrossios C. Bagtzoglou, Dale D. Werkema, John W. Lane
      Pages: 5179 - 5194
      Abstract: Zones of strong groundwater upwelling to streams enhance thermal stability and moderate thermal extremes, which is particularly important to aquatic ecosystems in a warming climate. Passive thermal tracer methods used to quantify vertical upwelling rates rely on downward conduction of surface temperature signals. However, moderate to high groundwater flux rates (>−1.5 m d−1) restrict downward propagation of diurnal temperature signals, and therefore the applicability of several passive thermal methods. Active streambed heating from within high‐resolution fiber‐optic temperature sensors (A‐HRTS) has the potential to define multidimensional fluid‐flux patterns below the extinction depth of surface thermal signals, allowing better quantification and separation of local and regional groundwater discharge. To demonstrate this concept, nine A‐HRTS were emplaced vertically into the streambed in a grid with ∼0.40 m lateral spacing at a stream with strong upward vertical flux in Mashpee, Massachusetts, USA. Long‐term (8–9 h) heating events were performed to confirm the dominance of vertical flow to the 0.6 m depth, well below the extinction of ambient diurnal signals. To quantify vertical flux, short‐term heating events (28 min) were performed at each A‐HRTS, and heat‐pulse decay over vertical profiles was numerically modeled in radial two dimension (2‐D) using SUTRA. Modeled flux values are similar to those obtained with seepage meters, Darcy methods, and analytical modeling of shallow diurnal signals. We also observed repeatable differential heating patterns along the length of vertically oriented sensors that may indicate sediment layering and hyporheic exchange superimposed on regional groundwater discharge.
      PubDate: 2016-07-02T03:05:48.91018-05:0
      DOI: 10.1002/2015WR018219
       
  • Can a paleodrought record be used to reconstruct streamflow?: A case
           study for the Missouri River Basin
    • Authors: Michelle Ho; Upmanu Lall, Edward R. Cook
      Pages: 5195 - 5212
      Abstract: Recent advances in paleoclimatology have revealed dramatic long‐term hydroclimatic variations that provide a context for limited historical records. A notable data set derived from a relatively dense network of paleoclimate proxy records in North America is the Living Blended Drought Atlas (LBDA): a gridded tree‐ring‐based reconstruction of summer Palmer Drought Severity Index. This index has been used to assess North American drought frequency, persistence, and spatial extent over the past two millennia. Here, we explore whether the LBDA can be used to reconstruct annual streamflow. Relative to streamflow reconstructions that use tree rings within the river basin of interest, the use of a gridded proxy poses a novel challenge. The gridded series have high spatial correlation, since they rely on tree rings over a common radius of influence. A novel algorithm for reconstructing streamflow using regularized canonical regression and inputs of local and global covariates is developed and applied over the Missouri River Basin, as a test case. Effectiveness in reconstruction is demonstrated with reconstructions showing periods where streamflow deficits may have been more severe than during recent droughts (e.g., the Civil War, Dust Bowl, and 1950s droughts). The maximum persistence of droughts and floods over the past 500 years far exceeds those observed in the instrumental record and periods of multidecadal variability in the 1500s and 1600s are detected. Challenges for an extension to a national streamflow reconstruction or applications using other gridded paleoclimate data sets such as adequate spatial coverage of streamflow and applicability of annual reconstructions are discussed.
      PubDate: 2016-07-02T03:05:11.660188-05:
      DOI: 10.1002/2015WR018444
       
  • Detection of carbon dioxide leakage during injection in deep saline
           formations by pressure tomography
    • Authors: Linwei Hu; Peter Bayer, Ralf Brauchler
      Pages: 5676 - 5686
      Abstract: CO2 injected into storage formations may escape to the overlying permeable layers. Mixed‐phase diffusivity, namely the ratio of hydraulic conductivity and specific storage of the phase mixture, declines with increasing CO2 saturation. Thus, it can be an indicator of CO2 leakage. In this study, we perform interference brine or CO2 injection tests in a synthetic model, including a storage reservoir, an above aquifer, and a caprock. Pressure transients derived from an observation well are utilized for a travel‐time based inversion technique. Variations of diffusivity are resolved by inverting early travel time diagnostics, providing an insight of plume development. Results demonstrate that the evolution of CO2 leakage in the above aquifer can be inferred by interpreting and comparing the pressure observations, travel times, and diffusivity tomograms from different times. The extent of the plume in reservoir and upper aquifer are reconstructed by clustering the time‐lapse data sets of the mixed‐phase diffusivity, as the diffusivity cannot be exactly reproduced by the inversion. Furthermore, this approach can be used to address different leaky cases, especially for leakage occurring during the injection.
      PubDate: 2016-07-02T03:08:17.938387-05:
      DOI: 10.1002/2015WR018420
       
 
 
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