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  Subjects -> WATER RESOURCES (Total: 148 journals)
Showing 1 - 47 of 47 Journals sorted alphabetically
Acque Sotterranee - Italian Journal of Groundwater     Open Access   (Followers: 1)
Acta Limnologica Brasiliensia     Open Access   (Followers: 3)
Advances in Oceanography and Limnology     Open Access   (Followers: 11)
Advances in Water Resource and Protection     Open Access   (Followers: 11)
Advances in Water Resources     Hybrid Journal   (Followers: 42)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 13)
Agricultural Water Management     Hybrid Journal   (Followers: 38)
American Journal of Water Resources     Open Access   (Followers: 7)
American Water Works Association     Hybrid Journal   (Followers: 20)
Anales de Hidrología Médica     Open Access   (Followers: 1)
Annals of Warsaw University of Life Sciences - SGGW. Land Reclamation     Open Access  
Annual Review of Marine Science     Full-text available via subscription   (Followers: 11)
Applied Water Science     Open Access   (Followers: 8)
Aquacultural Engineering     Hybrid Journal   (Followers: 7)
Aquaculture     Hybrid Journal   (Followers: 32)
Aquaculture Environment Interactions     Open Access   (Followers: 2)
Aquaculture Research     Hybrid Journal   (Followers: 31)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 34)
Aquatic Geochemistry     Hybrid Journal   (Followers: 3)
Aquatic Living Resources     Hybrid Journal   (Followers: 11)
Aquatic Procedia     Open Access   (Followers: 2)
Aquatic Science and Technology     Open Access   (Followers: 3)
Aquatic Sciences     Hybrid Journal   (Followers: 12)
Asian Journal of Rural Development     Open Access   (Followers: 7)
Australian Journal of Water Resources     Full-text available via subscription   (Followers: 6)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 21)
Civil and Environmental Research     Open Access   (Followers: 18)
CLEAN - Soil, Air, Water     Hybrid Journal   (Followers: 20)
Computational Water, Energy, and Environmental Engineering     Open Access   (Followers: 4)
Cost Effectiveness and Resource Allocation     Open Access   (Followers: 5)
Desalination     Hybrid Journal   (Followers: 7)
Desalination and Water Treatment     Hybrid Journal   (Followers: 11)
Developments in Water Science     Full-text available via subscription   (Followers: 9)
Ecological Chemistry and Engineering S     Open Access   (Followers: 4)
Environmental Science : Water Research & Technology     Full-text available via subscription   (Followers: 6)
Environmental Toxicology     Hybrid Journal   (Followers: 9)
EQA - International Journal of Environmental Quality     Open Access   (Followers: 1)
European journal of water quality - Journal européen d'hydrologie     Full-text available via subscription   (Followers: 6)
Ground Water Monitoring & Remediation     Hybrid Journal   (Followers: 18)
Groundwater for Sustainable Development     Full-text available via subscription   (Followers: 1)
Grundwasser     Hybrid Journal  
Hydro Nepal : Journal of Water, Energy and Environment     Open Access   (Followers: 4)
Hydrology Research     Partially Free   (Followers: 12)
Hydrology: Current Research     Open Access   (Followers: 12)
IDA Journal of Desalination and Water Reuse     Hybrid Journal   (Followers: 1)
Ingeniería del agua     Open Access  
International Journal of Climatology     Hybrid Journal   (Followers: 25)
International Journal of Hydrology Science and Technology     Hybrid Journal   (Followers: 4)
International Journal of Nuclear Desalination     Hybrid Journal  
International Journal of River Basin Management     Hybrid Journal   (Followers: 1)
International Journal of Salt Lake Research     Hybrid Journal   (Followers: 2)
International Journal of Waste Resources     Open Access   (Followers: 4)
International Journal of Water     Hybrid Journal   (Followers: 14)
International Journal of Water Resources and Environmental Engineering     Open Access   (Followers: 9)
International Journal of Water Resources Development     Hybrid Journal   (Followers: 22)
International Soil and Water Conservation Research     Open Access  
Irrigation and Drainage     Hybrid Journal   (Followers: 12)
Irrigation Science     Hybrid Journal   (Followers: 4)
Journal of Aquatic Sciences     Full-text available via subscription   (Followers: 2)
Journal of Contemporary Water Resource & Education     Hybrid Journal   (Followers: 3)
Journal of Environmental Health Science & Engineering     Open Access   (Followers: 1)
Journal of Fisheries and Aquatic Science     Open Access   (Followers: 5)
Journal of Geophysical Research : Oceans     Partially Free   (Followers: 49)
Journal of Hydro-environment Research     Full-text available via subscription   (Followers: 9)
Journal of Hydroinformatics     Full-text available via subscription   (Followers: 2)
Journal of Hydrology (New Zealand)     Full-text available via subscription   (Followers: 1)
Journal of Hydrology and Hydromechanics     Open Access   (Followers: 2)
Journal of Hydrometeorology     Full-text available via subscription   (Followers: 6)
Journal of Limnology     Open Access   (Followers: 6)
Journal of the American Water Resources Association     Hybrid Journal   (Followers: 29)
Journal of Water and Climate Change     Partially Free   (Followers: 37)
Journal of Water and Health     Partially Free   (Followers: 3)
Journal of Water Chemistry and Technology     Hybrid Journal   (Followers: 9)
Journal of Water Process Engineering     Full-text available via subscription   (Followers: 4)
Journal of Water Resource and Hydraulic Engineering     Open Access   (Followers: 9)
Journal of Water Resource and Protection     Open Access   (Followers: 9)
Journal of Water Resource Engineering and Management     Full-text available via subscription   (Followers: 3)
Journal of Water Resources Planning and Management     Full-text available via subscription   (Followers: 46)
Journal of Water Reuse and Desalination     Partially Free   (Followers: 6)
Journal of Water Science & Environment Technologies     Open Access   (Followers: 2)
Journal of Water Security     Open Access   (Followers: 1)
Journal of Water Supply : Research and Technology - AQUA     Partially Free   (Followers: 7)
Journal of Water, Sanitation and Hygiene for Development     Open Access   (Followers: 5)
La Houille Blanche     Full-text available via subscription   (Followers: 1)
Lake and Reservoir Management     Hybrid Journal   (Followers: 7)
Lakes & Reservoirs Research & Management     Hybrid Journal   (Followers: 14)
Large Marine Ecosystems     Full-text available via subscription  
Liquid Waste Recovery     Open Access  
Mangroves and Salt Marshes     Hybrid Journal   (Followers: 2)
Marine and Freshwater Behaviour and Physiology     Hybrid Journal   (Followers: 1)
Marine Ecology Progress Series MEPS     Hybrid Journal   (Followers: 23)
Marine Ecosystem Stressor Response     Open Access  
Methods in Oceanography : An International Journal     Hybrid Journal   (Followers: 4)
New Zealand Journal of Marine and Freshwater Research     Hybrid Journal   (Followers: 6)
Open Journal of Modern Hydrology     Open Access   (Followers: 4)
Osterreichische Wasser- und Abfallwirtschaft     Hybrid Journal  
Ozone Science & Engineering     Hybrid Journal   (Followers: 1)
Paddy and Water Environment     Hybrid Journal   (Followers: 9)
Research Journal of Environmental Toxicology     Open Access   (Followers: 2)
Reviews in Aquaculture     Hybrid Journal   (Followers: 10)
Revue des sciences de l'eau / Journal of Water Science     Full-text available via subscription   (Followers: 2)
RIBAGUA - Revista Iberoamericana del Agua     Open Access  
Riparian Ecology and Conservation     Open Access   (Followers: 6)
River Research and Applications     Hybrid Journal   (Followers: 16)
River Systems     Full-text available via subscription   (Followers: 3)
SA Irrigation = SA Besproeiing     Full-text available via subscription   (Followers: 1)
SABI Magazine - Tydskrif     Full-text available via subscription  
San Francisco Estuary and Watershed Science     Open Access  
Sciences Eaux & Territoires : la Revue du Cemagref     Open Access  
Scientia Marina     Open Access   (Followers: 2)
Smart Water     Open Access  
Society & Natural Resources: An International Journal     Hybrid Journal   (Followers: 17)
Sri Lanka Journal of Aquatic Sciences     Open Access   (Followers: 1)
Sustainability of Water Quality and Ecology     Hybrid Journal   (Followers: 4)
Sustainable Technologies, Systems & Policies     Open Access   (Followers: 8)
Tecnología y Ciencias del Agua     Open Access  
Texas Water Journal     Open Access   (Followers: 2)
Urban Water Journal     Hybrid Journal   (Followers: 13)
Waste Technology     Open Access   (Followers: 3)
Water     Open Access   (Followers: 6)
Water & Sanitation Africa     Full-text available via subscription   (Followers: 4)
Water and Environment Journal     Hybrid Journal   (Followers: 22)
Water Environment and Technology     Full-text available via subscription   (Followers: 16)
Water Environment Research     Full-text available via subscription   (Followers: 41)
Water International     Hybrid Journal   (Followers: 14)
Water Policy     Partially Free   (Followers: 7)
Water Practice     Full-text available via subscription   (Followers: 3)
Water Practice and Technology     Full-text available via subscription   (Followers: 13)
Water Quality Research Journal of Canada     Full-text available via subscription   (Followers: 4)
Water Research     Hybrid Journal   (Followers: 53)
Water Resources     Hybrid Journal   (Followers: 20)
Water Resources and Economics     Hybrid Journal   (Followers: 4)
Water Resources and Industry     Open Access   (Followers: 3)
Water Resources and Rural Development     Hybrid Journal   (Followers: 2)
Water Resources Management     Hybrid Journal   (Followers: 35)
Water Resources Research     Full-text available via subscription   (Followers: 79)
Water SA     Open Access  
Water Science & Technology     Partially Free   (Followers: 25)
Water Science : The National Water Research Center Journal     Open Access   (Followers: 6)
Water Science and Engineering     Open Access   (Followers: 9)
Water Science and Technology : Water Supply     Partially Free   (Followers: 21)
Water Wheel     Open Access   (Followers: 2)
Water, Air, & Soil Pollution     Hybrid Journal   (Followers: 25)
Water21     Full-text available via subscription   (Followers: 1)
Waterlines     Full-text available via subscription   (Followers: 2)
Western Indian Ocean Journal of Marine Science     Open Access   (Followers: 1)
Wetlands Ecology and Management     Hybrid Journal   (Followers: 20)
Wiley Interdisciplinary Reviews : Water     Hybrid Journal  
WMU Journal of Maritime Affairs     Hybrid Journal   (Followers: 3)

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Journal Cover Water Resources Research
  [SJR: 2.661]   [H-I: 144]   [79 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 0043-1397 - ISSN (Online) 1944-7973
   Published by AGU Homepage  [17 journals]
  • Replenishing an unconfined coastal aquifer to control seawater intrusion:
           Injection or infiltration?
    • Authors: Chunhui Lu; Wenlong Shi, Pei Xin, Jichun Wu, Adrian D. Werner
      Abstract: In this study, we compare the performances of well injection and pond infiltration in controlling seawater intrusion in an unconfined coastal aquifer through two scenario groups: (1) a single injection well vs. an elliptic infiltration pond, and (2) an injection-extraction well pair system vs. an elliptic infiltration pond-extraction well system. Comparison is based on quantitative indicators that include the interface toe location, saltwater volume, and maximum net extraction rate (for scenario 2). We introduce a method to determine the maximum net extraction rate for cases where the locations of stagnation points cannot be easily derived. Analytical analysis shows that the performances of injection and infiltration are the same, provided that the pond shape is circular. The examination of scenario group (1) suggests that the shape of the infiltration pond has a minor effect on the interface toe location as well as the reduction in the saltwater volume, given the same total recharge rate. The investigation of scenario group (2) indicates, by contrast, that the maximum net extraction rate increases significantly with the increasing ratio of b to a, where a and b are semi-axes of the ellipse parallel and perpendicular to the coastline, respectively. Specifically, for a typical aquifer assumed, an increase of 40% is obtained for the maximum net extraction when b/a increases from 1/200 to 200. Despite that the study is based on a simplified model, the results provide initial guidance for practitioners when planning to use an aquifer recharge strategy to restore a salinized unconfined coastal aquifer.
      PubDate: 2017-05-19T09:05:57.062423-05:
      DOI: 10.1002/2016WR019625
       
  • Periodic sediment shift in migrating ripples influences benthic microbial
           activity
    • Authors: Sanja Zlatanovic; Jenny Fabian, Clara Mendoza-Lera, K. Benjamin Woodward, Katrin Premke, Michael Mutz
      Abstract: Migrating bedforms have high levels of particulate organic matter and high rates of pore water exchange, causing them to be proposed as hot spots of carbon turnover in rivers. However, the shifting of sediments and associated mechanical disturbance within migrating bedforms, such as ripples, may stress and abrade microbial communities, reducing their activity. In a microcosm experiment, we replicated the mechanical disturbances caused by the periodic sediment shift within ripples under oligotrophic conditions. We assessed the effects on fungal and bacterial biomass ratio (F:B), microbial community respiration (CR), and bacterial production (BCP) and compared with stable undisturbed sediments. Interactions between periodic mechanical disturbance and sediment-associated particulate organic matter (POM) were tested by enriching sediments collected from migrating ripples with different qualities of POM (fish feces, leaf litter fragments and no addition treatments). F:B and BCP were affected by an interaction between mechanical disturbance and POM quality. Fish feces enriched sediments showed increased F:B and BCP compared to sediments with lower POM quality and responded with a decrease of F:B and BCP to sediment disturbance. In the other POM treatments F:B and BCP were not affected by disturbance. Microbial respiration was however reduced by mechanical disturbance to similar low activity levels regardless of POM qualities added, whereas fish feces enriched sediment showed short temporary boost of CR. With the worldwide proliferation of migrating sand ripples due to massive catchment erosion, suppressed mineralization of POM will increasingly affect stream metabolism, downstream transport of POM and carbon cycling from reach to catchment scale.
      PubDate: 2017-05-19T09:05:52.965713-05:
      DOI: 10.1002/2017WR020656
       
  • Induced heterogeneity of soil water content and chemical properties by
           treated wastewater irrigation and its reclamation by freshwater irrigation
           
    • Authors: Matan Rahav; Naaran Brindt, Uri Yermiyahu, Rony Wallach
      Abstract: The recognition of treated wastewater (TWW) as an alternative water resource is expanding in areas with a shortage of freshwater (FW) resources. Today, most orchards in Israel are irrigated with TWW. While the benefits of using TWW for irrigation are apparent, evidence of its negative effects on soil, trees and yield is accumulating. This study, performed in a commercial TWW-irrigated citrus orchard in central Israel, examined the effects of (1) soil-wettability decrease due to prolonged TWW irrigation on the spatial and temporal distribution of water content and associated chemical properties in the root zone; (2) the conversion of irrigation in half of the TWW-irrigated research plot to FW (2012) for soil reclamation. Electrical resistivity tomography surveys in the substantially water repellent soils revealed that water flow is occurring along preferential flow paths in both plots, leaving behind a considerably nonuniform water-content distribution. This was despite the gradual relief in soil water repellency measured in the FW plots. Four soil-sampling campaigns (spring and fall, 2014–2016), performed in 0–20 and 20–40 cm layers of the research plot, revealed bimodal gravimetrically measured water-content distribution. The preferential flow led to uneven chemical-property distribution, with substantially high concentrations in the dry spots, and lower concentrations in the wet spots along the preferential flow paths. The average salt and nutrient concentrations, which were initially high in both plots, gradually dispersed with time, as concentrations in the FW plots decreased. Nevertheless, the efficiency of reclaiming TWW soil by FW irrigation appears low.
      PubDate: 2017-05-19T09:05:48.879466-05:
      DOI: 10.1002/2016WR019860
       
  • Concentration-discharge relationships during an extreme event: Contrasting
           behavior of solutes and changes to chemical quality of dissolved organic
           material in the Boulder Creek Watershed during the September 2013 flood
    • Authors: Garrett P. Rue; Nathan D. Rock, Rachel S. Gabor, John Pitlick, Malak Tfaily, Diane M. McKnight
      Abstract: During the week of September 9-15, 2013, about 44 cm of rain fell across Boulder County, Colorado, USA, representing a very rare precipitation event. The resultant stream flows corresponded to an extreme event not seen since the historical flood of 1894. For the Boulder Creek Critical Zone Observatory (BcCZO), this event provided an opportunity to study the effect of extreme rainfall on solute concentration-discharge relationships and biogeochemical processes. We measured weathering-derived lithologic solutes (Ca, Mg, Na, K, and Si) and dissolved organic carbon (DOC) concentrations at two sites on Boulder Creek during the recession of peak flow. We also isolated four distinct fractions of dissolved organic matter (DOM) for chemical characterization. At the upper and lower sites, all solutes had their highest concentration at peak flow. At the upper site, which represented a mostly forested catchment, the concentrations of lithologic solutes decreased slightly during flood recession. In contrast, DOC and K concentrations decreased by a factor of three. At the lower site within the urban corridor, concentration of lithologic solutes decreased substantially for a few days before rebounding, whereas the DOC and K concentrations continued to decrease. Additionally, we found spatiotemporal trends in the chemical quality of DOM that were consistent with a limited reservoir of soluble organic matter in surficial soils becoming depleted and deeper layers of the Critical Zone contributing DOM during the flood recession. Overall, these results suggest that despite the extreme flood event, concentration-discharge relationships were similar to typical snowmelt periods in this Rocky Mountain region.
      PubDate: 2017-05-19T09:05:47.469953-05:
      DOI: 10.1002/2016WR019708
       
  • Observations of the impact of rock heterogeneity on solute spreading and
           mixing
    • Authors: Maartje Boon; Branko Bijeljic, Sam Krevor
      Abstract: Rock heterogeneity plays an important role in solute spreading and mixing in hydrogeologic systems. Few observations, however, have been made that can spatially resolve these processes in 3-D, in consolidated rocks. We make observations of the spatially resolved steady state concentration of a sodium iodide solute while flowing brine through cylindrical rock cores using X-ray CT imaging. Three rocks with an increasing level of heterogeneity are chosen: Berea sandstone, Ketton carbonate and Indiana carbonate. The impact of heterogeneity on solute transport is analyzed by: 1., quantifying spreading and mixing using metrics such as the transverse dispersion coefficient, the dilution index, the reactor ratio and the scalar dissipation rate, and 2., visualizing and analyzing flow structures such as meandering, flow-focusing and flow-splitting using iso-concentration contour maps. The transverse dispersion coefficient, Dt, and the variation in Dt throughout the rock core, increases with Peclét number (Pe) and rock heterogeneity. The reactor ratio indicates that mixing is Fickian for the Berea sandstone and Ketton carbonate, but diverges for the Indiana carbonate. The temporal evolution of the scalar dissipation rate, a measure of the mixing rate, remains close to that of Fickian mixing for the Berea and Ketton rocks but not for the Indiana. Heterogeneous rock features are observed to cause meandering, focusing or splitting of the plume depending on Pe.
      PubDate: 2017-05-19T09:05:45.564374-05:
      DOI: 10.1002/2016WR019912
       
  • Time scales of relaxation dynamics during transient conditions in
           two-phase flow
    • Authors: Steffen Schlüter; Steffen Berg, Tianyi Li, Hans-Jörg Vogel, Dorthe Wildenschild
      Abstract: The relaxation dynamics towards a hydrostatic equilibrium after a change in phase saturation in porous media is governed by fluid reconfiguration at the pore scale. Little is known whether a hydrostatic equilibrium in which all interfaces come to rest is ever reached and which microscopic processes govern the time scales of relaxation. Here we apply fast synchrotron-based X-ray tomography (X-ray CT) to measure the slow relaxation dynamics of fluid interfaces in a glass bead pack after fast drainage of the sample. The relaxation of interfaces triggers internal redistribution of fluids, reduces the surface energy stored in the fluid interfaces and relaxes the contact angle towards the equilibrium value while the fluid topology remains unchanged. The equilibration of capillary pressures occurs in two stages: (i) a quick relaxation within seconds in which most of the pressure drop that built up during drainage is dissipated, a process that is to fast to be captured with fast X-ray CT, and (ii) a slow relaxation with characteristic time scales of 1-4 h which manifests itself as a spontaneous imbibition process that is well described by the Washburn equation for capillary rise in porous media. The slow relaxation implies that a hydrostatic equilibrium is hardly ever attained in practice when conducting two-phase experiments in which a flux boundary condition is changed from flow to no-flow. Implications for experiments with pressure boundary conditions are discussed.
      PubDate: 2017-05-17T11:30:45.529344-05:
      DOI: 10.1002/2016WR019815
       
  • Partitioning into hazard subregions for regional peaks-over-threshold
           modeling of heavy precipitation
    • Authors: J. Carreau; P. Naveau, L. Neppel
      Abstract: The French Mediterranean is subject to intense precipitation events occurring mostly in autumn. These can potentally cause flash floods, the main natural danger in the area. The distribution of these events follows specific spatial patterns, i.e. some sites are more likely to be affected than others. The peaks-over-threshold approach consists in modeling extremes, such as heavy precipitation, by the generalized Pareto (GP) distribution. The shape parameter of the GP controls the probability of extreme events and can be related to the hazard level of a given site. When interpolating across a region, the shape parameter should reproduce the observed spatial patterns of the probability of heavy precipitation. However, the shape parameter estimators have high uncertainty which might hide the underlying spatial variability. As a compromise, we choose to let the shape parameter vary in a moderate fashion. More precisely, we assume that the region of interest can be partitioned into sub-regions with constant hazard level. We formalize the model as a conditional mixture of GP distributions. We develop a two-step inference strategy based on probability weighted moments and put forward a cross-validation procedure to select the number of sub-regions. A synthetic data study reveals that the inference strategy is consistent and not very sensitive to the selected number of sub-regions. An application on daily precipitation data from the French Mediterranean shows that the conditional mixture of GPs outperforms two interpolation approaches (with constant or smoothly varying shape parameter).
      PubDate: 2017-05-17T11:30:33.961973-05:
      DOI: 10.1002/2017WR020758
       
  • Chemical mass transport between fluid fine tailings and the overlying
           water cover of an oil sands end pit lake
    • Authors: Kathryn A. Dompierre; S. Lee Barbour, Rebecca L. North, Sean K. Carey, Matthew B.J. Lindsay
      Abstract: Fluid fine tailings (FFT) are a principal by-product of the bitumen extraction process at oil sands mines. Base Mine Lake (BML) – the first full-scale demonstration oil sands end pit lake (EPL) – contains approximately 1.9 x108 m3 of FFT stored under a water cover within a decommissioned mine pit. Chemical mass transfer from the FFT to the water cover can occur via two key processes: (1) advection-dispersion driven by tailings settlement; and (2) FFT disturbance due to fluid movement in the water cover. Dissolved chloride (Cl) was used to evaluate the water cover mass balance and to track mass transport within the underlying FFT based on field sampling and numerical modeling. Results indicated that FFT was the dominant Cl source to the water cover and that the FFT is exhibiting a transient advection-dispersion mass transport regime with intermittent disturbance near the FFT-water interface. The advective pore water flux was estimated by the mass balance to be 0.002 m3 m−2 d−1, which represents 0.73 m of FFT settlement per year. However, the FFT pore water Cl concentrations and corresponding mass transport simulations indicated that advection rates and disturbance depths vary between sample locations. The disturbance depth was estimated to vary with location between 0.75 and 0.95 m. This investigation provides valuable insight for assessing the geochemical evolution of the water cover and performance of EPLs as an oil sands reclamation strategy.
      PubDate: 2017-05-17T11:25:34.802655-05:
      DOI: 10.1002/2016WR020112
       
  • Nonparametric triple collocation
    • Authors: Grey S. Nearing; Soni Yatheendradas, Wade T. Crow, David D. Bosch, Michael H. Cosh, David C. Goodrich, Mark S. Seyfried, Patrick J. Starks
      Abstract: Triple collocation has found widespread application in the hydrological sciences because it provides information about the errors in our measurements without requiring that we have any direct access to the true value of the variable being measured. Triple collocation derives variance-covariance relationships between three or more independent measurement sources and an indirectly observed truth variable in the case where the measurement operators are additive. We generalize that theory to arbitrary observation operators by deriving nonparametric analogues to the total error and total correlation statistics as integrations of divergences from conditional to marginal probability ratios. The nonparametric solution to the full measurement problem is under-determined, and we therefore retrieve conservative bounds on the theoretical total nonparametric error and correlation statistics. We examine the application of both linear and nonlinear triple collocation to synthetic examples and to a real-data test case related to evaluating space-borne soil moisture retrievals using sparse monitoring networks and dynamical process models.
      PubDate: 2017-05-17T11:25:27.284272-05:
      DOI: 10.1002/2017WR020359
       
  • Improved characterization of heterogeneous permeability in saline aquifers
           from transient pressure data during freshwater injection
    • Authors: Peter K. Kang; Jonghyun Lee, Xiaojing Fu, Seunghak Lee, Peter K. Kitanidis, Ruben Juanes
      Abstract: Managing recharge of freshwater into saline aquifers requires accurate estimation of the heterogeneous permeability field for maximizing injection and recovery efficiency. Here, we present a methodology for subsurface characterization in saline aquifers that takes advantage of the density difference between the injected freshwater and the ambient saline groundwater. We combine high resolution forward modeling of density-driven flow with an efficient Bayesian geostatistical inversion algorithm.In the presence of a density difference between the injected and ambient fluids due to differences in salinity, the pressure field is coupled to the spatial distribution of salinity. This coupling renders the pressure field transient: the time evolution of the salinity distribution controls the density distribution which then leads to a time-evolving pressure distribution.We exploit this coupling between pressure and salinity to obtain an improved characterization of the permeability field without multiple pumping tests or additional salinity measurements. We show that the inversion performance improves with an increase in the mixed convection ratio–the relative importance between viscous forces from injection and buoyancy forces from density difference. Our work shows that measuring transient pressure data at multiple sampling points during freshwater injection into saline aquifers can be an effective strategy for aquifer characterization, key to the successful management of aquifer recharge.
      PubDate: 2017-05-17T11:20:48.52963-05:0
      DOI: 10.1002/2016WR020089
       
  • In situ characterization of wettability alteration and displacement
           mechanisms governing recovery enhancement due to low-salinity
           waterflooding
    • Authors: M. Khishvand; A.H. Alizadeh, I. Oraki Kohshour, M. Piri, R.S. Prasad
      Abstract: A series of micro-scale core-flooding experiments were performed on reservoir core samples at elevated temperature and pressure conditions to develop better insights into wettability alteration and pore-scale displacement mechanisms taking place during low-salinity waterflooding. Two individual miniature core samples were cut from a preserved reservoir whole core, saturated to establish initial reservoir fluid saturation conditions, and subsequently waterflooded with low- and high-salinity brines. A third miniature sister core sample was also cut, solvent-cleaned, and subjected to a dynamic wettability restoration process (to reestablish native state wettability) and then a low-salinity waterflood. All samples were imaged during the experiments using a micro-CT scanner to obtain fluid occupancy maps and measure in-situ oil-water contact angles.The results of the experiments performed on the preserved core samples show a significantly improved performance of low-salinity waterflooding (LSWF) compared to that of high-salinity waterflooding (HSWF). Pore-scale contact angle measurements provide direct evidence of wettability alteration from weakly oil-wet toward weakly water-wet conditions during LSWF, whereas contact angles measured during HSWF remain unchanged. We believe that the reduction in oil-water contact angles toward increased water-wetness lowers the threshold water pressure needed to displace oil from some medium-sized pore elements. Contact angles measured during the dynamic wettability restoration process show an equilibrium wettability state very similar to the initial one observed in the preserved samples. This indicates that drilling fluid contaminants had a negligible effect on the reservoir rock wettability. The experimental results also reveal similarities between saturation trends for the preserved- and restored-LSWF tests.
      PubDate: 2017-05-17T11:20:39.803368-05:
      DOI: 10.1002/2016WR020191
       
  • Geological entropy and solute transport in heterogeneous porous media
    • Authors: Marco Bianchi; Daniele Pedretti
      Abstract: We propose a novel approach to link solute transport behavior to the physical heterogeneity of the aquifer, which we fully characterize with two measurable parameters: the variance of the log K values (σY2), and a new indicator (HR) that integrates multiple properties of the K field into a global measure of spatial disorder or geological entropy. From the results of a detailed numerical experiment considering solute transport in K fields representing realistic distributions of hydrofacies in alluvial aquifers, we identify empirical relationship between the two parameters and the first three central moments of the distributions of arrival times of solute particles at a selected control plane. The analysis of experimental data indicates that the mean and the variance of the solutes arrival times tend to increase with spatial disorder (i.e, HR increasing), while highly skewed distributions are observed in more orderly structures (i.e, HR decreasing) or at higher σY2. We found that simple closed-form empirical expressions of the bivariate dependency of skewness on HR and σY2 can be used to predict the emergence of non-Fickian transport in K fields considering a range of structures and heterogeneity levels, some of which based on documented real aquifers. The accuracy of these predictions and in general the results from this study indicate that a description of the global variability and structure of the K field in terms of variance and geological entropy offers a valid and broadly applicable approach for the interpretation and prediction of transport in heterogeneous porous media.
      PubDate: 2017-05-17T03:26:20.105264-05:
      DOI: 10.1002/2016WR020195
       
  • How are streamflow responses to the El Nino Southern Oscillation affected
           by watershed characteristics?
    • Authors: Joshua S. Rice; Ryan E. Emanuel
      Abstract: Understanding the factors that influence how global climate phenomena, such as the El-Nino Southern Oscillation (ENSO), affect streamflow behavior is an important area of research in the hydrologic sciences. While large scale patterns in ENSO-streamflow relationships have been thoroughly studied, and are relatively well-understood, information is scarce concerning factors that affect variation in ENSO responses from one watershed to another. To this end, we examined relationships between variability in ENSO activity and streamflow for 2731 watersheds across the conterminous U.S. from 1970 to 2014 using a novel approach to account for the intermediary role of precipitation. We applied an ensemble of regression techniques to describe relationships between variability in ENSO activity and streamflow as a function of watershed characteristics including: hydroclimate, topography, geomorphology, geographic location, land cover, soil characteristics, bedrock geology, and anthropogenic influences. We found that variability in watershed scale ENSO – streamflow relationships was strongly related to factors including: precipitation timing and phase, forest cover, and interactions between watershed topography and geomorphology. These, and other influential factors, share in common the ability to affect the partitioning and movement of water within watersheds. Our results demonstrate that the conceptualization of watersheds as signal filters for hydroclimate inputs, commonly applied to short-term rainfall-runoff responses, also applies to long-term hydrologic responses to sources of recurrent climate variability. These results also show that watershed processes, which are typically studied at relatively fine spatial scales, are also critical for understanding continental scale hydrologic responses to global climate.
      PubDate: 2017-05-16T05:40:40.256882-05:
      DOI: 10.1002/2016WR020097
       
  • A new unconditionally stable and consistent quasi-analytical in-stream
           water quality solution scheme for CSTR-basedwater quality simulators
    • Authors: Befekadu Taddesse Woldegiorgis; Ann van Griensven, Fernando Pereira, Willy Bauwens
      Abstract: Most common numerical solutions used in CSTR-based in-stream water quality simulators are susceptible to instabilities and/or solution inconsistencies. Usually, they cope with instability problems by adopting computationally expensive small time steps. However, some simulators use fixed computation time steps and hence do not have the flexibility to do so. This paper presents a novel quasi-analytical solution for CSTR-based water quality simulators of an unsteady system. The robustness of the new method is compared with the commonly used fourth order Runge-Kutta methods, the Euler method and three versions of the SWAT model (SWAT2012, SWAT-TCEQ and ESWAT). The performance of each method is tested for different hypothetical experiments. Besides the hypothetical data, a real case study is used for comparison. The growth factors we derived as stability measures for the different methods and the R-factor -considered as a consistency measureturned out to be very useful for determining the most robust method. The new method outperformed all the numerical methods used in the hypothetical comparisons. The application for the Zenne River (Belgium) shows that the new method provides stable and consistent BOD simulations whereas the SWAT2012 model is shown to be unstable for the standard daily computation time step. The new method unconditionally simulates robust solutions. Therefore, it is a reliable scheme for CSTR-based water quality simulators that use first order reaction formulations.
      PubDate: 2017-05-16T05:40:34.380907-05:
      DOI: 10.1002/2016WR019558
       
  • Beaver-mediated lateral hydrologic connectivity, fluvial carbon and
           nutrient flux, and aquatic ecosystem metabolism
    • Authors: Pam Wegener; Tim Covino, Ellen Wohl
      Abstract: River networks that drain mountain landscapes alternate between narrow and wide valley segments. Within the wide segments, beaver activity can facilitate the development and maintenance of complex, multi-thread planform. Because the narrow segments have limited ability to retain water, carbon, and nutrients, the wide, multi-thread segments are likely important locations of retention. We evaluated hydrologic dynamics, nutrient flux, and aquatic ecosystem metabolism along two adjacent segments of a river network in the Rocky Mountains, Colorado: 1) a wide, multi-thread segment with beaver activity; and, 2) an adjacent (directly upstream) narrow, single-thread segment without beaver activity. We used a mass balance approach to determine the water, carbon, and nutrient source-sink behavior of each river segment across a range of flows. While the single-thread segment was consistently a source of water, carbon, and nitrogen, the beaver impacted multi-thread segment exhibited variable source-sink dynamics as a function of flow. Specifically, the multi-thread segment was a sink for water, carbon, and nutrients during high flows, and subsequently became a source as flows decreased. Shifts in river-floodplain hydrologic connectivity across flows related to higher and more variable aquatic ecosystem metabolism rates along the multi-thread relative to the single-thread segment. Our data suggest that beaver activity in wide valleys can create a physically complex hydrologic environment that can enhance hydrologic and biogeochemical buffering, and promote high rates of aquatic ecosystem metabolism. Given the widespread removal of beaver, determining the cumulative effects of these changes is a critical next step in restoring function in altered river networks.
      PubDate: 2017-05-15T20:45:43.052119-05:
      DOI: 10.1002/2016WR019790
       
  • Reexamining ultrafiltration and solute transport in groundwater
    • Authors: C. E. Neuzil; Mark Person
      Abstract: Geologic ultrafiltration – slowing of solutes with respect to flowing groundwater – poses a conundrum: it is consistently observed experimentally in clay-rich lithologies, but has been difficult to identify in subsurface data. Resolving this could be important for clarifying clay and shale transport properties at large scales as well as interpreting solute and isotope patterns for applications ranging from nuclear waste repository siting to understanding fluid transport in tectonically active environments. Simulations of one-dimensional NaCl transport across ultrafiltering clay membrane strata constrained by emerging data on geologic membrane properties showed different ultrafiltration effects than have often been envisioned. In relatively high permeability advection-dominated regimes, salinity increases occurred mostly within membrane units while their effluent salinity initially fell and then rose to match solute delivery. In relatively low permeability diffusion-dominated regimes, salinity peaked at the membrane upstream boundary and effluent salinity remained low. In both scenarios, however, only modest salinity changes (up to ∼ 3 g l−1) occurred because of self-limiting tendencies; membrane efficiency declines as salinity rises, and although sediment compaction increases efficiency, it is also decreases permeability and allows diffusive transport to dominate. It appears difficult for ultrafiltration to generate brines as speculated, but widespread and less extreme ultrafiltration effects in the subsurface could be unrecognized. Conditions needed for ultrafiltration are present in settings that include topographically-driven flow systems, confined aquifer systems subjected to injection or withdrawal, compacting basins, and accretionary complexes.
      PubDate: 2017-05-15T20:45:40.203796-05:
      DOI: 10.1002/2017WR020492
       
  • Parameterization and prediction of manoparticles transport in porous
           media: A reanalysis using artificial neural network
    • Authors: Peyman Babakhani; Jonathan Bridge, Ruey-an Doong, Tanapon Phenrat
      Abstract: The continuing rapid expansion of industrial and consumer processes based on nanoparticles (NP) necessitates a robust model for delineating their fate and transport in groundwater. An ability to reliably specify the full parameter set for prediction of NP transport using continuum models is crucial. In this paper we report the reanalysis of a dataset of 493 published column experiment outcomes together with their continuum modelling results. Experimental properties were parametrized into 20 factors which are commonly available. They were then used to predict 5 key continuum model parameters as well as the effluent concentration via artificial neural network (ANN)-based correlations. The Partial Derivatives (PaD) technique and Monte Carlo method were used for the analysis of sensitivities and model-produced uncertainties, respectively. The outcomes shed light on several controversial relationships between the parameters, e.g., it was revealed that the trend of Katt with average pore water velocity was positive. The resulting correlations, despite being developed based on a ‘black-box' technique, (ANN), were able to explain the effects of theoretical parameters such as critical deposition concentration (CDC), even though these parameters were not explicitly considered in the model. Porous media heterogeneity was considered as a parameter for the first time, and showed sensitivities higher than those of dispersivity. The model performance was validated well against subsets of the experimental data and was compared with current models. The robustness of the correlation matrices was not completely satisfactory, since they failed to predict the experimental breakthrough curves (BTCs) at extreme values of ionic strengths.
      PubDate: 2017-05-13T03:47:11.235226-05:
      DOI: 10.1002/2016WR020358
       
  • Hyporheic zone influences on concentration-discharge relationships in a
           headwater sandstone stream
    • Authors: Beth Hoagland; Tess A. Russo, Xin Gu, Lillian Hill, Jason Kaye, Brandon Forsythe, Susan L. Brantley
      Abstract: Complex subsurface flow dynamics impact the storage, routing, and transport of water and solutes to streams in headwater catchments. Many of these hydrogeologic processes are indirectly reflected in observations of stream chemistry responses to rain events, also known as concentration-discharge (CQ) relations. Identifying the relative importance of subsurface flows to stream CQ relationships is often challenging in headwater environments due to spatial and temporal variability. Therefore, this study combines a diverse set of methods, including tracer injection tests, cation exchange experiments, geochemical analyses, and numerical modeling, to map groundwater-surface water interactions along a first-order, sandstone stream (Garner Run) in the Appalachian Mountains of central Pennsylvania. The primary flowpaths to the stream include preferential flow through the unsaturated zone (“interflow”), flow discharging from a spring, and groundwater discharge. Garner Run stream inherits geochemical signatures from geochemical reactions occurring along each of these flowpaths. In addition to end-member mixing effects on CQ, we find that the exchange of solutes, nutrients, and water between the hyporheic zone and main stream channel is a relevant control on the chemistry of Garner Run. CQ relationships for Garner Run were compared to prior results from a nearby headwater catchment overlying shale bedrock (Shale Hills). At the sandstone site, solutes associated with organo-mineral associations in the hyporheic zone influence CQ, while CQ trends in the shale catchment are affected by preferential flow through hillslope swales. The difference in CQ trends document how the lithology and catchment hydrology control CQ relationships.
      PubDate: 2017-05-12T19:50:41.249598-05:
      DOI: 10.1002/2016WR019717
       
  • Improving degradation of benzotriazoles by applying chaotic advection in
           Managed Aquifer Recharge in randomly heterogeneous porous media
    • Authors: P. Rodríguez-Escales; D. Fernández-García, J. Drechsel, A. Folch, X. Sanchez-Vila
      Abstract: Improving degradation rates of emerging organic compounds (EOCs) in groundwater is still a challenge. Although their degradation is not fully understood, it has been observed that some substances are preferably degraded under specific redox conditions. The coupling of Managed Aquifer Recharge with soil aquifer remediation treatment, by placing a reactive layer containing organic matter at the bottom of the infiltration pond, is a promising technology to improve the rate of degradation of EOCs. Its success is based on assuming that recharged water and groundwater get well mixed, which is not always true. It has been demonstrated that mixing can be enhanced by inducing chaotic advection through extraction-injection-engineering. In this work we analyze how chaotic advection might enhance the spreading of redox conditions with the final aim of improving degradation of a mix of benzotriazoles: benzotriazole, 5-methyl-benzotriazole, and 5-chloro-benzotriazole. The degradation of the first two compounds was fastest under aerobic conditions whereas the third compound was best degraded under denitrification conditions. We developed a reactive transport model that describes how a recharged water rich in organic matter mixes with groundwater, how this organic matter is oxidized by different electron acceptors, and how the benzotriazoles are degraded attending for the redox state. The model was tested in different scenarios of recharge, both in homogenous and in heterogenous media. It was found that chaotic flow increases the spreading of the plume of recharged water. Consequently, different redox conditions coexist at a given time, facilitating the degradation of EOCs.
      PubDate: 2017-05-12T19:35:42.388198-05:
      DOI: 10.1002/2016WR020333
       
  • Raindrop interaction in interrill erosion for steady rainfalls: A
           probabilistic approach
    • Authors: A. Nouhou Bako; F. Darboux, F. James, C. Lucas
      Abstract: The main processes involved in interrill erosion are soil particles detachment and transport. Detachment is caused by shear stresses created by the impacts of raindrops. After sediments are lifted in the water layer, they are transported over a distance that depends on their settling velocities and the water flow velocity. This study calculates the probabilities of interactions between raindrops during soil detachment, and between raindrops and particles during their sedimentation. Raindrops are assumed to be consistent with the Poisson process and their densities are described by raindrop size distribution functions (Marshall-Palmer, Gamma and Lognormal laws). Interaction probabilities are calculated based on characteristic time and length scales of the shear stresses and the perturbation created by the raindrop impact inside the water layer.Under the hypothesis of a constant rainfall intensity, the results show that, during soil detachment, raindrops are almost independent. Thus, the total amount of soil detached by a rainfall is practically the sum of soil detached by its individual raindrops. Whereas during sediment transport, the probability of interaction between raindrops and settling particles is very high whatever the rainfall intensity and particle size, emphasizing the need to study further the interaction between raindrops and settling particles.
      PubDate: 2017-05-12T19:35:33.479914-05:
      DOI: 10.1002/2017WR020568
       
  • A theoretically consistent stochastic cascade for temporal disaggregation
           of intermittent rainfall
    • Authors: F. Lombardo; E. Volpi, D. Koutsoyiannis, F. Serinaldi
      Abstract: Generating fine-scale time series of intermittent rainfall that are fully consistent with any given coarse-scale totals is a key and open issue in many hydrological problems. We propose a stationary disaggregation method that simulates rainfall time series with given dependence structure, wet/dry probability, and marginal distribution at a target finer (lower-level) time scale, preserving full consistency with variables at a parent coarser (higher-level) time scale. We account for the intermittent character of rainfall at fine time scales by merging a discrete stochastic representation of intermittency and a continuous one of rainfall depths. This approach yields a unique and parsimonious mathematical framework providing general analytical formulations of mean, variance, and autocorrelation function (ACF) for a mixed-type stochastic process in terms of mean, variance, and ACFs of both continuous and discrete components, respectively. To achieve the full consistency between variables at finer and coarser time scales in terms of marginal distribution and coarse-scale totals, the generated lower-level series are adjusted according to a procedure that does not affect the stochastic structure implied by the original model. To assess model performance, we study rainfall process as intermittent with both independent and dependent occurrences, where dependence is quantified by the probability that two consecutive time intervals are dry. In either case, we provide analytical formulations of main statistics of our mixed-type disaggregation model and show their clear accordance with Monte Carlo simulations. An application to rainfall time series from real world is shown as a proof of concept.
      PubDate: 2017-05-12T19:30:35.923673-05:
      DOI: 10.1002/2017WR020529
       
  • High-resolution flow characterization close to the sediment-water
           interface in a run of the river reservoir
    • Authors: Andreas Brand; Christian Noss
      Abstract: A bistatic high-resolution acoustic profiler was used in order to characterize the lowermost boundary layer of a run of the river reservoir. The profiler allows determining the statistics of the three-dimensional flow field at a single point (sweet spot) as well as the measurement of the time averaged flow velocity profiles at 1 mm resolution around the sweet spot. Therefore, in addition to the flow statistics provided by single point acoustic Doppler profilers, mixing coefficients as well as production of turbulent kinetic energy can be calculated using a single device. Fitting of semiempirical relations to observed cospectra allowed eliminating artifacts as they result from coordinate system rotation during calculation of Reynolds stress profiles at millimeter resolution. While most parameters showed characteristics of a constant stress layer, length scales indicated anisotropy of the turbulent flow. Under these anisotropic near wall conditions, we found that the use of the commonly accepted Kolmogorov constants for the determination of dissipation rates using the inertial dissipation method is not valid any more. Instead, these constants vary with distance from the sediment water interface. We provide evidence that coefficients determined by numerical simulations are the appropriate choice also in field applications. In addition we resolved the viscous boundary layer close to the sediment-water interface in high resolution (1 mm) profiles and identified a double logarithmic layer above 1.5 cm at one location. The discrepancy of the scales as well as the double logarithmic layer suggests the existence of roughness elements upstream of the measurement sites.
      PubDate: 2017-05-12T10:35:37.002689-05:
      DOI: 10.1002/2016WR020203
       
  • Editorial: A vision for Water Resources Research
    • Authors: Martyn P. Clark; Jean A. Bahr, Marc F. P. Bierkens, Ximing Cai, Terri S. Hogue, Charles H. Luce, Jessica D. Lundquist, D. Scott Mackay, H.J. (Ilja) van Meerveld, Harihar Rajaram, Xavier Sanchez-Vila, Peter A. Troch
      Abstract: Water Resources Research (WRR) continues to evolve as the team of international editors begins a new 4-year term of service. In this Editorial we summarize the importance of WRR in the hydrologic sciences, the challenges ahead, and the plans for the future of the journal.
      PubDate: 2017-05-12T08:53:20.580489-05:
      DOI: 10.1002/2017WR021050
       
  • Validating a universal model of particle transport lengths with laboratory
           measurements of suspended grain motions
    • Authors: Suleyman Naqshband; Brandon McElroy, Robert C. Mahon
      Abstract: The mechanics of sediment transport are of fundamental importance for fluvio-deltaic morphodynamics. The present study focuses on quantifying particle motions and trajectories across a wide range of flow conditions. In particular, a continuous model is presented that predicts particle travel distances for saltation and suspension based on Rouse number and relative grain roughness. By utilizing a series of 8 video cameras in a plexiglass flume direct measurements of the distributions of particle travel distances (excursion lengths) were obtained. To this end, experiments were carried out in dark under black lights with fluorescent painted plastic and quartz sand particles. For relatively high Rouse numbers indicating bed load dominant transport regime (P ≥ 2.5), particle motion is governed by the effect of gravitational forces (settling velocities) and measured excursion lengths closely follow a Gaussian distribution. For P = 2.5, particle motion is equally subjected to both gravitational and turbulent forces. Consequently, measured excursion lengths exhibit a bi-modal distribution with two distinct peaks. As turbulent fluctuations increase and dominate particle motion over gravity (P 
      PubDate: 2017-05-08T08:52:04.005955-05:
      DOI: 10.1002/2016WR020024
       
  • Processes governing arsenic retardation on Pleistocene sediments:
           Adsorption experiments and model-based analysis
    • Authors: Bhasker Rathi; Harald Neidhardt, Michael Berg, Adam Siade, Henning Prommer
      Abstract: In many countries of south/south-east Asia, reliance on Pleistocene aquifers for the supply of low-arsenic groundwater has created the risk of inducing migration of high-arsenic groundwater from adjacent Holocene aquifers. Adsorption of arsenic onto mineral surfaces of Pleistocene sediments is an effective attenuation mechanism. However, little is known about the sorption under anoxic conditions, in particular the behavior of arsenite. We report the results of anoxic batch experiments investigating arsenite (1–25 µmol/L) adsorption onto Pleistocene sediments under a range of field-relevant conditions. The sorption of arsenite was non-linear and decreased with increasing phosphate concentrations (3–60 µmol/L) while pH (range 6–8) had no effect on total arsenic sorption. To simulate the sorption experiments, we developed surface complexation models of varying complexity. The simulated concentrations of arsenite, arsenate and phosphate were in good agreement for the isotherm and phosphate experiments while secondary geochemical processes affected the pH experiments. For the latter, the model-based analysis suggests that the formation of solution complexes between organic buffers and Mn(II) ions promoted the oxidation of arsenite involving naturally-occurring Mn-oxides. Upscaling the batch experiment model to a reactive transport model for Pleistocene aquifers demonstrates strong arsenic retardation and could have useful implications in the management of arsenic-free Pleistocene aquifers.
      PubDate: 2017-05-08T08:51:44.912294-05:
      DOI: 10.1002/2017WR020551
       
  • Valuing environmental services provided by local stormwater management
    • Authors: Daniel A. Brent; Lata Gangadharan, Allison Lassiter, Anke Leroux, Paul A. Raschky
      Abstract: The management of stormwater runoff via distributed green infrastructures delivers a number of environmental services that go beyond the reduction of flood risk, which has been the focus of conventional stormwater systems. Not all of these services may be equally valued by the public, however. This paper estimates households' willingness to pay (WTP) for improvements in water security, stream health, recreational and amenity values, as well as reduction in flood risk and urban heat island effect. We use data from nearly 1,000 personal interviews with residential homeowners in Melbourne and Sydney, Australia. Our results suggest that the WTP for the highest levels of all environmental services is A$799 per household per year. WTP is mainly driven by residents valuing improvements in local stream health, exemptions in water restrictions, the prevention of flash flooding, and decreased peak urban temperatures respectively at A$297, A$244, A$104 and A$65 per year. We further conduct a benefit transfer analysis and find that the WTP and compensating surplus are not significantly different between the study areas. Our findings provide additional support that stormwater management via green infrastructures have large non-market benefits and that, under certain conditions, benefit values can be transferred to different locations.
      PubDate: 2017-05-08T08:51:35.875623-05:
      DOI: 10.1002/2016WR019776
       
  • Inferring hydraulic properties of alpine aquifers from the propagation of
           diurnal snowmelt signals
    • Authors: B. L. Kurylyk; M. Hayashi
      Abstract: Alpine watersheds source major rivers throughout the world and supply essential water for irrigation, human consumption, and hydroelectricity. Coarse depositional units in alpine watersheds can store and transmit significant volumes of groundwater and thus augment stream discharge during the dry season. These environments are typically data scarce, which has limited the application of physically-based models to investigate hydrologic sensitivity to environmental change.This study focuses on a coarse alpine talus unit within the Lake O'Hara watershed in the Canadian Rockies. We investigate processes controlling the hydrologic functioning of the talus unit using field observations and a numerical groundwater flow model driven with a distributed snowmelt model. The model hydraulic parameters are adjusted to investigate how these properties influence the propagation of snowmelt-induced diurnal signals. The model results expectedly demonstrate that diurnal signals at the talus outlet are progressively damped and lagged with lower hydraulic conductivity and higher specific yield. The simulations further indicate that the lag can be primarily controlled by a higher hydraulic conductivity upper layer, whereas the damping can be strongly influenced by a lower hydraulic conductivity layer along the base of the talus. The simulations specifically suggest that the talus slope can be represented as a two layer system with a high conductivity zone (0.02 m s−1) overlying a 10 cm thick lower conductivity zone (0.002 m s−1). This study demonstrates that diurnal signals can be used to elucidate the hydrologic functioning and hydraulic properties of shallow aquifers and thus aid in the parameterization of hydrological models.
      PubDate: 2017-05-08T08:51:28.464843-05:
      DOI: 10.1002/2016WR019651
       
  • A process-based insight into nonstationarity of the probability
           distribution of annual runoff
    • Authors: Cong Jiang; Lihua Xiong, Shenglian Guo, Jun Xia, Chong-Yu Xu
      Abstract: In this paper, a process-based analytical derivation approach is proposed to perform a nonstationary analysis for annual runoff distribution by taking into account the information of nonstationarities in both hydrological inputs and runoff generation processes. Under the Budyko hypothesis, annual runoff is simulated as a formulation of hydrological inputs (annual precipitation and potential evaporation) using an annual runoff model based on the Fu equation with a parameter w accounting for the runoff generation processes. The nonstationarity of the runoff generation process is captured by the dynamic Fu-equation parameter w. Then the multivariate joint probability distribution among the hydrological inputs, the Fu-equation parameter w, and the runoff model error k is constructed based on the nonstationary analysis for both the hydrological inputs and w. Finally, the annual runoff distribution is derived by integrating the multivariate joint probability density function. The derived distribution by the process-based analytical derivation approach performs well in fitting distributions of the annual runoffs from both the Yangtze River and Yellow River, China. For most study watersheds in these two basins, the derived annual runoff distributions are found to be nonstationary, due to the nonstationarities in hydrological inputs (mainly potential evaporation) or the Fu-equation parameter w.
      PubDate: 2017-05-08T08:51:23.564882-05:
      DOI: 10.1002/2016WR019863
       
  • Evaluating the role of watershed properties in long-term water balance
           through a Budyko equation based on two-stage partitioning of precipitation
           
    • Authors: Yin Tang; Dingbao Wang
      Abstract: In this paper, a four-parameter Budyko equation is derived for mean annual water balance by applying the proportionality relationship to a two-stage partitioning of precipitation. The four dimensionless parameters include the Horton index (H, defined as the ratio of evaporation to total wetting) and λ (the ratio of initial evaporation to total wetting) for slow runoff, and β (the ratio of initial wetting to total wetting) and γ (the ratio of total wetting to its potential) for fast runoff. The derived four-parameter equation balances model parsimony and representation of dominant hydrologic processes, and provides a framework to disentangle the roles of climate variability, vegetation, soil and topography on long-term water balance in gauged watersheds. The four parameters are determined for 165 watersheds by using observations of precipitation, potential evaporation, streamflow, and soil properties. Based on the principal component regression analysis, average time interval between rainfall events, slope, normalized difference vegetation index, and wilting point are identified as the dominant controlling factors on H and λ; saturated hydraulic conductivity and the difference between field capacity and residual soil moisture are identified as the dominant controlling factors on β; and γ is controlled by effective soil water storage capacity, frequency of rainfall events, and climate seasonality. The combination of four-parameter Budyko equation and the principal component regression equations provides a model to assess the long-term responses of evaporation and runoff to climate and watershed property changes in ungauged watersheds.
      PubDate: 2017-05-08T08:51:05.432207-05:
      DOI: 10.1002/2016WR019920
       
  • The Role of Rating Curve Uncertainty in Real-Time Flood Forecasting
    • Authors: David Ocio; Nataliya Le Vine, Ida Westerberg, Florian Pappenberger, Wouter Buytaert
      Abstract: Data assimilation has been widely tested for flood forecasting, although its use in operational systems is mainly limited to a simple statistical error correction. This can be due to the complexity involved in making more advanced formal assumptions about the nature of the model and measurement errors. Recent advances in the definition of rating curve uncertainty allow estimating a flow measurement error that includes both aleatory and epistemic uncertainties more explicitly and rigorously than in the current practice. The aim of this study is to understand the effect such a more rigorous definition of the flow measurement error has on real-time data assimilation and forecasting. This study, therefore, develops a comprehensive probabilistic framework that considers the uncertainty in model forcing data, model structure, and flow observations. Three common data assimilation techniques are evaluated: 1) Autoregressive error correction, 2) Ensemble Kalman Filter, and 3) Regularised Particle Filter, and applied to two locations in the flood-prone Oria catchment in the Basque Country, northern Spain. The results show that, although there is a better match between the uncertain forecasted and uncertain true flows, there is a low sensitivity for the threshold exceedances used to issue flood warnings. This suggests that a standard flow measurement error model, with a spread set to a fixed flow fraction, represents a reasonable trade-off between complexity and realism. Standard models are therefore recommended for operational flood forecasting for sites with well-defined stage–discharge curves that are based on a large range of flow observations.
      PubDate: 2017-05-08T08:50:58.935094-05:
      DOI: 10.1002/2016WR020225
       
  • Characterizing hyporheic exchange processes using high frequency
           electrical conductivity-discharge relationships on sub-hourly to
           interannual timescales
    • Authors: Joel G. Singley; Adam N. Wlostowski, Anna J. Bergstrom, Eric R. Sokol, Christa L. Torrens, Chris Jaros, Colleen E. Wilson, Patrick J. Hendrickson, Michael N. Gooseff
      Abstract: Concentration-discharge (C-Q) relationships are often used to quantify source water contributions and biogeochemical processes occurring within catchments, especially during discrete hydrological events. Yet, the interpretation of C-Q hysteresis is often confounded by complexity of the critical zone, such as numerous source waters and hydrochemical non-stationarity. Consequently, researchers must often ignore important runoff pathways and geochemical sources/sinks, especially the hyporheic zone because it lacks a distinct hydrochemical signature. Such simplifications limit efforts to identify processes responsible for the transience of C-Q hysteresis over time. To address these limitations, we leverage the hydrologic simplicity and long-term, high-frequency Q and electrical conductivity (EC) data from streams in the McMurdo Dry Valleys, Antarctica. In this two end-member system, EC can serve as a proxy for the concentration of solutes derived from the hyporheic zone. We utilize a novel approach to decompose loops into sub-hysteretic EC-Q dynamics to identify individual mechanisms governing hysteresis across a wide range of timescales. We find that hydrologic and hydraulic processes govern EC response to diel and seasonal Q variability and that the effects of hyporheic mixing processes on C-Q transience differ in short and long streams. We also observe that variable hyporheic turnover rates govern EC-Q patterns at daily to interannual timescales. Lastly, sub-hysteretic analysis reveals a period of interannual freshening of glacial meltwater streams related to the effects of unsteady flow on hyporheic exchange. The sub-hysteretic analysis framework we introduce may be applied more broadly to constrain the processes controlling C-Q transience and advance understanding of catchment evolution.
      PubDate: 2017-05-08T08:50:48.049312-05:
      DOI: 10.1002/2016WR019739
       
  • The effect of sampling effort on estimates of methane ebullition from peat
    • Authors: Jorge A. Ramirez; Andy J. Baird, Tom J. Coulthard
      Abstract: We investigated the effect of sample size and sampling duration on methane bubble flux (ebullition) estimates from peat using a computer model. A field scale (10 m), seasonal (> 100 days) simulation of ebullition from a two-dimensional structurally-varying peat profile was modelled at fine spatial resolution (1 mm × 1 mm). The spatial and temporal scale of this simulation was possible because of the computational efficiency of the reduced complexity approach that was implemented, and patterns of simulated ebullition were consistent with those found in the field and laboratory. The simulated ebullition from the peat profile suggested that decreases in peat porosity – which cause increases in gas storage – produce ebullition that becomes increasingly patchy in space and erratic in time. By applying different amounts of spatial and temporal sampling effort it was possible to determine the uncertainty in ebullition estimates from the peatland. The results suggest that traditional methods to measure ebullition can equally overestimate and underestimate flux by 20% and large ebullition events can lead to large overestimations of flux when sampling effort is low. Our findings support those of field studies, and we recommend that ebullition should be measured frequently (hourly to daily) and at many locations (n > 14).
      PubDate: 2017-05-08T08:50:38.892488-05:
      DOI: 10.1002/2017WR020428
       
  • Quantifying model structural error: Efficient Bayesian calibration of a
           regional groundwater flow model using surrogates and a data-driven error
           model
    • Authors: Tianfang Xu; Albert J. Valocchi, Ming Ye, Feng Liang
      Abstract: Groundwater model structural error is ubiquitous, due to simplification and/or misrepresentation of real aquifer systems. During model calibration, the basic hydrogeological parameters may be adjusted to compensate for structural error. This may result in biased predictions when such calibrated models are used to forecast aquifer responses to new forcing. We investigate the impact of model structural error on calibration and prediction of a real-world groundwater flow model, using a Bayesian method with a data-driven error model [Xu and Valocchi, 2015a] to explicitly account for model structural error. The error-explicit Bayesian method jointly infers model parameters and structural error and thereby reduces parameter compensation. In this study, Bayesian inference is facilitated using high performance computing and fast surrogate models (based on machine learning techniques) as a substitute for the computationally expensive groundwater model. We demonstrate that with explicit treatment of model structural error, the Bayesian method yields parameter posterior distributions that are substantially different from those derived using classical Bayesian calibration that does not account for model structural error. We also found that the error-explicit Bayesian method gives significantly more accurate prediction along with reasonable credible intervals. Finally, through variance decomposition we provide a comprehensive assessment of prediction uncertainty contributed from parameter, model structure, and measurement uncertainty. The results suggest that the error-explicit Bayesian approach provides a solution to real-world modeling applications for which data support the presence of model structural error, yet model deficiency cannot be specifically identified or corrected.
      PubDate: 2017-05-08T08:50:33.034177-05:
      DOI: 10.1002/2016WR019831
       
  • Effects of spatially distributed sectoral water management on the
           redistribution of water resources in an integrated water model
    • Authors: Nathalie Voisin; Mohamad Hejazi, Ruby Leung, Lu Liu, Maoyi Huang, Hong-Yi Li, Teklu Tesfa
      Abstract: Realistic representations of sectoral water withdrawals and consumptive demands and their allocation to surface and groundwater sources are important for improving modeling of the integrated water cycle. To inform future model development, we enhance the representation of sectoral water management in a regional Earth system (ES) model with a spatially distributed allocation of sectoral water demands simulated by a regional integrated assessment (IA) model to surface and groundwater systems. The integrated modeling framework (IA-ES) is evaluated by analyzing the simulated regulated flow and sectoral supply deficit in major hydrologic regions of the conterminous U.S, which differ from ES studies looking at water storage variations. Decreases in historical supply deficit are used as metrics to evaluate IA-ES model improvement in representating the complex sectoral human activities for assessing future adaptation and mitigation strategies. We also assess the spatial changes in both regulated flow and unmet demands, for irrigation and non-irrigation sectors, resulting from the individual and combined additions of groundwater and return flow modules. Results show that groundwater use has a pronounced regional and sectoral effect by reducing water supply deficit. The effects of sectoral return flow exhibit a clear east-west contrast in the hydrologic patterns, so the return flow component combined with the IA sectoral demands is a major driver for spatial redistribution of water resources and water deficits in the U.S. Our analysis highlights the need for spatially distributed sectoral representation of water management to capture the regional differences in inter-basin redistribution of water resources and deficits.
      PubDate: 2017-05-08T08:35:37.70385-05:0
      DOI: 10.1002/2016WR019767
       
  • Forward and back diffusion through argillaceous formations
    • Authors: Minjune Yang; Michael D. Annable, James W. Jawitz
      Abstract: The exchange of solutes between aquifers and lower-permeability argillaceous formations is of considerable interest for solute and contaminant fate and transport. We present a synthesis of analytical solutions for solute diffusion between aquifers and single aquitard systems, validated in well-controlled experiments, and applied to several datasets from laboratory and field-scale problems with diffusion time and length scales ranging from 10−2-108 years and 10−2-102 m. One-dimensional diffusion models were applied using the method of images to consider the general cases of a finite aquitard bounded by two aquifers at the top and bottom, or a semi-infinite aquitard bounded by an aquifer. The simpler semi-infinite equations are appropriate for all domains with dimensionless relative diffusion length, ZD 
      PubDate: 2017-05-03T18:55:28.593317-05:
      DOI: 10.1002/2016WR019874
       
  • Geochemical evolution of the Critical Zone across variable time scales
           informs concentration-discharge relationships: Jemez River Basin Critical
           Zone Observatory
    • Authors: Jennifer C. McIntosh; Courtney Schaumberg, Julia Perdrial, Adrian Harpold, Angélica Vázquez-Ortega, Craig Rasmussen, David Vinson, Xavier Zapata-Rios, Paul D. Brooks, Thomas Meixner, Jon Pelletier, Louis Derry, Jon Chorover
      Abstract: This study investigates the influence of water, carbon and energy fluxes on solute production and transport through the Jemez Critical Zone (CZ) and impacts on C-Q relationships over variable spatial and temporal scales. Chemical depletion-enrichment profiles of soils, combined with regolith thickness and groundwater data indicate the importance to stream hydrochemistry of incongruent dissolution of silicate minerals during deep bedrock weathering, which is primarily limited by water fluxes, in this highly fractured, young volcanic terrain. Under high flow conditions (e.g., spring snowmelt), wetting of soil and regolith surfaces and presence of organic acids promote mineral dissolution and provide a constant supply of base cations, Si, and DIC to soil water and groundwater. Mixing of waters from different hydrochemical reservoirs in the near stream environment during ‘wet' periods leads to the chemostatic behavior of DIC, base cations, and Si in stream flow. Metals transported by organic matter complexation (i.e., Ge, Al) and/or colloids (i.e., Al) during periods of soil saturation and lateral connectivity to the stream display a positive relationship with Q. Variable Si-Q relationships, under all but the highest flow conditions, can be explained by non-conservative transport and precipitation of clay minerals, which influences long- versus short-term Si weathering fluxes. By combining measurements of the CZ obtained across different spatial and temporal scales, we were able to constrain weathering processes in different hydrological reservoirs that may be flushed to the stream during hydrologic events, thereby informing C-Q relationships.
      PubDate: 2017-05-02T19:35:37.307325-05:
      DOI: 10.1002/2016WR019712
       
  • Ephemeral and intermittent runoff generation processes in a low relief,
           highly weathered catchment
    • Authors: Margaret A. Zimmer; Brian L. McGlynn
      Abstract: Most field-based approaches that address runoff generation questions have been conducted in steep landscapes with shallow soils. Runoff generation processes in low relief landscapes with deep soils remain less understood. We addressed this by characterizing dominant runoff generating flowpaths by monitoring the timing and magnitude of precipitation, runoff, shallow soil moisture, and shallow and deep groundwater dynamics in a 3.3 hectare ephemeral-to-intermittent drainage network in the Piedmont region of North Carolina, USA. This Piedmont region is gently sloped with highly weathered soils characterized by shallow impeding layers due to decreases in saturated hydraulic conductivity with depth. Our results indicated two dominant catchment storage states driven by seasonal evapotranspiration. Within these states, distinct flowpaths were activated, resulting in divergent hydrograph recessions. Groundwater dynamics during precipitation events with different input characteristics and contrasting storage states showed distinct shallow and deep groundwater flowpath behavior could produce similar runoff magnitudes. During an event with low antecedent storage, activation of a shallow, perched, transient water table dominated runoff production. During an event with high antecedent storage, the deeper water table activated shallow flowpaths by rising into the shallow transmissive soil horizons. Despite these differing processes, the relationship between active surface drainage length (ASDL) and runoff was consistent. Hysteretic behavior between ASDL and runoff suggested that while seasonal ASDLs can be predicted based on runoff, the mechanisms and source areas producing flow can be highly variable and not easily estimated from runoff alone. These processes and flowpaths have significant implications for stream chemistry across seasons and storage states.
      PubDate: 2017-05-02T19:30:58.387939-05:
      DOI: 10.1002/2016WR019742
       
  • A two-dimensional analytical model of vapor intrusion involving vertical
           heterogeneity
    • Authors: Yijun Yao; Iason Verginelli, Eric M. Suuberg
      Abstract: In this work, we present an analytical chlorinated vapor intrusion (CVI) model that can estimate source-to-indoor air concentration attenuation by simulating two-dimensional (2-D) vapor concentration profile in vertically heterogeneous soils overlying a homogenous vapor source. The analytical solution describing the 2-D soil gas transport was obtained by applying a modified Schwarz–Christoffel mapping method. A partial field validation showed that the developed model provides results (especially in terms of indoor emission rates) in line with the measured data from a case involving a building overlying a layered soil. In further testing, it was found that the new analytical model can very closely replicate the results of three-dimensional (3-D) numerical models at steady state in scenarios involving layered soils overlying homogenous groundwater sources. By contrast, by adopting a two-layer approach (capillary fringe and vadose zone) as employed in the EPA implementation of the Johnson and Ettinger model, the spatially and temporally averaged indoor concentrations in the case of groundwater sources can be higher than the ones estimated by the numerical model up to two orders of magnitude. In short, the model proposed in this work can represent an easy-to-use tool that can simulate the subsurface soil gas concentration in layered soils overlying a homogenous vapor source while keeping the simplicity of an analytical approach that requires much less computational effort.
      PubDate: 2017-05-02T10:59:26.275321-05:
      DOI: 10.1002/2016WR020317
       
  • A geostatistics-informed hierarchical sensitivity analysis method for
           complex groundwater flow and transport modeling
    • Authors: Heng Dai; Xingyuan Chen, Ming Ye, Xuehang Song, John M. Zachara
      Abstract: Sensitivity analysis is an important tool for development and improvement of mathematical models, especially for complex systems with a high dimension of spatially correlated parameters. Variance-based global sensitivity analysis has gained popularity because it can quantify the relative contribution of uncertainty from different sources. However, its computational cost increases dramatically with the complexity of the considered model and the dimension of model parameters. In this study we developed a new sensitivity analysis method that integrates the concept of variance-based method with a hierarchical uncertainty quantification framework. Different uncertain inputs are grouped and organized into a multi-layer framework based on their characteristics and dependency relationships to reduce the dimensionality of the sensitivity analysis. A set of new sensitivity indices are defined for the grouped inputs using the variance decomposition method. Using this methodology, we identified the most important uncertainty source for a dynamic groundwater flow and solute transport model at the Department of Energy (DOE) Hanford site. The results indicate that boundary conditions and permeability field contribute the most uncertainty to the simulated head field and tracer plume, respectively. The relative contribution from each source varied spatially and temporally. By using a geostatistical approach to reduce the number of realizations needed for the sensitivity analysis, the computational cost of implementing the developed method was reduced to a practically manageable level. The developed sensitivity analysis method is generally applicable to a wide range of hydrologic and environmental problems that deal with high-dimensional spatially-distributed input variables.
      PubDate: 2017-04-29T12:00:11.82816-05:0
      DOI: 10.1002/2016WR019756
       
  • Hydrologic controls on junction angle of river networks
    • Authors: Milad Hooshyar; Arvind Singh, Dingbao Wang
      Abstract: The formation and growth of river channels and their network evolution are governed by the erosional and depositional processes operating on the landscape due to the movement of water. The branching angles, i.e., the angle between two adjoining channels, in drainage networks are important features related to the network topology and contain valuable information about the forming mechanisms of the landscape. Based on the channel networks extracted from 1 m Digital Elevation Models of 120 catchments with minimal human impacts across the United States, we show that the junction angles have two distinct modes with α1-≈49.5° and α2-≈75.0°. The observed angles are physically explained as the optimal angles that result in minimum energy dissipation and are linked to the exponent characterizing the slope-area curve. Our findings suggest that the flow regimes, debris-flow dominated or fluvial, have distinct characteristic angles which are functions of the scaling exponent of the slope-area curve. These findings enable us to understand the geomorphic signature of hydrologic processes on drainage networks and develop more refined landscape evolution models.
      PubDate: 2017-04-29T10:24:26.417507-05:
      DOI: 10.1002/2016WR020267
       
  • Ecohydrological interfaces as hotspots of ecosystem processes
    • Authors: Stefan Krause; Jörg Lewandowski, Nancy B. Grimm, David M. Hannah, Gilles Pinay, Karlie McDonald, Eugènia Martí, Alba Argerich, Laurent Pfister, Julian Klaus, Tom Battin, Scott T. Larned, Jacob Schelker, Jan Fleckenstein, Christian Schmidt, Michael O Rivett, Glenn Watts, Francesc Sabater, Albert Sorolla, Valentina Turk
      Abstract: The movement of water, matter, organisms, and energy can be altered substantially at ecohydrological interfaces, the dynamic transition zones that often develop within ecotones or boundaries between adjacent ecosystems. Interdisciplinary research over the last two decades has indicated that ecohydrological interfaces are often “hotspots” of ecological, biogeochemical, and hydrological processes and may provide refuge for biota during extreme events. Ecohydrological interfaces can have significant impact on global hydrological and biogeochemical cycles, biodiversity, pollutant removal, and ecosystem resilience to disturbance. The organisational principles (i.e., the drivers and controls) of spatially and temporally variable processes at ecohydrological interfaces are poorly understood and require the integrated analysis of hydrological, biogeochemical, and ecological processes. Our rudimentary understanding of the interactions between different drivers and controls critically limits our ability to predict complex system responses to change.In this paper we explore similarities and contrasts in the functioning of diverse freshwater ecohydrological interfaces across spatial and temporal scales. We use this comparison to develop an integrated, interdisciplinary framework, including a roadmap for analysing ecohydrological processes and their interactions in ecosystems. We argue that, in order to fully account for their non-linear process dynamics, ecohydrological interfaces need to be conceptualised as unique, spatially and temporally dynamic entities, which represents a step change from their current representation as boundary conditions at investigated ecosystems.
      PubDate: 2017-04-29T10:24:20.299483-05:
      DOI: 10.1002/2016WR019516
       
  • Evaluating climate and soil effects on regional soil moisture spatial
           variability using EOFs
    • Authors: Tiejun Wang; Trenton E. Franz, Ruopu Li, Jinsheng You, Martha D. Shulski, Chittaranjan Ray
      Abstract: Soil moisture is an important state variable in terrestrial water cycles; however, only few studies are available on regional soil moisture spatial variability (SMSV), which yielded inconsistent findings about regional controls on SMSV. Here, long-term soil moisture data were obtained from the Automated Weather Data Network and Soil Climate Analysis Network in three regions with different climate regimes across the continental U.S. Comprehensive datasets were compiled to examine regional controls on SMSV using the method of Empirical Orthogonal Function. One dominant spatial structure (EOF1) of soil moisture was found in the study regions, which explained over 75%, 67%, and 86% of the spatial variance in soil moisture in Nebraska, Utah, and the Southeast U.S., respectively. Despite the significant spatial variability in precipitation and potential evapotranspiration in all the study regions, the results showed that meteorological forcings had limited effects on regional SMSV in those regions with different climatic conditions, which differed from the traditional notion that SMSV is mainly controlled by meteorological forcings at the scale from 50 to 400 km. Instead, local factors related to soil (e.g., sand and clay fractions) were found to have significant correlations with EOF1, although the effects of other local factors (e.g., topography and vegetation) were generally negligible. This study provides strong field evidence that soil can exert much stronger impacts on regional SMSV than previously thought, which can override the effects of meteorological forcings. Future studies are still needed to elaborate on the relative roles of climate and soil in affecting regional SMSV.
      PubDate: 2017-04-29T10:02:32.572717-05:
      DOI: 10.1002/2017WR020642
       
  • Simulating seasonal variations of tile drainage discharge in an
           agricultural catchment
    • Authors: G. De Schepper; R. Therrien, J. C. Refsgaard, X. He, C. Kjaergaard, B. V. Iversen
      Abstract: Seasonal variations of tile drainage discharge were simulated in the 6 km2 Fensholt catchment, Denmark, with the coupled surface and subsurface HydroGeoSphere model. The catchment subsurface is represented in the model by 3 m of topsoil and clay, underlain by a heterogeneous distribution of sand and clay units. Two subsurface drainage networks were represented as nodal sinks. The spatial distribution of the heterogeneous units was generated stochastically and their hydraulic properties were calibrated to reproduce drainage discharge for one network and verified with drainage discharge for the other network. Simulated discharge was compared to that of another model for which the heterogeneous sand and clay units were replaced by a homogeneous unit, whose hydraulic conductivity was the mean value of the heterogeneous model. With the homogeneous model, drainage dynamics were correctly simulated but drainage discharge was less accurate compared to the heterogeneous model. Simulated discharge was also compared to that a larger scale model created with the MIKE SHE code, built with the same heterogeneous model. HydroGeoSphere and MIKE SHE generated drainage discharge that was significantly different, with better simulated groundwater dynamics data produced by HydroGeoSphere. Nodal sinks in HydroGeoSphere reproduced drain flow peaks more accurately. Calibration against drainage discharge data suggests that drain flow is controlled primarily by geological heterogeneities included in the model and, to a lesser extent, by the nature of the soil units located between the drains and ground surface.
      PubDate: 2017-04-27T18:31:01.861163-05:
      DOI: 10.1002/2016WR020209
       
  • The importance and challenge of hyporheic mixing
    • Authors: Erich T. Hester; M. Bayani Cardenas, Roy Haggerty, Sourabh V. Apte
      Abstract: The hyporheic zone is the interface beneath and adjacent to streams and rivers where surface water and groundwater interact. The hyporheic zone presents unique conditions for reaction of solutes from both surface water and groundwater, including reactions which depend upon mixing of source waters. Some models assume that hyporheic zones are well-mixed and conceptualize the hyporheic zone as a surface water-groundwater mixing zone. But what are the controls on and effects of hyporheic mixing? What specific mechanisms cause the relatively large (>∼1m) mixing zones suggested by subsurface solute measurements? In this commentary, we explore the various processes that might enhance mixing in the hyporheic zone relative to deeper groundwater, and pose the question whether the substantial mixing suggested by field studies may be due to the combination of fluctuating boundary conditions and multi-scale physical and chemical spatial heterogeneity. We encourage investigation of hyporheic mixing using numerical modeling and laboratory experiments to ultimately inform field investigations.
      PubDate: 2017-04-27T18:30:51.377076-05:
      DOI: 10.1002/2016WR020005
       
  • Evaluating the impacts of farmers' behaviors on a hypothetical
           agricultural water market based on double auction
    • Authors: Erhu Du; Ximing Cai, Nicholas Brozović, Barbara Minsker
      Abstract: Agricultural water markets are considered effective instruments to mitigate the impacts of water scarcity and to increase crop production. However, previous studies have limited understanding of how farmers' behaviors affect the performance of water markets. This study develops an agent-based model to explicitly incorporate farmers' behaviors, namely irrigation behavior (represented by farmers' sensitivity to soil water deficit λ) and bidding behavior (represented by farmers' rent seeking μ and learning rate β), in a hypothetical water market based on a double auction. The model is applied to the Guadalupe River Basin in Texas to simulate a hypothetical agricultural water market under various hydrological conditions. It is found that the joint impacts of the behavioral parameters on the water market are strong and complex. In particular, among the three behavioral parameters, λ affects the water market potential and its impacts on the performance of the water market are significant under most scenarios. The impacts of μ or β on the performance of the water market depend on the other two parameters. The water market could significantly increase crop production only when the following conditions are satisfied: (1) λ is small, and (2) μ is small and/or β is large. The first condition requires efficient irrigation scheduling, and the second requires well-developed water market institutions that provide incentives to bid true valuation of water permits.
      PubDate: 2017-04-27T18:28:30.723561-05:
      DOI: 10.1002/2016WR020287
       
  • Dynamic hyporheic and riparian flow path geometry through base flow
           recession in two headwater mountain stream corridors
    • Authors: Adam S. Ward; Noah M. Schmadel, Steven M. Wondzell, Michael N. Gooseff, Kamini Singha
      Abstract: The hydrologic connectivity between streams and their valley bottoms (stream corridor) is a critical determinant of their ecological function. Ecological functions are known to be spatially and temporally variable, but spatial dimensions of the problem are not easily quantified and thus they are usually overlooked. To estimate the spatial patterns of connectivity, and how connectivity varies with changes in discharge, we developed the Hyporheic Potential Model. We used the model to interpret a series of solute tracer injections in two headwater mountain streams with contrasting valley bottom morphologies to estimate connectivity in the stream corridor. The distributions of flowpath origination locations and the lengths of hyporheic flow paths appear to vary with baseflow recession, even in cases where transport timescales are apparently unchanged. The modeled distribution of origination locations further allowed us to define a spatial analogue to the temporal window of detection associated with solute tracer studies, and enables assessment of connectivity dynamics between streams and their corridors. Altogether, the reduced complexity Hyporheic Potential Model provides an easy way anticipate the spatial distribution and origination locations of hyporheic flow paths from a basic understanding of the valley bottom characteristics and solute transport timescales.
      PubDate: 2017-04-26T11:30:35.745422-05:
      DOI: 10.1002/2016WR019875
       
  • Rainfall variability in the Himalayan orogen and its relevance to erosion
           processes
    • Authors: Eric Deal; Anne-Catherine Favre
      Abstract: Rainfall is an important driver of erosion processes. The mean rainfall rate is often used to account for the erosive impact of a particular climate. However, for some erosion processes, erosion rate is a nonlinear function of rainfall, e.g. due to a threshold for erosion. When this is the case, it is important to take into account the full distribution of rainfall, instead of just the mean. In light of this, we have characterized the variability of daily rainfall over the Himalayan orogen using high spatial and temporal resolution rainfall data sets. We find significant variations in rainfall variability over the Himalayan orogen, with increasing rainfall variability to the west and north of the orogen. By taking into account variability of rainfall in addition to mean rainfall rate, we find a pattern of rainfall that, from a geomorphological perspective, is significantly different from mean rainfall rate alone. Using these findings we argue that short-term rainfall variability may help explain observed short and long term erosion rates in the Himalayan orogen.
      PubDate: 2017-04-26T11:21:42.662329-05:
      DOI: 10.1002/2016WR020030
       
  • Technical report: The design and evaluation of a basin-scale wireless
           sensor network for mountain hydrology
    • Authors: Ziran Zhang; Steven D. Glaser, Roger C. Bales, Martha Conklin, Robert Rice, Danny G. Marks
      Abstract: A network of sensors for spatially representative water-balance measurements was developed and deployed across the 2000 km2 snow-dominated portion of the upper American River basin, primarily to measure changes in snowpack and soil-water storage, air temperature and humidity. This wireless sensor network (WSN) consists of 14 sensor clusters, each with 10 measurement nodes that were strategically placed within a 1­km2 area, across different elevations, aspects, slopes and canopy covers. Compared to existing operational sensor installations, the WSN reduces hydrologic uncertainty in at least three ways. First, redundant measurements improved estimation of lapse rates for air and dew-point temperature. Second, distributed measurements captured local variability and constrained uncertainty in air and dew-point temperature, snow accumulation and derived hydrologic attributes important for modeling and prediction. Third, the distributed relative-humidity measurements offer a unique capability to monitor upper-basin patterns in dew-point temperature and characterize elevation gradient of water vapor-pressure deficit across steep, variable topography. Network statistics during the first year of operation demonstrated that the WSN was robust for cold, wet and windy conditions in the basin. The electronic technology used in the WSN reduced adverse effects, such as high current consumption, multipath signal fading and clock drift, seen in previous remote WSNs.
      PubDate: 2017-04-26T11:16:04.63207-05:0
      DOI: 10.1002/2016WR019619
       
  • Inferring reservoir operating patterns across the Mekong Basin using only
           space observations
    • Authors: Matthew Bonnema; Faisal Hossain
      Abstract: This study explores the operating pattern of artificial reservoirs by examining their impact on streamflow through two parameters, residence time and flow alteration, using a purely satellite based technique for the Mekong Basin. Overall residence times of individual reservoirs ranged from 0.09 years to 4.04 years, while streamflow was altered between 11% and 130% of its natural variability. The current set of reservoirs appears to have increased the residence time of the entire Mekong basin by about 1 month. However, if sub-basin variability is considered, the satellite-based method depicts a different picture. Residence time increases to 4 months when only regulated flows are considered. If low residence time reservoirs on major rivers are excluded and reservoirs on higher stream-order rivers considered, residence time increases to 1.3 years. Predictable strong seasonal patterns emerged in residence time, where reservoirs experience higher residence time in the dry season and lower residence time in the wet season and residence time varies inversely with precipitation. High variability in reservoir effects on streamflow between reservoirs could not be explained by any reservoir properties (e.g. size, use, location, etc.), highlighting the variability in the human decisions operating these reservoirs. The take-home message of this study is that satellite observations, in combination with physical models forced with satellite data can elucidate the spatio-temporal variability of reservoir behavior in ungauged basins of the developing world. We demonstrate in this study that the requirement for ground data to monitor current or historical behavior of dams is not necessary.
      PubDate: 2017-04-25T10:50:53.161606-05:
      DOI: 10.1002/2016WR019978
       
  • Concentration-discharge relationships in headwater streams of the Sierra
           Nevada, California
    • Authors: Carolyn T. Hunsaker; Dale W. Johnson
      Abstract: We examined streamwater concentration-discharge relationships for eight small, forest watersheds ranging in elevation from 1,485 to 2,465 m in the southern Sierra Nevada. These headwater streams revealed nearly chemostatic behavior by current definitions for K+, Ca2+, Mg2+, Na+, Cl- and SO42- in most cases but not for NH4+. NO3-, or ortho-P. The latter ions were somewhat enriched during high flows. All ions studied showed a dilution process at lower flows (< 50 l sec−1) with the concentration-discharge relationship being more chemostatic at higher flows. While previous studies in the Sierra Nevada have reported peak concentrations of NH4+, NO3-, and SO42- during snowmelt, the headwater systems of the Kings River Experimental Watersheds experience peak concentrations of these ions during the fall rains after the dry summer. These forested watersheds span the rain-snow transition zone, are 49 to 228 ha in size, and have soils derived from granite. A statistically significant relationship between soils and streamwater concentrations for ortho-P, Ca2+, and Na+ strongly suggests that soil chemistry has a major influence on streamwater chemistry. Factors controlling streamwater NH4+, NO3-, and SO42- concentrations are less clear, but one possible source of spikes in these ions during storm events is input from O-horizon runoff where high concentrations were measured. Overall, streamwater concentation-discharge relationships for these Sierran watersheds are similar to those found in other watershed systems (nearly chemostatic); however, the dominant processes controlling these relationships are probably localized because of different watershed characteristics like soil chemistry, vegetation cover, hydrologic flow paths, and weather patterns.
      PubDate: 2017-04-25T10:50:47.401121-05:
      DOI: 10.1002/2016WR019693
       
  • Similarities and differences between three coexisting spaceborne radars in
           global rainfall and snowfall estimation
    • Authors: Guoqiang Tang; Yixin Wen, Jinyu Gao, Di Long, Yingzhao Ma, Wei Wan, Yang Hong
      Abstract: Precipitation is one of the most important components in the water and energy cycles. Radars are considered the best available technology for observing the spatial distribution of precipitation either from the ground since the 1980s or from space since 1998. This study, for the first time ever, compares and evaluates the only three existing spaceborne precipitation radars, i.e., the Ku-band precipitation radar (PR), the W-band Cloud Profiling Radar (CPR), and the Ku/Ka-band Dual-frequency Precipitation Radar (DPR). The three radars are matched up globally and intercompared in the only period which they co-exist: 2014-2015. In addition, for the first time ever, TRMM PR and GPM DPR are evaluated against hourly rain gauge data in Mainland China. Results show that DPR and PR agree with each other and correlate very well with gauges in Mainland China. However, both show limited performance in the Tibetan Plateau (TP) known as the Earth's third pole. DPR improves light precipitation detectability, when compared with PR, whereas CPR performs best for light precipitation and snowfall. DPR snowfall has the advantage of higher sampling rates than CPR; however, its accuracy needs to be improved further. The future development of spaceborne radars is also discussed in two complementary categories: (1) multi-frequency radar instruments on a single platform and (2) constellations of many small cube radar satellites, for improving global precipitation estimation. This comprehensive intercomparison of PR, CPR, and DPR sheds light on spaceborne radar precipitation retrieval and future radar design.
      PubDate: 2017-04-21T11:32:41.24204-05:0
      DOI: 10.1002/2016WR019961
       
  • Modeling blowing snow accumulation downwind of an obstruction: The Ohara
           Eulerian particle distribution equation
    • Authors: N. J. Kinar
      Abstract: An equation [Ohara, 2017] was proposed to model the height of blowing snow accumulation downwind of an obstacle such as vegetation, a snow fence, a building, or a topographic feature. The equation does not require aerodynamic flow condition parameters such as wind speed, allowing for the spatial distribution of snow to be determined at locations where meteorological data is not available. However, snow particle diffusion, drift and erosion coefficients must be estimated for application of the equation. These coefficients can be used to provide insight into the relative magnitude of blowing snow processes at a field location. Further research is required to determine efficient methods for coefficient estimation. The equation could be used with other models of wind-transported snow to predict snow accumulation downwind of an obstacle without the need for wind speed adjustments or correction equations. Applications for this equation include the design of snow fences, and the use of this equation with other hydrological models to predict snow distribution, climate change, drought, flooding, and avalanches.
      PubDate: 2017-04-21T11:32:25.590737-05:
      DOI: 10.1002/2017WR020731
       
  • Observational breakthroughs lead the way to improved hydrological
           predictions
    • Authors: Dennis P. Lettenmaier
      Abstract: New data sources are revolutionizing the hydrological sciences. The capabilities of hydrological models have advanced greatly over the last several decades, but until recently model capabilities have outstripped the spatial resolution and accuracy of model forcings (atmospheric variables at the land surface) and the hydrologic state variables (e.g., soil moisture; snow water equivalent) that the models predict. This has begun to change, as shown in two examples here: soil moisture and drought evolution over Africa as predicted by a hydrology model forced with satellite-derived precipitation, and observations of snow water equivalent at very high resolution over a river basin in California's Sierra Nevada.
      PubDate: 2017-04-20T13:01:14.892909-05:
      DOI: 10.1002/2017WR020896
       
  • Solving water quality problems in agricultural landscapes: New approaches
           for these nonlinear, multiprocess, multiscale systems
    • Authors: Patrick Belmont; Efi Foufoula-Georgiou
      Abstract: Changes in climate and agricultural practices are putting pressure on agroenvironmental systems all over the world. Predicting the effects of future management or conservation actions has proven exceptionally challenging in these complex landscapes. We present a perspective, gained from a decade of research and stakeholder involvement in the Minnesota River Basin, where research findings have influenced solutions and policy in directions not obvious at the outset. Our approach has focused on identifying places, times, and processes of accelerated change and developing reduced complexity predictive frameworks that can inform mitigation actions.
      PubDate: 2017-04-20T13:01:10.41205-05:0
      DOI: 10.1002/2017WR020839
       
  • The essential value of long-term experimental data for hydrology and water
           management
    • Authors: Doerthe Tetzlaff; Sean K. Carey, James P. McNamara, Hjalmar Laudon, Chris Soulsby
      Abstract: Observations and data from long-term experimental watersheds are the foundation of hydrology as a geoscience. They allow us to benchmark process understanding, observe trends and natural cycles, and are prerequisites for testing predictive models. Long-term experimental watersheds also are places where new measurement technologies are developed. These studies offer a crucial evidence base for understanding and managing the provision of clean water supplies, predicting and mitigating the effects of floods, and protecting ecosystem services provided by rivers and wetlands. They also show how to manage land and water in an integrated, sustainable way that reduces environmental and economic costs.
      PubDate: 2017-04-20T09:04:41.384354-05:
      DOI: 10.1002/2017WR020838
       
  • Science, politics, and rationality in a partisan era
    • Authors: James W. Kirchner
      Abstract: Science plays an essential role in public policy by outlining the factual foundations of policy debates. As a result, science often becomes a political football, with partisans dismissing or misrepresenting scientific findings that conflict with their political views. Here I argue that scientists can most effectively speak out, not as activists supporting particular political causes, but instead as advocates for a fundamentally rational public discourse, one that starts from the facts – not from whatever one might choose to believe – and then explores how society should respond to the challenges that they pose.
      PubDate: 2017-04-20T09:00:07.843589-05:
      DOI: 10.1002/2017WR020882
       
  • The frontier beneath our feet
    • Authors: Gordon E. Grant; William E. Dietrich
      Abstract: Following the simple question as to where water goes when it rains leads to one of the most exciting frontiers in earth science: the critical zone – Earth's dynamic skin. The critical zone extends from the top of the vegetation canopy through the soil and down to fresh bedrock and the bottom of the groundwater. Only recently recognized as a distinct zone, it is challenging to study because it is hard to observe directly, and varies widely across biogeoclimatic regions. Yet new ideas, instruments, and observatories are revealing surprising and sometimes paradoxical insights, underscoring the value of field campaigns and long-term observatories. These insights bear directly on some of the most pressing societal problems today: maintaining healthy forests, sustaining streamflow during droughts, and restoring productive terrestrial and aquatic ecosystems. The critical zone is critical because it supports all terrestrial life; it is the nexus where water and carbon is cycled, vegetation (hence food) grows, soil develops, landscapes evolve, and we live. No other frontier is so close to home.
      PubDate: 2017-04-20T09:00:07.463751-05:
      DOI: 10.1002/2017WR020835
       
  • Water and life from snow: A trillion dollar science question
    • Authors: Matthew Sturm; Michael A. Goldstein, Charles Parr
      Abstract: Snow provides essential resources/services in the form of water for human use, and climate regulation in the form of enhanced cooling of the Earth. In addition, it supports a thriving winter outdoor recreation industry. To date, the financial evaluation of the importance of snow is incomplete and hence the need for accelerated snow research is not as clear as it could be. With snow cover changing worldwide in several worrisome ways, there is pressing need to determine global, regional, and local rates of snow cover change, and to link these to financial analyses that allow for rational decision-making, as risks related to those decisions involve trillions of dollars.
      PubDate: 2017-04-20T09:00:06.503109-05:
      DOI: 10.1002/2017WR020840
       
  • Geological storage of captured carbon dioxide as a large-scale carbon
           mitigation option
    • Authors: Michael A. Celia
      Abstract: Carbon capture and storage, or CCS, involves capture of CO2 emissions from power plants and other large stationary sources and subsequent injection of the captured CO2 into deep geological formations. This is the only technology currently available that allows continued use of fossil fuels while simultaneously reducing emissions of CO2 to the atmosphere. Although the subsurface injection and subsequent migration of large amounts of CO2 involve a number of challenges, many decades of research in the earth sciences, focused on fluid movement in porous rocks, provides a strong foundation on which to analyze the system. These analyses indicate that environmental risks associated with large CO2 injections appear to be manageable.
      PubDate: 2017-04-20T09:00:05.8641-05:00
      DOI: 10.1002/2017WR020841
       
  • Science, society, and the coastal groundwater squeeze
    • Authors: Holly A. Michael; Vincent E.A. Post, Alicia M. Wilson, Adrian D. Werner
      Abstract: Coastal zones encompass the complex interface between land and sea. Understanding how water and solutes move within and across this interface is essential for managing resources for society, such as clean water, and for ecosystem conservation. The increasingly dense human occupation of coastal zones disrupts natural groundwater flow patterns and degrades freshwater resources by both over-use and pollution. This pressure results in a ‘coastal groundwater squeeze', where the thin veneers of potable freshwater are threatened by contaminant sources at the land surface and saline groundwater at depth. Scientific advances in the field of coastal hydrogeology have enabled responsible management of water resources and protection of important ecosystems. To address the problems of the future, we must continue to make scientific advances, and groundwater hydrology needs to be firmly embedded in integrated coastal zone management. This will require interdisciplinary scientific collaboration, open communication between scientists and the public, and strong partnerships with policymakers.
      PubDate: 2017-04-20T09:00:05.348229-05:
      DOI: 10.1002/2017WR020851
       
  • The food-energy-water nexus: Transforming science for society
    • Authors: Bridget R. Scanlon; Ben L. Ruddell, Patrick M. Reed, Ruth I. Hook, Chunmiao Zheng, Vince C. Tidwell, Stefan Siebert
      Abstract: Emerging interdisciplinary science efforts are providing new understanding of the interdependence of food, energy, and water (FEW) systems. These science advances, in turn, provide critical information for coordinated management to improve the affordability, reliability, and environmental sustainability of FEW systems. Here we describe the current state of the FEW nexus and approaches to managing resource conflicts through reducing demand and increasing supplies, storage, and transport. Despite significant advances within the past decade, there are still many challenges for the scientific community. Key challenges are the need for interdisciplinary science related to the FEW nexus; ground-based monitoring and modeling at local-to-regional scales; incorporating human and institutional behavior in models; partnerships among universities, industry, and government to develop policy relevant data; and systems modeling to evaluate tradeoffs associated with FEW decisions.
      PubDate: 2017-04-20T09:00:04.367199-05:
      DOI: 10.1002/2017WR020889
       
  • Lattice Boltzmann simulation of immiscible two-phase flow with capillary
           valve effect in porous media
    • Authors: Zhiyuan Xu; Haihu Liu, Albert J. Valocchi
      Abstract: A new algorithm for imposing the contact angle on solid surfaces is proposed in the Lattice Boltzmann color-gradient model. The capability and accuracy of this algorithm are validated by simulation of contact angles for a droplet resting on a flat surface and on a cylindrical surface. The color-gradient model with the proposed contact angle algorithm is then used to study the capillary valve effect in porous media. As a preliminary study, the capillary valve effect is explained by simulating immiscible two-phase displacement within a single-pore geometry. It is shown that the capillary valve effect is accurately captured by the present simulations. Further simulations of drainage and imbibition are also conducted to understand the capillary valve effect in an experiment-matched pore network micromodel. The simulated results are found to agree quantitatively with the experimental results reported in literature, except for a few differences which result from the exclusion of contact angle hysteresis in the proposed algorithm.
      PubDate: 2017-04-19T14:48:47.753003-05:
      DOI: 10.1002/2017WR020373
       
  • A modeling approach to identify the effective forcing exerted by wind on a
           pre-alpine lake surrounded by a complex topography
    • Authors: G. Valerio; A. Cantelli, P. Monti, G. Leuzzi
      Abstract: The representation of spatial wind distribution is recognized as a serious difficulty when modeling the hydrodynamics of lakes surrounded by a complex topography. To address this issue, we propose to force a 3D lake model with the wind field simulated by a high-resolution atmospheric model, considering as a case study a 61 km2 pre-alpine lake surrounded by mountain ranges that reach 1800 m above the lake's surface, where a comprehensive data set was available in the stratified season. The improved distributed description of the wind stress over the lake surface led to a significant enhancement in the representation of the main basin-scale internal wave motions, and hence provided a reference solution to test the use of simplified approaches. Moreover, the analysis of the power exerted by the computed wind field enabled us to identify measuring stations that provide suitable wind data to be applied uniformly on the lake surface in long-term simulations. Accordingly, the proposed methodology can contribute to reducing the uncertainties associated with the definition of wind forcing for modeling purposes and can provide a rational criterion for installing representative measurement locations in pre-alpine lakes.
      PubDate: 2017-04-19T13:53:24.408967-05:
      DOI: 10.1002/2016WR020335
       
  • Machine learning algorithms for modeling groundwater level changes in
           agricultural regions of the United States
    • Authors: S. Sahoo; T. A. Russo, J. Elliott, I. Foster
      Abstract: Climate, groundwater extraction, and surface water flows have complex nonlinear relationships with groundwater level in agricultural regions. To better understand the relative importance of each driver, and predict groundwater level change, we develop a new ensemble modeling framework based on spectral analysis, machine learning, and uncertainty analysis, as an alternative to complex and computationally expensive physical models. We apply and evaluate this new approach in the context of two aquifer systems supporting agricultural production in the United States: the High Plains aquifer (HPA) and the Mississippi River Valley alluvial aquifer (MRVA). We select input datasets by using a combination of mutual information, genetic algorithms, and lag analysis, and then use the selected datasets in a Multilayer Perceptron network architecture to simulate seasonal groundwater level change. As expected, model results suggest that irrigation demand has the highest influence on groundwater level change for a majority of the wells. The subset of groundwater observations not used in model training or cross-validation correlates strongly (R > 0.8) with model results for 88% and 83% of the wells in the HPA and MRVA, respectively. In both aquifer systems, the error in the modeled cumulative groundwater level change during testing (2003 to 2012) was less than 2 m over a majority of the area. We conclude that our modeling framework can serve as an alternative approach to simulating groundwater level change and water availability, especially in regions where subsurface properties are unknown.
      PubDate: 2017-04-19T13:53:16.126975-05:
      DOI: 10.1002/2016WR019933
       
  • Changes in floodplain inundation under nonstationary hydrology for an
           adjustable, alluvial river channel
    • Authors: B.C. Call; P. Belmont, J.C. Schmidt, P. R. Wilcock
      Abstract: Predicting the frequency and aerial extent of flooding in river valleys is essential for infrastructure design, environmental management, and risk assessment. Conventional flood prediction relies on assumptions of stationary flood distributions and static channel geometries. However, non-stationary flow regimes are increasingly observed and changes in flow and/or sediment supply are known to alter the geometry and flood conveyance of alluvial channels. Systematic changes in flows and/or channel geometry may amplify or attenuate the frequency and/or extent of flood inundation in unexpected ways. We present a stochastic, reduced complexity model to investigate such dynamics. The model routes a series of annual peak-discharges through a simplified reach-averaged channel-floodplain cross-section. Channel width, depth, and slope are permitted to adjust annually by a user-specified fraction towards equilibrium geometries predicted based on each year's peak-discharge and sediment supply. Modeled channel adjustments are compared with empirical observations for two rivers in Minnesota, USA that have experienced multiple large floods over the past six-years. The model is then run using six-hypothetical scenarios simulating non-stationary flow regimes with temporal adjustments in the mean and/or variance of the governing peak-flow distributions. Each scenario is run repeatedly while varying parameters that control the amount of fractional adjustment that channel geometries can make annually. Results indicate that the intra-annual mean horizontal width of floodplain inundation primarily depends on the governing peak-flow distribution's coefficient of variation, but the intra-annual frequency of floodplain inundation (i.e. the fraction of modeled years with inundation) primarily depends on the amount of channel adjustment permitted annually.
      PubDate: 2017-04-19T13:38:10.547136-05:
      DOI: 10.1002/2016WR020277
       
  • Big ship data: Using vessel measurements to improve estimates of
           temperature and wind speed on the Great Lakes
    • Authors: Kevin Fries; Branko Kerkez
      Abstract: The sheer size of many water systems challenges the ability of in-situ sensor networks to resolve spatiotemporal variability of hydrologic processes. New sources of vastly distributed and mobile measurements are, however, emerging to potentially fill these observational gaps. This paper poses the question: How can non-traditional measurements, such as those made by volunteer ship captains, be used to improve hydrometeorological estimates across large surface water systems? We answer this question through the analysis of one of the largest such data sets: an unprecedented collection of one million unique measurements made by ships on the North American Great Lakes from 2006-2014. We introduce a flexible probabilistic framework, which can be used to integrate ship measurements, or other sets of irregular point measurements, into contiguous datasets. The performance of this framework is validated through the development of a new ship-based spatial data product of water temperature, air temperature and wind speed across the Great Lakes. An analysis of the final data product suggests that the availability of measurements across the Great Lakes will continue to play a large role in the confidence with which these large surface water systems can be studied and modeled. We discuss how this general and flexible approach can be applied to similar data sets, and how it will be of use to those seeking to merge large collections of measurements with other sources of data, such as physical models or remotely sensed products.
      PubDate: 2017-04-13T11:34:23.714221-05:
      DOI: 10.1002/2016WR020084
       
  • Implementation of a physiographic complexity-based multiresolution snow
           modeling scheme
    • Authors: Elisabeth Baldo; Steven A. Margulis
      Abstract: Using a uniform model resolution over a domain is not necessarily the optimal approach for simulating hydrologic processes when considering both model error and computational cost. Fine -resolution simulations at 100 m or less can provide fine-scale process representation, but can be costly to apply over large domains. On the other hand, coarser spatial resolutions are more computationally inexpensive, but at the expense of fine-scale model accuracy. Defining a multi-resolution (MR) grid spanning from fine-resolutions over complex mountainous areas to coarser resolutions over less complex regions can conceivably reduce computational costs, while preserving the accuracy of fine-resolution simulations on a uniform grid. A MR scheme was developed using a physiographic complexity metric (CM) that combines surface heterogeneity in forested fraction, elevation, slope and aspect. A data reduction term was defined as a metric (relative to a uniform fine-resolution grid) related to the available computational resources for a simulation. The focus of the effort was on the melt season where physiographic complexity is known to have a significant signature. MR simulations were run for different data reduction factors to generate melt rate estimates for three representative water years over a test headwater catchment in the Colorado River Basin. The MR approach with data reductions up to 47% led to negligible cumulative snowmelt differences compared to the fine-resolution baseline case, while tests with data reductions up to 60% showed differences lower than 2%. Large snow-dominated domains could therefore benefit from a MR approach to be more efficiently simulated while mitigating error.
      PubDate: 2017-04-13T11:33:43.487268-05:
      DOI: 10.1002/2016WR020021
       
  • Physical effects of thermal pollution in lakes
    • Authors: Love Råman Vinnå; Alfred Wüest, Damien Bouffard
      Abstract: Anthropogenic heat emissions into inland waters influence water temperature and affect stratification, heat and nutrient fluxes, deep-water renewal and biota. Given the increased thermal stress on these systems by growing cooling demands of riparian/costal infrastructures in combination with climate warming, the question arises on how to best monitor and manage these systems. In this study, we investigate local and system-wide physical effects on the medium-sized perialpine Lake Biel (Switzerland), influenced by point-source cooling-water emission from an upstream nuclear power plant (heat emission ∼700 MW, ∼18 W m−2 lake-wide). We use one-dimensional (SIMSTRAT) and three-dimensional (Delft3D-Flow) hydrodynamic numerical simulations and provide model resolution guidelines for future studies of thermal pollution. The effects on Lake Biel by the emitted excess heat are summarized as: (i) clear seasonal trend in temperature increase, locally up to 3.4°C and system-wide volume-mean ∼0.3°C, which corresponds to one decade of regional surface water climate warming, (ii) the majority of supplied thermal pollution (∼60%) leaves this short residence time (∼58 days) system via the main outlet, whereas the remaining heat exits to the atmosphere, (iii) increased length of stratified period due to the stabilizing effects of additional heat, (iv) system-wide effects such as warmer temperature, prolonged stratified period and river-caused epilimnion flushing are resolved by both models whereas local raised temperature and short-circuiting was only identifiable with the three-dimensional model approach. This model-based method provides an ideal tool to assess man-made impacts on lakes and their downstream outflows.
      PubDate: 2017-04-13T11:33:39.247943-05:
      DOI: 10.1002/2016WR019686
       
  • Time-dependent velocity-field controls on anomalous chemical transport in
           porous media
    • Authors: Alon Nissan; Ishai Dror, Brian Berkowitz
      Abstract: Temporal variations in the subsurface velocity field are often (if not always) present in the real world to at least some degree. However, an accounting of their effects on chemical transport has been largely neglected. Here, we demonstrate experimentally effects of a time-varying velocity field on conservative chemical tracer transport in porous media, as compared to constant velocity conditions. We find that velocity-field fluctuations increase chemical tracer spreading and residence time, which intensify the anomalous nature of the transport. This behavior is modeled by a continuous time random walk particle tracking method formulated to account for time-dependent velocity fields. The model matches the experimental results with a parsimonious and consistent set of parameters. The model is then applied to study the effects of different magnitudes in velocity-field fluctuations, as well as different degrees of porous media heterogeneity, on 1-D and 2-D spatiotemporal propagation of an injected, point source, chemical plume. Increased intensity of velocity-field fluctuations, and increased porous medium heterogeneity, each serve to increase the extent of chemical spreading and anomalous behavior.
      PubDate: 2017-04-13T11:33:34.188247-05:
      DOI: 10.1002/2016WR020143
       
  • An efficient and stable hydrodynamic model with novel source term
           discretisation schemes for overland flow simulations
    • Authors: Xilin Xia; Qiuhua Liang, Xiaodong Ming, Jingming Hou
      Abstract: Numerical models solving the full 2D shallow water equations (SWEs) have been increasingly used to simulate overland flows and better understand the transient flow dynamics of flash floods in a catchment. However, there still exists key challenges that have not yet been resolved for the development of fully dynamic overland flow models, related to 1) the difficulty of maintaining numerical stability and accuracy in the limit of disappearing water depth; and 2) inaccurate estimation of velocities and discharges on slopes as a result of strong nonlinearity of friction terms. This paper aims to tackle these key research challenges and present a new numerical scheme for accurately and efficiently modelling large-scale transient overland flows over complex terrains. The proposed scheme features a novel surface reconstruction method (SRM) to correctly compute slope source terms and maintain numerical stability at the small water depth condition, and a new implicit discretisation method to handle highly nonlinear friction terms. The resulting shallow water overland flow model is first validated against analytical and experimental test cases and then applied to simulate a hypothetic rainfall event on the 42 km2 Haltwhistle Burn, UK.
      PubDate: 2017-04-11T08:16:03.468387-05:
      DOI: 10.1002/2016WR020055
       
  • Mineralogical and transport controls on the evolution of porous media
           texture using direct numerical simulation
    • Authors: Sergi Molins; David Trebotich, Gregory H. Miller, Carl I. Steefel
      Abstract: The evolution of porous media due to mineral dissolution and precipitation can change the bulk properties of subsurface materials. The pore-scale structure of the media, including its physical and mineralogical heterogeneity, exerts controls on porous media evolution via transport limitations to reactive surfaces and mineral accessibility. Here we explore how these controls affect the evolution of the texture in porous media at the pore scale. For this purpose, a pore-scale flow and reactive transport model is developed that explicitly tracks mineral surfaces as they evolve using a direct numerical simulation approach. Simulations of dissolution in single-mineral domains provide insights into the transport controls at the pore scale, while the simulation of a fracture surface composed of bands of faster-dissolving calcite and slower-dissolving dolomite provides insights into the mineralogical controls on evolution. Transport-limited conditions at the grain-pack scale may result in unstable evolution, a situation in which dissolution is focused in a fast-flowing, fast-dissolving path. Due to increasing velocities, the evolution in these regions is like that observed under conditions closer to strict surface control at the pore scale. That is, grains evolve to have oblong shapes with their long dimensions aligning with the local flow directions. Another example of an evolving reactive transport regime that affects local rates is seen in the evolution of the fracture surface. As calcite dissolves, the diffusive length between the fracture flow path and the receding calcite surfaces increases. Thus, the calcite dissolution reaction becomes increasingly limited by diffusion.
      PubDate: 2017-04-11T08:15:46.767433-05:
      DOI: 10.1002/2016WR020323
       
  • Continuous monitoring of snowpack dynamics in alpine terrain by
           above-ground neutron sensing
    • Authors: Paul Schattan; Gabriele Baroni, Sascha E. Oswald, Johannes Schöber, Christine Fey, Christoph Kormann, Matthias Huttenlau, Stefan Achleitner
      Abstract: The characteristics of an above-ground cosmic-ray neutron sensor (CRNS) are evaluated for monitoring a mountain snowpack in the Austrian Alps from 03/2014 to 06/2016. Neutron counts were compared to continuous point-scale snow depth (SD) and snow-water-equivalent (SWE) measurements from an automatic weather station with a maximum SWE of 600 mm (04/2014). Several spatially distributed Terrestrial Laser Scanning (TLS) based SD and SWE maps were additionally used. A strong non-linear correlation is found for both SD and SWE. The representative footprint of the CRNS is in the range of 230 to 270 m. In contrast to previous studies suggesting signal saturation at around 100 mm of SWE, no complete signal saturation was observed. These results imply that CRNS could be transferred into an unprecedented method for continuous detection of spatially-averaged SD and SWE for alpine snowpacks, though with sensitivity decreasing with increasing SWE. While initially different functions were found for accumulation and melting season conditions, this could be resolved by accounting for a limited measurement depth. This depth limit is in the range of 200 mm of SWE for dense snowpacks with high liquid water contents and associated snow density values around 450 kg m−3 and above. In contrast to prior studies with shallow snowpacks, inter-annual transferability of the results is very high regardless of pre-snowfall soil moisture conditions. This underlines the unexpectedly high potential of CRNS to close the gap between point-scale measurements, hydrological models and remote sensing of the cryosphere in alpine terrain.
      PubDate: 2017-04-11T08:15:43.037977-05:
      DOI: 10.1002/2016WR020234
       
  • Characterizing landscape-scale erosion using 10Be in detrital fluvial
           sediment: Slope-based sampling strategy detects the effect of widespread
           dams
    • Authors: Lucas J. Reusser; Paul R. Bierman, Donna M. Rizzo, Eric W. Portenga, Dylan H. Rood
      Abstract: Concentrations of in situ 10Be measured in detrital fluvial sediment are frequently used to estimate long-term erosion rates of drainage basins. In many regions, basin-averaged erosion rates are positively correlated with basin average slope. The slope dependence of erosion allows model-based erosion rate estimation for unsampled basins and basins where human disturbance may have biased cosmogenic nuclide concentrations in sediment.Using samples collected from southeastern North America, we demonstrate an approach that explicitly considers the relationship between average basin slope and erosion rate. Because dams and reservoirs are ubiquitous on larger channels in the field area, we selected 36 undammed headwater sub-basins (average area 10.6 km2) from which we collected river sand samples and measured 10Be concentrations. We used these data to train a predictive model that relates average basin slope and 10Be-inferred erosion rate.Applying our model to 28 basins in the same region previously studied with 10Be, we find it successfully predicts erosion rates for basins of different sizes if they are undammed or if samples were collected >25 km downstream of dams. For samples collected closer to dams, measured erosion rates exceed modeled erosion rates for two-thirds of the samples. In three of four cases where paired samples were collected upstream of reservoirs and downstream of the impounding dam, 10Be concentrations were lower downstream. This finding has implications for detrital cosmogenic studies, whether or not samples were collected directly downstream of dams, because dams obstruct most major rivers around the world, effectively trapping sediment that originated upstream.
      PubDate: 2017-04-11T08:15:40.842875-05:
      DOI: 10.1002/2016WR019774
       
  • Ambient groundwater flow diminishes nitrate processing in the hyporheic
           zone of streams
    • Authors: Morvarid Azizian; Fulvio Boano, Perran L.M. Cook, Russell L. Detwiler, Megan A. Rippy, Stanley B. Grant
      Abstract: Modeling and experimental studies demonstrate that ambient groundwater flow reduces the flux of water through the hyporheic zone, but the implications of this observation for stream N-cycling is not yet clear. Here we utilize a simple process-based model (the Pumping and Streamline Segregation or PASS model) to evaluate N-cycling over two scales of hyporheic exchange (fluvial ripples and riffle-pool sequences), ten ambient groundwater and stream flow scenarios (five gaining and losing conditions and two stream discharges), and three biogeochemical settings (identified based on a principal component analysis of previously published measurements in streams throughout the U.S.). Model-data comparisons indicate that our model provides realistic estimates for direct denitrification of stream nitrate, but over-predicts nitrification and coupled nitrification-denitrification. Riffle-pool sequences are responsible for most of the N-processing, despite the fact that fluvial ripples generate 3 to 11 times more hyporheic exchange flux. Across all scenarios, hyporheic exchange flux and the Damköhler Number emerge as primary controls on stream N-cycling; the former regulates trafficking of nutrients and oxygen across the sediment-water interface, while the latter quantifies the relative rates of organic carbon mineralization and advective transport in streambed sediments. Vertical groundwater flux modulates both of these master variables in ways that tend to diminish stream N-cycling. Thus, anthropogenic perturbations of ambient groundwater flows (e.g., by urbanization, agricultural activities, groundwater mining, and/or climate change) may compromise some of the key ecosystem services provided by streams.
      PubDate: 2017-04-11T08:15:34.118278-05:
      DOI: 10.1002/2016WR020048
       
  • A Kolmogorov-Brutsaert structure function model for evaporation into a
           turbulent atmosphere
    • Authors: Gabriel Katul; Heping Liu
      Abstract: In 1965, Brutsaert proposed a model that predicted mean evaporation rate E¯ from rough surfaces to scale with the 3/4 power-law of the friction velocity (u*) and the square-root of molecular diffusivity (Dm) for water vapor. In arriving at these results, a number of assumptions were made regarding the surface renewal rate describing the contact durations between eddies and the evaporating surface, the diffusional mass process from the surface into eddies, and the cascade of turbulent kinetic energy sustaining the eddy renewal process itself. The working hypothesis explored here is that E¯∼Dmu*3/4 is a direct outcome of the Kolmogorov scaling for inertial subrange eddies modified to include viscous-cutoff thereby by-passing the need for a surface renewal assumption. It is demonstrated that Brutsaert's model for E¯ may be more general than its original derivation implied.
      PubDate: 2017-04-11T08:15:23.524671-05:
      DOI: 10.1002/2016WR020006
       
  • Noble gas signatures in the Island of Maui, Hawaii: Characterizing
           groundwater sources in fractured systems
    • Authors: Yi Niu; M. Clara Castro, Chris M. Hall, Stephen B. Gingerich, Martha A. Scholl, Rohit B. Warrier
      Abstract: Uneven distribution of rainfall and freshwater scarcity in populated areas in the Island of Maui, Hawaii, renders water resources management a challenge in this complex and ill-defined hydrological system. A previous study in the Galapagos Islands suggests that noble gas temperatures (NGTs) record seasonality in this fractured, rapid infiltration groundwater system rather than the commonly observed mean annual air temperature (MAAT) in sedimentary systems where infiltration is slower thus, providing information on recharge sources and potential flow paths. Here, we report noble gas results from the basal aquifer, springs, and rainwater in Maui to explore the potential for noble gases in characterizing these complex fractured hydrologic systems. Most samples display a mass-dependent depletion pattern with respect to surface conditions consistent with previous observations both in the Galapagos Islands and Michigan rainwater. Basal aquifer and rainwater noble gas patterns are similar and suggest direct, fast recharge from precipitation to the basal aquifer. In contrast, multiple springs, representative of perched aquifers, display highly variable noble gas concentrations suggesting recharge from a variety of sources. The distinct noble gas patterns for the basal aquifer and springs suggest that basal and perched aquifers are separate entities. Maui rainwater displays high apparent NGTs, incompatible with surface conditions, pointing either to an origin at high altitudes with the presence of ice or an ice-like source of undetermined origin. Overall, noble gas signatures in Maui reflect the source of recharge rather than the expected altitude/temperature relationship commonly observed in sedimentary systems.
      PubDate: 2017-04-10T09:42:05.773577-05:
      DOI: 10.1002/2016WR020172
       
  • Little impact of Three Gorges Dam on recent decadal lake decline across
           China's Yangtze Plain
    • Authors: Jida Wang; Yongwei Sheng, Yoshihide Wada
      Abstract: The ubiquitous lakes across China's Yangtze Plain (YP) are indispensable freshwater resources sustaining ecosystems and socioeconomics for nearly half a billion people. Our recent survey revealed a widespread net decline in the total YP lake inundation area during 2000–2011 (a cumulative decrease of ∼10%), yet its mechanism remains contentious. Here, we uncover the impacts of climate variability and anthropogenic activities including i) Yangtze flow and sediment alterations by the Three Gorges Dam (TGD) and ii) human water consumption in agricultural, industrial, and domestic sectors throughout the downstream Yangtze Basin. Results suggest that climate variability is the dominant driver of this decadal lake decline, whereas studied human activities, despite varying seasonal impacts that peak in fall, contribute marginal fraction (∼10–20% or less) to the interannual lake area decrease. Given that the TGD impacts on the total YP lake area and its seasonal variation are both under ∼5%, we also dismiss the speculation that the TGD might be responsible for evident downstream climate change by altering lake surface extent and thus open water evaporation. Nevertheless, anthropogenic impacts exhibited a strengthening trend during the past decade. Although the TGD has reached its full-capacity water regulation, the negative impacts of human water consumption and TGD-related net channel erosion are already comparable to that of TGD's flow regulation, and may continue to grow as crucial anthropogenic factors to future YP lake conservation.
      PubDate: 2017-04-06T15:06:18.231566-05:
      DOI: 10.1002/2016WR019817
       
  • Early formation of preferential flow in a homogeneous snowpack observed by
           micro-CT
    • Authors: Francesco Avanzi; Giacomo Petrucci, Margret Matzl, Martin Schneebeli, Carlo De Michele
      Abstract: We performed X-ray microtomographic observations of wet-snow metamorphism during controlled continuous melting and melt-freeze events in the laboratory. Three blocks of snow were sieved into boxes and subjected to cyclic, superficial heating or heating-cooling to reproduce vertical water infiltration patterns in snow similarly to natural conditions. Periodically, samples were taken at different heights and scanned. Results suggest that wet-snow metamorphism dynamics are highly heterogeneous even in an initially homogeneous snowpack. Consistent with previous work, we observed an increase with time in the thickness of the ice structure, which is a measure of grain size. However, this was coupled with large temporal scatter between consecutive measurements of the specific surface area and of the statistical moments of grain thickness distributions. Because of marked differences in the right tail, grain thickness distributions did not show shape invariance with time, contrary to previous analyses. In our experiments, wet-snow metamorphism showed two strikingly different patterns: homogeneous coarsening superimposed by faster heterogeneous coarsening in areas that were affected by preferential percolation of water. Liquid water movement in snow and fast structural evolution may be thus intrinsically coupled by early formation of preferential flow at local scale. These observations suggest that further experiments are highly needed to fully understand wet-snow metamorphism and infiltration patterns in a natural snowpack.
      PubDate: 2017-04-06T15:06:05.444864-05:
      DOI: 10.1002/2016WR019502
       
  • Development of an experimental approach to study coupled
           soil-plant-atmosphere processes using plant analogs
    • Authors: Andrew C. Trautz; Tissa H. Illangasekare, Ignacio Rodriguez-Iturbe, Katharina Heck, Rainer Helmig
      Abstract: The atmosphere, soils, and vegetation near the land-atmosphere interface are in a state of continuous dynamic interaction via a myriad of complex interrelated feedback processes which collectively, remain poorly understood. Studying the fundamental nature and dynamics of such processes in atmospheric, ecological, and/or hydrological contexts in the field setting presents many challenges; current experimental approaches are an important factor given a general lack of control and high measurement uncertainty. In an effort to address these issues and reduce overall complexity, new experimental design considerations (2-dimensional intermediate-scale coupled wind tunnel-synthetic aquifer testing using synthetic plants) for studying soil-plant-atmosphere continuum soil moisture dynamics are introduced and tested in this study. Validation of these experimental considerations, particularly the adoption of synthetic plants, is required prior to their application in future research. A comparison of three experiments with bare soil surfaces or transplanted with a Stargazer lily/limestone block, were used to evaluate the feasibility of the proposed approaches. Results demonstrate that coupled wind tunnel-porous media experimentation, used to simulate field conditions, reduces complexity and enhances control while allowing fine spatial-temporal resolution measurements to be made using state-of-the-art technologies. Synthetic plants further help reduce system complexity (e.g. airflow) while preserving the basic hydrodynamic functions of plants (e.g. water uptake and transpiration). The trends and distributions of key measured atmospheric and subsurface spatial and temporal variables (e.g. soil moisture, relative humidity, temperature, air velocity) were comparable, showing that synthetic plants can be used as simple, idealized, non-biological analogs for living vegetation in fundamental hydrodynamic studies.
      PubDate: 2017-04-06T15:05:55.832468-05:
      DOI: 10.1002/2016WR019884
       
  • A shallow water table fluctuation model in response to precipitation with
           consideration of unsaturated gravitational flow
    • Authors: Jina Jeong; Eungyu Park
      Abstract: A precise estimation of groundwater fluctuation is studied by considering delayed recharge flux (DRF) and unsaturated zone drainage (UZD). Both DRF and UZD are due to gravitational flow impeded in the unsaturated zone, which may nonnegligibly affect groundwater level changes. In the validation, a previous model without the consideration of unsaturated flow is benchmarked. The model is calibrated using multi-year groundwater data, and consistent model parameter statistics are obtained and validated. The estimation capability of the new model is superior to the benchmarked model as indicated by the significantly improved representation of groundwater level with physically interpretable model parameters.
      PubDate: 2017-04-06T15:05:51.670895-05:
      DOI: 10.1002/2016WR020177
       
  • Mixing layer and coherent structures in compound channel flows: Effects of
           transverse flow, velocity ratio, and vertical confinement
    • Authors: S. Proust; J. N. Fernandes, J.B. Leal, N. Rivière, Y. Peltier
      Abstract: Turbulent mixing layers associated with streamwise uniform and non-uniform flows in compound channels (main channel with adjacent floodplains) are experimentally investigated. The experiments start with uniform flow conditions. The streamwise non-uniformity is then generated by imposing an imbalance in the upstream discharge distribution between main channel (MC) and floodplains (FPs), keeping the total discharge constant, which results in a transverse depth-averaged mean flow. This study firstly aims at assessing the effect of a transverse flow on the mixing layer and coherent structures that form at the MC/FP interfaces. A wide range of initial velocity ratio or dimensionless shear between MC and FP is tested. The study secondly aims at assessing the effect of this velocity ratio on the mixing layer, for a fixed vertical confinement of flow. The total discharge was then varied to quantify the confinement effect. The results show that, far from the inlet section, Reynolds-stresses increase with local velocity ratio for a fixed confinement, and decrease with confinement for a fixed velocity ratio. It is also shown that, irrespective of confinement, the existence of quasi-two-dimensional coherent structures is driven by velocity ratio and the direction and magnitude of transverse flow. These structures cannot develop if velocity ratio is lower than 0.3 and if a strong transverse flow towards the MC occurs. In the latter case, the transverse flow is the predominant contribution to momentum exchange (compared with turbulent mixing and secondary currents), convex mean velocity profiles are observed, preventing the formation of quasi-two-dimensional structures.
      PubDate: 2017-04-06T15:05:48.793121-05:
      DOI: 10.1002/2016WR019873
       
  • Multiobjective reservoir operating rules based on cascade reservoir input
           variable selection method
    • Authors: Guang Yang; Shenglian Guo, Pan Liu, Liping Li, Chongyu Xu
      Abstract: The input variable selection in multi-objective cascade reservoir operation is an important and difficult task. To address this problem, this study proposes the cascade reservoir input variable selection (CIS) method that searches for the most valuable input variables for decision-making in multiple-objectivity cascade reservoir operations. From a case study of Hanjiang cascade reservoirs in China, we derive reservoir operating rules based on the combination of CIS and Gaussian radial basis functions (RBFs) methods, and optimize the rules through Pareto-archived dynamically dimensioned search (PA-DDS) with two objectives: to maximize both power generation and water supply. We select the most effective input variables and evaluate their impacts on cascade reservoir operations. From the simulated trajectories of reservoir water level, power generation, and water supply, we analyze the multi-objective operating rules with several input variables. The results demonstrate that the CIS method performs well in the selection of input variables for the cascade reservoir operation, and the RBFs method can fully express the non-linear operating rules for cascade reservoirs. We conclude that the CIS method is an effective and stable approach to identifying the most valuable information from a large number of candidate input variables. While the reservoir storage state is the most valuable information for the Hanjiang cascade reservoir multi-objective operation, the reservoir inflow is the most effective input variable for the single-objective operation of Danjiangkou.
      PubDate: 2017-04-06T15:05:45.957658-05:
      DOI: 10.1002/2016WR020301
       
  • Uncertainty analysis and risk-based design of detention basin without
           damage function
    • Authors: Yeou-Koung Tung
      Abstract: Risk-based analysis provides an economically defensible framework for determining the optimal design of hydrosystems with the minimum total cost including project cost (installation plus operation/maintenance/repair) and failure induced expected damage cost. However, failure related damage function with good quality may not be widely available in practical applications for assessing annual expected damage cost. In addition to aleatory uncertainty representing natural randomness of hydrologic events, there exists a variety of epistemic uncertainties due to knowledge deficiency from the use of inadequate models, inaccurate model parameters, etc. The presence of epistemic uncertainties could affect the loads and capacity of hydrosystem facilities which, in turn, would affect the value of failure induced physical performance indicators. Using detention basin design as an example, this paper presents a systematic framework to integrate aleatory and epistemic uncertainties for the risk-based design under the condition of no monetary damage function. For illustration, aleatory uncertainty due to randomness of rainfall intensity and epistemic uncertainties caused by runoff coefficient and curve number are considered in risk-based design of an example detention basin.
      PubDate: 2017-04-06T15:05:43.141259-05:
      DOI: 10.1002/2016WR020079
       
  • Lagrangian scheme to model subgrid-scale mixing and spreading in
           heterogeneous porous media
    • Authors: P. A. Herrera; J. M. Cortínez, A. J. Valocchi
      Abstract: Small-scale heterogeneity of permeability controls spreading, dilution, and mixing of solute plumes at large scale. However, conventional numerical simulations of solute transport are unable to resolve scales of heterogeneity below the grid-scale. We propose a Lagrangian numerical approach to implement closure models to account for subgrid-scale spreading and mixing in Darcy-scale numerical simulations of solute transport in mildly heterogeneous porous media. The novelty of the proposed approach is that it considers two different dispersion coefficients to account for advective spreading mechanisms and local-scale dispersion. Using results of benchmark numerical simulations we demonstrate that the proposed approach is able to model subgrid-scale spreading and mixing provided there is a correct choice of block-scale dispersion coefficient. We also demonstrate that for short travel times it is only possible to account for spreading or mixing using a single block-scale dispersion coefficient. Moreover, we show that it is necessary to use time-dependent dispersion coefficients to obtain correct mixing rates. On the contrary, for travel times that are large in comparison to the typical dispersive time scale, it is possible to use a single expression to compute the block-dispersion coefficient, which is equal to the asymptotic limit of the block-scale macro-dispersion coefficient proposed by Rubin et al. [1999]. Our approach provides a flexible and efficient way to model subgrid-scale mixing in numerical models of large-scale solute transport in heterogeneous aquifers. We expect that these findings will help to better understand the applicability of the advection-dispersion-equation (ADE) to simulate solute transport at the Darcy-scale in heterogeneous porous media.
      PubDate: 2017-04-01T09:25:33.125103-05:
      DOI: 10.1002/2016WR019994
       
  • Lagrangian simulation of mixing and reactions in complex geochemical
           systems
    • Authors: Nicholas B. Engdahl; David A. Benson, Diogo Bolster
      Abstract: Simulations of detailed geochemical systems have traditionally been restricted to Eulerian reactive transport algorithms. This note introduces a Lagrangian method for modeling multi-component reaction systems. The approach uses standard random walk based methods for the particle motion steps but allows the particles to interact with each other by exchanging mass of their various chemical species. The colocation density of each particle pair is used to calculate the mass transfer rate, which creates a local disequilibrium that is then relaxed back toward equilibrium using the reaction engine PhreeqcRM. The mass exchange is the only step where the particles interact and the remaining transport and reaction steps are entirely independent for each particle. Several validation examples are presented, which reproduce well-known analytical solutions. These are followed by two demonstration examples of a competitive decay chain and an acid-mine drainage system. The source code, entitled Complex Reaction on Particles (CRP), and files needed to run these examples are hosted openly on GitHub (https://github.com/nbengdahl/CRP), so as to enable interested readers to readily apply this approach with minimal modifications.
      PubDate: 2017-04-01T09:20:25.769559-05:
      DOI: 10.1002/2017WR020362
       
  • Let hydrologists learn the latest computer science by working with
           Research Software Engineers (RSEs) and not reinvent the waterwheel
           ourselves. A comment to “Most Computational Hydrology is not
           Reproducible, so is it Really Science?”
    • Authors: R. W. Hut; N. C. van de Giesen, N. Drost
      Abstract: The suggestions by Hutton et al. might not be enough to guarantee reproducible computational hydrology. Archiving software code and research data alone will not be enough. We add to the suggestion of Hutton et al. that hydrologists not only document their (computer) work, but that hydrologists use the latest best practices in designing research software, most notably the use of containers and open interfaces. To make sure hydrologists know of these best practices we urge close collaboration with Research Software Engineers (RSEs).
      PubDate: 2017-03-31T18:10:33.767783-05:
      DOI: 10.1002/2017WR020665
       
  • Numerical simulation of backward erosion piping in heterogeneous fields
    • Authors: Yue Liang; Tian-Chyi Jim Yeh, Yu-Li Wang, Mingwei Liu, Junjie Wang, Yonghong Hao
      Abstract: Backward erosion piping (BEP) is one of the major causes of seepage failures in levees. Seepage fields dictate the BEP behaviors and are influenced by the heterogeneity of soil properties. To investigate the effects of the heterogeneity on the seepage failures, we develop a numerical algorithm and conduct simulations to study BEP progressions in geologic media with spatially stochastic parameters. Specifically, the void ratio e, the hydraulic conductivity k, and the ratio of the particle contents r of the media are represented as the stochastic variables. They are characterized by means and variances, the spatial correlation structures, and the cross-correlation between variables. Results of the simulations reveal that the heterogeneity accelerates the development of preferential flow paths, which profoundly increase the likelihood of seepage failures. To account for unknown heterogeneity, we define the probability of the seepage instability (PI) to evaluate the failure potential of a given site. Using Monte-Carlo simulation (MCS), we demonstrate that the PI value is significantly influenced by the mean and the variance of lnk and its spatial correlation scales. While the other parameters, such as means and variances of e and r, and their cross-correlation, have minor impacts. Based on PI analyses, we introduce a risk rating system to classify the field into different regions according to risk levels. This rating system is useful for seepage failures prevention and assists decision making when BEP occurs.
      PubDate: 2017-03-31T18:10:30.501905-05:
      DOI: 10.1002/2017WR020425
       
  • A fully subordinated linear flow model for hillslope subsurface stormflow
    • Authors: Yong Zhang; Boris Baeumer, Li Chen, Donald M. Reeves, HongGuang Sun
      Abstract: Hillslope subsurface stormflow exhibits complex patterns when natural soils with multi-scale heterogeneity impart a spatiotemporally nonlocal memory on flow dynamics. To efficiently quantify such nonlocal flow responses, this technical note proposes a fully subordinated flow (FSF) equation where the time- and flow-subordination capture the temporal and spatial memory, respectively. Results show that the time-subordination component of the FSF model captures a wide range of delayed flow response due to various degrees of soil heterogeneity (especially for low-conductivity zones), while the model's flow-subordination term accounts for the rapid flow responses along preferential flow paths. In the FSF model, parameters defining spatiotemporal memory functions may be related to soil properties, while other parameters such as scalar factors controlling the overall advection and diffusion are difficult to predict and can be estimated from subsurface stormflow hydrographs. These parameters can be constants at the hillslope scale because the spatiotemporal subordination, an upscaling technique, can capture the impact of system heterogeneity on flow dynamics, leading to a linear FSF model that might be applicable for various slopes. Valid scale, limitation and extension of the FSF model, and modification of the model for other complex hydrological dynamics are also discussed.
      PubDate: 2017-03-31T18:10:26.94627-05:0
      DOI: 10.1002/2016WR020192
       
  • Bayesian calibration of groundwater models with input data uncertainty
    • Authors: Tianfang Xu; Albert J. Valocchi, Ming Ye, Feng Liang, Yu-Feng Lin
      Abstract: Effective water resources management typically relies on numerical models to analyze groundwater flow and solute transport processes. Groundwater models are often subject to input data uncertainty, as some inputs (such as recharge and well pumping rates) are estimated and subject to uncertainty. Current practices of groundwater model calibration often overlook uncertainties in input data; this can lead to biased parameter estimates and compromised predictions. Through a synthetic case study of surface-ground water interaction under changing pumping conditions and land use, we investigate the impacts of uncertain pumping and recharge rates on model calibration and uncertainty analysis. We then present a Bayesian framework of model calibration to handle uncertain input of groundwater models. The framework implements a marginalizing step to account for input data uncertainty when evaluating likelihood. It was found that not accounting for input uncertainty may lead to biased, overconfident parameter estimates because parameters could be over-adjusted to compensate for possible input data errors. Parameter compensation can have deleterious impacts when the calibrated model is used to make forecast under a scenario that is different from calibration conditions. By marginalizing input data uncertainty, the Bayesian calibration approach effectively alleviates parameter compensation and gives more accurate predictions in the synthetic case study. The marginalizing Bayesian method also decomposes prediction uncertainty into uncertainties contributed by parameters, input data and measurements. The results underscore the need to account for input uncertainty to better inform post-modeling decision making.
      PubDate: 2017-03-31T18:10:24.373418-05:
      DOI: 10.1002/2016WR019512
       
  • Pore network extraction from pore space images of various porous media
           systems
    • Authors: Z. X. Yi; M. Lin, W. B. Jiang, Z. B. Zhang, H. S. Li, J. Gao
      Abstract: Pore network extraction, which is defined as the transformation from irregular pore space to a simplified network in the form of pores connected by throats, is significant to microstructure analysis and network modeling. A physically realistic pore network is not only a representation of the pore space in the sense of topology and morphology, but also a good tool for predicting transport properties accurately. We present a method to extract pore network by employing the centrally located medial axis to guide the construction of maximal-balls-like skeleton where the pores and throats are defined and parameterized. To validate our method, various rock samples including sand pack, sandstones and carbonates were used to extract pore networks. The pore structures were compared quantitatively with the structures extracted by medial axis method or maximal ball method. The predicted absolute permeability and formation factor were verified against the theoretical solutions obtained by lattice Boltzmann method and finite volume method, respectively. The two-phase flow was simulated through the networks extracted from homogeneous sandstones, and the generated relative permeability curves were compared with the data obtained from experimental method and other numerical models. The results show that the accuracy of our network is higher than that of other networks for predicting transport properties, so the presented method is more reliable for extracting physically realistic pore network.
      PubDate: 2017-03-31T05:55:49.31285-05:0
      DOI: 10.1002/2016WR019272
       
  • Overtopping-induced failure of noncohesive, homogenous fluvial dikes
    • Authors: Ismail Rifai; Sebastien Erpicum, Pierre Archambeau, Damien Violeau, Michel Pirotton, Kamal El Kadi Abderrezzak, Benjamin Dewals
      Abstract: Accurate predictions of breach characteristics are necessary to reliably estimate the outflow hydrograph and the resulting inundation close to fluvial dikes. Laboratory experiments on the breaching of fluvial sand dikes were performed, considering a flow parallel to the dike axis. The breach was triggered by overtopping the dike crest. A detailed monitoring of the transient evolution of the breach geometry was conducted, providing key insights into the gradual and complex processes involved in fluvial dike failure. The breach develops in two phases: (1) the breach becomes gradually wider and deeper eroding on the downstream side along the main channel, and (2) breach widening controlled by side slope failures, continuing in the downstream direction only. Increasing the inflow discharge in the main channel, the breach formation time decreases significantly and the erosion occurs preferentially on the downstream side. The downstream boundary condition has a strong influence on the breach geometry and the resulting outflow hydrograph.
      PubDate: 2017-03-31T05:40:31.093044-05:
      DOI: 10.1002/2016WR020053
       
  • Introduction to special section on modeling highly heterogeneous aquifers:
           
    • Authors: J. Jaime Gómez-Hernández; James. J. Butler, Aldo Fiori, Diogo Bolster, Vladimir Cvetkovic, Gedeon Dagan, David Hyndman
      PubDate: 2017-03-31T05:40:24.083402-05:
      DOI: 10.1002/2017WR020774
       
  • Thermal effect of climate change on groundwater-fed ecosystems
    • Authors: Erick R. Burns; Yonghui Zhu, Hongbin Zhan, Michael Manga, Colin F. Williams, Steven E. Ingebritsen, Jason Dunham
      Abstract: Groundwater temperature changes will lag surface temperature changes from a changing climate. Steady-state solutions of the heat-transport equations are used to identify key processes that control the long-term thermal response of springs and other groundwater discharge to climate change, in particular changes in (1) groundwater recharge rate and temperature and (2) land-surface temperature transmitted through the vadose zone. Transient solutions are developed to estimate the time required for new thermal signals to arrive at ecosystems. The solution is applied to the volcanic Medicine Lake highlands, California, USA, and associated springs complexes that host groundwater-dependent ecosystems. In this system, upper-basin groundwater temperatures are strongly affected only by recharge conditions. However, as the vadose zone thins away from the highlands, changes in the average annual land-surface temperature also influence groundwater temperatures. Transient response to temperature change depends on both the conductive timescale and the rate at which recharge delivers heat. Most of the thermal response of groundwater at high elevations will occur within 20 years of a shift in recharge temperatures, but the large lower-elevation springs will respond more slowly, with about half of the conductive response occurring within the first 20 years and about half of the advective response to higher recharge temperatures occurring in approximately 60 years. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-30T03:46:09.111262-05:
      DOI: 10.1002/2016WR020007
       
  • Using Dual-Domain Advective-Transport Simulation to Reconcile Multiple
           Tracer Ages and Estimate Dual-Porosity Transport Parameters
    • Authors: Ward E. Sanford; L. Niel Plummer, Gerolamo Casile, Ed Busenberg, David L. Nelms, Peter Schlosser
      Abstract: Dual-domain transport is an alternative conceptual and mathematical paradigm to advection-dispersion for describing the movement of dissolved constituents in groundwater. Here we test the use of a dual-domain algorithm combined with advective pathline tracking to help reconcile environmental tracer concentrations measured in springs within the Shenandoah Valley, USA. The approach also allows for the estimation of the three dual-domain parameters: mobile porosity, immobile porosity, and a domain exchange rate constant. Concentrations of CFC-113, SF6, 3H, and 3He were measured at 28 springs emanating from carbonate rocks. The different tracers give three different mean composite piston-flow ages for all the springs that vary from 5 to 18 years. Here we compare four algorithms that interpret the tracer concentrations in terms of groundwater age: piston flow, old-fraction mixing, advective-flowpath modeling, and dual-domain modeling. Whereas the second two algorithms made slight improvements over piston flow at reconciling the disparate piston-flow age estimates, the dual-domain algorithm gave a very marked improvement. Optimal values for the three transport parameters were also obtained, although the immobile porosity value was not well constrained. Parameter correlation and sensitivities were calculated to help quantify the uncertainty. Although some correlation exists between the three parameters being estimated, a watershed simulation of a pollutant breakthrough to a local stream illustrates that the estimated transport parameters can still substantially help to constrain and predict the nature and timing of solute transport. The combined use of multiple environmental tracers with this dual-domain approach could be applicable in a wide variety of fractured-rock settings. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-30T03:46:06.967303-05:
      DOI: 10.1002/2016WR019469
       
  • Lake and wetland ecosystem services measuring water storage and local
           climate regulation
    • Authors: Christina P. Wong; Bo Jiang, Theodore J. Bohn, Kai N. Lee, Dennis P. Lettenmaier, Dongchun Ma, Zhiyun Ouyang
      Abstract: Developing interdisciplinary methods to measure ecosystem services is a scientific priority, however progress remains slow in part because we lack ecological production functions (EPFs) to quantitatively link ecohydrological processes to human benefits. In this study we tested a new approach, combining a process-based model with regression models, to create EPFs to evaluate water storage and local climate regulation from a green infrastructure project on the Yongding River in Beijing, China. Seven artificial lakes and wetlands were established to improve local water storage and human comfort; evapotranspiration (ET) regulates both services. Managers want to minimize the tradeoff between water losses and cooling to sustain water supplies while lowering the heat index (HI) to improve human comfort. We selected human benefit indicators using water storage targets and Beijing's HI, and the Variable Infiltration Capacity model to determine the change in ET from the new ecosystems. We created EPFs to quantify the ecosystem services as marginal values [Δfinal ecosystem service/Δecohydrological process]: (1) Δwater loss (lake evaporation/volume)/Δdepth and (2) Δsummer HI/ΔET. We estimate the new ecosystems increased local ET by 0.7 mm/day (20.3 W/m2) on the Yongding River. However ET rates are causing water storage shortfalls while producing no improvements in human comfort. The shallow lakes/wetlands are vulnerable to drying when inflow rates fluctuate, low depths lead to higher evaporative losses, causing water storage shortfalls with minimal cooling effects. We recommend managers make the lakes deeper to increase water storage, and plant shade trees to improve human comfort in the parks. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-30T03:46:02.474331-05:
      DOI: 10.1002/2016WR019445
       
  • Approximate Bayesian Computation methods for daily spatiotemporal
           precipitation occurrence simulation
    • Authors: Branden Olson; William Kleiber
      Abstract: Stochastic precipitation generators (SPGs) produce synthetic precipitation data and are frequently used to generate inputs for physical models throughout many scientific disciplines. Especially for large datasets, statistical parameter estimation is difficult due to the high dimensionality of the likelihood function. We propose techniques to estimate SPG parameters for spatiotemporal precipitation occurrence based on an emerging set of methods called Approximate Bayesian computation (ABC), which bypass the evaluation of a likelihood function. Our statistical model employs a thresholded Gaussian process that reduces to a probit regression at single sites. We identify appropriate ABC penalization metrics for our model parameters to produce simulations whose statistical characteristics closely resemble those of the observations. Spell length metrics are appropriate for single sites, while a variogram-based metric is proposed for spatial simulations. We present numerical case studies at sites in Colorado and Iowa where the estimated statistical model adequately reproduces local and domain statistics. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-28T11:20:35.949997-05:
      DOI: 10.1002/2016WR019741
       
  • Network structure classification and features of water distribution
           systems
    • Authors: Orazio Giustolisi; Antonietta Simone, Luca Ridolfi
      Abstract: The network connectivity structure of water distribution systems (WDSs) represents the domain where hydraulic processes occur, driving the emerging behavior of such systems, for example with respect to robustness and vulnerability. In complex network theory (CNT), a common way of classifying the network structure and connectivity is the association of the nodal degree distribution to specific probability distribution models; and during the last decades, researchers classified many real networks using the Poisson or Pareto distributions. In spite of the fact that degree-based network classification could play a crucial role to assess WDS vulnerability, this task is not easy because the network structure of WDSs is strongly constrained by spatial characteristics of the environment where they are constructed. The consequence of these spatial constraints is that the nodal degree spans very small ranges in WDSs hindering a reliable classification by the standard approach based on the nodal degree distribution. This work investigates the classification of the network structure of twenty-two real WDSs, built in different environments, demonstrating that the Poisson distribution generally models the degree distributions very well. In order to overcome the problem of the reliable classification based on the standard nodal degree, we define the “neighborhood” degree, equal to the sum of the nodal degrees of the nearest topological neighbors (i.e., the adjacent nodes). This definition of “neighborhood” degree is consistent with the fact that the degree of a single node is not significant for analysis of WDSs. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-28T11:20:32.760104-05:
      DOI: 10.1002/2016WR020071
       
  • A diagnostic approach to constraining flow partitioning in hydrologic
           models using a multi-objective optimization framework
    • Authors: Mahyar Shafii; Nandita Basu, James R. Craig, Sherry L. Schiff, Philippe Van Cappellen
      Abstract: Hydrologic models are often tasked with replicating historical hydrographs, but may do so without accurately reproducing the internal hydrological functioning of the watershed, including the flow partitioning, which is critical for predicting solute movement through the catchment. Here we propose a novel partitioning-focused calibration technique that utilizes flow partitioning coefficients developed based on the pioneering work of L'vovich [1979]. Our hypothesis is that inclusion of the L'vovich partitioning relations in calibration increases model consistency and parameter identifiability, and leads to superior model performance with respect to flow partitioning than using traditional hydrological signatures (e.g., flow duration curve indices) alone. The L'vovich approach partitions the annual precipitation into four components (quick flow, soil wetting, slow flow, and evapo-transpiration) and has been shown to work across a range of climatic and landscape settings. A new diagnostic multi-criteria model calibration methodology is proposed that first quantifies four calibration measures for watershed functions based on the L‘vovich theory, and then utilizes them as calibration criteria. The proposed approach is compared with a traditional hydrologic signature-based calibration for two conceptual bucket models. Results reveal that the proposed approach not only improves flow partitioning in the model compared to signature-based calibration, but is also capable of diagnosing flow partitioning inaccuracy and suggesting relevant model improvements. Furthermore, the proposed partitioning-based calibration approach is shown to increase parameter identifiability. This model calibration approach can be readily applied to other models. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-28T11:20:25.769657-05:
      DOI: 10.1002/2016WR019736
       
  • A numerical investigation into the importance of bed permeability on
           determining flow structures over river dunes
    • Authors: Sumit Sinha; Richard J. Hardy, Gianluca Blois, James L. Best, Gregory H. Sambrook Smith
      Abstract: Although permeable sediments dominate the majority of natural environments past work concerning bedform dynamics has considered the bed to be impermeable, and has generally neglected flow between the hyporheic zone and boundary layer. Herein, we present results detailing numerically modelled flow which allow the effects of bed permeability on bedform dynamics to be assessed.Simulation of an isolated impermeable bedform over a permeable bed shows that flow is forced into the bed upstream of the dune and returns to the boundary layer at the leeside, in the form of returning jets that generate horseshoe-shaped vortices. The returning flow significantly influences the leeside flow, modifying the separation zone, lifting the shear layer adjoining the separation zone away from the bed. Simulation of a permeable dune on a permeable bed reveals even greater modifications as the flow through the dune negates the formation of any flow separation in the leeside. With two dunes placed in series the flow over the downstream dune is influenced by the developing boundary layer on the leeside of the upstream dune. For the permeable bed case the upwelling flow lifts the separated flow from the bed, modifies the shear layer through the coalescence with vortices generated, and causes the shear layer to undulate rather than be parallel to the bed.These results demonstrate the significant effect that bed permeability has on the flow over bedforms that may be critical in affecting the flux of water and nutrients. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-23T04:00:58.174612-05:
      DOI: 10.1002/2016WR019662
       
  • Mixing as a driver of temporal variations in river hydrochemistry. Part 2:
           Major and trace element concentration dynamics in the Andes-Amazon
           transition
    • Authors: J. Jotautas Baronas; Mark A. Torres, Kathryn E. Clark, A. Joshua West
      Abstract: Variations in riverine solute chemistry with changing runoff are used to interrogate catchment hydrology and to investigate chemical reactions in Earth's critical zone. This approach requires some understanding of how spatial and temporal averaging of solute-generating reactions affect the dissolved load of rivers and streams. In this study, we investigate the concentration-runoff (C-Q) dynamics of a suite of major (Na, Mg, Ca, Si, K, and SO4) and trace (Al, Ba, Cd, Co, Cr, Cu, Fe, Ge, Li, Mn, Mo, Nd, Ni, Rb, Sr, U, V, and Zn) elements in nested catchments of variable size, spanning the geomorphic gradient from the Andes mountains to the Amazon foreland-floodplain. The major elements exhibit various degrees of dilution with increasing runoff at all sites, whereas the concentrations of most trace elements either increase or show no relationship with increasing runoff in the three larger catchments (160 to 28 000 km2 area). We show that the observed mainstem C-Q dynamics are influenced by variable mixing of tributaries with distinct C-Q relationships. Trace element C-Q relationships are more variable among tributaries relative to major elements, which could be the result of variations in geomorphology, lithology, and hydrology of the sub-catchments. Certain trace metals are also lost from solution during in-channel processes (possibly related to colloidal size-partitioning), which may exert an additional control on C-Q dynamics. Overall, we suggest that aggregation effects should be assessed in heterogeneous catchments before C-Q or ratio-Q relationships can be interpreted as reflecting catchment-wide solute generation processes and their relationship to hydrology. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-17T19:15:39.992386-05:
      DOI: 10.1002/2016WR019729
       
  • Mixing as a driver of temporal variations in river hydrochemistry. Part 1:
           Insights from conservative tracers in the Andes-Amazon transition
    • Authors: Mark A. Torres; J. Jotautas Baronas, Kathryn E. Clark, Sarah J. Feakins, A. Joshua West
      Abstract: The response of hillslope processes to changes in precipitation may drive the observed changes in the solute geochemistry of rivers with discharge. This conjecture is most robust when variations in the key environmental factors that affect hillslope processes (e.g., lithology, erosion rate, and climate) are minimal across a river's catchment area. For rivers with heterogenous catchments, temporal variations in the relative contributions of different tributary sub-catchments may modulate variations in solute geochemistry with runoff. In the absence of a dense network of hydrologic gauging stations, alternative approaches are required to distinguish between the different drivers of temporal variability in river solute concentrations. In this contribution, we apportion the water and solute fluxes of a reach of the Madre de Dios River (Peru) between its four major tributary sub-catchments during two sampling campaigns (wet and dry seasons) using spatial variations in conservative tracers. Guided by the results of a mixing model, we identify temporal variations in solute concentrations of the mainstem Madre de Dios that are due to changes in the relative contributions of each tributary. Our results suggest that variations in tributary mixing are, in part, responsible for the observed concentration-discharge (C-Q) relationships. The implications of these results are further explored by re-analyzing previously published C-Q data from this region, developing a theoretical model of tributary mixing, and, in a companion paper, comparing the C-Q behavior of a suite of major and trace elements in the Madre de Dios River system. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-17T19:15:31.304506-05:
      DOI: 10.1002/2016WR019733
       
  • A new model for predicting the drag exerted by vegetation canopies
    • Authors: Vahid Etminan; Ryan J. Lowe, Marco Ghisalberti
      Abstract: The influence of vegetation canopies on the flow structure in streams, rivers and floodplains is heavily dependent on the cumulative drag forces exerted by the vegetation. The drag coefficient of vegetation elements within a canopy has been shown to be significantly different to well-established values for a single element in isolation. This study investigates the mechanisms that determine canopy flow resistance and proposes a new model for predicting canopy drag coefficients. Large Eddy Simulations were used to investigate the fine-scale hydrodynamics within emergent canopies with solid area fractions (λ) ranging from 0.016 to 0.25. The influence of three mechanisms in modifying canopy drag, namely blockage, sheltering and delayed separation, were investigated. While the effects of sheltering and delayed separation were found to slightly reduce the drag of very sparse canopies, the blockage effect significantly increased the drag of denser canopies (λ ≳ 0.04). Furthermore, an analogy drawn between canopy flow and wall-confined flow around bluff bodies is used to propose an alternative reference velocity to the conventional spatially-averaged velocity, namely the constricted cross-section velocity (Uc), to redefine the canopy drag coefficient. Through comparison with both prior experimental data and the present numerical simulations, typical formulations for the drag coefficient of a single cylinder are shown to accurately predict the drag coefficient of staggered emergent canopies when Uc is used as the reference velocity. Finally, it is shown that this new model can be extended to predict the bulk drag coefficient of randomly-arranged vegetation canopies. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-11T03:45:32.914639-05:
      DOI: 10.1002/2016WR020090
       
  • Development of a Water and Enthalpy Budget-based Glacier mass balance
           Model (WEB-GM) and its preliminary validation
    • Authors: Baohong Ding; Kun Yang, Wei Yang, Xiaobo He, Yingying Chen, Zhu La, Xiaofeng Guo, Lei Wang, Hui Wu, Tandong Yao
      Abstract: This paper presents a new water and energy budget-based glacier mass balance model. Enthalpy, rather than temperature, is used in the energy balance equations to simplify the computation of the energy transfers through the water phase change and the movement of liquid water in the snow. A new parameterization for albedo estimation and state-of-the-art parameterization schemes for rainfall/snowfall type identification and surface turbulent heat flux calculations are implemented in the model. This model was driven with meteorological data and evaluated using mass balance and turbulent flux data collected during a field experiment implemented in the ablation zone of the Parlung No. 4 Glacier on the Southeast Tibetan Plateau during 2009 and 2015–2016. The evaluation shows that the model can reproduce the observed glacier ablation depth, surface albedo, surface temperature, sensible heat flux, and latent heat flux with high accuracy. Comparing with a traditional energy budget-based glacier mass balance model, this enthalpy-based model shows a superior capacity in simulation accuracy. Therefore, this model can reasonably simulate the energy budget and mass balance of glacier melting in this region and be used as a component of land surface models and hydrological models. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-09T19:07:11.799814-05:
      DOI: 10.1002/2016WR018865
       
  • Tropical river suspended sediment and solute dynamics in storms during an
           extreme drought
    • Authors: Kathryn E. Clark; James B. Shanley, Martha A. Scholl, Nicolas Perdrial, Julia N. Perdrial, Alain F. Plante, William H. McDowell
      Abstract: Droughts, which can strongly affect both hydrologic and biogeochemical systems, are projected to become more prevalent in the tropics in the future. We assessed the effects of an extreme drought during 2015 on stream water composition in the Luquillo Mountains of Puerto Rico. We demonstrated that drought baseflow in the months leading up to the study was sourced from trade-wind orographic rainfall, suggesting a resistance to the effects of an otherwise extreme drought. In two catchments (Mameyes and Icacos), we sampled a series of four rewetting events that partially alleviated the drought. We collected and analyzed dissolved constituents (major cations and anions, organic carbon and nitrogen) and suspended sediment [inorganic and organic matter (particulate organic carbon and particulate nitrogen)]. The rivers appeared to be resistant to extreme drought, recovering quickly upon rewetting, as 1) the concentration - discharge (C-Q) relationships deviated little from the long-term patterns; 2) “new water” dominated streamflow during the latter events; 3) suspended sediment sources had accumulated in the channel during the drought flushed out during the initial events; and 4) the severity of the drought, as measured by the US drought monitor, was reduced dramatically after the rewetting events. Through this interdisciplinary study we were able to investigate the impact of extreme drought through rewetting events on the river biogeochemistry. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-09T18:57:06.989544-05:
      DOI: 10.1002/2016WR019737
       
  • A new drought index that considers the joint effects of climate and land
           surface change
    • Authors: Meixian Liu; Xianli Xu, Chaohao Xu, Alexander Y. Sun, Kelin Wang, Bridget R. Scanlon, Lu Zhang
      Abstract: This study proposes a hydrological drought index, the standardized wetness index (SWI), by combining the structure of the Standardized Precipitation-Evapotranspiration Index and actual-evaporation-based residual water-energy ratio, in which actual evaporation is estimated using the Budyko hypothesis. The SWI requires three parameters, precipitation, potential evaporation, and parameter n of a Budyko-type formulae. Based on different types of n (fixed or dynamic), SWI can be used to estimate the dryness/wetness resulting from climate change (variability) solely, and from the joint effects of climate and land surface change (variability). Performance of SWI is evaluated using historical droughts and by comparing to the self-calibrated Palmer Drought Severity Index. Results show that SWI effectively captures global droughts. Furthermore, a case study in two catchments with significant land surface modification, indicates that the joint effects of climate and land surface have greater impacts on dryness/wetness in the water-limited Wuding catchment than in the energy-limited Poyang catchment. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-07T19:45:27.468069-05:
      DOI: 10.1002/2016WR020178
       
  • Groundwater similarity across a watershed derived from time-warped and
           flow-corrected time series
    • Authors: M. Rinderer; B. L. McGlynn, H.J. van Meerveld
      Abstract: Information about catchment-scale groundwater dynamics is necessary to understand how catchments store and release water and why water quantity and quality varies in streams. However, groundwater level monitoring is often restricted to a limited number of sites. Knowledge of the factors that determine similarity between monitoring sites can be used to predict catchment-scale groundwater storage and connectivity of different runoff source areas. We used distance-based and correlation-based similarity measures to quantify the spatial and temporal differences in shallow groundwater similarity for 51 monitoring sites in a Swiss pre-alpine catchment. The 41 months long time series were pre-processed using dynamic time-warping and a flow-corrected time transformation to account for small timing differences and bias towards low-flow periods. The mean distance-based groundwater similarity was correlated to topographic indices, such as upslope contributing area, Topographic Wetness Index and local slope. Correlation-based similarity was less related to landscape position but instead revealed differences between seasons. Analysis of Variance and Partial Mantel tests showed that landscape position, represented by the Topographic Wetness Index, explained 52% of the variability in mean distance-based groundwater similarity, while spatial distance, represented by the Euclidean distance, explained only 5%. The variability in distance-based similarity and correlation-based similarity between groundwater and streamflow time series was significantly larger for midslope locations than for other landscape positions. This suggests, that groundwater dynamics at these midslope sites, which are important in order to understand runoff source areas and hydrological connectivity at the catchment-scale, are most difficult to predict. This article is protected by copyright. All rights reserved.
      PubDate: 2017-03-02T12:30:25.364245-05:
      DOI: 10.1002/2016WR019856
       
  • Issue Information
    • Pages: 2577 - 2580
      PubDate: 2017-05-18T10:07:09.665736-05:
      DOI: 10.1002/wrcr.22251
       
  • The future of evapotranspiration: Global requirements for ecosystem
           functioning, carbon and climate feedbacks, agricultural management, and
           water resources
    • Authors: Joshua B. Fisher; Forrest Melton, Elizabeth Middleton, Christopher Hain, Martha Anderson, Richard Allen, Matthew F. McCabe, Simon Hook, Dennis Baldocchi, Philip A. Townsend, Ayse Kilic, Kevin Tu, Diego D. Miralles, Johan Perret, Jean-Pierre Lagouarde, Duane Waliser, Adam J. Purdy, Andrew French, David Schimel, James S. Famiglietti, Graeme Stephens, Eric F. Wood
      Pages: 2618 - 2626
      Abstract: The fate of the terrestrial biosphere is highly uncertain given recent and projected changes in climate. This is especially acute for impacts associated with changes in drought frequency and intensity on the distribution and timing of water availability. The development of effective adaptation strategies for these emerging threats to food and water security are compromised by limitations in our understanding of how natural and managed ecosystems are responding to changing hydrological and climatological regimes. This information gap is exacerbated by insufficient monitoring capabilities from local to global scales. Here, we describe how evapotranspiration (ET) represents the key variable in linking ecosystem functioning, carbon and climate feedbacks, agricultural management, and water resources, and highlight both the outstanding science and applications questions and the actions, especially from a space-based perspective, necessary to advance them.
      PubDate: 2017-04-10T05:08:15.085365-05:
      DOI: 10.1002/2016WR020175
       
  • Preferences for policy attributes and willingness to pay for water quality
           improvements under uncertainty
    • Authors: Jeffrey D. Mullen; Kayla C. Calhoun, Gregory J. Colson
      Pages: 2627 - 2642
      Abstract: When exploring environmental policy options, sometimes neither the current state of the environmental good being analyzed nor the effectiveness of the proposed policy is known with certainty. This is the case with privately owned, residential, onsite wastewater treatment systems (septic systems)—there is ample evidence that they can contribute to water quality impairment, but their contribution is generally stochastic in nature and the efficacy of technological solutions is uncertain. Furthermore, the benefits of ameliorating water quality impairments are public in nature. Septic system owners are legally responsible for maintaining their systems, but requiring them to upgrade otherwise properly functioning tanks is outside the scope of water quality regulations. An incentive structure is necessary to induce private homeowners to invest in septic upgrades that deliver both private benefits in addition to the positive externality for the wider public and environment. The question for policy makers is how these private incentives should be financed, and whether public support can be garnered. Results of a choice experiment in Gwinnett County, Georgia, accounting for both sources of uncertainty—the current state of water quality and the efficacy of the intervention—in the design of water quality policy are presented. We find baseline water quality conditions and policy efficacy significantly affect public support for a policy transferring public funds to private homeowners, in terms of both sentiment and willingness to pay. The manner in which costs are shared across stakeholders also affects the selection of a policy option, but not willingness to pay for it.
      PubDate: 2017-04-02T12:40:27.591678-05:
      DOI: 10.1002/2016WR019397
       
  • Changes in cold region flood regimes inferred from long-record reference
           gauging stations
    • Authors: Donald H. Burn; Paul H. Whitfield
      Pages: 2643 - 2658
      Abstract: Variability and nonstationarity in flood regimes of cold regions are examined using data from hydrometric reference streamflow gauging stations from 27 natural watersheds in Canada and adjacent areas of the United States. Choosing stations from reference networks with nearly 100 years of data allows for the investigation of changes that span several phases of some of the atmospheric drivers that may influence flood behavior. The reference hydrologic networks include only stations considered to have good quality data and were screened to avoid the influences of regulation, diversions, or land use change. Changes and variations in flood regimes are complex and require a multifaceted approach to properly characterize the types of changes that have occurred and are likely to occur in the future. Peaks over threshold (POT) data are extracted from daily flow data for each watershed, and changes to the magnitude, timing, frequency, volume, and duration of threshold exceedences are investigated. Seasonal statistics are used to explore changes in the nature of the flood regime based on changes in the timing of flood threshold exceedences. A variety of measures are developed to infer flood regime shifts including from a nival regime to a mixed regime and a mixed regime to a more pluvial-dominated regime. The flood regime at many of the watersheds demonstrates increased prominence of rainfall floods and decreased prevalence of snowmelt contributions to flood responses. While some individual stations show a relationship between flood variables and climate indices, these relationships are generally weak.
      PubDate: 2017-04-02T12:40:37.564376-05:
      DOI: 10.1002/2016WR020108
       
  • A regional and nonstationary model for partial duration series of extreme
           rainfall
    • Authors: Ida Bülow Gregersen; Henrik Madsen, Dan Rosbjerg, Karsten Arnbjerg-Nielsen
      Pages: 2659 - 2678
      Abstract: Regional extreme value models for estimation of extreme rainfall intensities are widely applied, but their underlying assumption of stationarity is challenged. Many recent studies show that the rainfall extremes worldwide exhibit a nonstationary behavior. This paper presents a spatiotemporal model of extreme rainfall. The framework is built on a partial duration series approach with a nonstationary, regional threshold value. The model is based on generalized linear regression solved by generalized estimation equations. It allows a spatial correlation between the stations in the network and accounts furthermore for variable observation periods at each station and in each year. Marginal regional and temporal regression models solved by generalized least squares are used to validate and discuss the results of the full spatiotemporal model. The model is applied on data from a large Danish rain gauge network for four durations ranging from 10 min to 24 h. The observation period differs between stations, and the number of stations with more than 10 years of observations has increased over the years. A spatiotemporal model for the threshold is suggested, applying the mean annual precipitation and time as the explanatory variables in the regional and temporal domain, respectively. Further analysis of partial duration series with nonstationary and regional thresholds shows that the mean exceedances also exhibit a significant variation in space and time for some rainfall durations, while the shape parameter is found to be constant.
      PubDate: 2017-04-02T12:40:44.061371-05:
      DOI: 10.1002/2016WR019554
       
  • Potential effects of landscape change on water supplies in the presence of
           reservoir storage
    • Authors: Andrew J. Guswa; Perrine Hamel, P. James Dennedy-Frank
      Pages: 2679 - 2692
      Abstract: This work presents a set of methods to evaluate the potential effects of landscape changes on water supplies. Potential impacts are a function of the seasonality of precipitation, losses of water to evapotranspiration and deep recharge, the flow-regulating ability of watersheds, and the availability of reservoir storage. For a given reservoir capacity, simple reservoir simulations with daily precipitation and streamflow enable the determination of the maximum steady supply of water for both the existing watershed and a hypothetical counter-factual that has neither flow-regulating benefits nor any losses. These two supply values, representing land use end-members, create an envelope that defines the water-supply service and bounds the effect of landscape change on water supply. These bounds can be used to discriminate between water supplies that may be vulnerable to landscape change and those that are unlikely to be affected. Two indices of the water-supply service exhibit substantial variability across 593 watersheds in the continental United States. Rcross, the reservoir capacity at which landscape change is unlikely to have any detrimental effect on water supply has an interquartile range of 0.14–4% of mean-annual-streamflow. Steep, forested watersheds with seasonal climates tend to have greater service values, and the indices of water-supply service are positively correlated with runoff ratios during the months with lowest flows.
      PubDate: 2017-04-02T12:40:34.596327-05:
      DOI: 10.1002/2016WR019691
       
  • Field estimates of groundwater circulation depths in two mountainous
           watersheds in the western U.S. and the effect of deep circulation on
           solute concentrations in streamflow
    • Authors: Marty D. Frisbee; Douglas G. Tolley, John L. Wilson
      Pages: 2693 - 2715
      Abstract: Estimates of groundwater circulation depths based on field data are lacking. These data are critical to inform and refine hydrogeologic models of mountainous watersheds, and to quantify depth and time dependencies of weathering processes in watersheds. Here we test two competing hypotheses on the role of geology and geologic setting in deep groundwater circulation and the role of deep groundwater in the geochemical evolution of streams and springs. We test these hypotheses in two mountainous watersheds that have distinctly different geologic settings (one crystalline, metamorphic bedrock and the other volcanic bedrock). Estimated circulation depths for springs in both watersheds range from 0.6 to 1.6 km and may be as great as 2.5 km. These estimated groundwater circulation depths are much deeper than commonly modeled depths suggesting that we may be forcing groundwater flow paths too shallow in models. In addition, the spatial relationships of groundwater circulation depths are different between the two watersheds. Groundwater circulation depths in the crystalline bedrock watershed increase with decreasing elevation indicative of topography-driven groundwater flow. This relationship is not present in the volcanic bedrock watershed suggesting that both the source of fracturing (tectonic versus volcanic) and increased primary porosity in the volcanic bedrock play a role in deep groundwater circulation. The results from the crystalline bedrock watershed also indicate that relatively deep groundwater circulation can occur at local scales in headwater drainages less than 9.0 km2 and at larger fractions than commonly perceived. Deep groundwater is a primary control on streamflow processes and solute concentrations in both watersheds.
      PubDate: 2017-04-04T00:15:44.352292-05:
      DOI: 10.1002/2016WR019553
       
  • Steady state fractionation of heavy noble gas isotopes in a deep
           unsaturated zone
    • Authors: Alan M. Seltzer; Jeffrey P. Severinghaus, Brian J. Andraski, David A. Stonestrom
      Pages: 2716 - 2732
      Abstract: To explore steady state fractionation processes in the unsaturated zone (UZ), we measured argon, krypton, and xenon isotope ratios throughout a ∼110 m deep UZ at the United States Geological Survey (USGS) Amargosa Desert Research Site (ADRS) in Nevada, USA. Prior work has suggested that gravitational settling should create a nearly linear increase in heavy-to-light isotope ratios toward the bottom of stagnant air columns in porous media. Our high-precision measurements revealed a binary mixture between (1) expected steady state isotopic compositions and (2) unfractionated atmospheric air. We hypothesize that the presence of an unsealed pipe connecting the surface to the water table allowed for direct inflow of surface air in response to extensive UZ gas sampling prior to our first (2015) measurements. Observed isotopic resettling in deep UZ samples collected a year later, after sealing the pipe, supports this interpretation. Data and modeling each suggest that the strong influence of gravitational settling and weaker influences of thermal diffusion and fluxes of CO2 and water vapor accurately describe steady state isotopic fractionation of argon, krypton, and xenon within the UZ. The data confirm that heavy noble gas isotopes are sensitive indicators of UZ depth. Based on this finding, we outline a potential inverse approach to quantify past water table depths from noble gas isotope measurements in paleogroundwater, after accounting for fractionation during dissolution of UZ air and bubbles.
      PubDate: 2017-04-06T04:29:16.482511-05:
      DOI: 10.1002/2016WR019655
       
  • The mechanistic basis for storage-dependent age distributions of water
           discharged from an experimental hillslope
    • Authors: Luke A. Pangle; Minseok Kim, Charlene Cardoso, Marco Lora, Antonio A. Meira Neto, Till H. M. Volkmann, Yadi Wang, Peter A Troch, Ciaran J. Harman
      Pages: 2733 - 2754
      Abstract: Distributions of water transit times (TTDs), and related storage-selection (SAS) distributions, are spatially integrated metrics of hydrological transport within landscapes. Recent works confirm that the form of TTDs and SAS distributions should be considered time variant—possibly depending, in predictable ways, on the dynamic storage of water within the landscape. We report on a 28 day periodic-steady-state-tracer experiment performed on a model hillslope contained within a 1 m3 sloping lysimeter. Using experimental data, we calibrate physically based, spatially distributed flow and transport models, and use the calibrated models to generate time-variable SAS distributions, which are subsequently compared to those directly observed from the actual experiment. The objective is to use the spatially distributed estimates of storage and flux from the model to characterize how temporal variation in water storage influences temporal variation in flow path configurations, and resulting SAS distributions. The simulated SAS distributions mimicked well the shape of observed distributions, once the model domain reflected the spatial heterogeneity of the lysimeter soil. The spatially distributed flux vectors illustrate how the magnitude and directionality of water flux changes as the water table surface rises and falls, yielding greater contributions of younger water when the water table surface rises nearer to the soil surface. The illustrated mechanism is compliant with conclusions drawn from other recent studies and supports the notion of an inverse-storage effect, whereby the probability of younger water exiting the system increases with storage. This mechanism may be prevalent in hillslopes and headwater catchments where discharge dynamics are controlled by vertical fluctuations in the water table surface of an unconfined aquifer.
      PubDate: 2017-04-06T23:50:53.774071-05:
      DOI: 10.1002/2016WR019901
       
  • Gas bubble size estimation in peat soils from EM wave scattering observed
           with ground penetrating radar
    • Authors: Neil Terry; Lee Slater
      Pages: 2755 - 2769
      Abstract: The size of biogenic gas bubbles in peatlands is believed to regulate ebullition of carbon gases to the atmosphere. The measurement of electromagnetic (EM) wave travel times using ground penetrating radar (GPR) is a proven field-scale method for indirect estimation of volumetric gas content. However, there is also the possibility that information on the size of the gas bubbles can be determined from the analysis of the spectral content of GPR signals as scattering attenuation possesses a frequency dependence for bubbles smaller than the EM wavelength (Rayleigh-type scattering). Theoretical modeling shows that GPR data acquired with typical antenna frequencies are likely to be affected by bubble size in peat soils. Analysis of GPR data from two recent studies on peat monoliths where biogenic gas production was documented produced results consistent with the model predictions. Using the approach, zero offset cross-borehole GPR data in a northern peatland suggest that large bubble clusters (i.e., 0.05 m radius) occur in peat. These findings broaden the utility of GPR for providing information on biogenic gas dynamics in peatlands.
      PubDate: 2017-04-06T23:50:39.104678-05:
      DOI: 10.1002/2016WR019783
       
  • Quantifying local rainfall dynamics and uncertain boundary conditions into
           a nested regional-local flood modeling system
    • Authors: María Bermúdez; Jeffrey C. Neal, Paul D. Bates, Gemma Coxon, Jim E. Freer, Luis Cea, Jeronimo Puertas
      Pages: 2770 - 2785
      Abstract: Inflow discharge and outflow stage estimates for hydraulic flood models are generally derived from river gauge data. Uncertainties in the measured inflow data and the neglect of rainfall-runoff contributions to the modeled domain downstream of the gauging locations can have a significant impact on these estimated “whole reach” inflows and consequently on flood predictions. In this study, a method to incorporate rating curve uncertainty and local rainfall-runoff dynamics into the predictions of a reach-scale flood model is proposed. The methodology is applied to the July 2007 floods of the River Severn in UK. Discharge uncertainty bounds are generated applying a nonparametric local weighted regression approach to stage-discharge measurements for two gauging stations. Measured rainfall downstream from these locations is used as input to a series of subcatchment regional hydrological model to quantify additional local inflows along the main channel. A regional simplified-physics hydraulic model is then applied to combine these contributions and generate an ensemble of discharge and water elevation time series at the boundaries of a local-scale high complexity hydraulic model. Finally, the effect of these rainfall dynamics and uncertain boundary conditions are evaluated on the local-scale model. Accurate prediction of the flood peak was obtained with the proposed method, which was only possible by resolving the additional complexity of the extreme rainfall contributions over the modeled area. The findings highlight the importance of estimating boundary condition uncertainty and local rainfall contributions for accurate prediction of river flows and inundation at regional scales.
      PubDate: 2017-04-07T04:17:03.185941-05:
      DOI: 10.1002/2016WR019903
       
  • Developing reservoir monthly inflow forecasts using artificial
           intelligence and climate phenomenon information
    • Authors: Tiantian Yang; Ata Akbari Asanjan, Edwin Welles, Xiaogang Gao, Soroosh Sorooshian, Xiaomang Liu
      Pages: 2786 - 2812
      Abstract: Reservoirs are fundamental human-built infrastructures that collect, store, and deliver fresh surface water in a timely manner for many purposes. Efficient reservoir operation requires policy makers and operators to understand how reservoir inflows are changing under different hydrological and climatic conditions to enable forecast-informed operations. Over the last decade, the uses of Artificial Intelligence and Data Mining [AI & DM] techniques in assisting reservoir streamflow subseasonal to seasonal forecasts have been increasing. In this study, Random Forest [RF), Artificial Neural Network (ANN), and Support Vector Regression (SVR) are employed and compared with respect to their capabilities for predicting 1 month-ahead reservoir inflows for two headwater reservoirs in USA and China. Both current and lagged hydrological information and 17 known climate phenomenon indices, i.e., PDO and ENSO, etc., are selected as predictors for simulating reservoir inflows. Results show (1) three methods are capable of providing monthly reservoir inflows with satisfactory statistics; (2) the results obtained by Random Forest have the best statistical performances compared with the other two methods; (3) another advantage of Random Forest algorithm is its capability of interpreting raw model inputs; (4) climate phenomenon indices are useful in assisting monthly or seasonal forecasts of reservoir inflow; and (5) different climate conditions are autocorrelated with up to several months, and the climatic information and their lags are cross correlated with local hydrological conditions in our case studies.
      PubDate: 2017-04-07T04:17:28.744496-05:
      DOI: 10.1002/2017WR020482
       
  • The impact of sedimentary anisotropy on solute mixing in stacked
           scour-pool structures
    • Authors: Jeremy P. Bennett; Claus P. Haslauer, Olaf A. Cirpka
      Pages: 2813 - 2832
      Abstract: The spatial variability of hydraulic conductivity is known to have a strong impact on solute spreading and mixing. In most investigations, its local anisotropy has been neglected. Recent studies have shown that spatially varying orientation in sedimentary anisotropy can lead to twisting flow enhancing transverse mixing, but most of these studies used geologically implausible geometries. We use an object-based approach to generate stacked scour-pool structures with either isotropic or anisotropic filling which are typically reported in glacial outwash deposits. We analyze how spatially variable isotropic conductivity and variation of internal anisotropy in these features impacts transverse plume deformation and both longitudinal and transverse spreading and mixing. In five test cases, either the scalar values of conductivity or the spatial orientation of its anisotropy is varied between the scour-pool structures. Based on 100 random configurations, we compare the variability of velocity components, stretching and folding metrics, advective travel-time distributions, one and two-particle statistics in advective-dispersive transport, and the flux-related dilution indices for steady state advective-dispersive transport among the five test cases. Variation in the orientation of internal anisotropy causes strong variability in the lateral velocity components, which leads to deformation in transverse directions and enhances transverse mixing, whereas it hardly affects the variability of the longitudinal velocity component and thus longitudinal spreading and mixing. The latter is controlled by the spatial variability in the scalar values of hydraulic conductivity. Our results demonstrate that sedimentary anisotropy is important for transverse mixing, whereas it may be neglected when considering longitudinal spreading and mixing.
      PubDate: 2017-04-07T01:57:15.300698-05:
      DOI: 10.1002/2016WR019665
       
  • Peaks Over Threshold (POT): A methodology for automatic threshold
           estimation using goodness of fit p-value
    • Authors: Sebastián Solari; Marta Egüen, María José Polo, Miguel A. Losada
      Pages: 2833 - 2849
      Abstract: Threshold estimation in the Peaks Over Threshold (POT) method and the impact of the estimation method on the calculation of high return period quantiles and their uncertainty (or confidence intervals) are issues that are still unresolved. In the past, methods based on goodness of fit tests and EDF-statistics have yielded satisfactory results, but their use has not yet been systematized. This paper proposes a methodology for automatic threshold estimation, based on the Anderson-Darling EDF-statistic and goodness of fit test. When combined with bootstrapping techniques, this methodology can be used to quantify both the uncertainty of threshold estimation and its impact on the uncertainty of high return period quantiles. This methodology was applied to several simulated series and to four precipitation/river flow data series. The results obtained confirmed its robustness. For the measured series, the estimated thresholds corresponded to those obtained by nonautomatic methods. Moreover, even though the uncertainty of the threshold estimation was high, this did not have a significant effect on the width of the confidence intervals of high return period quantiles.
      PubDate: 2017-04-07T02:01:41.050841-05:
      DOI: 10.1002/2016WR019426
       
  • Incorporating geologic information into hydraulic tomography: A general
           framework based on geostatistical approach
    • Authors: Yuanyuan Zha; Tian-Chyi J. Yeh, Walter A. Illman, Hironori Onoe, Chin Man W. Mok, Jet-Chau Wen, Shao-Yang Huang, Wenke Wang
      Pages: 2850 - 2876
      Abstract: Hydraulic tomography (HT) has become a mature aquifer test technology over the last two decades. It collects nonredundant information of aquifer heterogeneity by sequentially stressing the aquifer at different wells and collecting aquifer responses at other wells during each stress. The collected information is then interpreted by inverse models. Among these models, the geostatistical approaches, built upon the Bayesian framework, first conceptualize hydraulic properties to be estimated as random fields, which are characterized by means and covariance functions. They then use the spatial statistics as prior information with the aquifer response data to estimate the spatial distribution of the hydraulic properties at a site. Since the spatial statistics describe the generic spatial structures of the geologic media at the site rather than site-specific ones (e.g., known spatial distributions of facies, faults, or paleochannels), the estimates are often not optimal. To improve the estimates, we introduce a general statistical framework, which allows the inclusion of site-specific spatial patterns of geologic features. Subsequently, we test this approach with synthetic numerical experiments. Results show that this approach, using conditional mean and covariance that reflect site-specific large-scale geologic features, indeed improves the HT estimates. Afterward, this approach is applied to HT surveys at a kilometer-scale-fractured granite field site with a distinct fault zone. We find that by including fault information from outcrops and boreholes for HT analysis, the estimated hydraulic properties are improved. The improved estimates subsequently lead to better prediction of flow during a different pumping test at the site.
      PubDate: 2017-04-08T03:01:37.32315-05:0
      DOI: 10.1002/2016WR019185
       
  • Modeling complex flow structures and drag around a submerged plant of
           varied posture
    • Authors: Richard J. Boothroyd; Richard J. Hardy, Jeff Warburton, Timothy I. Marjoribanks
      Pages: 2877 - 2901
      Abstract: Although vegetation is present in many rivers, the bulk of past work concerned with modeling the influence of vegetation on flow has considered vegetation to be morphologically simple and has generally neglected the complexity of natural plants. Here we report on a combined flume and numerical model experiment which incorporates time-averaged plant posture, collected through terrestrial laser scanning, into a computational fluid dynamics model to predict flow around a submerged riparian plant. For three depth-limited flow conditions (Reynolds number = 65,000–110,000), plant dynamics were recorded through high-definition video imagery, and the numerical model was validated against flow velocities collected with an acoustic Doppler velocimeter. The plant morphology shows an 18% reduction in plant height and a 14% increase in plant length, compressing and reducing the volumetric canopy morphology as the Reynolds number increases. Plant shear layer turbulence is dominated by Kelvin-Helmholtz type vortices generated through shear instability, the frequency of which is estimated to be between 0.20 and 0.30 Hz, increasing with Reynolds number. These results demonstrate the significant effect that the complex morphology of natural plants has on in-stream drag, and allow a physically determined, species-dependent drag coefficient to be calculated. Given the importance of vegetation in river corridor management, the approach developed here demonstrates the necessity to account for plant motion when calculating vegetative resistance.
      PubDate: 2017-04-08T05:31:42.446763-05:
      DOI: 10.1002/2016WR020186
       
  • Posterior population expansion for solving inverse problems
    • Authors: C. Jäggli; J. Straubhaar, P. Renard
      Pages: 2902 - 2916
      Abstract: Solving inverse problems in a complex, geologically realistic, and discrete model space and from a sparse set of observations is a very challenging task. Extensive exploration by Markov chain Monte Carlo (McMC) methods often results in considerable computational efforts. Most optimization methods, on the other hand, are limited to linear (continuous) model spaces and the minimization of an objective function, what often proves to be insufficient. To overcome these problems, we propose a new ensemble-based exploration scheme for geostatistical prior models generated by a multiple-point statistics (MPS) tool. The principle of our method is to expand an existing set of models by using posterior facies information for conditioning new MPS realizations. The algorithm is independent of the physical parametrization. It is tested on a simple synthetic inverse problem. When compared to two existing McMC methods (iterative spatial resampling (ISR) and Interrupted Markov chain Monte Carlo (IMcMC)), the required number of forward model runs was divided by a factor of 8–12.
      PubDate: 2017-04-08T03:01:22.942827-05:
      DOI: 10.1002/2016WR019550
       
  • Impact of eliminating fracture intersection nodes in multiphase
           compositional flow simulation
    • Authors: Kenneth M. Walton; Andre J. A. Unger, Marios A. Ioannidis, Beth L. Parker
      Pages: 2917 - 2939
      Abstract: Algebraic elimination of nodes at discrete fracture intersections via the star-delta technique has proven to be a valuable tool for making multiphase numerical simulations more tractable and efficient. This study examines the assumptions of the star-delta technique and exposes its effects in a 3-D, multiphase context for advective and dispersive/diffusive fluxes. Key issues of relative permeability-saturation-capillary pressure (kr-S-Pc) and capillary barriers at fracture-fracture intersections are discussed. This study uses a multiphase compositional, finite difference numerical model in discrete fracture network (DFN) and discrete fracture-matrix (DFM) modes. It verifies that the numerical model replicates analytical solutions and performs adequately in convergence exercises (conservative and decaying tracer, one and two-phase flow, DFM and DFN domains). The study culminates in simulations of a two-phase laboratory experiment in which a fluid invades a simple fracture intersection. The experiment and simulations evoke different invading fluid flow paths by varying fracture apertures as oil invades water-filled fractures and as water invades air-filled fractures. Results indicate that the node elimination technique as implemented in numerical model correctly reproduces the long-term flow path of the invading fluid, but that short-term temporal effects of the capillary traps and barriers arising from the intersection node are lost.
      PubDate: 2017-04-08T02:56:32.062639-05:
      DOI: 10.1002/2016WR020088
       
  • Biofuel as an Integrated Farm Drainage Management crop: A bioeconomic
           analysis
    • Authors: L. R. Levers; K. A. Schwabe
      Pages: 2940 - 2955
      Abstract: Irrigated agricultural lands in arid regions often suffer from soil salinization and lack of drainage, which affect environmental quality and productivity. Integrated Farm Drainage Management (IFDM) systems, where drainage water generated from higher-valued crops grown on high quality soils are used to irrigate salt-tolerant crops grown on marginal soils, is one possible strategy for managing salinity and drainage problems. If the IFDM crop were a biofuel crop, both environmental and private benefits may be generated; however, little is known about this possibility. As such, we develop a bioeconomic programming model of irrigated agricultural production to examine the role salt-tolerant biofuel crops might play within an IFDM system. Our results, generated by optimizing profits over land, water, and crop choice decisions subject to resource constraints, suggest that based on the private profits alone, biofuel crops can be a competitive alternative to the common practices of land retirement and nonbiofuel crop production under both low to high drainage water salinity. Yet IFDM biofuel crop production generates 30–35% fewer GHG emissions than the other strategies. The private market competitiveness coupled with the public good benefits may justify policy changes encouraging the growth of IFDM biofuel crops in arid agricultural areas globally.
      PubDate: 2017-04-10T05:58:13.330066-05:
      DOI: 10.1002/2016WR019773
       
  • Representative point-integrated suspended sediment sampling in rivers
    • Authors: A. B. Gitto; J. G. Venditti, R. Kostaschuk, M. Church
      Pages: 2956 - 2971
      Abstract: The vast majority of continental sediment delivered to the world's oceans moves by suspension in rivers. Depth-integrated or point-integrated bottle samplings are the traditional methods used to determine the mean concentration of suspended sediment in rivers. While there has been some investigation of the error associated with depth-integrated sampling, the representativeness of a point-integrated bottle sample has not been addressed in the literature. Here we analyze continuous hour-long measurements of suspended sediment and grain-size fractions collected using a LISST-SL in the sand-bed portion of the Fraser River, British Columbia, to determine an appropriate sampling time. The 2σ uncertainty range of individual 30 s samples varied from ±3% to ±33% about the observed mean, with a systematic increase toward the streambed. Mean concentrations for suspended sediment and grain-size fractions were computed over increasing time periods and compared with a long-duration mean concentration to determine when a sample becomes representative. A cumulative probability distribution was generated from multiple iterations of this process. All suspended sediment load and grain-size fractions bear a low probability of representing the mean concentration over standard bottle sample durations. A probability >90% of representing the mean concentration and grain size of various fractions requires ∼570 s (9.5 min) of sampling. Sampling for a shorter period of 264 s (4.4 min) can yield a sample with 73% probability of representing the mean concentration.
      PubDate: 2017-04-10T05:58:21.563004-05:
      DOI: 10.1002/2016WR019187
       
  • Hyphenated hydrology: Interdisciplinary evolution of water resource
           science
    • Authors: Kathryn L. McCurley; James W. Jawitz
      Pages: 2972 - 2982
      Abstract: Hydrology has advanced considerably as a scientific discipline since its recognized inception in the mid-twentieth century. Modern water resource related questions have forced adaptation from exclusively physical or engineering science viewpoints toward a deliberate interdisciplinary context. Over the past few decades, many of the eventual manifestations of this evolution were foreseen by prominent expert hydrologists. However, their narrative descriptions have lacked substantial quantification. This study addressed that gap by measuring the prevalence of and analyzing the relationships between the terms most frequently used by hydrologists to define and describe their research. We analyzed 16,591 journal article titles from 1965–2015 in Water Resources Research, through which the scientific dialogue and its time-sensitive progression emerged. Our word frequency and term cooccurrence network results revealed the dynamic timing of the lateral movement of hydrology across multiple disciplines as well as the deepening of scientific discourse with respect to traditional hydrologic questions. The conversation among water resource scientists surrounding the hydrologic subdisciplines of catchment-hydrology, hydro-meteorology, socio-hydrology, hydro-climatology, and eco-hydrology gained statistically significant momentum in the analyzed time period, while that of hydro-geology and contaminant-hydrology experienced periods of increase followed by significant decline. This study concludes that formerly exotic disciplines can potentially modify hydrology, prompting new insights and inspiring unconventional perspectives on old questions that may have otherwise become obsolete.
      PubDate: 2017-04-10T05:58:23.574701-05:
      DOI: 10.1002/2016WR019835
       
  • Vertical groundwater storage properties and changes in confinement
           determined using hydraulic head response to atmospheric tides
    • Authors: R. Ian Acworth; Gabriel C. Rau, Landon J. S. Halloran, Wendy A. Timms
      Pages: 2983 - 2997
      Abstract: Accurate determination of groundwater state of confinement and compressible storage properties at vertical resolution over depth is notoriously difficult. We use the hydraulic head response to atmospheric tides at 2 cpd frequency as a tracer to quantify barometric efficiency (BE) and specific storage (Ss) over depth. Records of synthesized Earth tides, atmospheric pressure, and hydraulic heads measured in nine piezometers completed at depths between 5 and 55 m into unconsolidated smectitic clay and silt, sand and gravel were examined in the frequency domain. The barometric efficiency increased over depth from ∼0.05 in silty clay to ∼0.15 in sands and gravels. BE for silty clay was confirmed by calculating the loading efficiency as 0.95 using rainfall at the surface. Specific storage was calculated using effective rather than total moisture. The differences in phase between atmospheric pressure and hydraulic heads at 2 cpd were ∼180° below 10 m indicating confined conditions despite the low BE. Heads in the sediment above a fine sand and silt layer at 12 m exhibited a time variable phase difference between 0° and 180° indicating varying confinement. Our results illustrate that the atmospheric tide at 2 cpd is a powerful natural tracer for quantifying groundwater state of confinement and compressible storage properties in layered formations from hydraulic heads and atmospheric pressure records without the need for externally induced hydraulic stress. This approach could significantly improve the development of conceptual hydrogeological model used for groundwater resource development and management.
      PubDate: 2017-04-10T05:58:28.907248-05:
      DOI: 10.1002/2016WR020311
       
  • Theoretical analysis of non-Gaussian heterogeneity effects on subsurface
           flow and transport
    • Authors: Monica Riva; Alberto Guadagnini, Shlomo P. Neuman
      Pages: 2998 - 3012
      Abstract: Much of the stochastic groundwater literature is devoted to the analysis of flow and transport in Gaussian or multi-Gaussian log hydraulic conductivity (or transmissivity) fields, Y(x)=ln⁡K(x) (x being a position vector), characterized by one or (less frequently) a multiplicity of spatial correlation scales. Yet Y and many other variables and their (spatial or temporal) increments, ΔY, are known to be generally non-Gaussian. One common manifestation of non-Gaussianity is that whereas frequency distributions of Y often exhibit mild peaks and light tails, those of increments ΔY are generally symmetric with peaks that grow sharper, and tails that become heavier, as separation scale or lag between pairs of Y values decreases. A statistical model that captures these disparate, scale-dependent distributions of Y and ΔY in a unified and consistent manner has been recently proposed by us. This new “generalized sub-Gaussian (GSG)” model has the form Y(x)=U(x)G(x) where G(x) is (generally, but not necessarily) a multiscale Gaussian random field and U(x) is a nonnegative subordinator independent of G. The purpose of this paper is to explore analytically, in an elementary manner, lead-order effects that non-Gaussian heterogeneity described by the GSG model have on the stochastic description of flow and transport. Recognizing that perturbation expansion of hydraulic conductivity K=eY diverges when Y is sub-Gaussian, we render the expansion convergent by truncating Y's domain of definition. We then demonstrate theoretically and illustrate by way of numerical examples that, as the domain of truncation expands, (a) the variance of truncated Y (denoted by Yt) approaches that of Y and (b) the pdf (and thereby moments) of Yt increments approach those of Y increments and, as a consequence, the variogram of Yt approaches that of Y. This in turn guarantees that perturbing Kt=eYt to second order in σYt (the standard deviation of Yt) yields results which approach those we obtain upon perturbing K=eY to second order in σY even as the corresponding series diverges. Our analysis is rendered mathematically tractable by considering mean-uniform steady state flow in an unbounded, two-dimensional domain of mildly heterogeneous Y with a single-scale function G having an isotropic exponential covariance. Results consist of expressions for (a) lead-order autocovariance and cross-covariance functions of hydraulic head, velocity, and advective particle displacement and (b) analogues of preasymptotic as well as asymptotic Fickian dispersion coefficients. We compare these theoretically and graphically with corresponding expressions developed in the literature for Gaussian Y. We find the former to differ from the latter by a factor k = 〈U2〉/〈U〉2 ( 〈〉 denoting ensemble expectation) and the GSG covariance of longitudinal velocity to contain an additional nugget term depending on this same factor. In the limit as Y becomes Gaussian, k reduces to one and the nugget term drops out.
      PubDate: 2017-04-11T02:41:14.246037-05:
      DOI: 10.1002/2016WR019353
       
  • Validation of SMAP soil moisture for the SMAPVEX15 field campaign using a
           hyper-resolution model
    • Authors: Xitian Cai; Ming Pan, Nathaniel W. Chaney, Andreas Colliander, Sidharth Misra, Michael H. Cosh, Wade T. Crow, Thomas J. Jackson, Eric F. Wood
      Pages: 3013 - 3028
      Abstract: Accurate global mapping of soil moisture is the goal of the Soil Moisture Active Passive (SMAP) mission, which is expected to improve the estimation of water, energy, and carbon exchanges between the land and the atmosphere. Like other satellite products, the SMAP soil moisture retrievals need to be validated, with the validation relying heavily on in situ measurements. However, a one-to-one comparison is ill advised due to the spatial mismatch of the large SMAP footprint (∼40 km) and the point scale in situ measurements. This study uses a recently developed hyper-resolution land surface model—HydroBlocks—as a tool to upscale in situ soil moisture measurements for the SMAPVEX15 (SMAP Validation Experiment 2015) field campaign during 2–18 August 2015. Calibrated against in situ observation, HydroBlocks shows a satisfactory Kling-Gupta efficiency (KGE) of 0.817 and RMSE of 0.019 m3/m3 for the calibration period. These results indicate that HydroBlocks can be used to upscale in situ measurements for this site. Different from previous studies, here in situ measurements are upscaled using a land surface model without bias correction. The upscaled soil moisture is then used to evaluate SMAP (passive) soil moisture products. The comparison of the upscaled network to SMAP shows that the retrievals are generally able to capture the areal-averaged soil moisture temporal variations. However, SMAP appears to be oversensitive to summer precipitation. We expect these findings can be used to improve the SMAP soil moisture product and thus facilitate its usage in studying the water, energy, and carbon cycles.
      PubDate: 2017-04-13T10:14:12.190982-05:
      DOI: 10.1002/2016WR019967
       
  • A method for preferential selection of dates in the Schaake shuffle
           approach to constructing spatiotemporal forecast fields of temperature and
           precipitation
    • Authors: Michael Scheuerer; Thomas M. Hamill, Brett Whitin, Minxue He, Arthur Henkel
      Pages: 3029 - 3046
      Abstract: Hydrological forecasts strongly rely on predictions of precipitation amounts and temperature as meteorological forcings for hydrological models. Ensemble weather predictions provide a number of different scenarios that reflect the uncertainty about these meteorological inputs, but these are often biased and under-dispersive, and therefore require statistical postprocessing. In addition to correcting the marginal distributions of the two weather variables, postprocessing methods must reconstruct their spatial, temporal, and intervariable dependence in order to generate physically realistic forecast trajectories that can be used as forcings of hydrological streamflow forecast models. For many years, a sample reordering method referred to as “Schaake shuffle” has been used successfully to address this multivariate aspect of forecast distributions by using historical observation trajectories as multivariate “dependence templates.” This paper proposes a variant of the Schaake shuffle, in which the historical dates are selected such that the marginal distributions of the corresponding observation trajectories are similar to the forecast marginal distributions, thus making it more likely that spatial and temporal gradients are preserved during the reordering procedure. This new approach is demonstrated with temperature and precipitation forecasts over four river basins in California, and it is shown to improve upon the standard Schaake shuffle both with respect to verification metrics applied to the forcings, and verification metrics applied to the resulting streamflow predictions.
      PubDate: 2017-04-13T12:42:17.985939-05:
      DOI: 10.1002/2016WR020133
       
  • Multiscale temporal variability and regional patterns in 555 years of
           conterminous U.S. streamflow
    • Authors: Michelle Ho; Upmanu Lall, Xun Sun, Edward R. Cook
      Pages: 3047 - 3066
      Abstract: The development of paleoclimate streamflow reconstructions in the conterminous United States (CONUS) has provided water resource managers with improved insights into multidecadal and centennial scale variability that cannot be reliably detected using shorter instrumental records. Paleoclimate streamflow reconstructions have largely focused on individual catchments limiting the ability to quantify variability across the CONUS. The Living Blended Drought Atlas (LBDA), a spatially and temporally complete 555 year long paleoclimate record of summer drought across the CONUS, provides an opportunity to reconstruct and characterize streamflow variability at a continental scale. We explore the validity of the first paleoreconstructions of streamflow that span the CONUS informed by the LBDA targeting a set of U.S. Geological Survey streamflow sites. The reconstructions are skillful under cross validation across most of the country, but the variance explained is generally low. Spatial and temporal structures of streamflow variability are analyzed using hierarchical clustering, principal component analysis, and wavelet analyses. Nine spatially coherent clusters are identified. The reconstructions show signals of contemporary droughts such as the Dust Bowl (1930s) and 1950s droughts. Decadal-scale variability was detected in the late 1900s in the western U.S., however, similar modes of temporal variability were rarely present prior to the 1950s. The twentieth century featured longer wet spells and shorter dry spells compared with the preceding 450 years. Streamflows in the Pacific Northwest and Northeast are negatively correlated with the central U.S. suggesting the potential to mitigate some drought impacts by balancing economic activities and insurance pools across these regions during major droughts.
      PubDate: 2017-04-13T10:13:54.05353-05:0
      DOI: 10.1002/2016WR019632
       
  • Simulation of the cumulative hydrological response to green infrastructure
    • Authors: P. M. Avellaneda; A. J. Jefferson, J. M. Grieser, S. A. Bush
      Pages: 3087 - 3101
      Abstract: In this study, we evaluated the cumulative hydrologic performance of green infrastructure in a residential area of the city of Parma, Ohio, draining to a tributary of the Cuyahoga River. Green infrastructure included the following spatially distributed devices: 16 street-side bioretention cells, 7 rain gardens, and 37 rain barrels. Data consisted of rainfall and outfall flow records for a wide range of storm events, including pretreatment and treatment periods. The Stormwater Management Model was calibrated and validated to predict the hydrologic response of green infrastructure. The calibrated model was used to quantify annual water budget alterations and discharge frequency over a 6 year simulation period. For the study catchment, we observed a treatment effect with increases of 1.4% in evaporation, 7.6% in infiltration, and a 9.0% reduction in surface runoff. The hydrologic performance of green infrastructure was evaluated by comparing the flow duration curve for pretreatment and treatment outfall flow scenarios. The flow duration curve shifted downward for the green infrastructure scenario. Discharges with a 0.5, 1, 2, and 5 year return period were reduced by an average of 29%. Parameter and predictive uncertainties were inspected by implementing a Bayesian statistical approach.
      PubDate: 2017-04-15T09:45:35.08592-05:0
      DOI: 10.1002/2016WR019836
       
  • Space-time duality for the fractional advection-dispersion equation
    • Authors: James F. Kelly; Mark M. Meerschaert
      Pages: 3464 - 3475
      Abstract: The fractional advection-dispersion equation replaces the second spatial derivative in the usual advection-dispersion equation with a fractional derivative in the spatial variable. It was first applied to tracer tests in underground aquifers, and later to tracer tests in rivers. An alternative model replaces the first time derivative with a fractional derivative in time. Previous work has shown that both models provide a reasonable fit to breakthrough curves in rivers, which has led to a controversy regarding the physically appropriate fractional model. This paper shows that the relevant space-fractional model is mathematically equivalent to the corresponding time-fractional model, thus resolving the controversy.
      PubDate: 2017-04-06T04:29:48.366165-05:
      DOI: 10.1002/2016WR019668
       
  • A new process sensitivity index to identify important system processes
           under process model and parametric uncertainty
    • Authors: Heng Dai; Ming Ye, Anthony P. Walker, Xingyuan Chen
      Pages: 3476 - 3490
      Abstract: A hydrological model consists of multiple process level submodels, and each submodel represents a process key to the operation of the simulated system. Global sensitivity analysis methods have been widely used to identify important processes for system model development and improvement. The existing methods of global sensitivity analysis only consider parametric uncertainty, and are not capable of handling model uncertainty caused by multiple process models that arise from competing hypotheses about one or more processes. To address this problem, this study develops a new method to probe model output sensitivity to competing process models by integrating model averaging methods with variance-based global sensitivity analysis. A process sensitivity index is derived as a single summary measure of relative process importance, and the index includes variance in model outputs caused by uncertainty in both process models and their parameters. For demonstration, the new index is used to assign importance to the processes of recharge and geology in a synthetic study of groundwater reactive transport modeling. The recharge process is simulated by two models that convert precipitation to recharge, and the geology process is simulated by two models of hydraulic conductivity. Each process model has its own random parameters. The new process sensitivity index is mathematically general, and can be applied to a wide range of problems in hydrology and beyond.
      PubDate: 2017-04-13T10:34:41.587942-05:
      DOI: 10.1002/2016WR019715
       
 
 
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