| 1. |
- Addassi, Mouadh, et al.
(författare)
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Pore-scale modeling of vapor transport in partially saturated capillary tube with variable area using chemical potential
- 2016
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Ingår i: Water resources research. - : AGU Publications. - 0043-1397 .- 1944-7973. ; 52:9, s. 7023-7035
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Tidskriftsartikel (refereegranskat)abstract
- Here we illustrate the usefulness of using the chemical potential as the primary unknown by modeling isothermal vapor transport through a partially saturated cylindrically symmetric capillary tube of variable cross-sectional area using a single equation. There are no fitting parameters and the numerical solutions to the equation are compared with experimental results with excellent agreement. We demonstrate that isothermal vapor transport can be accurately modeled without modeling the details of the contact angle, microscale temperature fluctuations, or pressure fluctuations using a modification of the Fick-Jacobs equation. We thus conclude that for a single, axisymmetric pore, the enhancement factor depends upon relative humidity boundary conditions at the liquid bridge interfaces, distance between liquid bridges, and bridge lengths.
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| 2. |
- Addor, Nans, et al.
(författare)
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Robust changes and sources of uncertainty in the projected hydrological regimes of Swiss catchments
- 2014
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 50:10, s. 7541-7562
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Tidskriftsartikel (refereegranskat)abstract
- Projections of discharge are key for future water resources management. These projections are subject to uncertainties, which are difficult to handle in the decision process on adaptation strategies. Uncertainties arise from different sources such as the emission scenarios, the climate models and their postprocessing, the hydrological models, and the natural variability. Here we present a detailed and quantitative uncertainty assessment, based on recent climate scenarios for Switzerland (CH2011 data set) and covering catchments representative for midlatitude alpine areas. This study relies on a particularly wide range of discharge projections resulting from the factorial combination of 3 emission scenarios, 10–20 regional climate models, 2 postprocessing methods, and 3 hydrological models of different complexity. This enabled us to decompose the uncertainty in the ensemble of projections using analyses of variance (ANOVA). We applied the same modeling setup to six catchments to assess the influence of catchment characteristics on the projected streamflow, and focused on changes in the annual discharge cycle. The uncertainties captured by our setup originate mainly from the climate models and natural climate variability, but the choice of emission scenario plays a large role by the end of the 21st century. The contribution of the hydrological models to the projection uncertainty varied strongly with catchment elevation. The discharge changes were compared to the estimated natural decadal variability, which revealed that a climate change signal emerges even under the lowest emission scenario (RCP2.6) by the end of the century. Limiting emissions to RCP2.6 levels would nevertheless reduce the largest regime changes by the end of the century by approximately a factor of two, in comparison to impacts projected for the high emission scenario SRES A2. We finally show that robust regime changes emerge despite the projection uncertainty. These changes are significant and are consistent across a wide range of scenarios and catchments. We propose their identification as a way to aid decision making under uncertainty.
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| 3. |
- Ahmad, Muhammad Arslan, et al.
(författare)
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Estimating the Permeability of Naturally Structured Soil From Percolation Theory and Pore Space Characteristics Imaged by X-Ray
- 2018
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Ingår i: Water Resources Research. - 0043-1397 .- 1944-7973. ; 54, s. 9255-9263
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Tidskriftsartikel (refereegranskat)abstract
- The saturated hydraulic conductivity of soil, K-s, is a critical parameter in hydrological models that remains notoriously difficult to predict. In this study, we test the capability of a model based on percolation theory and critical path analysis to estimate K-s measured on 95 undisturbed soil cores collected from contrasting soil types. One parameter (the pore geometry factor) was derived by model fitting, while the remaining two parameters (the critical pore diameter, d(c), and the effective porosity) were derived from X-ray computed tomography measurements. The model gave a highly significant fit to the K-s measurements (p<0.0001) although only 47% of the variation was explained and the fitted pore geometry factor was approximately 1 to 2 orders of magnitude larger than various theoretical values obtained for idealized porous media and pore network models. Apart from assumptions in the model that might not hold in reality, this could also be attributed to experimental error induced by, for example, air entrapment and changes in the soil pore structure occurring during sample presaturation and the measurement of K-s. Variation in the critical pore diameter, d(c), was the dominant source of variation in K-s, which suggests that d(c) is a suitable length scale for predicting soil permeability. Thus, from the point of view of pedotransfer functions, it could be worthwhile to direct future research toward exploring the correlations of d(c) with basic soil properties and site attributes.
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| 4. |
- Alfonso, L., et al.
(författare)
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Probabilistic Flood Maps to support decision-making : Mapping the Value of Information
- 2016
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 52:2, s. 1026-1043
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Tidskriftsartikel (refereegranskat)abstract
- Floods are one of the most frequent and disruptive natural hazards that affect man. Annually, significant flood damage is documented worldwide. Flood mapping is a common preimpact flood hazard mitigation measure, for which advanced methods and tools (such as flood inundation models) are used to estimate potential flood extent maps that are used in spatial planning. However, these tools are affected, largely to an unknown degree, by both epistemic and aleatory uncertainty. Over the past few years, advances in uncertainty analysis with respect to flood inundation modeling show that it is appropriate to adopt Probabilistic Flood Maps (PFM) to account for uncertainty. However, the following question arises; how can probabilistic flood hazard information be incorporated into spatial planning? Thus, a consistent framework to incorporate PFMs into the decision-making is required. In this paper, a novel methodology based on Decision-Making under Uncertainty theories, in particular Value of Information (VOI) is proposed. Specifically, the methodology entails the use of a PFM to generate a VOI map, which highlights floodplain locations where additional information is valuable with respect to available floodplain management actions and their potential consequences. The methodology is illustrated with a simplified example and also applied to a real case study in the South of France, where a VOI map is analyzed on the basis of historical land use change decisions over a period of 26 years. Results show that uncertain flood hazard information encapsulated in PFMs can aid decision-making in floodplain planning.
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| 5. |
- Ameli, Ali A., et al.
(författare)
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Primary weathering rates, water transit times, and concentration-discharge relations : A theoretical analysis for the critical zone
- 2017
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Ingår i: Water resources research. - : AMER GEOPHYSICAL UNION. - 0043-1397 .- 1944-7973. ; 53:1, s. 942-960
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Tidskriftsartikel (refereegranskat)abstract
- The permeability architecture of the critical zone exerts a major influence on the hydrogeochemistry of the critical zone. Water flow path dynamics drive the spatiotemporal pattern of geochemical evolution and resulting streamflow concentration-discharge (C-Q) relation, but these flow paths are complex and difficult to map quantitatively. Here we couple a new integrated flow and particle tracking transport model with a general reversible Transition State Theory style dissolution rate law to explore theoretically how C-Q relations and concentration in the critical zone respond to decline in saturated hydraulic conductivity (K-s) with soil depth. We do this for a range of flow rates and mineral reaction kinetics. Our results show that for minerals with a high ratio of equilibrium concentration ( Ceq) to intrinsic weathering rate ( Rmax), vertical heterogeneity in K-s enhances the gradient of weathering-derived solute concentration in the critical zone and strengthens the inverse stream C-Q relation. As CeqRmax decreases, the spatial distribution of concentration in the critical zone becomes more uniform for a wide range of flow rates, and stream C-Q relation approaches chemostatic behavior, regardless of the degree of vertical heterogeneity in K-s. These findings suggest that the transport-controlled mechanisms in the hillslope can lead to chemostatic C-Q relations in the stream while the hillslope surface reaction-controlled mechanisms are associated with an inverse stream C-Q relation. In addition, as CeqRmax decreases, the concentration in the critical zone and stream become less dependent on groundwater age (or transit time).
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| 6. |
- Ameli, Ali A., et al.
(författare)
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Where and When to Collect Tracer Data to Diagnose Hillslope Permeability Architecture
- 2021
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Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 57:8
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Tidskriftsartikel (refereegranskat)abstract
- The permeability architecture has a major influence on hillslope flow path and hydrogeochemistry. To constrain this architecture and overcome equifinality in the diagnosis of hillslope flow paths within hydrologic transport models, different types of complementary data (e.g., tracer) have been recommended. However, there is still little information on the extent to which such complementary data can unravel the permeability architecture, and where and when to measure such data to most efficiently constrain models. Here, we couple a Richards-based flow and transport model with extensive long-term field measurements to compare the relative value of different types of hydrometric and tracer data in discriminating between contrasting permeability (or saturated hydraulic conductivity ()) architectures, in the absence of macropore flow. Our results show that compared to streamflow and water table observations, stream tracer data have a stronger evaluative potential to constrain hillslope vertical pattern in , in particular during seasons when flow is on average low (e.g., winter or summer). Tracer data from within the hillslope are even more helpful to discriminate between different vertical patterns in Ks than stream tracer data. This suggests a higher evaluative potential for hillslope tracer observations. This evaluative potential of hillslope data depends on where and when the data are collected, and increases with depth from the soil surface, with distance from the stream and during seasons when flow is low. The findings also emphasize the importance of incorporating hillslope permeability architecture in hydrologic transport models in order to reduce the uncertainty in the predictions of stream water quality.
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| 7. |
- Aminjafari, Saeid, 1988-, et al.
(författare)
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Distinctive Patterns of Water Level Change in Swedish Lakes Driven by Climate and Human Regulation
- 2024
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 60:3
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Tidskriftsartikel (refereegranskat)abstract
- Despite having approximately 100,000 lakes, Sweden has limited continuous gauged lake water level data. Although satellite radar altimetry (RA) has emerged as a popular alternative to measure water levels in inland water bodies, it has not yet been used to understand the large-scale changes in Swedish lakes. Here, we quantify the changes in water levels in 144 lakes using RA data and in situ gauged measurements to examine the effects of flow regulation and hydroclimatic variability. We use data from several RA missions, including ERS-2, ENVISAT, JASON-1,2,3, SARAL, and Sentinel-3A/B. We found that during 1995–2022, around 52% of the lakes exhibited an increasing trend and 43% a decreasing trend. Most lakes exhibiting an increasing trend were in the north of Sweden, while most lakes showing a decreasing trend were in the south. Regarding the potential effects of regulation, we found that unregulated lakes had smaller trends in water level and dynamic storage than regulated ones. While the seasonal patterns of water levels in the lakes in the north are similar in regulated and unregulated lakes, in the south, they differ substantially. This study highlights the need to continuously monitor lake water levels for adaptation strategies in the face of climate change and understand the downstream effects of water regulatory schemes.
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| 8. |
- Aminjafari, Saeid, et al.
(författare)
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Tracking Centimeter-Scale Water Level Changes in Swedish Lakes Using D-InSAR
- 2024
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 60:2
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Tidskriftsartikel (refereegranskat)abstract
- Lakes are valuable water resources that support aquatic and terrestrial ecosystems and supply fresh water for the agricultural, industrial, and urban sectors worldwide. Although water levels should be tracked to monitor these services, conventional gauging is unfeasible in most lakes. This study applies Differential Interferometric Synthetic Aperture Radar (D-InSAR) to estimate small water level changes, less than 2 cm, in Swedish lakes over 6-day intervals. We validated the method across the shores of 30 Swedish lakes with gauged observations in 2019. We used Sentinel-1A/B images with a 6-day temporal separation to construct consecutive interferograms and accumulated the phase changes in pixels of high coherence to build a time series of water levels. We find that the accumulated phase change obtained by D-InSAR replicates the magnitude of water levels in seven lakes in Southern Sweden, where water levels change slowly, less than 2 cm per 6-day period, as validated by in-situ gauges. In addition, this study demonstrates the application of D-InSAR to estimate the long-term direction of water level change (i.e., increase or decrease) in all 30 lakes. This work reveals the utility of high temporal resolution water level observations in support of other satellite water level instruments such as conventional altimeters and the recently launched Surface Water and Ocean Topography Mission.
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| 9. |
- Archfield, Stacey A., et al.
(författare)
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Accelerating advances in continental domain hydrologic modeling
- 2015
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 51:12, s. 10078-10091
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Tidskriftsartikel (refereegranskat)abstract
- In the past, hydrologic modeling of surface water resources has mainly focused on simulating the hydrologic cycle at local to regional catchment modeling domains. There now exists a level of maturity among the catchment, global water security, and land surface modeling communities such that these communities are converging toward continental domain hydrologic models. This commentary, written from a catchment hydrology community perspective, provides a review of progress in each community toward this achievement, identifies common challenges the communities face, and details immediate and specific areas in which these communities can mutually benefit one another from the convergence of their research perspectives. Those include: (1) creating new incentives and infrastructure to report and share model inputs, outputs, and parameters in data services and open access, machine-independent formats for model replication or reanalysis; (2) ensuring that hydrologic models have: sufficient complexity to represent the dominant physical processes and adequate representation of anthropogenic impacts on the terrestrial water cycle, a process-based approach to model parameter estimation, and appropriate parameterizations to represent large-scale fluxes and scaling behavior; (3) maintaining a balance between model complexity and data availability as well as uncertainties; and (4) quantifying and communicating significant advancements toward these modeling goals.
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| 10. |
- Bargues Tobella, Aida
(författare)
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Determinants of Soil Field-Saturated Hydraulic Conductivity Across Sub-Saharan Africa: Texture and Beyond
- 2024
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Ingår i: Water Resources Research. - 0043-1397 .- 1944-7973. ; 60
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Tidskriftsartikel (refereegranskat)abstract
- Soil infiltration is critical for water security and related ecosystem services. This infiltration, the ability of soils to absorb water at their surface, is controlled by the soil hydraulic conductivity. Despite recent efforts in assembling measurements of soil hydraulic conductivity, global databases and derived pedotransfer functions lack coverage in the tropics. Here, we present soil infiltration measurements and other indicators of soil and land health collected systematically in 3,573 plots from 83 100 km2 sites across 19 countries in sub-Saharan Africa. We use these data to (a) determine field-saturated hydraulic conductivity (Kfs) and (b) explore which variables best predict variation in Kfs. Our results show that sand content, soil organic carbon (SOC), and woody cover had a positive relationship with Kfs, whereas grazing intensity and soil pH had a negative relationship. Our findings highlight that, despite soil texture being important, structure also plays a critical role. These results indicate considerable potential to improve soil hydrological functioning through management and restoration practices that target soil structure. Enhancing SOC content, limiting animal stocking, promoting trees, shrubs, and other vegetation cover, and preventing soil erosion can increase Kfs and improve water security. This data set can contribute to improving Earth system and land surface models for applications in Africa.We present field infiltration measurements and accompanying indicators of soil and land health from 3,573 plots across sub-Saharan Africa Field-saturated hydraulic conductivity (Kfs) is associated with soil texture and factors related to soil structure Our results suggest that soil hydrological functioning can be enhanced through management practices that target soil structure
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| 11. |
- Bargues Tobella, Aida, et al.
(författare)
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The effect of trees on preferential flow and soil infiltrability in an agroforestry parkland in semiarid Burkina Faso
- 2014
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Ingår i: Water Resources Research. - 0043-1397 .- 1944-7973. ; 50, s. 3342-3354
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Tidskriftsartikel (refereegranskat)abstract
- Water scarcity constrains the livelihoods of millions of people in tropical drylands. Tree planting in these environments is generally discouraged due to the large water consumption by trees, but this view may neglect their potential positive impacts on water availability. The effect of trees on soil hydraulic properties linked to groundwater recharge is poorly understood. In this study, we performed 18 rainfall simulations and tracer experiments in an agroforestry parkland in Burkina Faso to investigate the effect of trees and associated termite mounds on soil infiltrability and preferential flow. The sampling points were distributed in transects each consisting of three positions: (i) under a single tree, (ii) in the middle of an open area, and (iii) under a tree associated with a termite mound. The degree of preferential flow was quantified through parameters based on the dye infiltration patterns, which were analyzed using image analysis of photographs. Our results show that the degree of preferential flow was highest under trees associated with termite mounds, intermediate under single trees, and minimal in the open areas. Tree density also had an influence on the degree of preferential flow, with small open areas having more preferential flow than large ones. Soil infiltrability was higher under single trees than in the open areas or under trees associated with a termite mound. The findings from this study demonstrate that trees have a positive impact on soil hydraulic properties influencing groundwater recharge, and thus such effects must be considered when evaluating the impact of trees on water resources in drylands.
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| 12. |
- Basirat, Farzad, et al.
(författare)
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Hydraulic Modeling of Induced and Propagated Fractures : Analysis of Flow and Pressure Data From Hydromechanical Experiments in the COSC-1 Deep Borehole in Crystalline Rock Near Åre, Sweden
- 2021
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Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 57:11
-
Tidskriftsartikel (refereegranskat)abstract
- To characterize the coupled hydromechanical behavior of rock fractures, the step-rate injection method for fracture in-situ properties (SIMFIP) was conducted with a specialized downhole probe developed by Guglielmi et al. (2014, https://doi.org/10.1007/s00603-013-0517-1). In June 2019, a field campaign was carried out near Åre, Sweden, where the SIMFIP probe was applied in the Collisional Orogeny in the Scandinavian Caledonides-1 scientific borehole to understand the dynamics of injection-induced fracture initiation, fracture opening, and shearing due to water injection-withdrawal in a borehole interval isolated by two packers. Three intervals were investigated at ∼500 m depth: (a) an unfractured section (intact rock), (b) a section with non-conductive fractures, and (c) a section with hydraulically conductive fractures. Pressure, injection flow rate, and borehole wall displacement were simultaneously measured during the tests. In the present study, the geometry of the induced fracture and deformation of existing fractures at different time stages of the tests are determined based on a hydrologic model by using the measured pressure and flow data during each time stage of the experiment. A numerical model for the fluid flow within the fracture and the packed-off borehole interval is implemented within COMSOL Multiphysics. By matching model simulations with observed data for all three sections, estimates of the induced and propagated fractures' radius and aperture at successive time stages have been obtained in each case. We could also determine the non-linear relationship between fracture aperture and pressure for values above fracture opening pressures. The model results provide insights for the understanding of pressure-induced fracture initiation and propagation in crystalline rock.
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| 13. |
- Bassiouni, Maoya, et al.
(författare)
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Source Relationships and Model Structures Determine Information Flow Paths in Ecohydrologic Models
- 2022
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Ingår i: Water Resources Research. - 0043-1397 .- 1944-7973. ; 58
-
Tidskriftsartikel (refereegranskat)abstract
- In a complex ecohydrologic system, vegetation and soil variables combine to dictate heat fluxes, and these fluxes may vary depending on the extent to which drivers are linearly or nonlinearly interrelated. From a modeling and causality perspective, uncertainty, sensitivity, and performance measures all relate to how information from different sources "flows" through a model to produce a target, or output. We address how model structure, broadly defined as a mapping from inputs to an output, combines with source dependencies to produce a range of information flow pathways from sources to a target. We apply information decomposition, which partitions reductions in uncertainty into synergistic, redundant, and unique information types, to a range of model cases. Toy models show that model structure and source dependencies both restrict the types of interactions that can arise between sources and targets. Regressions based on weather data illustrate how different model structures vary in their sensitivity to source dependencies, thus affecting predictive and functional performance. Finally, we compare the Surface Flux Equilibrium theory, a land-surface model, and neural networks in estimating the Bowen ratio and find that models trade off information types particularly when sources have the highest and lowest dependencies. Overall, this study extends an information theory-based model evaluation framework to incorporate the influence of source dependency on information pathways. This could be applied to explore behavioral ranges for both machine learning and process-based models, and guide model development by highlighting model deficiencies based on information flow pathways that would not be apparent based on existing measures.
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| 14. |
- Baxevani, Anastassia, 1969, et al.
(författare)
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A spatiotemporal precipitation generator based on a censored latent Gaussian field
- 2015
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Ingår i: Water Resources Research. - 0043-1397 .- 1944-7973. ; 51:6, s. 4338-4358
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Tidskriftsartikel (refereegranskat)abstract
- A daily stochastic spatiotemporal precipitation generator that yields precipitation realizations that are quantitatively consistent is described. The methodology relies on a latent Gaussian field that drives both the occurrence and intensity of the precipitation process. For the precipitation intensity, the marginal distributions, which are space and time dependent, are described by a composite model of a gamma distribution for observations below some threshold with a generalized Pareto distribution modeling the excesses above the threshold. Model parameters are estimated from data and extrapolated to locations and times with no direct observations using linear regression of position covariates. One advantage of such a model is that stochastic generator parameters are readily available at any location and time of the year inside the stationarity regions. The methodology is illustrated for a network of 12 locations in Sweden. Performance of the model is judged through its ability to accurately reproduce a series of spatial dependence measures and weather indices. © 2015. American Geophysical Union. All Rights Reserved.
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| 15. |
- Bayer-Raich, Martí, et al.
(författare)
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Breakthrough of attenuating contaminant plumes in pumping wells: Analytical model and implications for integral pumping tests.
- 2009
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 45, s. W02413-
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Tidskriftsartikel (refereegranskat)abstract
- Monitoring of contaminant plumes and predicting their future fate are essential for effective management of groundwater contaminants. Solute breakthrough curves from operating pumping wells can provide information on the water quality in relatively large aquifer regions, which may be unavailable to instrumentation and direct measurement for practical and/or economical reasons. Relations between spatially varying aquifer concentrations C0(x, y) initially surrounding a well and temporally varying concentrations of subsequently extracted well water, Cp(t), then need to be quantified. However, limited applicability of analytical expressions and numerical inaccuracies related to solving transport equations for converging flow fields hamper such quantifications even in homogeneous aquifers. We use a stream-tube approach and provide a general problem formulation that accounts for first-order degradation and linear, instantaneous, sorption/retardation in heterogeneous aquifers. An analytical expression is obtained for homogeneous aquifer conditions (in the well vicinity), relating any given initial C0(x, y) function and the subsequent contaminant breakthrough Cp(t) in the well. Results for wide plumes subject to first-order degradation show that concentrations at the extraction well will increase as a function of pumping time. This increase is despite the fact that late-time data reflect longer transport paths (to the well), along which mass is removed through degradation. We also derive unique solutions for the inverse problem, in particular considering how the average contaminant concentration Cav (averaged along a control plane through the well within its capture zone, perpendicular to the mean groundwater flow direction) depends on the measurable Cp(t). The solutions demonstrate that the longer the pumping time, the more sensitive the solutions for Cav become to degradation rate constants, which if needed can be determined in situ using multiple control planes.
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| 16. |
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| 17. |
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| 18. |
- Beven, Keith, et al.
(författare)
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Macropores and water flow in soils revisited
- 2013
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Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 49:6, s. 3071-3092
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Forskningsöversikt (refereegranskat)abstract
- The original review of macropores and water flow in soils by Beven and Germann is now 30 years old and has become one of the most highly cited papers in hydrology. This paper attempts to review the progress in observations and theoretical reasoning about preferential soil water flows over the intervening period. It is suggested that the topic has still not received the attention that its importance deserves, in part because of the ready availability of software packages rooted firmly in the Richards domain, albeit that there is convincing evidence that this may be predicated on the wrong experimental method for natural conditions. There is still not an adequate physical theory linking all types of flow, and there are still not adequate observational techniques to support the scale dependent parameterizations that will be required at practical field and hillslope scales of application. Some thoughts on future needs to develop a more comprehensive representation of soil water flows are offered.
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| 19. |
- Bin Ashraf, Faisal, et al.
(författare)
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A Method for Assessment of Sub-Daily Flow Alterations Using Wavelet Analysis for Regulated Rivers
- 2022
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Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 58:1
-
Tidskriftsartikel (refereegranskat)abstract
- New tools are needed to evaluate the impacts of short-term hydropower regulation practices on downstream river systems and to progress towards sustainable river-flow management. As hydropower is increasingly being used to balance the energy load deficit caused by other less flexible sources, sub-daily flow conditions across many regulated river (RR) systems are changing. To address this, we used wavelet analyses to quantify the discharge variability in RRs and categorized the level of variability based on the conditions in natural free-flowing rivers. The presented framework used the definition of fluvial connectivity (Grill et al., 2019) to identify free-flowing rivers used in the study. We tested the developed framework in 12 different RRs in Finland and found higher overall averaged sub-daily variations, with up to 20 times larger variability than natural conditions. A large, highly regulated Finnish river system was found to have the highest sub-daily variations in winter, while smaller RRs with lower levels of regulation the highest variations in summer. The proposed framework offers a novel tool for sustainable river management and can be easily applied to various rivers and regions globally. It had flexibility to analyze sub-daily variations in desired seasonal or other ecologically sensitive periods.
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| 20. |
- Blazkova, Sarka, et al.
(författare)
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A limits of acceptability approach to model evaluation and uncertainty estimation in flood frequency estimation by continuous simulation : Skalka catchment, Czech Republic
- 2009
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 45, s. W00B16-
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Tidskriftsartikel (refereegranskat)abstract
- In this study continuous simulation flood frequency predictions on the Skalka catchment in the Czech Republic (672 km 2, range of altitudes from 460 to 1041 m above sea level), are compared against summary information of rainfall characteristics, the flow duration curve, and the frequency characteristics of flood discharges and snow water equivalent using the generalized likelihood uncertainty estimation limits of acceptability approach outlined by Beven (2006). Limits of acceptability have been defined, prior to running the Monte Carlo model realizations for subcatchment rainfalls, discharges (using rating data) at 5 sites within the catchment, and snow water equivalent in 13 snow zones, 4 of which have observed data. Flood frequency and flow duration data at the outlet of the whole catchment are not used in the evaluation but are used to test the predictions. In order to get sufficient behavioral models to assess adequately the prediction uncertainty it was necessary to refine the model structure, sample the model space more densely, and, in the end, relax the limits of acceptability to allow for a strong realization effect in predicted flood frequencies. We use a procedure of scoring deviations relative to the limits of acceptability to identify the minimum extension of the limits across all criteria to obtain a sample of 4192 parameter sets that were accepted as potentially useful in prediction. Results show that individual model realizations, with the same parameter values, of similar length to the observations can vary significantly in acceptability. Long-term simulations of 10,000 years for retained models were used to obtain uncertain estimates of the 1000 year peak and associated flood hydrographs required for the assessment of dam safety at the catchment outlet.
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| 21. |
- Bottacin-Busolin, Andrea, 1980-, et al.
(författare)
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Combined role of advective pumping and mechanical dispersion on time scales of bed form-induced hyporheic exchange
- 2010
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Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 46, s. W08518-
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Tidskriftsartikel (refereegranskat)abstract
- This study analyzes the effect of advective pumping and pore scale dispersion on bed form-induced hyporheic exchange. Advection and dispersion play a competitive role in the exchange dynamics between the porous medium and the overlying stream: Advective fluxes first lead solutes deep into the bed and then back to the stream water, whereas dispersive fluxes favor the transfer of solutes deep into the bed leading to a permanent mass retention. The combined effect of advective exchange and dispersive fluxes produces complexity in the shape of the tails of the residence time distributions (RTDs), which follow at various stages of the process either a power law or an exponential decay. The seepage velocity induced by the stream gradient and, in case of a moving bed, the celerity of the translating bed forms limit the thickness of the advective hyporheic zone, inducing the RTDs to decrease rapidly at late time. This rapid decay can be preceded by a temporal region where the probability density functions (pdf's) tend to be inversely proportional to the square of time, and is followed by a region dominated by dispersion where the pdf's tend to be inversely proportional to the 3/2 power of time. The process shows distinct temporal ranges identified here by appropriate dimensionless parameters. Because of this complex exchange dynamics, models considering pure advection in the porous medium can significantly underestimate solute transfer at long time scales, whereas purely diffusive models of hyporheic exchange appear inadequate to represent the physical processes at an intermediate stage.
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| 22. |
- Bottacin-Busolin, Andrea, 1980-, et al.
(författare)
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Probabilistic description of grain resistance from simultaneous flow field and grain motion measurements
- 2008
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Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 44:9, s. W09419-
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Tidskriftsartikel (refereegranskat)abstract
- Experiments were carried out using a mobile gravel bed placed in a tilting flume with a modified particle image velocimetry (PIV) system. Individual grain movements were surveyed using data from time series of images. Near-bed velocity flow field measurements were made simultaneously above the same area of the sediment surface by applying cross-correlation techniques to the collected plan view images. Statistics of grain motions were collected through a semiautomatic procedure. Significant changes in the flow field were observed in the proximity of the entrained or deposited particles. A strong correlation is shown between the changes in the local streamwise and lateral velocity and the movement of the grains. The theory of Grass is revisited and developed based on the experimental results. The probability distribution of individual grain resistance has been derived from the statistics of the near-bed velocity field and of the entrainment risk.
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| 23. |
- Broxton, P, et al.
(författare)
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On the role of aspect to quantify water transit times in small mountainous catchments
- 2009
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 45, s. W08427-W08427
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Tidskriftsartikel (refereegranskat)abstract
- In the current empirical study, we provide evidence about how the hydrologic responses of small mountain catchments are related to aspect (slope direction; exposure) at Redondo Peak, located in the Valles Caldera, New Mexico, USA. Specifically, we test the hypothesis that the transit time of water is related to the catchment aspect. Aspect is an easily measurable and transferable topographic characteristic that is related to the amount of direct solar radiation a particular catchment receives, and therefore, different catchments with different aspects have different rates of snow ablation, evapotranspiration, and water cycling in general. Transit times, which describe the time between when water enters the catchment as precipitation and when it leaves as stream flow, captures many hydrologic features such as flowpath variability and the combined effects of water storage and water fluxes. We have designed an experiment that involves field data collection, isotopic analysis of stream and precipitation samples, and the estimation of transit times using lumped-parameter convolution for 15 sites in small (1-15 km2) catchments that drain different aspects of Redondo Peak. Our data suggests that isotopic variability and estimated transit times are both related to aspect. Other potential relationships between topographical features (such as flowpath length, slope gradient, and elevation) and isotopic measurements of streamwater suggest that landscape and hydrological features are interconnected at Redondo Peak, but these links are not conclusive, suggesting that these topographic indicators do not fully explain the variability of water cycling in these small mountain catchments.
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| 24. |
- Brunner, Manuela I., et al.
(författare)
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Flood type specific construction of synthetic design hydrographs
- 2017
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Ingår i: Water resources research. - : AMER GEOPHYSICAL UNION. - 0043-1397 .- 1944-7973. ; 53:2, s. 1390-1406
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Tidskriftsartikel (refereegranskat)abstract
- Accurate estimates of flood peaks, corresponding volumes, and hydrographs are required to design safe and cost-effective hydraulic structures. In this paper, we propose a statistical approach for the estimation of the design variables peak and volume by constructing synthetic design hydrographs for different flood types such as flash-floods, short-rain floods, long-rain floods, and rain-on-snow floods. Our approach relies on the fitting of probability density functions to observed flood hydrographs of a certain flood type and accounts for the dependence between peak discharge and flood volume. It makes use of the statistical information contained in the data and retains the process information of the flood type. The method was tested based on data from 39 mesoscale catchments in Switzerland and provides catchment specific and flood type specific synthetic design hydrographs for all of these catchments. We demonstrate that flood type specific synthetic design hydrographs are meaningful in flood-risk management when combined with knowledge on the seasonality and the frequency of different flood types.
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| 25. |
- Brunner, Manuela I., et al.
(författare)
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Identification of Flood Reactivity Regions via the Functional Clustering of Hydrographs
- 2018
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 54:3, s. 1852-1867
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Tidskriftsartikel (refereegranskat)abstract
- Flood hydrograph shapes contain valuable information on the flood-generation mechanisms of a catchment. To make good use of this information, we express flood hydrograph shapes as continuous functions using a functional data approach. We propose a clustering approach based on functional data for flood hydrograph shapes to identify a set of representative hydrograph shapes on a catchment scale and use these catchment-specific sets of representative hydrographs to establish regions of catchments with similar flood reactivity on a regional scale. We applied this approach to flood samples of 163 medium-size Swiss catchments. The results indicate that three representative hydrograph shapes sufficiently describe the hydrograph shape variability within a catchment and therefore can be used as a proxy for the flood behavior of a catchment. These catchment-specific sets of three hydrographs were used to group the catchments into three reactivity regions of similar flood behavior. These regions were not only characterized by similar hydrograph shapes and reactivity but also by event magnitudes and triggering event conditions. We envision these regions to be useful in regionalization studies, regional flood frequency analyses, and to allow for the construction of synthetic design hydrographs in ungauged catchments. The clustering approach based on functional data which establish these regions is very flexible and has the potential to be extended to other geographical regions or toward the use in climate impact studies.
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