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  • 1.
    Addassi, Mouadh
    et al.
    Technical University of Denmark, Denmark.
    Schreyer, Lynn
    Washington State University, USA.
    Johannesson, Björn
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Lin, Hai
    University of Colorado Denver, USA.
    Pore-scale modeling of vapor transport in partially saturated capillary tube with variable area using chemical potential2016Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 52, nr 9, s. 7023-7035Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 2. Addor, Nans
    et al.
    Rössler, Ole
    Köplin, Nina
    Huss, Matthias
    Weingartner, Rolf
    Seibert, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Robust changes and sources of uncertainty in the projected hydrological regimes of Swiss catchments2014Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 50, nr 10, s. 7541-7562Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 3.
    Alfonso, L.
    et al.
    UNESCO IHE Inst Water Educ, Integrated Water Syst & Governance, Delft, Netherlands..
    Mukolwe, M. M.
    UNESCO IHE Inst Water Educ, Integrated Water Syst & Governance, Delft, Netherlands.;Masinde Muliro Univ Sci & Technol, Estates Dept, Kakamega, Kenya..
    Di Baldassarre, Giuliano
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Probabilistic Flood Maps to support decision-making: Mapping the Value of Information2016Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 52, nr 2, s. 1026-1043Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 4. Ameli, Ali A.
    et al.
    Beven, Keith
    Erlandsson, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Creed, Irena F.
    McDonnell, Jeffrey J.
    Bishop, Kevin
    Primary weathering rates, water transit times, and concentration-discharge relations: A theoretical analysis for the critical zone2017Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 53, nr 1, s. 942-960Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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 <mml:mfrac>CeqRmax</mml:mfrac> 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 <mml:mfrac>CeqRmax</mml:mfrac> decreases, the concentration in the critical zone and stream become less dependent on groundwater age (or transit time).

  • 5.
    Ameli, Ali A.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära. Univ Saskatchewan, Global Inst Water Secur, Saskatoon, SK, Canada.;Western Univ, Dept Biol, London, ON, Canada.
    Beven, Keith
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära. Univ Lancaster, Lancaster Environm Ctr, Lancaster, England..
    Erlandsson, Martin
    Stockholm Univ, Dept Phys Geog, Stockholm, Sweden..
    Creed, Irena F.
    Western Univ, Dept Biol, London, ON, Canada..
    McDonnell, Jeffrey J.
    Univ Saskatchewan, Global Inst Water Secur, Saskatoon, SK, Canada.;Univ Aberdeen, Sch Geosci, Aberdeen, Scotland.;Oregon State Univ, Dept Forest Engn Resources & Management, Corvallis, OR 97331 USA..
    Bishop, Kevin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära. Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Uppsala, Sweden..
    Primary weathering rates, water transit times, and concentration-discharge relations: A theoretical analysis for the critical zone2017Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 53, nr 1, s. 942-960Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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 <mml:mfrac>CeqRmax</mml:mfrac> 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 <mml:mfrac>CeqRmax</mml:mfrac> decreases, the concentration in the critical zone and stream become less dependent on groundwater age (or transit time).

  • 6. Archfield, Stacey A.
    et al.
    Clark, Martyn
    Arheimer, Berit
    Hay, Lauren E.
    McMillan, Hilary
    Kiang, Julie E.
    Seibert, J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Hakala, Kirsti
    Bock, Andrew
    Wagener, Thorsten
    Farmer, William H.
    Andreassian, Vazken
    Attinger, Sabine
    Viglione, Alberto
    Knight, Rodney
    Markstrom, Steven
    Over, Thomas
    Accelerating advances in continental domain hydrologic modeling2015Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 51, nr 12, s. 10078-10091Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 7. Archfield, Stacey A.
    et al.
    Clark, Martyn
    Arheimer, Berit
    SMHI, Forskningsavdelningen, Hydrologi.
    Hay, Lauren E.
    McMillan, Hilary
    Kiang, Julie E.
    Seibert, Jan
    Hakala, Kirsti
    Bock, Andrew
    Wagener, Thorsten
    Farmer, William H.
    Andreassian, Vazken
    Attinger, Sabine
    Viglione, Alberto
    Knight, Rodney
    Markstrom, Steven
    Over, Thomas
    Accelerating advances in continental domain hydrologic modeling2015Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 51, nr 12, s. 10078-10091Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 8. Bayer-Raich, Martí
    et al.
    Jarsjö, Jerker
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Teutsch, Georg
    Breakthrough of attenuating contaminant plumes in pumping wells: Analytical model and implications for integral pumping tests.2009Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 45, s. W02413-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 9.
    Beven, Keith
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Cloke, Hannah L.
    Department of Geography, King's College London, London, UK.
    Comment on ‘‘Hyperresolution global land surface modeling: Meeting a grand challenge for monitoring Earth’s terrestrial water’’ by Eric F. Wood et al.2012Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 48, s. W01801-Artikkel i tidsskrift (Fagfellevurdert)
  • 10.
    Beven, Keith
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Germann, Peter
    Macropores and water flow in soils revisited2013Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 49, nr 6, s. 3071-3092Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    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.

  • 11.
    Beven, Keith
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Smith, Paul
    Lancaster Environment Centre, University of Lancaster, Lancaster, UK.
    Westerberg, Ida
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Freer, Jim
    School of Geographical Sciences, University of Bristol, Bristol, UK.
    Comment on "Pursuing the method of multiple working hypotheses for hydrological modeling" by M. P. Clark et al.2012Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 48, s. W11801-Artikkel i tidsskrift (Fagfellevurdert)
  • 12. Blazkova, Sarka
    et al.
    Beven, Keith
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    A limits of acceptability approach to model evaluation and uncertainty estimation in flood frequency estimation by continuous simulation: Skalka catchment, Czech Republic2009Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 45, s. W00B16-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 13.
    Bosshard, Thomas
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Carambia, M.
    Goergen, K.
    Kotlarski, S.
    Krahe, P.
    Zappa, M.
    Schaer, C.
    Quantifying uncertainty sources in an ensemble of hydrological climate-impact projections2013Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 49, nr 3, s. 1523-1536Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The quantification of uncertainties in projections of climate impacts on river streamflow is highly important for climate adaptation purposes. In this study, we present a methodology to separate uncertainties arising from the climate model (CM), the statistical postprocessing (PP) scheme, and the hydrological model (HM). We analyzed ensemble projections of hydrological changes in the Alpine Rhine (Eastern Switzerland) for the near-term and far-term scenario periods 2024-2050 and 2073-2099 with respect to 1964-1990. For the latter scenario period, the model ensemble projects a decrease of daily mean runoff in summer (-32.2%, range [-45.5% to -8.1%]) and an increase in winter (+41.8%, range [+4.8% to +81.7%]). We applied an analysis of variance model combined with a subsampling procedure to assess the importance of different uncertainty sources. The CMs generally are the dominant source in summer and autumn, whereas, in winter and spring, the uncertainties due to the HMs and the statistical PP gain importance and even partly dominate. In addition, results show that the individual uncertainties from the three components are not additive. Rather, the associated interactions among the CM, the statistical PP scheme, and the HM account for about 5%-40% of the total ensemble uncertainty. The results indicate, in distinction to some previous studies, that none of the investigated uncertainty sources are negligible, and some of the uncertainty is not attributable to individual modeling chain components but rather depends upon interactions. Citation: Bosshard, T., M. Carambia, K. Goergen, S. Kotlarski, P. Krahe, M. Zappa, and C. Schar (2013), Quantifying uncertainty sources in an ensemble of hydrological climate-impact projections, Water Resour. Res., 49, 1523-1536, doi: 10.1029/2011WR011533.

  • 14.
    Bottacin-Busolin, Andrea
    et al.
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Marion, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Combined role of advective pumping and mechanical dispersion on time scales of bed form-induced hyporheic exchange2010Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 46, s. W08518-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 15.
    Bottacin-Busolin, Andrea
    et al.
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Tait, Simon
    Univ Bradford, Sch Engn Design & Technol.
    Marion, Andrea
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Chegini, Amir
    Univ Guilan, Dept Civil Engn, Fac Engn.
    Tregnaghi, Matteo
    Univ Padua, Dept Hydraul Maritime Environm & Geotech Engn.
    Probabilistic description of grain resistance from simultaneous flow field and grain motion measurements2008Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 44, nr 9, s. W09419-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 16. Broxton, P
    et al.
    Troch, P
    Lyon, S
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    On the role of aspect to quantify water transit times in small mountainous catchments2009Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 45, s. W08427-W08427Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 17.
    Brunner, Manuela I.
    et al.
    Univ Zurich, Dept Geog, Zurich, Switzerland;Univ Grenoble Alpes, CNRS, IRD, Grenoble INP,IGE, Grenoble, France.
    Viviroli, Daniel
    Univ Zurich, Dept Geog, Zurich, Switzerland;Belop Gmbh, Sarnen, Switzerland.
    Furrer, Reinhard
    Univ Zurich, Dept Math, Zurich, Switzerland;Univ Zurich, Dept Computat Sci, Zurich, Switzerland.
    Seibert, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära. Univ Zurich, Dept Geog, Zurich, Switzerland.
    Favre, Anne-Catherine
    Univ Grenoble Alpes, CNRS, IRD, Grenoble INP,IGE, Grenoble, France.
    Identification of Flood Reactivity Regions via the Functional Clustering of Hydrographs2018Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 54, nr 3, s. 1852-1867Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 18.
    Brunner, Manuela I.
    et al.
    Univ Zurich, Dept Geog, Zurich, Switzerland.;Univ Grenoble Alpes, Grenoble INP, Grenoble, France..
    Viviroli, Daniel
    Univ Zurich, Dept Geog, Zurich, Switzerland.;Belop GmbH, Sarnen, Switzerland..
    Sikorska, Anna E.
    Univ Zurich, Dept Geog, Zurich, Switzerland.;Warsaw Univ Life Sci, Dept Hydraul Engn, Warsaw, Poland..
    Vannier, Olivier
    Compagnie Natl Rhone, Lyon, France..
    Favre, Anne-Catherine
    Univ Grenoble Alpes, Grenoble INP, Grenoble, France..
    Seibert, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära. Univ Zurich, Dept Geog, Zurich, Switzerland..
    Flood type specific construction of synthetic design hydrographs2017Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 53, nr 2, s. 1390-1406Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 19. Buytaert, Wouter
    et al.
    Beven, Keith
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Regionalization as a learning process2009Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 45, s. W11419-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper deals with the uncertainty involved in geographical migration of hydrological model structures, commonly known as regionalization. Regionalization relies on the hypothesis that calibrated parameter sets from a donor catchment can be useful to predict discharge of an ungauged catchment. However, since every catchment is unique, model parameters need to be adapted for differences between a calibration and a prediction catchment, either by transformation or further selection. This process is inherently uncertain. Model parameters, and therefore the required changes, do not exactly represent quantities that we can measure or calculate. This paper outlines an approach to learn about how model parameters should be transformed between a gauged and an ungauged catchment. The approach consists of an iterative process, in which a model structure is applied successively to gauged catchments. After each step, parameter behavior is evaluated as a function of catchment properties and intercatchment similarities. The method is illustrated with an application of a customized version of TOPMODEL to a set of catchments in the Ecuadorian Andes. First, parameter sets are generated for a donor catchment. This model ensemble is then used to predict the discharge of the other catchments, after applying a stochastic parameter transformation to account for the uncertainty in the model migration. The parameter transformation is then evaluated and improved before further application. The case study shows that accurate predictions can be made for predicted basins. At the same time, knowledge is gained about model behavior and potential model limitations.

  • 20.
    Cheng, Hua
    et al.
    KTH, Tidigare Institutioner                               , Mark- och vattenteknik.
    Cvetkovic, Vladimir
    KTH, Tidigare Institutioner                               , Mark- och vattenteknik.
    Hydrodynamic control of tracer retention in heterogeneous rock fractures2003Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 39, nr 5, s. 1130-1139Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate the statistical properties of a Lagrangian random variable beta[T/L], which has been shown to quantify hydrodynamic impact on retention [Cvetkovic et al., 1999], using Monte Carlo simulations of flow and transport in a single fracture. The "local cubic law'' of water flow is generalized to a power law Qsimilar tob(n), where Q is the flow rate, b is the half aperture, and nless than or equal to3. Simulations of flow and particle transport are carried out assuming "local cubic law'' (n=3) and "local quadratic law'' (n=2), and for two typical flow configurations: uniform flow and radially converging flow. We find that beta is related to tau as betasimilar totau(m), where m is dependent on the power n and the configuration of flow and transport. Simulation results for uniform flow indicate that betasimilar totau(n/n-1) for a small source section; as the source section increases, we have the convergence to betasimilar totau. For radially converging flow, we find betasimilar totau for a small source section and a convergence to beta=const for an increasing source section. Simulation results for both flow configurations are consistent with the results for a homogeneous fracture. The results for a homogeneous fracture provide reasonable bounds for simulated beta. The correlation between beta and Q is relatively weak for all cases studied.

  • 21. Cvetkovic, V.
    et al.
    Carstens, C.
    Selroos, J.-O.
    Destouni, Georgia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Water and solute transport along hydrological pathways2012Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 48, nr 6, s. W06537-(15 pp)Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A Lagrangian framework for material transport along hydrological pathways is presented and consequences of statistically stationary space-time flow velocity variations on advective transport are investigated. The two specific questions addressed in this work are: How do temporal fluctuations affect forward and backward water travel time distributions when combined with spatial variability? and Can mass transfer processes be quantified using conditional probabilities in spatially and temporally variable flow? Space-time trajectories are studied for generic conditions of flow, with fully ergodic or only spatially ergodic velocity. It is shown that forward and backward distributions of advective water travel time coincide for statistically stationary space-time variations. Temporal variability alters the statistical structure of the Lagrangian velocity fluctuations. Once this is accounted for, integration of the memory function with the travel time distribution is applicable for quantifying retention. Further work is needed to better understand the statistical structure of space-time velocity variability in hydrological transport, as well as its impact on tracer retention and attenuation.

  • 22.
    Cvetkovic, V.
    et al.
    Royal Inst Technol, Dept Land & Water Resources, SE-10044 Stockholm, Sweden .
    Frampton, A.
    Royal Inst Technol, Dept Land & Water Resources, SE-10044 Stockholm, Sweden .
    Transport and retention from single to multiple fractures in crystalline rock at Aspo (Sweden): 2. Fracture network simulations and generic retention model2010Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 46, s. W05506-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hydrogeologic characterization of crystalline rock formations on the field scale is important for many applications but still presents a multitude of challenges. In this work we use comprehensive hydrostructural information and present a detailed simulation study of flow and advective transport in a discrete fracture network (DFN) that replicates the Tracer Retention Understanding Experiments (TRUE) Block Scale rock volume at the Aspo Hard Rock Laboratory (Sweden). Simulated water residence time tau and hydrodynamic retention parameter beta are used as independent constraints for estimating material retention properties as presented in paper 1 of this series, whereas simulated mean water residence times are compared with observed values. We find that the DFN simulations reproduce water residence times reasonably well, indicating that the characterization data are sufficient and that the DFN model does capture dominant features of the flow paths analyzed. The empirical quadratic law that relates aperture and transmissivity seems to better reproduce calibrated mean water residence times than the theoretical cubic law for the five flow paths. The active specific surface area (beta/tau) [1/L] as inferred from simulations is used for defining a generic retention model for the dominant rock type (Aspo diorite) that matches fairly well the entire range of calibrated retention parameters of the TRUE tests. The combination of paper 1 and this work provides a general, comprehensive methodology for evaluating tracer test results in crystalline rock where a comparable amount of information is available; critical to this methodology is that tracer tests are carried out using tracers with sufficiently different sorption affinities (of factor 10-100).

  • 23.
    Cvetkovic, Vladimir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattenvårdsteknik.
    A general memory function for modeling mass transfer in groundwater transport2012Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 48, s. W04528-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A power-law extension of the gamma distribution is proposed as a general memory function for capturing rate limitations of retention in groundwater transport. Using moments, we show how the new memory function can be reduced to most other forms available in the literature, exactly or approximately. The proposed formulation is suitable for field scale or laboratory scale transport modeling. Rate limitation effects are illustrated for solute transport by considering the fractional mass release over a given transport scale. The equilibrium and no-retention cases set bounds for contaminant attenuation, between which the impact of rate limitations is clearly exposed.

  • 24.
    Cvetkovic, Vladimir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    How accurate is predictive modeling of groundwater transport?: A case study of advection, macrodispersion, and diffusive mass transfer at the Forsmark site (Sweden)2013Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 49, nr 9, s. 5317-5327Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study predictive modeling of groundwater transport that accounts for three mechanisms: mean advection, macrodispersion, and mass transfer. A general methodology is presented and applied to a series of nonsorbing tracer tests along multiple pathways on scales ranging from ca. 70 to 300 m, in a highly heterogeneous aquifer at Forsmark (Sweden). The mean water residence time cannot be predicted well using a simple water balance model. Longitudinal macrodispersivity (L) (L) and a mass transfer parameter group (1/root T) are extrapolated from the control tracer experiments, to yield accurate predictions of tracer discharge, once the mean water residence time is constrained. A relatively simple modeling framework based on Fickian macrodispersion and diffusion seems to be adequate for reproducing the tracer discharge in this complex and highly heterogeneous porous media.

  • 25.
    Cvetkovic, Vladimir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattenvårdsteknik.
    Significance of fracture rim zone heterogeneity for tracer transport in crystalline rock2010Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 46, nr 3, s. W03504-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Conducting fractures of crystalline rock are typically altered over long periods of time. The fracture rim zone, a result of these alterations, will as a rule have different physical and chemical properties from the unaltered ("fresh'') rock, depending on various microscopic and macroscopic factors of the alterations. In this paper, we study the impact of rim zone heterogeneity, exemplified by a decreasing porosity trend as inferred from the Aspo Hard Rock Laboratory site (Sweden), on short- and long-term tracer transport. Our main finding is that this particular rim zone structure will have a dominant effect on transport of moderately to strongly sorbing tracers on experimental time scales and a notable effect on application time scales. The findings of this work lend further support to the interpretation of the relatively strong retention reported by Cvetkovic et al. The fracture rim zone porosity structure may provide an additional safety margin for sorbing radionuclides in crystalline rock at sites where fracture alteration is prevalent.

  • 26.
    Cvetkovic, Vladimir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Resurser, energi och infrastruktur.
    Statistical Formulation of Generalized Tracer Retention in Fractured Rock2017Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 53, nr 11, s. 8736-8759Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study tracer retention in fractured rock by combing Lagrangian and time domain random walk frameworks, as well as a statistical representation of the retention process. Mass transfer is quantified by the retention time distribution that follows from a Lagrangian coupling between advective transport and mass exchange processes, applicable for advection-dominated transport. A unifying parametrization is presented for generalized diffusion using two rates denoted by k(1) and k(2) where k(1) is a forward rate and k(2) a reverse rate, plus an exponent as an additional parameter. For the Fickian diffusion model, k(1) and k(2) are related to measurable retention properties of the fracture-matrix by the method of moments, whereas for the non-Fickian case dimensional analysis is used. The derived retention time distributions are exemplified for interpreting tracer tests as well as for predictive modeling of expected tracer breakthrough. We show that non-Fickian effects can be notable when transport is upscaled based on a non-Fickian interpretation of a tracer test for which deviations from Fickianity are relatively small. The statistical representation of retention clearly shows the significance of the forward rate k(1) which depends on the active specific surface area and is the most difficult parameter to characterize in the field.

  • 27.
    Cvetkovic, Vladimir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattenvårdsteknik.
    Tracer attenuation in groundwater2011Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 47, nr 12, s. W12541-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The self-purifying capacity of aquifers strongly depends on the attenuation of waterborne contaminants, i.e.,irreversible loss of contaminant mass on a given scale as a result of coupled transport and transformation processes. A general formulation of tracer attenuation in groundwater is presented. Basic sensitivities of attenuation to macrodispersion and retention are illustrated for a few typical retention mechanisms. Tracer recovery is suggested as an experimental proxy for attenuation. Unique experimental data of tracer recovery in crystalline rock compare favorably with the theoretical model that is based on diffusion-controlled retention. Non-Fickian hydrodynamic transport has potentially a large impact on field-scale attenuation of dissolved contaminants.

  • 28.
    Cvetkovic, Vladimir
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattenvårdsteknik.
    Carstens, Christoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattenvårdsteknik.
    Selroos, Jan-Olof
    Destouni, Georgia
    Water and solute transport along hydrological pathways2012Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 48, nr 6, s. W06537-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A Lagrangian framework for material transport along hydrological pathways is presented and consequences of statistically stationary space-time flow velocity variations on advective transport are investigated. The two specific questions addressed in this work are: How do temporal fluctuations affect forward and backward water travel time distributions when combined with spatial variability? and Can mass transfer processes be quantified using conditional probabilities in spatially and temporally variable flow? Space-time trajectories are studied for generic conditions of flow, with fully ergodic or only spatially ergodic velocity. It is shown that forward and backward distributions of advective water travel time coincide for statistically stationary space-time variations. Temporal variability alters the statistical structure of the Lagrangian velocity fluctuations. Once this is accounted for, integration of the memory function with the travel time distribution is applicable for quantifying retention. Further work is needed to better understand the statistical structure of space-time velocity variability in hydrological transport, as well as its impact on tracer retention and attenuation.

  • 29.
    Cvetkovic, Vladimir
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattenvårdsteknik.
    Cheng, H.
    Byegard, J.
    Winberg, A.
    Tullborg, E. -L
    Widestrand, H.
    Transport and retention from single to multiple fractures in crystalline rock at Aspo (Sweden): 1. Evaluation of tracer test results and sensitivity analysis2010Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 46, s. W05505-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We evaluate the breakthrough curves obtained within a comprehensive experimental program for investigating the retention properties of crystalline rock, referred to as Tracer Retention Understanding Experiments (TRUE). The tracer tests were conducted at the Aspo Hard Rock Laboratory (Sweden) in two phases jointly referred to as TRUE Block Scale (TBS); the TBS tests comprise a total of 17 breakthrough curves with nonsorbing and a range of sorbing tracers. The Euclidian length scales are between 10 and 30 m, compared to 5 m for the earlier tests TRUE-1. The unlimited diffusion model is consistent with measured breakthrough curves and is adopted here for evaluation. The model has four independent parameters, two of which are related to advection and dispersion, one which is related to diffusion-sorption, and one which is related to surface sorption; the individual retention parameters or properties cannot be inferred from breakthrough curves alone and require additional constraints. The mean water residence times for the TBS tests are in the range 15-250 h, whereas the coefficient of variation of the water residence times is in the range 0.4-0.6. A consistent trend is found in the calibrated retention parameters with the sorption affinities of the tracers involved. Using Bode sensitivity functions, it is shown that sensitivity increases for the retention parameter with increasing sorption affinity; for nonsorbing tracers, diffusion and hydrodynamic dispersion are shown to "compete," exhibiting similar effects; hence, their estimates are uncertain. The analysis presented here exposes a few fundamental limitations and sensitivities when evaluating diffusion-controlled retention in the subsurface; it is general and applicable to any site with comparable tracer test data. In part 2, it will be shown how discrete fracture network simulations based on the hydrostructural information available can be used for further constraining individual retention parameters, in particular, the active specific surface area (s(f)) and the rock matrix porosity (theta).

  • 30.
    Cvetkovic, Vladimir
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattenvårdsteknik.
    Cheng, Hua
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattenvårdsteknik.
    Evaluation of single-well injection-withdrawal tests in Swedish crystalline rock using the Lagrangian travel time approach2011Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 47, s. W02527-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of 10 single-well injection-withdrawal (SWIW) tests are evaluated with two tracers each: uranine and cesium (Cs). An evaluation tool for SWIW tests in crystalline rock is presented on the basis of the Lagrangian travel time approach, whereby probabilities of tracer particle residence times are computed for key stages of the test cycle. Calibration results for three transport parameters and each breakthrough curve are presented. We show that estimates of the controlling retention parameter group psi [1/root T] are robust for Cs but highly uncertain for uranine. The estimated retention for Cs is larger for the Laxemar-Simpevarp site compared to the Forsmark site. Deviations from the -3/2 asymptotic breakthrough curve slope observed in a few of the tests at Forsmark are possibly due to a thin fracture coating that has been identified in mineralogical studies at some locations of the site.

  • 31.
    Cvetkovic, Vladimir
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattenvårdsteknik.
    Cheng, Hua
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Sorbing tracer experiments in a crystalline rock fracture at Aspo (Sweden): 3. Effect of microscale heterogeneity2008Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 44, nr 12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the impact of microscale (10(-3) -10(-2) m) heterogeneity in material and structural properties on sorbing tracer transport in a single crystalline fracture of the TRUE-1 tests (mesoscale, 5 m) at Aspo (Sweden). The analysis is based on the microscale characterization results as presented in part 1 of this series. Our main objective in this last part of the series is to provide an independent interpretation (or "prediction'') of the effective parameters as estimated from calibration in part 2 by combining the data presented in part 1 with analytical and numerical transport modeling. We show here that the independent information from microscopic characterization can be used for "predicting'' the effective diffusion time t(d) reasonably well; a discrepancy is to be expected given the uncertainties of microscale retention properties, in particular of the sorption coefficient.

  • 32.
    Cvetkovic, Vladimir
    et al.
    KTH, Tidigare Institutioner                               , Mark- och vattenteknik.
    Cheng, Hua
    KTH, Tidigare Institutioner                               , Mark- och vattenteknik.
    Wen, X. -H.
    Analysis of nonlinear effects on tracer migration in heterogeneous aquifers using Lagrangian travel time approach1996Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 32, nr 6, s. 1671-1680Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Advective transport in a heterogeneous two-dimensional aquifer is simulated and quantified by the statistical moments of tracer travel time and transverse displacement. These moments depend on the statistics of the Lagrangian velocity given as a function of space rather than time. A comparison is made with first-order results that appear to be robust for log transmissivity variance at least up to 1. Lagrangian statistics for travel time clearly expose a few essential features of nonlinear transport: nonstationary distribution and the increasing integral scale of the Lagrangian velocity. These reflect the tendency of streamlines to concentrate into relatively few flow paths ('preferential flow') for increasing log transmissivity variance. Two simple empirical relationships are identified that in combination with first-order results for the flow capture the main features of nonlinear transport. The proposed methodology can readily be generalized for analyzing advective transport under more complex flow conditions and for establishing relatively simple analytical models for estimating solute mass flux in heterogeneous aquifers.

  • 33.
    Cvetkovic, Vladimir
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattenvårdsteknik.
    Cheng, Hua
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Widestrand, H.
    Byegard, J.
    Winberg, A.
    Andersson, P.
    Sorbing tracer experiments in a crystalline rock fracture at Aspo (Sweden): 2. Transport model and effective parameter estimation2007Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 43, nr 11Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    [1] Transport and retention of sorbing tracers in a single, altered crystalline rock fracture on a 5 m scale is investigated. We evaluate the results of a comprehensive field study ( referred to as Tracer Retention Understanding Experiments, first phase ( TRUE- 1)), at a 400 m depth of the Aspo Hard Rock Laboratory ( Sweden). A total of 16 breakthrough curves are analyzed, from three test configurations using six radioactive tracers with a broad range of sorption properties. A transport- retention model is proposed, and its applicability is assessed based on available data. We find that the conventional model with an asymptotic power law slope of - 3/ 2 ( one- dimensional diffusion into an unlimited rock matrix) is a reasonable approximation for the conditions of the TRUE- 1 tests. Retention in the altered rock of the rim zone appears to be significantly stronger than implied by retention properties inferred from generic ( unaltered) rock samples. The effective physical parameters which control retention ( matrix porosity and retention aperture) are comparable for all three test configurations. The most plausible in situ ( rim zone) porosity is in the range 1% - 2%, which constrains the effective retention aperture to the range 0.2 - 0.7 mm. For all sorbing tracers the estimated in situ sorption coefficient appears to be larger by at least a factor of 10, compared to the value inferred from through- diffusion tests using unaltered rock samples.

  • 34.
    Cvetkovic, Vladimir
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Fiori, Aldo
    Dagan, Gedeon
    Solute transport in aquifers of arbitrary variability: A time-domain random walk formulation2014Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 50, nr 7, s. 5759-5773Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Solute transport in three-dimensional aquifers, with spatially varying hydraulic conductivity of arbitrary point distribution is investigated. The basis of our study is a multiindicator model (MIM) representation of the heterogeneity, combined with a self-consistent approximation for groundwater flow and particle transport. A time-domain random walk (TDRW) approach is presented for computing the expected mass arrival along the longitudinal transport direction that is simple and honors the hydrodynamics of flow for any variability. Using hydraulic conductivity measurements at the MADE site and the MIM, it is shown that the travel time distribution for large variability, cannot be well reproduced by the common distributions used for modeling hydrological transport, such as the log-normal distribution, or the inverse-Gaussian distribution. The proposed TDRW approach directly relates to the Lagrangian trajectory formulation and is appropriate for applications where occurrence of negative flow velocities is small. These results open new possibilities for modeling solute transport in aquifers of arbitrary variability by the time-domain random walk that can readily account for a wide range of mass transfer reactions.

  • 35. Cvetkovic, Vladimir
    et al.
    Frampton, Andrew
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Solute transport and retention in three-dimensional fracture networks2012Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 48, s. W02509-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Resolving the hydrodynamic control of retention is an important step in predictive modeling of transport of sorbing tracers in fractured rock. The statistics of the transport resistance parameter beta [T/L] and the related effective active specific surface area s(f) [1/L] are studied in a crystalline rock volume on a 100 m scale. Groundwater flow and advective transport are based on generic boundary conditions and realistic discrete fracture networks inferred from the Laxemar site, southeast Sweden. The overall statistics of beta are consistent with statistics of the water residence time tau; the moments of beta vary linearly with distance, at least up to 100 m. The correlation between log tau and log beta is predominantly linear, however, there is significant dispersion; the parameter s(f) strongly depends on the assumed hydraulic law (theoretical cubic or empirical quadratic). Fast and slow trajectories/segments in the network determine the shape of the beta distribution that cannot be reproduced by infinitely divisible model over the entire range; the low value range and median can be reproduced reasonably well with the tempered one-sided stable density using the exponent in the range 0.35-0.7. The low percentiles of the beta distribution seems to converge to a Fickian type of behavior from a 50 to 100 m scale.

  • 36.
    Cvetkovic, Vladimir
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Frampton, Andrew
    Solute transport and retention in three-dimensional fracture networks2012Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 48, s. W02509-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Resolving the hydrodynamic control of retention is an important step in predictive modeling of transport of sorbing tracers in fractured rock. The statistics of the transport resistance parameter beta [T/L] and the related effective active specific surface area s(f) [1/L] are studied in a crystalline rock volume on a 100 m scale. Groundwater flow and advective transport are based on generic boundary conditions and realistic discrete fracture networks inferred from the Laxemar site, southeast Sweden. The overall statistics of beta are consistent with statistics of the water residence time tau; the moments of beta vary linearly with distance, at least up to 100 m. The correlation between log tau and log beta is predominantly linear, however, there is significant dispersion; the parameter s(f) strongly depends on the assumed hydraulic law (theoretical cubic or empirical quadratic). Fast and slow trajectories/segments in the network determine the shape of the beta distribution that cannot be reproduced by infinitely divisible model over the entire range; the low value range and median can be reproduced reasonably well with the tempered one-sided stable density using the exponent in the range 0.35-0.7. The low percentiles of the beta distribution seems to converge to a Fickian type of behavior from a 50 to 100 m scale.

  • 37.
    Cvetkovic, Vladimir
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Frampton, Andrew
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Transport and retention from single to multiple fractures in crystalline rock at Äspö (Sweden): 2. Fracture network simulations and generic retention model.2010Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hydrogeologic characterization of crystalline rock formations on the field scale is important for many applications but still presents a multitude of challenges [Neuman, 2005]. In this work we use comprehensive hydro-structural information and present a detailed simulation study of flow and advective transport in a discrete fracture network (DFN) that replicates the TRUE Block Scale rock volume at the Äspö Hard Rock Laboratory (Sweden). Simulated water residence time τ and hydrodynamic retention parameter β are used as independent constraints for estimating material retention properties as presented in part 1 of this series [Cvetkovic et al., 2009] whereas simulated mean water residence times are compared with observed values. We find that the DFN simulations reproduce water residence times reasonably well, indicating that the characterization data are sufficient and that the DFN model does capture dominant features of the flow paths analyzed. The empirical quadratic law that relates aperture and transmissivity seems to better reproduce calibrated mean water residence times than the theoretical cubic law, for the five flow paths. The active specific surface area (β/τ) [1/L] as inferred from simulations, is used for defining a generic retention model for the dominant rock type (”Äspö diorite”) that matches fairly well the entire range of calibrated retention parameters of the TRUE tests. The combination of Part 1 and this work provide a general, comprehensive methodology for evaluating tracer test results in crystalline rock where a comparable amount of information is available; critical to this methodology is that tracer tests are carried out using tracers with sufficiently different sorption affinities (of factor 10 to 100).

  • 38.
    Cvetkovic, Vladimir
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Gotovac, Hrvoje
    Flow-dependence of matrix diffusion in highly heterogeneous rock fractures2013Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 49, nr 11, s. 7587-7597Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Diffusive mass transfer in rock fractures is strongly affected by fluid flow in addition to material properties. The flow-dependence of matrix diffusion is quantified by a random variable ("transport resistance'') denoted as beta [T/L] and computed from the flow field by following advection trajectories. The numerical methodology for simulating fluid flow is mesh-free, using Fup basis functions. A generic statistical model is used for the transmissivity field, featuring three correlation structures: (i) highly connected non-multiGaussian; (ii) poorly connected (or disconnected) non-multi-Gaussian; and (iii) multi-Gaussian. The moments of beta are shown to be linear with distance, irrespective of the structure, after approximately 10 integral scales of ln T. Percentiles of beta are found to be linear with the mean beta when considering all three structures. Taking advantage of this property, a potentially useful relationship is presented between beta percentiles and the fracture mean water residence time that integrates all structures with high variability; it can be used in discrete fracture network simulations where T statistical data on individual fractures are not available.

  • 39.
    Cvetkovic, Vladimir
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Gotovac, Hrvoje
    On the upscaling of chemical transport in fractured rock2014Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 50, nr 7, s. 5797-5816Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The impact of flow heterogeneity on chemical transport from single to multiple fractures is investigated. The emphasis is on the dynamic nature of the specific surface area (SSA) due to heterogeneity of the flow, relative to a purely geometrical definition. The flow-dependent SSA is interpreted probabilistically, following inert tracer particles along individual fractures. Upscaling to a fracture network is proposed as a time domain random walk based on the statistics of SSA for single fractures. Statistics of SSA are investigated for three correlation structures of transmissivity: multi-Gaussian and two non-multi-Gaussian. The mean of SSA stabilizes after similar to 20 fractures at different values depending on whether the cubic or quadratic hydraulic law is assumed. The results are tested against comprehensive DFN simulations based on site-specific data but also against direct estimates from a wider range of tracer tests. The proposed time domain random walk methodology sets bounds for SSA in a 75% confidence interval as similar to 1800 1/m and 27,000 1/m, with a median of 14,000 1/m; these values capture reasonably well both the DFN simulation and tracer test SSA data. Presented results may be particularly relevant when quantifying uncertainty of reactive transport modeling in fractured rock.

  • 40.
    Cvetkovic, Vladimir
    et al.
    KTH, Tidigare Institutioner, Mark- och vattenteknik.
    Painter, S.
    Outters, N.
    Selroos, J. O.
    Stochastic simulation of radionuclide migration in discretely fractured rock near the Aspo Hard Rock Laboratory2004Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 40, nr 2, s. W02404-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the migration of sorbing tracers through crystalline rock by combining relatively simple transport measures with particle tracking in a discrete fracture network. The rock volume is on a 100 m scale and is a replica of a thoroughly characterized site at the Aspo Hard Rock Laboratory, Sweden. Flow is driven by generic boundary conditions consistent with the natural gradient in the region. The emphasis is on the global effect of fracture-to-fracture hydraulic variability where individual fractures are assumed to be of uniform aperture. The transport measures are conditioned on two random variables: the water residence time (tau) and a parameter which quantifies the hydrodynamic control of retention (beta). Results are illustrated for two radionuclides: technetium (strongly sorbing) and strontium (weakly sorbing). It is found that the assumption of streamline routing or full mixing at fracture intersections has comparatively little impact on transport. The choice of the cubic or quadratic hydraulic law (i.e., relation between transmissivity and aperture) strongly affects water residence times but has little impact on average transport since it does not affect the statistics of beta. If the statistics of beta are known, then the distribution of water residence time (tau) is of little importance for transport. We assess the applicability of a linearized model beta = tau/b(ret) using two different approaches to estimate the effective retention'' aperture 2b(ret): from transmissivity data and from fracture density and flow porosity data. Under some conditions, these conventional estimates may provide acceptable representation of transport. The results stress the need for further studies on upscaling of tau, beta distributions as well as on estimating effective parameters for hydraulic control of retention.

  • 41.
    Cvetkovic, Vladimir
    et al.
    KTH, Tidigare Institutioner                               , Mark- och vattenteknik.
    Painter, S.
    Turner, D.
    Pickett, D.
    Bertetti, P.
    Parameter and model sensitivities for colloid-facilitated radionuclide transport on the field scale2004Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 40, nr 6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate the potential effects of inorganic colloids on radionuclide transport in groundwater using generic sensitivity studies and an example based on the alluvial aquifer near Yucca Mountain, Nevada. Our emphasis is on kinetically controlled sorption of radionuclides on mobile and immobile colloids. Three kinetic sorption models are considered for the sensitivity analysis: bilinear, Langmuir, and linear. Plutonium is assumed to be injected into the Yucca Mountain alluvial aquifer at a constant rate and follows a random stream tube to a monitoring boundary. The linear sorption model provides a reasonable upper bound on colloid-facilitated plutonium transport for the site-specific conditions. In the absence of colloid filtration and retardation, colloids enhance the plutonium discharge by a large factor over the situation without colloids. Exchange of plutonium between solution and reversibly attached colloids makes colloid retardation relatively ineffective at reducing colloid-facilitated transport except when the retardation factor is large. Irreversible removal of colloids (filtration) is more effective than retardation at reducing colloid-facilitated transport. For fixed filtration rate the degree of attenuation depends sensitively and nonmonotonically on the rate of plutonium desorption from colloids. These results emphasize the need for accurate measurements of rates of desorption from colloids as well as in situ studies of filtration of naturally occurring colloids.

  • 42. Davies, J.
    et al.
    Beven, Keith
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Rodhe, Allan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Nyberg, L.
    Bishop, Kevin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Integrated modeling of flow and residence times at the catchment scale with multiple interacting pathways2013Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 49, nr 8, s. 4738-4750Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is still a need for catchment hydrological and transport models that properly integrate the effects of preferential flows while accounting for differences in velocities and celerities. A modeling methodology is presented here which uses particle tracking methods to simulate both flow and transport in multiple pathways in a single consistent solution. Water fluxes and storages are determined by the volume and density of particles and transport is attained by labeling the particles with information that may be tracked throughout the lifetime of that particle in the catchment. The methodology allows representation of preferential flows through the use of particle velocity distributions, and mixing between pathways can be achieved with pathway transition probabilities. A transferable 3-D modeling methodology is presented for the first time and applied to a unique step-shift isotope experiment that was carried out at the 0.63 ha G1 catchment in Gardsjon, Sweden. This application highlights the importance of combining flow and transport in hydrological representations, and the importance of pathway velocity distributions and interactions in obtaining a satisfactory representation of the observations.

  • 43.
    Davies, Jessica
    et al.
    Lancaster University.
    Beven, Keith
    Lancaster University.
    Rodhe, Allan
    Uppsala universitet.
    Nyberg, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Centrum för klimat och säkerhet.
    Bishop, Kevin
    Uppsala universitet.
    Integrated modeling of flow and residence times at the catchment scale with multiple interacting pathways2013Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 49, nr 8, s. 4738-4750Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is still a need for catchment hydrological and transport models that properly integrate the effects of preferential flows while accounting for differences in velocities and celerities. A modeling methodology is presented here which uses particle tracking methods to simulate both flow and transport in multiple pathways in a single consistent solution. Water fluxes and storages are determined by the volume and density of particles and transport is attained by labeling the particles with information that may be tracked throughout the lifetime of that particle in the catchment. The methodology allows representation of preferential flows through the use of particle velocity distributions, and mixing between pathways can be achieved with pathway transition probabilities. A transferable 3-D modeling methodology is presented for the first time and applied to a unique step-shift isotope experiment that was carried out at the 0.63 ha G1 catchment in Gårdsjön, Sweden. This application highlights the importance of combining flow and transport in hydrological representations, and the importance of pathway velocity distributions and interactions in obtaining a satisfactory representation of the observations.

  • 44. de Barros, F. P. J.
    et al.
    Bellin, A.
    Cvetkovic, Vladimir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Dagan, G.
    Fiori, A.
    Aquifer heterogeneity controls on adverse human health effects and the concept of the hazard attenuation factor2016Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 52, nr 8, s. 5911-5922Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We analyze the probability distribution of the hazard attenuation factor for a noncarcinogenic reactive compound captured by a well in heterogeneous porous formations. The hazard attenuation factor is defined as the ratio between the hazard index HI at a detection well and at the source. Heterogeneity of the aquifer is represented through the multi-indicator model (a collection of blocks of independent permeability) while flow and transport are solved by the means of the self-consistent approach that is able to deal with any degree of heterogeneity. Due to formation heterogeneity, HI is a random variable and similar for hazard attenuation index. The latter can be fully characterized by its cumulative distribution function (CDF), which in turn can be related to the statistics of the travel time of solute particles, from the source to the detection well. The approach is applied to the case of a solute which undergoes decay and a well with a screen much smaller than the correlation scale of hydraulic conductivity. The results show that the probability of exceeding a given acceptable threshold of the hazard index is significantly affected by the level of heterogeneity comparable to the one observed for the MADE site, and the distance between the source and the well.

  • 45. Delsman, Joost R.
    et al.
    Essink, Gualbert H. P. Oude
    Beven, Keith J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Stuyfzand, Pieter J.
    Uncertainty estimation of end-member mixing using generalized likelihood uncertainty estimation (GLUE), applied in a lowland catchment2013Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 49, nr 8, s. 4792-4806Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    End-member mixing models have been widely used to separate the different components of a hydrograph, but their effectiveness suffers from uncertainty in both the identification of end-members and spatiotemporal variation in end-member concentrations. In this paper, we outline a procedure, based on the generalized likelihood uncertainty estimation (GLUE) framework, to more inclusively evaluate uncertainty in mixing models than existing approaches. We apply this procedure, referred to as G-EMMA, to a yearlong chemical data set from the heavily impacted agricultural Lissertocht catchment, Netherlands, and compare its results to the traditional end-member mixing analysis (EMMA). While the traditional approach appears unable to adequately deal with the large spatial variation in one of the end-members, the G-EMMA procedure successfully identified, with varying uncertainty, contributions of five different end-members to the stream. Our results suggest that the concentration distribution of effective end-members, that is, the flux-weighted input of an end-member to the stream, can differ markedly from that inferred from sampling of water stored in the catchment. Results also show that the uncertainty arising from identifying the correct end-members may alter calculated end-member contributions by up to 30%, stressing the importance of including the identification of end-members in the uncertainty assessment.

  • 46.
    Dessirier, Benoît
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Frampton, Andrew
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Fransson, A.
    Jarsjö, Jerker
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Modeling early in situ wetting of a compacted bentonite buffer installed in low permeable crystalline bedrock2016Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 52, nr 8, s. 6207-6221Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The repository concept for geological disposal of spent nuclear fuel in Sweden and Finland is planned to be constructed in sparsely fractured crystalline bedrock and with an engineered bentonite buffer to embed the waste canisters. An important stage in such a deep repository is the postclosure phase following the deposition and the backfilling operations when the initially unsaturated buffer material gets hydrated by the groundwater delivered by the natural bedrock. We use numerical simulations to interpret observations on buffer wetting gathered during an in situ campaign, the Bentonite Rock Interaction Experiment, in which unsaturated bentonite columns were introduced into deposition holes in the floor of a 417 m deep tunnel at the Aspo Hard Rock Laboratory in Sweden. Our objectives are to assess the performance of state-of-the-art flow models in reproducing the buffer wetting process and to investigate to which extent dependable predictions of buffer wetting times and saturation patterns can be made based on information collected prior to buffer insertion. This would be important for preventing insertion into unsuitable bedrock environments. Field data and modeling results indicate the development of a de-saturated zone in the rock and show that in most cases, the presence or absence of fractures and flow heterogeneity are more important factors for correct wetting predictions than the total inflow. For instance, for an equal open-hole inflow value, homogeneous inflow yields much more rapid buffer wetting than cases where fractures are represented explicitly thus creating heterogeneous inflow distributions.

  • 47.
    Dessirier, Benoît
    et al.
    Stockholms universitet, Institutionen för naturgeografi.
    Frampton, Andrew
    Stockholms universitet, Institutionen för naturgeografi.
    Fransson, A.
    Jarsjö, Jerker
    Stockholms universitet, Institutionen för naturgeografi.
    Modeling early in situ wetting of a compacted bentonite buffer installed in low permeable crystalline bedrock2016Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 52, nr 8, s. 6207-6221Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The repository concept for geological disposal of spent nuclear fuel in Sweden and Finland is planned to be constructed in sparsely fractured crystalline bedrock and with an engineered bentonite buffer to embed the waste canisters. An important stage in such a deep repository is the postclosure phase following the deposition and the backfilling operations when the initially unsaturated buffer material gets hydrated by the groundwater delivered by the natural bedrock. We use numerical simulations to interpret observations on buffer wetting gathered during an in situ campaign, the Bentonite Rock Interaction Experiment, in which unsaturated bentonite columns were introduced into deposition holes in the floor of a 417 m deep tunnel at the Aspo Hard Rock Laboratory in Sweden. Our objectives are to assess the performance of state-of-the-art flow models in reproducing the buffer wetting process and to investigate to which extent dependable predictions of buffer wetting times and saturation patterns can be made based on information collected prior to buffer insertion. This would be important for preventing insertion into unsuitable bedrock environments. Field data and modeling results indicate the development of a de-saturated zone in the rock and show that in most cases, the presence or absence of fractures and flow heterogeneity are more important factors for correct wetting predictions than the total inflow. For instance, for an equal open-hole inflow value, homogeneous inflow yields much more rapid buffer wetting than cases where fractures are represented explicitly thus creating heterogeneous inflow distributions.

  • 48.
    Destouni, Georgia
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Fischer, Ida
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Prieto, Carmen
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Water quality and ecosystem management: Data-driven reality check of effects in streams and lakes2017Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 53, nr 8, s. 6395-6406Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigates nutrient-related water quality conditions and change trends in the first management periods of the EU Water Framework Directive (WFD; since 2009) and Baltic Sea Action Plan (BASP; since 2007). With mitigation of nutrients in inland waters and their discharges to the Baltic Sea being a common WFD and BSAP target, we use Sweden as a case study of observable effects, by compiling and analyzing all openly available water and nutrient monitoring data across Sweden since 2003. The data compilation reveals that nutrient monitoring covers only around 1% (down to 0.2% for nutrient loads) of the total number of WFD-classified stream and lake water bodies in Sweden. The data analysis further shows that the hydro-climatically driven water discharge dominates the determination of waterborne loads of both total phosphorus and total nitrogen across Sweden. Both water discharge and the related nutrient loads are in turn well correlated with the ecosystem status classification of Swedish water bodies. Nutrient concentrations do not exhibit such correlation and their changes over the study period are on average small, but concentration increases are found for moderate-to-bad status waters, for which both the WFD and the BSAP have instead targeted concentration decreases. In general, these results indicate insufficient distinction and mitigation of human-driven nutrient components in inland waters and their discharges to the sea by the internationally harmonized applications of the WFD and the BSAP. The results call for further comparative investigations of observable large-scale effects of such regulatory/management frameworks in different parts of the world.

  • 49.
    Destouni, Georgia
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Prieto, Carmen
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Quantifying hydrological and tidal influences on groundwater discharges into coastal waters2005Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 41, nr 12, s. W12427-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    [1] In coastal aquifers the dynamic mixing zone between intruding seawater and fresh groundwater constitutes a zone of salinity transition that may supply brackish groundwater along with chemical tracers and nutrients to coastal waters. Tidal influence has been proposed as a possible mechanism for enhancement of recirculated seawater, total submarine groundwater discharge (SGD), and associated tracer loading through salinity transition zones into coastal waters. We show that tidal oscillation may, for relatively low SGD cases, considerably increase the average recirculated seawater component of total SGD relative to nontidal conditions. High SGD cases, however, are dominated by and require large fresh groundwater flow components also under tidal conditions; this result is obtained from a wide range of different groundwater simulation scenarios and is supported by direct comparison with field data from different reported high-SGD sites in the world. For cases with hydrologically limited fresh groundwater flow directly into the sea we propose that observed excessive coastal loading of groundwater-derived tracers may be the result of large groundwater flow and transport into unmonitored coastal stream reaches, in addition to SGD.

  • 50.
    Di Baldassarre, Giuliano
    et al.
    Faculty of Engineering, University of Bologna, Bologna, Italy.
    BRATH, A
    MONTANARI, A
    Reliability of different depth-duration-frequency equations for estimating short-duration design storms2006Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 42, nr 12, s. W12501-Artikkel i tidsskrift (Fagfellevurdert)
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