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  • 1.
    Achleitner, Stefan
    et al.
    Unit of Hydraulic Engineering, University of Innsbruck.
    Schröber, Johannes
    AlpS - Centre for Climate Change Adaptation Technologies, Innsbruck.
    Rinderer, Michael
    Hydrology and Climate Unit, Department of Geography, University of Zurich.
    Leonhardt, Günther
    Unit of Environmental Engineering, University of Innsbruck.
    Schöberl, Friedrich
    Institute of Geography, University of Innsbruck.
    Kirnbauer, Robert
    Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology.
    Schönlaub, Helmut
    TIWAG - Tiroler Wasserkraft AG.
    Analyzing the operational performance of the hydrological models in an alpine flood forecasting system2012In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 412-413, p. 90-100Article in journal (Refereed)
    Abstract [en]

    During recent years a hybrid model has been set up for the operational forecasting of flood discharges in the 6750km 2 Tyrolean part of the River Inn catchment in Austria. The catchment can be characterized as a typical alpine area with large variations in altitude. The paper is focused on the error analysis of discharge forecasts of four main tributary catchments simulated with hydrological water balance models. The selected catchments cover an area of 2230km 2, where the non-glaciated and glaciated parts are modeled using the semi-distributed HQsim and the distributed model SES, respectively.The forecast errors are evaluated as a function of forecast lead time and forecasted discharge magnitude using 14 events from 2007 to 2010. The observed and forecasted precipitation inputs were obtained under operational conditions. The mean relative bias of the forecasted discharges revealed to be constant with regard to the forecast lead time, varying between 0.2 and 0.25 for the different catchments. The errors as a function of the forecasted discharge magnitude showed large errors at lower values of the forecast hydrographs, where errors decreased significantly at larger discharges being relevant in flood forecasting

  • 2. Ala-aho, P.
    et al.
    Soulsby, C.
    Pokrovsky, O. S.
    Kirpotin, S. N.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Serikova, Svetlana
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Vorobyev, S. N.
    Manasypov, R. M.
    Loiko, S.
    Tetzlaff, D.
    Using stable isotopes to assess surface water source dynamics and hydrological connectivity in a high-latitude wetland and permafrost influenced landscape2018In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 556, p. 279-293Article in journal (Refereed)
    Abstract [en]

    Climate change is expected to alter hydrological and biogeochemical processes in high-latitude inland waters. A critical question for understanding contemporary and future responses to environmental change is how the spatio-temporal dynamics of runoff generation processes will be affected. We sampled stable water isotopes in soils, lakes and rivers on an unprecedented spatio-temporal scale along a 1700 km transect over three years in the Western Siberia Lowlands. Our findings suggest that snowmelt mixes with, and displaces, large volumes of water stored in the organic soils and lakes to generate runoff during the thaw season. Furthermore, we saw a persistent hydrological connection between water bodies and the landscape across permafrost regions. Our findings help to bridge the understanding between small and large scale hydrological studies in high-latitude systems. These isotope data provide a means to conceptualise hydrological connectivity in permafrost and wetland influenced regions, which is needed for an improved understanding of future biogeochemical changes.

  • 3. Amaguchi, H.
    et al.
    Kawamura, A.
    Olsson, Jonas
    SMHI, Research Department, Hydrology.
    Takasaki, T.
    Development and testing of a distributed urban storm runoff event model with a vector-based catchment delineation2012In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 420, p. 205-215Article in journal (Refereed)
    Abstract [en]

    The recent advances in GIS technology as well as data availability open up new possibilities concerning urban storm runoff modeling. In this paper, a vector-based distributed storm event runoff model - the Tokyo Storm Runoff (TSR) model - is developed and tested for urban runoff analysis using two historical storm events. The set-up of this model is based on urban landscape GIS delineation that faithfully describes the complicated urban land use features in detail. The flow between single spatial elements is based on established hydraulic and hydrological models with equations that describe all aspects of storm runoff generation in an urban environment. The model was set up and evaluated for the small urban lower Ekota catchment in Tokyo Metropolis, Japan. No calibration or tuning was performed, but the general model formulation was used with standard parameter values obtained from the literature. The runoff response to two storm events were simulated; one minor event resulting only in a small-scale flood wave and one major event which inundated parts of the catchment. For both events, the simulated water levels closely reproduced the observed ones. For the major event, also the reported inundation area was well described by the model. It was also demonstrated how the model can be used to evaluate the flow conditions in specific components of the urban hydrological system, which facilitates e.g. evaluation of flood-preventive measures. (C) 2011 Elsevier B.V. All rights reserved.

  • 4.
    Amvrosiadi, Nino
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Bishop, Kevin
    Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Uppsala, Sweden.
    Seibert, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Univ Zurich, Dept Geog, Zurich, Switzerland.
    Soil moisture storage estimation based on steady vertical fluxes under equilibrium2017In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 553, p. 798-804Article in journal (Refereed)
    Abstract [en]

    Soil moisture is an important variable for hillslope and catchment hydrology. There are various computational methods to estimate soil moisture and their complexity varies greatly: from one box with vertically constant volumetric soil water content to fully saturated-unsaturated coupled physically-based models. Different complexity levels are applicable depending on the simulation scale, computational time limitations, input data and knowledge about the parameters. The Vertical Equilibrium Model (VEM) is a simple approach to estimate the catchment-wide soil water storage at a daily time-scale on the basis of water table level observations, soil properties and an assumption of hydrological equilibrium without vertical fluxes above the water table. In this study VEM was extended by considering vertical fluxes, which allows conditions with evaporation and infiltration to be represented. The aim was to test the hypothesis that the simulated volumetric soil water content significantly depends on vertical fluxes. The water content difference between the no-flux, equilibrium approach and the new constant-flux approach greatly depended on the soil textural class, ranging between similar to 1% for silty clay and similar to 44% for sand at an evapotranspiration rate of 5 mm.d(-1). The two approaches gave a mean volumetric soil water content difference of 1 mm for two case studies (sandy loam and organic rich soils). The results showed that for many soil types the differences in estimated storage between the no-flux and the constant flux approaches were relatively small.

  • 5.
    Andersson, Lotta
    et al.
    SMHI, Core Services.
    Wilk, Julie
    Todd, Martin C.
    Hughes, Denis A.
    Earle, Anton
    Kniveton, Dominic
    Layberry, Russet
    Savenije, Hubert H. G.
    Impact of climate change and development scenarios on flow patterns in the Okavango River2006In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 331, no 1-2, p. 43-57Article in journal (Refereed)
    Abstract [en]

    This paper lays the foundation for the use of scenario modelling as a tool for integrated water resource management in the Okavango River basin. The Pitman hydrological model is used to assess the impact of various development and climate change scenarios on downstream river flow. The simulated impact on modelled river discharge of increased water use for domestic use, livestock, and informal irrigation (proportional to expected population increase) is very limited. Implementation of all likely potential formal irrigation schemes mentioned in available reports is expected to decrease the annual flow by 2% and the minimum monthly flow by 5%. The maximum possible impact of irrigation on annual average flow is estimated as 8%, with a reduction of minimum monthly flow by 17%. Deforestation of all areas within a 1 km buffer around the rivers is estimated to increase the flow by 6%. However, construction of all potential hydropower reservoirs in the basin may change the monthly mean flow distribution dramatically, although under the assumed operational rules, the impact of the dams is only substantial during wet years. The simulated impacts of climate change are considerable larger that those of the development scenarios (with exception of the high development scenario of hydropower schemes) although the results are sensitive to the choice of GCM and the IPCC SRES greenhouse gas (GHG) emission scenarios. The annual mean water flow predictions for the period 2020-2050 averaged over scenarios from all the four GCMs used in this study are close to the present situation for both the A2 and B2 GHG scenarios. For the 2050-2080 and 2070-2099 periods the all-GCM mean shows a flow decrease of 20% (14%) and 26% (17%), respectively, for the A2 (B2) GHG scenarios. However, the uncertainty in the magnitude of simulated future changes remains high. The simulated effect of climate change on minimum monthly flow is proportionally higher than the impact on the annual mean flow. (c) 2006 Elsevier B.V. All rights reserved.

  • 6.
    Andersson, Lotta
    et al.
    Linköping University, The Tema Institute, Centre for Climate Science and Policy Research . Linköping University, The Tema Institute, Department of Water and Environmental Studies.
    Wilk, Julie
    Linköping University, The Tema Institute, Centre for Climate Science and Policy Research . Linköping University, The Tema Institute, Department of Water and Environmental Studies.
    Todd, Martin
    University College of London.
    Hughes, Denis
    Research Rhodes University, South Africa.
    Earle, Anton
    University of Pretoria, South Africa.
    Kniveton, Dominic
    University of Sussex, UK.
    Layberry, Russel
    University of Sussex, UK.
    Savenije, Hubert
    Delft University of Technology, Netherlands.
    Impact of climate change and development scenarios on flow patterns in the Okavango River2006In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 331, no 1-2, p. 43-57Article in journal (Refereed)
    Abstract [en]

    This paper lays the foundation for the use of scenario modelling as a tool for integrated water resource management in the Okavango River basin. The Pitman hydrological model is used to assess the impact of various development and climate change scenarios on downstream river flow. The simulated impact on modelled river discharge of increased water use for domestic use, livestock, and informal irrigation (proportional to expected population increase) is very limited. Implementation of all likely potential formal irrigation schemes mentioned in available reports is expected to decrease the annual flow by 2% and the minimum monthly flow by 5%. The maximum possible impact of irrigation on annual average flow is estimated as 8%, with a reduction of minimum monthly flow by 17%. Deforestation of all areas within a 1 km buffer around the rivers is estimated to increase the flow by 6%. However, construction of all potential hydropower reservoirs in the basin may change the monthly mean flow distribution dramatically, although under the assumed operational rules, the impact of the dams is only substantial during wet years. The simulated impacts of climate change are considerable larger that those of the development scenarios (with exception of the high development scenario of hydropower schemes) although the results are sensitive to the choice of GCM and the IPCC SRES greenhouse gas (GHG) emission scenarios. The annual mean water flow predictions for the period 2020-2050 averaged over scenarios from all the four GCMs used in this study are close to the present situation for both the A2 and B2 GHG scenarios. For the 2050-2080 and 2070-2099 periods the all-GCM mean shows a flow decrease of 20% (14%) and 26% (17%), respectively, for the A2 (B2) GHG scenarios. However, the uncertainty in the magnitude of simulated future changes remains high. The simulated effect of climate change on minimum monthly flow is proportionally higher than the impact on the annual mean flow. © 2006 Elsevier B.V. All rights reserved.

  • 7.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Lidén, R.
    SMHI.
    Nitrogen and phosphorus concentrations from agricultural catchments - influence of spatial and temporal variables2000In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 227, no 1-4, p. 140-159Article in journal (Refereed)
    Abstract [en]

    The eutrophication problem has drawn attention to nutrient leaching from arable land in southern Sweden, and further understanding of spatial and temporal variability is needed in order to develop decision-making tools. Thus, the influence of spatial and temporal variables was analysed statistically using empirical time series of different nutrient species from 35 well-documented catchments (2-35 km(2)), which have been monitored for an average of 5 years. In the spatial analysis several significant correlations between winter median concentrations and catchment characteristics were found. The strongest correlation was found between inorganic nitrogen and land use, while concentrations of different phosphorus species were highly correlated to soil texture. Multiple linear regression models gave satisfactory results for prediction of median winter concentrations in unmeasured catchments, especially for inorganic nitrogen and phosphate. In the analysis of temporal variability within catchments, internal variables from a dynamic hydrological model (HBV) were linked to concentration fluxes. It was found that phosphorus and inorganic nitrogen concentrations were elevated during flow increase at low-Bow conditions, while they were diluted as the wetness in the catchment increased. During unmonitored periods regression models were successful in predicting temporal variability of total phosphorus, phosphate and inorganic nitrogen, while organic nitrogen and particulate phosphorus could not be predicted with this approach. Dividing the data into different flow categories did not improve the prediction of nutrient concentration dynamics. The results and literature review presented, confirm parts of the present HBV-W model approach and will be useful for further development of nutrient routines linked to dynamic hydrological models. (C) 2000 Elsevier Science B.V. All rights reserved.

  • 8.
    Bejarano, Maria Dolores
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Sordo-Ward, Alvaro
    Alonso, Carlos
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Characterizing effects of hydropower plants on sub-daily flow regimes2017In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 550, p. 186-200Article in journal (Refereed)
    Abstract [en]

    A characterization of short-term changes in river flow is essential for understanding the ecological effects of hydropower plants, which operate by turning the turbines on or off to generate electricity following variations in the market demand (i.e., hydropeaking). The goal of our study was to develop an approach for characterizing the effects of hydropower plant operations on within-day flow regimes across multiple dams and rivers. For this aim we first defined ecologically meaningful metrics that provide a full representation of the flow regime at short time scales from free-flowing rivers and rivers exposed to hydropeaking. We then defined metrics that enable quantification of the deviation of the altered short-term flow regime variables from those of the unaltered state. The approach was successfully tested in two rivers in northern Sweden, one free-flowing and another regulated by cascades of hydropower plants, which were additionally classified based on their impact on short-term flows in sites of similar management. The largest differences between study sites corresponded to metrics describing sub-daily flow magnitudes such as amplitude (i.e., difference between the highest and the lowest hourly flows) and rates (i.e., rise and fall rates of hourly flows). They were closely followed by frequency-related metrics accounting for the numbers of within-day hourly flow patterns (i.e., rises, falls and periods of stability of hourly flows). In comparison, between-site differences for the duration-related metrics were smallest. In general, hydropeaking resulted in higher within-day flow amplitudes and rates and more but shorter periods of a similar hourly flow patterns per day. The impacted flow feature and the characteristics of the impact (i.e., intensity and whether the impact increases or decreases whatever is being described by the metric) varied with season. Our approach is useful for catchment management planning, defining environmental flow targets, prioritizing river restoration or dam reoperation efforts and contributing information for relicensing hydropower dams. 

  • 9. Bengtsson, L
    et al.
    Bendz, D
    Hogland, William
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Rosquist, H
    Åkesson, M
    Water balance for landfills of different age1994In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 158, no 3-4, p. 203-217Article in journal (Refereed)
    Abstract [en]

    Water-related processes in landfills are discussed with emphasis on internal processes such as field capacity, moisture variation in time and space, and macropore flow. Runoff production and evaporation from landfills in Sweden of different age are investigated. It is clarified in what ways and for how long a closed municipal landfill differs from an ordinary land area from a hydrological point of view. 

  • 10.
    Berg, Peter
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Feldmann, H.
    Panitz, H. -J
    Bias correction of high resolution regional climate model data2012In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 448, p. 80-92Article in journal (Refereed)
    Abstract [en]

    Bias correction of varying complexity - from simple scaling and additive corrections to more advanced histogram equalisation (HE) corrections - is applied to high resolution (7 km) regional climate model (RCM) simulations. The aim of the study is to compare different methods that are easily implemented and applied to the data, and to assess the applicability and impact of the bias correction depending on the type of bias. The model bias is determined by comparison to a new gridded high resolution (1 km) data set of temperature and precipitation, which is also used as reference for the corrections. The performance of the different methods depends on the type of bias of the model, and on the investigated statistic. Whereas simpler methods correct the first moment of the distributions, they can have adverse effects on higher moments. The HE method corrects also higher moments, but approximations of the transfer function are necessary when applying the method to other data than the calibration data. Here, an empirical transfer function with linear fits to the tails is compared to a version where the complete function is approximated by a linear fit. The latter is thus limited to corrections of the first and second moments of the distribution. While making the transfer function more generally applicable, these approximations also limit the performance of the HE method. For the current model biases, the linear approximation is found suitable for precipitation, but for temperature it is not able to correct the whole distribution. The lower performance of the linear correction is most pronounced in summer, and is likely due to a difference in skewness between the model and observational data. Further limitations of the HE method are due to the need for long time series in order to have robust distributions for calculating the transfer function. Theoretical approximations of the required length of the calibration period were performed by using different sampling sizes drawn from a known distribution. The excerise show that about 30 year long time series are needed to have reasonable accuracy for the estimation of variance, when also corrections of the annual cycle is required. (C) 2012 Elsevier B.V. All rights reserved.

  • 11.
    Berg, Peter
    et al.
    SMHI, Research Department, Hydrology.
    Norin, Lars
    SMHI, Research Department, Atmospheric remote sensing.
    Olsson, Jonas
    SMHI, Research Department, Hydrology.
    Creation of a high resolution precipitation data set by merging gridded gauge data and radar observations for Sweden2016In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 541, p. 6-13Article in journal (Refereed)
  • 12.
    Bergström, Sten
    et al.
    SMHI, Research Department, Hydrology.
    Graham, Phil
    SMHI, Research Department, Climate research - Rossby Centre.
    Abstract to "On the scale problem in hydrological modelling" [Journal of Hydrology 211 (1998) 253-265]1999In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 217, no 3-4, p. 284-284Article in journal (Refereed)
  • 13.
    Bergström, Sten
    et al.
    SMHI, Research Department, Hydrology.
    Graham, Phil
    SMHI, Research Department, Climate research - Rossby Centre.
    On the scale problem in hydrological modelling1998In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 211, no 1-4, p. 253-265Article in journal (Refereed)
    Abstract [en]

    The problem of scales and particularly the modelling of macro or continental scale catchments in hydrology is addressed. It is concluded that the magnitude of the scale problem is related to the specific hydrologic problem to be solved and to the scientific approach and perspective of the modeller. A distributed modelling approach, based on variability parameters, is suggested for modelling of soil moisture dynamics and runoff generation. It is shown that the parameters of such an approach are relatively stable over a wide range of scales. An example of the application of a standard Version of the Swedish HBV hydrological model to the continental scale catchment of the Baltic Sea is shown and its usefulness is discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.

  • 14.
    Beven, Keith
    Institute of Environmental & Natural Sciences, Lancaster University, UK.
    A manifesto for the equifinality thesis2006In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 320, no 1-2, p. 18-36Article in journal (Refereed)
    Abstract [en]

    This essay discusses some of the issues involved in the identification and predictions of hydrological models given some calibration data. The reasons for the incompleteness of traditional calibration methods are discussed. The argument is made that the potential for multiple acceptable models as representations of hydrological and other environmental systems (the equifinality thesis) should be given more serious consideration than hitherto. It proposes some techniques for an extended GLUE methodology to make it more rigorous and outlines some of the research issues still to be resolved. (c) 2005 Elsevier Ltd All rights reserved.

  • 15.
    Beven, Keith J
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Smith, P.
    Freer, J.
    Comment on “Hydrological forecasting uncertainty assessment: Incoherence of the GLUE methodology” by Pietro Mantovan and Ezio Todini2007In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 338, no 3-4, p. 315-318Article in journal (Refereed)
    Abstract [en]

    This comment is a response to the criticisms of the GLUE methodology by [Mantovan, P., Todini, E., 2006. Hydrological forecasting uncertainty assessment: Incoherence of the GLUE methodology, J. Hydrology, 2006]. In this comment it is shown that the formal Bayesian identification of models is a special case of GLUE that can be used where the modeller is prepared to make very strong assumptions about the nature of the modelling errors. For the hypothetical study of Mantovan and Todini, exact assumptions were assumed known for the formal Bayesian identification, but were then ignored in the application of GLUE to the same data. We show that a more reasonable application of GLUE to this problem using similar prior knowledge shows that gives equally coherent results to the formal Bayes identification. In real applications, subject to input and model structural error it is suggested that the coherency condition of MT06 cannot hold at the single observation level and that the choice of a formal Bayesian likelihood function may then be incoherent. In these (more interesting) cases, GLUE can be coherent in the application of likelihood measures based on blocks of data, but different choices of measures and blocks effectively represent different beliefs about the information content of data in real applications with input and model structural errors.

  • 16.
    Beven, Keith
    et al.
    Environmental Science/Lancaster Environment Centre, Lancaster University, Lancaster UK.
    Smith, Paul J.
    Environmental Science/Lancaster Environment Centre, Lancaster University, Lancaster UK.
    Freer, Jim E.
    Environmental Science/Lancaster Environment Centre, Lancaster University, Lancaster UK.
    So just why would a modeller choose to be incoherent?2008In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 354, no 1-4, p. 15-32Article in journal (Refereed)
    Abstract [en]

    This article provides an extended response to the criticisms of the GLUE methodology by Mantovan and Todini [Mantovan, P., Todini, E., 2006. Hydrological forecasting uncertainty assessment: incoherence of the GLUE methodology. J. Hydrol. 330, 368-381]. It is shown that the formal Bayesian identification of models is a special case of GLUE that can be used where the modeller is prepared to make very strong assumptions about the nature of the modelling errors. Under such assumptions, GLUE can be coherent in the sense of Manotvan and Todini. In real applications, however, with multiple sources of uncertainty including model structural error, their strong definition of coherence is shown to be inapplicable to the extent that the choice of a format likelihood function based on a simple error structure may be an incoherent choice. It is demonstrated by some relatively minor modifications of their hypothetical example that misspecification of the error model and the non-stationarities associated with the presence of input error and model structural error in the Bayes approach will then produce well-defined but incorrect parameter distributions. This empirical result is quite independent of GLUE, but the flexibility of the GLUE approach may then prove to be an advantage in providing more coherent and robust choices of model evaluation in these cases and, by analogy, in other non-ideal cases for real applications. At the current time it is difficult to make a reasoned choice between methods of uncertainty estimation for real applications because of a lack of understanding of the real information content of data in conditioning models.

  • 17.
    Bhattacharya, Prosun
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Naidu, Ravi
    Polya, David A.
    Mukherjee, Abhijit
    Bundschuh, Jochen
    Charlet, Laurent
    Arsenic in hydrological processes-Sources, speciation, bioavailability and management2014In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 518, p. 279-283Article in journal (Other academic)
  • 18.
    Blecken, Godecke-Tobias
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Zinger, Yaron
    Facility for Advancing Water Biofiltration, Department of Civil Engineering, Monash University.
    Deletic, Ana
    Facility for Advancing Water Biofiltration, Department of Civil Engineering, Monash University.
    Fletcher, Tim
    Facility for Advancing Water Biofiltration, Department of Civil Engineering, Monash University.
    Hedström, Annelie
    Viklander, Maria
    Laboratory study on stormwater biofiltration: nutrient and sediment removal in cold temperatures2010In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 394, no 3-4, p. 507-514Article in journal (Refereed)
    Abstract [en]

    Stormwater biofilters have the ability to remove nutrients from stormwater. Reliable pollutant removal during the cold season is particularly important due to the comparably high contamination levels. However, the removal performance might be negatively affected by low temperatures. A biofilter column study was conducted in thermostat-controlled climate rooms (at 2, 7 and 20 °C) to investigate the effect of low temperatures on nutrient removal. Phosphorus and suspended solids removal were significantly correlated and consistently very high (typically in excess of 90 and 95%, respectively, at all temperatures). This is important for the successful implementation of biofilters in cold climates since phosphorus is commonly of principal concern, often being the limiting factor for eutrophication in freshwater ecosystems. Unfortunately, nitrogen removal was poor and leaching was shown, which increased with temperature. The increasing nitrate-nitrogen production rates with temperature were well described by the Arrhenius relationship with temperature coefficients Q10 in the range which is typically used to describe temperature effects on nitrification. Thus, temperature effects have to be considered when nitrogen removal is targeted and the biofilter might be exposed to cold temperatures.

  • 19.
    Bodin, Hristina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, The Institute of Technology.
    Persson, Jesper
    Swedish University of Agriculture Science, Sweden .
    Englund, Jan-Eric
    Swedish University of Agriculture Science, Sweden .
    Milberg, Per
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, The Institute of Technology.
    Influence of residence time analyses on estimates of wetland hydraulics and pollutant removal2013In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 501, p. 1-12Article in journal (Refereed)
    Abstract [en]

    Hydraulic tracer studies are frequently used to estimate wetland residence time distributions (RTDs) and ultimately pollutant removal. However, there is no consensus on how to analyse these data. We set out to (i) review the different methods used and (ii) use simulations to explore how the data analysis method influences the quantification of wetland hydraulics and pollutant removal. The results showed that the method influences the water dispersion (N) most strongly and the removal least strongly. The influence increased with decreasing effective volume ratio (e) and N, indicating a greater effect of the method in wetlands with low effective volume and high dispersion. The method of moments with RTD truncation at 3 times the theoretical residence time (t(n)) and tracer background concentration produced the most dissimilar parameters. The most similar parameters values were those for gamma modelling and the method of moments with RTD truncation at tracer background concentration. For correct removal estimates, e was more important than N. However, the results from the literature review and simulations indicated that previously published articles may contain overestimated e and underestimated N values as a result of frequent RTD truncations at 3t(n), when using the method of moments. As a result, the removal rates may also be overestimated by as much as 14% compared to other truncation methods or modelling. Thus, it is recommended that wetland hydraulic tracer studies should use the same method, specifically, RTD truncation. We conclude that the choice of tracer data analysis method can greatly influence the quantifications of wetland hydraulics and removal rate.

  • 20.
    Bodin, Hristina
    et al.
    Linköping University.
    Persson, Jesper
    SLU, Alnarp.
    Englund, Jan-Erik
    SLU, Alnarp.
    Milberg, Per
    Linköping University.
    Influence of residence time analyses on estimates of wetland hydraulics and pollutant removal2013In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 501, p. 1-12Article in journal (Refereed)
    Abstract [en]

    Hydraulic tracer studies are frequently used to estimate wetland residence time distributions (RTDs) and ultimately pollutant removal. However, there is no consensus on how to analyse these data. We set out to (i) review the different methods used and (ii) use simulations to explore how the data analysis method influences the quantification of wetland hydraulics and pollutant removal. The results showed that the method influences the water dispersion (N) most strongly and the removal least strongly. The influence increased with decreasing effective volume ratio (e) and N, indicating a greater effect of the method in wetlands with low effective volume and high dispersion. The method of moments with RTD truncation at 3 times the theoretical residence time (tn) and tracer background concentration produced the most dissimilar parameters. The most similar parameters values were those for gamma modelling and the method of moments with RTD truncation at tracer background concentration. For correct removal estimates, e was more important than N. However, the results from the literature review and simulations indicated that previously published articles may contain overestimated e and underestimated N values as a result of frequent RTD truncations at 3tn when using the method of moments. As a result, the removal rates may also be overestimated by as much as 14% compared to other truncation methods or modelling. Thus, it is recommended that wetland hydraulic tracer studies should use the same method, specifically, RTD truncation. We conclude that the choice of tracer data analysis method can greatly influence the quantifications of wetland hydraulics and removal rate.

  • 21. Breinl, Korbinian
    et al.
    Turkington, Thea
    Stowasser, Markus
    Stochastic generation of multi-site daily precipitation for applications in risk management2013In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 498, p. 23-35Article in journal (Refereed)
    Abstract [en]

    Unlike single-site precipitation generators, multi-site precipitation generators make it possible to reproduce the space–time variation of precipitation at several sites. The extension of single-site approaches to multiple sites is a challenging task, and has led to a large variety of different model philosophies for multi-site models. This paper presents an alternative semi-parametric multi-site model for daily precipitation that is straightforward and easy to implement. Multi-site precipitation occurrences are simulated with a univariate Markov process, removing the need for individual Markov models at each site. Precipitation amounts are generated by first resampling observed values, followed by sampling synthetic precipitation amounts from parametric distribution functions. These synthetic precipitation amounts are subsequently reshuffled according to the ranks of the resampled observations in order to maintain important statistical properties of the observation network. The proposed method successfully combines the advantages of non-parametric bootstrapping and parametric modeling techniques. It is applied to two small rain gauge networks in France (Ubaye catchment) and Austria/Germany (Salzach catchment) and is shown to well reproduce the observations. Limitations of the model relate to the bias of the reproduced seasonal standard deviation of precipitation and the underestimation of maximum dry spells. While the lag-1 autocorrelation is well reproduced for precipitation occurrences, it tends to be underestimated for precipitation amounts. The model can generate daily precipitation amounts exceeding the ones in the observations, which can be crucial for risk management related applications. Moreover, the model deals particularly well with the spatial variability of precipitation. Despite its straightforwardness, the new concept makes a good alternative for risk management related studies concerned with producing daily synthetic multi-site precipitation time series.

  • 22.
    Bring, Arvid
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hydro-climatic changes and their monitoring in the Arctic: Observation-model comparisons and prioritization options for monitoring development2013In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 492, p. 273-280Article in journal (Refereed)
    Abstract [en]

    The Arctic undergoes particularly large and rapid hydro-climatic changes, and information on hydrological responses to these changes is crucial to plan for societal adaptation. We investigate hydro-climatic change severity and monitoring in 14 major hydrological basins across the pan-Arctic, in view of different possible strategies for their monitoring prioritization. Results show that the current distribution of monitoring density in these basins is more relevant for so far observed precipitation changes than for observed temperature changes, or for projected future temperature and precipitation changes. Furthermore, present and projected future hot-spots of greatest hydro-climatic change differ spatially, so that major spatial shifts must occur in the future among the different Arctic basins in order for observations and climate model projections to converge with regard to hydro-climatic change severity. Also temporally, observation-model convergence requires that important change direction shifts occur in major Arctic basins, which have currently decreasing precipitation while model projections imply future increasing precipitation within them. Different prioritization options for rational development of hydro-climatic monitoring can be argued for based on the present results. The divergent prioritization options imply a need for an explicit strategy for achieving certain information goals, which must be selected from a larger set of different possible goals based on societal importance.

  • 23.
    Bringfelt, Björn
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    LINDROTH, A
    SYNOPTIC EVAPOTRANSPIRATION MODEL APPLIED TO 2 NORTHERN FORESTS OF DIFFERENT DENSITY1987In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 95, no 3-4, p. 185-201Article in journal (Refereed)
  • 24. Chen, H.
    et al.
    Guo, S.L.
    Xu, Chong-yu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Singh, V.P.
    Historical temporal trends of hydro-climatic variables and runoff response to climate variability and their relevance in water resource management in the Hanjiang basin2007In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 344, no 3-4, p. 171-184Article in journal (Refereed)
    Abstract [en]

    The Danjiangkou reservoir lies in the upper Hanjiang basin and is the source of water for the middle route of the South-to-North Water Diversion Project (SNWDP) in China. Any significant change in the magnitude or timing of runoff from the Danjiangkou reservoir induced by changes in climatic variables would have significant implications for the economic prosperity of the area in the Hanjiang basin as well as for the South-to-North Water Diversion Project. In this paper the following issues are investigated: (1) Temporal trends of annual and seasonal precipitation and temperature from 1951 to 2003 in the Hanjiang basin are analyzed using the Mann–Kendall and the linear regression methods; spatial distributions of precipitation and temperature are interpolated by the inverse distance weighted interpolation method. (2) Temporal trends of runoff, precipitation and temperature from 1951 to 2003 in the Danjiangkou reservoir, an upper stream basin of the Hanjiang River, are further tested. (3) To assess the impact of climate change on water resources and predict the future runoff change in the Danjiangkou reservoir basin, a two-parameter water balance model is used to simulate the hydrological response for the climate change predicted by GCMs for the region for the period of 2021–2050.

    The results indicate that (1) at the α = 0.05 significance level precipitation in the Hanjiang basin has no trend, but the temperature in the same region has significant upward trends in most parts of the Hanjiang basin. (2) The mean annual, spring, and winter runoffs in the Danjiangkou reservoir basin have decreasing trends. (3) The results simulated for the period 2021–2050 show that runoff of the Danjiangkou reservoir would increase in all the seasons, mainly in response to the predicted precipitation increase in the region. Sensitivity analysis shows that a 1 °C and 2 °C increase in temperature would reduce the mean annual runoff to about 3.5% and 7%, respectively. A decrease/increase of the mean monthly precipitation of 20% and 10% would decrease/increase the mean annual runoff to about 30% and 15%, respectively. The results of this study provide a scientific reference not only for assessing the impact of the climate change on water resources and the flood prevention in the Hanjiang basin, but also for dimensioning the middle route of the SNWDP in China.

  • 25. Cheng, Qin-Bo
    et al.
    Chen, Xi
    Xu, Chong-Yu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Reinhardt-Imjela, Christian
    Schulte, Achim
    Improvement and comparison of likelihood functions for model calibration and parameter uncertainty analysis within a Markov chain Monte Carlo scheme2014In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 519, no Part B, p. 2202-2214Article in journal (Refereed)
    Abstract [en]

    Summary In this study, the likelihood functions for uncertainty analysis of hydrological models are compared and improved through the following steps: (1) the equivalent relationship between the Nash–Sutcliffe Efficiency coefficient (NSE) and the likelihood function with Gaussian independent and identically distributed residuals is proved; (2) a new estimation method of the Box–Cox transformation (BC) parameter is developed to improve the effective elimination of the heteroscedasticity of model residuals; and (3) three likelihood functions—NSE, Generalized Error Distribution with BC (BC-GED) and Skew Generalized Error Distribution with BC (BC-SGED)—are applied for SWAT-WB-VSA (Soil and Water Assessment Tool – Water Balance – Variable Source Area) model calibration in the Baocun watershed, Eastern China. Performances of calibrated models are compared using the observed river discharges and groundwater levels. The result shows that the minimum variance constraint can effectively estimate the BC parameter. The form of the likelihood function significantly impacts on the calibrated parameters and the simulated results of high and low flow components. SWAT-WB-VSA with the NSE approach simulates flood well, but baseflow badly owing to the assumption of Gaussian error distribution, where the probability of the large error is low, but the small error around zero approximates equiprobability. By contrast, SWAT-WB-VSA with the BC-GED or BC-SGED approach mimics baseflow well, which is proved in the groundwater level simulation. The assumption of skewness of the error distribution may be unnecessary, because all the results of the BC-SGED approach are nearly the same as those of the BC-GED approach.

  • 26. Choi, H.T.
    et al.
    Beven, Keith J
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Multi-period and Multi-criteria Model Conditioning to Reduce Prediction Uncertainty in Distributed Rainfall-Runoff Modelling within GLUE framework2007In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 332, no 3-4, p. 316-336Article in journal (Refereed)
    Abstract [en]

    A new approach to multi-criteria model evaluation is presented. The approach is consistent with the equifinality thesis and is developed within the Generalised Likelihood Uncertainty Estimation (GLUE) framework. The predictions of Monte Carlo realisations of TOPMODEL parameter sets are evaluated using a number of performance measures calibrated for both global (annual) and seasonal (30 day) periods. The seasonal periods were clustered using a Fuzzy C-means algorithm, into 15 types representing different hydrological conditions. The model shows good performance on a classical efficiency measure at the global level, but no model realizations were found that were behavioural over all multi-period clusters and all performance measures, raising questions about what should be considered as an acceptable model performance. Prediction uncertainties can still be calculated by allowing that different clusters require different parameter sets. Variations in parameter distributions between clusters, as well as examination of where observed discharges depart from model prediction bounds, give some indication of model structure deficiencies.

  • 27.
    Cornelissen, Gerard
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Okkenhaug, Gudny
    Breedveld, Gijsbert D.
    Sorlie, Jan-Erik
    Transport of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in a landfill: A novel equilibrium passive sampler to determine free and total dissolved concentrations in leachate water2009In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 369, no 04-mar, p. 253-259Article in journal (Refereed)
    Abstract [en]

    Equilibrium passive sampling devices consisting of 17-mu m thick polyoxymethylene (POM) were in situ deployed as a novel technique for landfill groundwater leachate water sampling of freely dissolved poly-cyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). POM was deployed in two groundwater leachate wells (flow around 100 m y(-1)) and an effluent leachate tank. The dissipation of >90% of spiked performance reference compounds and comparison between 60 d and 140 d of equilibration confirmed that POM-water equilibrium was reached for all PAHs and most PCBs within 60 d. Comparison of total and freely dissolved concentrations yielded dissolved organic carbon-water distribution ratios that were on average 0.4 log-unit below amorphous organic carbon-water distribution ratios and in accordance with literature values. Particle-bound fractions ranged from 50% (small PAHs) to 99.9% (large PCBs), and were >95% for most compounds. It was concluded that POM-17 equilibrium passive samplers provide a facile method to measure freely dissolved concentrations of PAH and PCB in groundwater leachate, which will yield valuable information on its ecotoxicological risk for aquatic and benthic organisms. 

  • 28.
    Cvetkovic, Vladimir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Fiori, A.
    Dagan, G.
    Tracer travel and residence time distributions in highly heterogeneous aquifers: Coupled effect of flow variability and mass transfer2016In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707Article in journal (Refereed)
    Abstract [en]

    The driving mechanism of tracer transport in aquifers is groundwater flow which is controlled by the heterogeneity of hydraulic properties. We show how hydrodynamics and mass transfer are coupled in a general analytical manner to derive a physically-based (or process-based) residence time distribution for a given integral scale of the hydraulic conductivity; the result can be applied for a broad class of linear mass transfer processes. The derived tracer residence time distribution is a transfer function with parameters to be inferred from combined field and laboratory measurements. It is scalable relative to the correlation length and applicable for an arbitrary statistical distribution of the hydraulic conductivity. Based on the derived residence time distribution, the coefficient of variation and skewness of residence time are illustrated assuming a log-normal hydraulic conductivity field and first-order mass transfer. We show that for a low Damkohler number the coefficient of variation is more strongly influenced by mass transfer than by heterogeneity, whereas skewness is more strongly influenced by heterogeneity.

  • 29.
    Cvetkovic, Vladimir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Soltani, Safeyeh
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Vigouroux, Guillaume
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Global sensitivity analysis of groundwater transport2015In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 531Article in journal (Refereed)
    Abstract [en]

    In this work we address the model and parametric sensitivity of groundwater transport using the Lagrangian-Stochastic Advection-Reaction (LaSAR) methodology. The 'attenuation index' is used as a relevant and convenient measure of the coupled transport mechanisms. The coefficients of variation (CV) for seven uncertain parameters are assumed to be between 0.25 and 3.5, the highest value being for the lower bound of the mass transfer coefficient k0. In almost all cases, the uncertainties in the macro-dispersion (CV = 0.35) and in the mass transfer rate k0 (CV = 3.5) are most significant. The global sensitivity analysis using Sobol and derivative-based indices yield consistent rankings on the significance of different models and/or parameter ranges. The results presented here are generic however the proposed methodology can be easily adapted to specific conditions where uncertainty ranges in models and/or parameters can be estimated from field and/or laboratory measurements.

  • 30.
    Dahlke, Helen E.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Easton, Zachary M.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Walter, M. Todd
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Steenhuis, Tammo S.
    Dissecting the variable source area concept - Subsurface flow pathways and water mixing processes in a hillslope2012In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 420, p. 125-141Article in journal (Refereed)
    Abstract [en]

    This study uses an instrumented (trenched) 0.5 ha hillslope in the southern tier of New York State, USA, to provide new data and insights on how variable source areas and associated flow pathways form and combine to connect rainfall with downstream water flows across a hillslope. Measurements of water fluxes in the trench, upslope water table dynamics, surface and bedrock topography, and isotopic and geochemical tracers have been combined for a four-dimensional (space-time) characterization of subsurface storm flow responses. During events with dry antecedent conditions infiltrating rainwater was found to percolate through a prevailing fragipan layer to deeper soil layers, with much (33-71%) of the total discharge of the hillslope originating from deeper water flow below the fragipan. During storm events with wet antecedent conditions and large rainfall amounts, shallow lateral flow of event and pre-event water above the fragipan occurred and was one magnitude greater than the deeper water flow contribution. Spatial surface and subsurface water quality observations indicate that water from a distance of up to 56 m contributed runoff from the hillslope during storm events. In addition, mobilization of total dissolved phosphorus (TDP) with subsurface flow played a greater role than with overland or near-surface flow. During all events TDP loads were highest in the total discharge during peak flows (8-11.5 kg ha(-1) d(-1)), except during the largest storm event, when TDP concentrations were highly diluted. These results have implications for strategies to protect streams and other downstream water recipients from waterborne nutrient and pollutant loading.

  • 31.
    Dargahi, Bijan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Setegn, Shimelis Gebriye
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Combined 3D Hydrodynamic and Watershed Modelling of Lake Tana, Ethiopia2011In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 398, no 1-2, p. 44-64Article in journal (Refereed)
    Abstract [en]

     The growing high demand for lake Tana water portends a disturbing future. The main objective of this paper is to make a contribution to the development of a sustainable use of the water of Lake Tana. A fully three-dimensional hydrodynamic model was combined with a watershed model and together, these models were successfully validated for the year 2006. The flow structure is characterized by large recirculation and secondary flow regions. Secondary flows are induced by hydrodynamic instabilities occurring at the interfaces of layers with a velocity gradient and the interaction with the irregularities of the bed. The weak stratification process in Lake Tana is characterized by a classic summer profile, which is more pronounced during January-February. Mixing processes in the lake are controlled by wind, the mixing energy induced by both river inflows and the lake outlet, and convective mixing due to the negative buoyancy. An alarming fall of the water levels in Lake Tana was found in response to the planned water withdrawal. The long flushing time (19 months) will not allow a fast decay of contaminated materials released into the lake. The flow structure will not be significantly modified by the planned water withdrawal but the flushing time will decrease. The hydrodynamics of Lake Tana resemble a closed system similar to a shallow reservoir with an overflow type outlet. The implication is that the lake is vulnerable to changes in external conditions and sustainable use of the water resource of the lake will require awareness of this vulnerability. The combined watershed and hydrodynamic models would be effective tools to achieve this awareness. It is also necessary to address the impact of climate change on the fate of the lake. These are all difficult challenges that need to be addressed to safeguard the sensitive eco-system of the area.

  • 32.
    Destouni, Georgia
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Verrot, Lucile
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Screening long-term variability and change of soil moisture in a changing climate2014In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 516, p. 131-139Article in journal (Refereed)
    Abstract [en]

    Soil moisture is an essential component of water variability and change in the landscape. This paper develops a conceptual and analytical framework for linking hydro-climatic change at the surface and soil-groundwater conditions in the subsurface, and quantifying long-term development of soil moisture statistics in a changing climate. Soil moisture is evaluated both in the unsaturated zone and over a fixed soil depth that may also include a variable groundwater table. Long-term variability and change of soil moisture are assessed for a hydro-climatic observation record that extends over the whole 20th century in a major Swedish drainage basin. Frequencies of particularly dry and wet soil moisture events are investigated for different 20-year climatic periods. Results show major increase in the frequency of dry events from the beginning to the end of the 20th century. This indicates increased risk for hydrological and agricultural drought even though the risk for meteorological drought, in terms of precipitation, has decreased in the region. The developed quantification framework can also be used to screen future scenarios of soil moisture change under projected climate change.

  • 33.
    Di Baldassarre, Giuliano
    et al.
    School of Geographical Sciences, University of Bristol, University Road, Bristol BS8 1SS, UK.
    SCHUMANN, G
    BATES, PD
    A technique for the calibration of hydraulic models using uncertain satellite observations of flood extent2009In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 367, no 3-4, p. 276-282Article in journal (Refereed)
    Abstract [en]

    This paper presents a methodology to calibrate hydraulic models using possibility of inundation maps derived from satellite imagery. The study was performed on a river reach of the Lower Dee, UK, where a coarse resolution image (ENVISAT ASAR) and high resolution satellite image (ERS-2 SAR) were acquired at the same time during the December 2006 flood event. Ten different flood extent maps were derived from the two flood images by using five different procedures to process these data. These flood extent maps were used to perform a sensitivity analysis of a simple raster-based inundation model (LISFLOOD-FP). The sensitivity analysis enabled us to investigate the capability of the two different resolution images to calibrate the friction parameters of the flood inundation model. The analysis showed that the optimal parameters of the model depend on the type of satellite image used to evaluate the model as well as on the particular procedure used to derive the flood extent map. Finally, the study developed a novel methodology to calibrate flood inundation models by comparing the model results to a possibility of inundation map obtained by combining the ten different flood extent maps.

  • 34. Doughty, Christine
    et al.
    Tsang, Chin-Fu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Yabuuchi, Satoshi
    Kunimaru, Takanori
    Flowing fluid electric conductivity logging for a deep artesian well in fractured rock with regional flow2013In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 482, p. 1-13Article in journal (Refereed)
    Abstract [en]

    The flowing fluid electric conductivity (FFEC) logging method is a well-logging technique that may be used to estimate flow rate, salinity, transmissivity, and hydraulic head of individual fractures or high-permeability zones intersected by a wellbore. Wellbore fluid is first replaced with fluid of a contrasting electric conductivity, then repeated FEC logging is done while the well is pumped. Zones where fluid flows into the wellbore show peaks in the FEC logs, which may be analyzed to infer inflow rate and salinity of the individual fractures. Conducting the procedure with two or more pumping rates (multi-rate FFEC logging) enables individual fracture transmissivity and hydraulic head to be determined. Here we describe the first application of the multi-rate FFEC logging method to an artesian well, using a 500-m well in fractured rock at Horonobe, Japan. An additional new factor at the site is the presence of regional groundwater flow, which heretofore has only been studied with synthetic data. FFEC logging was conducted for two different pumping rates. Several analysis techniques had to be adapted to account for the artesian nature of the well. The results were subsequently compared with independent salinity measurements and transmissivity and hydraulic head values obtained from packer tests in the same well. Despite non-ideal operating conditions, multi-rate FFEC logging successfully determined flow rate, salinity, and transmissivity of 17 conducting fractures intercepted by the logged section of the borehole, including two fractures with regional groundwater flow. Predictions of hydraulic head were less accurate, a not unexpected result in light of operational problems and the form of the equation for hydraulic head, which involves the difference between two uncertain quantities. This study illustrates the strengths and weaknesses of the multi-rate FFEC logging method applied to artesian wells. In conjunction with previous studies, it demonstrates the usefulness of the method for a broad range of conditions encountered in subsurface fractured rock.

  • 35. Du, Jinkang
    et al.
    Xie, Hua
    Hu, Yujun
    Xu, Youpeng
    Xu, Chong-Yu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Development and testing of a new storm runoff routing approach based on time variant spatially distributed travel time method2009In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 369, no 1-2, p. 44-54Article in journal (Refereed)
    Abstract [en]

    In this study, a GIS based simple and easily performed runoff routing approach based on travel time was developed to simulate storm runoff response process with consideration of spatial and temporal variability of runoff generation and flow routing through hillslope and river network. The watershed was discretized into grid cells, which were then classified into overland cells and channel cells through river network delineation from the DEM by use of GIS. The overland flow travel time of each overland cell was estimated by combining a steady state kinematic wave approximation with Manning’s equation, the channel flow travel time of each channel cell was estimated using Manning’s equation and the steady state continuity equation. The travel time from each grid cell to the watershed outlet is the sum of travel times of cells along the flow path. The direct runoff flow was determined by the sum of the volumetric flow rates from all contributing cells at each respective travel time for all time intervals. The approach was calibrated and verified to simulate eight storm runoff processes of Jiaokou Reservoir watershed, a sub-catchment of the Yongjiang River basin in southeast China using available topography, soil and land use data for the catchment. An average efficiency of 0.88 was obtained for the verification storms. Sensitivity analysis was conducted to investigate the effect of the area threshold of delineating river networks and parameter K relating channel velocity calculation on the predicted hydrograph at the basin outlet. The effects of different levels of grid size on the results were also studied, which showed that good results could be attained with a grid size of less than 200 m in this study. (C) 2009 Elsevier B.V. All rights reserved.

  • 36. Du, Jinkang
    et al.
    Xie, Hua
    Hu, Yujun
    Xu, Youpeng
    Xu, Chong-Yu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Reply to comment on “Development and testing of a new storm runoff routing approach based on time variant spatially distributed travel time method” by Du et al. [Journal of Hydrology 369 (2009) 44-54]2010In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 381, p. 374-376Article in journal (Refereed)
  • 37. Du, Jinkang
    et al.
    Xie, Shunpeng
    Xu, Youpeng.
    Xu, Chong-yu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Singh, Vijay P
    Development and testing of a simple physically-based distributed rainfall-runoff model for storm runoff simulation in humid forested basins2007In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 336, no 3-4, p. 334-346Article in journal (Refereed)
    Abstract [en]

    A distributed rainfall-runoff model was developed to predict storm runoff from humid forested catchments. The model is physically based and takes into account the saturation excess overland flow mechanism and preferential subsurface flow. The watershed is discretized into a number of square grids, which then are classified into overland flow and channel flow elements based on water flow properties. On the overland elements, Infiltration, overland flow and lateral subsurface flow are estimated, while on channel flow elements river flow routing is performed. Lateral subsurface flow is calculated using Darcy’s law and the continuity equation, whereas overland flow and channel flow are modeled using a one dimensional kinematic wave approximation to the St. Venant equations. The model governing equations are solved by an implicit finite difference scheme. While using process-based equations and physically meaningful parameters, the model still maintains a relatively simple structure. Most of the model parameters can be derived from digital elevation models (DEMs), digital soil and land use data, and the remainder of the parameters that are comparatively sensitive can be determined by model calibration. The model is tested using nine storm events in the Jiaokou watershed, a sub-basin of Yongjiang River in Zhejiang Province, China. Of these storms, one storm is used for calibrating the model parameters and the remaining eight storms are used to verify the model. When judged by the model efficiency coefficient (R2), volume conversation index (VCI), absolute error of the time to peak (ΔT), and relative error of the peak flow rate (δPmax), acceptable results are achieved. Sensitivity analysis shows that the model is sensitive to saturated hydraulic conductivity (Ks), Manning’s roughness coefficients (n) and the initial soil moisture content.

  • 38. Falter, Daniela
    et al.
    Schroeter, Kai
    Dung, Nguyen Viet
    Vorogushyn, Sergiy
    Kreibich, Heidi
    Hundecha, Yeshewatesfa
    SMHI, Research Department, Hydrology.
    Apel, Heiko
    Merz, Bruno
    Spatially coherent flood risk assessment based on long-term continuous simulation with a coupled model chain2015In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 524, p. 182-193Article in journal (Refereed)
    Abstract [en]

    A novel approach for assessing flood risk in river catchments in a spatially consistent way is presented. The approach is based on a set of coupled models representing the complete flood risk chain, including a multisite, multivariate weather generator, a hydrological model, a coupled 1D-2D hydrodynamic model and a flood loss model. The approach is exemplarily developed for the meso-scale Mulde catchment in Germany. 10,000 years of meteorological fields at daily resolution are generated and used as input to the subsequent models, yielding 10,000 years of spatially consistent river discharge series, inundation patterns and damage values. This allows estimating flood risk directly from the simulated damage. The benefits of the presented approach are: (1) in contrast to traditional flood risk assessments, where homogenous return periods are assumed for the entire catchment, the approach delivers spatially heterogeneous patterns of precipitation, discharge, inundation and damage patterns which respect the spatial correlations of the different processes and their spatial interactions. (2) Catchment and floodplain processes are represented in a holistic way, since the complete chain of flood processes is represented by the coupled models. For instance, the effects of spatially varying antecedent catchment conditions on flood hydrographs are implicitly taken into account. (3) Flood risk is directly derived from damage yielding a more realistic representation of flood risk. Traditionally, the probability of discharge is used as proxy for the probability of damage. However, non-linearities and threshold behaviour along the flood risk chain contribute to substantial variability between damage probabilities and corresponding discharge probabilities. (C) 2015 Elsevier B.V. All rights reserved.

  • 39.
    Fischer, Benjamin M. C.
    et al.
    Univ Zurich, Dept Geog, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    van Meerveld, H. J. (Ilja)
    Univ Zurich, Dept Geog, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Seibert, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Univ Zurich, Dept Geog, Winterthurerstr 190, CH-8057 Zurich, Switzerland.
    Spatial variability in the isotopic composition of rainfall in a small headwater catchment and its effect on hydrograph separation2017In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 547, p. 755-769Article in journal (Refereed)
    Abstract [en]

    Isotope hydrograph separation (IHS) is a valuable tool to study runoff generation processes. To perform an IHS, samples of baseflow (pre-event water) and streamflow are taken at the catchment outlet. For rainfall (event water) either a bulk sample is collected or it is sampled sequentially during the event. For small headwater catchment studies, event water samples are usually taken at only one sampling location in or near the catchment because the spatial variability in the isotopic composition of rainfall is assumed to be small. However, few studies have tested this assumption. In this study, we investigated the spatiotemporal variability in the isotopic composition of rainfall and its effects on IHS results using detailed measurements from a small pre-alpine headwater catchment in Switzerland. Rainfall was sampled sequentially at eight locations across the 4.3 km(2) Zwackentobel catchment and stream water was collected in three subcatchments (0.15, 0.23, and 0.70 km(2)) during ten events. The spatial variability in rainfall amount, average and maximum rainfall intensity and the isotopic composition of rainfall was different for each event. There was no significant relation between the isotopic composition of rainfall and total rainfall amount, rainfall intensity or elevation. For eight of the ten studied events the temporal variability in the isotopic composition of rainfall was larger than the spatial variability in the rainfall isotopic composition. The isotope hydrograph separation results, using only one rain sampler, varied considerably depending on which rain sampler was used to represent the isotopic composition of event water. The calculated minimum pre-event water contributions differed up to 60%. The differences were particularly large for events with a large spatial variability in the isotopic composition of rainfall and a small difference between the event and pre-event water isotopic composition. Our results demonstrate that even in small catchments the spatial variability in the rainfall isotopic composition can be significant and has to be considered for IHS studies. Using data from only one rain sampler can result in significant errors in the estimated pre-event water contributions to streamflow.

  • 40.
    Frampton, Andrew
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Painter, Scott
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Non-isothermal, three-phase simulations of near-surface flows in a model permafrost system under seasonal variability and climate change2011In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 403, no 3-4, p. 352-359Article in journal (Refereed)
    Abstract [en]

    Permafrost responses to a changing climate can affect hydrological and biogeochemical cycling, ecosystems and climate feedbacks. We have simulated a model permafrost system in the temperature range associated with discontinuous permafrost focusing on interactions between permafrost and hydrology using a non-isothermal, three-phase model of water migration coupled to heat transport in partially frozen porous media. We explore the subsurface hydraulic property controls on the formation and dynamics of permafrost, and how this impacts seasonal variability of subsurface runoff to surface waters. For all subsurface conditions considered, the main common hydrological signal of permafrost degradation in a warming trend is decreasing seasonal variability of water flow. This is due to deeper and longer flow pathways with increasing lag times from infiltration or thawing through subsurface flow to surface water discharge. These results show how physically based numerical modelling can be used to quantitatively and qualitatively improve the understanding of how permafrost thawing relates to, and may be detected in, hydrological data. This is advantageous since hydrological data is considerably easier to obtain, may be available in longer time series, and generally reflects larger-scale conditions than direct permafrost observations.

  • 41. Frech, Michael
    et al.
    Samuelsson, Patrick
    Stockholm University, Faculty of Science, Department of Meteorology .
    Tjernström, Michael
    Stockholm University, Faculty of Science, Department of Meteorology .
    Jochum, Anne
    Regional surface fluxes over the NOPEX area1998In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 212-213, p. 155-171Article in journal (Refereed)
  • 42.
    Galfi, Helen
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Österlund, Helene
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Marsalek, Jiri
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Indicator bacteria and associated water quality constituents in stormwater and snowmelt from four urban catchments2016In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 539, p. 125-140Article in journal (Refereed)
    Abstract [en]

    SummaryFour indicator bacteria were measured in association with physico-chemical constituents and selected inorganics during rainfall, baseflow and snowmelt periods in storm sewers of four urban catchments in a northern Swedish city. The variation patterns of coliforms, E. coli, enterococci and C. perfringens concentrations were assessed in manually collected grab samples together with those of phosphorus, nitrogen, solids, and readings of pH, turbidity, water conductivity, temperature and flow rates to examine whether these constituents with variation patterns similar to those of indicator bacteria, and to exclude the constituents with less similarity. In the reduced data set, the similarities were quantified by the clustering correlation analysis. Finally, the positive/negative relationships found between indicator bacteria and the identified associated constituent groups were described by multilinear regressions. In the order of decreasing concentrations, coliforms, E. coli and enterococci were found in the highest mean concentrations during both rainfall and snowmelt generated runoff. Compared to dry weather baseflow, concentrations of these three indicators in stormwater were 10 (snowmelt runoff) to 102 (rain runoff) times higher. C. perfringens mean concentrations were practically constant regardless of the season and catchment. The type and number of variables associated with bacteria depended on the degree of catchment development and the inherent complexity of bacteria sources. The list of variables associated with bacteria included the flow rate, solids with associated inorganics (Fe and Al) and phosphorus, indicating similar sources of constituents regardless of the season. On the other hand, bacteria were associated with water temperature only during rain periods, and somewhat important associations of bacteria with nitrogen and pH were found during the periods of snowmelt. Most of the associated constituents were positively correlated with bacteria responses, but conductivity, with two associated inorganics (Si and Sr), was mostly negatively correlated in all the catchments. Although the study findings do not indicate any distinct surrogates to indicator bacteria, the inclusion of the above identified constituents (flow rate, solids and total phosphorus for all seasons, water temperature for rainfall runoff, and total nitrogen and pH for snowmelt only) in sanitary surveys of northern climate urban catchments would provide additional insight into indicator bacteria sources and their modelling.

  • 43.
    Gavric, Snezana
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Larm, Thomas
    StormTac corporation, Stockholm, Sweden.
    Österlund, Helene
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Marsalek, Jiri
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Wahlsten, Anna
    StormTac corporation, Stockholm, Sweden.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Measurement and conceptual modelling of retention of metals (Cu, Pb, Zn) in soils of three grass swales2019In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 574, p. 1053-1061Article in journal (Refereed)
    Abstract [en]

    Grass swales are important elements of the urban green infrastructure that convey and attenuate urban runoff and improve its quality mostly through stormwater infiltration into, and retention of conveyed pollutants by, swale soils. The retention of metals by grass swales was addressed in this study investigating the enrichment of swale soils by three common traffic-related metals: Cu, Pb and Zn. Three swales of various characteristics (L1, L2, L3) were selected for study and their soils were sampled by coring the top 30 cm and dividing the cores into 5 cm thick layers. Cumulative metal burdens were compared to those modelled by the proprietary StormTac Web model, which estimates annual loads of specific constituents for the given land uses and stormwater treatment. The comparisons of measured (MBm) and simulated (MBs) metal burdens retained by swales showed that the measured values exceed the simulated ones, as described by average ratios MBs/MBm = 0.64, 0.50 and 0.59, for swales L1, L2 and L3, respectively. The measured burdens were calculated after subtracting the native soil metal concentrations, assumed equal to those found in the deepest sampled layer, 25–30 cm below the surface. The results suggest the feasibility of assessing performance of grass swales by modelling metal (Cu, Pb, Zn) retention by swales, however for older facilities considered for rehabilitation, the simulated results should be supplemented by soil chemistry sampling.

  • 44.
    Gebrehiwot, Solomon Gebreyohannis
    et al.
    Justus Liebig Univ Giessen, Inst Landscape Ecol & Resources Management, Res Ctr BioSyst Land Use & Nutr iPZ, Heinrich Buff Ring 26, D-35392 Giessen, Germany;Addis Ababa Univ, Ethiopian Inst Water Resources, POB 150641, Addis Ababa, Ethiopia.
    Di Baldassarre, Giuliano
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. CNDS, Ctr Nat Hazards & Disaster Sci, Uppsala, Sweden.
    Bishop, Kevin
    Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, S-75007 Uppsala, Sweden.
    Halldin, Sven
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Karlstad Univ, CCS, SE-65188 Karlstad, Sweden.
    Breuer, Lutz
    Justus Liebig Univ Giessen, Inst Landscape Ecol & Resources Management, Res Ctr BioSyst Land Use & Nutr iPZ, Heinrich Buff Ring 26, D-35392 Giessen, Germany;Justus Liebig Univ Giessen, Ctr Int Dev & Environm Res ZEU, Senckenbergstr 3, D-35390 Giessen, Germany.
    Is observation uncertainty masking the signal of land use change impacts on hydrology?2019In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 570, p. 393-400Article in journal (Refereed)
    Abstract [en]

    Analysis of hydrological impacts of land use change raises questions about whether, and how much, such impacts are misrepresented because of errors in river flow observations. In this paper, land use change impacts (represented by changes in watershed storage) and different ranges of discharge measurement error are compared to assess how errors in discharge measurement can potentially mask a land use change impact. Using a watershed from the Ethiopian highlands to exemplify this, we simulated five different levels of land use change impacts with five levels of watershed storage reductions (from 10% to 50% change) and the associated time series of runoff. Different levels of observation error were then introduced into these artificial time series. Comparison was made between every pair, i.e. a time series derived from a certain level of land use change (storage reduction) versus a time series corresponding to a given level of observation error, using a step-change t-test. Significant step-changes between pairs define the detectability of land use change impact. The analysis was made for the entire 30-year time series as well as for the most extreme annual weather conditions. The results showed that for the average year and wettest year, 75% or more error in observed discharge masks the maximum simulated land use change impact on hydrology. In dry years, a 50% error in discharge is enough to mask the same impact. Knowing (and improving) the level of data quality contributes to a better understanding of hydrological uncertainties and improves the precision in assessing land use change impacts. Both of these are essential elements in water resources development planning.

  • 45.
    Gebrehiwot, Solomon Gebreyohannis
    et al.
    Justus Liebig University Giessen, Germany; Addis Ababa University, Ethiopia.
    Di Baldassarre, Giuliano
    Uppsala University; Centre of Natural Hazards and Disaster Science, Uppsala.
    Bishop, Kevin
    Swedish University of Agricultural Sciences, Uppsala,.
    Halldin, Sven
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Breuer, Lutz
    Justus Liebig University Giessen, Germany.
    Is observation uncertainty masking the signal of land use change impacts on hydrology?2019In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 570, p. 393-400Article in journal (Refereed)
    Abstract [en]

    Analysis of hydrological impacts of land use change raises questions about whether, and how much, such impacts are misrepresented because of errors in river flow observations. In this paper, land use change impacts (represented by changes in watershed storage) and different ranges of discharge measurement error are compared to assess how errors in discharge measurement can potentially mask a land use change impact. Using a watershed from the Ethiopian highlands to exemplify this, we simulated five different levels of land use change impacts with five levels of watershed storage reductions (from 10% to 50% change) and the associated time series of runoff. Different levels of observation error were then introduced into these artificial time series. Comparison was made between every pair, i.e. a time series derived from a certain level of land use change (storage reduction) versus a time series corresponding to a given level of observation error, using a step-change t-test. Significant step-changes between pairs define the detectability of land use change impact. The analysis was made for the entire 30-year time series as well as for the most extreme annual weather conditions. The results showed that for the average year and wettest year, 75% or more error in observed discharge masks the maximum simulated land use change impact on hydrology. In dry years, a 50% error in discharge is enough to mask the same impact. Knowing (and improving) the level of data quality contributes to a better understanding of hydrological uncertainties and improves the precision in assessing land use change impacts. Both of these are essential elements in water resources development planning.

  • 46.
    Ghosh, Devanita
    et al.
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences. Laboratory of Integrative Taxonomy and Molecular Ecology, Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India.
    Routh, Joyanto
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Bhadury, Punyasloke
    Laboratory of Integrative Taxonomy and Molecular Ecology, Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India.
    Characterization and microbial utilization of dissolved lipid organic fraction in arsenic impacted aquifers (India)2015In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 527, p. 221-233Article in journal (Refereed)
    Abstract [en]

    The coupled role of organic matter (OM) and microbial activity is widely acknowledged in arsenic (As) biogeochemical cycling in sedimentary environments. However, little is known about OM characteristics particularly the dissolved fraction in the Bengal Delta Plain aquifers – one of the worst As impacted regions in the world. Ongoing investigations in As-rich aquifers in Nadia district (West Bengal, India) indicate presence of arsenite As(III) oxidizing bacterial communities in the Grey Sand Aquifers (GSA), but absent in Brown Sand Aquifers (BSA). In this study, we investigate the key differences in dissolved organic carbon (DOC) characteristics and its relationship with differences in elemental concentrations, distribution of biomarkers, and utilization of DOC by in situ microbial communities in BSA and GSA. We demonstrate a new approach using ENVI™ C-18 DSK discs to pre-concentrate DOC from large volumes of water, and further extract the OM and separate it into different lipid fractions using the solid phase extraction technique. The aquifers show marked heterogeneity in terms of their DOC characteristics and elemental profiles irrespective of their grey or brown color. DOC indicates variable inputs of terrestrial derived OM sources, and OM derived from decomposition and/or microbial cellular components. DOC in the aquifers consist of predominantly n-alkanoic acids (∌80%) followed by n-alkanes and n-alcohols. The GSAs indicate high iron (Fe) and manganese (Mn) concentrations, and presence of mature petroleum derived hydrocarbons in DOC. BSA has comparatively lower concentrations of Fe and Mn, and shows absence of mature hydrocarbons in DOC. Experiments in presence of indigenous bacteria from groundwater with DOC lipid extracts as the sole carbon source indicate higher growth in the GSA samples implying preferential use of DOC. The potential availability of DOC in these aquifers can influence the community composition of indigenous heterotrophic microbial flora, which in turn can affect elemental cycles including that of As.

  • 47.
    Girons Lopez, Marc
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Seibert, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Department of Geography, University of Zurich, Irchel Winterthurerstr 190, 8057 Zurich, Switzerland.
    Influence of Hydro-Meteorological Data Spatial Aggregation on Streamflow Modelling2016In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 541, p. 1212-1220Article in journal (Refereed)
    Abstract [en]

    Data availability is important for virtually any purpose in hydrology. While some parts of the world continue to be under-monitored, other areas are experiencing an increased availability of high-resolution data. The use of the highest available resolution has always been preferred and many efforts have been made to maximize the information content of data and thus improve its predictive power and reduce the costs of maintenance of hydrometric sensor networks. In the light of ever-increasing data resolution, however, it is important to assess the added value of using the highest resolution available. In this study we present an assessment of the relative importance of hydro-meteorological data resolution for hydrological modelling. We used a case study with high-resolution data availability to investigate the influence of using models calibrated with different levels of spatially aggregated meteorological input data to estimate streamflow for different periods and at different locations. We found site specific variations, but model parameterizations calibrated using sub-catchment specific meteorological input data tended to produce better streamflow estimates, with model efficiency values being up to 0.35 efficiency units higher than those calibrated with catchment averaged meteorological data. We also found that basin characteristics other than catchment area have little effect on the performance of model parameterizations applied in different locations than the calibration site. Finally, we found that using an increased number of discharge data locations has a larger impact on model calibration efficiency than using spatially specific meteorological data. The results of this study contribute to improve the knowledge on assessing data needs for water management in terms of adequate data type and level of spatial aggregation.

  • 48.
    Gong, L
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Widen-Nilsson, E
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Halldin, S
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Xu, C.-Y.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Large-scale runoff routing with an aggregated network-response function2009In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 368, no 1-4, p. 237-250Article in journal (Refereed)
    Abstract [en]

    The accuracy of runoff routing for global water-balance models and land-surface schemes is limited by the low spatial resolution of flow networks. Many such networks have been developed for specific models at specific spatial resolutions. However, although low-resolution networks can be derived by up-scaling algorithms from high-resolution datasets, such low-resolution networks are inherently incoherent, and slight differences in their spatial resolution can cause significant deviations in routing dynamics. By neglecting convective delay, storage-based routing algorithms produce artificially early arriving peaks on large scales. A theoretical comparison between a diffusion-wave-routing algorithm and linear-reservoir-routing (LRR) algorithm on a 30-km cell demonstrated that the commonly used LRR method consistently underestimates the travel time through the cells. A new aggregated network-response-function (NRF) routing algorithm was proposed in this study and evaluated against a conventional flow-net-based cell-to-cell LRR algorithm. The evaluation was done for the 25,325 km(2) Dongjiang (East River) basin, a tributary to the Pearl River in southern China well equipped with hydrological and meteorological stations. The NRF method transfers high-resolution delay dynamics, instead of networks, to any lower spatial resolution where runoff is generated. It preserves, over all scales, the spatially distributed time-delay information in the 1-km HYDRO1k flow network in the form of simple cell-response functions for any low-resolution grid. The NRF routing was shown to be scale independent for latitude-longitude resolutions ranging from 5’ to 1 degrees. This scale independency allowed a study of input heterogeneity on modelled discharge modelled with a daily version of the WASMOD-M water-balance model. The model efficiency of WASMOD-M-generated daily discharge at the Boluo gauging station in the Dongjiang basin in south China was constantly high (0.89) within the whole range of resolutions when routed by the NRF algorithm. The performance dropped sharply for decreasing resolution when runoff was routed with the LRR method. The three WASMOD-M parameters were scale independent in combination with NRF, but not with LRR, and the same parameter values gave equally good results at all spatial resolutions. The effect of spatial resolution on the routing delay was much more important than the spatial variability of the climate-input field for scales ranging from 5’ to 1 degrees. The extra information in a distributed versus a uniform climate input could only be used when the NRF method was used to route the runoff. NRF requires more labour than LRR to set up but the model performance is very much higher than the LRR’s once this is done. The NRF method, therefore, provides a significant potential to improve global-scale discharge predictions. (c) 2009 Elsevier B.V. All rights reserved.

  • 49.
    Gong, Lebing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Xu, Chong-yu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Chen, D.
    Halldin, Sven
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Chen, Yongqin David
    Sensitivity of the Penman–Monteith reference evapotranspiration to key climatic variables in the Changjiang (Yangtze River) basin2006In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 329, no 3-4, p. 620-629Article in journal (Refereed)
    Abstract [en]

    Sensitivity analysis is important in understanding the relative importance of climatic variables to the variation of reference evapotranspiration (ETref). In this study, a non-dimensional relative sensitivity coefficient was employed to predict responses of ETref to perturbations of four climatic variables in the Changjiang (Yangtze River) basin. ETref was estimated with the FAO-56 Penman–Monteith equation. A 41-year historical dataset of daily air temperature, wind speed, relative humidity and daily sunshine duration at 150 national meteorological observatory stations was used in the analysis. Results show that the response of ETref can be precisely predicted under perturbation of relative humidity or shortwave radiation by their sensitivity coefficients; the predictive power under perturbations of air temperature and wind speed depended on the magnitude of the perturbation, season and region. The prediction errors were much smaller than the seasonal and regional variation of their sensitivity coefficients. The sensitivity coefficient could also be used to predict the response of ETref to co-perturbation of several variables. The accuracy of the prediction increases from the lower to the upper region. Spatial variations of long-term average monthly and yearly sensitivity coefficients were obtained by interpolation of station estimates. In general, relative humidity was the most sensitive variable, followed by shortwave radiation, air temperature and wind speed. The actual rank of the four climatic variables in terms of their sensitivity varied with season and region. The large spatial variability of the sensitivity coefficients of all the climatic variables in the middle and lower regions of the basin was to a large extent determined by the distinct wind-speed patterns in those two regions.

  • 50.
    Grabs, Thomas
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Laudon, Hjalmar
    Bishop, Kevin
    Modeling spatial patterns of saturated areas: A comparison of the topographic wetness index and a dynamic distributed model2009In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 373, no 1-2, p. 15-23Article in journal (Refereed)
    Abstract [en]

    Topography is often one of the major controls on the spatial pattern of saturated areas, which in turn is akey to understanding much of the variability in soils, hydrological processes, and stream water quality.The topographic wetness index (TWI) has become a widely used tool to describe wetness conditions atthe catchment scale. With this index, however, it is assumed that groundwater gradients always equalsurface gradients. To overcome this limitation, we suggest deriving wetness indices based on simulationsof distributed catchment models. We compared these new indices with the TWI and evaluated the differ-ent indices by their capacity to predict spatial patterns of saturated areas. Results showed that the model-derived wetness indices predicted the spatial distribution of wetlands significantly better than the TWI.These results encourage the use of a dynamic distributed hydrological model to derive wetness indexmaps for hydrological landscape analysis in catchments with topographically driven groundwater tables.

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