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  • 351.
    Wetterhall, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Halldin, Sven
    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.
    Statistical precipitation downscaling in central Sweden with the analogue method2005In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 306, no 1-4, p. 174-190Article in journal (Refereed)
    Abstract [en]

    Most climate predictions show significant consequences globally and regionally, but many of its critical impacts will occur at sub-regional and local scales. Downscaling methods are, thus, needed to assess effects of large-scale atmospheric circulation on local parameters such as precipitation and runoff. This study aims at evaluating the analogue method (AM) as a benchmark method for precipitation downscaling in northern Europe. The predictors used in this study were daily and monthly gridded sea-level pressures from 1960 to 1997 in an area 45-75 degrees N and 30 degrees W-40 degrees E with a resolution of 5 X 5 degrees long-lat. Analogues for daily and monthly precipitation at seven precipitation stations in south-central Sweden were established with two techniques, principal-component analysis (PCA) and the Teweles-Wobus score (TWS). The results showed that AM downscaling on both daily and monthly basis was commonly generally much better than a random baseline but depended on the objective function used for assessment; PCA and TWS produced similar results in most cases but TWS was superior in simulating precipitation duration and intensity. Downscaling was improved when seasonality was included and when the SLP field was confined to those geographical areas that contributed most to precipitation in south-central Sweden.

  • 352.
    Widén, Elin
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science. Air and Water Science.
    Jansson, P-E.
    Espeby, B.
    Olofsson, B.
    Estimations of the water flows to Lake Hällefjärd and Lake Eckarfjärden, Northern Uppland2004Report (Other scientific)
  • 353.
    Widén, Elin
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science. Air and Water Science.
    Xu, Chong-yu
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science. Air and Water Science.
    Halldin, Sven
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science. Air and Water Science.
    Continental-Scale Water-Balance Modelling of the Baltic and Other Large Catchments2004In: Fourth Study Conference on BALTEX, Conference Proceedings, 2004, p. 95-96Conference paper (Refereed)
  • 354.
    Widén, Elin
    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.
    Halldin, Sven
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Managing input data and parameter estimation in a global water-balance model2005In: Geophysical Research Abstracts 7, 2005, p. 04377-Conference paper (Other academic)
  • 355.
    Widén Nilsson, Elin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Gong, Lebing
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Halldin, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Xu, Chong-Yu
    Department of Geosciences, University of Oslo, Oslo, Norway.
    Global water-balance modelling with WASMOD-M2007In: 5th Study Conference on BALTEX, Conference Proceedings, 2007Conference paper (Other academic)
  • 356.
    Widén Nilsson, Elin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Gong, Lebing
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Halldin, Sven
    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.
    Unsicherheitsstudien mit dem globalen Wasserbilanzmodell WASMOD-M.2007In:  :  , 2007Conference paper (Refereed)
  • 357.
    Widén-Nilsson, Elin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Halldin, Sven
    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.
    Global water-balance modelling with WASMOD-M: parameter estimation and regionalisation2007In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 340, no 1-2, p. 105-118Article in journal (Refereed)
    Abstract [en]

    Limitations in water quantity and quality are among the greatest social and economic problems facing mankind. However, difficulties in estimating the global long-term average runoff have led to differences of as much as 30% when integrated to the whole earth. Model estimates of runoff are especially uncertain for the 50% of the global land surface lacking consistent runoff data. In this study, we present the WASMOD-M global water-balance model, constructed to provide robust runoff estimates both for gauged and ungauged basins. WASMOD-M is a conceptual water-budgeting model with two state-variables and five tunable parameters. A simple parameter-value estimation procedure allowed “acceptable” parameter values to be identified both for the majority of gauged basins, and for most ungauged basins. Acceptable global simulations could be accomplished with continentally constant parameter values but at the cost of compensating errors on a basin scale. A “standard”, spatially-distributed parameter-value set was derived for a ”best” global simulation. Of the simulated 59132 0.5° × 0.5° cells, 45% got “good” parameter values as a by-product of regionalisation, 41% from regionalisation, whereas 14% were given a default value set. This global set allowed simulation of the 1915–2000 world water balance. The simulation was in the same range as previously published model results and compilations of runoff measurements. Long-term average within-year runoff variations agreed well with previously published results for most of the studied runoff stations although WASMOD-M was only calibrated against long-term average runoff. Improvement of WASMOD-M and other global water-balance models should be simplified by a common definition of basin boundaries and areas, as well as runoff. Further, modelling progress will depend on improved global datasets of precipitation and runoff regulation.

  • 358. Wilby, R.L.
    et al.
    Beven, Keith J.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Reynolds, N.S.
    Climate change and fluvial flood risk in the UK: More of the same?2008In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 22, no 14, p. 2511-2523Article, review/survey (Refereed)
    Abstract [en]

    The potential impact of climate change on fluvial flooding is receiving considerable scientific and political interest thanks to evidence from climate model projections and a widely held belief that flood risk may be increasing at European levels. This review compares published work on historical trends in UK rainfall and river flow records with high-resolution regional climate change projections, and attempts to reconcile apparent differences between the two. Attention is focused on the techniques used for climate change detection and attribution, as well as the potential confounding effects of land-use change. International and domestic efforts to build adaptive capacity rest on improved quantification of uncertainty in flood risk at very local, catchment and regional scales. This will involve further research to better integrate climate and land-management interactions, to understand changes in the dependence between different flood generating mechanisms, and to improve the characterization and communication of uncertainty at all stages of analysis. Resources are also needed to ensure that latest, but still uncertain, science is presented in an appropriate form to underpin policy development and is translated into sensible guidance for practitioners.

  • 359.
    Xu, Chong-yu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Avrinning: Lärobok för kurs Avrinning2005Book (Other academic)
  • 360.
    Xu, Chong-yu
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science. Air and Water Science.
    Avrinning: Lärobok för kurs Avrinning2004Book (Other scientific)
  • 361.
    Xu, Chong-yu
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science. Air and Water Science.
    Hydrological modeling in Climate change studies, progress and challenges2004In: Proceedings of Chinese-American Oceanic and Atmospheric (COAA) 2004 Annual Meeting: June 27-30, Beijing, China, 2004Conference paper (Other scientific)
  • 362.
    Xu, Chong-yu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Hydrological Modeling: lärobok för kurs Hydrologisk Analys och Modellering2005Book (Other academic)
  • 363.
    Xu, Chong-yu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Chen, D.
    Comparison of seven models for estimation of evapotranspiration and groundwater recharge using lysimeter measurement data in Germany2005In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 19, no 18, p. 3717-3734Article in journal (Refereed)
  • 364.
    Xu, Chong-yu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Gong, Lebing
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Jiang, T.
    Chen, D.
    Decreasing reference evapotranspiration in a warming climate: a case of Changjiang (Yangtze) river catchment during 1970–20002006In: Advances in Atmospheric Sciences, ISSN 0256-1530, E-ISSN 1861-9533, Vol. 23, no 4, p. 513-520Article in journal (Refereed)
    Abstract [en]

    This study deals with temporal trends in the Penman-Monteith reference evapotranspiration estimated from standard meteorological observations, observed pan evaporation, and four related meteorological variables during 1970–2000 in the Yangtze River catchment. Relative contributions of the four meteorological variables to changes in the reference evapotranspiration are quantified. The results show that both the reference evapotranspiration and the pan evaporation have significant decreasing trends in the upper, the middle as well as in the whole Changjiang (Yangtze) River catchment at the 5% significance level, while the air temperature shows a significant increasing trend. The decreasing trend detected in the reference evapotranspiration can be attributed to the significant decreasing trends in the net radiation and the wind speed.

  • 365.
    Xu, Chong-yu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science. Air and Water Science.
    Gong, Lebing
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science. Air and Water Science.
    Jiang, T.
    Chen, D.
    Spatial and temporal variations of reference evapotranspiration in Changjiang (Yangtze River) catchment during 1961 and 20002004In: Abstract Proceeding of Second IAG (International Association of Geomorphologists) Yangtze Fluvial Conference: June 24-27, Shanghai, China, 2004Conference paper (Other academic)
  • 366.
    Xu, Chong-yu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Gong, Lebing
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Jiang, T.
    Chen, D.
    Singh, V. P.
    Analysis of spatial distribution and temporal trend of reference evapotranspiration and pan evaporation in Changjiang (Yangtze River) catchment2006In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 327, no 1-2, p. 81-93Article in journal (Refereed)
    Abstract [en]

    In this study the Penman–Monteith reference evapotranspiration, pan evaporation measured by a 20 cm pan, and pan coefficient, i.e., the ratio of Penman–Monteith evapotranspiration to pan evaporation, at 150 meteorological stations during 1960–2000 in the Changjiang (Yangtze River) catchment in China are calculated, compared and regionally mapped. Their spatial distributions and temporal variations are examined and the causes for the variations are discussed. The spatial distributions of temporal trends in the reference evapotranspiration as well as in the meteorological variables that determine evapotranspiration are analyzed. The contributions of various meteorological variables to the temporal trend detected in the reference evapotranspiration and pan evaporation are then determined. The results show that: (1) the spatial distributions of reference evapotranspiration and pan evaporation are roughly similar. Spatial correlation coefficients between the reference evapotranspiration and the pan evaporation are high for both the seasonal and annual values. The temporal correlation between the two estimates is higher in the lower (humid) region than in the upper (semi-arid) region. The spatial distribution pattern of the pan coefficient is significantly influenced by wind speed and relative humidity in the region. Higher values of the pan coefficient were found in the central area of the catchment with a relatively high humidity (as compared with the upper area) and a very low wind speed (as compared with other areas); (2) for the whole catchment, there is a significant decreasing trend in both the reference evapotranspiration and the pan evaporation, which is mainly caused by a significant decrease in the net total radiation and to a lesser extent by a significant decrease in the wind speed over the catchment. No temporal trend is detected for the pan coefficient; (3) sensitivity analysis shows that the reference evapotranspiration is most sensitive to the net total radiation, followed by relative humidity, air temperature and wind speed.

  • 367.
    Xu, Chong-Yu
    et al.
    Department of Geosciences, University of Oslo, Oslo, Norway.
    Halldin, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Lundin, Lars-Christer
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Coello, Zairis
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Guerrero, José-Luis
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Westerberg, Ida
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Climate change and Hydrological modeling2007Conference paper (Other academic)
  • 368.
    Xu, Chong-yu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Krasovskaia, I.
    Gottschalk, L.
    Chen, D.
    Climate change and water resources modelling of the hydrological cycle: recent achievements and challenge2005Conference paper (Other academic)
  • 369.
    Xu, Chong-yu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Singh, V. P.
    Evaluation of three complementary relationship evapotranspiration models by water balance approach to estimate actual regional evapotranspiration in different climatic regions2005In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 308, no 1-4, p. 105-121Article in journal (Refereed)
  • 370.
    Xu, Chong-yu
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science. Air and Water Science.
    Singh, V.P.
    Review on regional water resources assessment under stationary and changing climate2004In: Water Resources Management, Vol. 18, p. 591-612Article in journal (Refereed)
  • 371.
    Xu, Chong-yu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Tunemar, Liselotte
    Chen, Yongqin David
    Singh, V. P.
    Evaluation of seasonal and spatial variations of lumped water balance model sensitivity to precipitation data errors2006In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 324, no 1-4, p. 80-93Article in journal (Refereed)
    Abstract [en]

    Sensitivity of hydrological models to input data errors have been reported in the literature for particular models on a single or a few catchments. A more important issue, i.e. how model's response to input data error changes as the catchment conditions change has not been addressed previously. This study investigates the seasonal and spatial effects of precipitation data errors on the performance of conceptual hydrological models. For this study, a monthly conceptual water balance model, NOPEX-6, was applied to 26 catchments in the Mälaren basin in Central Sweden. Both systematic and random errors were considered. For the systematic errors, 5–15% of mean monthly precipitation values were added to the original precipitation to form the corrupted input scenarios. Random values were generated by Monte Carlo simulation and were assumed to be (1) independent between months, and (2) distributed according to a Gaussian law of zero mean and constant standard deviation that were taken as 5, 10, 15, 20, and 25% of the mean monthly standard deviation of precipitation. The results show that the response of the model parameters and model performance depends, among others, on the type of the error, the magnitude of the error, physical characteristics of the catchment, and the season of the year. In particular, the model appears less sensitive to the random error than to the systematic error. The catchments with smaller values of runoff coefficients were more influenced by input data errors than were the catchments with higher values. Dry months were more sensitive to precipitation errors than were wet months. Recalibration of the model with erroneous data compensated in part for the data errors by altering the model parameters.

  • 372.
    Xu, Chong-yu
    et al.
    University of Oslo, Department of Geosciences .
    Widén, Elin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Halldin, Sven
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Modelling hydrological consequences of climate change: progress and challenges2005In: Advances in Atmospheric Sciences, ISSN 0256-1530, E-ISSN 1861-9533, Vol. 22, no 6, p. 789-797Article in journal (Refereed)
    Abstract [en]

    The simulation of hydrological consequences of climate change has received increasing attention from the hydrology and land-surface modelling communities. There have been many studies of climate-change effects on hydrology and water resources which usually consist of three steps: (1) use of general circulation models (GCMs) to provide future global climate scenarios under the effect of increasing greenhouse gases, (2) use of downscaling techniques (both nested regional climate models, RCMs, and statistical methods) for "downscaling" the GCM output to the scales compatible with hydrological models, and (3) use of hydrologic models to simulate the effects of climate change on hydrological regimes at various scales. Great progress has been achieved in all three steps during the past few years, however, large uncertainties still exist in every stage of such study. This paper first reviews the present achievements in this field and then discusses the challenges for future studies of the hydrological impacts of climate change.

  • 373. Yan, Z.
    et al.
    Jones, Phil
    Davies, T.D.
    Moberg, Anders
    Bergström, Hans
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Camuffo, D.
    Cocheo, C.
    Maugeri, M.
    Demaree, G.
    Verhoeve, T.
    Barriendos, M.
    Rodriguez, R.
    Martin-Vide, J.
    Yang, C.
    Extreme temperature trends in Europe and China based on daily observations2002In: Climatic Change, no 53, p. 355-392Article in journal (Refereed)
  • 374.
    Yan, ZW
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Jones, PD
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Moberg, A
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Bergstrom, H
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Davies, TD
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Yang, C
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Recent trends in weather and seasonal cycles: An analysis of daily data from Europe and China2001In: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, ISSN 0747-7309, Vol. 106, no D6, p. 5123-5138Article in journal (Refereed)
    Abstract [en]

    A wavelet analysis is conducted to investigate daily variability (DV, timescales of less than 3 days), weekly (weather) variability (WV, timescales of 5 days up to 2 months), and seasonal variability (SV, timescales of 8 to 17 months) in five temperature

  • 375.
    Yang, Zhibing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Niemi, Auli
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Fagerlund, Fritjof
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Illangasekare, Tissa
    Colorado School of Mines.
    Modeling of DNAPL spreading in heterogeneous variable aperture fractures2009In: Geophysical Research Abstract Vol. 11, EGU General Assembly 2009, 2009, p. 10221-Conference paper (Other academic)
    Abstract [en]

    The design of effective remediation schemes for dense non-aqueous phase liquids (DNAPLs) in fractured rocksrequires a fundamental understanding of their multiphase spreading and dissolution processes in these highly heterogeneoussystems. Stochastic heterogeneity is present both at the level of individual fractures and at the levelof fracture networks, and the processes of DNAPL spreading in these systems are not well understood. This workinvestigates the multiphase spreading and immobilization of chlorinated solvents in variable aperture single fracturesby means of numerical modeling. Multiphase simulation code iTOUGH2/T2VOC is used. Log-normallydistributed and spatially correlated aperture fields are generated and locally valid cubic law is assumed to relatethe variable aperture to the variable permeability. Hysteretic Brooks-Corey-Burdine type of capillary pressuresaturation-relative permeability relationships obtained by experimental study of Reitsma and Kueper (Water ResourcesResearch, 30 (1994): 865-878) are adopted and scaled with regard to interfacial tensions and local permeabilityaccording to Leverett J function. The effect of fracture aperture characteristics and correlation length aswell as fracture dipping angle on DNAPL spreading pathway and residual distribution is examined. Implicationsfor upscaling the observed behavior to fracture network systems are discussed.

  • 376. Zaldivar, J.M.
    et al.
    Håkanson, Lars
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science. LUVA.
    Berrojalbiz, N.
    Dueri, S.
    Carafa, R.
    Marinov, D.
    Jurado, E.
    Lacorte, S.
    Dahllöf, I.
    Dachs, J.
    The use of models for ecological risk assessment in coastal ecosystems: Thresholds point of view.2006Report (Other scientific)
  • 377.
    Zandin, Hanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science. LUVAL.
    Illangasekare, Tissa
    Niemi, Auli
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science. LUVAL.
    Moreno-Barbero, Elena
    Sakaki, T.
    Partitioning Tracer Test Performance in 3D Heterogeneous Tank Experiment: Influence of Nonaqueous Phase Liquid Source Zone2007In: International Conference ModelCARE 2007: Groundwater Modelling Credibility of Modelling Copenhagen September 9-13, 2007, 2007Conference paper (Refereed)
    Abstract
  • 378.
    Zandin, Hanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science. LUVA.
    Niemi, Auli
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science. LUVA.
    A Modeling case study of NAPL transport in porous medium under the influence of variable infiltration and geological heterogeneity.2006In: Proceedings of TOUGH Symposium 2006.: Lawrence Berkeley National Laboratory, Berkeley, California, May 15-17, 2006., 2006Conference paper (Refereed)
    Abstract
  • 379. Zhang, Q.
    et al.
    Liu, C. L.
    Xu, Chong-Yu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Xu, Y. P.
    Jiang, T.
    Observed trends of annual maximum water level and streamflow during past 130 years in the Yangtze River basin, China2006In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 324, no 1-4, p. 255-265Article in journal (Refereed)
    Abstract [en]

    Annual maximum streamflow and annual maximum water level and their variations exert most serious influences on human society. In this paper, temporal trends and frequency changes at three major stations of Yangtze River, i.e. Yichang, Hankou and Datong representing upper, middle and lower reaches, respectively, were detected with the help of parametric t-test, Mann-Kendall (MK) analysis and wavelet transform methods. The results show that: (1) there is a significant upward trend in streamflow at middle Yangtze River, indicating that flood hazard in the middle reach of the river, the flood rich region, will be more serious; (2) there is a consistent increase of water level from upper to lower reaches of the river which does not always coincide with the maximum streamflow variations; and (3) the periods of water level changes are decreasing over time, indicating the increasing occurrence frequency of annual maximum water level over time. This phenomenon is more obvious from upper Yangtze River to the lower Yangtze River. Human activities like destruction of vegetation, land reclamation and construction of levees reduced lake sizes and filled up the river bed, reducing the flood storage capacity of lakes and fluvial channel. These factors led to higher water level even some times the streamflow is small. Human should adjust his activity to enhance his adaptive capacity to flood hazard in the future.

  • 380. Zhang, Q.
    et al.
    Xu, Chong-yu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Becker, S.
    Jiang, T.
    Sediment and runoff changes in the Yangtze River basin during past 50 years2006In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 311, no 3-4, p. 511-523Article in journal (Refereed)
    Abstract [en]

    Annual runoff and annual suspended sediment loads of hydrological gauging stations along the mainstream of the Yangtze River basin (Pingshan station, Yichang station, Hankou station and Datong station) and main tributaries (Beipei station in Jialingjiang River, Wulong station in Wujiang River and Huangzhuang station in Hanjiang River) were analyzed with the help of Mann–Kendall trend analysis and linear regression analysis. Research results indicate that (1) changing patterns of runoff and sediment loads are different in different parts of the Yangtze River basin. No significant trend is detected for annual runoff at all stations at >95% confidence level. Changes of sediment loads, however, demonstrate different pictures in the Yangtze River basin. The sediment loads are in increasing trend in Pingshan station- the most upstream station on the Yangtze River basin (this increasing trend is significant at >95% confidence level after about 1990), but are in decreasing trend at other stations (including stations in the tributaries studied in this paper). This decreasing trend becomes more obvious from Yichang station to Datong station. (2) Water reservoirs exerted more influences on changes of sediment loads than on runoff, which is the main reason for the decreasing trend of sediment loads found in most stations. (3) Influences of water reservoirs on sediment loads are more obvious in the tributaries than in the mainstream of the Yangtze River basin, while in the mainstream the variation patterns of sediment loads are determined by multiple factors.

  • 381. Zhang, Q.
    et al.
    Xu, Chong-yu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Jiang, T.
    Wu, Y.
    Possible influence of ENSO on annual maximum streamflow of the Yangtze River, China2007In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 333, no 2-4, p. 265-277Article in journal (Refereed)
    Abstract [en]

    Variability and possible teleconnections between annual maximum streamflow from the lower, the middle and the upper Yangtze River basin and El Niño/Southern Oscillation (ENSO) are detected by continuous wavelet transform (CWT), cross-wavelet and wavelet coherence methods. The results show that: (1) different phase relations are found between annual maximum streamflow of the Yangtze River and El Niño/Southern Oscillation (ENSO) in the lower, the middle and the upper Yangtze River basin. In-phase relations are detected between annual maximum streamflow of the lower Yangtze River and anti-phase relations are found in the upper Yangtze River. But ambiguous phase relations occur in the middle Yangtze River, showing that the middle Yangtze River basin is a transition zone. Different climatic systems control the upper and the lower Yangtze River. The upper Yangtze River is mainly influenced by the Indian summer monsoon and the lower Yangtze is mainly influenced by the East Asian summer monsoon; (2) as for the individual stations, different phase relations are found in the longer and the shorter periods, respectively. In the longer periods, the annual maximum streamflow is more influenced by climatic variabilities, while in the shorter periods, it is influenced by other factors, e.g. human activities. The results of the study provide valuable information for improving the long-term forecasting of the streamflow using its relationship with ENSO and the Indian Monsoon.

  • 382.
    Zilitinkevich, Sergej
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Esau, Igor
    Resistance and heat/mass transfer laws for neutral and stable planetary boundary layers: old theory advanced and re-evaluated2005In: Quart. J. Roy. Met. Soc, Vol. 131, p. 1863-1892Article in journal (Refereed)
  • 383.
    Zilitinkevich, Sergej
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Esau, Igor
    Baklanov, A
    Atmospheric boundary layers in storms: advanced theory and modelling applications.2005In: Advances in Geosciences, no 2, p. 47-49Article in journal (Refereed)
  • 384.
    Öhman, Johan
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science. LUVA.
    Antikainen, J.
    Niemi, Auli
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science. LUVA.
    Thermo-Mechanical effects on hydraulic conductivity in a nuclear waste repository setting2004In: Coupled Thermo-Hydro-Mechanical-Chemical Processes in Geo-Systems, Fundamentals, Modelling, Experiments and Applications, 2004, p. 281-286Chapter in book (Refereed)
  • 385.
    Öhman, Johan
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science. AIR AND WATER SCIENCE.
    Niemi, Auli
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science. AIR AND WATER SCIENCE.
    Upscaling of Fracture Hydraulics by Means of an Oriented Correlated Stochastic Continuum Model2003In: Water Resources Research, Vol. 39, no 10Article in journal (Refereed)
  • 386.
    Öhman, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Niemi, Auli
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Tsang, Chin-Fu
    Probabilistic Estimation of Fracture Transmissivity from Wellbore Hydraulic Data Accounting for Depth-Dependent Anisotropic Rock Stress2005In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, no 5-6, p. 793-804Article in journal (Refereed)
    Abstract [en]

    A new method is introduced that incorporates the use of hydrological and rock mechanical data in assigning transmissivities for fracture-network models. The hydrological data comes from fixed-interval packer tests carried out in a borehole and the rock-mechanical data are the prevailing in situ depth-dependent stress-field and the stress-closure relationship of fractures.

    In the model, the fracture transmissivity distribution is considered to be constituted of two components, one deterministic stress-induced component and the other a stochastic component that describes the intrinsic variability of fractures in a network. The outcome is a tensorial description of fracture transmissivities in an anisotropic stress-regime, where the transmissivity for an arbitrarily oriented fracture in the network is determined by its orientation in relation to the ambient stress-field. These transmissivities are conditioned such that the overall results satisfy the hydraulic packer test data. The suggested procedure is applied to an example data set from a site at Sellafield, England.

    The results show that the probabilistic approach, relying on hydraulic data alone, may underestimate the true variability in fracture transmissivities, since the typically vertical boreholes entail a sampling bias towards horizontal fractures that are predominantly subject to vertical stress. The suggested method helps to account for the true underlying three-dimensional variability that is incompletely resolved by using the hydraulic borehole data alone. This method is likely to have the largest impact at low stress-levels, in strongly anisotropic stress-fields, for borehole directions parallel to one principal stress, and for fracture network geometries characterized by sets orthogonal to the three principal stresses.

  • 387. Šimůnek, J.
    et al.
    Hansson, Klas
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science. Air and Water Science.
    van Genuchten, M.Th.
    Models for Simulating Water Flow and Solute Transport in Subsurface: Development, Applications, and Future Plans2004In: International Workshop On Modeling Water Movement And Reactive Transport In Roads: February 2004 - Portsmouth, NH, USA, 2004Conference paper (Refereed)
5678 351 - 387 of 387
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