摘要:

Discharge characteristics and the role of monsoonal rainfall in the glacierized Dokriani catchment in the Ganga River headwaters, Garhwal Himalaya, India are examined for the summer ablation period of 1994. Monsoonal rainfall over the glacierized area appears to be an important factor controlling the characteristics of the discharge hydrograph. Monsoonal cloud cover reduces the energy input resulting in subdued ice melt. The monsoonal component was separated from the bulk flow hydrograph recorded close to the glacier snout using a mass balance approach: 11.46% of the total discharge of 62.38 x l06m3was contributed by the rainfall over the catchment.

ISSN:0262-6667    

DOI:10.1080/02626669909492284

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The flood that occurred in summer 1997 in Poland, affecting the drainage basins of the Odra and the Vistula, caused 54 fatalities and material losses of the order of billions of US$. The flood struck a large part of the country and caused inundation of 665 000 ha of land. The number of evacuees was 162 thousand. The rhetoric commonly used in Poland refers to the Great Flood of 1997 as an event whose scale exceeded all imagination about the possible size of the disaster. Indeed, historic maxima of river stage and flow rate were considerably exceeded. From the hydrological point of view, this flood was a very rare event, with a return period in some river cross-sections of the order of a thousand years and more. As this natural disaster, striking a dynamically developing country-in-transition, attracted much international interest, a holistic view of it is presented. Attempts to answer the questions: “Could the disaster have been avoided?” and “What lessons can be learnt from the flood?” are also made.

ISSN:0262-6667    

DOI:10.1080/02626669909492285

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Various theoretical expressions are presented for determining risk in water resources systems design based on floods modelled by dependent processes. The effect of dependence on the simple risks involved in any engineering design is investigated on the basis of the lag-one Markov process. Asymptotically dependent process formulations reduce to independent case solutions that are already available in the literature. It is shown that a design risk value can be determined if the expected project life, serial correlation coefficient and simple risk are known. Necessary procedures and tables are presented for risk calculations when the variables concerned are serially correlated.

ISSN:0262-6667    

DOI:10.1080/02626669909492286

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The problem of a groundwater model calibration is posed as a multiextremum (global) optimization problem, rather than the more widely considered single-extremum (local) optimization problem. Several algorithms of randomized search incorporated in the global optimization tool GLOBE are considered (including the canonical genetic algorithm and more recently developed adaptive cluster covering), and applied to the calibration of the groundwater model TRIWACO. The results show the usefulness of global optimization algorithms in the automatic calibration of even complex models having considerable running times.

ISSN:0262-6667    

DOI:10.1080/02626669909492287

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Application of the concept of combining the estimated forecast output of different rainfall-runoff models to yield an overall combined estimated output in the context of real-time river flow forecasting is explored. A Real-Time Model Output Combination Method (RTMOCM) is developed, based on the structure of the Linear Transfer Function Model (LTFM) and utilizing the concept of the Weighted Average Method (WAM) for model output combination. A multiple-input single-output form of the LTFM is utilized in the RTMOCM. This form of the LTFM model uses synchronously the daily simulation-mode model-estimated discharge time series of the rainfall-runoff models selected for combination, its inherent updating structure being used for providing updated combined discharge forecasts. The RTMOCM is applied to the daily data of five catchments, using the simulation-mode estimated discharges of three selected rainfall-runoff models, comprising one conceptual model (Soil Moisture Accounting and Routing Procedure—SMAR) and two black-box models (Linear Perturbation Model—LPM and Linearly-Varying Variable Gain Factor Model—LVGFM). In order to get an indication of the accuracy of the updated combined discharge forecasts relative to the updated discharge forecasts of the individual models, the LTFM is also used for updating the simulation-mode discharge time series of each of the three individual models. The results reveal that the updated combined discharge forecasts provided by the RTMOCM, with parameters obtained by linear regression, can improve on the updated discharge forecasts of the individual rainfall-runoff models.

ISSN:0262-6667    

DOI:10.1080/02626669909492288

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In the Dobrich region, with an area of a little over 4000 km2, two important aquifer systems can be differentiated, which we have named the Upper and Deep Aquifers. The hydrodynamic and hydrogeochemical characteristics of these two aquifers are different. Agricultural activities, livestock units, and urban waste waters and solid wastes constitute the principal sources of contamination of the Upper Aquifer. Furthermore, signs of marine intrusion in some coastal zones have been detected. The Deep Aquifer is found to be affected by hydrogeochemical processes related to hydrocarbons that generate elevated concentrations of H2S and NO2(which may exceed 10 mg 1−1). This aquifer has numerous deep overflowing boreholes that lack appropriate capping, with the consequent loss of resource, draining in the order of 4 m3s−1of thermal and sulphurous waters.

ISSN:0262-6667    

DOI:10.1080/02626669909492289

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The southeast of the Betic Cordilleras has long been recognized as an area with numerous geothermal anomalies of regional character. Many thermal springs appear related to currently tectonically active fault systems. Carbon dioxide and other gases in these waters have been mobilized through those fault systems. The great depth of these “slip-strike zones” affects the entire thickness of the lithosphere and leads to contrasting crustal domains of different natures and structures. In this area, the detrital aquifer of the Alto Guadalentín has thermal waters with high salinity and unusually high contents of CO2gas. The utilization of Principal Components Analysis (PCA) in the hydrogeochemical study of this aquifer has revealed that the origin of the salinity of its waters is due essentially to processes of dissolution of the Miocene evaporite rocks, principally sulphate, and to the contribution of deep hydrothermal waters that show signs of endogenous CO2contamination. To a lesser extent, infiltration waters also form an input, with elevated sulphate, chloride and nitrate content. Likewise, PCA has enabled the differentiation of distinct groups of water to which these processes have had a variable contribution.

ISSN:0262-6667    

DOI:10.1080/02626669909492290

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The capability of the spatially-distributed, physically-based, rainfall-runoff modelling system, MIKE SHE, to simulate the hydrological behaviour of the natural and drained parts of the North Kent Grazing Marshes, UK, is investigated. The MIKE SHE code is applied to Bells Creek, a small, underdrained, agricultural catchment located within the marshes. The model is used to both provide insights into the essential parameters that control the hydrological processes in the catchment, and predict the influence of various, hypothetical, water management strategies (land use and drainage) on pumped discharge and soil moisture storage in the catchment. The water table model predictions arising from these hypothetical scenarios are also compared against field data obtained from on-going hydrological research on the neighbouring, natural, Elmley Marshes. The comparison is found to be favourable. The results of this study indicate the potential of the MIKE SHE system to simulate the hydrological regime of these wetlands, and hence to play an important role as a tool that can assist environmental and conservation agencies in the sound management of wetland resources.

ISSN:0262-6667    

DOI:10.1080/02626669909492291

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Nous examinons ici le phénomène très complexe de l'érosion hydrique de bassins versants. L'approche adoptée consiste d'une part à quantifier l'érosion à plusieurs échelles spatiales, au sens de la méthode Wischmeier, de la simulation de pluies sur 1 et 87 m2, de micro-bassins expérimentaux, de retenues collinaires et d'un barrage en exploitation, et d'autre part à rechercher un modèle régressif pouvant expliquer la relation débit solide-débit liquide pour les différentes formes d'érosion. Une zone de marnes du bassin de la Mina en Algérie, productive en sédiments pour un barrage en aval et représentant le cinquième de la surface, a constitué la zone expérimentale. Les résultats montrent que, vu la complexité des facteurs mis enjeu, il est quasiment impossible d'extrapoler à différentes échelles. Le modèle puissance caractérise la relation débit solide-débit liquide, quelle que soit l'échelle spatiale considérée.

ISSN:0262-6667    

DOI:10.1080/02626669909492292

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669909492293

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor