ISSN:0262-6667    

DOI:10.1080/02626669809492098

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669809492099

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The International Association of Hydrological Sciences (IAHS) is one of the seven international associations comprising the International Union of Geodesy and Geophysics (IUGG). Each Association has its own domain, but the boundaries between them are artificial. The Earth is undisciplined, and it does not recognize our academic subjects. In the US Academy Report “Solid-Earth Sciences and Society”, published in 1993, a number of broad objectives and major research areas were set up in a matrix which provided a research framework. A remarkable number of high-priority research opportunities in the “solid-Earth Sciences” are concerned with water, the subject of IAHS. Water is a critical material for society and indeed in nearly every topic in Earth science research. Our priorities for the next century must be based on the beautiful science which arouse our curiosity, but we must also give weight to societal problems. Examples of burning recent problems can be found in many of the world's megacities that are situated in locations threatened by earthquakes, volcanic eruptions, landslides, floods, and rising sea level.

ISSN:0262-6667    

DOI:10.1080/02626669809492100

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The decade of the 1990s has seen an awakening understanding by the global community of the importance of freshwater for societal and environmental vitality. In 1994, the Scientific Committee on Water Research (SCOWAR) was established by the International Council for Scientific Unions (ICSU) to address frontier freshwater-related science issues. This paper is SCOWAR's review of current trends and burning needs in selected areas of water resources research. The key future concerns to be served by the results of the research brought under review by SCOWAR are identified as equitable sharing of water resources and demand management, soil moisture for agriculture, water and health, ecological consequences of hydrological change, and improving data collection and assessment. SCOWAR also perceives immediate intellectual challenges in a number of other areas, such as, inter alia, multiple-scale problems, sustainability of reservoirs, dynamics of freshwater ecosystems. There is a general recognition that unavailability of water in sufficient quality and quantity has been and will continue to be an increasingly important constraint on socio-economic development. But the situation is not the same all over the world. SCOWAR is concerned that much of the increased pressure occurs and will occur in particular in Sub-Saharan Africa where high population growth and the desire to improve living standards expand water requirements.

ISSN:0262-6667    

DOI:10.1080/02626669809492101

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper provides a discussion of the development and application of Artificial Neural Networks (ANNs) to flow forecasting in two flood-prone UK catchments using real hydrometric data. Given relatively brief calibration data sets it was possible to construct robust models of 15-min flows with six hour lead times for the Rivers Amber and Mole. Comparisons were made between the performance of the ANN and those of conventional flood forecasting systems. The results obtained for validation forecasts were of comparable quality to those obtained from operational systems for the River Amber. The ability of the ANN to cope with missing data and to “learn” from the event currently being forecast in real time makes it an appealing alternative to conventional lumped or semi-distributed flood forecasting models. However, further research is required to determine the optimum ANN training period for a given catchment, season and hydrological contexts.

ISSN:0262-6667    

DOI:10.1080/02626669809492102

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Despite having the same snowmelt processes, snowpacks in urban environments experience a range of conditions different from those of rural areas. Melt is intensified at some sites due to greater radiative energy. Shading, however, can reduce radiation and melt at other sites. Changes to the radiation balance and snowpack processes have been investigated. A physical snowpack model was developed and tested against data from an impervious study plot in Sweden. Estimated surface runoff compared favourably with that measured. An urban radiation scheme captured the observed net allwave radiation well. Series of sensitivity analyses were made by perturbing the scheme to represent three urban locations: open ground and the southern (sunny) and north (shaded) sides of a hypothetical building. Cloudiness, albedo, wall temperature and sky view were altered to reproduce common urban conditions. Even without perturbation, the shaded and sunny sides of the building had different radiation fluxes—the south side experienced a daily average net radiation enhancement of 15 W m-2 and the north a decrease of 35 W m-2. This pattern was reflected in melt. Perturbation exaggerated the disparity.

ISSN:0262-6667    

DOI:10.1080/02626669809492103

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Use of output from global Circulation Models (GCMs) by regional or small scale rainfall-runoff models necessitates the disaggregation of the hydrological information available from GCMs to smaller scales. The hydrological processes of interest commonly occur at much smaller scales than those being modelled by GCMs. The present work examines the disaggregation of areally averaged monthly rainfall values of a basin or a region into point rainfall values. It uses some statistical methods based on a frequency analysis approach, a correlation approach and a disaggregation approach. A total of ten different methods have been tried and their relative performances compared based on some error criteria evaluated from observed and disaggregated point rainfall and mean areal rainfall values and their statistics. The results show the superiority of methods based on disaggregation techniques over other methods. The methods presented and discussed in the paper may very well be applied to disaggregate mean areal rainfall values into point rainfall values and also for infilling missing rainfall records.

ISSN:0262-6667    

DOI:10.1080/02626669809492104

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In a small heterogeneous limestone basin with mixed land use twelve flow components were distinguished by using chemographs of flood events and baseflow. Only a few of them are endmembers. The number of flow components depends on the tracers that are used and on the degree of heterogeneity. If the concept of flow components is restricted to endmembers only, the runoff generation process cannot be explained completely because runoff does not form by the mixing of chemically distinct water types alone. Beside water types, there are all kinds of temporal variations ranging from steep gradients to continuous changing, e.g. due to incomplete mixing, exhaustion of sources, etc. This means that the original concept of flow components should be extended to behaviour patterns in order to obtain a basic understanding of the very complex process of runoff generation. Furthermore it is an excellent approach to facilitate understanding of the temporal variation of water quality in flowing waters.

ISSN:0262-6667    

DOI:10.1080/02626669809492105

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

By considering the urbanization process on an overland plane whereby a relatively rough permeable surface is replaced by a relatively smooth impermeable surface, the effect of urbanization on the time of concentration is assessed. In the assessment, two opposing urbanization sequences are considered: one from downstream to upstream, and the other from upstream to downstream. The assessment is carried out in terms of the individual effect as well as the combined effect of the Manning resistance coefficient and the runoff coefficient. For both urbanization sequences and for all degrees of urbanization, the assessment shows that surface conversion from rough to smooth or from permeable to impermeable causes the time of concentration to be shorter. Urbanization at the upstream end causes the greatest decrease in the time of concentration, and the reduction in surface roughness causes a greater decrease in time of concentration as compared to the reduction in permeability. Depending on the pre- and post-urbanization land surface conditions, the assessment shows that the time of concentration could decrease to 4–39% of its original value. Moreover, the time of concentration for a plane with urbanization from downstream to upstream could be more than four times longer than that for a plane with urbanization from upstream to downstream. Finally, there is a remarkable resemblance between the results of this study with those obtained from drainage basins in earlier studies, and it appears that the results from earlier studies are only applicable for the upstream to downstream urbanization sequence.

ISSN:0262-6667    

DOI:10.1080/02626669809492106

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A grid network version of the two-layer Variable Infiltration Capacity (VIC-2L) macroscale hydrological model is described. The VIC-2L model is a hydrologically-based SVAT (Soil Vegetation Atmospheric Transfer) scheme designed to represent the land surface in numerical weather prediction and climate models. It is coupled to a linear routing scheme which is optimized with measured precipitation and streamflow data and is derived independently from the VIC-2L model. In this way it is possible to utilize streamflow measurements for the validation of coupled atmospheric-hydrological models. A baseflow separation routine is used to derive an equivalent description between the VIC-2L model and the routing model.

ISSN:0262-6667    

DOI:10.1080/02626669809492107

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor