摘要:

There are considerable difficulties in assembling global hydrological data sets in near real time, data that might be used for deciding investment for sustainable water resources development and management, for environmental protection and for studying global change. Several reasons exist for these difficulties, a new one is that many countries have recently been cutting back on hydrological networks and the services that operate them. This means that knowledge of the World's water resources is getting worse when the global demand for water is accelerating. By way of contrast, meteorologists have ready access to large volumes of global data, much of it in real time, principally through WMO's World Weather Watch (WWW). A World Hydrological Cycle Observing System (WHYCOS) is proposed to facilitate access to global data and support hydrological services in need. A world-wide network of about 1000 stations is planned for the largest rivers, together with associated data bases and products to meet the needs of users. WHYCOS would start in Africa with a 100-station network and be expanded to other regions. It is a necessary tool for averting the coming water crisis and essential to the drive towards sustainable development.

ISSN:0262-6667    

DOI:10.1080/026266693099492687

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A study of the effect of changes in climate on aquifer storage and river recharge using a simple model of an idealized aquifer/river system shows the combined influence of aquifer properties and climate change scenario on the system response. The study shows that changes in the seasonal distribution of recharge may have a critical effect on low flows in rivers supported by baseflow. However, rivers supported by slowly responding aquifers may show a considerable delay in response to climate change allowing an opportunity for water resources planning over an extended period.

ISSN:0262-6667    

DOI:10.1080/026266693099492688

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A two-stage formal approach to hydrological model conceptualization is described. The approach requires the definition of hydrological variables in terms of states and rates, the construction of state-rate diagrams and the definition of equations for the rates based on an indepth understanding of the related hydrological processes. It is inferred that the approach can help modellers arrive at models which are conceptually more feasible for operational use and for theoretical studies. STELLA, a programme specifically designed to facilitate model conceptualization using this approach, is also briefly described. The use of the two stage formal approach with STELLA will be an excellent teaching tool for hydrological modelling.

ISSN:0262-6667    

DOI:10.1080/026266693099492689

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Vertical surface properties of the landscape were measured using a laser altimeter mounted in a small twin-engine aeroplane. The laser altimeter makes 4000 measurements per second with a vertical recording precision of 0.05 m for a single measurement. These airborne laser measurements were analysed to provide information on topography, vegetation canopy and stream and gully cross-sections. Laser altimeter data were used to measure small (less than 0.20 m deep) and large gullies and stream cross-sections. Vegetation canopy heights, cover, structure and distribution were determined in studies in Texas and Arizona. Laser measurements of vegetation cover and height were significantly correlated with ground measurements made with line-intercept methods. While conventional ground-based techniques may be used to make all these measurements, airborne laser altimeter techniques allow the data to be collected in a quick and efficient way over large and inaccessible areas. The airborne laser altimeter data can also help quantify various land surface parameters needed for natural resource and landscape management or required by hydrological simulation models. Measurements of landscape properties over large areas provide a better understanding of landscape functions and can lead to the development of better management plans to conserve and improve the productivity of natural resources.

ISSN:0262-6667    

DOI:10.1080/026266693099492690

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A modified two-level estimator is proposed and implemented for real time flood forecasting for a hydrological system plagued by a high order of uncertainties because of ungauged tributaries and scanty nonrepresentative rainfall information. A finite set of time varying models running in parallel constitutes a coarse estimator for the proposed two-level estimator. The results of this coarse estimator are combined on the basis of a posterior probability distribution; the weighted model thus obtained is fine tuned by a Restricted Exponential Forgetting (REF) algorithm based on a fine estimator. In addition to the usual link between the coarse estimator and the fine estimator, a backward fine-to-coarse estimator link is also suggested. This not only helps in the crucial task of compilation of the finite model set of the coarse estimator but also materially affects the performance of the other components of the estimator. The estimator is shown to yield improved results.

ISSN:0262-6667    

DOI:10.1080/026266693099492691

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Conceptual mathematical models are a useful tool for rainfallrunoff modelling of a basin. The calibration of such models has attracted the attention of a number of hydrologists since unique and optimal parameters are difficult to obtain. The calibration of a conceptual model is discussed through a simple conceptual model whose parameters are determined using a search technique. It is shown that the optimization algorithm converges to a global optimum even when the errors in the initial parameters are quite significant and the input environment is noisy.

ISSN:0262-6667    

DOI:10.1080/026266693099492692

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/026266693099492693

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/026266693099492694

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/026266693099492696

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/026266693099492697

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor