摘要:

Precipitation and discharge have been measured for several years in two small forested catchments located in the Mediterranean area of Spain. Actual evapotranspiration has been calculated as the difference between annual precipitation and discharge. Results show that: (a) most of the precipitation is evaporated rather than lost by streamflow, even in the most humid years; (b) there is a high inter-annual variability both in discharge and evapotranspiration; and (c) annual evapotranspiration correlates significantly with annual precipitation, in contrast to the constancy of annual evaporation in catchments of wet, colder climates. Finally, a simple expression is proposed in order to calculate annual actual evaporation from the ratio of precipitation to potential evapotranspiration. This expression uses a derived exponent,k, which takes into account the characteristics of individual catchments.

ISSN:0262-6667    

DOI:10.1080/02626669109492492

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The effects of climate change obtained through model simulations on runoff and snow cover in Finland are presented in this study. The results are based on hydrological model simulations using the information from one climatic general circulation model (GISS) scenario with doubled atmospheric carbon dioxide as input. According to the GISS model scenario, the temperature increase in Finland will be 2–6®C, the precipitation increase 10–30 mm per month and the evaporation increase 5–30 mm per month. The effects of these climatic changes on runoff and snow cover have been evaluated in twelve different watersheds by hydrological watershed models. According to the results the mean discharge (MQ) increases by 20–50%, the mean minimum discharges (MNQ) increase considerably in winter due to a two to three months shorter snow cover period and the mean maximum discharges (MHQ) decrease due to diminished maximum snow water equivalents. In southern Finland persistent winter snow cover will vanish.

ISSN:0262-6667    

DOI:10.1080/02626669109492493

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The probability-distributed catchment model, as originally proposed by Moore & Clarke (1981), is re-examined from a maximum statistical entropy viewpoint. The distribution of water within a catchment is treated as a problem of statistical inference and resolved using an entropy maximization technique. A simple runoff generating mechanism is employed, which, together with the catchment mass balance equation, yields a catchment model involving just one dynamic parameter,y, and two constants,kand λ. The parameterydetermines the temporal variation of catchment storageVand runoffq.The latter is nonlinearly related toVthrough q = k(1—λyV), whereyprovides the nonlinear departure from the simple linear reservoir q = kV.

ISSN:0262-6667    

DOI:10.1080/02626669109492494

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The daily discharge of the Chang Jiang (the Yangtze River) at Yichang (catchment area about one million square kilometres) is derived by routing the daily discharge of the Jinsha Jiang at Pingshan (catchment area about half a million square kilometres) with modelled runoff based on daily precipitation at 14 rainfall stations in the downstream Sichuan basin. Precipitation at each station is transformed into runoff by means of a tank model composed with a time lag. The time lag is assumed to obey a normal distribution, the mean and the standard deviation of which are determined by the discharge on the same day at Three Gorges.

ISSN:0262-6667    

DOI:10.1080/02626669109492495

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Possibilities for the development of dynamic-stochastic models of runoff formation with random inputs are discussed. Two models are described: the first allows the calculation of the statistical distribution of the maximum discharges of rainfall floods, and the second the statistical distribution of snowmelt flood volumes. Meteorological inputs are generated by the Monte- Carlo method. Physically-based models are used for the transformation of input data into runoff. The various models are applied to observation data from two watersheds.

ISSN:0262-6667    

DOI:10.1080/02626669109492496

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

One of the most important problems of hydrological forecasting is to obtain a reliable estimation of effective rain. Infiltration is one of the variables which greatly influences the partitioning of rainfall into surface runoff and subsurface flow. This paper presents an infiltration model which describes the unsaturated zone as a multi-layer system. For this purpose a relationship developed by Denisov (1978) for total hydraulic potential versus soil moisture content has been used. The model contains a system of ordinary differential equations for describing soil moisture movement and it can be interpreted as an aggregated simulation model with lumped parameters. Some basic equations and results of simulation runs are presented.

ISSN:0262-6667    

DOI:10.1080/02626669109492497

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669109492498

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669109492499

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669109492500

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669109492501

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor