Author(s)

A. N. Hadadin

Abstract

With the rapid advancement in computer and information technologies, computer modeling has become a vital tool in watershed research and management practices. This paper presents a brief review of the development and application of watershed hydrologic models through the past five decades. The purpose of this study is to apply the Stanford Watershed Model (SWM) to estimate the rainfall-runoff relationship for the Wala valley (catchment area 1800km2). The SWM has been widely accepted as a tool to synthesis a continuous hydrograph of hourly or daily streamflow. Many meteorological and hydrological data and several hydrologic parameters are required as input data. Sensitivity analysis and a trail and error adjustment technique are used for optimization of the number of parameters of the model. Comparison between estimated and measured surface runoff for the Wala valley indicates that the model is considerably efficient in predicting the total annual surface runoff from rainfall. Keywords: watershed modeling, watershed hydrology, rainfall-runoff relationship, continuous hydrograph, streamflow, Stanford Watershed Model, surface runoff. 1 Introduction Watershed models range widely in complexity. Some are nothing more than simple empirical equations, others perform a complex accounting of soil moisture and water in various stages of runoff. Hydrological models are divided broadly into two groups; the deterministic models seek to simulate the physical processes in the catchment involved in the transformation of rainfall to streamflow, whereas stochastic models describe the hydrological time series of

Keywords

watershed modeling, watershed hydrology, rainfall-runoff relationship, continuous hydrograph, streamflow, Stanford Watershed Model, surface runoff.