Distributed Hydrological Modeling of Upper Prek Thnot River Watershed, Cambodia

Abstract

The aim of this research was to establish a basic structure of distributed hydrological model equipped with an ET sub-model which can be applied to watersheds having distinct dry season. The model is a grid-based model and each cell of the grid consists of two layers of storage tanks. The upper layer tank was considered to correspond to the root zone model, and the idea of Sakai's ET sub-model was employed to it. The main processes of this model such as infiltration, evapotranspiration, percolation, overland flow, interflow and channel flow were modeled by Green-Ampt explicit scheme, Sakai's ET equation, Brook-Corey equation, kinematic wave explicit scheme, Darcy equation and Muskingum-Cunge equation respectively. The model was applied to the Upper Prek Thnot River watershed in Cambodia. The model parameters were derived from a digital elevation model (DEM), land use and soil type map of the watershed. These parameters and the observed daily hydro-meteorological data (2001-2003) were used to simulate outflow hydrograph and to test the performance of the model. It was found that actual evapotranspiration was properly simulated in comparison with the potential evapotranspiration and the simulated daily runoff showed fairly good agreement with the observed runoff at Peam Khley gauging station. It was confirmed that this model could work properly with the ET sub-model.