HYDROLOGICAL SIMULATION IN XEDONE BASIN USING SWAT MODEL

Abstract

For effective planning and sustainable management of land and water resources in a river basin, proper assessment of water resources is required. The assessment of water resources can be done effectively with the help of appropriate well calibrated hydrological model. The Soil and Water assessment Tool (SWAT), developed by Agriculture Research Service of USDA, has gained popularity in the recent past, because it is a distributed watershed model and has capabilities to simulate rainfall runoff response, impact of land management practices on water, sediment and agricultural chemical yields in complex watersheds. The present study is undertaken with an aim to test the performance of SWAT model on Xedone River located in Southern Lao PDR draining an area of 5714.75 km2. For model application, the catchment area is divided into 16 sub-watersheds. The whole catchment area is classified . into nine land use categories. Available hydrological data (i.e. from 1992-2002), split into two groups is used for calibrating and validating parameters of the model. The calibrated model parameters are also used to test the performance of the model at upstream intermediate gauging site at Saravan. Model performance is adjudged base on visual comparison of observed and model computed runoff as well as on statistical measures of mass balance error, coefficient of determination and Nash Sutcliffe efficiency (NSE). Comparative analysis of results is done on daily and monthly time scale. Analysis reveals that during calibration period, the Nash Sutcliffe efficiency varies between 0.58 to 0.82 with an average of 0.70 on daily time scale and 0.77 to 0.96 with an average value of 0.86 on monthly time scale at Suvanakily gauging site. The performance of the calibrated model at intermediate test site, Saravan gauging site has show good agreement between observed and model computed hydrographs with NSE varying between 0.60 to 0.80 with average value of 0.72 on daily time scale and 0.69 to 0.96 with an average value of 0.86 on monthly time scale which are comparable to NSE achieved for entire watershed indicating the applicability of the model at intermediate locations also. Overall, based on visual and statistical evaluation, it can be concluded that the SWAT model can be used with confidence to simulate runoff response in Xedone basin on daily, monthly and annual basis.