ASSESSMENT OF HYDROLOGIC IMPACTS OF LAND USE CHANGE IN KULFO RIVER WATERSHED USING SWAT MODEL

Abstract

Land use and land cover changes in Kulfo River watershed experiences a lot of human disturbances due to agricultural expansion, and increasing urban demand for charcoal, fuel wood and timber; resulting in forest and land degradation. This in turn altered the hydrologic responses of the catchment. This study was conducted to assess the hydrological response of land use/cover change on Kulfo River flows. In this study SWAT model was selected as it applies distributed hydrologic model where various spatial parameters could be used and runoff is simulated at required scale. Spatial data (land use, DEM and soil) and meteorological data were obtained from USGS Satellite image, Ministries of Water Resources, Irrigation and Energy, National Meteorology agency respectively. SWAT model was used to simulate stream-flow for land use/land cover for the year 1985, 1995 and 2005 to determine the impact of land use/cover change on Kulfo stream flow. Land use maps of 1985, 1995 and 2005 were derived from satellite images processed using ERDAS Imagine 9.1 software. The model is calibrated and validated using historical flow data. Land cover change analysis has shown an increment in the proportional of the Agricultural land from 11.9% to 14.39%, Bare land from 25.8% to 14.14%, Forest from 16% to 12.43%. Water body, remain stable, however, Shrub land increased from 29.28% to 36.82% in between 1985 to 2005. Sensitivity analysis has shown that the curve number is the most sensitive parameter that affects the hydrology of the watershed. The models were calibrated using flow data from the 1989 to 2001 and validate from 2002 to 2008. The R 2 and Nash- Sutcliffe Efficient (NSE) value for the watershed were 0.78 and 0.93 for calibration and 0.80 and 0.78 for the validation respectively. It has been concluded that LULC highly affected the runoff process in the watershed.