IMPACTS OF LAND COVER CHANGES ON HYDROLOGIC RESPONSES: A CASE STUDY OF CHI RIVER BASIN, THAILAND

Land use and land cover (LULC) have been continuously changing, through human activities, leading to variations in hydrological cycle. In this study, we applied SWAT model to investigate potential impacts of LULC on water budget of the Chi river basin in Thailand. Five plausible scenarios of land use change were evaluated, including an conversion of forested area, expansion of farmland, switching of rice paddy fields to energy crops and two scenarios involving conversion of farmland to rice and sugarcane plantation. The results indicated that different land use scenarios contributed to various effects in annual and seasonal water yield and evapotranspiration (ET). Conversion of forested area and farmland showed slightly small changes on water flows and ET. Substitution of paddy fields by sugarcane plantation showed clearly reduced water flows and increased ET by almost 5.0% in dry season. Particularly, in case of expansion of rice paddy fields to farmland, small changes occur on annual flow and ET but more significant effect occur on seasonal flows. The results showed decrease in ET by nearly 12.0%, leading to increase of water yield by up to 5.1% during dry season. Finally, conversion of farmland to sugarcane plantation for biofuel production showed significant effect on seasonal ET, mainly decreasing in dry season by 4.5 % but small changes were detected on water yields.