Hydrologic Impact Evaluation of Land Use and Land Cover Change in Palico Watershed, Batangas, Philippines Using the SWAT Model

Abstract

Information on the relationship between hydrologic response and land use and land cover change (LULC) is vital for proper management of water resources and land use planning. This study aimed to evaluate the impact of LULC on the hydrologic characteristics of Palico watershed in Batangas, Philippines using the Soil and Water Assessment Tool (SWAT) model. Model inputs used were the 1989 and 2013 LULC maps and climatological and hydrologic data. Good agreement was obtained between simulated and observed streamflow values during model calibration (NSE=0.84 & R2=0.86), and validation (NSE=0.61 & R2=0.68). For the entire watershed, reduction in forest cover and rangeland resulted to an increase in surface runoff and decreases in baseflow or dry season flow and groundwater recharge. LULC changes affected the water quantity and timing of occurrence. Subbasin with 22% increase in forest cover and rangeland increased the baseflow by 1% to 15% and reduced the streamflow by 1% to 17% during the rainy months. Another subbasin with 54% forest loss resulted to more pronounced rainfall-runoff response with 11% to 17% decrease in baseflow and 4% to 24% increase in streamflow during rainy months. Finding the balance between these two opposite LULC change scenarios is crucial for the attainment of water security and sustainability in the watershed and in the areas it serves.