The impact of land use and climate change on surface runoff and groundwater in Cimanuk watershed, Indonesia

The Cimanuk River with a total watershed area of 4010.8 km 2 flowing from the Garut Regency to Indramayu Delta is the longest in West Java Province. However, the cumulative effects of climate change, increased population, and fish farming in the coastal area have continuously pressured the availability of water resources in its watershed. This study was, therefore, aimed to analyze the impact of land use and climate change on surface runoff and groundwater using a SWAT model. This is a physically based semi-distributed hydrological model with various applications, particularly to simulate water balance and watershed management. Daily discharge record for 2005–2008, land use data for 2002–2017, and the simulated climate (1979–2003) and projected climate data (2075–2099) retrieved from MRI-AGCM3.2 20-km by the Meteorological Research Institute of Japan Meteorological Agency were used in this research. The result showed that the calibration and validation of SWAT model have exhibited satisfactory criteria for hydrological simulations. The modeled period showed land use changes caused a general increase in runoff and decline in base flow contribution to annual streamflow. The changes between the current and projected climate exhibited increase in Q max / Q min ratio in certain years.