Climate Change Impact on the Hydrologic Regimes and Sediment Yield of Pulangi River Basin (PRB) for Watershed Sustainability

The impacts of climate change are increasingly threatening the sustainability of ecosystems around the world. The Pulangi River Basin (PRB) in the Philippines is experiencing sedimentation beyond the tolerable amount (11.2 tons/ha/yr) due to land conversion and the effects of climate change. Changes in precipitation and temperature due to climate change are likely to further affect the annual runoff and sediment yield of PRB. In this study, the Soil and Water Assessment Tool (SWAT) was employed to simulate various scenarios of twelve downscaled climate projections from three Global Circulation Models (GCM) of CMIP5 under two Representative Concentration Pathways (RCP 4.5 and 6.0) for 2040-2069 and 2070-2099 timeframes, and the results were compared to a baseline period (1975-2005). This study revealed that the maximum mean annual precipitation is expected to increase by 39.10%, and the minimum and maximum temperatures are expected to increase by 3.04 degrees C and 3.83 degrees C, respectively. These observed changes correspond to an increase in runoff (44.58-76.80%) and sediment yield (1.33-26.28%) within the sub-basins. These findings suggest a general increase in the threat of severe flooding and excessive soil loss, leading to severe erosion and reservoir sedimentation throughout the PRB.