Water Availability and Variability Analysis Using Different Earth System Models RCP 2.6, 4.5, and 8.5 Scenarios in Bauan, Batangas Philippines

Climate change has been affecting the Earth for more than several decades. With these prevailing effects, the demand to determine the possible impact of this changes in a specific area’s water availability and variability as well as rainfall levels are becoming necessary for planning. To predict the precipitation levels for the next 20 years, downscaling method was employed here. The study aimed to analyze and evaluate the effects of climate change on the water availability and variability in Bauan, Batangas by downscaling rainfall data considering Earth System Models’ Representative Concentration Pathways (RCPs) 2.6, 4.5, and 8.5 scenarios. The study could help in the planning and management of water supply in a certain area that mainly relies on surface water sources. The Statistical Downscaling Model – Decision Centric 4.2.9 and Hydrologic Engineering Center – Hydrological Modeling System (HEC-HMS) were used to attain the objective of this research. After the downscaling process and hydrologic simulation, a set of predicted data were produced, rainfall levels and water inflows in the watershed were generated for each RCP scenario. Results of each RCP scenario were compared to each other to analyze the differences in these what ifs scenarios. Future climate changes in Bauan, Batangas were projected under the RCP 2.6, 4.5, and 8.5 scenarios for a period of 20 years (2021 – 2041). The highest inflow data is 603.8 m3/s from the RCP 4.5 scenario while the highest average inflow was from RCP 8.5 with an inflow value of 541.848 m3/s. Meanwhile, the RCP 2.6 projected the lowest value of inflow and the lowest average among the three, with values of 359.9 m3/s and 406.505 m3/s.