Assessment of Water Availability and Variability under Representative Concentration Pathways (RCP) 2.6, 4.5, and 8.2 of Agos River in Quezon, Philippines

Abstract

This study assesses the variability of water availability in the Agos Watershed from 2025 to 2044 under Representative Concentration Pathways (RCP) 2.6, 4.5, and 8.5, highlighting the potential hydrologic impacts of climate change. Using the Statistical DownScaling Model (SDSM), rainfall projections were statistically downscaled and bias-corrected through its integrated Variance Inflation Method (VIF). The model was calibrated using observed rainfall data from 2003 to 2023, with 70% allocated for calibration, enhancing the reliability of rainfall and river inflow simulations. Results reveal consistent seasonal peaks in October and November, with annual rainfall under RCP 8.5 reaching a projected maximum of 4,470.10 mm by 2032—substantially higher than 3,836.87 mm (RCP 2.6) and 3,720.63 mm (RCP 4.5). These rainfall trends correspond to inflow peaks of 218.69 m³/s, 217.47 m³/s, and 211.53 m³/s, respectively. While increased inflows enhance short-term availability, drier months such as February and May reflect potential periods of scarcity. Findings underscore the importance of climate-informed water management strategies, emphasizing adaptive infrastructure, conservation measures, and integrated planning to bolster the watershed’s resilience.