Projecting hydrological response to climate change and urbanization using WEAP model: A case study for the main watersheds of Bicol River Basin, Philippines

Abstract

Study region: Bicol River Basin, Philippines Study focus: The study investigated the impact of climate change and urbanization on water resources in the Philippines. It used Water Evaluation and Planning (WEAP) software and climate forecasts from eight Global Circulation Models (GCMs) to assess the nation's water balance, focusing on two sensitive watersheds: Libmanan-Pulantuna (LPW) and Quinali (QW). The study projects water availability in these areas by creating climate-urbanization scenarios. Furthermore, our endeavor aims to provide insight into the complexities of hydrological processes within traditionally under-observed regions, serving as a blueprint for future environmental planning and sustainable water management in the Philippines and beyond. New hydrological insights: The study's simulated streamflow matches observed data (R2: 0.70–0.85, NSE: 0.57–0.67) and indicates warming trends and variable precipitation in both watersheds. Rising water demand in domestic and industrial sectors contrasts with a decline in agriculture due to land conversion. QW faces increased water demands from urbanization, while LPW has lower unmet water demand. Low Land Decline scenarios indicate consistent water scarcity in agriculture, while High Land Decline scenarios predict a decrease by 2100. Urbanization significantly impacts future water stress more than climate change, with reduced agricultural land generally associated with lower water stress. Conversely, climate change exacerbates unmet demand issues in domestic and industrial development cases. Due to diminishing agricultural land, both watersheds are expected to transition from water-deficient to water-surplus regions by the end of the century. However, immediate action is crucial to address current water demands, particularly in the severely water-deficient Quinali Watershed.

Keywords

• WEAP
• Bicol River Basin
• Climate change
• Urbanization
• Agricultural land decline