Projection of the water resources availability in the Philippines under the impact of climate change

The Philippines is blessed with abundant water resources which theoretically assure the country of adequate freshwater supply for its agricultural, industrial and domestic uses. Water resources distribution, however, varies temporally and spatially due to different geographic and climate conditions in different parts of the country. Climate change and increasing incidence of extreme weather events severely affects water supply, while population growth, urbanization, agricultural and industrial expansion affects of water demand. The challenge of food security is directly related to the challenge of water availability. Up until recently, all estimates of water resources in the Philippines is based on a landmark 1998 NWRB-JICA study which presented water demand and availability projections for different water resources regions until 2025 under low and high growth scenarios. However, the hydrological estimates in this study were based on insufficient data then and the river basin assessments are no longer valid due to land use changes and the impact of climate change now. These acknowledged shortcomings point to the need for an updated and more comprehensive water-resource assessment for the Philippines. This paper presents a template for computing water resources availability projections under the impact of climatic change. Climatic change was evaluated based on rainfall generated from climate projection methods under different emission scenarios. The results of water supply and demand projections for years 2020 and 2050, including maps of regional distribution, of the Cagayan and Mindanao River Basins are presented as examples. The data generated here can be used for short-term and long-term planning of water resources management and development projects, including drought management and flood control structure plans.