A study on impact of climate variability/change on water resources in the Philippines

Abstract An effort to investigate possible effects of climate variability/change on water resources in the Philippines has been undertaken. Long term temperature and rainfall trends at various stations as well as hydrologic parameters in multipurpose dams in the Philippines were examined. Results indicated generally increasing trends of yearly temperature at representative stations. However, the inter-annual variations of yearly and seasonal rainfall indicated geographical patterns among trends. Rainfall trends in western Luzon are mainly increasing while decreasing trends are indicated in eastern section of Luzon, most parts of Visayas and the whole of Mindanao. Water inflows in the major multipurpose dams in Luzon and at Lake Lanao in Mindanao indicated decreasing trends. Decrease of water inflow is found to be prominent during ENSO events. Most drought occurrences based on climatological studies in the Philippines are found to be ENSO-related. At this stage of the investigation, there is a tendency to believe that the trends exhibited by the above-mentioned parameters are associated with some shifting in the global circulation patterns. Effects of other factors such as land use change, increase of population and other non-climatic factors on such trends can not however be discounted.