The development of new water sources to ensure more stable water supply for Metropolitan Manila is urgently needed especially with the changing climate. The objectives of this study are: 1) to develop hydrological models in 3 river basins (Angat, Kaliwa and Pampanga) surrounding Metro Manila; 2) to assess basin-scale hydrological impacts of climate change in terms of a) flooding trends and b) drought trends. Calibrations of the basins were performed in Angat dam inflows for Angat basin; and Pantabangan dam, Cabanatuan, Zaragoza, San Isidro and Arayat stream flows for Pampanga river basin. Soil moisture verification of Pampanga river basin utilized monthly surface soil moistures from both the LDAS-UT and hydrological model outputs in short vegetation areas. Incorporating bias corrected rainfall and other parameters from GCMs showed future flooding trends is virtually certain to increase while drought trends are as likely as not to increase in the uplands but very likely to increase in the flood plains.