The San Roque reservoir has a large holding capacity of 525 million cu. m. active storage and 120 million cu.m. flood surcharge where inflow during heavyrains are stored and gradually released downstream. This attenuates the perennial flooding of the river.

If necessary, during extreme flood events, the Flood Forecasting and Warning System for Dam Operations (FFWSDO) of the National Power Corporation (NPC) in coordination with the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), regulates the volume of water to be released by specifying the appropriate spillway gate openings to SRPC based on extensive meteorological and flow gauge data transmitted to the dam via redundant communication systems.