The reservoir supplies about 90 percent of raw water requirements for Metro Manila through the facilities of the Metropolitan Waterworks and Sewerage System and it irrigates about 28,000 hectares of farmland in the provinces of Bulacan and Pampanga.

Angat Dam has a normal high water level of 210 meters, according to the Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa).

[3] In the early 1990s, the Philippine government and Metropolitan Waterworks and Sewerage System studied tapping the Umiray River basin in General Nakar, Quezon as an additional source for the Angat Dam Reservoir, as the growing population of Metro Manila pushed the demand for potable water up.

The UATP involved constructing a 13 km 4.3 meter diameter diversion tunnel which channeled the headwaters of Umiray River at its intake point to Macua, in Doña Remedios Trinidad, Bulacan, providing an additional 300 mld to the Angat Dam Reservoir.

[8] Emma hit Central Luzon in 1967, passing through the Angat Hydro-Electric Project and Dam of the National Power Corporation (NPC or Napocor) in Norzagaray.

This resulted in the inundation of several towns in Bulacan near the dam; the hardest-hit was Norzagaray, where about 100 residents died and million of pesos worth of properties were destroyed.