Heavy rains brought by the southwest monsoon caused flooding in parts of Bulacan on Saturday night, including the overflow of the Marilao River, while the water level at Angat Dam remained below its operating level.

Data from the Provincial Disaster Risk Reduction and Management Office showed Angat Dam’s water elevation dropped to 167.80 meters as of 6 a.m. Sunday from 168.10 meters the previous day. The dam’s minimum operating level is 180 meters.

PDRRMO chief Manuel Lukban said the decline was recorded despite scattered heavy rains across the province.

Marilao Mayor Jem Sy said the river overflowed Saturday night, prompting several residents to evacuate. Floodwaters later subsided, allowing evacuees to return home.

Angat Dam in Norzagaray supplies about 97 percent of Metro Manila’s potable water.