PAGASA on Sunday announced that Ipo Dam in Norzagaray, Bulacan started releasing water at midday.
This is due to the high water level in the dam following heavy rainfall caused by the Southwest Monsoon (Habagat).
At 12 noon, the water level was at 101.30 meters, which is already above the dam’s normal high water level (NHWL) of 101 meters.
Water was released from the dam at 12:29 p.m. 
“IPO Dam Management conducted spilling operation at 12:29pm with approximate discharge of 40.8 cms,” PAGASA announced at 1 p.m.
The weather bureau earlier said Ipo Dam’s water level at 7 a.m. was 100.56 meters.
At 6 a.m., it was at 100.51 meters, an increase of 0.79 meters over the level at 6 a.m. on Saturday, 99.72 meters.
Dam updates as of 6:00 AM, 25 July 2021
— PAGASA-DOST (@dost_pagasa) July 24, 2021
However, the water level in Ipo Dam was still expected to rise on Sunday as more rains fall.
“IPO Dam Management will conduct spilling operation at 12:00nn with approximate initial discharge of 38 cms,” PAGASA earlier said.
It advised residents in low-lying areas and near the Angat River bank from Norzagaray, Angat, San Rafael, Bustos, Baliuag, Pulilan, Plaridel and Hagonoy to be alert.
PAGASA earlier said monsoon rains will continue to be experienced in Metro Manila, Bulacan and other areas on Sunday as Typhoon In-Fa (formerly known as Fabian) and Tropical Storm Nepartak, which are both outside the Philippine Area of Responsibility, enhance the Southwest Monsoon. —KG, GMA News