MANILA (2nd UPDATE) – State weather bureau PAGASA on Thursday warned of possible flooding as major dams in Luzon were expected to rise due to Typhoon Ulysses.

Quezon City's La Mesa Dam is currently spilling over after reaching its capacity of 80.15 meters, water concessionaire Manila Water said in a 10 a.m. advisory.

The excess in supply is expected to affect the low-lying areas along Tullahan River from Quezon City (Fairview, Forest Hills Subdivision, Quirino Highway, Sta. Quiteria and San Bartolome); Valenzuela (Barangay Ligon, North Expressway, La Huerta Subdivision); and Malabon.

“All the residents living in the aforementioned areas, especially those near the river banks or in the floodplains are advised to be alert for possible flooding,” PAGASA said.

Meanwhile, the reservoir water level in Angat Dam in Norzagaray, Bulacan has reached critical level, the National Power Corporation (NPC) said.

The dam was to open its spillway gates with an initial gate opening of 0.5 meters at 10 a.m. to bring it down to a safe level.

"Due to the release of water, the water level and flow in the Angat river is expected to rise. Please be on alert and take necessary precautions," NPC said.

Angat Dam breached its 210-meter capacity, with its water level at 211.30 meters at 6 a.m.

PAGASA said the water level in Ipo Dam, also in Bulacan, reached 101.20 meters at 6 a.m. Thursday, surpassing its spilling level of 101 meters, the agency said.

Residents living along the low-lying areas and those near the river bank of Angat River from Norzagaray, Angat, San Rafael, Bustos, Baliuag, Pulilan, Plaridel and Hagonoy are advised to be on alert for possible flooding, including flash floods.

The weather bureau also reported the Caliraya Dam in Laguna was already nearing its spilling level of 288 meters. As of 6 a.m., the dam’s water level stood at 287.95 meters.

PAGASA hydrologist Richard Orendain, in an interview on ABS-CBN's TeleRadyo, said dams would be releasing water continually to preserve its structural integrity and avoid a dam burst.

• Typhoon Ulysses weakens, set to exit Luzon

According to PAGASA's 11 a.m. advisory, the Philippines' 21st storm has crossed over to the West Philippine Sea, somewhere west of Zambales province, after making several landfalls over the Luzon landmass.

Ulysses' strength has weakened to 130 kph maximum sustained winds and gusts of up to 200 kph.

Watch more in iWantv or TFC.tv