(Updated 9:57 a.m.) - Following heavy rain since Sunday, Ipo Dam in Bulacan province opened one of its gates early Monday to release excess water.
The National Disaster Risk Reduction and Management Council advised residents near Angat River to take precautions for an increase in water levels.
"The water release from Ipo Dam is expected to affect the low-lying areas along Angat River from Norzagaray to Hagonoy. Residents in the area are advised for possible increase in the water level downstream," it said
It said the Ipo Dam's opening was by 30 cm as of 6:30 a.m.
As of 6 a.m. Monday, the Philippine Atmospheric Geophysical and Astronomical Services Administration said Ipo Dam's water level was at 100.83 meters
, a sudden 0.87-meter jump from 99.96 meters 24 hours earlier.
According to PAGASA hydrologist Roy Badilla, the water released from Ipo Dam's opening was at 47.9 cubic meters per second as of 8 a.m.
"Medyo maliit lang compared sa capacity," Badilla said, noting that the tolerable flow for Angat River is at 800 cubic meters per second.
Badilla said that except for Ipo and La Mesa dams, the other major dams are far from spilling level. He said La Mesa dam is currently at 79.79 cubic meters per second, and will overflow if the water level reaches 80.15.
Badilla explained that when excess water is released, residents in the area will experience an increase in the water level downstream.
"Tataas nang kaunti ‘yung tubig. Depende sa labas ng tubig kung gaano kataas," he said.
In a later interview on GMA News' News to Go on Monday, however, Badilla said the water level at Ipo Dam is already decreasing. "Medyo bumababa na nang kaunti mula noong mag-open sila kaninang umaga," he said.
"Ang ine-expect lang natin ay baka magkaroon tayo ng minor flooding. Ito ay sanhi ng mga local rains hindi dahil sa pagpapakawala ng tubig sa Ipo," he said.
Meanwhile, the Provincial Disaster Risk Reduction and Management Councils (PDRRMC) in Aurora is monitoring Central and Northern Aurora for possible bad weather.
PDRRMCs in Bulacan and Zambales are also monitoring their areas of responsibility. –With report from Carmela Lapeña/KG, GMA News