The Ipo Dam in Bulacan on Sunday afternoon opened one gate to discharge water in preparation for possible heavy rain from a potential cyclone that entered Philippine territory Saturday afternoon.

Philippine Atmospheric Geophysical and Astronomical Services Administration (PAGASA) hydrologist Gene Nievares said the dam was discharging water at 47.9 cumecs (cubic meters) per second.

"Ginagawa ito in preparation for tinatawag na effect ng active low-pressure area. Ginawa ito para ma-accommodate ang rainfall na maibibigay ng ALPA for the next days," she said in an interview on dzBB radio.

Earlier, PAGASA said the ALPA may intensify into a cyclone this week and enhance the southwest monsoon, which in turn will bring rain to parts of the country.

PAGASA's Flood Forecasting and Warning Section said on its Twitter account that one gate of Ipo Dam was open at 0.3 meter as of 1 p.m.

As of 6 a.m., Ipo's water level was 100.64 meters, up from 100.52 meters on Saturday. This was slightly below its 100.80-meter high level.

"Kailangan bigyan ng malaking espasyo ang ALPA para sa darating na araw (We have to give leeway for the ALPA's rain)," Nievares said.

She added the enhanced monsoon is likely to bring rain to the western side of Luzon.

"'Yan ang precautionary measure, nagbibigay ng espasyo para sa incoming na ulan ng ALPA," she said.

Meanwhile, Nievares said the La Mesa Dam in Quezon City remained on red alert Sunday, though its water level had gone down to 79.77 meters, below the overflow level of 80.15 meters. — LBG, GMA News