The water level (WL) of Angat Dam continues to decline despite the El Niño already in its weakening phase.

On Monday, its reservoir WL was recorded at 180.73 meters (m), a -0.22 reduction from its 180.95 WL the previous day.

The minimum operating level of Angat Dam, which supplies raw water to the majority of Metro Manila areas and irrigates some farm areas in Bulacan and Pampanga, is 180 m.

"Hopefully, the rains will continue in the watersheds so that our reservoir level will increase,” said Engr. Patrick Dizon, spokesperson for the Metropolitan Waterworks and Sewerage System (MWSS).

“What we really need is the fall of rain and the storm to refill our reservoirs,” he added.

Despite this, Dizon said that its WL is still sufficient to meet local demands but noted it still needs to be preserved until the rainy season comes.

Lowered daily WL decrease

Meanwhile, Dizon said isolated rains that occurred on Sunday helped to minimize the daily average WL decrease in Angat Dam.

“In the past few days, our reservoir was lowered by 40 to 50 centimeters per day, but because of the rain yesterday, it lowered the daily average decrease of our water in the reservoir—from 40 to 50 centimeters per day, the Angat Dam dropped yesterday by just 16 centimeters,” he said.

Moreover, Dizon said that the reservoir elevation of Ipo Dam and La Mesa Dam increased by 5 cm due to the rains.

“Since our reservoirs are already saturated, if it continues to rain in our watersheds, we expect the water in our reservoirs to increase,” he said.

Rainy season onset

The Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA) said last week that the scattered rains experienced in the country in the past days can be an indicator of the possible onset of the rainy season.

According to PAGASA Climate Monitoring and Prediction Section chief Analiza Solis, the onset of the rainy season as forecasted by their agency is between 1 and 15 June or the last week of May.

She noted that there is still a probability of more than 15 percent or a slim chance of the rainy season's delayed onset.

PAGASA issued last March a La Niña watch, signifying that there is a level of more than 55 percent of its occurrence in the next six months.