MANILA -- The water level at La Mesa Dam, which supplies water to Metro Manila, has slipped to its lowest in 21 years, the state weather bureau said Thursday.

As of 6 a.m. the dam's level was at 68.74 meters, said PAGASA hydrologist Sonia Serrano.

The dam's last record low was 68.75 meters in 1998, during an El Niño phenomenon, she told ABS-CBN News.

The latest reading has breached the critical level of 69 meters.

The dam's level is expected to dip further with rains currently drenching only parts of Mindanao, said Serrano.

A weak El Niño is affecting the country, with the dry season expected to start in the fourth week of March, PAGASA earlier said.

The dip in La Mesa Dam's level has prompted water concessionaire Manila Water to cup supply in the east zone of Metro Manila, bringing misery to tens of thousands of customers.

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