Strengthening Angat Dam, Metro’s source of water

Published February 8, 2018, 12:05 AM

by Mario Casayuran and Vanne Elaine Terrazola


Mayon Volcano’s continued activity reminds us that we are in a part of the planet that is under constant pressure from forces beneath the earth’s surface that could explode in deadly violence at any time. It has now been weeks since Mayon erupted with ash clouds and sent rivers of lava flowing down to communities at its base.

Volcanoes are part of the Ring of Fire in the lands around the Pacific Ocean, with the Philippines at its western side. We also have an abundance of geological faults where land masses are constantly grinding against one another in the bowels of the earth all over the Philippine archipelago. One of these is the West Valley Fault that begins in Central Luzon, goes through eastern Metro Manila, on to Cavite and the rest of Southern Luzon.

Because the West Valley Fault has a recorded history of exploding into catastrophic earthquakes about every 400 years, and the last major earthquake was in 1658, 360 years ago, it is feared that a major earthquake with a magnitude of 7.2 could come at any time. This would be the “Big One” for which Metro Manila and the nearby provinces of Bulacan, Cavite, Rizal, and Laguna have been holding “Shake Drills” for several years now.

Of special concern to the government is the state of Angat Dam in Bulacan which supplies irrigation water to farmers in 20 towns of Bulacan and Pampanga. It also generates electric power for the Luzon Grid. And it is the source of Metro Manila’s water supply. The Metropolitan Waterworks and Sewerage System (MWSS) draws water from Angat, courses it through two tunnels to Ipo Dam, on to the millions of homes and factories in Metro Manila.

The MWSS announced early this month that the Angat Hydropower Corporation is now in the process of strengthening the dam at a total cost of R533.3 million, along with the National Power Corporation and the provincial government of Bulacan.

Part of the West Valley Fault cuts right through the eastern area of the body of water behind Angat Dam and Angat Dyke. There is, therefore, a very real danger of dam water cascading and flooding the surrounding land in case of severe seismic activity. But of greater impact in case Angat Dam breaks would be the loss of Metro Manila’s source of water supply.

This is why we welcome wholeheartedly the work being done to strengthen Angat Dam and Angat Dyke. We are doing well in attending to the needs of the people around Mayon and we are undertaking annual drills to prepare the people of Metro Manila in case the long-feared “Big One” earthquake finally strikes. We are truly glad that the government is strengthening Angat for the first time since it was built in the 1960s.