Opening of Wawa Dam in Rizal helps stop more Metro flooding

RESERVOIR This aerial photo shows the floodwaters entering the Upper Wawa Dam reservoir in Rodriguez, Rizal, and how the dam’s controlled impounding system reduced the impact of flooding caused by Supertyphoon Carina (international name: Gaemi) last week. —WawaJVCo Inc.

LUCENA CITY, QUEZON, Philippines — The timely inauguration of the Upper Wawa Dam reservoir in Rodriguez town of Rizal province early this month saved some areas in the province and Metro Manila from worse flooding during last week’s onslaught of Supertyphoon Carina (international name: Gaemi) and enhanced southwest monsoon or “habagat.”

“If without it (dam), I feel like most likely San Mateo and Montalban would be down and definitely Marikina and parts of Quezon City and even Pasig would be affected because of Laguna Lake,” Rizal Gov. Rebecca Ynares told President Ferdinand Marcos Jr. during the situation briefing in San Mateo town on Friday, said a report from the Presidential Communication Office on Saturday.

According to Ynares, it was expected that it would take six months before the dam would be filled. But due to the heavy rainfall from Carina, the reservoir was nearly filled in just two days of heavy rains.

READ: Marcos calls for more impounding systems to curb flooding

During the briefing, Rizal Rep. Jose Arturo “Jojo” Garcia Jr. also told Marcos that if it were not for the dam, there would still be flooding in the National Capital Region (NCR).

The President has been conducting meetings with local government officials during his ocular inspection in typhoon-hit areas.

Water security

National Irrigation Administration Administrator Eduardo Guillen, in a Bagong Pilipinas Ngayon briefing on Thursday, also cited the role of the Upper Wawa Dam in alleviating the impact of severe flooding in NCR Manila during the typhoon.The Upper Wawa Dam reservoir was built by Prime Infra-led WawaJVCo Inc. to meet the increasing demands of Metro Manila for clean water and amid concern that the Angat Dam in Bulacan province could no longer meet the water needs in NCR.

The Upper Wawa Dam is set to start supplying bulk water to Metro Manila by the end of 2025.

In his speech during the ceremonial start of the impounding process of the Upper Wawa Dam on July 10, Marcos said the dam would ensure the water security of Metro Manila and surrounding areas, as it was the biggest water source to be built in the country in over 50 years, next to the Angat Dam.

“While designed as a water supply dam, the project can also help mitigate flooding in downstream communities, particularly low-lying areas in Rizal province and the eastern district of Metro Manila,” said a statement from WawaJVCo Inc.

Bulk water

After the briefing, Marcos directed a study on the building of weirs along tributaries to control the water flow from Sierra Madre down to Rizal and Metro Manila. The unimpeded water flow causes severe flooding during the rainy season, according to the President.

A weir is a small barrier built across a stream or river to control and raise the water level slightly on the upstream side, essentially a small-scale dam. It is used to prevent flooding, measure water flow, and hold water. The impounded water can be used in towns, homes, industry or irrigation.

Public Works and Highways Secretary Manuel Bonoan disclosed plans to build a series of small dams below the Upper Wawa Dam to impound floodwater.

WawaJVCo Inc. said it will continue collaborating with its host communities to help strengthen resilience against future weather-related challenges.

Nilo Tamoria, Department of Environment and Natural Resources director in Calabarzon told the Inquirer on Sunday that they also “acknowledged the assistance of projects like this (Upper Wawa Dam) in preventing the flooding caused by bad weather.

He added: “We must also ensure that there is a corresponding effort to enhance the forest and reforestation program to more effectively mitigate the impact of typhoons and heavy rains on watersheds like UMRBPL (Upper Marikina River Basin Protected Landscape).”