The local government of Rizal province said the operations of the Wawa Dam was a key factor in reducing the impact of the flooding caused by typhoon “Carina” last week.
Rizal Governor Nina Ynares said in a statement without the project, flooding in certain areas of the province could have been significantly worse particularly in low-lying areas and the eastern district of Metro Manila.
The water supply dam is composed of the Wawa bulk water supply project and its second phase, the Upper Wawa Dam, which began impounding its reservoir on July 10.
Ynares said the it takes six months for Upper Wawa Dam’s reservoir to fully impound water.
However, the dam was nearly filled in just two days with the heavy rainfall Typhoon “Carina” enhanced by the southwest monsoon.
“…Without it, most likely, San Mateo and Montalban would be down; and definitely, Marikina and parts of Quezon City and even Pasig would be affected,” Ynares said, in a report to President Ferdinand Marcos Jr.
The Upper Wawa Dam features a reservoir of about 450 hectares, approximately twice the size of Bonifacio Global City and can store up to 120 million cubic meters of water.
It is the largest dam to be built in over 50 years with the critical objective of addressing water supply security in Metro Manila and the province of Rizal.
Based on measurements conducted throughout July 24, floodwater entering the dam’s reservoir peaked at approximately 2,100 cubic meters per second (m³/s).
The controlled impoundment successfully managed the discharge downstream to approximately 200 m³/s, significantly lessening the impact of the floods.
The Upper Wawa Dam reservoir also accumulated over 90 million m³ of water during the super typhoon.
The Upper Wawa Dam is set to start supplying bulk water by the end of 2025 which is a project of WawaJVCo Inc., a subsidiary of Prime Infrastructure Holdings Inc.
Upper Wawa Dam’s 710 million liters per day (MLD) capacity is also seen to reduce Metro Manila’s reliance on the existing Angat-Ipo System.
WawaJVCo has an existing 30-year offtake agreement involving the supply of 518 MLD from Upper Wawa Dam’s 710 MLD to Manila Water, leaving 192 MLD of available excess raw water supply.
