RAMON, Isabela: The rising volume of water on the rivers of Magat and Cagayan is threatening to submerge low-lying cities and municipalities in Isabela and Cagayan provinces, the Office of the Civil Defense (OCD) Region 2 warned on Monday.
Dan Villamin, officer of OCD-Region 2, said they have alerted officials of the two cities and 17 municipalities in Cagayan and Isabela to mobilize their respective disaster management councils for necessary precautions.
He identified the affected areas in Isabela as Ilagan City, Gamu, Tumauini Delfin Albano, Santo Tomas, Cabagan, Santa Maria and San Pablo. As well as Tuguegarao City, Enrile, Solana, Iguig, Amulung, Alcala, Gattaran, Lallo, Lasam, Baggao, Camalaniugan and Aparri of Cagayan province.
“We have warned residents in these cities and municipalities to be always vigilant and heed the warnings by authorities to avoid untoward incidents caused by flashfloods,” Villamin said.
The warning was issued as National Irrigation Administration-Magat River Integrated Irrigation System (NIA-MARIIS) announced that Magat Dam reservoir has reached its critical and spilling level, prompting a need to release water.
NIA-MARIIS Department Manager Wilfredo Gloria said the Magat reservoir elevation as of 12:00 noon on Monday was at 193.17 meters, slightly above the 193 meters critical and spilling level.
A continued discharge of water from the Magat Dam needs to be done to relieve the aging dam structure and in anticipation of more rainfall that may come in the days ahead, he said.
“The swelling of the dam’s major sources like the Ibulao River in Ifugao and the Magat River in Nueva Vizcaya due to continued downpour since the onslaught of typhoon Nona is causing the rise in water level at the Magat Dam,” Gloria said.
He said water outflow at 1,610 centimeters, which required the opening of four of the seven units spillway gates at seven meters, will affect low lying areas along the Magat and Cagayan rivers.
“We also rely on several automatic rain gauges installed upstream at the watershed areas of the dam where data are registered and transmitted to the control system of the reservoir,” Gloria added.
Warning devices have also been installed downstream as a mechanism to warn the residents around and within the low-lying areas of Magat River to be prepared to leave anytime the dam reservoir is supposed to release stored water.
Magat Dam is a large rock-filled dam by the river at the boundary between the municipalities of Alfonso Lista in Ifugao province and Ramon in Isabela.
It was the largest dam in the Philippines back in 1983, the year it was built. It now generates 360 megawatts of electricity (with a water head 81 meters high) and supplies irrigation water for about 85,000 hectares of farmland in Isabela and surrounding areas.
The dam and its watershed are managed by the NIA. The National Power Corporation (NPC) managed the hydroelectric plant before the plant was turned over to SN Aboitiz Power Inc. in April 2007 as part of the privatization of power plants under the Electric Power Industry Reform Act (EPIRA) of 2001.