The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) on Friday, Sept. 13 said Magat Dam in Isabela has opened two gates to manage the reservoir’s rising water level amid heavy rains caused by the southwest monsoon (habagat) and the trough of Tropical Storm “Bebinca.”
In a press conference, PAGASA Hydrologist Rosalie Pagulayan said Magat Dam’s water level has reached 188.21 meters as of 11 a.m.
“At this time, the water discharge is being tapered off to stabilize the elevation in preparation for the additional rainfall that is expected to increase the water level at Magat Dam,” Pagulayan said in Filipino.
Magat Dam may only 20 millimeters of rainfall to reach its normal high water level of 190 meters.
Pagulayan explained that with the forecast of 15 to 40 millimeters of average basin rainfall over the next 24 hours, Magat Dam could reach the normal high water level, prompting the current gate openings.
She said only one gate was opened the previous day, but as of 10 a.m. on Friday, two gates have been opened to a height of 1 meter each, with an estimated discharge of 378 cubic meters per second.
Pagulayan added that while the Magat River can accommodate a discharge of 378 cubic meters per second, PAGASA has issued a hydrological situation report for Magat Dam detailing what residents can expect over the next 24 hours.
In the report, communities along the Magat River that may be affected by Magat Dam’s release of water are the municipalities of Ramon, San Mateo, Aurora, Cabatuan, Luna, Reina Mercedes, Burgos, Naguilian, and Gamu, all in Isabela province.
She advised the concerned local government units and communities along the river to temporarily halt activities along the Magat River.
Meanwhile, Pagulayan said there has been no announcement yet regarding gate operations for the Ambuklao and Binga dams in Benguet but the areas near these dams are already in the flood precaution phase.
She said both Ambuklao and Binga dams are approaching their normal high water levels but most of the water that will be discharged will be captured by the San Roque Dam in Pangasinan.
The Ambuklao-Binga-San Roque cascade includes these three dams.
Pagulayan said that San Roque Dam may need 500 millimeters of rainfall if there are no discharges from Ambuklao and Binga.
However, if Ambuklao and Binga are already full, San Roque may require only 170 millimeters of rain.
For Angat Dam in Bulacan, reaching the normal high water level of 210 meters requires 560 millimeters of rainfall, and it is still considerably short of this level, Pagulayan said.