‘Bising’ may force Magat Dam to extend spilling ops

MANILA – Downstream communities of Magat Dam in Northern Luzon must prepare for the possibility that this facility’s ongoing spilling operation may last for several days.

Typhoon Bising (international name Surigae) is heading towards waters east of Northern Luzon and may bring this week rain that can increase Magat’s inflow so there’s possibility for the dam to extend its spilling operation, noted Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) hydrologist Edgar dela Cruz on Tuesday.

“With increased inflow, Magat may need to continue spilling so its water won’t rise to the normal high water level there,” he said.

He noted Magat keeps its water below the normal high to ensure the integrity of the dam’s structure.

Earlier, PAGASA hydrologist Richard Orendain recommended preemptive evacuation of residents in Magat Dam’s downstream communities along Magat River.

These residents must move to safer ground as Magat Dam might eventually intensify its spilling operation, he noted.

“If it’ll rain hard there because of ‘Bising,’ prompting the need for Magat Dam to increasingly spill water, that’ll raise the risk for flooding downstream,” he said.

Residents concerned must also temporarily stop their activities in or along Magat River, dela Cruz noted.

“The river’s strong current can carry them away,” he said.

He said the current there can be three times stronger when Magat Dam releases water.

PAGASA reported Magat Dam’s 6 a.m. water level on Tuesday at 190.22 meters, just 2.78 meters below the normal high.

Magat’s water rises easily since this small dam receives a lot of runoff from rain over its large basin, dela Cruz noted.

“Even light rainfall causes Magat’s water level to already react,” he said.

Dela Cruz said Magat has opened one of its gates at a height of 1.0 meter to release excess water.

He isn’t discounting the possibility of Magat spilling for about two to three days depending on the dam’s inflow.

“Magat must maintain a safe water elevation,” he said.

According to PAGASA, Magat Dam’s latest spilling operation was from March 25 to 27 this year.

PAGASA said Magat conducted such an operation due to the surge in the northeast monsoon or “amihan”.

In its 11 a.m. severe weather bulletin on Tuesday, PAGASA located “Bising” some 475 kilometers (km) east of Infanta municipality in Quezon province as of 10 a.m.

“Bising” was slowly moving north-northwestwards, packing maximum sustained winds of 175 kilometer per hour (kph) near its center and gustiness of up to 215 kph.

PAGASA forecast “Bising” to be 340 km east of Tuguegarao City in Northern Luzon’s Cagayan province by Wednesday morning (April 21).