Monday, November 11, 2013

Angat Dam breaches 213 meter level, spills water

By Dino Balabo

Angat Dam's spillway as photographed by Napocor while discharging water on Sunday.

MALOLOS CITY—Water elevation at the Angat Dam climbed to 213 meters above sea level (masl) on Sunday, leading the National Power Corporation (Napocor) to discharge water through its spill way for the first time this year.

This came a day after Super typhoon Yolanda move out of the Philippine Area of Responsibility (PAR) but left heavy rainfall infl ow into the dam reservoir.

Gladys Sta. Rita, president of the Napocor, told PromdiNews that Angat Dam started discharging a total of 190 to 200 cubic meters per second (cms) of water. She said that Napocor opened its floodgate by one meter to discharge at least 130 cms through its spillway.

In addition to that, Napocor is also discharging 61 cms through its tunnels to power its hydroelectric turbines that generate electricity. As of yesterday morning, water discharged by Napocor through Angat Dam’s spillway was raised to 265 cms, while Bustos Dam on the Angat River downstream is discharging 285 cms.

The discharge through the dam’s spillway is the first this year, after months of clamor from Bulacan officials for Napocor to start “pre-emptive release” of water. On Saturday, water elevation at the dam climbed to 211.25 masl, but Engineer Rodolfo German said they would not spill water yet.

German is the general manager of the Angat River Hydroelectric Power Plant (ARHEPP) of the Napocor which manages the Angat Dam. German later said that they can spill water anytime, while the Napocor central office issued an advisory within the next 24 hours as they monitored situation at Angat Dam.

Based on data gathered by PromdiNews on Saturday, Yolanda’s rains left an infl ow of at least 568 cms, while the regular discharge of Angat Dam towards Ipo Dam is only 61 cms. This means more than 500 cms of inflow that caused water elevation to climb.
Angat Dam's spillway. Photo from Tonkin & Taylor
Yesterday, the inflow dropped to around 300 cms, and water elevation dropped to 213.51 masl from Sunday’s 213.65 masl. As this develop, the Provincial Disaster Risk Reduction Management Offi ce (PDRRMO) of Bulacan allayed fears of possible floods.

Liz Mungcal of the PDRRMO said that the 130 cms discharge to Angat River is almost negligible noting that there is not much rains in the last 24-hours and that rivers are shallow because of low tide. For his part, Engineer Precioso Punzalan of the National Irrigation Administration (NIA) said that Bustos Dam can accommodate water spilled from Angat Dam.

Operated by NIA, Bustos Dam is an after bay regulator dam of the bigger Angat Dam. Punzalan said they have been discharging 60 to 90 cms from Bustos Dam since Thursday in preparation for the Angat Dam discharge.

On Saturday, Gov. Wilhelmino Alvarado expressed disappointment over the refusal of Napocor to spill water despite the fact that its 210 spilling level was breached on Friday night. But Napocor officials like Engineers Romualdo Beltran and Russel Rigor explained that the 210 masl is not their spilling level but the normal high water level during flood season.

As head of the Dams Management Division of the Napocor, Beltran noted that the month of November normally marks the end of rainy season and the start of the summer. However, he said that Napocor is also considering typhoons that can hit the country between the end of November to December and January next year.