San Roque dam release hardly felt
SAN MANUEL—With two typhoons – ‘Pedring’ and ‘Quiel’ – pummelling Luzon and dumping heavy rains within one week, the San Roque Multi-purpose Dam Project (SRMDP) here opened one of its six spillway gates by one-half meter at 12 noon of September 29.
Dam authorities explained that the spill from San Roque was a preemptive move to avoid a sudden discharge that could bring about a flash flood as it did in 2009 when the water release destroyed the flood control dike in Carmen, Rosales and other parts of Pangasinan, devastating residential houses, business establishments, and agricultural farms.
Tom Valdez, vice president for corporate social responsibility of San Roque Power Corporation (SRPC), the company operating the dam, said with one gate open, the water released downstream was only 72 cubic meters per second, equivalent to about 360 drums of water per second.
Bell Connel, SRPC senior vice president for operations and site administrator, echoed that the opening of one of six gates of the dam just by one-half meter will have insignificant effect in the lowlands of Pangasinan.
As of Friday, there was reportedly a minimal rise of water downstream of Agno River Valdez stressed there is no way that the water released from the dam could reach Dagupan City, which is already under water in many parts.
The flood warning system of the Philippine Atmospheric Geo-sciences Astronomical Services Administration (PAGASA) reported that water slightly rose by 0.3 meter in Sta. Maria town section of the Agno River.
As of 9:00 a.m. Friday, the SRMD reservoir had an elevation of 280.90 masl, just .90 meter higher than the critical level of 280 masl.
Total outflow of water from the dam was 333.78 per second. Of this, 72 cubic meter per second was attributed to the opened one gate of SRMDP by one-half meter.
WITNESS
The opening of the San Roque dam gate was witnessed by newsmen and representatives of the provincial government, including Sixth District Provincial Board Member Ranjit Ramos Shahani and Provincial Information Officer Butch Velasco, to ensure that protocol was being observed to avoid a repeat of the 2009 disaster.
When Gate 4 of SRMDP was opened, the water elevation at SRMDP reservoir was 279.96, masl, just 0.4 meter below the critical level of 280 masl.
With three gates of Binga dam opened by six meters, the inflow of water was 1,091 cubic meters per second, more than the outflow of 260 cubic meters per second.
Aside from Binga dam, the Ambuklao dam also opened two gates early last week. Both dams spill water into San Roque.
In generating 407 megawatts of power for the Luzon Grid, San Roque is discharging 260 cubic meters of water from its turbines.
Virgilio Garcia, area chief of the Agno River Flood Forecasting and Warning System of the National Power Corporation (NPC), said it will take four to five hours for the water released from the dam to reach Carmen, Rosales and another six to seven hours to reach Lingayen Gulf.
Garcia said people near the downstream portion of the Agno River were adequately informed before they opened the gate.
The Agno Flood Forecasting and Warning System has 18 warning stations downstream of the Agno River and all these, except two which are defective, were used to sound the alarm of the incoming release of water from the dam.
Garcia said the gate will remain open depending on the volume of rain that typhoon Quiel will bring over the weekend.
The NPC and the SRPC continue to provide the Provincial Disaster Risk Reduction and Management Council (PDRRMC) an hourly update on the elevation of the dam.
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