30 August 2018
Napocor terminates water spilling operations at San Roque dam
After containing huge water inflows from five successive typhoons and rains from enhanced southwest monsoons
The National Power Corporation (Napocor) on Thursday announces the closing of all spillway gates of San Roque dam after it reached the target elevation of below 275 meters above sea level (masl).
As of 8 AM today, the dam’s elevation is at 274.62 masl. Its normal high-water elevation (NHWL) is 280 masl.
Napocor’s Dams Management Department (DMD) said that the target elevation will give leeway for future water inflow especially during another tropical depression.
The corporation also emphasized the flood mitigating function of dams which helped hold and control huge amount rainfall from going straight to the Agno river and nearby towns.
Water discharge in brief
It can be recalled that the San Roque dam started its spilling operations in the morning of 12 August 2018 when its elevation breached the NHWL of 280 masl. Water elevation peaked at 287.19 masl on August 14, 2018 due to the continuous large inflows from heavy rain caused by Tropical Storm Karding and the enhanced southwest monsoon (habagat). Spilling of water from Ambuklao and Binga dams which cascades to San Roque dam also contributed to the increased elevation.
For the next ten days, spilling operations continued to avoid overflow and to allow sustained decrease in reservoir water elevation until it reaches the target elevation of 275 masl.
However, the declining elevation stalled at 276.28 masl on 24 August due to the moderate rainfall brought about by Tropical Depression Luis which also increased the water discharge of upstream dams Ambuklao and Binga.
San Roque dam’s elevation peaked at 281.00 masl in the morning of 27 August, thus the continued water spilling operations. It finally attained target elevation on 30 August at 8:00 AM.
Napocor said that few weeks prior to Typhoon Karding, the Ambuklao, Binga and San Roque dams already contained massive amount of rainfall and water inflow brought about by Tropical Storms Henry, Inday and Josie in North and Central Luzon.
Dams for flood control
Napocor said that apart from power generation, dams likewise have flood control and mitigation functions, preventing loss of life and property caused by massive flooding. Dams impound floodwaters and release them under control to river or store them for other uses like irrigation.
“We continually monitor the inflow of water to the reservoir and the PAGASA reports so as to be on guard on the dam’s situation,” said Napocor’s DMD Chief Conrado Sison.
Napocor assures the public that the corporation, along with the San Roque Power Corporation who operates the San Roque hydropower plant and SN Aboitiz Power who operates Ambuklao and Binga hydropower plants, strictly complies with the coordination protocol on dam operations as contained in its Dam Safety Program. END