2009 lessons helped Pangasinan deal with new floods
DAGUPAN CITY—Had it not been for the gradual release of water from San Roque Dam in San Manuel, Pangasinan, the province would have stood on the brink of another disaster similar to what it suffered during the massive flooding in 2009.
But it took the provincial government a lot of prodding before the National Power Corp. (Napocor) finally opened the dam’s spillway gates on the night of Aug. 2, when the dam’s water elevation was about
4 meters short of its spilling level of 280 meters above sea level (masl) amid continuous and heavy rains in northern Luzon.
The Napocor owns the dam, while San Roque Power Corp. maintains and operates it.
Frantic calls
“We called [the dam operators] every day,” said provincial administrator Rafael Baraan.
As a result, despite the rains dumped by the southwest monsoon in the province in the last two weeks, only a few villages in five Pangasinan towns and this city were flooded.
Baraan said if the dam did not release water early on, it would have reached its maximum elevation of 290 masl by now.
“And with the nonstop rains, Napocor will have to open all its spillway gates again,” Baraan says.
In 2009, the dam was blamed for flooding 38 towns and cities in the province that destroyed some P4 billion worth of crops, fish, roads, bridges and dikes after Napocor’s dam operators opened all of the dam’s six spillway gates when it was about to reach its full capacity.
“We have learned our lesson, that’s why we are monitoring the dam closely, just like what we have done last year,” Baraan said.
Minimum impact
On Tuesday, the provincial disaster risk reduction and management council (PDRRMC) reported that only the towns of Dasol, Aguilar, Bugallon, Calasiao and Sta. Barbara, and Dagupan City experienced flooding because of storm surges and high tide.
With intense rain predicted to fall over Pangasinan on Wednesday, the provincial government asked local officials to prepare for emergency and to conduct preemptive evacuation, especially of residents along Agno River and the two river systems of the province.
On Tuesday night, Napocor also increased the opening of the dam’s two spillway gates to a total height of 2.5 m to release water at 658 cubic meters per second (cms). The dam’s elevation at that time was 282.81 masl, still 2.82 m above its spilling level.
But the provincial government was not impressed. Baraan said Napocor continued to defy the dam discharge protocol that was agreed on in 2009.
Protocol shunned
He said the protocol clearly stated that San Roque Dam should start spilling water at 280 masl.
“We have asked them to increase the amount of water they are releasing to provide space for the increased inflow in the coming days, but they do not follow us,” said Baraan.
Rosales Mayor Ricardo Revita said residents in his town were alarmed after provincial officials announced that San Roque’s operators did not follow protocol on the release of excess water.
Revita said he received calls and text messages from residents asking if the town would again experience heavy floods. Rosales was one of the worst hit towns in 2009 when San Roque Dam opened all its gates and released 5,300 cms of water that flooded Pangasinan for several days.
During a PDRRMC meeting on Tuesday, officials expressed frustration when the dam operators did not open more spillway gates when the dam’s water level reached almost 284 masl.
“Maybe the dam’s operators did not follow protocol, but there is no cause for alarm yet. If there was a violation, provincial officials should just have called up San Roque Dam officials to avoid raising alarm among the people,” Revita said.
Napocor speaks
Virgilio Garcia, Napocor hydrologist, said dam operators were following the protocol in water releases.
He said that even before the water elevation reached
280 masl, Napocor had started to open the gates.
At 10 p.m. of Aug. 2, when water elevation reached
276.66 masl, the dam opened a gate by half a meter to release a total of 330 cms. At that time, water entering the dam reached 1,345 cms.
Two days later, the dam’s water level reached 282.38 masl and the opening was increased by another half meter.
Garcia said the level between 280 and 290 masl was the “flood control” level of the dam. This 10-m elevation can contain 125 million cubic meters of water, he said.
“Maybe they are thinking that we are not allowed to go higher than 280 masl,” he said.
He said Napocor opened all of the dam’s gates in 2009 when water elevation hit 286 masl due to heavy rains dumped by Typhoon “Pepeng.”
Garcia said: “I may have a different decision if I were the hydrologist then. But whatever the decision, the result could still be massive flooding because of the unprecedented amount of water brought by Pepeng.”
San Roque Dam, which is located downstream of the Agno River, catches water released from the Binga Dam in Benguet and runoff water from the Cordillera and Caraballo mountains.
