Opening of Magat Dam gates not major cause of Cagayan, Isabela floods —NIA

National Irrigation Administration chief Ricardo Visaya on Tuesday maintained that the opening of the water gates of Magat Dam was not the major cause of the flooding in Cagayan and Isabela.

Visaya made the remark during the House joint panel probe into the massive flooding in many areas in the Cagayan Valley Region during the onslaught of Typhoon Ulysses.

During the inquiry, Visaya presented a matrix which showed that from November 9 to 14 amid the typhoon, the peak water inflow at Magat Dam was at 7,128 cubic meters per second but the dam released only at 6,706 cubic meters per second.

Meanwhile, the water level at Buntun Bridge, which measures the water level of Cagayan River, was at 13.2 meters, he added.

Based on this matrix alone, Visaya said it could already be concluded that the opening of the water gates of Magat Dam was not the major cause of the flooding in Cagayan and Isabela.

"Can we draw now a conclusion from this matrix? Yes. Is it really Magat Dam that provided or the major cause of the flooding in Cagayan? I don't think so," he said.

"Nakita natin, it's very clear that 'yung contribution ng Magat Dam sa flooding ng Cagayan was not really the major cause," he added.

Visaya also assured that concerned offices and individuals who may be affected by the release of water are warned ahead of time before the release of the water from Magat Dam.

"Six hours before release, activate the warning stations. As much as possible, hindi tayo magre-release ng tubig in any dam after 5 o'clock. Ang tina-target natin dito 3 o'clock. We are giving a lead time to all concerned including government offices, LGUs, radio stations, et cetera, six hours para makapag-react sila," he said.

"Redundant ang pag-iinform natin dito. And it is followed by a black and white document. Lahat ng LGUs pumipirma nito. Kaya hindi nila masasabi na hindi sila nai-inform because we have the documents," he added.

At the same time, Visaya said that the release of water from Magat Dam was done gradually and not all at once.

"During the typhoon, [there is] regulation of outflow from the dam to mitigate damage to the downstream. Nire-regulate 'yan. Hindi ibig sabihin na during that time, biglang nag-release. Mali 'yun," he said.

For instance, on November 9, the first water gate was opened by only one meter at 3 p.m., followed by another gate at 5 p.m., Visaya said.

By November 12, more water gates were opened due to the increasing inflow at the dam, but this was reduced by 4 a.m. the following day," he added.

"Imi-mitigate natin 'yung tubig na nanggagaling sa dam. In mitigating, the outflow will be lower than the inflow. Malakas lang talaga ang tubig during that time," he continued.

Other factors

Visaya said the massive flooding in Cagayan and Isabela could have been prevented had there been better implementation of anti-illegal logging, mining and quarrying activities.

"We have to look into the other factors that could have contributed to the flooding of Cagayan. Kung ini-implement lang nang mabuti ang anti-illegal logging activities, 'yung sa illegal mining, illegal quarrying, maybe we can prevent the flooding of Cagayan River," he said.

Visaya earlier said that the gates of Magat Dam had to be opened amid heavy rains from the typhoon to prevent the dam from breaking and causing a bigger catastrophe.

"Ang laki ng ating reservoir ng Magat [Dam] is about 4,800 hectares. 'Pag ito ang na-break, lumampas sa spilling level na 193 meters above mean sea level, mag-spill po 'yan. Masisira po 'yan at milyon-milyon po na tao ang maaapektuhan," he said. 

Typhoon Ulysses has left 73 people dead and 69 others injured, and affected more than 4 million individuals or 995,476 families families, according to the National Disaster Risk Reduction and Management Council.

President Rodrigo Duterte placed the entire Luzon under state of calamity following the onslaught of typhoons Rolly and Ulysses. —KG, GMA News