MANILA - The National Irrigation Administration said Sunday it warned residents of Cagayan and Isabela of Magat Dam's water release two days prior Typhoon Ulysses' landfall on Nov. 11.
The water release and rainfall from nearby provinces caused "unprecedented" floods and killed at least 9 in his province, Cagayan Governor Manuel Mamba had said.
The dam's water level is at 192.15 meters as of 6 a.m. Sunday, close to its spilling level of 193 meters, the NIA said in a statement.
It said the NIA-Magat River Integrated Irrigation System (NIA-MARIIS) used different mediums such as TV, radio, print, social media, emails, text messaging, and sirens to disseminate information on Magat Dam and its water releases.
"All stakeholders are kept posted and updated as to the actual scenario of the water volume that may be flowing into their place on an hourly basis through SMS," the NIA said.
The NIA-MARIIS was in "close coordination" with local disaster officials, Office of Civil Defense, state weather bureau PAGASA, Regional Agricultural Fisheries Extension Network group and other concerned local government offices "prior, during and after water releases."
"Officials have warned residents living near low-lying areas, particularly those adjacent to and along Magat River and Cagayan River to move to higher and safer places as the dam continues to release water starting November 9," it said.
Prior to Typhoon Ulysses, 5 storms brought "continuous rain for almost two months" in Luzon, prompting Magat Dam to open 2 gates equivalent to 4 meters of water level to reduce water, the NIA said.
"It is necessary to release water from the reservoir for purposes of preventing the dam from reaching its critical level of 193 msl that may compromise its structural integrity and may result (in) a catastrophe to nearby municipalities and more impact on a widespread flooding in Region II (Cagayan Valley)," it said.
"The continuous rains upstream of Magat Dam contributed to high inflows, while rivers along the Cagayan River had also reached its maximum capacity, causing river overflows, not only to the Cagayan River but its adjacent areas."
Magat Dam is a catch basin of 8 upstream rivers while the Magat River is only 1 of 18 river tributaries which can delay the surge of floodwater through the dam, the NIA said.
"With the Magat Reservoir and Magat Dam to regulate the gush of water from these sources, flash flood and greater flooding at low-lying areas, which could have caused greater damage to life and property, is minimized, if not prevented," it said.
The NIA urged residents to "stay vigilant and take appropriate action" against landslides and flashfloods most especially in the prevalence of COVID-19 pandemic."
Mamba earlier said residents were warned but the volume of water that descended onto the province was the worst in 4 decades.
He acknowledged it is standard operating procedure for dams to release water, but he lamented the "very short notice" for it.
"I think this is also caused by the management of their watershed, dahil 'pag dumating na yung tubig kaagad-agad, nire-release nang maramihan din. I think pati ang watershed nila dyan inabuso din po nila, kaya we are suffering because of that. We don’t get any advantage for any drop of water dyan," he told ABS-CBN's TeleRadyo on Sunday.
(I think this is also caused by the management of their watershed because when water arrives, they release it immediately. I think their watershed is abused and we are suffering because of that.)
"Masakit po ang loob namin dyan. But I think, kapabayaan po lahat ng ito at abuso sa inang kalikasan ito and now we are suffering. I hope this will be a lesson to have a holistic approach on how to solve our problem," he added.
(It hurts us but I think everyone is liable for this and the abuse of mother nature and now we are suffering.)
Mamba said he intends to invite experts to help them out as far as lessons learned from the present calamity and give them advice on what to do next.
Ulysses (international name: Vamco) first hit land in Quezon province on the night of Nov. 11, and crossed Luzon island westward, leaving at least 67 people killed and causing heavy flooding in Marikina City and parts of Rizal province, aside from the northern provinces of Cagayan and Isabela.
It left the Philippine area of responsibility in the morning of Nov. 13.