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Explained: Why Magat Dam Released So Much Water to Cagayan

It's a familiar dilemma for dam operators.
by Ara Eugenio
Nov 16, 2020
Photo/s: Twitter/Philippine Coast Guard

Days before Typhoon Ulysses arrived, the operators of Magat Dam in Isabela confronted their dilemma: whether or not to release water. Should they release water and flood riverside communities or risk the dam breaking which could lead to a catastrophe.

An aerial survey before the storm on Nov. 8 showed that holding water in could cause the dam to break, said Eden Selva, spokesman of the National Irrigation Administration that manages the reservoir. At that time, Magat's water level was one meter shy of its spilling point.

"Dapat po makapagpakawala na tayo ng tubig bago ma-reach kasi po delikado, mako-compromise yung ating structural integrity. Baka pag may dam breakage po tayong mangyari, mas malaking pinsala ang mangyari," she said.

Water from Magat Dam, seasonal monsoon rains and rainwater from surrounding waters caused the unprecedented floods in Isabela that chased thousands to their rooftops where they pleaded for help using the hashtag #CagayanNeedsHelp.

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Protocols were followed

Selva said the water release followed protocols, contrary to observations that it was done in haste. The NIA coordinated with PAGASA on the potential effects of the storm, Selva said.

Six hours before the first dam discharge, a first warning is released via radios, fliers, and coordination with concerned government agencies in the area. This includes the Office of Civil Defense and the Regional and Provincial Disaster Risk Reduction Management Offices who are then expected to coordinate with local government units, she said.

"Gaya ng binabanggit namin, hindi lang NIA gumagawa ng warning kundi along the route ng Magat river, pagpasok niyan sa Cagayan River confluence, kasama na ang at local NDRRMC sila na po yung nagbabahay-bahay para masabihan ang mga communities. May megaphones po at sirens," she said. 

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What went wrong?

According to residents, they were made aware of the water release, corroborating NIA's claims. However, the amount of water and how it would completely submerge their houses was unexpected

In an interview with ANC's Headstart, Vice President Leni Robredo said the incident should be investigated to prevent it from happening again.

"It was a confluence of many factors.. Question ko sa kanila, meron bang existing estimate kung halimbawa, one gate yung bubuksan, alin yung may danger of flooding. At least yung mga city councilors I was with, di nila alam. They were not aware if there was such an estimate. Para sakin kailangan may ganon eh," Robredo said.

At the height Typhoon Ulysses on Nov. 12 and until the next day, Magat Dam had seven gates open, discharging 6244 cubic meters of water per second.

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Cagayan River is a catch basin not only to Magat dam, but also to water flowing from nearby provinces such as Isabela, Nueva Vizcaya, Quirino, Ifugao, and Kalinga. Due to the series of typhoons that came prior to Ulysses, the river was already swollen and its soil's resolve already weakened due to saturation. It couldn't absorbed any more water, hence the flooding. 

Magat's releases exacerbated this problem, said Cagayan Gov. Manuel Mamba.

According to NIA, "climate-resilient" dikes for Magat dam should be in place to account for the effects of climate change.

"Ang pakiwari ko po ay coordination. Coordination by different government offices na talagang maibigay kung ano yung tamang info at arrangement kung sino talaga magsisignal. Kasi ganoon din noon, na bleblame yung NIA kasi alam ng tao dahil dam yan, kami may hawak," Selva said. 

Selva said NIA was still clarifying their agency's role in disaster prevention and response. "Inaaral pa ng NIA yan kung ano pinakamabuti," she said. 

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In the interview with Teleradyo, Selva claimed that the directive on whether or not they should be releasing water comes from PAGASA.

A PAGASA hydrologist, Maximo Peralta, said the decision is still with NIA. "Hindi naman talaga kami ang mag-uutos sa kanila. Hindi nga talaga namin ang alam kung ano po ang nangyari doon. Pero dahil naging protocol ay magpapadala kami sa kanila ng info sa kanila, in a subtle manner, tinatanong rin namin kung okay ba yung mga equipment nila, and if it can withstand the typhoon,"Peralta told reportr.  

Tuguegarao City Mayor Jefferson Soriano was under fire last week for going out of town for a birthday trip. He said this was because no storm signal was raised in their area. 

There have been repeated calls to create a separate disaster department. Robredo told ANC there was a risk of adding  "another unnecessary layer to the bureacracy."


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"Baka it would be worth studying the existing agencies, ano ba yung kakulangan nito. kung may kulang baka kaya ng legislation, ng any other means, kung hindi na talaga pwede edi idissolve, gumawa ng bago," she said.

"Ito yung nirereklamo nila [Isabela] Governor Albano na andami-daming agencies na gumagawa ng kanya-kanya. Itong working in silos makes it very difficult to harmonize the policies of these many agencies having specific roles that sometimes contradict each other," she said.

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