DISPUTING complaints it did not give timely warnings to low-lying communities, the National Irrigation Administration (NIA) said on Tuesday it had warned residents in the low-lying areas near the Magat River that the Magat Dam would release water to ease pressure on the reservoir in anticipation of Typhoon Rosita’s expected rainfall.
NIA-Magat River Integrated Irrigation System Department Manager Wilfredo Gloria told the BusinessMirror that the agency followed the necessary protocols prior to releasing water from the dam.
“Six hours prior to the release of the water, we have already informed the concerned people that the dam would be releasing water. That’s already a built-in protocol between the NIA and the concerned local government units,” Gloria said in an interview on Tuesday.
Before then, the NIA had not responded to queries from BusinessMirror’s Isabela correspondent, who documented the release of the huge wall of water that swamped some low-lying villages in at least three Isabela towns: San Mateo, Aurora and Roxas.
On Tuesday, however, Gloria claimed that prior to the release of the water, they had told the Office of Civil Defense, the Provincial Disaster Risk Reduction and Management Office, provincial government, municipal government and barangay officials.
People are informed through text messages, radio broadcast, television and even via print, he added.
Furthermore, the NIA also includes, as part of protocols, the sounding of sirens along the Magat River. Gloria said this could be heard by residents in the largest tributary of the Cagayan river.
“This has been our protocol ever since. Six hours before releasing water, especially when there is additional volume, we ring the siren,” he said. “We always look after the welfare of our downstream residents,” he added.
Gloria explained that the they opened one spillway gate of the Magat Dam on October 29 to maintain the reservoir’s storing capacity and preempt the inflow of water due to Typhoon Rosita.
“Prior to arrival [of Typhoon Rosita], we opened one unit just to draw it down. Just to bring it to safe level to accommodate the volume of rainfall,” he said.
Since then, the NIA decided to open one gate after another as the inbound water kept rising until Magat Dam peaked at seven open spillway gates on the morning of October 31.
After Typhoon Rosita exited the Philippine area of responsibility, Magat Dam shut down its spillway gates one after the other as well, according to Gloria.
“We slowly terminated the gates until only one spillway gate was left open at 0.5 meters for standby purposes,” he said.
Magat Dam closed all its spillway gates on November 4 at 11 p.m., according to Gloria. Water level at the Magat Dam has returned below its spilling level of 193 meters.
Magat Dam had a peak reservoir inflow of about 5,859 cubic meters per second on October 30 while it had a maximum outflow of 4,392 cubic meters per second on October 31 noon, according to Gloria.
Magat Dam’s water volume peaked on November 1 at 5 p.m. at 193.24 meters, which is above its spilling level, Gloria added.
From October 30 until November 4, Magat Dam had a total water inflow of about 639.43 million cubic meter, while it recorded a total outflow of 368.725 million cubic meter, Gloria said.
Reports received by the BusinessMirror indicated that residents of low-lying towns near Magat Dam in Isabela were stunned last week by the sudden wall of water that came rampaging their way after Typhoon Rosita had exited.