RAMON, Isabela – The water releases from Magat Dam during the height of Typhoon Ulysses last week was crucial to maintaining the integrity of the reservoir and preventing even more devastating floods, the National Irrigation Administration (NIA)-Magat River Integrated Irrigation System flood forecasting chief here said on Monday.
“The gates of Magat Dam had to be opened since last week because of heavy rains from Typhoon Ulysses to prevent the dam from breaking. In fact, we have been preventing a bigger catastrophe so we released with seven gates opened on November 12,” Engineer Carlo Ablan, head of the flood forecasting and dam instrumentation division of NIA-Magat, told the Philippine News Agency in a phone interview.
Ablan said if Magat Dam’s water breaches the spilling level of 193 meters above mean sea level, it might result in breakage of the reservoir, that would cause even more devastating floods.
“It would mean damage and millions of affected so it is better to release (water). We maintain a standard safety level and a normal inflow and outflow,” he explained.
Magat Dam’s seven gates were opened on Nov. 12, releasing water volume equivalent to 106.223 Olympic-sized swimming pools, or around two swimming pools per second during the height of heavy rains spawned by Typhoon Ulysses.
Ablan said they issued an advisory regarding water releases on Nov. 10, or two days before the actual opening of the dam’s gates.
He also clarified that they stopped releasing after 5 p.m. in compliance with their agreement with the provincial disaster risk reduction management offices of Isabela and Cagayan.
Magat Dam, a large rock-fill dam in Isabela, is located on the Magat River, a major tributary of Cagayan River.
Records showed the construction of the dam started in 1975 and was completed in 1982.
Built to last for 50 years, Magat Dam is one of the largest in the Philippines. It is a multi-purpose dam that is used primarily for irrigating about 85,000 hectares of agricultural lands, flood control, and power generation through the Magat Hydroelectric Power Plant. The water stored in the dam’s reservoir is enough to supply about two months of normal energy requirements.
However, siltation and sedimentation had increased in the reservoir even as slash-and-burn farming, illegal logging and fish-caging had resulted in the deterioration of the dam’s watershed.
The 1990 Luzon earthquake also reportedly contributed to the increased siltation in the Magat River system. (PNA)