MARAMAG, Bukidnon (MindaNews/31 December) — The National Power Corporation released a total of 42 million cubic meters of water from its Pulangui IV dam on December 27 and 28 following the flash floods in Valencia City, the “highest spillage so far in Pulangui history,” plant manager Engr. Rudy Brioso said.
Forty-two million cubic meters is equivalent to the water consumption of Davao City’s 250,000 households for 5.6 months at one cubic meter per day per household. It is also equivalent to 16,800 Olympic-size pools at 2,500 cubic meters each.
Brioso told MindaNews the release was regulated and was not expected to cause flooding downstream in Cotabato. But flooding incidents in some downstream areas along the Pulangui River were reported by the National Disaster Risk Reduction and Management Council (NDRRMC) although damage was not extensive and no one was reported killed.
Brioso said Pulangui Dam did not collapse contrary to rumors that spread through text and the media and caused panic downstream. MindaNews visited the plant and the dam afternoon of December 28 and saw water being released from a bottom sluice and two of its seven spillways.
But Brioso acknowledged that Tuesday’s water inflow in its 2,000 hectare reservoir was “the highest we have encountered” and the water they released this week was also the “highest spillage so far in Pulangui history, attributed to the flashfloods in San Fernando and Valencia plains.”
“I believe this is the first we experienced since the start of the plant operation,” Brioso told MindaNews. The plant, capable of generating 255 megawatts but operating at a maximum load of 180 mw, was commissioned in December 1985.
Brioso said they released water “moderately” because of the “sudden increase” in elevation of the National Irrigation Administration’s (NIA) diversion dam in Lumbayao, San Fernando town early morning of December 27. Continuous rains triggered by a low pressure area caused the “sudden increase” and unleashed flash floods, hitting badly Valencia City. The floods displaced 1,150 families living along the Pulangui River in the city. Some 200 residents had to be rescued by helicopters.
Brioso said the diversion dam’s normal water level is half a meter but it reached three meters on Tuesday. The floodwaters reaching the Pulangui IV reservoir raised its water elevation as well, prompting Brioso to order the release of water downstream.
The NDRRMC report as of 8 a.m. December 31 said there was flooding downstream, in two villages in Quezon town, Bukidnon “ because of heavy rains and overflowing of flood water in Pulangi river.”
Flashfloods were also reported in Barangay Buluan, Kabacan, North Cotabato affecting three sitios “because of heavy volume of water coming from Pulangi River in Bukidnon.” A total of 800 families or 40,000 persons and one mosque were affected but as of December 29, the floodwater had “partially subsided but affected/ displaced families still remain at the evacuation centers.”
The NDRRMC reported seven barangays affected in Maguindanao’s Datu Montawal and Pagalungan town were flooded but as of December 29, “floodwater in the municipality of Montawal is gradually subsiding and no displacement or casualty has been reported.”
Text messages claiming the Pulangui Dam had collapsed and a huge volume of water was on its way to Cotabato triggered panic downstream and prompted local government units to order forced evacuations.
The city government of Cotabato evening of December 27, ordered a forced evacuation of some 200 families in Punol Island and warned residents along the riverside, particularly the Rio Grande de Mindanao. as the Spanish colonizers renamed the downstream part of the Pulangui River, to be ready.
In Pikit, North Cotabato, residents along the Pulangui also fled to higher grounds.
The NIA diversion dam in Lumbayao, which channels water from the Pulangi River to another irrigation district was not destroyed by floodwaters, contrary to reports. But a siphon facility in Barangay San Isidro, Valencia City, which diverts water from the Pulangi to irrigation canals, was.
San Isidro barangay captain Henry Ladesma showed MindaNews the siphon that slammed into a concrete pylon of the Pulangui Bridge. “Nag-shake itong bridge” (the bridge shook), Ladesma said. Notices were immediately rucks are no longer allowed to pass there. .
Brioso said they released water from the dam “moderately” otherwise Maramag would be flooded and delikado pud sa Cotabato side” (and it would be dangerous on the Cotabato side),” he said.
Pulangui River flows into the Ligawasan marsh which is composed of three separate marshes, Ligawasan, Libungan and Ebpanan which in turn flows into the Rio Grande de Mindanao (the downstream part of Pulangui River) and into Cotabato City. The Presidential Task Force for the Mindanao River Basin Rehabilitation and Development (PTFMRBRD) in a June 2011 report described the flow of the waters, thus: “These marshes, defined only during the dry season, combine as the entire Ligawasan marsh during the rainy season. The Ligawasan and Libungan marshes empty into the Ebpanan marsh which in turn flows into the Rio Grande de Mindanao whose only two outlets are in Cotabato City.”
Brioso said Chief Insp. Supt. Felicisimo Khu, chief of the Directorate for Integrated Police Operations (DIPO)-West was in touch with him and informed him morning of December 28 that the water released the day before had not reached Cotabato and had not been felt in Cotabato.
Brioso acknowledged that the flooding on December 27 in Valencia City, was “unusual.”
He said Pulangui Dam’s maximum water elevation is 285.5 meters but he issued an order to keep to the level of 285.2 meters “to anticipate more water (from the flash floods) and to enable us to cope up.”
He said they could not go beyond the maximum level otherwise their equipment would be destroyed.
“Hapit wa mi kaoperate kay napuno” (We almost didn’t operate because it was full), he said.
Engr. Jing Natividad, senior engineer at Pulangui IV told MindaNews that based on their records, from 1 a.m. to 12 midnight of December 27, the water spilled was 21.6 million cubic meters or 900,000 cubic meters per hour. From 1 a.m. to 12 midnight, total water spilled was 20.631 cubic meters or about 860,000 cubic meters per hour.
For two days, the water released was 42 million cubic meters, higher than the daily average during the May—June flooding in Cotabato City which PTFMRBRD June 17 report said was aggravated by emergency releases of water from Pulangi IV “totally around 98 million cubic meters in 20 days” or an average of 4.9 million cubic meters a day.
Brioso told MindaNews that spillway gate 4 was closed at 9:30 p.m. on December 28 while spillway gate 2 was closed at 12:30 a.m. on December 29 “so for now practically all the gates are already closed.”
Brioso said the 2.000 hectare reservoir can carry 67 million cubic meters of water but because of the silt, it can hold only 35 to 40 million cubic meters. The total volume of water released in two days – December 27 and 28 – was 42 million cubic meters.
To appreciate how big that volume of water is, the average consumption of all households in Davao City is about one cubic meter per day. That is equivalent to 1,000 liters or five drums of 200 liters. If it were drinking water, that’s good for 21 million households for one day. Davao City has about 250,000 households. That water will be enough for 84 days of consumption by all households in the city. At 42 million, that would be 168 days or 5.6 months.
The 42 million cubic meter water is enough to fill 16,800 Olympic-size pools, at approximately 2,500 cubic meters each. (Carolyn O. Arguillas/MindaNews)