THE continuing two to three-hour daily rotational brownouts in General Santos City and in other key cities in Mindanao will not likely end any time soon after the island's power deficit rose to 159 megawatts (MW) on Thursday.

The National Grid Corp. of the Philippines (NGCP) said Mindanao grid's available capacity had dropped to 1,021 MWs from the 1,094 MWs generated by the existing operational power resources last Monday.

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Although the island's peak demand dropped to 1,180 from the 1,210 recorded last Monday, the significant reduction in Mindanao grid’s available power capacity caused the increase of the previous supply deficit of 116 MWs to 159 MW.

Regional corporate communications officer Belinda Canlas of the NGCP said "the shutdown of power plants, the increase in power demand among customers, and the dry weather of the El Niño have been limiting the available capacity or supply in the power system."

The company said in Visayas and Mindanao, the electricity supply generated from power plants continued to be low and might not be enough to meet the demand of power grid users.

Last Monday, NGCP said the Agus 5 hydroelectric power plant was placed on maintenance shutdown but its Unit 1 was already synchronized with the Mindanao grid as of February 16 and is now undergoing testing.

The diesel-fed Power Barge 117’s Unit 2 was also placed under maintenance shutdown and will not be operational until March 1.

"Because of the lean power reserves, the system may be forced to implement load curtailment among Visayas and Mindanao grid users to ration the available power and to ensure the reliability and stability of the entire transmission network," the NGCP said.

Rodolfo Ocat, general manager of the South Cotabato Electric Cooperative (Socoteco) II, earlier warned that the continuing daily rotational brownouts may extend until June due to the significant drop in water reserves of Lake Lanao in Lanao del Sur and the Pulangi River in Bukidnon.

He said the drop in the water levels was attributed to the onslaught of the prolonged dry spell, or the El Niño phenomenon in the area.

The Lake Lanao-Agus River System and the Pulangi River host the National Power Corp’s main hydropower plants that generate the bulk of Mindanao grid's power supply requirements.

Ocat said the power cooperative, which needs at least 106 MWs of power supply during peak hours, had been voluntarily shedding a significant load from its daily supply requirement in the wake of ongoing power supply shortage.

Socoteco II serves General Santos City, the entire Sarangani province and the municipalities of Polomolok and Tupi in South Cotabato.