Meridian is being forced to drain water from depleted hydro lakes to generate power in order to take up the slack from generation facilities which are off-line for maintenance.

This comes as lakes Tekapo and Pukaki sit at levels which have prompted one electricity industry consultant to suggest a low-level power-saving campaign be prepared and implemented if they fail to rise soon.

Meridian spokesman Alan Seay said yesterday that the company continued to drain water from Pukaki and Tekapo, which between them account for 55 per cent of national storage capacity, to generate electricity. About 600 megawatts of thermal generation capacity from the North Island was off-line for maintenance, he said.

Power industry consultant Bryan Leyland said that with the thermal down, there was no alternative but to use hydro-electric generation.

"We've run out of reserve capacity," he said.

Lake Tekapo yesterday sat at 705.175m above sea level, about 40% full and at 63% of its average for this time of the year.

Lake Pukaki was at 521.696m above sea level, about 25% full and at 48% of average for this time of the year. -- NZPA