The Waitaki River flow is expected to fall this week as Meridian Energy Ltd reduces the amount of water being released from over-full storage lakes.
However, how quickly that will change depends on rainfall in the upper Waitaki catchment and inflows into Lakes Pukaki and Tekapo.
The Waitaki River has been running high for the past five days, increasing from about 220cumecs on April 28 to a peak of 1403cumecs on April 30-May 1.
Yesterday, it was still running at about 720cumecs.
The average daily mean flow is about 350cumecs.
Heavy rain in the upper catchment a week ago boosted storage lake levels beyond their maximum operating levels, forcing Meridian to release water.
Meridian external relations manager Claire Shaw said yesterday that, taking into consideration market demands and competition from other generators, as much surplus water as possible was being used to generate electricity.
"We are now seeing inflows receding and we expect the Waitaki River to trend downwards this week, but still remain high," she said.
The release from Lake Pukaki had been cut back, but not that from Tekapo.
Yesterday, Meridian was releasing 80cumecs from Tekapo, 300 from Pukaki, 180 from Benmore, 270 from Aviemore and 230 from Waitaki.
Releases from Lake Ohau had ceased.
That put the lower Waitaki River at about 720 cumecs.
Lake Tekapo yesterday was at 711.123m above sea level (masl), still above its maximum operating level of 710.9masl.
Lake Pukaki was 532.559masl (532masl maximum operating level) and Lake Ohau 520.327masl (520.4masl).
Lakes Benmore, Aviemore and Waitaki, which are operational and not storage lakes, were also above their maximum levels.
