The Waitaki hydro storage lakes are virtually full after heavy rain at the weekend and, if there are further downpours, Meridian Energy Ltd may have to consider spilling water again.
Over three days at the weekend about 270mm of rain fell at the head of Lake Tekapo, and at 709.678m above sea level it was full, and still rising.
Lake Pukaki at 531.893m above sea level was 99% full.
Rain was still falling yesterday, although expected to ease later in the day, and had yet to reach the lakes.
There had been very little rainfall in the Manapouri catchment.
Meridian's external relations manager Claire Shaw said yesterday no decision had been made on whether water would have to be spilled from the lakes.
"There is a chance we may have to spill, but it is hard to predict at this stage because we don't know what in-flows are still to come and whether another rainfall event on Thursday will have an effect," she said.
If water had to be spilled, it would be tomorrow or Thursday and probably from Lake Tekapo, although Miss Shaw emphasised a decision still had to be made.
"We are doing everything we can to manage the in-flows over the next few days - we are not in the habit of spilling water," she said.
Another northerly weather pattern was predicted for Thursday, which could bring more rain.
Depending how much was forecast, water might have to be spilled.
"It's only a chance, but we can't decide until we see the full effects of the current rainfall and what is predicted.
"On the flip-side, we are certainly in a better position [with lake levels] than we were last year.
"That can only be a good thing," she said.
In January, Meridian spilled water from Lakes Tekapo and Pukaki for 48 hours, with 950cumecs, compared with its normal average of 380cumecs, flowing down the Waitaki River.
