Water may have to be spilled today from Lake Benmore as Meridian Energy Ltd manages high lake levels in its Waitaki storage lakes.
However, it will be nowhere near the levels Meridian spilled for 48 hours in January, and will make no marked difference to the current flow of the lower Waitaki River.
Yesterday, the river was running up to 500cumecs, compared with its average flow of about 350cumecs.
A $67 million refurbishment of the Benmore power house, which has taken two of its six turbines out of action, is causing a bottleneck in clearing water through the Waitaki hydro system from the Pukaki and Tekapo storage lakes.
Both are almost full after heavy rain last weekend.
Meridian's external relations manager Claire Shaw yesterday said the company was trying to manage water from the storage lakes as efficiently as possible by using it to generate electricity through the five power stations in the upper Waitaki power scheme, which feed into Lake Benmore.
If spilled directly from Lakes Pukaki and Tekapo it would by-pass power stations, losing the potential generation.
By generating through the upper Waitaki system, Meridian was able to manage the present in-flows into the two storage lakes.
Yesterday, the level of Lake Tekapo was steady and that of Pukaki was increasing marginally.
Lake Tekapo was just below its maximum operating level and Lake Pukaki slightly above.
However, with two turbines undergoing an overhaul at the Benmore power house, Lake Benmore was approaching its maximum operating level.
There was more water going into the lake than was coming out.
"We may have to spill water from Lake Benmore down the spillway to maintain its level," Ms Shaw said yesterday.
"It is better to spill at Benmore than it is from Tekapo and Pukaki, by-passing generation in the upper Waitaki."
Any spill would be tightly controlled, at "moderate levels" and about equal to what would be going through the two turbines if they were generating.
"It would be nothing like the flushing flows [in January]. It will be moderate spills to keep the level right," she said.
The flows from Lake Benmore through the Aviemore and Waitaki power houses to the lower Waitaki River could be managed by generation.
