The level of New Zealand’s largest hydro storage lake — Lake Pūkaki — is above the 91-year average for the first time since May, Meridian Energy said yesterday.
Lake Hāwea, which feeds the Roxburgh and Clyde power stations on the Clutha River, has had an increase of storage of 78% in the past four weeks, rising about 2m.
It is now back to average storage.
Lake Manapouri which feeds the Manapouri power station was sitting at 179.23m, which was sightly above its maximum operating range.
Meridian wholesale general manager Chris Ewers said, in a statement, the rain missed in April to August finally arrived in September.
"We’ve been managing our hydro lakes extremely carefully for months now, but there’s nothing like a helping hand from Mother Nature."
Lake Pūkaki had been below average for more than 150 days, and at historically low levels as recently as mid-August, before weeks of heavy rain and snowfall changed the outlook. Over the last week Pūkaki rose 715mm to just over 525m above sea level — 102% of average for this time of year.
"The last few weeks have more than exceeded our expectations," Mr Ewers said.
"September felt wet, and it was. The Waitaki catchment, which feeds Lake Pūkaki and the Waitaki hydro scheme, had its fourth-wettest September on record."
But it is not just water in the lakes that is welcome. In the mountains above the Waitaki catchment, snow storage is now sitting at 117% of average.
"That’s great news for later in the season as that snow melts and feeds the lakes throughout the warmer months. After a challenging winter, we couldn’t have asked for a better start to spring."
The historical average level of Lake Pūkaki changes over the course of the year, and spring is generally when levels are at their lowest due to high demand for electricity and less rainfall throughout winter.
Contact Energy hydro head of generation Boyd Brinsdon said inflows were low during winter, down to below 300 cumecs in 110 days over winter.
But September had been really wet and that had led the Clyde Dam spilling water for most of the last month.
The dam could not generate all the water coming through the dam, so some of it had to go down the spillways. It was not quite enough to lead to flushing further down the river in the Roxburgh Gorge. The company was also carrying out some work at the Roxburgh Dam.
Flushing helps shift sediment which may lead to floods.
Mr Brinsdon said the snow pack was also looking good for the Lakes Hāwea catchment.
He said the higher storage levels allowed more renewable generation to be used and not rely as much on gas-powered generation.
The ongoing favourable conditions continue to ensure wholesale prices — also known as spot prices — are kept in check.
The average North Island price was down $5 to $78 per megawatt hour and the average South Island price was down $5 to $69, Meridian said.
