Lake Opuha reaps a rich winter harvest
A rich snow harvest in the Fairlie basin is providing an unexpected windfall for lowland farmers needing Lake Opuha to fully recharge for the next irrigation season.
After being closed to irrigators in February, the lake reached ‘‘zero storage’’ for the first time in 17 years and was slow to return to its normal levels over autumn.
The lake will be boosted by the initial snow melt in the lower basin, with water levels expected to continue rising as deeper snow in the Two Thumb Range thaws in spring, but more water is needed for it to totally refill.
Opuha Water chief executive Tony McCormick said the big snowfall had given farmers some confidence that lake levels would return, but they were not out of the woods yet.
‘‘We copped it as good as anyone, and the Fairlie basin has had quite a bit of snow, and this has given us a bit of heart.
‘‘It’s very difficult to quantify, as there are two lots of snow – the stuff which will melt over the next seven to 10 days, which is good, because our current level is well below average for this time of the year. We also have the snow up on the hills, which is water in the bank.’’
Opuha’s level is at 34 per cent, when it would typically be 64 per cent at this time of year.
‘‘That shows we are by no means out of the woods yet, and prior to last week things were get- ting pretty dry again as the inflows were dropping and the lake was levelling out, and this will keep the lake filling,’’ McCormick said.
Opuha managers need an average winter with average rainfall for the lake to become completely full. The snow over the past week is expected to provide 10 per cent of its total water needs.
The lake take had dropped to 1 per cent each week in early June.
McCormick said Opuha’s fill period was usually autumn and spring, with winter providing bonus recharging.
The lake was still reliant on the spring thaw, and there would be concern if it was not at 85 per cent of its total by September, he said.
There had been good thawing conditions during the day for lowland snow, although colder nights might slow this down, McCormick said. A layer of 400 millimetres fell around the lake, with about a metre on upper parts of the Two Thumb Range.
McCormick said lake managers were not overly confident of the lake returning to its full state, as droughts often followed droughts and weather forecasters were indicating that an El Nino might bring dry conditions again.
He said plans has been made to introduce early conservative management if the lake was full at the start of the irrigating season, so supply could be sustained to the 250 irrigators in the Opuha Water scheme.
Opuha had been this low for June only once before, in 2001, McCormick said.