Restrictions likely until irrigation season ends, Opuha chief executive warns
Irrigations restrictions for users of South Canterbury's Opuha Dam could last until the end of the irrigation season.
Opuha Water Limited chief executive Tony McCormick says a 50 per cent restriction on water use from the manmade lake is likely to remain in place through all of January.
"I envisage that there will be some level of restriction in place for the remainder of the season," McCormick said on Monday.
National Institute of Water and Atmospheric Research (NIWA) charts suggest rainfall in much of South Canterbury reached near normal levels in December after months of below average rainfall.
However, McCormick said water inflows were the "key parameter" for managing the lake.
"What is very obvious to us is that this season's inflows are down considerably compared with last season."
Inflows to the lake in November averaged 3.91 cubic metres per second compared to 5.39 cumecs last season. December's average inflows averaged 2.56, compared to 3.36 in 2014.
The lake's level was about 386 metres on Tuesday, which McCormick said was about 25 per cent higher than for the same time last year, when the lake's low level led Minister for Primary Industries Nathan Guy to use it as a backdrop for the declaration of a drought in the region.
McCormick said the company had been able to release smaller volumes of water into rivers downstream sooner in the season than it did last year.
"We have actually had river restrictions in place continuously since last season although there were quite long periods in the off-season when the river was operating naturally above the minimum flow even though we were maintaining absolute minimum releases from the dam to try and build the storage.
"The support of the OEFRAG [Opuha Environmental Flow Release Advisory Group] group has been absolutely crucial in getting us to this point."
Opuha Water had also started irrigation restrictions sooner than it did in 2014, he said.
Although the lake had an extra three weeks' worth of water stored compared to 2014, McCormick said the situation was "no less serious" than last year, when irrigation was shut off completely.
Opuha Water would try to avoid a total shut down and try to keep river flows higher in Autumn "to improve the conditions at an important period for fish and river ecology", he said.
NIWA soil moisture records suggest although fields in some parts of South Canterbury are less dry than on the same day in 2015, soil moisture levels remain below historical averages.
Recorded soil moisture levels in South Canterbury deviate most from previous years in parts of the high country where recent rainfall has been significantly lower than average.