Irrigators and water users nervous as new restrictions roll into place

Lake Opuha is 100 per cent per cent full, after a period when inflows were higher than outflows.

Lake Opuha is 100 per cent per cent full, after a period when inflows were higher than outflows.

Water users in the north and south Opuha rivers, the Te Ngawai River and Opihi River [above Rockwood] are on tenterhooks as they wait for Environment Canterbury [Ecan] to review minimum flows and a potential water allocation restriction.

The review is based on national environmental standards that have come out in the last five years, Opuha Water Ltd chief executive Tony McCormick said.

The Pareora River and Orari River have been through this process.

Lake Opuha is full to the brim and OWL have been releasing artificial freshies.
Tony McCormick

Lake Opuha is full to the brim and OWL have been releasing artificial freshies.

"We have undertaken to assist and coordinate through that process with the intention of trying to protect our irrigators interests," McCormick said.

"The Te Ngawai group have already mobilised and are doing some work to pull together the information needed to make sure they can contribute to the zone committees minimum flows discussion."

Also under scrutiny, and making some water users nervous is a review of the stream depletion process, which determines whether a well has an effect on a nearby stream.

Irrigators in some parts of the Fairlie Basin could be facing restrictions.
JOHN BISSET/FAIRFAX NZ

Irrigators in some parts of the Fairlie Basin could be facing restrictions.

"The 30-day pumping test has been used locally but the consistent standard is the 150-day pumping test," McCormick said.

"If a well is half a kilometre from a river, and a farmer draws on the well, is it hydrologically connected to the river? If you pump for 150 days, will that have an effect? What this means is that water users whose wells are not deemed to be hydrologically connected to the river most probably will be under the 150-day regime. At present, if they are not deemed connected they don't have to go on restriction when the river gets low but this will change.

"OWL shareholders aren't restricted because we augment the river. That's what their shareholding pays for, that reliability. Now there will be a new lot of people connected to the river. Some water users may not be able to enjoy the unrestricted water they are used to."

McCormick said the main thrust for the company was an "adaptive flow regime." He said the company had learned the last few years that this was the best way to manage the river and storage.

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"When things get tough we need to be able to adapt our operation to the conditions. It's hard to be prescriptive about this."

"This is what we have learned over the last couple of years when we were short on water. The importance of reliability and how we can, in collaboration with stakeholders, manage the river and storage to have better outcomes than what a rigid regime would have.

"For example, the plan at the moment is that if the lake gets to a certain level you will be on restrictions. We all know that that level is far too low at 10 per cent. 

"The lake at 50 per cent in February- not such a big deal. But the lake at 50 per cent in September is a real worry, but not if there is a whole lot of snow in the catchment. If it's a dry catchment, it is a worry.

"Snow pack is incredibly important going into the season.

"But it's not easy to put this approach into a regional plan which usually has a whole lot of prescriptive numbers and rules."

McCormick said it was too early to tell if things were well set up for the beginning of the irrigation season later in the year.

There was still months of supplying the river to go yet, he said, but levels were well above where they had been in April the last few years.

There was actually more water than McCormick was comfortable with.

"Another big dump of rain like the last couple and we would end up spilling," he said.

"We are looking manage the river down a bit to give us a little bit of headroom. We are being cautious."

 - Stuff

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