Dry Summer Sparks Irrigation Queries On West Coast

Tuesday, 4 March 2025, 8:48 pm
Article: Lois Williams - Local Democracy Reporter

The West Coast's long, hot summer has seen river levels dropping and fish life under stress, the West Coast Regional Council has heard.

But the one-in-ten-year drought will not trigger more investment in groundwater monitoring.

In its quarterly update, the council’s environment science team reported low rainfall during the past three months has resulted in several waterways running low.

Fish and Game had been concerned about the impact on fish in the Mawheraiti and Little Grey rivers near Reefton, manager Shanti Morgan reported.

The team had been doing more spot monitoring of water temperatures and quality in the Grey Valley and Buller, as far north as Karamea.

A number showed signs of thermal stress and staff were now working with farmers in those areas to tackle the issue.

“Maintaining healthy riparian vegetation to provide shade is a key way to help mitigate high water temperatures," the report said.

"Riparian shade in smaller waterways … would help larger wider rivers like the Mawheraiti.”

Streams in South Westland were not under similar stress, despite the heat and a lack of riparian planting, because many were spring-fed and therefore cooler, the report noted.

Committee chair Brett Cummings Brett raised the question of irrigation consents in the Grey Valley.
“Some of those irrigation consents are for 30 years. When do we get to change that?"

Some farmers had been given large allocations and others had not been able to secure any, he noted.
Staff confirmed the council could review resource consents for irrigation if the situation changed.

But chief executive Darryl Lew urged caution.

“We’ve had probably a one-in-ten year drought in some of our catchments … but the West Coast is not the dry east coast.

“We’re not Canterbury, or Hawke's Bay or the Wairarapa and we do not have the water allocation pressure on our catchments that ... Canterbury has.”

For that reason the council had not significantly invested in low flow or groundwater monitoring, Mr Lew said.

“And as chief executive, I would say that has actually been the right decision.”

The sort of groundwater models used in Canterbury to determine how much water was available for irrigation cost up to $200,000, Mr Lew told councillors.

“We are very blessed, and from a sustainability point of view, the West Coast is one of the best places to have a dairy farm because you don’t have huge reliance on irrigation that other regions of New Zealand have.”

The degree of monitoring, science and regulation the regional council carried out was “pretty much fit for purpose," Mr Lew said.

Councillor Allan Birchfield agreed, “It’s common sense. Everyone is getting all panicky. It’s scaremongering to say we’re gonna be short of water in the Grey Valley.

“There’s a huge lot of water [running] underground. We’re never going to get to that critical stage."
The dry summer and low river levels had been good for the hydrology team, Ms Morgan reported.

It had enabled staff gather a lot of data and replace equipment at its test sites on rivers up and down the region.

The team had worked with NIWA on a fish passage project; and set up a new sampling at a Reefton swimming spot, which had shown low-risk results.

It had installed new radar units measuring river levels in the Waiho and Kokotahi catchments and another in the Callery River to give early warning of a landslide dam.

And it planned to set another radar unit at Okuru, in response to local requests.

The hydrology team had also upgraded or replaced rain gauges including the Karamea one, to meet National Environmental Standards, the report said.

- LDR is local body journalism co-funded by RNZ and NZ On Air.

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