Hurunui project opponents warn of impact

A proposed dam on the Hurunui River could cause an "ecological bomb", opponents warn.

The Hurunui Water Project plans to build the 75-metre high dam on the river's south branch and raise the level of Lake Sumner through a weir to irrigate about 42,000 hectares in the Hurunui and Upper Waipara catchments.

Opponent Edward Snowdon, who lives in Christchurch and owns a hut at Loch Katrine, said the new seven-kilometre lake holding 111 million cubic metres of water for irrigation was being presented as a wonderful new recreational resource.

However, he said, there could be dust storms and exposed areas of dead wasteland in dry years.

"No fish will live there it will become, in summer, a dust bowl," he said.

"You'll get dust storms over the North Canterbury plains.

"This is an ecological bomb."

Snowdon, a member of opposition group Dambusters, said the project would ruin one of the best sources of wild water in Canterbury.

"This is the Manapouri of our generation."

Fish & Game environment officer Tony Hawker feared the salmon run in the Hurunui could end because of the dam.

"Obviously, a massive structure like this will stop completely any chance of fish passage."

An environmental report for the project, from Sinclair Knight Merz, said public access to the reservoir on the Hurunui River's south branch, and the river above the reservoir, would add to the area's recreation potential.

However, the proposal's ecological report, from Boffa Miskell, said in very dry years estimated at once a decade more storage would be needed for irrigation and that might "empty the lake".

A 50-million cubic metre lake would be left, exposing two kilometres of river gravel and inundated terraces.

The report said an "extreme draw down" could destroy plants and animals, and result in longer lasting water-quality issues.

"Overall, the level of impact of the operating regime on the new lake habitats and species is uncertain."

Shore processes and management consulting scientist Martin Single said some lakes with large ranges, like Pukaki and Tekapo, had dust storms, while Mahinerangi, near Dunedin, did not have such problems.

The likelihood of storms would depend on whether the area had dust-generating sediments, and the wind, he said.

Hurunui Water's project manager Amanda Loeffen disputed there would be dust storms but admitted river gravel would be exposed.

"We don't know what will happen to the land, but it won't be uncovered every year," she said.

"This is a huge project you can't make huge changes like this without having some effects."

Hurunui Water had tried to find a solution that would have the least impact, she said.

Building the dam would improve the health of the river downstream by increasing the flow, she said.

- © Fairfax NZ News