Water loss would 'hurt river wildlife'

The historic "Save Manapouri" campaign of the 1970s overlooked the harm it would have on the Waiau River, an Environment Southland hearing was told yesterday.

Fiordland Guardian Dave Riddell made the claim at a resource consent hearing for Meridian Energy.

The company has applied to have its maximum discharge limit from the Manapouri power scheme increased, when conditions permit, from 510 cubic metres a second, or cumecs, to 550 cumecs to generate more electricity.

Mr Riddell said while the Save Manapouri campaign helped preserve the natural processes and patterns in Lakes Manapouri and Te Anau, the impact on the Waiau River was either neglected or unforeseen at the time.

"The power scheme resulted in the be-heading of the lower Waiau River and, on average, about 380 cumecs was removed," he said.

Department of Conservation documents show the mean flow of the Waiau River was 560 cumecs before 1969.

Resource consents issued in 1996 introduced a minimum flow to the lower Waiau of 12 to 16 cumecs, depending on the season, Mr Riddell said.

A second tailrace tunnel in 2002 let the maximum Manapouri power station discharge to increase by 20 cumecs for about 20 per cent of the time, an estimated 4-cumec loss to the lower Waiau, he said.

"Under (the Meridian proposal), another 10 cumecs, on average, will be lost to the lower Waiau River. Therefore, in terms of average flow, practically all of the gains achieved in 1996 will be lost," he said.

The Fiordland Guardians believed that reducing the Waiau's flow to near pre-1996 levels would create the risk of algal blooms and didymo, Mr Riddell said.Former Fiordland Guardian chairman Professor Sir Alan Mark said maintaining the lakes at a constant level, rather than allowing for natural fluctuation, could jeopardise at least 23 threatened plant species.

Jan Riddell, speaking for the Waiau Fisheries and Wildlife Habitat Enhancement Trust, said it opposed Meridian's proposal because it did not adequately address the loss of flood flows through the lower Waiau.

A decrease in water levels affected the sustainability of active channel backwaters, riparian aquifers, wetlands, fish habitat and bird habitat, she said.

michael.forbes@stl.co.nz

- © Fairfax NZ News

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