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The controversial Mokihinui River scheme may be the one that’s grabbing national attention, but the West Coast of the South Island has no fewer than five hydro-electric power schemes in various stages of development – and the first of them could be on-stream within six months. For much of the past decade The Coast has been leading the country in economic development, thanks to its dairy, mining and tourism industries, but it’s always been held back to some extent by having to import virtually all of its power from elsewhere. That’s despite Reefton becoming in 1888 the first town in the Southern Hemisphere to be lit by electricity, sourced from a hydro-electric scheme. It’s also despite the region’s notoriously high rainfall and the multiplicity of wild rivers pouring untapped off the Southern Alps into the Tasman Sea. At present the West Coast is supplied from the Waitaki hydro system in Otago, with power being sent from the Benmore dam through Christchurch to Kikiwa and Inangahua, with resultant transmission losses of up to 50 percent at peak times. The Coast’s electricity demand presently peaks at 65MW, but is expected to increase to 80-88MW by 2012. A number of small hydro-electric systems – apart from Reefton’s – were set up especially in the early years of last century, mostly to power mining operations, but when the big national schemes came on-stream in the second half of the century The Coast seems to have abandoned any ambitions to become self-sufficient in electricity. The $300 million Mokihinui scheme 60 kilometres north of Westport is the first major one to be launched, though it is presently mired in the Environment Court appeals process after being granted resource consent in April this year. Promoter Meridian Energy and the Department of Conservation (DoC) are at loggerheads, DoC reckoning the environmental cost is too high. Separately from the resource consent, Meridian needs DoC permission for access over public land, and it had lodged two such requests with the department, sweetened by the offer of a 790-hectare land-swap. The parties have decided that rather than thrash out the side-issues in the court, they would try to sort them by mutual agreement, thereby saving the taxpayer significant court costs. However they’re still expected to be back in court in November this year. The Mokihinui scheme involves the construction of an 85-metre-high dam on the river 11 kilometres from the coast and three kilometres upstream from the village of Seddonville. The proposed dam would be 300 metres wide and extend 14 kilometres inland, flooding 225 hectares. It would produce 310-360 gigawatt hours a year, peaking at 35MW. While the battle between state-owned Meridian and DoC over the fate of the pristine Mokihinui River has hit the headines nationwide, flying under the radar have been four other hydro-electric projects. The largest of these is on the Stockton plateau where state-owned collier Solid Energy’s huge opencast coalmine has for years been polluting the Ngakawau River, 30 kilometres north of Westport. In January this year a local company, Hydro Developments gained resource consent for a hydro scheme that would create two storage lakes, one of 50 hectares and the other of 28 hectacres, fed by 10 streams on the plateau and connected by a 3.85 kilometre-long tunnel. A power station would be built at the tunnel outlet, with a 4.9km-long tunnel leading to a second station just above the township of Granity. A 600 metre-long submarine outlet tunnel would take the outfall into the sea beyond the wave-break. This 25MW proposal, capable of powering 22,000 homes, won the blessing of conservationists because it will incidentally clean up the Ngakawau River, but hardly had the ink dried on the resource consent before Solid Energy lodged an appeal against it. Belatedly deciding that a road across part of its tenement threatened its future mining options, Solid Energy came up with its own hydro scheme, different in detail but producing about the same amount of power. Solid Energy’s scheme has set up a nice little David-and-Goliath battle between it and hydro Developments which will ultimately be played out in the Environment Court in the likely event that current negotiations between the parties fail to reach agreement on who should build what and where. Just a few kilometres north of Westport there’s another hydro project already under way that could be producing 4.2MW within six months. It’s the $10 million Lake Rochfort project which will take water from the lake through a 2.5 kiloemtres-long penstock with a 415 metre head. It’s the brainchild of another local company, Kawatiri Energy, which is presently driving an access road to the site where it has already nearly completed a power-station. Down to the south near Greymouth, Tauranga-based private company Trustpower is planning the 46MW Arnold River hydro scheme in the valley of the same name, using part of an existing dam, powerhouse and spillway complex. The plan is to divert water from the river through a canal starting at the existing dam to a storage pond and power station, then returning the water to the river. Once the new scheme is up and running, the old one will be decommissioned, leaving the old tail-race and pipe bridge which may be converted to a visitor attraction. This scheme won resource consent back in November of 2008 but is the subject of appeals – including one by Trustpower itself – which will probably have to be resolved in the Environment Court. Further south again, near Harihari, a subsidiary of local power utility Westpower is a couple of years away from the completion of the Amethyst hydro project. This too is an upgrade of a small existing scheme on the Wanganui River – not be confused with the larger river of the same name near Karamea, nor yet the even larger one on the west coast of the North Island. The Amethyst hydro scheme, being built by Harihari Hydro, will be a redevelopment of a long-since-decommissioned scheme and on completion will generate 6MW.
Energy NZ Vol.4 No.4 July-August 2010 |
West Coasters are suddenly rushing to generate electricity from their famously high rainfall, as Hugh de Lacy discovers.