Hurunui hydro cost could be $50M

Press, 4 October 1977, Page 4

Hurunui hydro cost could be $50M

A power scheme on the Hurunui River could cost as much as SSOM. A meeting of the water committee of the North Canterbury Catchment Board received a report outlining proposals for the development of the Hurunui' River. Lake Sumner, in the upper reaches of the river, holds rhe key to any hydro-electric development on the Hurunui. The 1389 ha lake, which the Hurunui flows in and out of, not only prevents shingle being carried further down the river but substantially moderates flood flows, as well as providing a large water storage area. The need for a large spillway structure on any' downstream dam to cope; with flood flow’s, is there-j fore reduced, which would ! substantially lower the cost! of any power scheme Two alternative areas fori power station sites are presented in the report. The first area is on the I north branch of the Hurunui.* downstream from Lake Sumner, in the gorges before the confluence of the north and south branches of the, rive. Preliminary investigations have been carried out in this area by the North Canterbury Electric Power Board n three sites, one of which as not proved feasible beause of engineering difficulties. The other alternative ta .he report is a site downstream at the confluence of he north and south

branches near where the Mandamus River joins the Hurunui. From here the Hurunui would be diverted north across the Amuri Plains to the Waiau River. Along this canal two lowhead power stations could be built. Investigations by the North Canterbury Electric Power Board have concentrated on the first area, on the north branch of the Hurunui. Here, the power board has chosen two sites as feasible. The most expensive dam would cost between $41.7M and 548.9 M, producing 189GwH per year at a cost of between 2.71 c and 2.31 c per kWh. The other project i? estimated to cost between $27.1 M and 530.7 M. producing 109 GwH annually, at a cost of between 264 c and 2.99 c per kWh. The power board lists the following unique features of the Hurunui as 'reasons for power development in the upper river :— The flow pattern of the (Hurunui follows the seasonal electricty demand in the board’s area; Lake Sumner provides . storage — the total storage •of Lake Sumner and nearby I Loch Katrine is enough to store the mean annual flow of the river at the outlet of Lake Sumner for 1.8 years; Any power station built on the river would be a short distance from the South Island’s major power demand area — Christchurch. Problems associated with

the building of a dam on the i north branch of the Hurunui! include:— The effect of creating a barrier preventing salmon and trout reaching their spawning grounds among the tributaries and eight lakes further up the river; The effect of artificially controlling the level of Lake Sumner and the levels it should be operated within, including the flooding of adjacent native bush included tn a forest park; Conflicts between the power board wishing to store water at peak demand times and other users, such as farmers, for irrigation, and recreational users, like fishermen. Irrigation possibilities were outlined in a Ministry of Works and Development report completed in February this year. It suggests six separate schemes, all drawing water from the Hurunui or its tributaries, with a total irrigation area of 25,000 ha. The areas these porposals would affect are low rainfall areas and regularly suffer summer drought conditions. The possible schemes are: Balmoral (3000 ha PeaksMedbury (6000 ha), Masorrs Flat-Hawarden-Waikari (7000 ha). Scargill (2000 ha). Waipara (3000 ha), and Glasnevin (4000 ha). However the catchment board say there is not enough water available, without further storage, to implement these schemes. Storage areas could either be combined with a hydro scheme or included on farms.