MORE HYDRO POWER

Auckland Star, Volume LXVI, Issue 170, 20 July 1935, Page 13

MORE HYDRO POWER

LAKE WAIKAREMOANA.

PROBLEM FOR ENGINEERS

PLANS FOR STOPPING LEAKS

(By Telegrapn.—Own correspondent.)

WELLINGTON, this day

The hydro-electric engineering branch of the Public Works Department is taking practical steps to control leakages of water from Lake Waikaremoana with the ultimate object of making available nearly four times the power at present being developed from that immense natural storage reservoir. The lake is 2000 feet above sea level, and has an area of 21 square miles, with one outlet presenting a highly interesting problem for engineers.

Ages ago two immense cliffs appear to have been tilted into a gorge, blocking up the outlet and raising the lake level to a considerable height. However, the immense rocks piled up in such a fashion that they left large gaps through which water could escape at various levels down to possibly seventy feet below the water surface.

It is intended to stop these subterranean leaks, which all occur in one bay of the lake, and if this can be done 400 feet will be added to the height at which water can be controlled for purposes of power generation. The geological upheaval which created the problem occurred so long ago that the stratum is thoroughly stable. The work in hand fe that of putting down trial bores through this immense ancient slip covered by the lake waters and the sinking of an exploratory shaft in the lake bed on what will eventually become the site of a control tunnel, through which water for power generation will bo regulated. With the knowledge gained through sinking of bores and running the shaft through the rocks, the Department will be able to stop existing leaks through the conglomerate mass of rock.

Divers have been utilised to locate the inlet points of tl'-'se leaks, and chemical methods have also given important information through tho tracing of the chemical from the lake water to the point at which it emerged on the hillside above the power house. Experiments arc being made with various cement grouting mixtures for sealing the cracks through which water is escaping.

Power Possibilities. If the plans succeed, Waikarenioana will be callable of steadily supplying water for generating up to 120,000 kilowatts, though the present station, which serves so large an area extending from Gisborne to Wellington, and frequently up the West Coast, has a capacity of 32,000 kilowatts. The leaks in the hillside prevent the tapping of the lake water at lake level, and the streams from the leaks do not come together until they reach a point 400 ft lower. Then the stream is impounded and power-house requirements piped to the turbines in tlio vallev below.

Success with the plans now being] carried out will enable another power house to be placed above the present one, as an additional head of 400 ft will be available if the whole lake outlet can be regulated through the tunnel at the bottom of the shaft now being sunk. After being used in the proposed upper power house, the water will still be available for the present plant, and when further extensions are needed the outlet of the latter will be impounded in a shallow lake on what is now a grassy flat, and taken by tunnel and pipeline to the third station site, giving a fall of 300 ft, and bringing the total power output to 120,000 kilowatts.