LOOKING AHEAD.

Manawatu Standard, Volume LV, Issue 198, 20 July 1935, Page 7

LOOKING AHEAD.

POWER FROM WAIKAREMOANA. PROBLEM FOR ENGINEERS. (By Telegraph.—Special to Standard.) WELLINGTON, July 20. The hydro-electric engineering branch of the Public Works Department is taking practical steps to control leakages of water from Lake AVaikaremoana with the ultimate object of making available nearly four times the power at present being developed from that immense natural storage reservoir. Tlie lake is 2000 ft. aJ>ove 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 tho lake level to a considerable height. However, the immense rocks piled up in such a fashion that they left largo gaps through which wator 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 bo added to the height at which water can bo controlled for purposes of power generation. The geological upheaval which created the problem occurred so long ago that tho strata is thoroughly stable. The work in hand is that of putting down trial bores through this immense ancient slip covered by tho lake waters, and tho sinking of an exploratory shaft in the lake bed on what will eventually become the site of a control tunnel through which tho water for power generation will he regulated. With the knowledge gained through the sinking of bores and running the shaft through the rocks, the department will l>e able to stop existing leaks through the conglomerate mass of rock. Divers have been utilised to locate the inlet-points of these leaks, and chemical methods have also given important information through the tracing of the chemical from tho lake water to the point at which it emerged on the hillside above the power liohse. Experiments are being made with various cement grouting mixtures for sealing the cracks through which water is escaping. FUTURE POSSIBILITIES. If the plans succeed, AVaikaremoana will be capable of steadily supplying water for generating up to IzO,UUII kilowattes, though the present station which serves so large an area extending from Gisborne to Wellington, and frequently up the AVest Coast, has a capacity of 32,000 kilowattes. The leaks in the hillside prevent tho tapping of the lake water at lake level, and the streams from the leaks do not come together until they reach a point 400 feet lower. Then the stream is impounded and power house requirements piped To the turbines in the valley below, Success with the plans now being carried out will enable another powerhouse to be placed above the present one, as an additional head of 400 feet will be available if the whole lake outlet can be regulated through tho tunnel at the bottom of the shaft now being sunk. After being used in the proposed upper powerhouse the water will still be available for the present plant, and when further extensions are needed the outlet ot the latter will be impounded in a shallow lake on what is now a grassy flat, and taken by tunnel and pipe-lino to the third station site giving a fall of 300 feet, and bringing the total power output to 120,000 kilowatts.