POWER SCHEME

New Zealand Herald, Volume LXXI, Issue 21932, 16 October 1934, Page 10

POWER SCHEME

THE WORKS AT WAITAKI HUGE SUPPLY OF WATER NATURE PROVIDES STORAGE TRIBUTARY LAKES AND RIVERS [by telegraph—own correspondent] OAMARU, Monday The Waitaki hydro-electric scheme differs from many undertakings of the kind in others parts of the Dominion in the fact that it is not a storage project in any shape or form. A dam had to be thrown across the river, but its purpose i,s merely to raise the level of the river to furnish an adequate supply of water to provide the motive force for the giant turbines which carry out the actual generation of power. Nature accomplishes all the storage necessary miles back in the mountains i and lakes and rivers of the Southern Alps. The reservoirs of the Waitaki scheme are huge l_akes, fed by rushing turbulent alpine rivers and glaciers, which empty themselves into the tributary rivers of the Waitaki. The primary source of the Waitaki River is the snow-covered pile of the Alps, and its reservoirs are the three lakes. Tekapo, Pukaki and Ohau, the very character and origin of which en- ' sure that there will always be more than enough water in the Waitaki River for the successful operation of the development works. Lake Tekapo is about ' 25 square miles in area, Pukaki 40 6quare miles and Ohau 25 square miles. All are fed by glaciers which at no very remote period extended right down to the shores of the lakes themselves. No Childhood or Youth / The Tasman, the- Cass, the Godlev and other rivers which take their names from the glaciers from which they spring, rise' full-grown and dash downwards to the lakes. They have no childhood or youth, these glacial waterways, 110 struggle for existence. They are bom with I;he full vigour of the mature river and cn leaving the glacier they rush madly in a bee-line for their destinations', The Tasman River runs over a course of 22 miles on its way from the Tasman Glacier to Lake Pukaki, and never once does it turn or deflect in anv way. Similarly, in the 20-mile length of the Godley River, there is scarcely a bend to impede its gay and swift rush to the lake. The three lakes are drained by rivers bearing the iiames of the lakes from which they emerge, and all are deep, swiftly-flowing waterways which finally meet at a common point several miles above the Waitaki dam to form the Waitaki River. This, then, is the source of the waters of the Waitata, but in addition the river has a drainage area above the site of the development works .of approximately 3000 square miles. At the outset, when Waitaki was being compared with other Canterbury projects, with a view to ascertaining the most reliable, the fullest investigation was made into the resources of the various schemes. Recordings were made nt the junction of the Ohau, Tekapo and Pukaki Rivers, and it was found that the lowest recorded flow of the Waitaki at this point was 3000 cusecs, or. 18,750 gallons a second. The average minimum flow of the river, however, was found to be 5000 cusecs, or 31,250 gallons a second. Records of Wate:r Flow While the work was in progress on tho jWaitaki observations were still continued to determine what could be expected in the way of flood flows in the river, and on February 3, 1931, it was found that the recorded flow at_ the < confluence of the three rivers was 85,000 cusecs or 531,250 gallons a second. To date that is the highest flow of the river that' has been recorded, but not even that volume of water could seriously perturb the engineers, since th« dam has been designed to cope with e flood flow of 160,000 cusecs, nearly double the highest flow so far recorded. There can be no possibility, therefore, of the Waitaki scheme ever being unable to perform the functions for ■which it was constructed. The river springs from Nature's illimitable resources. Frost and sunshine, torrent and glacier, avalanche and ice-fall are all incessantly at work converting the raw material extracted from the clouds into floods which swell the river and provide more than enough water for the proper utilisation of the power machinery. i An Altered Countryside It is interesting at the present time to note the alteration that has been effected in the appearance of the countryside at Waitaki by the filling up of the lake at the dam. Where once the Waitaki River wound its way between undulating banks, covering hundreds of acres with water or shingle, there is now a huge lake, extending upstream for a distance of five miles, and a mile and a-half across at its widest point. It covers an area of 1800 acres in normal times, and at flood time will ex* tend itself over another 400 acres. It has a maximum depth of 100 ft. ProV posals are already on foot to have tho Waitaki Lake formed into a tourist resort, and one of the first steps to bo taken in this direction is the afforestation of its extensive shores. The Waitaki County Council has intimated that it will put the work in hand as soon as possible, and the N»rth Otago Soldiers' Aid Association, with which the proposals originated, is also taking a hand. The Waitaki Acclimatisation Society has been steadily stocking the^tributary streams with trout fry for some years, so that the lake should eventually become an angler's resort aa well. There has been some criticism of tho .Waitaki scheme the grounds that a river like the Waitaki will very quickly silt up the bed of the lake and reduce the head of water available for the generation of electricity. That there is no need for concern on this score has been strikingly demonstrated by recent investigations. In the first place, the lakes at the head of the river form natural depositories for the gravel and shingle brought down from the mountains, but in any case it has been shown that it will take centuries for a fan of gravel to spread over the floor of the lake to a depth sufficient to threaten the water supplies behind the dam. By that time, it is stated, the sinking fund will have wip»ed out tho capital cost of the whole scheme. In j any case, it is suggested that before such an eventuality could occur, hydroelectricity will be a thing of the past and mankind will be drawing all its power and light from the air.