HUGE HYDKO-ELECTRIC SCHEME

Dominion, Volume 9, Issue 2776, 20 May 1916, Page 13

HUGE HYDKO-ELECTRIC SCHEME

TASMANIA'S BIG NEW INSTALLATION

Tasmania's Statehydro-electric 6cheme, which was officially opened by the Gov-ernor-General of the Commonwealth on Saturday, is tho largest , thing of its kind at present on foot south of 'the line (saye tho Melbourne "Argus-).; For the -moment, indeed, it is ' only (developing UOOO horse-power, ns against., the 10.0U0, of the Lake Coleridge' (N.Z.)'"scheme, but/the present plant is only the first instalment of something very much bigger. It will be duplicated .almost at once, and eventually something approaching 100,000 horse .power will, be developed from the waters of the Great Lake. .

The outstanding feature of the Tasmanian scheme is its compactness and simplicity. The Great Lake, the reservoir which supplios tho necessary water, is situated nearly lii' the centre of Tasmania, and at an elevation of 3250 feet,' or. little. short of half , the height of the highest mountain in Australia, aliqVe sea; level..-It had normally an area of "miles, or 26,880 acres, now considerably increased by tho raising of the level of tho lake. •Into this_ lake drains, an., area of 227. square miles, wi'tli a heavy rainfall and snowfall ranging from 60 inches upwards. By way of comparison, it may be noted that the Mount Lyell Lako Margaret hydro-electric scheme, tho first of itskind. in Australia,:which has now been in active operation for n couple of ■yeais, is based on a, lake of 370 acres, with a drainage- area of seven 6quare miles. The-"head" .of water is almost identical with that given by the Great Lake scheme, and the Mount Lyell Com"■pany is able to develop 6000 horse power, 'and to supply all the power needed' fot operating the machinery at ita mines, smelters, and other works; to light them, and also to supply light and ■ power to the town of Qucenstown. It is true that the Lake Margaret region has a much heavier rainfall, averaging about'l2 feet 'i year, but' the comparison may give Borne idea of the potentialities of the Oreat Lako scheme.

The Great Lake is drained by the Hirer Shannon, and ft few miles south, of the lalio the Shannon, is flowing across the ■plateau about 3500 feet sea level, while a few miles to the westward the River Ouso is flowing at the bottom oil a deep, narrow 'gorge "1800 feet above the sea. It is on this difference in levels thaJt the scheme , is -built. A dam across the Shannon at the point where it leaves the lake has raised the level of the latter by 11 feet, and will eventually be carried up to IB feet. The water thus conserved flows down the Shannon for fivb miles, Mid is then diverted into >■ canal, vy'hich carries it for three and a half -miles to • the watershed between the Shannon and the Ouso. Here a convenient lagoon of 300 acres acts as a settling reservoir, and from it first a wooden pipe of 4 feet internal diameter, and then for the last and steepest part of the slope a, doublo

steel pipe carries the water .downtiJ'the. power 6tation built on tho'banks:'of the Ouse. The vertical fall of the pips line is 1132 feet, and after allowing tor lossea , there is a net available bead of water of lflofl feet at the turbines. It is there that the latent power of the water is dtv to loped by the .turbo-alternatprs into three phase 50 cycle: power at. 6600-voltsT- It ia then transmitted- at tlie eriornious"pressure of .88,000 volts over-the/hteh "tension transmission' line, 63.miles.in length, to Hobart." At . Hob'art transformed down again to (IGflO volts, and is ready for use for the thousand and'one purposes to which electricity can, ha put. The amount of power which-the water nf:,the:-Great Lako is capable of developing .;hag been variously estimated. • Mr. Parry, - the, -New; Zealand hydro-electric;' expert;:' on tlio_ scheme, • put it 65,000. ..horseiv. power, which isV probablya; conservative', estimate. There'-is, too, the of increasing the water supply;of Great Lake by diverting into it. the; headiwaters of the Ouse whiich ..fife "plateau at a higher level than-'tho lake/; and only a few miles away; : .This work- presents no engineering' difficulties..'." The Ouse. would: :first be diverted J -;.jhto tha G'reat Lake,, and, then after ■■ passing through the lake and down the Shannon be,put through tlie power station and re< toned- to its old ; with interest. But In view of the fact that the total aggregate of tho inquiries already -mads for hydro-electric power -runs 150,000 horse' power, andlhat the ■ 'contracts already in hand and. the. others, iij which tentative agreements ; lrave already ■been reached amount to over 100,000. tho Government has been looking round for other sources of power in case oi need, and some preliminary investigation has been made of what might be don« irith Lake St: Clair, a lake about halt the, size of the Great Lake, "which lies at an elevation of 2000 feet about 30 mi>« to the west.