The Magic of Water

New Zealand Herald, Volume LXIX, Issue 21278, 3 September 1932, Page 4 (Supplement)

The Magic of Water

No. IV.

1 would like this week to give you a brief description of the Mangahao and Lake Coleridge Tower schemes.

Mangahao station, situated 65 miles north of Wellington City, derives its power from the Mangahao River, which is diverted through two ridges of the Tararua Ranges, into the Mangaore Valley, about 2o miles :rom the. river's natural junction with the Manawatu This valley was chosen as the site for the power-house, because its low level enables the required head of water to be gained. The Mangahao River flows in a deep valley separated from Mangaore by two high, heavily-forested ridges. Two dams have been built across the river to provide water storage. From the lower dam a tunnel, just over a mile long, conveys the water to the next valley, where a third dam, the Arapeti, provides a further reservoir of water. From here, another tunnel driven through the second ridge, leads the water to a point overlooking the power station, 890 ft. below, down to which the water is finally led through big steel pipe-lines. Mangahao is a high-head station, using Pelton waterwheels. There are five of these: three of 3000. and two of 4000 horse power each.

Lastly, we come to Lake Coleridge, the first hydro-electric plant -constructed by the Government and completed in 1915. This scheme is really a model of simplicity in its essential?. In the foothills of the Southern Alps, at an elevation of 1670 ft. above sea-level, lies Lake Coleridge, a long, narrow body of water separated from the Rakaia River valley by a low ridge less two miles wide. The river level is about 500 ft. below that of the lake. A tunnel through the ridge conveys the watn'r to the hillside overlooking the river. From this point the pipe-fines descend steeply to the power-house on the margin ol the Rakaia River, into which the water from the turbines flows after having done its work. This station has nine turbines: four of 2000, two of 4000, and three of 12.700 horse-power each. The three largest machines were added wiiien the plant was extended in 1926. This brief reference to the four main Government stations is just by way of giving you an idea of the extent to which the natural features of the country were favourable to water power development, and the methods by which the engineers took advantage of them in each case. The working of the great generators that produce the electric power, the control of

By A.MJ.M.E

the current and its transmission through*" ." I out the Dominion is a separate and a big one. too. But I hop* I' - ~ have, succeeded in showing yon that th» secret of the power in water is really not |§' ; 'f very hard to grasp, and that even £htoej£-| simple little contrivances of my boyfcoo4'i4%| days can give useful guidance to an under-' "■ * standing of the principles of water-povir. engineering. _ . I have now explained how the up fore'e of water is made to drive ' : water-wheels or turbine?, and so produce j power. I would' now like to tell you something ; about another side of the subject-, »n<J one which does not deal with hvdraulie' - principles, pipe lines and heads of water. You may be sure that in carrying out V - | a big water-power scheme ah ehormmii ambunt of planning,'-calculation, organisation and human energy is needed. During its construction a thousand men, f or even more, may be employed. Let u» sen how such an undertaking is hunched and get an idea of some of the problt-ms to be dealt with. Of course, there is a k lot of preliminary work to be done before IS;' a start is made in building the powerhouse and other portions of the Whetne.

Surveys and investigati6ns must be car* ried out to decide the most suitable site and many and varied arrangements made for housing and providing for all the ' workmen and for the transport of the huge quantities of machinery, materials and food, etc. " The men who carry out all these prehmmaries are indeed pioneers, for their ' 7 work takes them out into fresh, uninhabited country, where the first sod has to be turned in preparation for human abode and activity. When construction work is in full swing there is the popu-,..' lation of a small township to be provided for, and, of course, such a village does not grow np in the usual haphazard way, with gradual increases of inhabitants, houses, shops, etc., year by v year. Its boundaries, the number and situations of the cottages, huts and storehouses are planned beforehand and provision made for water supply, drainage, lighting and transport. Next week we will pay a visit to "Wai- $1 taki, in the South Island, and see how the pioneering construction work of a great hydro-electric scheme is carried out. (To be continued)