POWER IN PROSPECT

Evening Post, Volume CXIX, Issue 33, 8 February 1935, Page 38 (Supplement)

POWER IN PROSPECT

ON the preceding page is an account of the development of the New Zealand hydro- • !. ,f sy^em. The following, also written by Mr. F. W. Furkert, gives a general outline of the^ system, and a useful summary of the possible further development of the waterpowers already harnessed and of other sources ot power.

A general, outline of the system is as follows. .In the 'North Island there are three main, generating stations, Mangahao, 19,200 'k.w., ««™ana,32iOOO k.w:, and Arapuni, 60^000 kw. ; The first : named is, a high head scheme: based on the short-circuiting of part of .■■■ ; - ; tne.-c : headwaters of-the .Manawatu River, thus --reducing; its length of seventymiles to about SfTn ■ an ' P re" servin S 900 ft of the total: 1073 ft ot iall for. power generation. Storage in three dams enables some equalisation of the extremely flashy stream flow, but a great deal of water is still wasted in floods owing to the want of a really favourable spot at which to construct a storage reservoir. Should power be'c°me more valuable in the future, more water could be led in from other streams and more dams built, but at present prices the station wm- develo Ped UP to the economical limit. Waikaremoana utilises part of the fall of tlie waters^scaping through the rock barrier, which formed Lake Waikaremoana, on their way to • tne old river valley bottom. It can be increased m-two ways, firstly, by other stations above and below developing the balance of the avail- ... able .fall (not quite so favourable as the first development), and, secondly, by regulating "the outflow from the lake. The lake is so large relatively to the watershed that it could completely regulate the flow, but at present the r outflow is mostly through subterranean outlets, .and these pass insufficient water in times of low lake, and conversely when the lake is high ,tbo. much water escapes (partly over the top)' to be dealt with by the installed machines, the problem of regulating this lake possesses characteristics not paralleled anywhere, but it will ■be solved and enable the output to be increased to 130,000' k.w. ... .Arapuni obtains' its power by means of a dam which holds up the Waikato River and makes an artificial head of 175 ft. It also does ,a certain amount of regulation of the rivei .flow, which is already well regulated by Lake .Taupo and the pumice blanket which covers a great deal of the watershed. Without furthei headworks the power-house capacity can be in creased to 120,000 k.w. Though we generally srjeak of the undertaking as a three-station system, there is also in constant use the Horahora station, eight miles further down the Waikato River, previously mentioned as the pioneer'of the Government network. Its 10,300 k.w. cannot be increased. . THE TRANSMISSION NETWORK. j The main transmission lines, operated prin papally at 110,000 volts, extend from Welling ton very'roughly paralleling the New Plymouth railway, to Stratford, thence via the railway to Ohura, and thence north to Arapuni, where the power from : that station and Horahora are connected. Then the Waikato Valley is followed to Mercer, and thence almost straight to Auckland (where the city steam plant and the Government Diesel plant can be linked up) and'round the harbour to Takapuna. Fromiiorahora to Bombay, via Te Aroha and Waihi toere is aru% maih with an extension into-the Bay of Plenty district, which can link up with | the Omanawa Falls and McLaren's Falls plants I oi the Taiirajpga Borough Council. From Ara- ! pinji Another line runs-via Rotorua to Whaka- ■

tane, and eventually a branch from this will connect with Waikaremoana, completing the main ring. The fuel plants, of Wellington, Palmerston North, and Wanganui are arranged for switching in, and can when required supply into the Government system; the same applies to the water-power plants at Tariki and Waiwhakaiho of the Tariki Power Board and New Plymouth Borough respectively. From Bunnythorpe a line runs across the ranges to Woodville, branching south for the Wairarapa and north to Gisborne, via Waikaremoana, where it.picks up current from that station. In time the north line will be extended to connect with Dargaville and the water-power station of Wilson's Portland Cement Company at Wairua Falls, and eventually perhaps to Kaitaia. It will be seen that the installation is fairly complete, but further connection in the interests of continuity of supply will no doubt be made. The Wairarapa line will come over the Rimutaka Hill to connect at Melling with the high-tension spur line from Khandallah now serving the Hutt Valley Power Board. All lines in the main ring, some of which are still only single, will be duplicated and triplicated. Ihe very limited extent of the coal resources of New Zealand should prompt successive Governments to encourage any changes which will reduce the use of coal for any purposes which can be otherwise served. ADDITIONAL POWER IN NORTH ISLAND. It will be seen from the above that the north and east of the Island have provision made tor much additional power by extensions of Arapuni and Waikaremoana, but the south and west are not so well situated.' Mangahao can be somewhat increased (at a price), and econo-

mic power stations are possible on the Otaki and Hutt Rivers, but the mind's eye turns to something bigger, and the main Manawatu, the Rangitikei, and the Wanganui come into the picture. Investigations so far made do not admit of a definite decision, but the following general remarks may be made:—

The whole valley of the Manawatu is settled, and farms extend to the water's edge in all parts except the mountain valleys, where the potentialities are too small. There are no really good dam and reservoir sites except perhaps in the ■ Woodville-Ashhurst Gorge, where an adequate raising of the waters would swamp Woodville and much rich farm land, and necessitate extensive and expensive deviations of both railways and highways. The Rangitikei flows generally in gorges where, the erection of dams would, not be unduly expensive, and the raising of the waters would not interfere with railways and main highways. But this river carries considerable gravel and other detritus, its flow is very variable, and its regular inclination and narrow valley militate against large storage being obtained with moderate dam height. The Wanganui runs for many miles through unsettled country, its gorges provide good dam sites, and its flat slope, particularly in the lower reaches, where the most water is available, make storage reasonably cheap. A dam one hundred feet high just above tidal influence would back up the water far past Pipiriki. When we consider that 40 square miles at Mangahao, incompletely regulate.d, with 900 ft fall, produces 24,000 horse-power, the Wanganui, with 2850 square miles, even with only 100 ft of fall, should. be worth more than, a second thought, especially as it can be almost

entirely regulated and supplemented with the waters of the Mangawhero. There are other tongs to be considered, such as rainfall, but with dams at tide level and above Pipiriki, a quarter of a million horse-power should be realisable economically. MANY POSSIBLE SOURCES. Assuming a demand of one-half a horse-power per inhabitant, which is two and a half times as great as that on which the Government scheme was based (but which has not yet been reached) the one million population, just S^' 1 COuld have its P°wer demand of . bOO.OOO h.p. easily met from Arapuni, Waikaremoana, Mangahao, and Wanganui; or alternatively, op the originally-assumed basis, two and a half million people could be supplied. Looking further ahead, the Waikato can be damned at a gorge some miles below Horahora and made to supply a further 50,000 h.p. before it escapes to sea. Dammed just above Arapuni (*i lt WOuld a further 200,000 h.p. land there are several other dam sites), or the waters of Lake Taupo can be led by a tunnel mrect from one of the western bays into the Waikato a little above Arapuni Lake, thus making _ use of the entire potential energy of the basin above and surrounding the lake. The mere recital of all the other feasible power schemes would render this article too voluminous, but sufficient has been said to show that many generations will elapse before if becomes necessary for the engineers of the future .to worry over the problem of bringing power from the South Island. When that day comes the population may be more easily transferred than the power, if they have not already drifted south to the great works, to which the South

Island's incomparable power will give birth.

The supply of power to the South Island at present is not so systematised and inter-con-nected as in the North Island, but practically every settled district there is also tvithin reasonab c reach of power wires. The main station is Lake Coleridge, which at present supplies from Hurunui m the north to Hampden in the south, assisted when necessary by the Diesel plant at Lyttelton. The Waitaki power station is already connected, and will shortly be feeding power into the same system. It will relieve Coleridge of the load to the southward, thus leaving surplus power to cope with growth of load in and around Christchurch. Lines now being erected will soon join- up with the Waipori network and enable Waitaki to relieve Waipon station, now somewhat overloaded. Waipori now supplies from the Shag Valley in the north to Catlin's in the south and inland via Lawrence as far as Beaumont. Almost the whole province of Southland is supplied by the Southland Power Board's hydro-electric station at Lake Monowai. This station is overloaded, and negotiations are now in progress which will undoubtedly lead to the extension of the Government high-tension lines to Gore, at which point power from Waitaki will feed into the Southland mam transmission lines. (It is only a matter of fixing mutually satisfactory financial terms.) Central Otago is now supplied frbm the Teviot Power Board's hydro station on the leviot River, and a very few miles of line Will connect this reticulation to the Government's, when power demand justifies the cost., Marlborough draws -its power requirements from the hydro station of the Marlborougb

Power Board at Benhopai. So far the sparcity of population has prevented a connection from its system at Ward with the Coleridge lines at Hurunui. Nelson City has-the only steam generating station still running continuously in New Zealand. The Waimea and Motueka Valleys- receive power from a small hydro plant at Brightwater, and another small plant on the Brooklyn btream, near Motueka, is now being developed to supplement.it. Later the Waimea Toy^r Board proposes to develop enough power pn^tSe Lobb R lver t0 supply Nelson City) g S wel] M all. lto own territory, and also to connect^ satisfactory terms can be arranged, • with the lakaka and Marlborough installations, 'and even possibly with Murchison. <- Westport has a small hydro planf for town power. The Grey Power Board, with a hydro station on the Arnold River, supplies" all the payable territory in the Grey Valley and the settled coastal area. A hydro station at Lake Kamen and another small one at Kumara supply Hokitika and the mines; and the sawmills and farming areas centring in these towns, tor the future the development of business and industry in the north end of the Island will in time justify the harnessing of Lake Rotoroa in the Gowan Valley, which could supply all the demands of the Nelson and Marlborodft , provincial districts for many years to come. DIFFICULT TO FORECAST. When Canterbury's load reaches the capacity? of the present stations. Waitaki can be increased t tW°,n«n,f, half times its Present size, that^ from 40,000 k.w to 100.000 k.w., by regulating; Lakes Tekapo, Pukaki, and Ohau. The erection of another dam above the present reservoir would enable that output to be doubled again, fhe Clutha could be dammed in many places/ but probably .the choice would fall on a sit* as far down stream as feasible, say, near Black--cleugh,_ below Beaumont, thus reducing th¥ ransmission distance to a minimum, and ob* taming the supply of water. .But the possibilities of power development in the, South Island are so numerous and favourable that it is idle to speculate on which scource* will be used. ': ■ When a large station is developed in the north and is inter-connected with the present extensive eastern system and a link is thrown acros? trom Coleridge to the Arnold, the West Coasf stations being meanwhile connected, it can be said that the South Island system will be W most as complete as that of the North Island? At one time the writer was very optimistic about the prospects of new industries spring »ng up in the Western Sounds on account of the enormous and very cheap power possibilifie* there but the climate, isolation, and distance trom labour supply are definite drawbacks; while the great possibilities: in the Clarence, Waimakariri, Clutha, Waitaki, and other river! near to centres of population with good climate and with all the amenities of civilisation anU good harbours adjacent, can supply a great demand for cheap and abundant power wtien it arises. . > .. -^ Nevertheless, with the world's coal and oil resources shrinking continually, and with rib possibility of replenishment, industrial activities must gravitate towards the water-power alternatives, and the South / Island must evenally iL ecome industrialised,-and; its specially cheap West Coast power sites will be the scenes Sreat smelting, chemical, and other works, not for New Zealand alone, but for the world's markets. But the day for this seems still afar on. •