D.—la.

The cost of the scheme outlined above, for 11,000 b.h.p. may be taken at £400,000, and the probable gross revenue at £40,000 per annum. The cost of a scheme to give 5,000 b.h.p. continuously would be cheaper —say, £225,000, giving a gross revenue of £36,000. A power-installation very similar to this was under construction lately at Utah, U.S.A. The leading features may be summarised here for comparison. The principal difference between the two schemes is that the Utah one has a much larger drainage-area, but a much less rainfall, and likely a much less percentage of rainfall running off. Dam, 100 ft. high ; foundation to crest, 400 ft. long; depth of water in reservoir, 60 ft.; storage-capacity, 2,400,000,000 cubic feet. Conduit nearly six miles long, 27,000 ft. being wooden-stave pipe in trench, and 4,600 ft. steel pipe ; both pipes 6 ft. internal diameter. Quantity of water delivered, 250 cubic feet per second. Effective fall, 440 ft. Gross power given as 12,500 (equal to about 10,000 b.h.p.). Length of transmission-line, thirty-eight miles. On the conduit there were eight tunnels (the longest 667 ft.), eight steel bridges of a total length of 560 ft., and one timber trestle. A dam to contain as much water as in the above scheme is not possible on the Tauherenikau, nor is it absolutely necessary. It remains to test the value of the river by gauging to determine the flow throughout the year, and to ascertain by survey the storage available at reasonable cost. Hutt. The Hutt Gorge a short distance below the junction of the Pakuratahi Stream is very narrow, and can be dammed with comparative ease, the breadth of the river being under 50 ft. ; the slopes of the gorge steep and showing rock-outcrops, so that probably good foundations can be got without much excavation. A dam 125 ft. high above low-water level would store a very large quantity of water —how much could only be determined by a contour-survey, as the water-level lines would be very irregular. The water would reach over two miles above the dam and above the road-bridge over the Pakuratahi. The drainage-area above the dam would be fifty-seven square miles. Of these thirty square miles would belong to the Hutt River, and the remainder to the Pakuratahi. The Hutt portion of the basin is bush-clad. A large portion of the bush on the Pakuratahi is now cleared. Apparently there must be a considerable rainfall over the area in question. For the years a raingauge was kept at the Upper Hutt the average rainfall was 65-7 in. The rainfall at the Summit has averaged for nine years in. The rainfall on the higher portions of the basin which reach heights of 2,800 ft. to 4,400 ft. is no doubt much greater than at the Summit, where the height is 1,144 ft. only. The junction of the Pakuratahi is 583 ft. above sea-level, as determined by levelling. The best place for a power-station is probably just above the junction of the Mungaroa with the Hutt. The conduit would consist of about 146 chains of drive, and about two miles of fluming or ditch, with a length of steel pipes from the end of the flume to the power-station. An effective head of about 275 ft. would be obtainable. I think investigation will show that water enough can be got to give a power plant of at least 5,000 b.h.p. at Mungaroa for continuous working, a dam 125 ft. high being built. The cost of this scheme would be, say, £225,000. The gross revenue derivable therefrom would be, say, £40,000 a year, the. line losses being small for the short distance. To meet the present-day conditions of hours of working, a plant of greater capacity would be required to use all the water in a shorter time, working at varying power during, say, sixteen hours or more per day. Supposing a plant of 12,000 b.h.p. installed for this purpose, the cost would be, say, £340,000, the gross revenue being £50,000. The dam for this scheme would be 150 ft. high. The dam, if built, should be 150 ft. to 160 ft. high. This would give a great increase in the amount of water stored, and a consequent increase in available power; but this is a point to settle when the total annual flow of the river is known. The distance of the power-station from Wellington would be a little over twenty-four miles. The Hutt and Petone districts would take a large amount of power, so that the transmission losses would not be so great in this scheme as in others. The transmission-line should be comparatively very safe from risks of breakdown. Though relatively expensive per horse-power, this scheme is, I think, worthy of very full investigation if ever any proposal is considered for supplying electric energy to Wellington. The low-water flow of the Hutt is likely to be much too small to justify any attempt to utilise it alone for the generation of power. Storage of all the water flowing from the upper areas of the river-basin is necessary to make any such scheme a success. The Akatarawa River joins the Hutt just above the Upper Hutt Station. Its drainage-area is fifty square miles above the junction of the little Akatarawa. The fall from this point to the Hutt is 133 ft. A race starting about a mile above the junction of the two Akatarawas, and taking the water of both to the Hutt would give, say, 1,000 b.h.p. continuous working for probable ordinary low-water flow. Small dams for overnight storage could be got, but the valley does not present conditions favourable for the construction of a large storage-reservoir to equalise the annual flow. The Whakataki joins the Hutt River just below the Upper Hutt. It has a drainage-area of twentythree square miles to the junction of the two streams at Birch Spur. The stream here is nearly 160 ft. above its junction with the Hutt; the distance is about two miles. A reservoir of some size could be got here. If most of the water could be stored, 700 or 800 b.h.p. could be got from this stream for continuous working, and about twice this for intermittent working. The cost of a dam would be too great to justify much storage, and the scheme is only of value for some small local industry.

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