t).—la.

Monowai Lake. This lake lies at a level of 676 ft. above sea-level. The area of the lake is eleven square milesThe drainage-area is not yet very accurately known. It is probably about sixty-seven square miles. The junction of the Monowai River with the Waiau is 390 ft. above sea-level. There is therefore a fall of about 286 ft. from the lake to the river. The length of conduit would be over five miles, and about three-quarters of a mile of this would be pipes. The lake-level could be raised by an earth dam to conserve all flood-water for power purposes. This should give an average flow of say 700 cubic feet per second. Deducting loss of head in race, and allowing for the flood-rise in the Waiau River, about 225 ft. of head would be available. This should give about 14,000 b.h.p. continuously at a powerstation on the Waiau Eiver, or 28,000 b.h.p. for full-power working for twelve hours per day. The approximate cost of a scheme to develop 14,000 b.h.p. would be £430,000 to deliver energy in Invercargill, and to develop 28,000 b.h.p. for variable working during two shifts per day of eight hours each, would be £735,000, with a probable gross revenue of £100,000 per annum. There is a very good route available for transmission-line to Invercargill, and several small townships could be supplied with lighting and power by the way. The distance to Invercargill will be rather less than sixty miles. More power could be got out of Monowai Lake by diverting the water into Hauroko Lake, to augment the Hauroko-Poteriteri scheme, in which an effective fall of at least 410 ft. is to be obtained. In this way about 70 per cent, more power could be got from the Monowai water. The length to drive between the lakes would be about three miles"iby the later maps, but is shown to be more on the older ones. Whether this method of utilising Monowai would be the most advantageous or not would require some investigation to decide. The be in schist rock, and for the purpose required might be effective if unlined. Hauroko-Poteeiteei. Hauroko Lake lies at an elevation of 514 ft. above sea-level, and Poteriteri at an elevation of 96 ft. The difference in level between the lakes is 418 ft., and the distance between them is about two miles and three-quarters. The conduit would be part canal for 20 or 25 chains at the Hauroko end ; 2 miles 10 chains of tunnel and about 10 or 12 chains of pipes, and about 13 chains of draw-off canal at the Poteriteri end, through a flat on which a power-station could be built. The level of Hauroko Lake can be raised by a dam any height found to be best, up to, say, 60 ft. Part of the height, say 20 ft., could be used to gain additional head (in which case the canal at the Hauroko end of the conduit would be of smaller dimensions), and part to give whatever storage-volume was deemed necessary. The river Wairaurahiri, flowing from Hauroko Lake, was gauged, and the flow found to be 1,800 cubic feet per second. The probable low-water flow may for the present be taken at 1,000 cubic feet per second, and the flood-flow 4,800 cubic feet per second. The area draining into the lake is about 210 square miles ; the area of the lake is twenty-seven square miles. To get the utmost power for a complete scheme, all the flood-water should be retained by the dam. In this way I think water enough should be got to give 80,000 b.h.p. at a power-station on the shore of Lake Poteriteri, for continuous working, or, say, 160,000 b.h.p. for twelve hours each day full power. The approximate cost of these two alternatives would be respectively £1,700,000 and £3,000,000, and the probable revenue likely to be derived from such a scheme, if the energy were fully utilised, should amount to £576,000 a year. The distance from the power-station to Invercargill is about seventy miles by the probable transmission-line route. The scheme is one of the best in the colony, and involves great industrial possibilities for Invercargill and the surrounding districts. This is a scheme in which a lower tariff than has been assumed for the purposes of this report could be charged and yet a sufficient margin be left to cover interest on capital, staff, maintenance, sinking fund, and management charges. The question of bringing the water from the lake to the sea has been partially considered. The shortest distance between the lake and the sea is about eight miles. If the conduit followed this route it would be nearly all tunnel. By another route the least length of tunnel (believed to be the shortest possible) would be about four miles and three-quarters, and there would be four or five miles of race. About nineteen miles of transmission-line would be saved, and the same length of road-making. Much transportation-cost would also be saved. Over 10,000 b.h.p. extra would be got from a station on the sea-shore. Without knowing the exact length of tunnel and pipe-line leading from it to the power-station, it is not possible to estimate the increase of cost, but it would probably be from 25 per cent, to 30 per cent, on each scheme given above. The extra power obtainable would justify this additional expenditure. The height of Lake Hauroko above the sea is now given as 97 ft. less than is shown on the latest maps. The correction is a recent one. The height has now been determined by triangulation, and may be taken as reliable. The greater height was the only one available when I first outlined this scheme. Minoe Schemes, South Island. Only very incomplete information is available regarding the numerous smaller rivers and streams in the South Island, except for Westland. The following list of rivers and streams will be largely increased when complete data are obtained, but some will no doubt be found to be of little value : Pelorus River ; Wakamarina ; Upper Wairau ; Branch, Leatham, and Coulter Rivers, tributaries of the Wairau ; Motueka River, Nelson ; Conway River ; Mokihinui River ; Hurunui River; Broken River, Esk River, tributaries of Waimakariri; Nevis River, tributary of Kawarau; Catlin's River ; Mataura, and its tributaries Mokoreta, Waikaka, Nokomai, Robertburn, Otamita, Eyre Stream ; Makarewa, and its tributaries Dunsdale, Lora, Otapiri; Oreti, and its tributaries Irthing, Cromwell, Acton, Windlev, Wydon ; Aparima River, and its tributaries Etat and Hamilton Burn ; tributaries of Waiau River —Orauwia, Wairaki, Taylors', Ligur, Redcliff, Whare, Excelsior streams or creeks, Borland, and Lillburn.

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