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APPENDIX E. HYDRO-ELECTIUC DEVELOPMENT—NORTH ISLAND SCHEME. INTERIM REPORT. Public Works Department, Wellington, N.Z., 19th February, 1917. Mhmohandum for Hon. Minister of Public Wobks, Public Works Department. I hereby submit, as requested by you, an interim report regarding the present position of the investigation into the scheme of developing the water-power resources of the North Island. Before relating the actual position of the work of investigation I wish to put on record some underlying principles which govern my actions in preparing the scheme. The fundamental principle involved is that of centralizing the power-generating plant and concentrating it into a few large units where the energy can be generated under more economical conditions than in small units, and transmitting the power so generated to the individual powerusers. By this means both labour and fuel are economized even where the centralized power plant depends on fuel for its motive power, and mucli more so where water is available as a motive power. This concentration and the ability to transmit and to distribute has been made possible through the agency of electricity. At first the concentration was on a small scale and limited to comparatively small areas —usually the boundary of a local authority—but for the last fifteen years the process of further concentration lias been going on at an increasing rate, and the local generating plant superseded by a larger centralized plant in the same way that the individual power plant was superseded by the local generating plant. That the advantages are substantial is proved bj- the rapid growth of power-supply undertakings and the enormous dimensions to which they have attained. The conclusion one arrives at on regarding this evolutionary process and the principles involved is that the generation of electricity should be concentrated to the greatest possible extent. Hearing this principle in mind, and having regard to the state of the art of transmission of energy at the present time, it may be stated that, regarded as a purely engineering proposition, it is quite possible and feasible to supply the whole of the North Island from one single source, more or less centrally situated, but there are several objections to this course which render it inadvisable. One is that there is no single source of power in the North Island which can be regarded as sufficient for all time, so that even if one source were to be selected for the time being, sooner or later it would require to be supplemented by the development of other sources. Another objection is that the distances of transmission resulting from the development of a single source, whilst not excessive, are yet somewhat great for the amount of power at present to be transmitted. This objection, whilst valid, is not a vital one; but another objection which is vital, and is really the determining factor in the question, is the nature of the country through which a great deal of the transmission-lines would require to be brought. A single source of supply would involve the erection of some hundreds of miles of transmission-lines over broken country of such a nature as to offer a serious obstacle in the way of repair and maintenance; and, having in view the importance of maintaining a continuous and uninterrupted supply, it is an essential condition that the transmission-lines should be as accessible as possible. It is, I think, clear that a supply from a single source is not the best solution of (lie problem of a general supply for the North Island; and the question arises as to what is the next largest possible concentration which can be effected, having regard to all circumstances. It is quite obvious that the unit should be as large as possible not only on general principles, but also on the special ground that small water-power developments are unduly costly. Generally speaking, a water-power source of less than about 10,000 horse-power cannot be economically developed. It is quite true that there exist quite a number of small water-power plants that are more economical than steam in their respective districts, depending upon the price of coal and the extent to which the power is used; but when it comes to a general supply to a large district which oarries with it the necessity of adequate storage to maintain the supply at all times, a small-power plant is found to be unduly expensive in first CQst, whilst the cost of operation, attendance, &c, is much the same for a small plant as for a large plant. All things considered, the capital cost of headworks, power-station, and plant, including everything up to the point of transmission, should not exceed £20 per horse-power of plant, otherwise, when account is taken of the cost of transmission, the extent of the capital expenditure will tend to swamp the advantages to lie derived from substituting water-power for fuel. Having in view the principles set forth, the scheme which best satisfies all requirements is one in which, at the outset, three water-power sources would be developed for supplying respectively the Auokland District, the Hawke's Bay District, and the Wellington District. These sources would in the ordinary course of development be linked up together, and by reinforcing each other provide additional guarantee of continuity of supply. Regarding the source of power for Hawke's Bay District, undoubtedly the best is Waikaremoana. The amount of power obtainable from this source is greatly in excess of the requirements of this district, and it should be regarded as a supplementary source for supplying the

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