— 153 Cost of Irrigation.

Tke final comparison of pumping units must be made on a financial basis, and in the choice of a type of plant for certain conditions not only must the costs of available fuels be considered, but also wages, repairs, depreciation, and interest on capital outlay.

Local variations in the cost of fuel, lubricating oils, transport and wages may materially influence costs of irrigation, and findings in one district will only have a limited application. In this country, where repairs are an expensive item, a plant must possess the essential quality of reliability, and particularly so if there is only a single pumping unit, as serious engine trouble may jeopardise the whole of the crops under irrigation.

The maximum financial economy in running costs is a sine qua non of profitable pumping. The margin of profit may be seriously influenced by variations in hft and reduction in the area irrigated. To secure the greatest economy the pumping unit must be run at its full capacity, and the largest possible area must be irrigated. In this way alone fixed charges, such as wages and interest, have the widest incidence obtainable.

Descriptions of the units, together with their test performances, have already been furnished, and it is now intended to consider in detail their actual working performances and the costs of irrigation. For simplicity and facility of comparison these have been shown in tabular form. It is regrettable that it has not been possible to include Plant No. 4, as, owing to its short period of service, any figures given would be practically valueless for comparative purposes. It may be said, however, that its performances during the few days since its installation give promise of its being the most economical plant yet erected.