THE MALVERN WATER RACE.

Globe, Volume XX, Issue 1603, 9 April 1879, Page 3

THE MALVERN WATER RACE.

The extensive work of constructing a water race through a considerable area of the northern part of the Canterbury Plains is steadily progrossing, and now presents proportions which would surprise many who have not recently visited the locality to which the operations are chiefly confined. The scheme of irrigating the Plains by such means was mooted years ago, and a considerable time elapsed before the work was finally decided on by the Provincial Council of Canterbury, and undertaken, under the superintendence of Mr Thornton, then the Government engineer. On the abolition of provincialism the work was taken over by the County Council of Selwyn, and placed under the control of Mr J Webster, who will carry it out to its completion. To those acquainted with the district extending from Rolleston to the Kowai Pass, it should be unnecessary to point out how beneficial will be a supply of water such as this race will provide; and to those who do not know the district and its great necessities, it will bo sufficient to say that a naturally fine extent of country, with a soil of remarkable richness has been kept back for want of moisture. the means at comra-md of the settlers to supply themselves with water being quite inadequate. The work now being tarried forward with as much speed as the circumstances of the country will permit, will therefore enhance the value of property and contribute to the advancement of the district in every way.

The woks of the Malvern water race arc being divided into sections, and are numbered consecutively as the various contracts are let. The present contract, No. 3, is two miles sixtythree chains in length, extending to within about three-quart rs of a mile of Sheffield, and will be completed within a few days. It consists of an open race, I4ft. wide at the bottom, with slopes of two to one. The fall in the country is here about 40ft. per mile, and to prevent scour falls have been placed at such distances that the excavation will never be less than 2ft, in depth, this being _ estimated as necessary to carry the maximum volume of water without overflowing. Each fall has a direct drop of 2it., and the water is received on a cushion, the force being thus expended previous to passing on through the race in the direction of the next fall. Wherever the race is crossed by a road a substantial bridge is erected, and it is proposed to carry surface drainage across the race in flumes. This course is to be adopted with the view of preserving the water in as pure a state as possible, so that it may be conveyed to the lower Plains in a state fit for domestic use. Contract No. 4, which is now being prepared, will extend from Contract No. 3, nine miles sixty-four chains, which will carry the work clear of the most difficult country, and the progress after that may be expected to bo rapid. The operations now going forward are on a most extensive scale, and necessarily entail a vast amount of work, not a little of which is performed in the offices of the engineer, Mr Webster, whose collection of plans for different sections of the work, represent in 'hemselves a considerable amount of trouble and expenditure of time. Our reporter was, by the courtesy of Mr Webster, permitted to inspect the plans of contracts yet to bo done. One of these is between contract [No. 3 and the first contract starting from the dam. The incompleted portion referred to has not yet been touched, because it was found that as a temporary measure an old creek running over that distance, could be utilised, and the water was discharged into that channel until lately, when it was cut off at the dam to prevent its running to waste lower down. Connected with contracts in contemplation, a great deal of bridging will_ have to be done, the cost of which alone is estimated to be about £\ ooo. But as above stated, the more difficult portion of the work has been accomplished, and the remainder is comparatively smooth sailing. The Malvern water race derives its supply from the river Kowai at a point about six miles above its junction with the Waimakariri. A substantial concrete dam is constructed across the river, and the water is collected and diverted through the sluice gates on the south bank into a tunnel, driven through the high terrace. This tunnel is half a mile in length, and built of brick. _ A concrete invert is now being laid as a protection against the excessive wear caused by shingle. From the tunnel the water will be carried in the open race through the plains lying between Sheffield, Rolleston, and Relwyn.