THE WATER SUPPLY QUESTION.

Globe, Volume XX, Issue 1552, 8 February 1879, Page 3

THE WATER SUPPLY QUESTION.

The question of an improved water supply for Christchurch is just now exciting considerable attention, and therefore it may interest our readers to be made acquainted with what is being done towards solving the problem of how to get a water supply for Christchurch. Therefore one of the staff of this journal yesterday proceeded to the locale of Mr W. White’s operations on the Waimakariri, that gentleman having submitted a scheme to the City Council, the feasibility of which the experiments now being made are intended to test. The spot selected is about eleven miles from Christchurch, and is in the bed of the Waimakariri, nearly opposite to McLean’s Island, and in a direct line from McLean’s station. After a jolting drive over shingle and boulders, the scone of operations was reached. In order to understand the description of what has been done, it will be necessary briefly to sketch the salient points of the proposal of Mr White to the City Council, and the method proposed by him to bring a water supply to the city. His proposition shortly stated is as follows :—To sink nine cylinders into the water-bearing strata under the shingle about twenty-five feet in depth. The cylinders are then to be capped by the main being connected with them, at a depth of at least, six feet below where the water in the iylinden would rise to. It is then proposed to carry the pipes down stream on piles, at a considerably less fall then the natural fall of the river, but at somewhat the same as is allowed for the pipes between the river and Christchurch, The main is to be carried down the river until the level of the pipes are above the highest known flood level. It is then carried over the bank or terrace of the river, and thence brought to Christchurch by gravitation. It will thus be seen that Mr White’s scheme does not depend upon the permanence of the bank or river bed for the stability of the work. The cylinders, it may be pointed out, are sunk into the river bed, like the piers for a bridge, on the pneumatic principle, and the main is carried on piles driven sufficiently deep below the river bed to prevent any danger of their being dislodged by flood. The steps that have been taken to prove the feasibility of this scheme are as follows : —On Tuesday last Mr White commenced borings for the purpose of testing whether there was or was not an abundant supply of water below the Waimakariri river bed for the supply of Christchurch and the suburbs, and also whether the supply would rise through vertical pipes or cylinders to the mean level of the water in the- river bed. The fi*st experiment was tried with a pipe two inches in diameter at a point in the river bed opposite Mr McLean’s station, and midway between that place and McLean’s Island. The depth of the boring was fiftythree feet, the mean level of the water at that point being eighteen inches below the river bed. So far as it was tried the experiment was a success, the water rising in the pipes to the same level, and with the aid of a No. 4 American pump it discharged fifteen gallons per minute. After five hours’ pumping the water became as clear as artesian water, and yesterday, on being tested by taste, it was found to bo as palatable as the best water in Christchurch, The next experiment was with a 1-jt inch bore, the spot selected being on the north side of McLean’s Island, and somewhat higher up the river than the place where the first boring was made. The level of the water was here about eighteen inches below the river bed, the pipes being driven about 25 feet. The water rose in the pipe about 23 feet 6 inches, this being about the mean level of the water in the river bed. This so far proved the fact which was the chief object of the experiment, viz., that the water will rise to the mean level of the water running down the river. This pipe also, with the aid of a No. 4 American pump, supplied twenty gallons per minute. These two experiments seem to show that there is a greater abundance of water in the water-bearing strata underneath the river bed midway between the north and south banks of the river, than on the side nearer McLean’s station, whore the first pipe was driven. This idea is further borne out by the fact that McLean’s well, situate about a quarter of a mile from the river bank had to bo sunk sixteen feet in depth before any water was reached, although the surface of the land is below the surface of the river-bed. The third of the series of experiments is now in course of being tried, and consists of a two inch pipe that is to be driven 25 feet down, at a spot

about it mile and a half above McLeanV station. This is only partially done ye% but it is probable that it will be completed to-clny. As to the quantity of water likely to he supplied by the proposed scheme, it may bo pointed out that the total discharge of the two-inch pipe per diem, at the present flow of twenty gallons per minute would amount to 28,800 gallons. Taking the cubical contents of the cylinders proposed to be used, at the very low rate of forty times the present flow from the two-inch pipe, a daily supply of 1,152,000 gallons is obtained.