Water Supply.

Christchurch, and, in fact, most of Canterbury, is bountifully supplied with water of the best quality. According to Professor Hutton, Curator of the Christchurch Museum, the geological formation of the site of Christchurch and of much of the Plains consists of beds of clay, impervious to water, alternating with layers of shingle and sand, through which percolates the water from the hills and the rivers. The formation is, of course, alluvial, and the clay being carried further than the other materials has closed over the ends of the layers of sand and shingle, and formed a large series of water-tight reservoirs. To get a flow of water, all that is necessary is to sink a pipe until it reaches the underground supply, and the water then rises to a level, depending upon the level from which it is derived. There are three strata so far worked in this way: the first stratum at a depth of about 85 feet, the second from 170 to 210 feet, and the “deep” stratum from 210 to 350 feet. The second stratum supply seems smaller than the first, as its level is more quickly affected by sinking new wells.

The shingle and sand through which the water percolates forms a great page 44 natural filter bed, and the depth from which it rises ensures a low temperature. It is in most parts of the plains quite soft and free from mineral impurities, and hardly any country in the world can boast of a water supply so pure, so continuous, and involving such small expense.

It is difficult to get any accurate evidence about the level of the supply or its diminution. The value of the calculations made depends largely upon the season of the year. However, there is no doubt that since 1864, when the sinking of artesians began, the flow has fallen about eight feet. It fell about three feet from 1864 to 1885. Professor Hutton points out that this does not mean that the supply is decreasing; but that a constantly increasing demand is made upon it. In 1895 it was stated by a good practical authority that there were in and about Christchurch and suburbs about 7000 first stratum wells. These discharged on the average about two gallons each per minute, giving an aggregate of about twenty million gallons per day, which far exceeds the supply used by any city in the world. A supply of thirty gallons per day would be far more than sufficient for every inhabitant. In 1895 this would have meant that 1,500,000 gallons were used per day; and the balance of the twenty millions was, in a sense, wasted. At that time there were said to be about 300 second stratum wells in and around Christchurch; and competent judges declared that at least one well per day was then going down to the first stratum, and one per week to the second stratum. Such a constant drain could not fail to affect the level of the supply. When the second stratum was first tapped at 194 feet, the water rose eleven feet above the surface; by 1895 it was necessary to sink 250 feet to get such a rise. When the water is struck at a favourable spot it rushes from the pipe in a sparkling icy stream, a marvellous sight to those accustomed to the droughts of Australia and other less favoured lands. But there is a great danger that through the reckless waste of the present generation many of these advantages may be denied to their successors.

Some further figures may convey a more adequate idea of the enormous supply and the extent to which it is abused. In 1897 it was calculated that there were in Christchurch City (without suburbs) 4000 wells, giving about five million gallons daily. The city population was about 17,000, and at twenty gallons per day this would mean that about one-fifteenth of the supply was used, and the balance (at least 4,000,000 gallons) ran to waste. At twenty gallons per head a day, the supply at that time was sufficient for a population of 250,000, or a city of the size of Melbourne. Another aspect of the case is presented by the fact that some of the second stratum wells flow at the rate of 40,000 gallons in twentyfour hours. Two six-inch lower stratum wells, similar to the wells in Victoria page 45 Square, would give a supply of 384,000 gallons, which would he ample for the whole of Christchurch City. This suggests that it might easily be possible to conserve the supply, and at the same time afford the city at least all the advantages that it now enjoys. At present, with thousands of artesians running night and day, the question of conservation, though important, is a difficult one.

Before dealing with the cognate subject of drainage, it may be well to mention a matter connected with the Canterbury water supply, which, while it has little to do with Christchurch itself, has a most important bearing upon the future of the province as a whole. The question of irrigation is, for the Canterbury Plains, a matter of vital importance. Large stretches of the Plains are so dry as to be in their natural state almost useless for either agricultural or pastoral purposes. But the large number and great volume of the rivers affords a means of remedying this natural defect. Between the Rakaia and the Ashburton, the Ashburton and the Hinds, the Hinds and the Rangitata, land once almost useless has been made by irrigation, productive and valuable. The work was first taken in hand in 1878 by the Ashburton County Council, and a scheme of irrigation was inaugurated by which every unwatered portion of the country has been brought within easy reach of a water-race. At first the water was intended only for stock, and needed filtering for domestic purposes. But now every farm in the county has a secure water supply. The system has been extended to other counties, and enlarged to suit the requirements of agriculture. In Selwyn a charge of from 8s 4d to 25s for 100 acres is made for water; in Ashburton about £3 is the fee for one mile of race per year; in Geraldine 7d per acre, with water rates, is charged, and in Waimate the races are maintained by an annual charge on the value of the lands watered. Altogether, in these four counties, over one million acres are watered by 2796 miles of water-races, distributing at least 200 million gallons every twenty-four hours. The cost per acre watered varies from 1s 2d to 4s 7d; and the total cost of the system has been considerably over £120,000. But the results are truly astonishing. In the words of an experienced old colonist, “water has changed the whole face of nature in the districts that now enjoy its benefits, and on the Plains life that was hardly tolerable before is now worth living.” The splendid success of irrigation, as far as it has gone, presages an even brighter history for the province in the future.