THE MELBOURNE WATER SUPPLY.

New Zealand Herald, Volume IX, Issue 2519, 21 February 1872, Page 5

THE MELBOURNE WATER SUPPLY.

[FBOJI THE " AEGT/S "j a .second mam was carried through the embankment or the purpa.es of/fatar extension, which has not vet bppn made. Thodiamater of the nJn pipe™ the reservoir is 33in., bnt after somemiles of distance it is reduced to 2/in., on a calculation, making allowance for friction that a body of water whicli has travelled a certain length will be conveyed as rapidly in a 27in., as in a33in. main. At Preston the main is farther reduced to a diameter of 2iin. There is a service reservoir at Preston, seven miles from Melbourne, designed to maintain tho city supply in the event of any accident occurring to the main between this point and Yan Yean. Ihis reservoir is 150 ft. above the highest ground in Melbourne and 300 ft. abore the Zi'T™ 1S 20ft - dce P and has a capacity of 14,000,000 gal. A second main, 24in. m diameter, connects this scource of supply with the city. It was originally thought that the Preston reservoir could be filled every night onfche supposition that there would bo I'ttledemaudonthemainsdurinothe usual period of rest. The Yan YeaS main dischargos 6,000,000 gals, every 12 hours, and it was estimated that only 2,000,000 gals, or 3,000,000 gals, would be required in the night time, leavinjr 3,000,000 gals, to be stored in the reservoir at Preston. That would provide something like 10,000,000 gals, for each day's consumption, but during the veryhot weather it has been found that the quantity of water consumed is as great in the night as in the day. The result of this waste—for the insufficient pressure is chiefly attributed to flowing taps used for purposes of irrigation—is that the Prestos reservoir is always exhausted at such times, and the whole supply is dependent on one mniu, the second main from Preston to Melbourne being of course useless. The obvious remedy ig the construction of a second main or open aqueduct from the Yan Yean reservoir to Preatcu, of equal capacity with the oxistina; main.

The failure of the water supply in Melbourne at the time when it is most wanted has been attributed to a variety of causes. The real cause of the difficulty with, the present means of supply is to be looked for in the wasteful use of the water, the consumption often reaching 120 gals, per head a day. There are 400 miles of reticulation pipes laid in Melbourne and the suburbs. When it is considered that a I inch pipe, the average size of the service pipes, will deliver from 600 gah. to 1,000 gals, per hour, according to pressure, it will readily be seen that the demands of the 40,000 tenements supplied are capable of being of a very extravagant character. If it is borne in mind that many of the traps are left running full bore through, the night, to water gardens and for other purposes, in addition to the escape from fire-plugs, it is not surprising that higher localities should be temporarily deprived of the supply. There is also a great loss from leakage. One week's inspection of the city services a short {{me ago resulted in the discoyj— of 200 burst pipo3. The inch nozzle attached to the hose and hydrant for watering the streets will deliver 2,000 gals, au hour. This watering of the streets, with the Yau Yean at a lowpressure, is a needless waste. The Public Works department has no power to stop the practice, and it would be very desirable to amend tho 216 th section of the Public Works Statute of 1865, so as to provide that the streets should only be watered in this way after the gauge has reached a certain pressure

which the department knows will supply tlio whole district. On hot-wind days, when tliere has been an unusual demand on the mains, men have been employed watering the streets in the usual way, after the department has availed itseif of the last drop in the tank on Eastern hill, a supply in the first instance intended solely for a case of emergency, and which is ,!only turned into the pipes when the registered pressure shows them to be empty. ' r he present charge for water is Is. per 1,000 gal., and tie cost decreases, in. proportion to tiie amount cousuined, until it reaches 4Jd. per 1.000 gal. Withlimited supply it i* questionable whether this tariff should not be lightly increased. But the abuses cen never be corrected until the consumers are supplied by meter. Mr. .Edward L".nge, the superintending engineer reports, that tliere at present 900 meters iu use, varying in size from half an inch to six inches, and that about 300,000,000 gal. per annum are supplied by meter. The Victorian railways use about 20,000,000 gal. per annum; the sugar works, 8.000.000 gal. ; brewers consume from 5,000,000 gal. to 7,000,000 gal.; Hobson's Bay Railway Company, 7,0O),000 gal.; Meat-preserving Company G,0J0,000 gal. ; and gas-works 3,000,000 gal.

The mains across the Yarra being small, a great pressure is required to convey the water to districts south of the river. When anything occurs to reduce the pressure, it is these localities which suffer first. The water is conveyed to Prahran by a 12in. main, to Handriilge by a 9in. main, and to St. Xilda and Brighton by a 10in. main. When there is a second main from the Yau Yean to Preston, it will be necessary to ext> nd the present main serosa to St. Kilda and South Yarra, and this would cure all irregularity in the supply. It is estimated that the cost of this work, with a main from the Yau Yean of equal capacity witli the existing one, would be £200,000, aad there is little doubt that with a largely increased demand for water every year, the outlay would bring an excellent return. It would be necessary to order pipes to be made in r.ngland, and the scheme could scarcely be carried out in less than two years. Mr. C. J. Taylor, however, late engineer at the Yaa Yean, who was recently instructed to report on the subject, recommends that instead of a second main being constructed water should be conveyed from the reservoir by an open aqueduct and flumiug ; a plan which would cost 40 per emit, less than that of tiie main, while it; would have the great advantage of saving from nine to 12 months' time, and of being completed at a sufficiently early date to meet the necessities of next summer. A. larger supply could be conveyed in this way thau by main, and it is thought that the quality of the water would be improved by passing along channels cut through basalt, which would be the case, except when the inequalities of the ground required fluming. The Preston re<ervoir would tiien be kept constantly full, the two 21 inch pipes supplying Melbourne would always be charged/and if it should become necessary to further increase the supply to Melbourne, a third main could be connected with the lower reservoir. Mr. Wardell, the Inspector-general of Public Works, has advise.) the Minister at the head ot his department, that authority be Riven him to have the necessary levels taken at ouce to determine whether this scheme is practicable, and to estimate the cost, and if it is found practicable, that not a moment should be lost in giving effect to it.