MR GORDON'S REPLY ON THE CITY WATER SUPPLY AND DRAINAGE.

Evening Star, Issue 4180, 20 July 1876, Page 4

MR GORDON'S REPLY ON THE CITY WATER SUPPLY AND DRAINAGE.

... is thqrcport of Mr Gordon, Ouief Engineer of Victorian Water Supply, upon the Pity ■water supply and drainage,, which was brought up at yesterday’s ordinary .. meeting of the City Council Victorian Water Supply, • • Chief Ffhgihfeer’s Office, Melbourne, May 2(5, 187b. Sir,—ln accordance withrthe -request cou- , tained-in.your, letter ■of the l6tb February - T I have the honor’to submit to the Ci'.y ..Council':the "following report on the water ■* "knpply and:■ drainage of Dunedin, premising that in the present state of the information and data available my remarks can only extend tp the general principles which I think should'guide the Council in carrying out the f»T,. and that th.e detail*must be arranged by the Council’s Engineer ".alter the necessary careful preliminary surveys have been made.-

f ‘ 11, WATER SUPPLY. , j 2. I observe from y6ur. letter of the 18th « J ' J; ApriLtodits enclosures that it is desired to fo vide*for a very large prospective increase the population to be supplied 100,000. is little doubt; that this princisound one, there must be accepted with it a’high rate, of cost per head of the population to be supplied at first. It will >-’• v, BfiSriyfJalways be cheaper to lay down mains and sub mains of sufficient diameter at once /r . ,rather than double them or replace them by larger ones afterwards. I also notice that it desired to supply water at a higher leyel.febau the present works will command then, the population at 100,000,- tholeast quantity of water that ought to be provided for summer supply k six million gallons per diem, and a storage „ ab °ut eight hundred 7 million ‘ leßtfwhat can be reckoned on as the

minimum' summer tupply pf 120 days from whatever source inay be chosen for the . i »«pply. 4. The sources which, could bo employed for increasing the supply by means of the present works are ; Ist, the Water-of-Leith; and-.’2nd, the streams, forming the -head of - thfe Waitati stream. Only the flood' waters of the Watcr-of-Leith could be reckoned on; there would be no supply duringthe summer months from- this source, unless either by . the ponstruction, of. reservpi. son the river, : di’ by compensating and Securing the full supply for the Waterworks. _.6. At the time of my visit streams called No. 1 and 2 (the second of the sources just • mentioned), were, by an approximate measurement, discharging together rather less than W : cubic feet per minute, or about bOO.OOO gallons in the twenty-fonr hours. Mr M'Kerrow informed me that the streams wore never lower and seldom much higher, but as both would have to be intercepted at ’ . >.higher level than where the above measure

meat vfts taken, I do not think they should be considered good for more than, say 700.000 £ a.'ions a day in summer,’ and 750.000 in winter,. - ■ 6. The present supply is stated to bo one , an,d a-half million gallons, and in summer ‘ " 2,000,000 gallons a day ; arid from this J oonolude that the addition of the above . ' streams to the present sources of .tupp y would yield a sutliciont quantity of water, if properly regular d, to a population of 46,000, viz.,’ fiO gallons per head per day in summer and 40 in winter, but would be quite in- • SMlficieit for the number for which it is proposed to provide. It would therefore eventually become necessary to make use of : tbe’.Waief'Of-Lnith, the summer discharge

,of which is said to be 2.7 million gallons in 24 hours, and. in.the absence of careful daily gaugings it is even doubtful whether the whole discharge of the tipper part of the Waiter-of-Leith added to the other sources would be sufficient to provide 40 gallons in winter and 60. in summer per head per day to 100,000 persons, or a total of 2,000,000,000 gallons pep hjinuni. If the gaugings shqw that the flood discharge would be sufficient to make up the summer deficiency, the storage capacity .must be at least 475,000,000*ga110n5. V. The -area of ■ the present gathering p o: acres,, and the annual ischarge fromlity according to the information furnished with your letter of April 18, beingffiearly T00,000,000 gallons, itfifaay, I be assumed that in years such as 1875 the Water-df-Leith would, yield, from 1,600 acres, about 930 million- gallons ; add available supply of present area, 607 million gallons ; the two. streams, 264 million ; total; I,Bol' million gallons, or , sufficient for 95,Q60 persons; 930 million gjllons'is equivalent to a’ discharge of 231 ■inches olf 1,600 acres, -if the rainfall of 1875 was abundant, then the deficiency in ordinary ycars-would have to be prov" idl'd for by au -extra .storage. of 450/millioii gallons - f dr equalising good and bad? years, 'as i the 475 _ million ga loiis stoiage men--..tionod above -would only compensate for the diherence of summer and winter supply. Gaugings OvOf a succession of years will determine whether this source addpd to the present and to streams Nos. 1 and 2 can be considered sufficient, or whether it will be nicest ary to. extend .the channel inteicepting the tributarie.rffif'-iffie Waitati.

8. In the above remarks I have not alluded to Mr - McGregor’s plan,- for two reasons—•first, that it seems to me to involve immediately one of two very important courses, either the construction of a.reservoir of a much larger capacity than Mr M‘Gregor proposes, dr the purchase of the mill interests ; and secondly, that, as you state it is hot intended to supply water outside the limits which can be commanded by the present 1 wort, s, the double system proposed by Mr M‘Gregor is unnecessary. Tue same applies to the report of Messrs Barr and Oliver.

8. I would recommend to the attention of the City Council the following considerations ; That it will certainly be expensive to purchase the rights of the •millownefs that it will bo impossible to provide water for the mills in addition to that required for a largely increased population ; that on tho other hand'a very cons derable increase, could be obtained at a small expense by Hading the water of tho two streams"over the summit of tho watershed to tho present reservoir, and that the supply Would tiffin, ■ if properly regulated, be equal iu all probab lity to that required by 45,000 persons ; j#p r that, in a short time, and at ! a reasonable expense, the supply would be : increased as much as would be needed for some years at least; and the works B j nndCrtalteh ‘'Would iorm part of.the wholo scheme that would eventually be required for the large contemplated increase in "the supply. 10. iShould the City Council think it well to act on these suggestions, and confine their works for tho present to tho bringing in bf the water of streams Xos. 1 and 2, I would recommend that immediate steps be taken to reserve the wholo of the drainage ar<\a of these streams, and of the next one or two on the same slope ; that the City Council should obtain by Act of Parliament tho right to tho wholo of tho water oi these streams above the proposed offtakes, and to all tho water m the Water of Leith not at present used by tho mills, and to that which may be brought into tho Water of Leith from other sources such as the aqueduct from the streams just mentioned. Tho i ity Council has already powers, to purchase the existing water rights when it is desirable to do so. The supply is so little, if at all, in exoessVffif whatthc demand will be (assuming the populat on to increase to .100, GOO), that every precaution should ho taken to secure a right to all tho water that can be brought into or stored in the W.-ter-of-Leitb, or codected from other sources.

11. The increased consumption will necessitate a modification of the reticulation in ..the direction of increased diameter of mains, and i would strongly recommend the principle of leading tho water to the higher parts of the district first, by mains with which no house services or sub-mains communicate, and distributing the water breticulation pipes downward from these higher points.. By this plan the supply can be better regulated when there is a great demand for water, and the higher sub mains need never be emptied by an unusual draught on the lower pipes. If suitable places are it will be very convenient to have service reservoirs, holding in the aggregate twenty-four hours’ supply, at levels as little below the present reservoir as would be consistent with a good current iu the main supplying them ; but 1 do not consider this point so essential in Dunedin as it generally is, because here tho reservoir is very near the town. J

12. Strict regulations should also be made and ci forced against the abuse and waste of water; and a strict supervision of fittings should be maintained. L)efi otiv r e fittings such leaky taps, defective ball-cocks, and the like, are the greatest cause of waste of water. The Council should have the right to require consumers to have meters if thought necessary. (The usual rate to bo the minimum sum paid, and all water used above the quantity so reckoned at 2s per 1,000 gallons charged for.) I send herewith for your information the regulations in force in Melbourne, (feeiono and C;u tlenir-ine, and an extract from some recent bye-lawa made in Liverpool ; also a statement of the rates in force under the Victorian Water Supply Act. [To be continued.]