DROUGHT RISK.

Auckland Star, Volume LXIX, Issue 220, 17 September 1938, Page 15

DROUGHT RISK.

WATER SUPPLY.

NORTH SHORE PROBLEM.

TrpPE,t pbofosai.

H Y w m•£ "" outlsned by Mr. .F. W. Me.kip, Mayor of Devonport and chairman of the North Shore Borouphs TV ater Board, that two season, of drought might cause a serious shortage in the water supply D f Devonport Takapuna, Northcote and Birkenhead local authorities on the North Shore are at present considering alternative schemes to augment the present supply. rhitt supply conies entirely from Lake I upuke, which has been stated ti l! 7 »' t the Southern Hemisphere— hut with growing population in the residential suburbs on that side of the Waitemata Harbour the demands on the lake are too great for safety. To assist I offered t' ,C A "V k,a " fl Cit . v Council has t .lJ.r ""PP'y water from the Wai•r mM> U ' Ut at a COf,t " f 1/ p r I(XM> gallons, (ienerally this is considered a reasonable offer in yiew of the ore,.instances, but it would raise water rates in the boroughs concerned to such an extent that alternatives are bciii" considered. By the adoption of o, Co Sterne, known as the Wairau scheme it is considered that the extra cost could be reduced to 2d per 1000 gallons, but that at P th° Je T a,C ° th<>r fnctors a L ~„ present time are matters concerned. ' a,,, °" g thc lwal Big Rise in Cost. Discussing the situation to-day, Mr. demand P B ° - r, ' at the demand on I upuke become that a couple Knr.T' vi y - wcathor '"teht leave the Isoith Shore in grave difficulty with regard to water supply. The City Council had made an offer to supply wa W that th? 1(X>0 .« but he considered that this would raise the rate to such an extent that every other avenue of supply should be explored before a decision was made.

At the present time all the North Shore boroughs paid for water at the rate of 1/8 per 1000 gallons. To accept the city offer would mean that the cost in the various boroughs would be as follows:—Devonport, 2/8 per 1000 gallons, (increase 1/2); Takapuntf, 2/5 per 1000 gallons, (increase lid); Northcote and Birkenhead, about 2/ per 1000 gallons (increase 6d). The water would be brought in a pipeline passing through Hobsonville, and thence through Northcote and inter vening boroughs to Devonport. Capital investments in existing systems in the various areas made for differences in costs.

To this scheme, said Mr. Meikle, only one alternative appeared to be practical, and that was the Scheme known as the Wairau scheme. The Water Board had asked the Public Works Department to report upon it some time ago. At the tune, at the request of the Minister, the report had been kept as -a confidential one, but the present Government had given permission for the report to be made known to the local bodies on the Shore. Certain aspects had not beoa completely investigated at the time of that report, and the Devonport Borough Council had taken the matter np. Data had been collected over 4 period of a year and it was now Cssible to place a definite scheme fofs the local bodies. llay Be Commission. 1 am of the opinion that water should bo a* cheap as possible," said Mr. Meikle," and I am calling a conference shortly to go into the question. Every alternative should be considered before wo either turn, down or accept the city offer. We could lay all the information available from a conference of the local bodies here before an impartial tribunal—say, an engineer with specialised knowledge, a legal authority and a Government representative. Such a commission could give us an unprejudiced opinion on the whole question. Some conclusion has to be arrived at." Other ' schemes had been considered, he said, but for one reason and another were not now practicable. With a population of 26,000 people on the North Shore the demand for water had grown to such an extent that it was more than the lake could supply. Briefly expressed, the Wairau scheme proposes the erection of a dam at the junction of two valleys on the Upper Wairau creek, collecting the run-oft and using it to augment Lake Pupuke during the winter months. It is not proposed at the start to Impound water, but merely to divert it to the lake when water of low turbidity was available. It is stated that it would be about 1970 before it would be necessary to consider collecting the wholS yield of the Upper Wairau watershed. It was intended also to so control the discharge into the lake that only water of low turbidity would l-e delivered. Tests of the water from t):e Wairau valley had proved it to be similar to the water from the Waitakere catchment area. For 40 Years Ahead. "There is sufficient water in that area to supply the whole of the North Shore for the next forty years, so the engineers report," said Mr. Meikle. "That is based on an increase in population of 2 per cent per annum, and we do not consider that the rate of increase will be that high. It should be emphasised that the scheme ha-s nothing to do with the lower portion of the Wairau Stream, where there is possibility of pollution. Only a low dam is proposed—just to hold the water sufficiently long to allow sedimentation, probably 48 hours. The dam would probably not be required for the first ten or twelve years." In 1933 the estimated cost of the scheme wss £31,750, and the report of the district engineer (Mr. F.-S. Dyson)

0 m stated: "Upper Wairau Creek would apparently be a satisfactory source as a supplementary supply for the lake, and provide for the anticipated demands of tlie increased population for a period of at least 40 years, at the same time allowing the lake to till within a period of approximately three years from the date of the inauguration of the scheme." This conclusion was based on a theoretical co-efficient of run-off from tlie catchment, and it is stated now that gauge readings taken over a period of a year give an estimate of 750,000,000 gallons per annum yield from the Wairau and lake combined, based on mean rainfall. Mr. Meikle said that it was considered that the lake could be brought to its original level in the period of a year. Objections Raised. Objection* so far raised to the scheme are stated to arise from financial considerations concerning various boroughs. Certain of the land about Lake Pupuke cannot be fully utilised because of its proximity to the water supply, and the hardship suffered is recognised by the Government in reducing the rate level to about half what it would otherwise be. The reservation of about four chains of land about the high-water mark of the lake, to protect the water from pollution might result in a further loss of revenue to the borough concerned. It is considered, however, that a commission would take all these questions into the scope of its inquiry and offer a satisfactory solution.

The urgency of the work was stated by Mr. Dyson in 1933, as follows: "It is considered to be appropriate on account of the acute position regarding a good adequate water supply, to refer to the urgent necessity for the North Shore communities to take immediate concerted action in the natnre of finalising proposals for a water scheme of sufficient capacity, which will assure an ample supply of hygienic and palatable water for the present and future population of the district."