FUTURE WATER SUPPLY.

New Zealand Herald, Volume LX, Issue 18521, 4 October 1923, Page 10

FUTURE WATER SUPPLY.

CITY'S GROWING NEEDS.

NEW RESERVOIR PROPOSED

SITE IN HUIA VALLEY.

CITY COUNCIL INSPECTION.

\ Proposals ■ recently ;: made ;' to augment Auckland's water supply by the impounding of a large area of. bush country in the .Huia Valley are to be considered by the City Council this evening.- Tho council has always ; followed oa s ; vigorous ! and; forward policy in tho matter of water supply and has carried out ' somo huge undertakings, tho most recent of which was the j building of the Nihotupu impounding dam, I but the; phenomenal growth of the: city ! has made increasing demands on the water 1 sources, and to-day the daily consumption is approximately 64 million gallons, while j the present ' available > supply may be I roughly stated 'at about 8^; million gallons. [Several years ago the council "had 'a comI prehensive scheme drawn up and 1 this contemplated- tho utilisation of several of the largo valleys on the Manukau Watershed [ of the Waitakero Ranges, the scheme being such as would provide for the needs of I a very large city. 'Nihotupu Valley was rone- of the catchment areas considered in I this scheme and 'now that the impounding i operations have, been .completed in this | area the council is taming its attention,to the Hiiia Valley which is the next large : depression in the mountains over ; the divide; to the' west. Surveys have been, ; made to determine the best site for an imi pounding dam, and yesterday the Mayor, Mr. J. H. Gunson, and ; members of the. City Councils; accompanied by tho city i engineer, Mr. W. E. Bush, and the assisti ant city engineer, Mr.' J. Tyler, visited the '■locality for the purpose of acquainting I.themselves with the conditions prevailing .there.'-;;: n . _ i Nihotupu. Dam in, Good Order. ;

The party first of.all visited the Nihotupu dam, where it was seen that all the country .-immediately - surrounding the artificial lake had been thoroughly cleaned up and all traces of the workmen removed. Much of the modern plant sused •in the construction of the wall has been removed to the depot at Muddy Creek and the remainder stored at a point above the quarry site,; pending the beginning of operations in the Huia. The imprisoned water is now ljlft. up the face of the retaining f wall, showing an accumulation of 450 million gallons of water. The water has to rise another four feet to reach the lip of the spillway by- which time the total capacity of 530 million gallons will have been reached. The whole area has a decidedly clean and wholesome appearance, and as the ; watershed is completely fenced ■in there is little or :no » risk of - contamination from outside sources. ;•;*': ■

i - The party crossed over the wall and [climbed the ridge separating the Nihotupu I and Huia'* watersheds, and wended their j way by a primitive track to the floor of the- valley until they reached a point close | to the junction of the Huia- and Castles Creeks.'. The journey was then continued i steeply upward in a Kne parallel to; the ! Huia Stream for a distance of a mile and a-quarter, where the site selected for, .the proposed impounding dam was viewed. All the way up the valley it; was noted that '■ the water in the stream was sparkling and beautifully clear, ; and those who tested it found it : delightfully cool and ■ palatable. It was generally agreed that the Huia was the best stream in the Waitakeres, for in addition to the large catchment area above the suggested dam site the water is undoubtedly of the finestquality.; Proposed Site of New Dam. ::>■ The point selected by the experts for the construction of the dam is a few yards below an old wooden dam formerly used for storing kauri? 1 logs, and still standing, f although 7 in/Van; advanced state ,of decay. l /At;this; point a large bluff 'abuts on the; stream, thus:., narrowing the distance to /be bridged by v the impounding wall which,. if constructed, < will ibe a somewhat smaller undertaking than '; the Nihotupu: wall. V Its i height from the bed of the stream; to the; spillway would probably be 'about 120 feet, and in ilength it- would be approximately about twothirds of the span of the Nihotupu dam. It was- roughly estimated that its: construction .would : call for about 50,000 cubic yards of I concrete, :as ; against 76,000 yards used iii the ; dam in the adjoining valley. The area reserved for the new reservoir is 2000 acres, all in : virgin bush, and ' it is estimated that, with \ r the ; wall vof the dimensions - suggested, the reservoir would hold 500- million gallons. ; The level of thev impounded water / would V then <be approximately, 700 feet above sea level, permitting of a ; supply by gravitation to Khyber Pass. ' ; The Huia Valley has boen systematically % worked for the large timber trees, and to-day, while there are many magnificent kauris \, and ; rimu trees J growing on the heavily- slopes, they are isolated survivors, and there ; to-day, .i in all probability, because it; did not pay yto fell them ;and make special preparations for their conveyance to tide water.. Th*> closing of the watershed ; to the public--a necessary precaution, to safeguard. the purity:, of the;, water—would ensure the . safety of these relics; of,a : great forest, and regeneration would be ; steadily carried 'oh, as kauri, ; rimu, and (totara' saplings are growing on all sides,•.:■: and ■;'..•'•: if given reasonable protection from animals and the ; risk of fire, should develop into stately trees. '

;W Development of ■Waitakerev.ffchemes.; ; '-' It '■ is 23 years since, the:.: City . Council first looked to the Waitukeres for the city water-supply,^: and from that time the development ;has' been( steady. . tvln the fyear 1902 a - supply was drawn from( the Nihotupu Valley by piping direct from the stream. Six, years later the W'aitakere dam, which impounded 220 million gallons of water, was,constructed.. •Then ( followed the building of the great Nihotupu r dam, which was opened this. year, . and is now filling up to - its .fullest ',, capacity. While this work (was in pio "gress;-(an auxiliary dam, with ;a( capacity of 70 ; million • gallons, ; was constructed at the head of the; Nihotupu Valley. "; The city has thus an : assured sunoly of 820 million gallons of, water in storu. in addition to the ample flow : from uie streams v serving \ the existing reservoirs. With a further reserve of 500 millions of; gallons provided by the proposed reservoir at the 'Huia., the city would have store : of 1320; million gallons, '■- which l (.- ; should suffice for the (needs of the citizens, for ; the -next ten or fifteen years:- -(■