Underground Water

Press, Volume CVI, Issue 31238, 9 December 1966, Page 16

Underground Water

Melbourne visitors to Christchurch are surprised to find water flowing in the storm-water channels in mid-summer; mariners declare there is no softer water anywhere than the water they take on board at Lyttelton; food and beverage manufacturers have sited their factories near Christchurch because of the known purity of its water supply. The abundance, softness, and purity of our water are so much taken for granted that few Christchurch residents appreciate the worth of this natural asset. Christchurch’s water is drawn from,artesian deposits in the shingle layers to be found virtually anywhere under the ground of the Canterbury plains. The rain which falls on the flat, level plains mostly finds its way into these shingle strata, strained and purified of any surface contamination. No attempt has ever been made to estimate the quantity of water in this vast underground reservoir, although regular checks are made of water levels and pressures in numerous wells. Ten years ago, according to the “most reliable estimates”, no more than a tenth of the available supplies was being drawn on. In the lifetime of Christchurch’s youngest present citizens, any “ shortage ” of water could be met by sinking wells in one of the deeper strata a few miles north, east, or west of existing wells. Pollution is the only threat to the Christchurch water supply. Indiscriminate discharge of industrial or domestic effluent could permeate the filtering surface layer and contaminate the underground water, at least in the higher strata. A single source of contamination could pollute the water supplies of thousands of people and damage the commercial reputations of dozens of food and beverage manufacturers. There is, perhaps, little likelihood of this happening in our time; local authorities and Government agencies police all the likely sources of contamination. But none of these authorities would guarantee that it could not happen. None of them know what protective steps are being taken in all of the other areas by all the appropriate authorities. The need for a single underground water authority, with jurisdiction over all possible sources of contamination, is obvious.

The need Is acknowledged by the Christchurch City Council and the adjoining borough and county councils, by the Christchurch Drainage Board, the North Canterbury Catchment Board, and the Regional Planning Authority; but there is little agreement on which of the existing bodies should assume this new function, or whether a new authority should be established. The latter suggestion should be ruled out if one of the existing authorities can establish a claim to competence in this field. None of the territorial local bodies, nor the Drainage Board, administers a big enough area. The Regional Planning Authority has no experience in this field. The Catchment Board is the obvious choice. Given specific powers, and some extra staff, the board would take over some of the functions, and probably some of the staff, of the other authorities at present policing, piecemeal and inadequately, the underground waters. Business interests need not fear that the board would be any more restrictive than the present authorities; it is at least possible that a more adequate knowledge of seepage, flows, and deposits will result in an easing of restrictions in many areas. The formation of an underground water authority is “extremely urgent”, according to the City Engineer (Mr P. G. Scoular), who favours the Catchment Boyd as this authority. The Water and Soil Conservation Bill would empower the board to assume this function—and the Bin win become an Act much sooner if it has the support of all Christchurch local bodies.