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Report on the Geology & Gold Fields of Otago

Water Supply

page 120

Water Supply.

The water supply of towns by artesian wells is the only geological question that need be discussed under this head, and Invercargill and Riverton are the only towns where the conditions appear to be favourable for obtaining water by this means. These towns are built on a series of gravels, silts, and clays, which rise in altitude from the sea, until they skirt round the bases of the Hokanui and Moonlight Ranges. These gravels rest upon a tolerably level platform of sandstones similar to those in the Hokanuis, and as these rocks appear near the surface in the Seaward Downs, it is probable that they are present at no very great depth under Invercargill. Rain water from the inland mountains probably percolates through the lower beds of the gravel series, and finds its way slowly into the sea; and if a bed of clay underlies Inrercargill, and extends far enough inland to rise to a higher level than the town, the conditions will be favorable for obtaining water by artesian wells. For if this clay were pierced by a bore-hole, the underlying water would rise up through it in preference to forcing its way out to sea. Whether this assumed bed of clay exists or not it is of course impossible to say, but the chances are in favour of it, and it is well worth a trial.