UNDERGROUND STREAMS.

Hawera Star, Volume XLVI, 4 October 1926, Page 7

UNDERGROUND STREAMS.

WAIMAKARIRI TO CHRISTCHURCH. WHAT OF THE' RAW ARAL WATER)? The source of the abundant' supply of artesian water which is available all about the City of Christchurch, has long presented a perplexing as well as an important problem to'those; seientifie investigators who have devoted attention to it. The latest volume of the Transactions of the New Zealand Institute' contains a further paper on the subject front the' pen of Dr. I'. \Y. Hi I genclorf. and some of his conclusions as to the probability of seepage through to "hiirch from the. bed of' the Waiakarirji River will lie read with sijecial interest by those who have , at'&ejied weight to the theory that there is a considerable seepage from Lake, \\ akatipu tO' the bed of'the' Kawarau River. In a. paper .given to the institute thirty years ago, Captain Hutton concluded that rises in the Christchurch, artesian wells, apart from rain, wer e d.ueeither to water running in from the bedi of the. Waimskariri or to some stj.ll lower-water-bearing stratum leaking into the upper ones At . the* same time l he showed that the height of the water in the wells was not. affected by the height of the river, and concluded-that it was improbable that the supply, was from a leak in the river bed. j I • ■. ■ In 1912, Dr. Hilgendorf, as the result of his investigations, expressed the opinion that the water from, the Wat mrkariri does assist the wells in som e degree. The reduction of the artesian water, which was a; steadii’y marked movement at one ed some years ago, and in 191/ Dr. Hilgendorf asserted that this was due to the supply of .water from the Waiakariri and from under-drainage to- the sea. Prior to this,: Mr R. Speight had come to the conclusion that the artesian, water of . Christchurch, comes from two sources, rainfall on the' plains' andi percolation from such river's as . the Waimakariri. , . Hr. Hi’gandorf has now been working further at the problem on the basis of record’s from various wells at or about Christchurch, and of chemical analyses of waters from- Christchurch, wells andi from their possible sources of supply. His conclusion is that, while the wells are raised above normal level! by a. rainfall, they Are. prevented from falling below normal by percolation from' the Waimakariri. The water analyses are consistent with the thesis that both town end country wells are fed by percolation from the Waimakariri. Now the amount- of water coming through in the neighbourhood of Christchurch is very great, and the combined flow of the wells there is much over 10,000.000 gallons a day. The, idea of such A. vast body of water travelling underground for many miles in Canterbury naturally suggests the possibility •of a, similar phenomenon between Lake Wakntivm and the Iv a wav An bed to account for the large' volume of water which so hampered the miners there on. thp occasion of the recent closing of the

Kawarau dr.lll. The probability of such seepage is a geological problem, and obviously depends very largelly on the nature, of the country through which the water has to pass. The matter was rei'eried to Professor James Park, of Otago University, whose long study of that country enables him to speak with authority. He states definitely that the amount oi' seepage from, the lake to the Kawarau can only be infinitesimal when compared with the total,yolume ofi water in the river bed. The nature bf tlie. deposit through which the water would have to percolate is a very fine silt and limestone, which together are very resistant to water. There is no reason to suppose that the existence of the dam would in any way increase such seepage •*« had previously existed. It does not. seem, therefore, that the analogy of Christchurch and. th e Waimakariri . can afford must support to those, who believe that underground percolation was an important factor in keeping the bed of the Kawarau so ivell filled. , .