SEEPAGE TESTS

Press, Volume LXXXV, Issue 25878, 10 August 1949, Page 6

SEEPAGE TESTS

INQUIRY ABOUT WINCHMORE

GEOLOGIST’S COMMENT

“It is hoped, if equipment is available, to conduct further similar tests at Winchmore next season, and I will' certainly adopt your correspondent’s Suggestion if at all practicable,” said Mr B. W. Collins, Christchurch district geologist of the geological survey of the Department of Scientific find Industrial Research, when commenting on a letter to the editor of "The Press * yesterday. The letter read: Sir, —The geologist’s survey of the irrigation seepage question at Winchmore, as reported in your edition of July 26, makes interesting reading, in view of the large volume of water that accumulated last summer in Nish's pit at Winchmore. Three weeks after the close of the irrigation season this water had receded. Will Mr B. W. Collins kindly comment on this and promise to investigate at this point next irrigation season. —Yours, etc., . INTERESTED.

Mr Collins said he did not know Nish’s pit, but thought it was probably used for the discharge of surplus irrifjation water at rhe lower end of an rrigated paddock. Some of this water Would obviously percolate downwards as indeed it was intended to do. Under ideal management there would be no surplus to get rid of, but at present the practice of irrigation had not progressed far enough to eliminate that need. The tests described in “The Press” of July 26 were conducted partly to determine the optimum amount of water to use under certain conditions, said Mr Collins. They were of a preliminary nature only and much further work needed to be done. “Under the conditions of the test there was no evidence that any water had Percolated below the soil-layer,” Said Mr Collins. “But this statement does certainly not apply to irrigation as practised on a large scale in the Ashburton area. On the other hand it seems clear that at times and in some areas too much v.ater is being used, and some percolates downwards, thus raising the water table. “Nevertheless, there is ample evidence that the effect of such leakage has been quite small in comparison with the effects of the exceedingly high rainfalls experienced in Canterbury between 1935 and 1947,” concluded Mr Collins.