Rakaia irrigation

Press, 4 July 1983, Page 20

Rakaia irrigation

Sir,—At the annual general meeting of the New Zealand Salmon Anglers’ Association, the president, Mr K. D. F. Hughey, rejected outright a suggestion that the Rakaia River’s salmon fishery could be preserved if Canterbury were irrigated from groundwater instead of river water. He said: “There is no way Canterbury can be irrigated without using the Rakaia River.” As my understanding of Canterbury irrigation is that groundwater use has increased markedly over the last 10 years, and is likely to increase further in the future, I was puzzled by Mr Hughey’s statement. I was wondering if he could clarify for me and for others who I am sure are wondering, just what his scientific evidence is for rejecting large scale development of irrigation from groundwater.—Yours, etc., BILL HORSLEY, Rangiora June 23, 1983.

[Mr K. F. D. Hughey, president, New Zealand Salmon Anglers’ Association, replies: “Unfortunately Bill Horsley has misquoted and misrepresented the conclusions I presented at the recent annual meeting of the N.Z.S.A.A. I did not say, or intimate, that ground water could not be used for large-scale irrigation development on the central plains. What I did say was that there is no way Canterbury can be completely irrigated without using Rakaia River water. This was put in context by stating that groundwater supplies are only available in amounts suitable to irrigate a portion of the plains. Subsequent over-extraction could then lead to groundwater depletion and associated effects on the internationally regarded wildlife and other values of Lake Ellesmere. In order to restrict this depletion some river water must be applied to replenish groundwater supplies. To support these contentions I refer Bill Horsley to the following quotations from the North Canterbury Catchment Board’s interim report on the groundwater resource of the central plains. Page 88 of the report states that ‘it is estimated that the present irrigation usage of 11 cumecs irrigating 34,500 ha during the irrigation season could be doubled without presenting problems.’ The report then concludes, on page 101, that ‘to increase abstraction from the ground water without depleting the resource requires that there be compensatory recharge (surpluses) from irrigation development utilising a “foreign” source of water.’ When it is considered that the total irrigable area is in excess of 200,000 ha, it is clear the use of river water in some form is essential. To this extent the N.Z.S.A.A. has now commissioned a firm of consulting engineers to assess an environ-

mentally acceptable option for implementing this plan.”]