MACKENZIE COUNTRY’S FUTURE FARM WATER NEEDS

Press, Volume CIII, Issue 30534, 1 September 1964, Page 20

MACKENZIE COUNTRY’S FUTURE FARM WATER NEEDS

When the inter-departmental committee which is examining the future use of water resources in the Mackenzie Country visited the district recently, discussions were held with runholders and representatives of interested organisations about stock and irrigation water supplies after the possible diversion of water from the Tekapo river into the Maryburn canal, which will carry water overland to a power station in the Maryburn valley and then to Lake Pukaki.

According to a report of the discussions provided by the chairman of the committee, Mr D. B. Dallas, Mr G. Natusch, of the Ministry of Works, told the meeting that as yet the Maryburn canal scheme had been approved only in principle by the Government. Design proposals would aim at a minimum of disturbance of the farming community. He indicated that it would be wasteful to leave a boundary flow in the Tekapo river and so when when the river was diverted it would not only be necessary for flood channels to be maintained, but also both' sides of the riverbed would have to be fenced to provide an alternative boundary. Stock Water Where the erection of boundary fencing resulted in high grade river flats being cut off, it was agreed that it would be reasonable for adjoining owners to graze these areas provided that

they assumed the responsibility for maintaining their own boundaries. Schemes for provision of stock water should power interests require all the water from the Tekapo were described by Mr E. R. L. O’Toole, of the Ministry of Works. He said that it would be possible by a system of races to provide stock water from the Sawdon and Edwards streams on the east side of the river; from the Forks, Irishman and Maryburn streams on the west side: and from the Maryburn canal for the area to the south-west of the Mary range. It was envisaged that in no case would stock be more than half a mile from water so that the system went well beyond the obligations of providing compensation water. Mr O’Toole also described the alternative of a piped supply. While there were reticulation problems arising from freezing conditions these could be overcome. Mr O’Toole concluded his survey by outlining a race system for providing water for irrigation from tributary streams to an area of 15,000 acres on the east bank of the Tekapo and an area of 30,000 to 40,000 acres on the west bank. Any water for irrigation in the area of about 5000 acres to the south-west of Simons Pass would have to be obtained by pumping from Lake Pukaki or from the. power canal, it was pointed out.

With only two or three exceptions those present at the meeting did not appear to have any Ann views on whether a race or piped system was

preferred, but it was pointed out that the Government might prefer a water supply involving pumping, storing and piping on the score of economy. Experience had also shown that frost damage to existing races was extensive and ice banking caused by fence or tree obstructions resulted in an overflow. The meeting was told that a major problem involved the passing of up to about 4000 cusecs of flood water either over or under the Maryburn canal, and while it was reported that various measures w'ere being planned to deal with this situation, including diverting the Forks stream into Lake Tekapo by the Joseph and Cass streams, nothing had yet been decided Some fears were expressed at the meeting about the adequacy of the protective structures in the Cass stream to handle this. Irrigation Of water needs for irrigation, Mr D. G. Reynolds, farm advisory officer of the Depart ment of Agriculture, Fairlic, and a member of the committee, said it was most unlikely that more than 50,000 acres would receive attention in the foreseeable future. The more immediate need was for limited irrigation to provide winter feed on 100 acres per 3000 sheep and this could be provided from stock water races Mr Dallas said later that more thought would need to be given to the relative merits of a piped as compared with a race water supply and at the same time consideration would have to be given to the provision of sufficient water to produce winter feed for sheep during the optimum growing period of 100 days in the Pukaki, Irishman creek and Edwards creek areas. A check was also being made on the likely areas that would be responsive to irrigation, he said, and arrangements had been made with superintendent of the Winchmore irrigation research station, Mr W. R. Lobb, for determination of soil infiltration rates in potential irrigation areas. Mr Dallas said that more investigations were also needed into the flow capacities of tributary streams.