An evaluation of a farm irrigation project

The major irrigation schemes operative in, and planned for, Canterbury obtain water from snow fed rivers. These snow fed rivers run to the sea on the high parts of their fans which have coalesced to form the plains. They have their greatest flow in the spring and early summer. As a result, these schemes do not require storage and the water may be run at right angles to the rivers across the plain. The major schemes will cover a little under one million acres, but there is at least another four million acres affected by drought from Central Otago in the south, through North Otago and Canterbury to Marlborough in the north. This four million acres is excluded from the major schemes because it is in the foothills and downs area or contained in small flats which would incur high reticulation costs. Investigations of cost and methods of water supply and its application to this drought prone area have not previously been published in detail, although the use of irrigation to increase pasture growth during the dry summer period has often been considered by individuals and groups of farmers in these districts. A 534 acre property south-east of Waiau in North Canterbury, provided an opportunity for the investigation of methods of water supply and irrigation in this type of drought prone country. In 1968 a research team, consisting of Mr R.D. Plank, Farm Management Department, Lincoln College, Mr T. Heiler, Agricultural Engineering Institute, Lincoln College, and Mr Anthony R. Taylor, Winchmore Irrigation Research Station, Department of Agriculture, was set up to investigate the feasibility of an irrigation scheme based on farm storage dams and automatic watering through border-dykes. It is the results of the work of this team that are published in this bulletin. Section 1 deals with the general principles of border dyke water application and discusses in detail the recommended layout on the project farm. A discussion of the financial impact of the proposed scheme on the farm follows in Section II. Finally, in Section III the hydrologic and hydraulic design of the storage works is laid out in detail, together with the soils investigation summary and the working drawings. The detail in the last section has been included so that non-professional readers may gauge the time and effort required to properly design the type of water storage dams used in this project