Glenmark Irrigation Scheme : Final design

Abstract

This report is a detailed case study of a community irrigation scheme which involves new concepts for New Zealand. These concepts could apply over a much wider range of conditions (topography, soils, water supply ,etc) than the existing, traditional schemes operating in Otago and Canterbury. As such, it opens the way for new developments in grazing and farming practice which may be far reaching. The agricultural and economic problems that exist on the farms within the area of this proposed scheme are common to many places in New Zealand. Farms are small; the farming systems involve a high proportion of cash cropping to complement traditional fat lamb production; and the area is subject to regular and severe droughts from October to March. Many of the farms are uneconomic at present. Unless a way for improving productivity and profitability can be found, large scale farm amalgamation may become inevitable. The summer water resources of the area are not sufficient to supply sufficient water for traditional run-of-river diversion irrigation schemes .The total water resources, however, are considerable, but flood discharge accounts for most of the annual discharge. The concept that is examined in detail in this report is that the diversion of flood water from tributaries of the Waipara River, into 28 storages constructed on 20 farms within the scheme area, will be used during periods of low rainfall to provide supplemental irrigation. Because many of the hydrologic, engineering and economic problems involved in this scheme have not been investigated in New Zealand before,the experience gained has, potentially, a wide application. This report is a record of this experience, as well as an answer to the particular problems of the Glenmark irrigation proposals.