In this study the author has used cost-benefit analysis to determine the net benefits, at both national and private levels, of the Waiau Section of the Amuri Plains Irrigation Scheme in North Canterbury. The effects on private returns of changes in the level of government subsidisation of irrigation development have also been analysed within this framework. The A.E.R.U. has continuing interest in irrigation. Other papers concerned with this subject include A.E.R.U. Research Reports No. 99 (The Regional Impacts of Irrigation Development in the Lower Waitaki)and No. 135 (Water and Choice in Canterbury).