- § = a) primary benefits of irrigation and drainage projects should -be baged on the expected increased net present value of agricultural production once marketing aspects have been investigated. Where appropriate, price and yield sensitivity analysis should be conducted; b) discount rate ~ the discount rate for present value calculations shail be 10% with sensitivity analysis conducted at 8% and 12%, of as determined by Management. Committees c} @ project Life for present value calculations of 25 years; é) total costs should include capital works, material and labour costs as well as maintenance and operational costs of the works: @) secondary benefits and costs should be examined where they can be clearly defined and considered in the analysis. 85/10/68