An economic evaluation of irrigation methods at Bundaberg

This paper reports the economic aspects of an extensive evalriation of four irrigation methods on soils of different water-holding capacities and at three water allocation rates for a 50 ha farm at Bundaberg and $330/tonne sugar. Water balance modelling determined crop yield and other base data. Engineering designs for each irrigation system determined capital and operating costs, and an economic model calculated gross benefit-cost ratios. For greenfield development,furrow with tailwater return was superior to other irrigation methods on soils with high moisture holding capacity, while drip was superior on low to medium moisture holding soils, despite the high capital cost of drip. Increasing the quantity of irrigation water from 50% to 100% allocation increased benefit-cost ratios markedly, highlighting the need for more water storage in the Bundaberg district. Benefit:cost ratios after conversion of 100% of the farm to furrow with tailwater return or drip irrigation remained essentially unchanged at 50% allocation, improved markedly at 100% allocation, but reduced with unlimited water supply, indicating conversion was most profitable with mediocre water supplies.