On-farm irrigation efficiencies - are they what we believe and what are the implications beyond the farm gate?

Ten on-farm centre pivot irrigation efficiency evaluations were undertaken using the catch can tests. 70% of the pivots had lower than expected uniformities. The average coefficient of uniformity (CU) and distribution uniformity (DU) were 79% and 68% respectively. Issues affecting efficiency results can be remedied through minor changes to the irrigation systems or operational changes to achieve acceptable average CU and DU values of at least 85% and 75% respectively. For example, the measured pressures on 80% of the pivots were below the optimal design pressures. Dealing with some obvious leaks on 25% of the irrigators could improve performance significantly. The paper further analyses the implications of the low efficiencies at farm level and beyond the farm gate level with respect to water allocation and energy use when (i) the systems are left unchanged to operate at low efficiency levels and (ii) when performance improvements are undertaken to achieve acceptable CUs and DUs. The paper demonstrates that even marginal improvements can have a substantial improvement on water use with up to 46% more water becoming available for other users or expanded irrigation depending on consented allocation and the rainfall season. This paper concludes by illustrating that this aspect of water management could, with further policy attention.