Accuracy of irrigation efficiency estimates

Evaluation of actual irrigation system performance should rely on an accurate hydrologic water balance over the area considered. In a companion paper, water uses are categorized as consumptive or nonconsumptive, and beneficial or nonbeneficial. Real performance is based on water uses over a specified period of time, rather than observation of a single irrigation event (with associate potential, but not yet actual, consumptive and/or beneficial uses). Once the components in the water balance have been determined, it is shown that the accuracy of irrigation performance parameters can be determined from the accuracy of the components in the water balance, using standard statistical procedures. Accuracy is expressed in terms of confidence intervals. Equations, procedures, and examples are provided for making these calculations. It is recommended that confidence intervals be included in all reporting of irrigation system performance parameters.