Accuracy of Irrigation Efficiency Estimates

Evaluation of actual irrigation system perfonnance should rely on an accurate hydrologic water balance over the area considered. In a companion paper, water uses are categorized as consumptive or noncon­ sumptive, and beneficial or nonbeneficial. Real perfonnance 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 perfonnance parameters can be determined from the accuracy of the components in the water balance, using standard statistical procedures. Accuracy is expressed in tenns of confidence intervals. Equations, procedures, and examples are provided for making these calculations. It is recommended that con­ fidence intervals be included in all reporting of irrigation system perfonnance parameters.