Author
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Clemmens, Albert |
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Submitted to: International Conference on Water Resources Engineering Proceedings
Publication Type: Proceedings Publication Acceptance Date: 8/18/1995 Publication Date: N/A Citation: N/A Interpretive Summary: Competition for limited water supplies has escalated substantially over the last decade. Unfortunately there are many misconceptions about water use, particularly in irrigated agriculture. The potential water savings that might result from increases in irrigation efficiency are usually overestimated. Many of these misconceptions and erroneous estimates of water savings stem from misunderstandings about how irrigation performance measures are defined and used. An ASCE task committee was formed to help to clarify the definition of irrigation performance measures -- what they represent and what has to be measured in order to provide reasonable values. Unfortunately, field measurements of irrigation performance contain errors, regardless of the skill of the evaluator. In this paper, we provide mathematical equations for calculating the possible error in irrigation performance estimates based on the errors associated with each measurement. Examples are provided which demonstrate that the confidence intervals for irrigation performance parameters are fairly wide, regardless of how much effort goes into field measurements. The results of this work will benefit irrigation district personnel, support and regulatory agencies, consultants, farmers, and other water users. Technical Abstract: Equations are presented for determining the confidence intervals (CI) of irrigation performance measures such as Irrigation Efficiency (IE) and Distribution Uniformity (DU), based on the accuracy of individual measurements. Also, an approximate equation for the confidence interval of DU is given, when it is estimated from the uniformity of components (i.e., to obtain a global DU). Examples are given which show the relatively wide CI for typical irrigation performance assessments. |
