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Title: ACCURACY OF FLOW MEASUREMENTS IN THE IMPERIAL IRRIGATION DISTRICT

Author
item Wahlin, Brian
item Replogle, John
item Clemmens, Albert

Submitted to: Congress of International Association for Hydraulic Research Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/15/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: The effectiveness of water conservation programs is limited by many physical and economical constraints. The Imperial Irrigation District (IID) has an interest in water conservation measures. The district is located at the tail end of the Colorado River, where unconsumed water flows to the Salton Sea. While some significant water conservation efforts have taken place, the volume of water flowing to the Sea is still on the order of one million acre feet per year. To determine the overall effectiveness of IID's water conservation programs and to identify opportunities for improving water management practices within the district, the accuracy of the measurements of the amount of water flowing into and out of IID needed to be evaluated. Five key sites entering and exiting the district were identified. The results of this study indicate that 4 of the 5 sites had individual flow measurement accuracies of about 3% while the fifth site had dan accuracy of about 6.5%. Because of the large number of measurements made in a year's time, the random errors of these individual measurements canceled in accordance with statistical theories. The result was that annual estimations of the volume flowing into and out of IID could be determined to within about 2 to 3%. Using this information, effects of various water conservation efforts within IID can be evaluated and additional water conservation practices may be identified. Irrigation districts interested in water conservation would benefit from the results of this research.

Technical Abstract: The Imperial Irrigation District (IID) in southern California has an interest in water conservation programs. These measures depend on the quantification of water flows at various sites within the district. In this study, the random and systematic error components for individual flow measurements at five key sites into and exiting IID were determined. From these individual error components, an estimate of the uncertainty for the annual volume that passes through these sites was determined. This information is expected to be used to identify opportunities for improving water management practices within the district. The 95% confidence interval for the annual volume at 4 of the 5 study sites was plus or minus 2.25%. The fifth site had a 95% confidence interval for the annual volume of plus or minus 3.50%. IID does a good job of estimating the flow rate and volume at each of these five sites. Very little systematic error (bias) could be identified and most of the random error is compensated because of the large number of current meterings IID performs each year.