|Wahl, Tony - BOR, DENVER, CO|
Submitted to: United States Committee of Irrigation and Drainage Engineering Conference
Publication Type: Proceedings
Publication Acceptance Date: March 1, 2003
Publication Date: July 13, 2003
Citation: Wahl, T.L., Clemmens, A.J., Replogle, J.A. The energy correction for calibration of submerged radial gates. United States Committee of Irrigation and Drainage Engineering Conference. p. 757-766. Interpretive Summary: Water supplies in the Western United States are not sufficient to meet current water demands, especially when considering water needed for environmental purposes. Agriculture=s share of available water is likely to decrease in the future. Agricultural water purveyors are being pressed by other water users to improve water measurement, control, and accounting, while their water users are demanding more flexible water deliveries so they can compete in the marketplace and implement water conservation measures on farm. Operation of irrigation-water delivery systems can be improved by providing canal operators with better tools for measuring flow rates. Radial gates are commonly used to control and measure flow rates within irrigation canals. Unfortunately, calibration of these gates has been problematic, particularly when the downstream water level is high (that is, the gate is submerged on the downstream side). A new calibration procedure for radial gates has been developed for both free-flow conditions (that is, when the downstream water level does not submerge the gate) and when the downstream level causes gate submergence. This paper provides an evaluation of these procedures based on prior data collected by the Bureau of Reclamation. These results should be of use to irrigation districts, consultants, and the U.S. Bureau of Reclamation. Ultimately better management of irrigation water supplies will conserve water and benefit the environment.
Technical Abstract: The E-M (energy-momentum) method is a new technique for calibrating radial gates, using the energy equation on the upstream side of the vena contracta and the momentum equation downstream from the vena contracta when the gate is submerged. This method allows continuous calibration from free to submerged flow through the transition zone, and overcomes several limitations of energy-based submerged flow equations since it explicitly accounts for downstream channel conditions. A key parameter in the method is an energy correction factor for submerged flow. This paper uses a previously collected data set to demonstrate the dependence of the energy correction on the relative gate opening and to develop an improved model for predicting the energy correction.