Submitted to: Journal of Hydraulic Engineering
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/17/2003
Publication Date: 6/1/2003
Citation: Clemmens, A.J., Strelkoff, T., Replogle, J.A. 2003. Calibration of submerged radial gates. Journal of Hydraulic Engineering. 129(9):680-687. 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 irigation-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 (when the downstream water level does not submerge the gate) and when the downstream level causes gate submergence. 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: Calibration equations for free-flowing radial gates typically provide sufficient accuracy for irrigation district operations. However, many districts have difficulty in determining accurate discharges when the downstream water level begins to submerge the gate. Based on laboratory studies, we have developed a new calibration method for free-flowing and submerged radial gates that allows for multiple gates and widely varying upstream and downstream channel conditions. The method uses the energy equation on the upstream side of the structure and the momentum equation on the downstream side, and thus is called the Energy-Momentum (E-M) Method. An iterative solution is required to solve these two equations, but this allows calibration from free flow to submerged flow right through the transition. Adjustments to the energy equation for free flow are described, along with an additional energy adjustment for the transition to submerged flow. An application is used to describe the new procedure and how it overcomes the limitations of current energy-based methods.