Flow rate measurement in gravity irrigation systems using sluice gates

Abstract

Gates are used to divert water to rice production plots in eastern Uruguay. In this study, the operating curves of rectangular gates installed at the entrance of circular section pipes are determined for submerged discharge conditions, which can be also used as gauging structures. For the tests, the gates were mounted at the inlet end of 6-m-long,sanitary-type PVC pipes, and with a nominal diameter of 250 and 315 mm. This configuration is analogous to that used in gravity irrigation systems. The derivation of the operating equations of the gates in this configuration is presented. The discharge coefficients (Cd) experimentally obtained show that discharge under the gate is dependent on the opening and on the upstream and downstreamdifference in depth, in addition to the Reynolds number under the gate. The dependence on the Reynolds number, which is usually omitted in other applications, is relevant in the case of rice irrigation, given the low velocities, and allows its use as a regulation structure and water gauging in these systems.