an irrigation channel gate uses flexible members which once released use the power of water flow to open and shut the gate . when flow in the channel is desired both an upstream gate and downstream gate are open . to stop flow the upstream gate is released . to reset the gates the down stream gate is closed and the upstream gate is opened . opening of the downstream gate permits flow again . the gates essentially comprise a main member hinged on a horizontal axis at the base of the channel and flexible side pieces to connect the main member to a central frame .