Abstract: A water control gate assembly comprises a self-actuating top-hung gate for controlling the flow of water in a waterway. The gate is pivotably mounted on a pair of piers located above an upstream of the gate for allowing the gate to pivot between a closed position and an open position in which water flows beneath the gate. The gate includes a ballast tank having an upstream inlet for charging the ballast tank and a downstream outlet for discharging the ballast tank. The upstream inlet is arranged to start charging the ballast tank with water in the event of the upstream water level reaching a first lower level. The downstream outlet is arranged to start discharging the ballast tank in the event of the upstream water level reaching a second upper level, with the ingress of water into the ballast tank between the first and second levels progressively increasing the closing moment of the gate and maintaining it closed against the progressively increasing opening moment of upstream water pressure against the gate.