GATE

(1) (Irrigation) Structure or device for controlling the rate of water flow into or from a canal, ditch, or pipe. (2) (Dam) A device in which a leaf or member is moved across the waterway from an external position to control or stop the flow. The following types of gates apply to dams and other such structures: (1) Bulkhead Gate: A gate used either for temporary closure of a channel or conduit to empty it for inspection or maintenance or for closure against flowing water when the head differential is small, e.g., a diversion tunnel closure. Although a bulkhead gate is usually opened and closed under nearly balanced pressures, it nevertheless may be capable of withstanding a high pressure differential when in the closed position. (2) Crest Gate (Spillway Gate): A gate on the crest of a spillway to control overflow or reservoir water level. (3) Emergency Gate: A standby or reserve gate used only when the normal means of water control is not available. (4) Fixed Wheel Gate (Fixed Roller Gate, Fixed Axle Gate): A gate having wheels or rollers mounted on the end posts of the gate. The wheels bear against rails fixed in side grooves or gate guides. (5) Flap Gate: A gate hinged along one edge usually either the top or bottom edge. Examples of bottom-hinged flap gates are tilting gates and fish belly gates, so-called due to their shape in cross section. (6) Flood Gate: A gate to control flood release from a reservoir. (7) Guard Gate (Guard Valve): A gate or valve that operates fully open or closed. It may function as a secondary device for shutting off the flow of water in case the primary closure device becomes inoperable, but is usually operated under balanced pressure, no-flow conditions. (8) Outlet Gate: A gate controlling the outflow of water from a reservoir. (9) Radial Gate (Tainter Gate): A gate with a curved upstream plate and radial arms hinged to piers or other supporting structures. (10) Regulating Gate (Regulating Valve): A gate or valve that operates under full pressure and flow conditions to throttle and vary the rate of discharge. (11) Slide Gate (Sluice Gate): A gate that can be opened or closed by sliding it in supporting guides.