Overflow structure of a dam Water passed over a spillway, or spill, can be forced, when there is not enough storage capability and flows exceed turbine capacity, or planned, when water is spilled to enhance juvenile fish passage
A passage such as a paved apron or channel for surplus water over or around a dam or similar obstruction An open or closed channel, or both, used to convey excess water from a reservoir It may contain gates, either manually or automatically controlled, to regulate the discharge of excess water
The channel or passageway around or over a dam through which excess water is released without going through the turbines It is a safety valve for a dam and must be capable of discharging major floods without damaging the dam while maintaining the reservoir level below some predetermined maximum level
A structure over or through which excess or flood flows are discharged If the flow is controlled by gates, it is a controlled spillway, if the elevation of the spillway crest is the only control, it is an uncontrolled spillway