Spillway

A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure that the water does not overflow and damage or destroy the dam. Lake Berryessa overflowing into the Glory Hole spillway at Monticello dam.A labyrinth spillway and a fish ladder (left) of the Hope Mills Dam in North Carolina.Spillway with flip bucket at Burdekin Dam.Water enters Hoover Dam's Arizona side channel drum-gate spillway (left) during the 1983 floods.A labyrinth spillway entrance (bottom) at the Ute Dam in New Mexico.An ogee-type spillway at the Crystal Dam in Colorado.An emergency spillway with fuse plug (bottom) and an auxiliary ogee spillway (top) at New Waddell Dam.Semicircular spillways of Ohzuchi Dam (Shiga Pref., Japan)Looking down into the Bell mouth spillway at Llyn CelynLow-height spillway of Bonneville Dam with sluice gatesA drop inlet in use at Horse Mesa Dam in Arizona, circa 1940The spillway at Monticello Dam, Lake Berryessa, in operation. February 19, 2017.The Geehi Dam spillway has never seen water as of March 2019. A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure that the water does not overflow and damage or destroy the dam. Floodgates and fuse plugs may be designed into spillways to regulate water flow and reservoir level. Such a spillway can be used to regulate downstream flows – by releasing water in small amounts before the reservoir is full, operators can prevent sudden large releases that would happen if the dam were overtopped. Other uses of the term 'spillway' include bypasses of dams or outlets of channels used during high water, and outlet channels carved through natural dams such as moraines. Water normally flows over a spillway only during flood periods – when the reservoir cannot hold the excess of water entering the reservoir over the amount used. In contrast, an intake tower is a structure used to release water on a regular basis for water supply, hydroelectricity generation, etc. A spillway is located at the top of the reservoir pool. Dams may also have bottom outlets with valves or gates which may be operated to release flood flow, and a few dams lack overflow spillways and rely entirely on bottom outlets.