A set of outlet works is a device used to release and regulate water flow from a dam

Dam

A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

. Such devices usually consist of one or more pipes or tunnels through the embankment of the dam, directing water usually under high pressure to the river downstream. These structures are usually used when river flow exceeds the capacity of the power plant or diversion capacity of the dam, but do not have flows high enough to warrant the use of the dam spillway

Spillway

A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically being the river that was dammed. In the UK they may be known as overflow channels. Spillways release floods so that the water does not overtop and damage or even destroy...

s. Although similar in purpose to spillways, outlet works provide a more controlled release to meet downstream flow requirements.
A typical set of outlet works begins in an intake structure, which is usually a canal

Canal

Canals are man-made channels for water. There are two types of canal:#Waterways: navigable transportation canals used for carrying ships and boats shipping goods and conveying people, further subdivided into two kinds:...

 or intake tower. A regulating gate or valve

Valve

A valve is a device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but are usually discussed as a separate category...

 controls water flow into the pipes of the outlet works, which discharge downstream into a stilling basin or directly into the river.
The inlets of the outlet works may consist of either gates or valves, or be composed of a more primitive system of stoplogs

Stoplogs

Stoplogs are a hydraulic engineering control element that are used in floodgates to adjust the water level or flow rate in a river, canal, or reservoir. Stoplogs are sometimes confused with flashboards, as both elements are used in bulkhead or crest gates...

. Inlets may also contain a series of other devices for different purposes, including trashracks and fish screen

Fish screen

A fish screen is designed to prevent fish from swimming or being drawn into an aqueduct, cooling water intake, dam or other diversion on a river, lake or waterway where water is taken for human use. They are built to supply debris-free water without harming aquatic life...

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