Spillway of Llyn Brianne dam in Wales

A Spillway is a structure used to provide for the controlled release of flood flows from a dam or levee into a downstream area, typically being the river that has been dammed. Floods are released by spillways so that the water does not overtop and damage, or even destroy, the dam by overflowing the structure. Except during flood periods, water does not normally flow over a spillway. In contrast, an "intake" is a structure used to release water on a regular basis for water supply, hydropower production, etc. Download high resolution version (966x1404, 431 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (966x1404, 431 KB) Wikipedia does not have an article with this exact name. ... National motto: Cymru am byth (Welsh: Wales for ever) Waless location within the UK Official languages English, Welsh Capital Cardiff Largest city Cardiff First Minister Rhodri Morgan Area  - Total Ranked 3rd UK 20,779 km² Population  - Total (2001)  - Density Ranked 3rd UK 2,903,085 140/km² Ethnicity: 97. ... Scrivener Dam, Canberra Australia, was engineered to withstand a once-in-5000-years flood event A dam is a barrier across flowing water that obstructs, directs or retards the flow, often creating a reservoir, lake or impoundment. ... A levee, levée (from the feminine past participle of the French verb lever, to raise), floodbank or stopbank is a natural or artificial embankment or dike, usually earthen, which parallels the course of a river. ...

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 rely entirely on bottom outlets and lack an overflow spillway.

There are two types of spillways: uncontrolled and controlled.

Spillway gates control the level of Lake Difenbaker, Saskatchewan Canada

Uncontrolled spillways do not have gates; when the water rises above the lip or "crest" of the spillway it begins to be released from the reservoir. The rate of discharge is controlled only by the depth of water within the reservoir. All of the storage volume in the reservoir above the spillway crest can be used only for the temporary storage of floodwater, and cannot be used as water supply storage because it is normally empty. Image File history File links Radial-type spillway gates for the Gardiner Dam on the Saskatchwan River, near Elbow, Saskatchwan Canada. ... Image File history File links Radial-type spillway gates for the Gardiner Dam on the Saskatchwan River, near Elbow, Saskatchwan Canada. ... Motto: Multis E Gentibus Vires (From many peoples, strength) Other Canadian provinces and territories Capital Regina Largest city Saskatoon Lieutenant Governor Lynda M. Haverstock Premier Lorne Calvert (NDP) Area 651,036 km² (7th) Land 591,670 km² Water 59,366 km² (9. ...

A controlled spillway has mechanical structures or "gates" to regulate the rate of flow. This design allows nearly the full height of the dam to be used for water storage year-around, and flood waters can be released as required by opening one or more gates.

Bell-mouth spillway at Llyn Celyn

Ice breaker rim on bell-mouth spillway

Some spillways are designed like an inverted bell-mouth so that water can enter all around the perimeter (also termed a "morning-glory" design). In areas where the surface of the reservoir may freeze, bell-mouth spillways are normally fitted with some arrangements for breaking the ice to prevent the spillway from becoming ice-bound. Image File history File links Download high resolution version (2250x1530, 2717 KB) Description: Llyn Celyn bell-mouth spillway Source: photo taken by Velela Date: August 14, 2005 Author: Velela Permission: Velela released under CC-BY-SA-2. ... Image File history File links Download high resolution version (2250x1530, 2717 KB) Description: Llyn Celyn bell-mouth spillway Source: photo taken by Velela Date: August 14, 2005 Author: Velela Permission: Velela released under CC-BY-SA-2. ... Llyn Celyn is a large reservoir constructed in 1961 in the valley of the River Tryweryn. ... Image File history File links Download high resolution version (1296x972, 798 KB) Description: Llyn Celyn bell-mouth spillway showing ice-breaker rim Source: photo taken by Velela Date: August 14, 2005 Author: Velela Permission: Velela released under CC-BY-SA-2. ... Image File history File links Download high resolution version (1296x972, 798 KB) Description: Llyn Celyn bell-mouth spillway showing ice-breaker rim Source: photo taken by Velela Date: August 14, 2005 Author: Velela Permission: Velela released under CC-BY-SA-2. ...