Weir

A weir (also dam, dam, in Switzerland, Austria and Southern Germany Wuhr or Werche ) is a hydraulic dam, which closes off the inflow or outflow of a water body. Weirs can temporarily flows over or through flows (or both simultaneously) be. They are generally along with other facilities constructed and operated (eg hydropower plant, lock, dam ).

The area below the weir is an underwater, the above referred to as the upper hand. The over falling water falls behind the weir in a stilling basin. The stilling basin can be completed by a threshold that is used to stabilize the exchange jump. About large fixed fortifications sometimes river bridges to be built. A smaller design of the weir is the manipulated case.

History

The first weirs there were already 5,000 years ago. Early weirs were created as permanent fixtures in the river, and were then usually the supply of water for the operation of a mill or the introduction into a channel other purpose ( water supply, irrigation). Weirs were able to navigable waters with low depth, presented on the other hand especially for large ships significant barriers dar.

Use

Weirs can serve different purposes (often several purposes simultaneously):

• Supply one above the weir branching channel for the operation of navigation or for irrigation agriculture
• Navigability of the upper water ( then usually in combination with a lock, which allows the bypass of the weir )
• Energy production ( mill, hydroelectric power plant, the power plant may be due to a secondary channel or directly into the barrage: River power plant, hydroelectric power plant)
• On the flow dynamics in a river system: Regulierwehr (example: Regulierwehr port)
• Stabilization of the sole of the watercourse (support weir)
• Provision of domestic hot water for industry
• Provision of drinking water
• Provision for fire fighting water reserves
• Flow measurement of a stream by means of a weir plate
• Creation of retention volume and surge rinses in storage channels in the form of cascade weirs
• Control of waste streams and discharges of mixed water in the water sector with the help of discharge weirs
• Fishing in the fish weir

As storage aim of the prescribed water level is referred to in the headwater, which is sought in accordance with the intended purpose of the weir for control operation and must not be exceeded with regard to lying on the upper reaches of the watercourse water users. Short-term exceedances are at high water, in exceptional situations, not always be avoided. The highest water level represents the maximum water level in the design flood outflow represents the water level is determined using a level.

Weir

Measuring weirs are used for measuring the flow of a stream by means of a weir plate

• Thomson weir ( V-notch weir )
• Plate weir
• Rectangular weir
• Cipolettiwehr

Designs

Fixed weirs

Armed with bluff body without closure

Basic military (wide crest weir)

Spillway

Siphon weir

Movable weirs

For movable weirs can be necessary, the shutters partly or completely eliminate them.

Cascade weir

Movable weirs with locks überströmbaren

Fish-belly flap

Roof weir ( double flap weir, bear trap )

Drum weir

Defense sector

Inflatable weir

Movable weirs with locks unterströmbaren

Segment weir

Roll defense

Restrictor bar weir

Float controlled flap weir

ASK weir - weir segment

Components

Today weirs usually contain at least partially movable elements (called relays) with which a dynamic flow regulation is possible. Modern dams also often include a fish pass, a weir, a boat or even a fish passage Canoe Pass.