Forebay (reservoir)

A pre-dam is usually a smaller dam, which is facing a dam to hold back is carried by the tributaries of contaminants ( tree trunks, oil, debris, sediment), which is particularly important in systems for domestic water supply is important.

Definition

Pre Perren and forebay

From the word meaning here is a " pre-dam " is a locking structure as the main barrier, behind which the " forebay " is. Pre-dam and forebay are thus one and designate two parts of the same dam. It would be immaterial whether there is still a piece of river between them and the main lock.

Definition of DIN

However, the DIN 4048-1:1987-01 ( stand 10.2005 ) makes another attempt, the terms pre-dam and forebay to standards. As a pilot Perren will be referred to, which are directly on the storage root of a dam, where the river or stream flows into the dam according to DIN dams. Forebay are of the main and pilot Perren upriver farther away. A pre-dam located just outside the main basin and is separated by a shut-off ( dam dam ) from her, and this is also backed up on the air side. The storage levels in the pre-dam is higher than or the same as in the main basin. A forebay is located further up the main barrier (or the pre-dam ) with a piece of river between.

Earlier meanings

In the past, the terms are often - too inconsistent used - in addition to the above definition. Large forebay, even if they were away from the main lock and already had the size of a dam, were sometimes called " pre-dam ". Insignificant small pilot Perren, however, were referred to as " forebay " or impoundments. They sometimes have only a passage without accumulation.

More definitions

Named in DIN difference should be better defined with other terms, such as:

Purpose of pre- Perren

Pre Perren and forebay are built to keep debris like, floating debris, dirt and from the main pool. The water should be pre-cleaned, thereby settle any suspended matter. For optimum precleaning of the water a sufficient residence time in the forebay is required; Short-circuit currents in the main basin are directly should be avoided. The required size of a Vorbeckens can be calculated depending on the amount of inflow, usually the sizing but is more influenced by structural conditions.

Depending on the conditions in the catchment forebay can silt by sedimentation and must be dredged periodically. Through them, but prevents the main reservoir silted up.

Pre Perren left on continuously accumulates, while the main barrier may have at all times changing water level. Due to the constant water level in the forebay is very different ecological conditions for the animal and plant world, making the forebay often develop into habitats that are put under protection arise.

Underwater pilot Perren

Pre Perren, which are at full back in the main reservoir under water, also called underwater pre Perren.

• Dam type