What is a weir?

Question

I never knew weirs existed till now. How does it differ from a dam and why do people use/bulid it or rather what is a purpose of the weir?

Thanks

Answer 1

C'mon people.  There are so many resources available on the net.  Do some research yourself.  http://en.wikipedia.org/wiki/Weir

Answer 2

A weir (IPA: /wɪɚ/) (also known as a lowhead dam) is a small overflow-type dam commonly used to raise the level of a river or stream. Weirs have traditionally been used to create mill ponds in such places. Water flows over the top of a weir, although some weirs have sluice gates which release water at a level below the top of the weir. The crest of an overflow spillway on a large dam is often called a weir.

Weirs are used in conjunction with locks to render a river navigable and to provide even flow for navigation. In this case, the weir is made significantly longer than the width of the river by forming it in a 'U' shape or running it diagonally instead of the short perpendicular path. Since the weir is the portion where water is overflowing, a long weir allows a lot more water with a small increase in overflow depth. This is done in order to minimize fluctuation in the depth of the river upstream with changes in the flow rate of the river. Doing so avoids unnecessary complication in designing and using the lock or irrigation diversion devices. [1]

Weirs also give hydrologists and engineers a simple method of measuring the rate of fluid flow in small to medium sized streams or in industrial discharge locations. Since the geometry of the top of the weir is known, and all water flows over the weir, the depth of water behind the weir can be converted to a rate of flow. If water is not carried away from the weir, it can complicate or make flow measurement impossible.

Answer 3

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Geography Dictionary: weir

Generally speaking, a small dam built across a river. In hydrology, weirs are erected to measure river flow. Water is impounded behind the dam and is fed through a notch. Sharp-crested weirs have a sharpened metal plate to dam the stream and a steep-sided notch. Broad-crested weirs are wider and lower. The rate of discharge of the river is calculated by different methods at each type of weir.



WordNet: weir

Note: click on a word meaning below to see its connections and related words.

The noun has 2 meanings:

Meaning #1: a low dam built across a stream to raise its level or divert its flow

Meaning #2: a fence or wattle built across a stream to catch or retain fish



Wikipedia: weir

The bridge and weir mechanism at Sturminster Newton on the River Stour, Dorset.

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The bridge and weir mechanism at Sturminster Newton on the River Stour, Dorset.