# What is a concrete weir?

## What is a concrete weir?

A weir is a concrete or masonry structure which is constructed across the open channel (such as a river) to change its water flow characteristics. Weirs are constructed as an obstruction to flow of water. These are commonly used to measure the volumetric rate of water flow, prevent flooding and make rivers navigable.

## How do you create a weir?

Criteria for Proper Weir Design

1. The weir should consist of a thin plate 1/8 to 1/4 inch (3 to 6 mm) thick with a straight edge or a thicker plate with downstream chamfered edge.
2. The upstream face of the weir should be smooth and perpendicular to the axis of the channel in both horizontal and vertical directions.

What is the main purpose of a weir?

A weir is a small dam built across a body of water, such as a river. We use them to help control the flow of water. Weirs can help raise the water level so that boats can pass through, and they can also reduce the flow of water to prevent flooding.

How do you calculate flow through a weir?

The equation recommended by the Bureau of Reclamation in their Water Measurement Manual, for use with a suppressed rectangular weir is: Q = 3.33 B H3/2, where Q is the water flow rate in ft3/sec, B is the length of the weir (and the channel width) in ft, and H is the head over the weir in ft.

### What is a standard weir?

Standard Contracted Rectangular Weirs. The fully contracted rectangular weir (figure 7-1) is the most frequent standard weir used in irrigation. To be fully contracted, all overflow plate sides and ends must be located at least a distance of 2h1max (two maximum measurement heads) from the approach flow boundaries.

### How do weirs measure flow?

Weirs to Measure Flow It works by raising the water level upstream of the weir, and then forcing the water to spill over. The more water is flowing over the weir, the deeper the water will be upstream of the weir. So measuring flow rate (CFS) can be done by simply measuring the depth of the water upstream.

Why do we build weirs?