Table of Contents

## What are the units for the weir coefficient?

The weir coefficient, since it is a function of the gravitational constant, is not dimensionless and therefore has different values depending on which unit system you are using. For example, a weir coefficient (C) of 3.00 in English Units would be 1.66 in SI units.

## How discharge is measured using a weir?

A weir, as defined in the USBR measurement manual, is simply an overflow structure built perpendicular to an open channel axis to measure the rate of flow of water. In other words, a weir is essentially a partial dam. It works by raising the water level upstream of the weir, and then forcing the water to spill over.

## What is 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 is weir calculated?

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’s the purpose of a weir?

Weirs are fixed barriers across a river or stream that force water to flow over their tops, where the height of the water above the weir can be used to calculate flow.

## How does a rectangular weir work?

A sharp crested, rectangular weir is simply a flat plate obstruction in an open channel flow path, with a straight, level opening to allow water flow over the weir, as shown in the pictures and diagrams in the rest of this article.

## What is the importance of weir?

Commonly, weirs are used to prevent flooding, measure water discharge, and help render rivers more navigable by boat. In some locations, the terms dam and weir are synonymous, but normally there is a clear distinction made between the structures.

## What are some disadvantages of a weir?

Disadvantages of Weirs

- Spacious Upstream Weir Pool Required.
- Cold Weather Can Compromise Readings.
- Discharge Must Be Free-Spilling.
- Weir Maintenance Is Extensive.
- Weirs and Flumes From Tracom.