Broad Crested Weir Calculator

A broad-crested weir is a control structure commonly used in hydraulic engineering to measure flow rates in open channels, like streams and irrigation ditches. This tutorial provides an overview of the principles behind broad-crested weirs, the formulas for calculating flow over a broad-crested weir, its real-life applications, notable individuals, and some interesting facts related to this fundamental hydraulic engineering structure.

Broad Crested Weir Calculator
Broad Crested Weir Calculator Results
Water Flow Rate = m3/s

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The formula for flow rate over a broad-crested weir is:

Q = Cd L H3/2


  1. Q: The flow rate (in cubic meters per second).
  2. Cd: The discharge coefficient, which is dimensionless and accounts for energy losses as the water flows over the weir. It must be determined experimentally.
  3. L: The length of the weir (in meters).
  4. H: The height of the water above the crest of the weir (in meters).

Who Wrote/Refined the Formula

The concept of weirs has been utilized in hydraulic engineering for centuries, but the specific formula for flow over a broad-crested weir was developed based on empirical observation and the principles of fluid mechanics. This formula is widely used in the field of hydraulic engineering and fluid mechanics.

Real Life Application

Broad-crested weirs are extensively used in hydraulic engineering to control the flow of water in irrigation ditches, canals, and rivers. They are also used to measure the rate of flow in these water bodies. For instance, they are often used in wastewater treatment plants to measure the flow rate of water through the facility.

Key Individuals in the Discipline

While no specific individuals can be linked to the development of the broad-crested weir or the associated formula, figures like Bernoulli, Torricelli, and Darcy have made significant contributions to the field of fluid mechanics, which forms the basis of understanding the principles behind the operation of weirs.

Interesting Facts

  1. The concept of weirs has been used for thousands of years in agriculture for the management of water flow in irrigation systems.
  2. Understanding the operation of broad-crested weirs and the calculation of flow over them is crucial for effective water management, flood prevention, and environmental conservation.
  3. The principle of broad-crested weirs is used in modern flow measurement devices, contributing to the advancement of hydraulic engineering and water management technologies.


Understanding the broad-crested weir and the associated calculations is crucial for hydraulic engineers and anyone involved in water management. This understanding allows for effective control and measurement of water flow in various applications, from agricultural irrigation to wastewater treatment, contributing significantly to our ability to manage water resources effectively and sustainably.

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