Weirs to Measure Flow

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. 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. The biggest difference between a weir and a flume is that a weir creates a pond upstream of the weir, while a flume requires much less upstream depth. This often prevents weirs from being used in flat canals or ditches, or canals with little head upstream.

Weirs are available in a variety of shapes and sizes, but the most common and most simple are the Rectangular, Cipolletti, and the V-Notch weirs. The style of weir required depends on your particular application.

We offer weirs made of fiberglass or steel. We can also design a weir for you that can be built of concrete on-site. To learn more about weirs and for assistance in selecting the correct type please contact us for a no-obligation consultation.

Box Weirs

Box weirs are also available and are convenient in many applications. They are often used when an application requires a control section and baffles to calm and control the water before being measured at the weir plate. A weir box can be installed with inlet and outlet pipe adapters as shown in the image on the right.


We carry a wide variety of sensors that can automatically measure and record flow rate through a flume or weir. This data can optionally be transmitted over radio or the internet, allowing you to monitor your flume from home or on your cell phone. Click the link below to learn more.

Water Level Sensor


Sensors for monitoring flumes and weirs, including ultrasonic sensors, floats and pulleys, pressure transducers, bubblers, and radar level sensors.