A weir is a low dam or overflow structure built across an open channel. It has a specific size and shape with a unique free-flow, head-discharge relationship. Weirs can be used for both high flows with the discharge measured by the water stage in the pool behind the weir or for volumetric flows in extremely low flow conditions that are too small to measure by current meter. Weirs are made of aluminium or stainless steel and the following types are available:
 

Flumes are primary devices that constrict an open channel flow for measurement. Once the flow is backed up behind the constriction there is a defined relationship between the depth up stream and the flow through the constriction. This relationship can either be determined from an equation or a table.

The flume may be operated as a free-flow, single-head measuring device, or operated under submerged-flow conditions where two heads are measured. We can offer

• Parshall Flumes: The Parshall Flume is the most widely used   flume due to its relatively low loss of head.)

• Modified Parshall Flume: A modified Parshall flume is virtually the same as the Parshall flume except that it does not have a diverging section and is used only under free-flow conditions. The modified Parshall flume is recommended for general use because of its simplicity, light weight, and ease of installation. A flume has an accuracy of 2-3 percent under free-flow conditions.

• Cutthroat Flumes: Cutthroat flumes resemble Parshall flumes with the throat „cut out“.

• H-Flume: The H-Flume is most commonly used to monitor agricultural field runoff and plot studies. The design of H-type flumes uses features of both flumes and weirs.

• Cutthroat Collapsible Flumes: Cutthroat Flumes are ideal for measuring water flow rates where an easily portable, completely collapsible flume is needed. Common uses are in stream surveys, evaporation studies, drainage surveys, and well pumping tests.