In which locations should a weir be used to measure water?

Using a weir to measure water is particularly effective in open channels. A weir is a barrier that directs the flow of water and allows for measurement of the volume of water flowing over it. This method takes advantage of the relationship between the height of water flowing over the weir (head) and the flow rate, which is well established and documented.

In open channels, the flow is typically unconfined, allowing for accurate flow measurement due to the consistent width and shape of the channel. The characteristics of open channels make them ideal for the use of weirs, as the weir can create a stable flow condition, enabling precise readings of water levels.

In contrast, measuring water flow via weirs in pipes, storage tanks, or pressure vessels can lead to inaccuracies. Pipes and pressure vessels typically contain confined flows that do not behave in the same predictable manner as open channel flows, while storage tanks can have variable flow patterns and water levels that are not conducive to the principles governing weir measurements.