Weir is one of the simplest and most accurate water measuring structures for measuring flow. It is a structure that sets up a breast wall at an appropriate place in the channel, which is built horizontally in the open channel with a gap, so that water flows through the gap, and the flow is measured according to the structure.
The shape of the weir can be divided into rectangular, trapezoidal, triangular, parabolic and other regular shapes according to the shape of the gap. Among them, rectangular, trapezoidal and 90-degree triangular weirs are the most common