Using a weir (Figure 8.2(e)). If Q is to be measured throughout the
year for the same stream, measurement can be made by building a dam
with a specially shaped calibration notch. Such a dam is called a weir.
The height of flow through the notch gives a measure of the flow. The
system is calibrated against a laboratory model having the same form
of notch. The actual calibrations are tabulated in standard handbooks.
Problem 8.2 shows how they are derived.