How the PQ works

The PQ measures the water level and the mean flow velocity and calculates the water discharge based on a defined cross-sectional profile with a specified roughness.

The discharge Q is the volume of water V flowing through a cross section of a canal per time unit t. The default metric dimension is m³/s.

By applying the continuity equation the expression above can be transformed into the base equation of the discharge measurement:

where A is the wetted cross-sectional area deduced by the measured water level, and v_m the mean flow velocity.