Work out river discharge instantly with clear inputs, formula shown and shareable results.
Discharge is cross-sectional area times mean velocity: 12 m wide, 1.4 m deep and 0.85 m/s gives 14.28 m3/s, or 1.23 million cubic metres a day. Mean velocity is normally about 0.85 of the surface velocity, and in practice it is measured at six-tenths depth across several verticals.
Discharge
Q = A x v = width x depth x mean velocity
Surface velocity correction
mean velocity is about 0.85 x surface velocity
At 0.6 of the depth from the surface for a single reading, or averaging 0.2 and 0.8 depth readings for better accuracy.
Because it measures the water actually delivered. Depth alone says nothing without width and velocity.