The unique shape of the H flume – more weir than flume – has meant that the discharge equation for the flume is, in fact, not one equation but three equations:  one for low flows, one for transitional flows, and one for main flows.

Bos et al simplified these equations into one standard relationship:

In the Teledyne Isco Open Channel Flow Measurement Handbook, 8th Edition, Teledyne goes further to provide simplified, single variable discharge equations for the various sizes of H flumes (not HS or HL).  These equations are intended to provide flow over the full scale of the table and may vary at the low / high ends of the discharge range.

Free-flow discharge tables for HS / H / HL flumes can be found in the Discharge Tables section.