Rehbock weir formula

Probably the most accurate formula for the rate of flow of water over a rectangular suppressed weir; it includes a correction for the velocity of approach for normal, or fairly uniform, velocity distribution in the upstream channel; the formula is Q = [3.234 + 5.347/(320 h- 3) + 0.428 h / d₀] lh ^3/2, where Q is the flow rate in cubic feet per second, l is the width of the weir in feet, h is the head of water above the crest of the weir in feet, and d₀ is the height of weir or depth of water at zero head in feet.