= Broad-crested weir
{title2=$Q=W\sqrt{g'}(2\delta/3)^{3/2}$}
For reservoir head $\delta$ above a broad crest, negligible approach <velocity>, constant <reduced gravity>, and no head loss, <hydraulic control> gives $\delta=3h_c/2$ and the displayed discharge. Reflecting the vertical coordinate gives the same result for a light layer escaping beneath a lowered roof. An orifice discharge coefficient is a separate closure and should not be silently inserted into this inviscid weir law.
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