WeirMAC Weir Discharge Calculator
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WeirMAC — weir discharge calculator with head–discharge rating curve

1Weir & Flow Parameters

Set the weir coefficient, then pick the unknown to solve for — flow, crest length, or head. US customary units.

Weir coefficient C
–
Crest length Leffective weir length
ft
Head Hhead on the crest
ft
Flow Qdischarge over the weirdischarge
cfs

2Result

Discharge — Q —
Unit discharge — q
—cfs/ft
Head : length — H/L
—
Calculation audit
Q = C·L·H^(3/2)  |  L = Q / (C·H^(3/2))  |  H = (Q / (C·L))^(2/3)  |  q = Q/L  (ft, cfs)

3Weir Elevation

front view · gray buffer surround with freeboard · length & head scaled independently

4Head–Discharge Rating Curve

head H (y) vs discharge Q (x) at the current C and L · marker = operating point