The approximate discharge over a 4 m long rectangular weir (with suppressed end contractions) with head over the crest as 0.36 m is
Q=23Cd√2gLeH3/2
=1.84LeH3/2(Long rectangular weir)
Le=(L−0.1nH)
=4−0.1×2×0.36
=3.928m
∴Q=1.84×3.928×(.36)3/2=1.56m3/s