$8\mathrm{.}5\mathrm{.}3.$ The water depth just upstream of an irrigation diversion weir is $1\mathrm{.}78$ m $.$ The weir is $1\mathrm{.}21$ m in height and is built across the floor of a $7-$m$-$wide rectangular channel. Determine the depth of water flowing over the crest of the weir and the discharge in the channel. Neglect friction loss and the velocity head upstream.

THE ANSWER IS: yc$=0\mathrm{.}380$ m $,$ Q$=5\mathrm{.}14$ m$^3/$s