A $200$ km long rectangular channel $)=(5m$ has a reservoir at the upstream end and a gate at the downstream end. Initially the flow condition in the canal are uniform at $V=0\mathrm{.}35\frac{m}{s}$ and $y=1\mathrm{.}05m.$ The water surface level in the reservoir begins to rise at a rate of $0\mathrm{.}2\frac{m}{h}$ for $6$ h $.$ Calculate the flow condition in the canal at $t=2h.$ Assume $S_0=S_r=0.$ Use Leapfrog Scheme and take appropriate $x$ and $t.$