$12\mathrm{.}4$ The data below show the discharge $(Q\frac{m^3}{s})$ recorded at a gauging station between $26$ and $28$ December. It is similar to that shown in Fig. $12\mathrm{.}15.$ The catchment area is $25\mathrm{.}3k{m}^2.($a$)$ Separate the surface runoff and groundwater components of the hydrograph. $($b$)$ Calculate the volume of surface runoff. $($c$)$ Calculate the total average depth of net rainfall on the catchment. If the answer obtained is significantly different to the rainfall shown in Fig. $12\mathrm{.}15,$ explain why.

$\backslash$table$[[$Date$,$Time $(h),Q\frac{m^3}{s}$