Answer
The mass flux through the surface is $~~347~kg/s$
Work Step by Step
We can find the mass flux through the surface:
$mass~flux = (\rho)~(\frac{w~d}{2})~(v)$
$mass~flux = \frac{(1000~kg/m^3)(3.22~m)(1.04~m)(0.207~m/s)}{2}$
$mass~flux = 347~kg/s$
The mass flux through the surface is $~~347~kg/s$