The equation for groundwater to surface water dilution is as follows:

DFgw-sw = (1 + (Qsw/(Vgw*dsw*Wgwsw))-1

Where

Qsw = surface water flowrate at groundwater to surface water discharge (cm3/s)

Vgw = groundwater darcy velocity (cm/s)

dsw= thickness of affected groundwater to surface water discharge (cm)

Wgwsw = Width of groundwater to surface water discharge (cm)