When using the Constant Flow seepage method for a pond, the reported seepage is less than the valve that was entered.
There is a stability filter that limit the seepage at low pond depth. For instance at the beginning of a storm, the inflow may be less than the constant infiltration rate. The result of this stability filter is that there will sometimes be smaller seepage than expected.
No seepage results from pond in SewerGEMS or CivilStorm
Pond and pond outlet assumptions in StormCAD, SewerGEMS, CivilStorm and SewerCAD
Using the Average Infiltration (Seepage) method for ponds