I realized that if I don't consider the GW in PCSWMM the simulated surface flow does not have nice recession (the volume of simulated flow is close to volume of measured flow but the simulated peak flows are sharper than the reality). So I thought I could let the flow infiltrate (increased the hydraulic conductivity in green ampt section) and return it to the surface flow gradually by the help of GW. I have most of GW parameters measured for my sub_basins.

by Increasing the infiltration I get lower surface flow so I mostly changed the GW coefficients (A1, B1, A2, B2, A3) to make the model produce higher flow. But not much success. What is your suggestion? I tried to change other GW parameters a little bit as well but they can not be unrealistic values.

Thanks