I think it will be easy for ...

I think it will be easy for you to choose the right parameters.  The hard part is to determine the  number of samples and how to deal with the hydrologic variability, such as rainfall depth, intensity, antecedent conditions, basin geometry, etc.    Many use models such as SWMM to model the catchment and calibrate it with the desired water quality parameters.      I think this is where your challenge will be.