I'm trying to plan a wetland preservation. This is the DEM I have:
My aim is to hold as much rainwater as possible in my area of interest (red poly) by building (as few as possible) new and raising existing dams. As the soils are (mostly) impermeable to water I only have to analyse the surface runoff (and plant transpiration, this is done separately). I already tried calculating the watersheds of surrounding pour points (Different watersheds for same area because of "burned streams"). Since I'm not directly interested in where the water comes from which reaches the pour points but concerned where the water is flowing to which falls as rain, I'm asking myself if this is the right way to handle my task or if there are better solutions.
What would be the correct and best practice way to solve this problem?