Modeling in a GIS requires several input maps.  These are added together to simulate factors that affect water quality such as septic system operation and erosion.  ???We created a septic suitability model to show areas in the watershed that are suitable and unsuitable for septic systems.  We also created an erosion potential model to show areas that have high potential to affect water quality through erosion and runoff.  I will first talk about the septic suitability model.