A Nonpoint Source Pollutant Loading Model for Small Suburban Watersheds

A nonpoint-point source lumped-parameter pollutant loading model appropriate for prediction of average yearly loads on small suburban watersheds has been developed. Three numerical physical process models describing transport processes observed in such watersheds are included; a build up- wash off model, a stream bank erosion model, and a land surface erosion model are implemented in a program written for general use with a Microsoft® Excel Graphical User Interface. The functionality of this model, Swarthmore Subwatershed-Scale Nonpoint Source Pollutant Model (SSSN) is demonstrated through a case study application to the Little Crum Creek Watershed, located in the suburban area near Philadelphia, Pennsylvania. The predicted loads are found to be within a reasonable margin of hourly simulation models and previous applications of more complex models, indicating its utility as a tool for TMDL regulation. This has been coupled with a resource optimization model, StormWISE, and combined results are presented.