Statewide GIS-based ranking of watersheds for agricultural pollution prevention

In efforts to control and reduce agricultural nonpoint pollution, it is important to identify critical contributing source areas. A geographic information system (GIS), combined with a pollutant generation and transport model, can be used to identify and rank critical pollutant source areas on a regional basis. In this study, a GIS-based, statewide screening model was used to rank the agricultural pollution potential of 104 watersheds in Pennsylvania. Cost constraints were an overwhelming factor in determining which data could be used and assumptions that had to be made to simplify the model. The ranking index was composed of four components: a runoff index, a sediment production index, and animal loading index, and a chemical use index. The ranking allowed identification of critical nonpoint-pollutant contributing watersheds in Pennsylvania and is useful for targeting further investigations and control programs. A similar GIS approach could be useful in other state and regional studies. -from Authors