Prioritizing Subwatersheds for Stormwater Pollution to Wachusett Reservoir

Wachusett Reservoir is a primary drinking water resource for the greater Boston, Massachusetts area. The Wachusett Reservoir Watershed, an area of 280 km2, has been urbanized with an increase in residential, commercial, industrial and transportation areas. Increased impervious surfaces due to urbanization have resulted in large runoff volume and pollutant loads to the reservoir. Annual stormwater pollutant mass loads were estimated in order to prioritize subbasins and identify pollutant hotspots in the watershed. Catchment Prioritization Index (CPI) was calculated using annual stormwater pollutant mass loads and was further used to identify clustered hotspots by applying the Getis-Ord Gi* statistic. The validation with observed data showed higher levels of fecal coliform loading from identified hotspots. Our approach will be useful to prioritize subbasins for developing stormwater monitoring strategies and Best Management Practices (BMPs) implementation in the watershed.