Indicator Details:

This map shows the Water Quality Index scores for 2007. Poor overall water quality is characterized by having low index scores, which is shown by shades of orange and red on the map. Most regions of the Bay had a Water Quality Index score in the poor to moderate range (20-60%). Highest index scores occurred in the Elk River and the Upper Bay and Upper Western Shore regions. Areas of the James and Potomac Rivers also had moderate-good water quality. High index scores in these regions are largely attributed to the dissolved oxygen and chlorophyll a levels. Lowest index scores occurred in the Patapsco and Back Rivers and the Lower Western Shore (MD) tributaries.