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Browse History: Lower Western Shore (MD) (2008) | Upper Western Shore (2008) | Phytoplankton Index of Biotic Integrity (2008) | Water Quality Index (2008)
Indicator Icon Water Quality Index

The Water Quality Index combines the water quality threshold scores (chlorophyll a, water clarity, and dissolved oxygen) into a single overarching index. Good overall water quality is characterized by having high index scores (green). Poor overall water quality is characterized by having low index scores (orange and red).

Chesapeake Bay - Indicator Details:





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Index Map


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This map shows the Water Quality Index scores for 2008. Poor overall water quality is indicated by low index scores, and 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%); this is consistent with spatial patterns in recent years. The highest index scores occurred in the Elk River (Upper Eastern Shore region) and the Upper Bay region. 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. The lowest index scores occurred in the Lower Western Shore (MD) and Patapsco and Back Rivers.

Creating this map
This map shows the Water Quality Index values for the current year. At each of the 144 monitoring station, the percent (%) frequency that each water quality parameter meets the threshold levels was calculated to provide the Water Quality Index score. Water quality index scores between stations was then estimated by interpolation to visualize spatial patterns and trends.

Ranking


Comparison of Bay Health Index scores for 2010 () compared to
()


Score Legend
 Score (%)
 0               20               40               60               80              100
  
James River  
Upper Bay  
Choptank River  
Upper Western Shore  
Mid Bay  
Overall Bay  
Lower Bay  
Potomac River  
Lower Eastern Shore (Tangier)  
York River  
Rappahannock River  
Upper Eastern Shore  
Patuxent River  
Elizabeth River  
Lower Western Shore (MD)  
Patapsco and Back Rivers  

This figure ranks each region from best to worst Water Quality Index (WQI) score for 2008. The highest ranked region in 2008 was the James River with a score of 56%, followed by the Upper Bay at 53%. The Lower Western Shore (MD) was the lowest ranked score in 2008 with a very poor score of 16%, a decrease from 23% in 2007. Poor Water Quality Index scores (20 to 40%) occurred in many regions including the Patapsco and Back Rivers and the Patuxent, Elizabeth, and York Rivers, as well as the Mid Bay, Upper Eastern Shore, and Lower Bay regions.


Excel Spreadsheet