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Water Quality Standards Achievement

Results of the 2011-2013 assessment period indicate that 29 percent of the water quality standards for the Chesapeake Bay were met during this time. This single indicator reflects the achievement of water quality standards for dissolved oxygen, water clarity/underwater grasses and chlorophyll a by the Bay and its tidal tributaries.





September 03, 2013

Scientists from Maryland Department of Natural Resources and University of Maryland’s Chesapeake Biological Laboratory show us key methods for tracking nutrient levels and determining the health of the Chesapeake Bay.
Closed Captions: http://www.youtube.com/watch?v=U1prV3zpeZA

Importance

Excess nutrients and sediment are among the leading causes of the Chesapeake Bay’s poor health. Both can impact the clarity of water and the amount of algae and oxygen it contains. This indicator measures the achievement of water quality standards in the Bay for each of these environmental factors. 

Water quality standards for the Bay were developed in 2003 by the U.S. Environmental Protection Agency (EPA). Within these standards, five aquatic habitats—also called “designated uses”—were identified, each with its own criteria for dissolved oxygen, water clarity/underwater grasses and chlorophyll a. If the Bay and its tidal tributaries are to function as a healthy ecosystem, all designated uses must meet all clean water criteria.

Goal

In 2014, the Chesapeake Bay Program adopted a goal to reduce pollution and achieve the water quality necessary to protect human health and support the region’s underwater resources.

Long-term trend (1985-2013) 

A straight line trend analysis shows a positive trend in the percentage of water quality standards met in the Chesapeake Bay between 1985 and 2013.

Short-term trend (2002-2013)

A straight line trend analysis shows no significant trend in the percentage of water quality standards met in the Bay between 2002 and 2013.

Change from previous reporting period (2010-2012 to 2011-2013)

Results of the 2011-2013 assessment period indicate that 29 percent of the water quality standards for the Bay were attained during this time. These results are not significantly different from those of the previous assessment period (2010-2012), in which 31 percent of water quality standards were attained.

Additional Information

Analyzing data

The methodology used to calculate this indicator considers the achievement or non-achievement of water quality standards for dissolved oxygen, water clarity/underwater grasses and chlorophyll a applicable to a designated use within a particular segment. Rather than reporting progress when all designated uses meet standards within a segment, this methodology reports progress when any designated use meets a standard within that segment. This means that instead of reporting on the 92 segments used in the establishment of the Chesapeake Bay’s “pollution diet,” or Total Maximum Daily Load (TMDL), this methodology reports on the 291 designated-use segments contained therein.

This indicator uses a surface area-weighted approach, which multiplies the surface area of a segment by its designated uses and criteria. This approach takes the relative size of each segment into account, ensuring we report the best available measure of water quality standards achievement in the Bay. This approach also gives equal weight to the achievement of the criteria protective of each designated use and segment, preventing any need to weigh differently the importance of restoring dissolved oxygen versus restoring underwater grasses, for example. The indicator combines the assessments of dissolved oxygen, water clarity/underwater grasses and chlorophyll a into a single indicator of water quality, measured against the goal of meeting all three standards across the Bay.

Reporting data

This indicator measures progress toward the achievement of water quality standards for dissolved oxygen, water clarity/underwater grasses and chlorophyll a in three-year assessment periods beginning in 1985. The indicator is consistent with how Delaware, the District of Columbia, Maryland and Virginia list their portions of the Bay’s tidal waters and illustrates Bay-wide improvements over time.

Source of Data

Chesapeake Bay Program

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Annapolis, Maryland 21403
Tel: (800) YOUR-BAY / Fax: (410) 267-5777
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