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Water Quality Standards Achievement for Chlorophyll a

Results for 2010-2012 indicated that 0 percent of the Bay was attaining water quality standards for chlorophyll a within the open water habitat designated use areas in 7 tidal segments where the chlorophyll a standard is applicable.




Chesapeake Bay Waters Meeting Chlorophyll a Criteria Water Quality Goals 2010-2012

Map: Chesapeake Bay Waters Meeting Chlorophyll a Criteria Water Quality Goals 2010-2012

Date created: Nov 06 2013 / Download

This map demonstrates the attainment status of those Chesapeake Bay Program monitoring segments that have numeric chlorophyll a standards for the Open Water designated use during the 2010-2012 assessment period.




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Importance

This indicator measures progress towards the achievement of water quality standards for chlorophyll a for each 3-year assessment period beginning in 1985.  The indicator is fully consistent with how Delaware, the District of Columbia, Maryland, and Virginia currently list their portion of the Bay’s tidal waters, and provides a means for illustrating improvements through time.

Additional Information

Nutrients, along with sediments, are the primary causes of impairments to the Chesapeake Bay and its tidal tributaries. To meet the objectives of the Clean Water Act, the EPA’s implementing regulations specify that states must adopt criteria that contain sufficient parameters to protect existing and designated uses. In 2003, EPA Region III developed Ambient Water Quality Criteria for Dissolved Oxygen, Water Clarity, and Chlorophyll a for the Chesapeake Bay and Its Tidal Tributaries. This was developed in order to achieve and maintain water quality conditions necessary to protect the aquatic living resources of the Chesapeake Bay and its tidal tributaries from the effects of nutrient and sediment pollution. Within the publication, five designated uses were identified and described, that when adequately protected, will ensure the protection of the living resources therein.

The methodology used for the calculation of the indicator considers the achievement or non-achievement of water quality standards for chlorophyll a within the open water habitat designated use in 7 segments where the chlorophyll a standard is applicable.  This indicator uses a surface area-weighted approach, which factors in the relative size of each segment, ensuring we report the best available measure of how much of Bay tidal waters were achieving water quality standards in the applicable designated use areas.

The University of Maryland Center for Environmental Science reports a different chlorophyll a indicator which tracks data in all tidal water segments and not in relation to Chesapeake Bay water quality standards. The results of that indicator are available at http://ian.umces.edu/ecocheck/report-cards/chesapeake-bay/2012/indicators/chlorophyll_a/ and are updated annually in the Bay Report Card.

Source of Data

Chesapeake Bay Program

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