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Browse History: Methods (2013)

Chesapeake Bay - Methods


New indicators and methods for the Chesapeake Bay report card from 2012 through the present

For the past seven years, three water quality indicators and three biotic indicators have been averaged into a Water Quality Index and a Biotic Index, which have then been averaged into an overall Bay Heath Index. This Index has been calculated for fifteen reporting regions Baywide. For the first time, in 2012, five water quality indicators–chlorophyll a, dissolved oxygen, water clarity, total nitrogen, and total phosphorus–and two biotic indicators–benthic index of biotic integrity and aquatic grasses–were equally weighted and averaged into an overall Bay Health Index for fifteen reporting regions and Baywide. These new methods leave out the phytoplankton community, which has not been analyzed in Maryland since 2011. It adds total nitrogen and total phosphorus, which are key nutrients in the Bay.

Indicators in the current report card compared to prior years

Old and new indicators table

General Methods

Ecosystem health report cards are an effective means of tracking and reporting the health of a waterway at both local and regional scales. A report card has been developed within the Chesapeake Bay science and management community in order to provide a transparent, timely, and geographically detailed annual assessment of Chesapeake Bay health.

Ecocheck methods newsletter

Calculating the Chesapeake Bay report card scores

This newsletter was produced for the inaugural report card in 2006, but the methods described are the same for all years. Click thumbnail to download.


Technical Methods Document

Development and evaluation of a spatially-explicit index of Chesapeake Bay health
Marine Pollution Bulletin 59(1-3): 14-25

This paper provides a more detailed of the methodology employed in generating the Bay Health Index.


Technical Methods Document

Supporting analysis for the report card scores

This document summarizes additional water quality analysis conducted for some reporting regions. This report was produced for the 2007 report card. Analysis was conducted for the Tidal Monitoring and Anlaysis workgroup by Jeni Keisman. Click thumbnail to download.


Reporting Regions

Reporting Regions Map


Comparing Health Reports

The Chesapeake Bay report card is unique in that it provides a geographically detailed and integrated approach to form numerical rankings of 15 reporting regions on an annual basis. This approach compliments those focusing on Bay-wide assessment over longer time frames. The geographic detail provided in the report card reflects the complexity of Chesapeake Bay and its tributaries, and provides information that can help guide and focus restoration efforts. The report card is a developing product, with a more complete assessment of Bay health expected in the future. Future report cards will aim to include indicators of fish and shellfish status at suitable spatial scales and time frames.

Report Card Cover

Chesapeake Bay Report Card

  • Bay and tributary specific assessment using six indicators
  • Integrated into an index
  • Provides full assessment since 2006 and trends since 1986
  • Numerical rankings of reporting regions
  • Continued development and refinement required

CBP Report Cardpdf icon

Chesapeake Bay health and restoration assessment

  • Bay-wide assessment using 13 indicators
  • Provides assessment for the past 20 years
  • Numerical ranking of Bay-wide indicators
  • Continued development and refinement required