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Browse History: Methods (2007) | Potomac River (2006) | Elizabeth River (2006) | Water Quality Index (2006)

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:

Index Map

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Editable Vector Version (SVG)

High Resolution Raster Version (JPG)

Station Data

This map shows the water quality index scores for 2006. 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 were restricted to the Upper Bay region and the upper reaches of tributaries such as the Potomac, Elk, Pocomoke and York Rivers. 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.

Creating this map
This map shows the Water Quality Index values for 2006. 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 using spatial interpolation software.

Ranking

	Score (%)
	0 20 40 60 80 100

Upper Bay
James River
Upper Western Shore
Lower Eastern Shore (Tangier)
Potomac River
Overall Bay
Rappahannock River
Lower Bay
Elizabeth River
Upper Eastern Shore
York River
Choptank River
Mid Bay
Patuxent River
Patapsco and Back Rivers
Lower Western Shore (MD)

This figure ranks each region from best to worst for the Water Quality Index. No reporting region had a high index score, but the highest was the Upper Bay region, due to the relatively high scores for the all the indicators. The Lower Western Shore (MD) and the Patapsco and Back Rivers had the lowest scores. These two regions had the lowest ranking because they had a score of 0% for water clarity and chlorophyll a.

Excel Spreadsheet

Trends Graph

This graph is dynamic, you can check and uncheck regions ( checkboxes in legend), select year range ( click and drag), and export as an image (right click).

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Editable Vector Version (SVG)

Excel Spreadsheet

Additional Info

Relevant Web Sites

Chesapeake Bay Program - Bay Trends and Indicators
MD DNR - Eyes on the Bay
Virginia DEQ - Chesapeake Bay Monitoring Programs

The EcoCheck report card has three main sections: Overview, Region Summaries, and Indicators/Indices.

Click the next (>>) button above to get a guided tour of some of the key features of the report card card website.

This map shows the Health Index grades for all the reporting regions, but mousing over each region also provides a text summary and clicking will direct the user to the region summary page with more details about the health of that region.

The region rankings table provides an easy way to visualize the Water Quality Index (WQI), Biotic Index (BI), and overall Bay Health Index (BHI) for all regions. Once again, mousing over provides extra information - try it yourself and see what is displayed. Region names, and indicator icons also serve as navigation links.

The comparison graph allow users to compare the current report card to previous year's scores. Mousing over provides actual percentages and bars provide a direct link to the region's summary page.

Now you're at the region summary page for the Overall Bay. This page details the scores for all the individual indicators, as well as a dynamically generated conceptual diagram (please scroll down the page to view). Even this diagram has more information onmouseover, and has direct links to the detailed indicator pages. There is also a vector (SVG) version of the diagram available for download so you can edit this in your favorite illustration software.

The trends graph shows all the indicators and indices for the selected region since 1986. You can dynamically turn on and off each of the indicators to show only the data you are most interested in. Mousing over the graph shows percentage scores and you can zoom in for finer detail in certain time periods. There is also a fully editable vector (SVG) version of the graph available for download, along with an Excel spreadsheet of the data.

This is the threshold map for Chlorophyll a. This map is zoomable and panable and also available in fully editable vector (SVG) and JPG versions.

The trends graph on the indicator pages shows the indicator and indices data for each region since 1986. By default, only the Overall Bay region is displayed, but you can turn on as many of the other regions as you wish.

The watershed stream health page has several tabs, but the key one is the interactive Google maps version of the data.

Please wait while the map loads and then test out the ratings toggle options and the "zoom to area" functionality (click on the magnifying glass and then click and drag to select the are to zoom to).