Healthy freshwater streams and rivers have local and regional importance. Clean waterways are a benefit to residents who use them for drinking water, family activities, business and other purposes. The watershed’s streams, creeks and rivers also eventually flow into the Bay, so their water quality has a direct impact on the health of the estuary.
An effective way to measure the health of freshwater streams and rivers is to study the many tiny creatures that live in these waters. The abundance and diversity of snails, mussels, insects and other bottom-dwelling organisms -– known as benthic macroinvertebrates -– are good indicators of the health of streams because these creatures can’t move very far and they respond in certain predictable ways to pollution and environmental stresses.
The indicator cannot be related to a goal at this time. However, the status of the health of the benthic macroinvertebrate communities on a scale of very poor to excellent can be portrayed. The results from this indicator will help managers and watershed groups focus efforts to restore streams needing improvement and protect the quality of the healthiest streams.
*Note: The historic data featured in this indicator changed from that reported in the 2007 assessment. The Bay Program and its partners developed an improved stream health indicator that provides a regional assessment of benthic macroinvertebrate community health. Benthic data collected in different ways by various natural resources agencies was incorporated into a Benthic Index of Biotic Integrity (B-IBI) that rates stream health across the entire 64,000-square-mile Bay watershed.
Long-term trend (since start of data collection)
There is no long-term trend; only the average B-IBI scores from 2000-2006 data are portrayed. Although only the 2006 reporting year is shown, many states monitor benthic macroinvertebrates on a rotating cycle, with data included in one reporting year that can reflect a two- to 10-year period.
What is the short-term trend? (10 year trend)
There is no short-term trend; only the average B-IBI scores from 2000-2006 data are portrayed.
Change from previous year
There is no change from the previous year; only the average B-IBI scores from 2000-2006 data are portrayed.
Stream Health
The health of streams varies from very poor to excellent throughout the Bay watershed. Although sampling densities differ, some generalizations about the health of the watershed’s streams can be made:
- Streams tend to be in very poor to fair condition around large urban areas, such as metropolitan Washington, D.C. (see map inset).
- Streams in heavily farmed or mined areas are also often in very poor to fair condition.
- In contrast, streams tend to be in good to excellent condition in forested areas with ample natural habitat and low levels of pollution, such as in the southwestern Pennsylvania region of the watershed (see map inset).
Stream and River Pollution
There are many different causes of polluted streams and rivers across the Bay watershed. Benthic macroinvertebrates are generally harmed by pollutants such as metals, acidity, sediment, pesticides, nitrogen and phosphorus. These pollutants come from sources such as mining, agriculture, urban and suburban runoff, automobile and power plant exhaust, and wastewater treatment facilities.
Data Collection for this Indicator
Most monitoring programs in the Bay watershed collect benthic macroinvertebrate samples with somewhat similar field methods and calculate a common suite of indicators from the data. However, the programs use state-specific protocols to score and evaluate these indicators to identify “impaired” waters for regulatory requirements.
The purpose of this new stream health indicator is to evaluate benthic community health in a uniform manner and in the context of the entire Bay watershed. This approach incorporates the data into an overall watershed-wide, family level Benthic Index of Biotic Integrity (B-IBI), which permits the results to be compared across state boundaries.
This indicator is a first step toward a regional benthic community health assessment; however, future work will continue to improve upon this indicator by standardizing methodologies, developing ways to combine B-IBI results from different sampling designs (targeted vs. random samples), and incorporating data that were not available for analysis this year.
The data used in the indicator were collected by natural resource agencies in Delaware, Maryland, New York, Pennsylvania, Virginia and West Virginia; Fairfax County, Virginia; Montgomery and Prince Georges counties in Maryland; the U.S. Forest Service; and Susquehanna River Basin Commission.
State-by-state Water Quality Assessment Reports
Learn more about the health of the streams and rivers in your portion of the Bay watershed:
Katie Foreman at (800) 968-7229 ext. 837
Chesapeake Bay Program Office