The long-term stream quality assessment program supports the Board of Supervisor’s Environmental Excellence for Fairfax County, a 20-year Vision, by providing a comprehensive study of the physical, chemical and biological conditions for Fairfax County's streams.
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The program simultaneously meets the requirements in local, state, and federal regulations, including:
The program is developing a substantial dataset, which over time
will be used to determine the overall rate of change or trends in
the conditions of Fairfax County’s streams. |
Stream Conditions | Monitoring Methods | Annual Reports | Get Involved!
Stream Conditions
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Countywide ConditionsBased on biological data collected at 30 randomly selected locations throughout Fairfax County in 2004, approximately 80 percent of Fairfax County's streams are in fair to very poor condition. This indicates a notable decrease in biological diversity and that our streams are significantly impaired. Map showing 2004 Biological Monitoring Site Locations in Fairfax County
Fairfax County Health
Department Water Quality Statement for Recreational Use of County
Streams |
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Volunteer Trend RankingsWhile the county's monitoring sites will change from year to year, data collected by volunteers through the Audubon Naturalist Society and Northern Virginia Soil and Water Conservation District provide a reliable source of data that can be used to determine trends in our stream quality. In 2004, volunteers through the Northern Virginia Soil and Water Conservation District collected benthic macroinvertebrate (aquatic bug) information at 48 locations. Volunteer monitoring results indicate 81 percent of the sites rate as unacceptable (or unhealthy). Species that are tolerant to pollution dominate the benthic macroinvertebrate community. Volunteer data collected in the future will be compared across years to determine if the quality of the streams are improving or getting worse. Map showing Fairfax County Volunteer Stream Monitoring Site Locations |
Stream Quality Index
The Stream Quality Index is computed based on the benthic macroinvertebrate data that are collected by the county. This index is reported annually to evaluate trends in the overall health of streams countywide.
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The index values for the 1999 Stream Protection Strategy Baseline Study data compared to the 2004 stratified random sampling data suggest a small decline in overall stream quality. However, it is difficult to make any broad statements about trends in the overall health of streams countywide based on data from only two sampling years. As more data is collected, the trends in streams conditions countywide will be more valid and more apparent.
Monitoring Methods
Every year, several randomly selected streams in Fairfax County are monitored for several water quality parameters including: bacteria, benthic macroinvertebrates, fish, and habitat. Water chemistry parameters, such as water temperature, dissolved oxygen, specific conductance, and pH are also collected four times per year. The results of the monitoring events are compiled into an annual report and are also used to support the county's Environmental Quality Advisory Council's Annual Report on the Environment.
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| Bacteria and Water Chemistry | Benthic Macroinvertebrates | Fish Community | Habitat Quality |
Annual Reports
Annual Report on Fairfax County's Streams, November 2006 and November 2005
Fairfax County Health Department's Annual Stream Water Quality Reports, 1997 - 2002
Stream Protection Strategy Baseline Study Report, January 2001
Get Involved!
Volunteer Biological
Stream Monitoring
Data, collected by Audubon Naturalist Society and Northern Virginia Soil
and Water Conservation District volunteers, are incorporated into a
number of different water quality reports, including the county's Stream
Protection Strategy Baseline Study and ongoing stream quality assessment
reports.
For more information on the county's Stream Quality Assessment Program, please contact the Stormwater Planning Division, 703-324-5500, TTY 711.