Overseeing the Water Resources of Loudoun County, VA
WATERSHED ASSESSMENT
The purpose of a watershed assessment is to provide the best possible answer to specific questions about water quality and the health of stream. The types of questions a watershed assessment can answer include: (1) how healthy is a stream, (2) how many steams are severely impacted by human activities, and (3) have development activities and changing land use degraded our streams? Assessing the health of a stream involves measuring the changes caused by disturbing the stream ecosystem. Human impacts on the quality of a watershed are complex, and small individual and cumulative impacts can add up to major degradation problems.
A healthy stream
An impacted stream
Assessment Parameters -- Parameters used to measure human impacts that upset the balanced conditions found in a natural stream ecosystem and cause major degradation problems are: (1) chemical quality of the stream water, (2) water flow, (3) bacteriological quality of the stream water, (4) stream habitat, and (5) the type of organisms living in the stream.
Conducting a habitat assessment
Collecting aquatic insects
Available Data - The best data to use to assess the health of a stream are data collected at randomly selected stations throughout a watershed. Unfortunately, these data do not exist in Loudoun. Instead Loudoun streams have been monitored at stations specifically selected by DEQ and citizen groups usually based on public access. DEQ has sampled 23 stations since the 1970's. The Loudoun Soil and Water Conservation District (LSWCD) have sampled 15 stations since 1999. The Loudoun Wildlife Conservancy (LWC) has sampled 15 stations for at least two years. The North Fork Goose Creek Watershed Committee has sampled 5 stations since 1993 and has added 3 stations in recent years.
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