Hello class,
The end of the semester is here and for our final assignment I will summarize what I have learned regarding my selected watershed. Pond Branch watershed is made up of three smaller watersheds:
- Pond Branch itself is in the northernmost portion of the watershed
- Clarks Branch is to the south and east
- Mine Run is to the south of that and meets the Potomac River at the upstream end of Great Falls Watershed history
Percent Impervious Area
The amount of development in the watershed area is referred to as percent impervious. This is the percentage of the land surface covered by roads, parking lots, driveways and rooftops that prevents rainfall from infiltrating into the soil. Five percent of the Nichol Run and Pond Branch watersheds are impervious (Fairfax Country Stormwater Planning Division, 2008).
Stream bank erosion
In 2003 the county conducted the stream Physical Assessment survey to document the conditions of the stream and areas with stream erosion. Most of the streams including Mine run showed some impact from stream bank erosion (Fairfax County Stormwater Planning Divison, 2011).
Habitat Conditions
The results of the 2001 baseline Stream Protection Strategy monitoring study indicate that the overall health of streams in the Nichol Run and Pond Branch watersheds ranges from “excellent” to “good” on a five-category rating scale. The Fairfax County Stream Physical Assessment found the following breakdown of Nichol Run and Pond Branch’s stream habitat condition (Fairfax Country Stormwater Planning Division, 2008):
Location
Pond Branch watershed (8.4 square miles) is located in the northernmost part of Fairfax County and drain to the Potomac River.
Water Quality
Urbanization increases the amount of pollutants that wash off the land and goes into the streams. Pond Branch watershed streams range from good to very poor. Poor and very poor reaches are concentrated around the upstream area and good reaches are generally located in the tributaries draining into the downstream area. The upstream area is characterized mainly by low density residential development and the downstream area is characterized mainly by estate residential development and open space. The Mine Run watershed management area (WMA) is located along the southern border of the Pond Branch watershed and is approximately 1,634 acres in size (2.6 square miles). Approximately 6.9 miles of perennial streams exist within the Mine Run WMA. (Fairfax County Stormwater Planning Divison , 2011)
E.coli monitoring
It is easy to forget that when it rains, water washes over the land picking up traces of anything that is on the ground such as oil and grease from the roads; household chemicals that are improperly disposed of; fertilizer and herbicides from lawns and gardens; not to mention traces of animal manure found in farmlands. This water then flows either into storm drains or directly into the water streams. In 2006, the Department of Environmental Quality found that about a mile of Mine Run, showed elevated levels of E. coli. Such waters have “impaired” water quality and per the Clean Water Act are required to be listed on Virginia’s 303(d) list. However, it has since been re-tested and came out negative for e-coli. However, (Fairfax County Stormwater Planning Divison , 2011).
Pond Branch Potomac Wathershed Exploration 