TMDL Studies

Beaver Creek Watershed

The TMDL final report is available for download at the DEQ Website.

 

The Beaver Creek watershed (VAV-B18R, 10,205 acres) is located in Rockingham County, Virginia, to the west of Harrisonburg. Beaver Creek is a tributary of the North River (USGS Hydrologic Unit Code 02070005), which in turn, is a tributary of the South Fork of the Shenandoah River. The Shenandoah River flows into the Potomac River. The Potomac River discharges into the Chesapeake Bay. A major contributor to flow in Beaver Creek is a spring located about 4.4 stream miles upstream of the watershed outlet.

Water quality samples collected in Beaver Creek over a period of 10 years (1994 – 2003) indicated that 52% of the samples violated the new instantaneous water quality standard for fecal coliform (400 colony forming units (cfu) / 100 ml). The majority of the bacteria come from nonpoint sources, agriculture being the largest of these sources. The HSPF model was used to determine allocation reductions. Since there was no stream gage within the watershed, only the water quality portion of the model could be calibrated. Calibrated hydrologic parameters were taken from a model file for a nearby watershed. A large spring whose flow intercepted Beaver Creek about halfway down the watershed necessitated the development of a TMDL at two locations in the watershed: upstream of the confluence with the spring, and at the watershed outlet. The low flow above the spring confluence caused high reductions to be called for in all source categories in the upper portion of the watershed. Two possible reduction scenarios were developed for the lower portion of the watershed, each with high reductions in bacteria from pasture areas and straight pipes and varied reductions from other sources.

Beaver Creek was also listed for a benthic impairment. A stressor analysis performed by Center personnel was completed for Beaver Creek to delist the benthic impairment for two reasons. A historic polluter shown to be the likely source of organic matter (the primary historic stressor the stream) had closed down in 2002. Additionally, three of four recent benthic assessments show no impairment on the creek; the remaining assessment shows only a slight impairment (benthic impairments are listed based on assessment of severe or moderate impairment, not slight impairment).