Shenandoah National Park is the origin of the headwaters of three river systems in the Mid-Atlantic area. The Shenandoah/Potomac River to the west and the Rappahannock and James Rivers to the east. Each of these rivers flows into Chesapeake Bay. These waters constitute a significant portion of the greater Chesapeake Bay Watershed.
Within park boundaries there are 70 watersheds: 42 on the west side of Shenandoah and 28 on the east. Watershed sizes range from 0.2mi2 to 12.1mi2. Most are in the range of 1-2mi2 in size. Park staff is in the process of developing attribute information for each of these watersheds including basin width and length, main channel length, stream density, land use, and elevation.
GroundwaterSeveral significant publications (DeKay 1972, Lynch 1987, Plummer 2001), all cited below in the Data, Reports, and Other Products section, provide both general descriptions of groundwater conditions throughout the park as well as specific conditions in the Big Meadows area. Groundwater withdrawal and condition are of particular interest because of relationships between high elevation ridge tops that tend to receive more moisture but that do not accumulate the water, presence of visitor use facilities along the crest of the ridge with associated high demand for potable water and withdrawal problems, and potential exposure to pollutants.
Current, clear information regarding the location and condition of springs and seeps is lacking for Shenandoah National Park. One report (DeKay 1972) indicates that there are as many as 854 surface water sources in the park. It is unclear whether or not this number represents springs alone or if other surface waters (streams primarily) are included. Most information about springs in the park has focused on roughly 70 springs that are located near Skyline Drive. Park staff members have prepared a request for funding to support an investigation to learn more about these important water resources.
Surface WatersThe locations of rivers and streams in Shenandoah are documented well on U.S. Geological Survey topographic maps as well as other map products. The park’s Geographic Information System database includes surface water layers. There are approximately 90 streams in the park. 72 of the streams are considered perennial. Extensive information is also available that describes the quality of these waters. Refer to the following section (Data, Reports, and Other Products) for access to this information.
Stream flows are largely affected by precipitation patterns. Higher runoff occurs in the central portion of the park and on the eastern side of the Blue Ridge. Peak stream flows generally occur in the spring. Two reports cited below (Data, Reports, and Other Products) are the primary sources for this information.
East slope streams tend to be larger and more dendritic, fed by one or more perennial tributaries and a number of associated springs. In contrast, west slope streams tend to be more linear and fed by fewer springs as most originate from much dryer south and west facing ridges. The lengths of those portions of streams that flow in the park range from 3.1 to 5 miles. Chief features of these streams are that they are high elevation, with high gradients, and have pools interspersed with riffles, rapids, cascades and falls. In many places, streams drop over ledges creating waterfalls up to 85 feet. Stream bottoms are chiefly gravel, rubble, boulder, and bedrock. Most streams are heavily shaded and cool or even cold in the summer and are typically clear with rain-caused turbidity quickly disappearing.
Water QualityAs a result of high air pollution levels, atmospheric deposition in Shenandoah National Park is the greatest threat to the protected mountain streams. Acid precipitation, a type of atmospheric deposition that is primarily linked to fossil fuel combustion, is lowering water pH in some extremely sensitive streams both chronically and episodically. The low buffering capacity of a large percentage of soils in the park provides limited protection from acid depositions. Because of the sensitivity of the streams in the park to acidification, long-term monitoring of stream water chemistry and hydrogeochemical processes is a major component of the Inventory and Monitoring Program in the park.
Last updated: January 19, 2018