Vulnerability of Streams to Episodic Acidification in Shenandoah National Park

Karen C. Rice, USGS
Frank R. Deviney, Jr., University of Virginia
James R. Webb, University of Virginia

A critical resource-management problem within Shenandoah National Park is air quality, 
in particular acid rain and its effects on streamwater quality. For example, Paine Run, in 
the park, is currently on the American Rivers' most endangered list because of the effects 
of acid deposition. Other streams in Shenandoah National Park likely are similarly 
threatened. Baseflow streamwater chemistry is strongly influenced by bedrock geology, 
but during precipitation events, other factors, such as topography, also influence 
streamwater chemistry. 

The study objective was to develop a vulnerability map that shows the predicted 
frequency, duration, and magnitude of episodic acidification events in Shenandoah 
National Park streams. University of Virginia researchers have continuous discharge data 
and discontinuous acid-neutralizing capacity (ANC) data for three streams in the park, 
including at Paine Run. A transfer function — the natural log of discharge regressed against 
ANC — was used to develop a time-series model of hourly stream ANC for each of the 
three streams. The models were subsequently used to characterize the frequency, duration, 
and magnitude of ANC excursions from baseflow concentrations. The models were 
extrapolated to nearby catchments with limited data, by application of filters to the models. 
The vulnerability map provides important information to better understand a critical stress 
to the park's aquatic ecosystem.

Rice, K.C., Deviney, F.A., Jr., and Webb, J.R., 2004, Vulnerability of Streams to Episodic 
Acidification in Shenandoah National Park [abs.]: Virginia Water Research Symposium, 
Oct. 4-6, 2004, Blacksburg, Va.

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