U.S. Geological Survey
U.S. Department of the Interior
News Release
Date: Sept. 24, 2007
Contact: Karen Rice 434-297-0106 kcrice@xxxxxxxx
___________________________________________________________________________
Acid Rain Makes Some Shenandoah
National Park Streams Unfavorable to Fish
Many streams in Shenandoah National
Park are vulnerable to acid rain. Steep slopes, small watersheds, and underlying
geology, combined with acid rain make many streams inhospitable to native
fish for extended periods of time, according to the U.S. Geological Survey
(USGS).
“Because of acid rain, Shenandoah
is the third most contaminated park in the national park system,” said
Karen Rice, the USGS scientist who led the study. “Many streams
in the park have low acid neutralizing capacities for periods lasting from
six hours to one week. About 14 percent of the park’s watersheds
will have 3-day episodes of acidity sufficient to kill native fish such
as brook trout. These high acid episodes occur at least once every two
years.”
Acid neutralizing capacity is an
important factor in stream-water quality and biologic health. In Shenandoah
National Park, the rains are typically ten times more acidic than normal
rainfall. The pH of rainfall in the park is usually 4.6, although it has
dipped well below 4.0. Normal rain has a pH of 5.6. (pH is a logarithmic
scale, therefore each whole-number denotes a 10-fold change.)
While this study did not look at
likely impacts to fish populations, the long-term outlook for fish inhabiting
streams with the lowest acid neutralizing capacity is not good. Over the
next 40-100 years, there is a greater than 90 percent probability in the
most vulnerable streams of at least one acid episode every year for four
consecutive years.
The USGS, and the University of
Virginia, in cooperation with the National Park Service began this study
in 2002 to predict stream response to acid rain. They found that
the vulnerability of a stream to acid rain was controlled by a combination
of factors including watershed size, elevation, steepness of gradient and
underlying rock type. Streams with the greatest vulnerability were in small
watersheds with a high elevation, steep gradient, and were underlain by
silicate bedrock. Those underlain by basaltic rocks have a greater
capacity to neutralize acid rain, all other factors being equal.
Reporters: The report,
“Predicting the Vulnerability of Streams to Episodic Acidification and
Potential Effects on Aquatic Biota in Shenandoah National Park, Virginia,”
is available on: http://pubs.usgs.gov/sir/2005/5259/.
A companion fact sheet, “Acid Rain in Shenandoah National Park,
Virginia,” is available on: http://pubs.usgs.gov/fs/2007/3057/
USGS provides science for a changing
world. For more information, visit www.usgs.gov.
Subscribe to USGS News Releases
via our electronic
mailing list or RSS
feed.
***www.usgs.gov***
Diane Noserale
Media Relations, Eastern Region
U.S. Geological Survey
150 National Center
Reston, VA 20192
phone: 703-648-4333
fax: 703-648-4588
