 |
 |
 |
 |
 |
 |
 |
Wild Trout VII, Yellowstone National Park, October 2000
J.R. Webb, F.A. Deviney, Jr., B.J. Cosby, A.J. Bulger, J.N. Galloway
Department
of Environmental Sciences
University of Virginia
Charlottesville, Virginia 22903
Introduction
Although recent and prospective reductions in precursor emissions may reduce the impact of acidic deposition on surface water resources in many regions of the United States, some areas remain at risk [U.S. EPA, 1995]. As summarized by Cosby et al. [1991] and Herlihy et al. [1993], the Mid-Appalachian region is one of the areas in the United States most affected by acidic deposition and surface waters in this region are susceptible to further acidification for several reasons; including high rates of acidic deposition, the presence of watersheds with base-poor bedrock, and the delayed-response properties of regional soils. The results of the 1987 VTSSS survey indicated that the mountainous watersheds of Virginia that support native brook trout (Salvelinus fontinalis) are especially sensitive to the effects of acidic deposition [Webb et al., 1989].
These watersheds are predominantly on public lands managed by the National Park Service, the U.S.D.A. Forest Service, and the Commonwealth of Virginia. Researchers, resource managers, and public user groups are interested in whether the reductions in sulfur emissions mandated by the Clean Air Act of 1990 will be sufficient to effect improvements in the acid-base status of these waters. Other monitoring programs have been too broadly based to adequately assess changes in this specific set of waters. We have taken two approaches to measuring status and changes in water quality. The first approach involves comparing results for near-census surveys separated by great intervals in time: An approach that requires organization and training of a large number of people for one-time events. The second approach involves analyses of trends in data obtained from quarterly sampling on a subset of the population: An approach that requires a continuous dedication of resources. We have examined data obtained through both of these approaches for specific evidence of recovery from acidification--decreasing concentrations of sulfate and increasing ANC.
|
