Mountains of Western Virginia

Abstract

Data are presented for surveys of (1) 344 native brook trout streams in the mountains of western Virginia (80% of all such streams in Virginia), (2) 47 streams draining the Shenandoah National Park in west-central Virginia, and (3) 63 headwater streams in the southwestern portion of the Shenandoah National Park. Based on analyses of these survey data and of six years of data from two intensively monitored catchments in the park, we concluded that the mountain streams of Virginia are at considerable risk to damage from acidic deposition. In the largest of the stream surveys, 93% of the streams have ANC concentrations < 200 µeq L⁻¹, 49% of the streams have ANC concentrations < 50 µeq L⁻¹; and 10% of the streams are currently acidic (ANC ≤ 0). Sulfate is the major anion in most streams with low ANC. All catchments surveyed are retaining a significant proportion of atmospherically deposited sulfur; median sulfate retention for all streams surveyed is approximately 60%. Bedrock geology appears to exert the strongest control on the variability of ANC in the streams within the region. Streams in the Valley and Ridge province have lower ANC and higher sulfate concentrations than streams in the Blue Ridge province. The potential for damage to fish populations is large, and at least one instance of decline in fish and invertebrate populations has been reported in the region.