Focus on the Headwaters The Shenandoah Watershed Study / The Virginia Trout Stream Sensitivity Study Rick Webb Department of Environmental Sciences University of Virginia

SWAS/VTSSS Research Program Objectives to improve understanding of ecosystem processes in the forested mountain watersheds of Shenandoah National Park and the central Appalachian region to detect and assess hydro- biogeochemical changes occurring in these relatively undisturbed ecosystems

Related Science Plan Questions What is the interrelationship between air quality and water quality? What is the interrelationship between soil quality and water retention and water quality?

SWAS-VTSSS Watershed Study Sites 65 streams sampled for water quality analysis on at least a quarterly basis since 1987 Selected to represent relatively pristine conditions and regional bedrock distribution A subset of 450 brook trout streams sampled in 1987 and 2000 George Washington and Jefferson National Forests Shenandoah National Park

George Washington National Forest Shenandoah National Park SWAS-VTSSS Sites in the Shenandoah Basin 16 streams sampled for water quality analysis on at least a quarterly basis since 1987 A subset of 80 brook trout streams sampled in 1987 and streams sampled on a weekly basis Continuous discharge gauging on 3 streams High-frequency sampling during high flow on one stream (Paine Run in Shenandoah National Park) Paine Run

Lithologic Classification Scheme for Western Virginia Based on physical and chemical weathering properties of bedrock Accounts for variation in the chemical and biological composition of streams, soil properties, distribution of vegetation, etc. Acidic streams and streams with low acid neutralizing capacity are mainly associated with siliciclastic rocks Siliciclastic Argillaceous Carbonate Granitic Basaltic

Bedrock Associations in Shenandoah NP Basaltic Watersheds Stream water ANC > 100 µeq/L 5-10 fish species median soil base saturation > 40% Granitic Watersheds Stream water ANC µeq/L 3-6 fish species median soil base saturation ~ 15% Siliciclastic Watersheds Stream water ANC 0-50 µeq/L 1-3 fish species median soil base saturation ~ 10%

Historic Impact of Acidic Deposition Estimated loss of acid neutralizing capacity in Shenandoah National Park streams: µeq/L Siliciclastic Granitic Basaltic Streams associated with siliciclastic bedrock experienced the most acidification –due to depletion of base cations (e.g., Ca 2+ and Mg 2+) and lower sulfur retention capacity in watershed soils. Watershed Bedrock Class

Recovery From Acidification is Not Projected Model projections indicate that the percentages of acidic streams and streams with low acid neutralizing capacity will not change despite ambitious emission reductions. Lack of recovery can be attributed to depletion of base cations and continuing accumulation of sulfate in watershed soils.

the base-cation supply in the soil is stable losses to surface water are replaced by release from bedrock base cations taken up by vegetation are recycled Simple Conceptual Model of Watershed Base Cation Mobility Pre-Industrial Period

sulfate (SO 4 2- ) leaches base cations from soil acidity is buffered at the expense of the base- cation supply in time, base-poor soils are dominated by the acidic cations H + and Al n+ surface water becomes more acidic as soil bases are depleted Post-Industrial Period Simple Conceptual Model of Watershed Base Cation Mobility

New England Lakes Adirondack Lakes Appalachian Streams Upper Midwest Lakes Ridge-Blue Ridge Streams New England Lakes Adirondack Lakes Appalachian Streams Upper Midwest Lakes Ridge-Blue Ridge Streams Slope of Trend (µeq/L/yr) Sulfate Acid Neutralizing Capacity Recovery From Acidification is Not Observed Regional Trends in Surface Water Chemistry: “... one region, the Ridge/Blue Ridge province, has yet to show any signs of recovery, either in SO 4 2- concentrations or acidity... This region has the highest likelihood of undergoing further acidification as the capacity of regional soils to adsorb SO 4 2- reaches capacity. The small increase in surface water SO 4 2- we report for this region should be a red flag to regulators that this region deserves further research and assessment.” (EPA 620/R-03/001)

Priority Research Needs and Data Gaps Shenandoah Valley - Headwaters A integrated assessment of the hydrologic, chemical, and biological status of the headwaters Continued long-term monitoring of stream water composition and discharge in the headwaters Initiation of long-term soil quality monitoring – with an emphasis on acid-base properties