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INDICATORS OF CHANGE IN MID-ATLANTIC WATERSHEDS, AND CONSEQUENCES IN UPPER CHESAPEAKE BAY
Citation:
Walker, H A., B. Yarnal, V. M. Berounsky, E H. Dettmann, J S. Latimer, AND N A. Jaworski. INDICATORS OF CHANGE IN MID-ATLANTIC WATERSHEDS, AND CONSEQUENCES IN UPPER CHESAPEAKE BAY. Presented at Federal Interagency Workshop on Urban Sprawl, Harpers Ferry, WV, December 6-8, 2000.
Description:
The rate of change of atmospheric temperature in the Northern Hemisphere in the past century relative to the preceding millennium strongly suggests that we are in a period of rapid global climate change. The mid-Atlantic region is quite sensitive to larger-scale climate variation, which affects the frequency and severity of storminess, drought, and flooding. Human activity enhances that sensitivity to climate variation. Anthropogenic alteration of watersheds has increased risks associated with climate extremes. Due to increases in nutrient loading to watersheds, nitrogen flux per unit flow has increased over time. Wet years now have different consequences in coastal receiving waters than equivalent wet years in previous centuries. In addition, increasing demands for water mean that regional drought can have increasing adverse impacts. We illustrate these points using a combination of modem observations and proxy indicators from the past 300 years using tree rings and marine sediment cores. Time series with monthly resolution from the past century illustrate variations in: 1) soil moisture based on NOAA climate division data, and 2) nutrient inputs and water quality changes in the Potomac River. Basin-scale variations in the Palmer Drought Severity Index are estimated for upper Chesapeake Bay watersheds and associated with water quality changes in the Potomac River and Chesapeake Bay. These examples illustrate ecosystem sensitivity to climate variation and increasing human and ecological vulnerability to both wet and dry extremes of climate.