Monitoring: a vital component of science at USGS WEBB sites

The U.S. Geological Survey launched its Water, Energy, and Biogeochemical Budgets (WEBB) program in 1991 with the establishment of five long-term research watersheds. Monitoring of climate, hydrology, and chemistry is the cornerstone of WEBB scientific investigations. At Loch Vale, CO, long-term streamflow and climate monitoring indicated an increase rather than the expected decrease in the runoff:precipitation ratio during a drought in the early 2000s, indicating the melting of subsurface and glacial ice in the basin. At Luquillo Experimental Forest in Puerto Rico, monitoring of mercury in precipitation revealed the highest recorded mercury wet deposition rates in the USA, an unexpected finding given the lack of point sources. At Panola Mountain, GA, long-term monitoring of soil- and groundwater revealed step shifts in chemical compositions in response to wet and drought cycles, causing a corresponding shift in stream chemistry. At Sleepers River, VT, WEBB funding has extended a long- term (since 1960) weekly snow water equivalent dataset which is a valuable integrating signal of regional climate trends. At Trout Lake, WI, long-term monitoring of lakes, ground-water levels, streamflow and subsurface water chemistry has generated a rich dataset for calibrating a watershed model, and allowed for efficient design of an automated procedure for sampling mercury during runoff events. The 17-plus years of monitoring at the WEBB watersheds provides a foundation for generating new scientific hypotheses, a basis for trend detection, and context for anomalous observations that often drive new research.