SENECA LAKE WATERSHED: AN IDEAL HYDROGEOCHEMICAL NATURAL LABORATORY

Seneca Lake is the largest of the Finger Lakes in central New York and is our focus for many undergraduate opportunities at Hobart and William Smith Colleges. The lake is approximately 55 km long, 3 km wide and has a maximum depth in excess of 200 meters. The lake is fed by 16 creeks and 13 drainages (collection of smaller tributaries) that drain a variety of surface areas (a few to 100 sq. km), landuse (agricultural, forested to urban landscapes), bedrock (Paleozoic carbonates, shales and coarser grained clastics), soils and other features. This variety provides an ideal natural laboratory for hydrogeochemical and limnological studies by our undergraduates and for our high school outreach programs. The data set is also key to assess water quality and other socio-economic-environmental variables as the lake provides drinking water to approximately 100,000 people and stimulates the billion dollar tourism/winery trade.

We routinely monitor 7 of the subwatersheds for discharge and recently automated the task with the HWS Data Logger. The logger is a small, inexpensive, microprocessor-based device that detects, digitizes, and stores voltage output from a sensor as an 8-bit value. The lake and streams are also analyzed for selected major ions (Cl, Ca, Mg, Alk), and nutrients (P, N, Si) to facilitate biogeochemical investigations. For example, mass balance calculations dictate chloride inputs through the sediments by the percolation of saline groundwater originating from the Paleozoic evaporites below the lake. Calcium concentrations in the streams parallel carbonate bedrock and agricultural landuse abundance. Calcium is removed from the lake by precipitation of an authigenic and biogenic (zebra mussels) carbonates. Atrazine (herbicide) and nitrate concentrations reflect runoff from agricultural areas and the later from older wastewater treatment facilities as well.