SPATIAL AND TEMPORAL TRENDS IN MAJOR ION CONCENTRATIONS FROM THE FINGER LAKES, NY

The eleven Finger Lakes, located in central and western New York State, occupy a 5,000 km², 14-county region. They are an important natural and economic resource for the local area, as they provide, on average, 200 million gallons of fresh water per day for 1.2 million people in the region, and the water-based recreation and a renowned and rapidly expanding winery annually attracts 22 million tourists to the region. These lakes are also an ideal natural laboratory for hydrogeochemical studies because each watershed has different land use, bedrock and physiographic characteristics.

Monthly water samples from Canadice, Honeoye, Canandaigua, Keuka, Owasco, Skaneateles, and Otisco lakes through the 2004 fall and winter seasons combined with annual samples collected previously over the past 4 years, were analyzed by ion chromatograph for chloride, sulfate, fluoride, sodium, potassium, magnesium and calcium, and were used to construct a preliminary hydrogeochemical budget for the major ions. This Finger Lake data set expands on earlier work that focused on Seneca Lake and its watershed where weekly samples were collected from four lake sites and up to eighteen streams within the Seneca Lake watershed, the largest Finger Lake.

The Seneca Lake research by previous undergraduates at HWS indicates that the major ion concentrations are constant over time and location, suggesting that each ion is at equilibrium in the lake. Stream ion concentrations, however, change slightly over time, between streams, and between the streams and the lake, reflecting seasonal variability and bedrock characteristics.

Spatially, chloride, sodium, and sulfate concentrations are larger in Seneca, and to a smaller extent in Cayuga, than the other Finger Lakes. This trend is consistent with a groundwater source by leaching Silurian evaporites below these deepest Finger Lakes as hypothesized for chloride by earlier researchers. Owasco, Skaneateles and Otisco reveal lower potassium concentrations, whereas Canadice and Honeoye reveal lower calcium and magnesium concentrations than the other Finger Lakes. Both trends suggest a bedrock control on the fluvial ion flux to each lake. Temporally, only chloride and sodium concentration have increased slightly over time in most lakes, a trend that might reflect de-icing practices.