PRECIPITATION, NUTRIENT LOADING AND WATER QUALITY TRENDS IN THE FINGER LAKES OF NEW YORK

A five-year comparative limnological study of the eight largest Finger Lakes in central and western New York (Canandaigua, Cayuga, Honeoye, Keuka, Otisco, Owasco, Seneca, and Skaneateles Lakes) indicates variability in water quality between lakes, and variability from one year to the next within an individual lake. Because the rural landscape is dominated by agricultural and forested land, each watershed has slightly different land use activities, and previous stream analyses reveal a correlation between nutrient loading and rainfall intensities, we hypothesize that annual variations in rainfall are directly correlated to runoff and nutrient loading fluxes from agricultural non point-sources and thus rainfall influences water quality in the lakes. This study investigates the correlation between rainfall and water quality.

Surface and bottom water were collected from at least two deep-water sites in each lake on a monthly basis during the May to October field season. The water was analyzed for total suspended sediment (TSS), total phosphate (TP), soluble reactive phosphate (SRP), nitrates, dissolved silica, chlorophyll-a, pH, conductivity, alkalinity and major ions following standard limnological techniques. In addition, secchi disk depths, plankton tows and CTD profiles were collected at each site. The SeaBird SBE-25 CTD collected profiles of conductivity, temperature, depth, pH, photosynthetically active radiation (PAR), dissolved oxygen, fluorescence and turbidity. Annual water quality rankings were based on annual mean secchi disk depths, total suspended solids, dissolved and total phosphates, nitrates, and chlorophyll-concentrations. NASA’s Tropical Rainfall Measuring Mission provided monthly 27km x 27km raster-based rainfall data that were clipped to each watershed for annual rainfall intensities in each watershed.

The results indicate that while rainfall and the presumed nutrient loading to each lake is one driver that impacts water quality, additional variability exists within each lake, and across the region, not explained by rainfall alone. Future studies must analyze other water quality drivers and continued monitoring is needed to study long-term trends.