WHAT HAPPENED TO OUR LAKE? NUTRIENT LOADING IN OWASCO LAKE AND ITS WATERSHED

Owasco Lake is one of the 11 Finger Lakes of central New York. It is a source of Class AA drinking water for over 58,000 people, as well as a major recreational resource. After winning Best Tasting Drinking Water in 1997, water quality has declined in the lake. Halfman and Bush (2006) stated that Owasco Lake had the worst water quality of the 7 central Finger Lakes studied as well as poorest water quality protection legislation and/or enforcement. We present the results of a two-year study to track the changes in and nutrient sources to the lake, and outline potential remediation efforts. Biweekly sampling from May to October in 2006 and 2007, collected lake surface water at 11 sites and bottom water at 2 sites distributed along the long axis of the lake. At each site a CTD profile was collected, secchi disk, temperature, conductivity, pH, dissolved oxygen, and alkalinity were measured, and water collected for subsequent major ion, total suspended solid, total and dissolved phosphate, nitrate, dissolved silica, and chlorophyll analyses back in the laboratory. The 2006 results indicated that the southern end of the lake was much more productive, thus had worse water quality than the rest of the lake. Biweekly sampling of 7 streams during May-Oct in both years including a 4-site segment analysis of the Owasco Inlet investigated potential nutrient sources to the lake. The Owasco Inlet provides 55% of the surface water to the lake, and enters at the southern end. The remaining water enters from Dutch Hollow Creek (20%), Veness and Sucker Brooks (15%), and other minor tributaries (10%). In 2006, higher concentrations of nutrients were detected in the Owasco Inlet than the other tributaries. The segment analysis revealed nutrient sources from a waste treatment plant, and other agricultural and onsite septic sources. Deeper secchi disk depths, larger salinities, and smaller nutrient concentrations were detected throughout the lake in 2007 than 2006. Nutrient fluxes decreased from 2006 to 2007 in the streams as well. The change may be due to smaller amounts of rain in 2007, which decreased runoff of these nutrients from the watershed. The 2006 to 2007 improvement in water quality suggests that decreasing nutrient sources to the streams will allow for future water quality improvement during normal rain years.