WATER QUALITY OF OWASCO LAKE, CENTRAL NEW YORK: THE 2006 WATERSHED SURVEY

A 2005 limnological survey of Honeoye, Canandaigua, Keuka, Seneca, Cayuga, Owasco and Skaneateles Lakes, the seven central Finger Lakes of central New York revealed that Owasco Lake had the worst water quality (Halfman and Bush, 2006). The analysis ranked the water transparency (total suspended solids and secchi disk depths), chlorophyll, nutrient (dissolved phosphate, nitrate and silica), total coliform and E. coli bacteria data from surface and bottom water samples collected at two deep-water, mid-lake sites. This and our companion poster present the results from a more detailed May through October 2006 survey of both the lake and the watershed to determine the likely sources of the water quality impairment in Owasco Lake.

The 2006 watershed survey included seven stream sites that sampled the outflow of Dutch Hollow Creek and undertook a segment analysis of Owasco Inlet. These two streams cover 15 and 57% of the entire watershed, respectively. Specific site selection took into account probable nutrient sources like runoff from agricultural land and effluent from wastewater treatment facilities. These sites were sampled every two to three weeks from May through October, on both sunny/calm days and during or just after major storm events. Stream discharge, total phosphate and major ion analyses were added to the list of analyses in the stream survey.

Mean total phosphate (TP) fluxes, for example, revealed that Dutch Hollow Creek and the tributaries flowing into Owasco Inlet added up to 1 kg/day, probably from runoff of agricultural land and onsite systems. The mean flux increased by 4 kg/day between the two upstream sites that bracket the location of Groton's municipal wastewater treatment facility. The flux on individual sample dates increased significantly during or just after major runoff events due to increased flow and higher concentrations, except for the site just downstream of the wastewater treatment plant. The wastewater plant is currently undergoing renovations to include tertiary treatment to reduce nutrient loading by its effluent. However, the impact of Owasco Inlet is significant enough that the former floodplain surrounding the channelized stream downstream of Moravia should be revitalized to absorb the excess pollutants during flood events.