WATER QUALITY OF OWASCO LAKE, CENTRAL NEW YORK: THE 2006 LAKE 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 lake survey included up to eleven lake sites distributed along the long axis of the lake and just offshore of major tributaries. These sites were sampled every two to three weeks from May through October, on both sunny/calm days and during or just after storm events. Total phosphates, a CTD cast (conductivity, temperature, depth and light transmission), horizontal and vertical plankton tows, total and dissolved organic matter, major ion analyses, and fecal bacteria counts were added to the lake survey.

Nutrient concentrations, secchi disk depths, total suspended solids, light transmission and conductivity data, and chlorophyll data indicated that Owasco's southern end was the most productive region of the lake. For example, the mean total phosphate concentration rose from mean open lake concentrations of 5 to 11 ug/L to as much as 600 ug/L at one of the southern sites. The impact was most noticeable during and just after severe storm events (e.g., 6/27), especially within a turbid plume that extended from the Owasco Inlet a few miles northward into the lake. The Inlet drains the southern and largest portion of the watershed (57% land surface). No noticeable impact was detected offshore of Dutch Hollow Creek, the second largest watershed (15% land surface). It suggests that remediation efforts should focus on the loading from the Owasco Inlet. Perhaps the former flood plain surrounding the channelized Inlet should be revitalized to absorb the flux of suspended sediments and nutrients during flood events before they flow into the lake.