Feb 22, 2017

Cayuga Lake, Watershed Water Quality Threatened

Department of Environmental Conservation monitors TMDLs

cayuga lake, watershed, drinking water, new york

According to the New York state Department of Environmental Conservation (DEC), the water quality in the shallow end of Cayuga Lake has sediment and nutrient loads, including phosphorus, from various sources that result in weed and algae growth. DEC said current water quality standards for water supply use of the lake are being met, but this use is considered as “threatened.”

The lake and watershed have been the focus of ongoing monitoring and study by a number of groups. The Cayuga Lake Modeling Project highlights this monitoring.

In December, Cornell University submitted the Cayuga Lake water quality model it has been developing to the DEC. The model was created to support the development of a Total Maximum Daily Load (TMDL) plan to address water quality impairment on the south end of the lake.

The DEC is now evaluating the model for use in testing different water quality scenarios to be used in the TMDL plan. A draft TMDL plan for reducing phosphorus in Cayuga Lake is expected to be available for public comment this spring.

The submission of the model was the last major commitment included in the State Pollution Discharge Elimination System discharge permit for Cornell’s Lake Source Cooling Facility at the south end of the lake in Ithaca.

Other completed requirements include a preliminary discharge outfall redesign study, a study of the LSC facility intake and regular best management practices, and optimization plan reports.

The DEC documentation on Cayuga Lake states that the potential threats to the lake as a drinking water source are agricultural activity, wastewater treatment plants and other sources of nutrients in the watershed.

DEC officials say that water quality conditions in the south end are much different than the rest of the lake. The south end has experienced problems dating back to the 1960s and has been declared “impaired” since 1998. The growth of aquatic plants, problems with water clarity and other impacts have resulted in the continuous closure of Stewart Park beach in Ithaca on the south end. More recently, increased phosphorus levels have resulted in algae and weed growth in the south end, becoming the dominant water quality issue.

Contributing to the problem is that the south end is shallower than the rest of the lake, generally less than 15 ft deep. In addition, the surrounding watershed is much more developed and densely populated than other parts of the watershed. The south end also has large tributaries, which carry significant non-point source pollution loads into the south end of the lake.

The south end also receives discharges from three large point sources, the Ithaca Area Wastewater Treatment Plant, Cayuga Heights Wastewater Treatment Plant and the Cornell Lake Source Cooling Facility.