Water Quality Issues


Sediment is a significant water quality, habitat, and use impairment issue, particularly in the southern tributaries and southern Cayuga Lake. The southern basin of Cayuga Lake is included on the State’s Priority Waterbodies List (PWL); silt and sediment is listed as the primary pollutant. Six tributaries are included on the PWL with silt and sediment listed as the primary pollutant; the six tributaries include four southern streams (Cascadilla Creek, Fall Creek, Six Mile Creek, Cayuga Inlet), Yawger Creek, and Bolter tributary. Southern Cayuga Lake is also included on the 303(d) list, a national compendium of impaired waters requiring a watershed approach to restoration.

Sediment is a significant pollutant in many New York watersheds. It creates or contributes to a number of water quality problems both in streams and ultimately in the impoundments they feed. Excessive sediment concentrations in the water column can be harmful to aquatic life and will exacerbate the toxic effects of other pollutants. Suspended sediment in the water column can increase temperature. Sediment deposits within streams degrade habitat for macroinvertebrates and fish. Finally, and perhaps most importantly, sediment carries other types of contaminants into the aquatic system: nutrients, organic compounds including pesticides, and heavy metals.


Phosphorus is the limiting nutrient for algal growth in Cayuga Lake as it is for most inland lakes in the Northeast. Enrichment of lakes with phosphorus increases the level of plant and algal growth (primary productivity) and is associated with loss of water clarity. Recent monitoring data confirm that Cayuga Lake is mesotrophic, with moderate levels of primary productivity. However, the shallow areas at the northern and southern ends of the lake exhibit higher levels of phosphorus and productivity. NYSDEC considers both the northern and southern segments of Cayuga Lake as priority areas, indicating water quality concerns. Phosphorus sources include the two wastewater treatment plants discharging to the southern lake basin and runoff from residential and agricultural areas. Septic systems are considered by NYSDEC to be significant sources of phosphorus to the northern segment.

Fertilizers and Pesticides

Fertilizers and pesticides have been detected in both tributary streams and the lake. Recent data provide direct evidence of chemical loss from the landscape and transport to the lake. Almost half of the land in the Cayuga Lake watershed is in active agriculture, and this land use contributes nitrate-nitrogen and pesticides (most notably, herbicides used in corn cultivation) to the lake. Residential and commercial areas are also a potential source of pesticides and herbicides. Using analytical methods with low detection limits, scientists from USGS and NYSDEC have documented trace concentrations of pesticides in the streams and lake. Concentrations of fertilizers and pesticides in groundwater are not well documented.

The herbicides are present at levels far below ambient water quality standards or guidelines based on toxicology and risk assessment. No exceedances of standards or guidelines developed to protect human health and the environment have been detected. However, long-term effects of exposure to trace concentrations of many of these chemicals, singly or in combination, are unknown. The monitoring program has also detected breakdown products of several herbicides in the lake. Concentrations of the breakdown products can be higher than the concentrations of the original compounds. The long-term health effects of exposure to these breakdown products are not well documented. Even when imputs are reduced, contaminants tend to persist in Cayuga Lake, due to the 9-12 year cycle of water replacement.

Organic compounds

There is localized contamination of groundwater in the Cayuga Lake watershed. The public water supplies in the Towns of Union Springs and Aurelius have detectable concentrations of trichloroethylene (TCE), an organic compound widely used as an industrial solvent, and several TCE breakdown products. Investigations are underway to identify the source(s) of the contamination. Monitoring of private and public wells is also being conducted and water is supplied to affected residents. Groundwater in the Village of Jacksonville has been contaminated by petroleum.

Trace Elements

Limited monitoring has documented elevated concentrations of trace elements (heavy metals) in sediments of Fall Creek and nearshore areas of southern Cayuga Lake. Potential sources of these trace elements are industrial discharges, stormwater runoff, and/or atmospheric deposition. Adverse impacts of metals include toxicity to sediment organisms (such as aquatic insects and worms), and bioaccumulation within the food web. Extensive monitoring data from Cayuga Lake and the tributaries used for water supply document that concentrations of trace elements in water are low. Concentrations are consistently within limits developed to protect human health and the environment.


Monitoring for the potential presence of pathogens (disease causing microorganisms) is very limited in the Cayuga Lake watershed. Pathogens originate from untreated or inadequately treated human sewage and wild and domestic animal waste. More data are needed to determine whether the issue poses a threat to the desired uses of the water resources.

Exotic species

Because of its connections to the Great Lakes through the Seneca River, Cayuga Lake is vulnerable to invasion by nonindigenous species of plants and animals. Two recent invaders are a focus of special concern due to their potential to alter the food web. These organisms are the zebra mussel (Dreissena polymorpha) and a predatory cladoceran zooplankton (Cercopagis pengoi). The macrophyte Eurasian water milfoil (Myriophyllum spicatum) is another introduced species that has, until recently, been a nuisance in Cayuga Lake.

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