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Cayuga Lake

Cayuga Lake Watershed Management

Map of Cayuga Lake
Map of Cayuga Lake

Cayuga Lake is the second-largest of the Finger Lakes of central New York State, extending over 38 miles in length with an average width of 1.75 miles. It is one of the deepest of the Finger Lakes, with a maximum depth of 435 feet. The watershed draining into Cayuga Lake is the largest of the Finger Lakes, covering 785 square miles (approximately 500,000 acres) in parts of 6 counties (Cayuga, Tompkins, Seneca, Schuyler, Tioga and Cortland) and is home to 120,000 people. The watershed consists of agricultural, residential, industrial, and forested land. More than 140 streams flow into the lake along its 95 mile shoreline. The largest of these tributaries includes Salmon Creek, Fall Creek, Cayuga Inlet (including Cascadilla Creek and Six Mile Creek) and Taughannock Creek. Most of the lake is classified as being suitable for use as a drinking water supply (Class AA(T), A(T), or A); a small portion of the lake at the northern/outlet end is Class B(T). The lake has been the focus of a number of monitoring studies, including a significant NYSDEC monitoring effort entitled Water Quality Study of the Finger Lakes (Callinan, NYSDEC, 2002).

Water Quality Issues

Aerial view of Cayuga Lake
View of Cayuga Lake - Bill Hecht

Water quality in much of Cayuga Lake is good, and meets water quality standards for the protection of recreational uses. The one exception to this assessment is in the shallow south end of the lake where sediment and nutrient loads from point and nonpoint sources result in weed and algal growth that impair summer recreational uses (see South End Cayuga Lake below). Similarly current water quality standards for water supply use of the lake are also being met. However while NYSDEC considers the lake to have water quality suitable for use as a water supply, this use has been assessed as threatened. This assessment is based on the NYS DOH Source Water Assessment Program (SWAP) evaluation of the potential, rather than actual, impacts to water supply use. In the case of Cayuga Lake, the potential threats are due to the considerable agricultural activity and wastewater sources in the watershed. The classification of much of the lake as a Class AA water, which designates the lake as suitable for use as a drinking water source requiring a minimum of treatment, makes the lake more vulnerable to potential sources.

The most recent water quality assessment of Cayuga Lake (PDF, 91 KB) and its tributary waters was conducted in 2007 and can be found in the NYSDEC Waterbody Inventory Priority Waterbodies List (WI/PWL) Report for the Oswego River/Finger Lakes Basin. The WI/PWL assessments are intended to be updated every five years. The assessment for Cayuga Lake is somewhat overdue. However NYSDEC expects to issue an updated assessment that reflects the numerous Cayuga Lake activities outlined on this webpage in the near future.

South End Cayuga Lake
Aerial view of the south end of Cayuga Lake and Ithaca
South End Cayuga Lake - Bill Hecht

Water quality conditions in the South End of Cayuga Lake are much different than those in the rest of the lake. Whereas water quality in other parts of Cayuga Lake are generally good, the South End has experienced water quality problems dating back to the 1960s and has been assessed as impaired since 1998. Excessive algal and aquatic weed growth restricts the recreational use of this part of the lake. Since the 1960s, aquatic weeds, poor water clarity and other impacts have resulted in the continuous closure of Stewart Park Beach along the south end of the lake. More recently, increasing nutrient (phosphorus) levels and algal growth throughout the South End have dominated water quality issue.

There are a number of factors that contribute to these conditions. For one thing the South End is more shallow than the rest of the lake, generally less than 15 feet deep. In addition, the surrounding watershed in the South End is much more developed and more densely populated than other parts of the watershed. A number of larger tributaries (Fall Creek and Cayuga Inlet/Cascadilla Creek/Six Mile Creek) which carry significant nonpoint source pollution loads also empty into the South End. This portion of the lake also receives discharges from three large point sources: The Ithaca Area WWTP, Cayuga Heights WWTP, and the Cornell Lake Source Cooling Facility.

Invasive Species: Hydrilla

Hydrilla verticillatum (hydrilla, or water thyme) was discovered in Cayuga Inlet in August of 2011. Hydrilla has created significant ecological and economic problems throughout the country, and is particularly challenging to control due to abundant and persistent modes of reproduction, spread, and transport. The discovery of this highly invasive aquatic plant In Cayuga Inlet prompted immediate and forceful action, due to the great concern that this plant could move into Cayuga Lake and the Great Lakes ecosystem. A state and local Task Force was quickly established to delineate the hydrilla populations, identify appropriate management actions, and proceed with an aggressive strategy to eradicate the 166 acre infestation found in the Inlet and some connected waterways, using federal, state, and local resources. Key members of the Task Force include the City of Ithaca, the Tompkins County Soil and Water Conservation District and Department of Health, Racine-Johnson Aquatic Ecologists, NYSDEC, Canal Corps, and other local and state organizations. Recommendations of the Task Force led NYSDEC to conduct emergency rule-making to allow for a Hydrilla infestation treatment effort. Presently to the The Task Force is presently engaged in a multi-pronged eradication strategy, including the use of aquatic herbicides, hand removal, boat inspections, and extensive public education, outreach and monitoring. More information about hydrilla in Cayuga Inlet can be found on the Tompkins County CCE website (see link at right)

Watershed Management Actions

In 2001 a collaboration of local municipalities, community groups, interested citizens, and regional planning boards completed a management plan, the Cayuga Lake Watershed Restoration and Protection Plan (RPP) for the protection of the Cayuga Lake watershed. This effort coincided with the establishment of the Cayuga Watershed Intermunicipal Organization, a voluntary partnership of 31 villages, towns, cities and counties in the watershed working together to implement the RPP (see links at right). The main purpose of the RPP is to serve as a working guide for the public, elected officials, farmers, the business community, environmentalists and others to manage Cayuga Lake's valuable water resources.

South End Cayuga Lake TMDL

The DEC is continuing to work with local partners in the watershed to address current and potential sources of pollution and impairment to the South End of the lake. The department has already worked with area municipalities to reduce wastewater point sources and stormwater nonpoint sources of nutrients to the lake. Currently DEC is focused on developing and implementing a more comprehensive plan to address algal growth and other recreational impairments in the South End of the lake. The centerpiece of this approach is a Total Maximum Daily Load (TMDL) analysis that will look at all sources of nutrients to the lake and determine necessary reductions to restore uses in the South End. This analysis will rely on a number of components, including a whole lake monitoring and modeling effort to determine the fate and movement of nutrients in the lake, and a watershed model to evaluate nutrient loads from tributary watersheds. An update of the Cayuga Lake Restoration and Protection Plan is key to the implementation of the completed TMDL. Many of these components are incorporated into the final SPDES permit for the Cornell Lake Source Cooling Facility (PDF, 533 KB), issued in March 2013.

The final SPDES permit addresses water releases from Cornell University's Lake Source Cooling (LSC) facility. The permit includes a limit on the amount of phosphorous the Cornell LSC facility draws from the deeper lake and discharges to the shallower southern shelf. An interim limit holds Cornell's discharge of phosphorus at its current levels. Once the TMDL is completed, a final limit will be developed based on the results of the TMDL. The permit includes a requirement that Cornell optimize the use of the Lake Source Cooling while minimizing the volume of water that is drawn through the system and discharged to the southern shelf.

The permit also includes a requirement outlining Cornell's commitment to fund a study of Cayuga Lake to assist NYSDEC with the development of the TMDL for the South End of the Lake. Progress and developments regarding the Cayuga Lake Water Quality Modeling Study will be shared with the public through ongoing NYSDEC outreach. The TMDL process also will have an outreach component.

More information regarding the effort to address water quality issues and develop a TMDL for the South End of Cayuga Lake is outlined in an October 19, 2012, NYSDEC Press Release. Information regarding the final SPDES permit for the Cornell Lake Source Cooling Facility is outlined in a March 27, 2013, NYSDEC Press Release, and in the NYSDEC Response to Public Comments (PDF, 251 KB) on the Cornell LSC Facility Permit.

Continuing Outreach and Additional Information

NYSDEC will continue to maintain outreach efforts and information sharing with local stakeholders throughout the TMDL development process for the South End Cayuga Lake. These activities, which build on existing local stakeholder outreach efforts, include:

  • Regular DEC participation in the Tompkins County Water Resources Council (link in the right column) Monitoring Partnership monthly conference calls, providing a point of contact for local access to DEC for Q&A and updates.
  • Occasional public meetings scheduled around key project milestones and used to report to the larger public on progress of the study and TMDL development, as well as other Cayuga Lake Watershed issues and activities. The most recent of these public meetings was held on December 3, 2013. The NYSDEC presentation (PDF, 47 KB) from that meeting is available. DEC also participated in the Cayuga Watershed Network's April 5, 2014, Spring Conference. The NYSDEC presentation (PDF, 288 KB) from that meeting is also available. The next Public Meeting is scheduled for July 17 at 7 pm at The Space @ GreenStar at 700 W. Buffalo Street in Ithaca.
  • A Technical Advisory Committee (TAC) to provide independent advice and expertise to NYSDEC on scientific and technical aspects associated with lake water quality issues and the development of the TMDL for phosphorus in Cayuga Lake. The focus of the TAC is outlined in the TAC Charter (pdf, 138 kb) which was adopted when the TAC was initially formed. The TAC will meet periodically to review progress and identify issues for presentation and discussion at the Monthly calls and/or at the Public Meetings. To participate in the TAC meetings please contact a TAC member (see TAC Charter) or NYSDEC.
  • Additional stakeholder involvement will also be conducted to coincide with the actual TMDL development process, which will commence when the Cayuga Lake Water Quality Modeling Study is complete in 2016.

In addition, continue to check back here on the Cayuga Lake Watershed webpage, or contact us directly if you have other questions or need more information.

Subscribe to Finger Lakes News

Subscribe to Finger Lakes News and the DEC will send you occasional project information, updates and public meeting announcements about the Finger Lakes, including Cayuga Lake- right to your e-mail box. To subscribe to Finger Lakes News, first use this link to subscribe to GovDelivery by entering your e-mail address. Fill in and submit the requested information on the "New Subscriber" page. This will take you to the "Quick Subscription" page where you will see all the topics that you can receive email updates on from DEC. Scroll to the "Lakes and Rivers" category and check the box next to "Finger Lakes" You will receive a welcome email from DEC confirming your subscription(s).

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