Seneca Lake is the largest of the glacial Finger Lakes of the U.S. state of New York, and the deepest glacial lake entirely within the state. It is promoted as being the lake trout capital of the world, and is host of the National Lake Trout Derby. Because of its depth and relative ease of access, the US Navy uses Seneca Lake to perform test and evaluation of equipment ranging from single element transducers to complex sonar arrays and systems.
The lake takes its name from the Seneca nation of Native Americans. At the north end of Seneca Lake is the city of Geneva, New York, home of Hobart and William Smith Colleges and the New York State Agricultural Experiment Station, a division of Cornell University. At the south end of the lake is the village of Watkins Glen, New York, famed for auto racing (hosting Watkins Glen International racetrack) and waterfalls.
Due to Seneca Lake's unique macroclimate it is home to over 50 wineries, many of them farm wineries and is the location of the Seneca Lake AVA. (See Seneca Lake wine trail).
At long, it is the second longest of the Finger Lakes and has the largest volume, estimated at , roughly half of the water in all the Finger Lakes. It has an average depth of , a maximum depth of , and a surface area of .
For comparison, Scotland's famous Loch Ness is long, wide, has a surface area of , an average depth of , a maximum depth of , and total volume of of water.
Seneca's two main inlets are Catharine Creek at the southern end and the Keuka Lake Outlet. Seneca Lake lets out into the Seneca River/ Cayuga-Seneca Canal, which joins Seneca and Cayuga Lakes at their northern ends.
It is fed by underground springs and replenished at a rate of 328,000 gallons (1240 m3) per minute. These springs keep the water moving in a circular motion, giving it little chance to freeze over. Because of Seneca Lake's great depth its temperature remains a near-constant . In summer the top warms to .