Seneca Lake was carved out of bedrock over 10,000 years ago by glaciers, it is the deepest freshwater lake east of the Mississippi River outside of the Great Lakes. The lake’s shoreline is found within Seneca, Ontario, Yates and Schuyler Counties.

Interesting Facts

38 miles long

3.2 miles at greatest width

1.9 miles wide on average

633 feet deep, at maximum

66.3 square miles or about 42,400 acres

4.2 Trillion gallons of water

75 miles of shoreline

11 municipalities rely on the lake for public water systems

100,000 people rely on Seneca Lake as their primary water source


Seneca Lake is changing…

PURE WATERS Stream Monitoring data shows:

Phosphorus is elevated, particularly Reeder Creek, and all streams have elevated phosphorus levels in high flow conditions.

E.Coli (bacteria) is elevated in streams flowing into the lake and streams are contaminated with animal and/or human waste.

Erosion is a problem: plumes of sediment entering the lake from stream runoff, especially during high flows – suspended sediments reduce water clarity and are source of excessive nutrients.

Upstream inputs from wastewater treatment outfalls, septic systems, agricultural runoff (manure, fertilizers) have adverse impacts on the water quality downstream.

Caynobacteria Blooms or CyanoHABs are becoming more prevalent.