Seneca Lake is part of the network of lakes, canals and waterways that comprise the Oswego River Basin. The Oswego River Basin drains water from an area of 5,122 square miles, towards Lake Ontario.  

Water Flow

Water can flow into Seneca Lake faster than it can flow out. The downstream area is relatively flat and the outflow is regulated; therefore the lake takes longer to drain than to fill.  All of the water in Seneca Lake leaves near Geneva through the Cayuga-Seneca Canal. The brown arrows on the map below show the direction of watershed flow.  The purple arrows show the direction of the canal flow.  

Seneca Lake's discharge is managed by Gravity Renewables, through its hydroelectric power plants at Waterloo and at Seneca Falls.

The power company’s objective is to generate clean electric power and stay within the compliance requirements of the Federal Energy Regulatory Authority (FERC). In addition, the New York State Canal Corporation operates a small bypass gate and locks in this region.  The only outlet for Seneca Lake water is the Cayuga-Seneca Canal. The discharge flow rate is measured by a river gage at Seneca Falls, near the Rt-89 bridge before the water flows to Cayuga Lake. From there the discharge is managed by the NYS Canal Corporation (NYSCC). NYSCC’s responsibilities are focused on safe navigation through the canals of New York State.

Ideally, when a high water event occurs, each lake will retain as much water as possible to balance the overall outflow to Lake Ontario at Oswego. The ideal is avoiding significant damage or navigational hazard anywhere throughout the Oswego River Basin.

The water level of Seneca Lake is only partially determined by the physiological features found within the Oswego River Basin. The Seneca Lake Rule Curve, developed in the mid-70s by Gordon Hansen of the Navy’s Underwater System Center at Dresden, defines the lake’s highest tolerable level, lowest tolerable level.  Rule curves establish a target range for the water level, helping to prevent severe flooding or severe drought conditions, ensuring a stable, reliable water supply throughout low water summer months and protecting damage to delicate natural resources during high water months.  

The rule curve establishes a Summer Target that is typically reached by mid-March and  Winter Target level which is typically reach by mid-December.

Each lake has a rules curve to guide its water level management. But there is only voluntary coordination among the lakes to manage both lake level and water discharge from each lake. Since each management unit has different objectives there are occasional conflicts.

Lake Depths and Elevations