Onondaga Lake Watershed
Onondaga Lake is 4.6 miles long and 1 mile wide. Its average depth is 35 feet, and its maximum depth is 63 feet. It has a drainage basin of 285 square miles, according to 2004 figures of the U.S. Geological Survey, covering nearly all of the City of Syracuse and many of its suburbs east and west of the lake.
The major natural tributaries to the lake are Nine Mile Creek and Onondaga Creek. Together they account for 70% of the total amount of water that flows into the lake each year. The Metropolitan Syracuse Sewage Treatment Plant contributes 20% of the lake's annual inflow. Other tributaries are Ley Creek, Bloody Brook, and Harbor Brook. Minor tributaries include Sawmill Creek, Tributary 5A, and the East Flume.
Water leaves the lake through a single outlet at the lake's north end. This outlet flows to the Seneca River and ultimately reaches Lake Ontario.
