The Onondaga lake watershed covers 285 square miles located almost entirely within Onondaga County

Onondaga Lake Watershed

A watershed is an area from which water drains to a particular body of water. It's the area of land that catches rain and snow and drains or seeps into a marsh, stream, river, lake, or groundwater. Watersheds range in size from a few acres to large areas of the country. Onondaga Lake's watershed is located almost entirely within Onondaga County. The lake receives water from a land area, or drainage basin, of 285 square miles located almost entirely within Onondaga County.

Natural Tributaries

The major natural tributaries to the lake are Nine Mile Creek and Onondaga Creek which together account for about 70% of the total amount of water that flows into the lake each year. Other natural tributaries include Ley Creek, Harbor Brook, Saw Mill Creek and Bloody Brook.

Onondaga Lake Tributaries

Metro

Onondaga County's Metropolitan Syracuse Treatment Plant (Metro) is the third largest source of water to the lake making up 20% of the lake's annual inflow. This large proportion of treated wastewater is a unique feature of Onondaga Lake and a leading source of its continuing water quality problems. For more information see Pollutants and Sources: Phosphorus, Ammonia and Nitrite, and combined sewer overflows. During the summer, when the amount of water flowing into the lake from the natural tributaries is low, the discharge from Metro represents the single largest contribution of water to Onondaga Lake. ,

Lake Flushing

Metropolitan Syracuse Wastewater Treatment Plant (Metro) Metro is currently the lake's main phosphorus and ammonia contributor.

Tributaries to Onondaga Lake flush the lake (replacing old water with new water) rapidly compared to most other lakes. This happens approximately 4 times each year. Its rapid rate of flushing will benefit the cleanup of Onondaga Lake because the lake will respond quickly to reductions in pollution inputs.

Outflow

Water flows from Onondaga Lake to the Seneca River through a single outlet at its north end. The Seneca River combines with the Oneida River at Three Rivers Junction to form the Oswego River. The Oswego River then flows north to Lake Ontario approximately 40 miles downstream from the Onondaga Lake outlet.

Watershed Protection

Land use activities within the Onondaga Lake Watershed produce pollutants that flow through the lake's tributaries into Onondaga Lake. Cleaning up Onondaga Lake requires addressing pollution issues within the watershed, not just the lake itself. A Watershed Protection Approach is a strategy for effectively protecting and restoring aquatic ecosystems and protecting human health. This strategy has as its premise that many water quality and ecosystem problems are best solved at the watershed level rather than at the individual water body or discharger level.

Major features of a Watershed Protection Approach are:

• Targeting priority problems
• Promoting a high level of stakeholder involvement, integrated solutions that make use of the expertise and authority of multiple agencies
• Measuring success through monitoring and other data gathering.