North Branch of the Chicago River Watershed
The North Branch of the Chicago River (NBCR) and Lake Michigan (LM) watersheds are located in northeastern Cook County and drain an area of over 120 square miles that includes 20 communities. The headwaters of the three major tributaries, the Skokie River, the Middle Fork, and the West Fork, are located in Lake County, IL. These tributaries flow south and, along with the North Shore Channel, discharge into and/or combine to form the NBCR. The downstream end of the NBCR is at the confluence with the Chicago River and South Branch of the Chicago River in downtown Chicago.
The Lake Michigan watershed within Cook County is located along the west coast of LM and extends west to the ridge along Green Bay Road. The LM watershed consists of seven ravines which drain east into Lake Michigan. The boundaries of these two watersheds were analyzed for the purposes of MWRD's stormwater management program.
Stormwater capital improvements
The MWRD has more than 240 active and complete stormwater projects throughout Cook County. These improvements include regional and local stormwater projects, green infrastructure, Space to Grow, and voluntary flood-prone property acquisitions. To see what projects are active and complete in your watershed, see the map below.
In conjunction with local municipalities, the MWRD operates five regional reservoirs located in this watershed, providing 2,765 acre-feet (900 million gallons) of stormwater detention.
- Deerfield Reservoir - Deerfield, IL - 575 acre-feet
- Glenview (Techny C) Reservoir - Glenview, IL - 1,040 acre-feet
- Middle Fork Reservoir - Northbrook, IL - 600 acre-feet
- Northbrook (Techny A) Reservoir - Northbrook, IL - 300 acre-feet
- Techny (Techny B) Reservoir - Northbrook, IL - 250 acre-feet
The following MWRD infrastructure are also located within this watershed. Below, you can download a map of these facilities located throughout Cook County.
Tunnel and Reservoir Plan
This watershed is served by the Mainstream Tunnel System and McCook Reservoir, which were constructed under the Tunnel and Reservoir Plan (TARP). The McCook Reservoir currently holds up to 3.5 billion gallons of water and will be expanded by 2029 to hold 10 billion gallons. The tunnels and reservoir were constructed as part of the Tunnel and Reservoir Plan (TARP).
This watershed is primarily served by the O'brien Water Reclamation Facility, which can treat up to 450 million gallons of wastewater per day. To learn more about wastewater treatment and this facility, please visit the wastewater treatment webpage. We also offer both virtual or in-person tours of our facilities.
Chicago Area Waterways
The North Branch of the Chicago River is the primary receiving waterway for this watershed. It connects with the Skokie River, Middle Fork, and West Fork, along with the North Shore Channel and flows to the confluence with Chicago River and South Branch of the Chicago River in downtown Chicago.
The NBCR and North Shore Channel make up a part of the Chicago Area Waterway System (CAWS). The CAWS provides drainage for much of the Chicago region and connects the Great Lakes with the Gulf of Mexico. The MWRD controls the flow and water level in the CAWS using control structures to both prevent discharges into Lake Michigan and reduce the risk of overbank flooding. These structures are located along Lake Michigan, such as at Wilmette Pumping Station, and at the southernmost point of the CAWS, the Lockport Powerhouse.
The MWRD also monitors the water quality of these waterways. In this watershed, two Sidestream Elevated Pool Aeration (SEPA) stations were installed along the CAWS to improve the water quality and support natural habitats for fish and other aquatic life.