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Metropolitan Water Reclamation District of Greater Chicago


The Little Calumet River Watershed drains an area of 264.6 square miles in southeastern Cook County, and includes 45 communities either wholly or partly within the watershed. Portions of the watershed extend into northeast Will County and the northwest portion of Lake County, Indiana. The watershed is bounded to the north by Blue Island, on the south by Monee, on the west by Tinley Park, and on the east by Gary, Indiana.

The Little Calumet River originates in Gary, Indiana and flows northwest along the northern boundary of the watershed.  It bends northeast at Blue Island, Illinois and continues flowing northeast until its confluence with the Calumet-Sag Channel. Flow continues westward in the Calumet-Sag Channel to the Chicago Sanitary and Ship Canal, tributary to the Des Plaines River, from the Des Plaines River to the Illinois River, and from the Illinois River to the Mississippi River basin. Under high flow conditions, the Little Calumet River flows to Lake Michigan through the O’Brien Locks and Dam.

Stormwater infrastructure

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.

Regional reservoirs

In conjunction with local municipalities, the MWRD operates five regional reservoirs located in this watershed, providing 3,019 acre-feet (983.7 million gallons) of stormwater detention. Click on the accordion below to see a list of these reservoirs.

  • Tinley Park Reservoir - Tinley Park, IL - 616 acre-feet
  • Calumet Union Reservoir - Hazel Crest, IL - 500 acre-feet
  • Edward C. Howell Reservoir - Markham, IL - 589 acre-feet
  • Deer Creek Reservoir - Ford Heights, IL 238 acre-feet
  • Dr. Mary Woodland Reservoir - Lynwood, IL - 1076 acre-feet

Additional infrastructure

The following MWRD infrastructure are also located within this watershed. Below, you can download a map of these facilities located throughout Cook County.

MWRD Facilities and Infrastructure Map

Tunnel and Reservoir Plan

This watershed is served by the Thornton composite reservoir, located in the Village of South Holland, and the Calumet tunnel system. The reservoir was constructed as part of the Tunnel and Reservoir Plan (TARP) and can hold 7.9 billion gallons of water. It benefits 14 communities throughout the southern suburbs and the south side of Chicago, protecting over 180,000 structures and preventing combined sewer overflows to the Calumet River and Calumet-Sag Channel.

Wastewater treatment

Wastewater in this watershed is treated by the Calumet Water Reclamation Plant, which can treat up to 430 million gallons of wastewater per day. It serves over 1 million people in 49 communities and covers 300 square miles in southern Cook County. 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 waterways

This watershed flows from the Little Calumet River, towards the Calumet-Sag Channel to the Chicago Sanitary and Ship Canal. 

These rivers and canals 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 and at the southernmost point of the CAWS, the Lockport Powerhouse.

The MWRD also monitors the water quality of these waterways and has installed Sidestream Elevated Pool Aeration (SEPA) stations along the CAWS to improve the water quality and support natural habitats for fish and other aquatic life.

Watershed Planning Council meetings


Little Calumet River WPC

South Suburban Mayors & Managers Association
708-206-1155 |

Little Calumet watershed council members

Blue Island
Calumet City  
Calumet Park  
Chicago Heights  
Country Club Hills  
East Hazel Crest  
Ford Heights  
Hazel Crest
Oak Forest  
Olympia Fields  
Orland Hills  
Park Forest  
Richton Park  
Sauk Village
South Chicago Heights  
South Holland   
Tinley Park  
University Park  

Opted out of WPC membership to this watershed
Orland Park  
Bloom Township  
Bremen Township  
Calumet Township  
Orland Township  
Rich Township  
Thornton Township  
Unincorporated Cook County