Chicago Locks: Managing Floods and Water Quality Amid Heavy Rains
The Chicago locks, which manage the flow between the Chicago River system and Lake Michigan, are occasionally opened during extreme rain events to prevent flooding in the city’s downtown area, known as the Loop. This action, however, comes with significant consequences, as it results in the discharge of untreated sewage and stormwater into Lake Michigan, the city’s primary source of drinking water. Since 1985, this measure has been used approximately 50 times, most recently on July 2, 2023, following a storm that brought eight inches of rain to parts of the city. The decision to open the locks is made by the Metropolitan Water Reclamation District (MWRD) as a last resort to prevent catastrophic flooding. Despite public misconceptions, opening the locks does not alleviate basement flooding, as the water must travel a long distance through the sewer system before reaching the lakefront. (Source time: 2026-09-14T12:15:00-04:00)
