Modeling the water quality impacts of the separation of the Great Lakes and Mississippi River basins for invasive species control

In 1900, the Chicago Sanitary and Ship Canal (CSSC) was opened to reverse the flow of the Chicago River and divert wastewater away from Lake Michigan and toward the Mississippi River. This reversal has been a public health success, but the CSSC and other components of the Chicago Area Waterway System (CAWS) have become conduits for invasive species to move between the Great Lakes and Mississippi River basins. The Great Lakes and Mississippi River Interbasin Study evaluated methods to prevent the migration of invasive species between the basins. The DUFLOW model was adapted to simulate water quality in the CAWS. This model is used to simulate conditions in the CAWS for the No Project (NP), Lakefront Separation (LS), and Midsystem Separation (MS) alternatives. Three representative water years (wet year, dry year, and normal year) are considered to compare the dissolved oxygen (DO) results and pollutant loads to Lake Michigan for the alternatives. The LS alternative results in large increases in noncompliance with DO standards with increases greater than 1000 h for several locations. The MS alternative results in large increases in noncompliance with DO standards in the waterways made stagnant by the placement of barriers with the Calumet-Sag Channel experiencing increases greater than 1000 h for nearly all locations evaluated. The loads to Lake Michigan for the MS alternative are greatly increased compared to the NP alternative with even the dry year modeled yielding loads of nitrogen, phosphorus, and chloride, 5.7, 0.73, and 150 million kg, respectively.