Aleia Dumond Myles T. Moore Amy Story Dawn Shively Muruleedhara N. Byappanahalli Aaron Aunins David C. Lampe Rebecca Hammer-Lester 2026 <p>Eutrophication has been regularly documented in the Grand Calumet River and Indiana Harbor Canal in northwest Indiana. The area has undergone various remediation efforts since the development of a Remedial Action Plan for the area in response to a 1987 amendment to the Great Lakes Water Quality Agreement of 1978 between the United States and Canada and the designation of the Grand Calumet River Area of Concern by the U.S. Environmental Protection Agency. To address concerns of eutrophication and its effects, the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency and the Indiana Department of Environmental Management, collected data from the Grand Calumet River and Indiana Harbor Canal in 2021 and 2022 to document the effects of remediation and combined sewer overflow releases on water quality.</p><p>This study used continuous monitors to collect real time data for dissolved oxygen, water temperature, chlorophyll fluorescence, specific conductance, and pH. Discrete sample analysis included biological oxygen demand, chemical oxygen demand, nutrients, nitrogen and oxygen isotopes in nitrate, nitrogen isotopes in ammonia, hydrogen and oxygen isotopes in water, and identification of algal communities (cyanobacteria and eukaryotic algae) by metabarcoding.</p><p>Eutrophic conditions were found throughout the area. Isotopic results indicated the source of nitrate in samples was either from soil organic nitrogen or combined sewer overflows. Combined sewer overflows were shown to have considerable effects on the sites, and remediation status did not have a great effect. Algal community results identified several taxa capable of becoming nuisance species, including Microcystaceae (cyanobacteria) and Chrysophyceae, Cryptophyceae, and Bacillariophyceae (all eukaryotic algae). When sites with irregular flow patterns were excluded from datasets, minimum dissolved oxygen concentrations were often higher downstream from remediated sites than from unremediated sites. This study shows the potential for further and more targeted exploration into the unusual conditions found throughout the Grand Calumet River and Indiana Harbor Canal area.</p> application/pdf 10.3133/sir20265130 en U.S. Geological Survey Evaluation of a eutrophication Beneficial Use Impairment in the Grand Calumet River Area of Concern in northwest Indiana, 2021–22 reports