Data for: Long-Term Trends Show Improvements in Water Quality in the Chicago Metropolitan Region with Investment in Wastewater Infrastructure, Deep Tunnels, and Reservoirs
Compiled water quality data of the Chicago, Calumet, and Des Plaines River Systems from 1975 to 2018. Data were collected as part of the Metropolitan Water Reclamation District's Ambient Water Quality Monitoring program. A study was carried out to evaluate water quality trends from 1975 to 2012 and from 2013 to 2018 in the Chicago, Calumet, and Des Plaines River Systems in Cook County, Illinois, in order to investigate the outcome of practices carried out by the Metropolitan Water Reclamation District of Greater Chicago. Data from 41 monitoring locations were compiled and analyzed for 11 water quality parameters. The seasonal Kendall test was performed on each variable at each location to analyze for long-term monotonic trends. Wilcoxon Rank-Sum test was used to test for significant differences in water quality constituents between time periods to point to practices that changed water quality during the study period. For most sampling locations, long-term trend analyses showed significant downward trends for total organic carbon (TOC), total Kjeldahl nitrogen (TKN), ammonium nitrogen (NH4-N), total suspended solids (TSS), fecal coliform (FC), and sulfate and significant upward trends for dissolved oxygen (DO), chloride, and temperature. Total phosphorus (TP) concentrations increased downstream of the Stickney, Kirie, and Calumet WRPs from 1975 to 2012, but decreased downstream of the Kirie WRP and had no trends downstream of the Stickney and Calumet WRPs from 2013 to 2018. Improvements in TKN, NH4-N, TOC, TSS, FC, TP, and DO concentrations over four decades demonstrated the beneficial outcome from the expansion of secondary treatment systems at water reclamation plants, implementation of the Tunnel and Reservoir Plan System, instream and side-stream elevated pool aeration stations, and effluent disinfection. The study is described in the article entitled "Long-Term Trends Show Improvements in Water Quality in the Chicago Metropolitan Region with Investment in Wastewater Infrastructure, Deep Tunnels, and Reservoirs". Supporting Information for this manuscript is attached.