Water Quality Trend Assessment of 21 Twin Cities Metropolitan Area Streams

The Saint Paul - Minneapolis metropolitan area is located at the confluence of three major rivers - the Minnesota, the Mississippi, and the Saint Croix. Multiple smaller rivers and tributary streams enter the major rivers within the metropolitan area, carrying a mix of urban and agricultural runoff, shallow groundwater, and wastewater treatment plant (WWTP) effluent. In 2014 Metropolitan Council Environmental Services (MCES) completed a comprehensive study of the water quality and flow of 21 tributary streams entering the major rivers within the metropolitan area.As part of the study, MCES used the R-based statistical package QWTREND to assess decades of monitoring data and to identify any long term changes in water quality, focusing on TSS (total suspended solids), TP (total phosphorus), nitrate, and chloride. Results indicate that of the 21 streams assessed, most exhibited a substantial improvement in water quality during 2008 to 2012 (17 streams showed decreasing TSS and TP concentrations and 16 had decreasing nitrate concentration); none of the streams had declining water quality for all three parameters. There was no identifiable spatial pattern for the streams with improving or declining water quality.Water quality improvements are likely the result of the multiple layers of water quality activities with the metropolitan area, including installation of structural practices, phosphorus removal from WWTP effluent, passage of multiple protective legislations, implementation of education programs, and creation of key funding mechanisms, including the Clean Water, Land, and Legacy Amendment.