Effects of a rainfall event on water quality parameters in two local waterways
Location
Golden Eagles
Start Date
2-5-2025 9:40 AM
Department
Environmental Science
Abstract
Rainfall can affect water quality parameters by diluting, mixing and transporting materials in local waterways, and these effects are expected to vary depending on the amount of recent precipitation. The objective of this study is to compare the differences in four water quality parameters before and after a rainfall event. We sampled at two sites, the North Shore Channel below O’Brien (Channel) and the Upper North Branch Chicago River (River). Water quality parameters of the Channel are strongly influenced by the O’Brien Wastewater Reclamation Plant (O’Brien), which discharges an average of 230 million gallons of wastewater per day. Water quality in the River is influenced by runoff from a large area with varied land use. We sampled on September 21st where there was no rain for a month, and September 23rd one day after a rainfall event. We sampled seven sites along the River and three along the Channel. We used a multiprobe to measure conductivity and nitrate and chloride concentrations, and colorimetry to measure phosphate concentrations of the samples. We compared values of the two waterways on the two dates using t-tests. Under low flow conditions, conductivity, nitrate, and chloride were all significantly higher in the River than the Channel, while phosphate was higher in the Channel. After rainfall, conductivity decreased in both the River and Channel; nitrate and chloride concentrations decreased in the River but were unchanged in the Channel; and phosphate decreased in the Channel but was unchanged in the River. Higher levels of conductivity, nitrate, and chloride in the River suggest that water quality was poorer in the River than in the Channel. However, the higher levels of phosphate in the Channel, that come from the discharged treated wastewater from O’Brien, are of concern, as they could lead to eutrophication. Phosphate, conductivity, nitrate, and chloride levels decreased, showing rainfall was a variable in water quality parameter measurements. This study highlights the importance of assessing water quality over time as a single sample may not be representative.
Faculty Sponsor
John Kasmer
Effects of a rainfall event on water quality parameters in two local waterways
Golden Eagles
Rainfall can affect water quality parameters by diluting, mixing and transporting materials in local waterways, and these effects are expected to vary depending on the amount of recent precipitation. The objective of this study is to compare the differences in four water quality parameters before and after a rainfall event. We sampled at two sites, the North Shore Channel below O’Brien (Channel) and the Upper North Branch Chicago River (River). Water quality parameters of the Channel are strongly influenced by the O’Brien Wastewater Reclamation Plant (O’Brien), which discharges an average of 230 million gallons of wastewater per day. Water quality in the River is influenced by runoff from a large area with varied land use. We sampled on September 21st where there was no rain for a month, and September 23rd one day after a rainfall event. We sampled seven sites along the River and three along the Channel. We used a multiprobe to measure conductivity and nitrate and chloride concentrations, and colorimetry to measure phosphate concentrations of the samples. We compared values of the two waterways on the two dates using t-tests. Under low flow conditions, conductivity, nitrate, and chloride were all significantly higher in the River than the Channel, while phosphate was higher in the Channel. After rainfall, conductivity decreased in both the River and Channel; nitrate and chloride concentrations decreased in the River but were unchanged in the Channel; and phosphate decreased in the Channel but was unchanged in the River. Higher levels of conductivity, nitrate, and chloride in the River suggest that water quality was poorer in the River than in the Channel. However, the higher levels of phosphate in the Channel, that come from the discharged treated wastewater from O’Brien, are of concern, as they could lead to eutrophication. Phosphate, conductivity, nitrate, and chloride levels decreased, showing rainfall was a variable in water quality parameter measurements. This study highlights the importance of assessing water quality over time as a single sample may not be representative.