Water quality monitoring in the headwaters region of the Raritan River Basin in Central New Jersey

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Noah Motz and Sara Desjadon, Science & Engineering, Raritan Valley Community College, Branchburg, NJ, Emilie K Stander, Department of Science & Engineering, Raritan Valley Community College, Branchburg, NJ, Maria Dowling and Kristi Macdonald, Raritan Headwaters Association, Bedminster, NJ

Background/Question/Methods
Water quality in the mixed-use, headwaters region of the Raritan River Basin in Central New Jersey is affected by a transition from agricultural land use/land cover to sub/urban LU/LC. Bi-weekly monitoring of 13 stream locations within the headwaters region of the Raritan River Basin has been conducted since May 2018. Qualitative assessments previously performed by citizen scientists indicated that some sites were impaired while others exhibited high quality. Quantitative water quality data were collected to further evaluate these streams. Water quality parameters measured include nitrate, orthophosphate, chloride, and E. coli concentrations along with temperature and pH. Water samples are collected in pre-rinsed sterile Nalgene bottles. E. coli concentrations are found by filtering the sample through membrane filters and incubating with m-ColiBlue24 media at 35°C for 24 hours. Colonies are counted manually using the EPA Approved Method 10029. The water samples are filtered and analyzed for nitrate concentrations by colorimetric analysis using a flow-injection analyzer. Orthophosphate is measured using a LaMotte kit, and chloride is measured using an ion-selective electrode. GIS analysis was used to categorize the percent land cover at each site at the HUC14 scale into six categories: agriculture, barren, forest, urban, water and wetland. Land use data were regressed against water quality measurements to find the most influential factors.
Results/Conclusions
Over the course of the study, nitrate concentrations ranged from 0.029 to 6.7 ppm, with a mean value of 1.24 ppm. The observed E. coli concentrations ranged from 0 to 36,067 cfu/100mL, with a mean value of 773 cfu/100mL. The nitrate concentrations were highest in the winter with a mean value of 1.78 ppm, while the highest E. coli concentrations occurred in the fall with a mean value of 1681 cfu/100mL. Two large storm events in the past two fall seasons may have skewed the results for E. coli concentrations. The most influential land use category for E. coli concentrations was percent barren land, with an r2 of 0.23, and the most significant land use category for nitrate concentrations was percent agricultural land, with an r2 of 0.14. This result is likely skewed by one site that had the largest percent agricultural land and also the largest variation in nitrate concentrations. For both E. coli and nitrate concentrations, the only season in which the most significant land use category changes is the summer, when percent water and percent wetland are the most significant factors respectively.