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Analyses (n = 535) of chloride (Cl-), bromide (Br-), nitrate as nitrogen (NO3-N), sodium (Na+), calcium (Ca2+), and potassium (K+) in stream water, tile-drain water, and groundwater were conducted in an urban-agricultural watershed (10% urban/impervious, 87% agriculture) to explore potential differences in the signature of Cl- originating from an urban source as compared to an agricultural source. Water samples were collected on a weekly interval from February 2018 to February 2019 at three station along the stream and from tile drains and wells. Nearly all surface water and tile water samples had Cl- concentrations above the calculated background threshold of 18 mg/l. Mann-Whitney U test revealed ratios of Cl- to Br- (p = 0.045), NO3-N (p < 0.0001), Ca2+ (p < 0.0001), and Na+ (p < 0.0001) to be statistically significantly different between urban and agricultural waters. Cl- ratios indicate that road salt is the dominant source of Cl- in the watershed, while potassium chloride fertilizer is an important secondary source. This study demonstrated that while deicing in watersheds where urban land use is minimal can have a profound impact on Cl- dynamics, agricultural practices should not be ignored.

2018-2019 Supporting_chemical_and_feild_data_Evergreen_lake_watershed.csv (65 kB)
Supporting Dataset described in Metadata