'Escherichia Coli' in the Santa Cruz River in Tumacácori National Historical Park, Arizona [open pdf - 17MB]
From the Document: "At Tumacácori National Historical Park in southern Arizona, resource managers are concerned about microbial pathogens in the Santa Cruz River that could pose a serious health risk to employees and visitors. The U.S. Geological Survey recently completed a comprehensive 3-year study of water quality in the Santa Cruz River watershed that investigated the possible sources of microbial contamination and how it relates to the amount of water and suspended sediment in the river. The results of this study help water managers and park administration better address this contamination and issue warnings to the public when the water is unsafe."
Fact Sheet 2019-3065
U.S. Geological Survey: http://www.usgs.gov/