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Effects of backpacker use, pack stock trail use, and pack stock grazing on water-quality indicators, including nutrients, E. coli, hormones, and pharmaceuticals, in Yosemite National Park, USA

Environmental Management

By:
, ORCID iD , , , and ORCID iD
https://doi.org/10.1007/s00267-017-0899-z

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Abstract

We investigated how visitor-use affects water quality in wilderness in Yosemite National Park. During the summers of 2012–2014, we collected and analyzed surface-water samples for water-quality indicators, including fecal indicator bacteria Escherichia coli, nutrients (nitrogen, phosphorus, carbon), suspended sediment concentration, pharmaceuticals, and hormones. Samples were collected upstream and downstream from different types of visitor use at weekly to biweekly intervals and during summer storms. We conducted a park-wide synoptic sampling campaign during summer 2014, and sampled upstream and downstream from meadows to evaluate the mitigating effect of meadows on water quality. At pack stock stream crossings, Escherichia coli concentrations were greater downstream from crossings than upstream (median downstream increase in Escherichia coli of three colony forming units 100 mL−1), with the greatest increases occurring during storms (median downstream increase in Escherichia coli of 32 CFU 100 mL−1). At backpacker use sites, hormones, and pharmaceuticals (e.g., insect repellent) were detected at downstream sites, and Escherichia coli concentrations were greater at downstream sites (median downstream increase in Escherichia coli of 1 CFU 100 mL−1). Differences in water quality downstream vs. upstream from meadows grazed by pack stock were not detectable for most water-quality indicators, however, Escherichia coli concentrations decreased downstream, suggesting entrapment and die-off of fecal indicator bacteria in meadows. Our results indicate that under current-use levels pack stock trail use and backpacker use are associated with detectable, but relatively minor, effects on water quality, which are most pronounced during storms.

Study Area

Additional publication details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Effects of backpacker use, pack stock trail use, and pack stock grazing on water-quality indicators, including nutrients, E. coli, hormones, and pharmaceuticals, in Yosemite National Park, USA
Series title:
Environmental Management
DOI:
10.1007/s00267-017-0899-z
Volume:
60
Issue:
3
Year Published:
2017
Language:
English
Publisher:
Springer
Contributing office(s):
Colorado Water Science Center
Description:
18 p.
First page:
526
Last page:
543
Country:
United States
State:
California
Other Geospatial:
Yosemite National Park