Assessing possible visitor-use impacts on water quality in Yosemite National Park, California

Environmental Monitoring and Assessment
By: , and 



There is concern that visitor-use associated activities, such as bathing, dish washing, wastewater production, and stock animal use near lakes and streams, could cause degradation of water quality in Yosemite National Park. A study was conducted during 2004–2007 to assess patterns in nutrient and Escherichia coli (E. coli) concentrations in the Merced and Tuolumne Rivers and characterize natural background concentrations of nutrients in the park. Results indicated that nutrient and E. coli concentrations were low, even compared to other undeveloped sites in the United States. A multiple linear regression approach was used to model natural background concentrations of nutrients, with basin characteristics as explanatory variables. Modeled nitrogen concentrations increased with elevation, and modeled phosphorus concentrations increased with basin size. Observed concentrations (±uncertainty) were compared to modeled concentrations (±uncertainty) to identify sites that might be impacted by point sources of nutrients, as indicated by large model residuals. Statistically significant differences in observed and modeled concentrations were observed at only a few locations, indicating that most sites were representative of natural background conditions. The empirical modeling approach used in this study can be used to estimate natural background conditions at any point along a study reach in areas minimally impacted by development, and may be useful for setting water-quality standards in many national parks.
Publication type Article
Publication Subtype Journal Article
Title Assessing possible visitor-use impacts on water quality in Yosemite National Park, California
Series title Environmental Monitoring and Assessment
DOI 10.1007/s10661-011-1915-z
Volume 183
Issue 1
Year Published 2011
Language English
Publisher Springer
Publisher location Amsterdam, Netherlands
Contributing office(s) Colorado Water Science Center, National Water Quality Laboratory
Description 19 p.
First page 197
Last page 215
Time Range Start 2004-01-01
Time Range End 2007-12-31
Country United States
State California
Other Geospatial Yosemite National Park
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