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

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), with the greatest increases occurring during storms (median downstream increase in Escherichia coli of 32 CFU 100 mL). 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). 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.

Bioactive contaminants of emerging concern in National Park waters of the northern Colorado Plateau, USA

“…To better understand the exposure, sources, and potential risk of CECs in the United States national parks, the National Park Service (NPS), U.S. Environmental Protection Agency (EPA), and U.S. Geological Survey (USGS) are evaluating CEC exposures in surface-water habitats in individual parks [e.g., 19,55,56,57] and, more recently, in regional park monitoring networks [e.g., 47,48,58] across the nation. The majority of sampling has taken place in temperate settings.…”

Microbial Water Quality Conditions Associated with Livestock Grazing, Recreation, and Rural Residences in Mixed-Use Landscapes

“…Finally, it is important to note that E. coli and fecal coliform concentrations observed during the study were over-dispersed with a majority of observations at low concentrations, and relatively few observations at high concentrations. This distributional attribute and associated large variability in FIB is common to FIB datasets reported for rural mixed-use landscapes (e.g., [46,50,55,64]). In our study, with the exception of rural residence sites, the median and 75th percentile concentrations were lower than mean concentrations for both E. coli and fecal coliforms (Figures 2 and 3).…”

“…For example, Tiedemann et al [50] and Gary et al [54] report similar magnitudes of increase in fecal coliform concentrations associated with extensively grazed cattle pastures on Colorado's Front Range and Oregon's Cascade Mountains, respectively. Forrester et al [55] and Clow et al [56] both report comparable values for E. coli in several studies of water quality conditions associated with backpacker and pack livestock trail stream crossings, and near-stream pack stock grazing in national parks in the south Sierra Nevada. Pandey et al [37] found mean E. coli concentrations to be less than 10 cfu/100 mL for sample sites on the mid and upper reaches of the "wild and scenic" designated Merced River Watershed draining Yosemite National Park to the south of the Stanislaus River Watershed, providing some reference for concentrations in limited use watersheds in the region.…”

Real‐Time Water Quality Monitoring at a Great Lakes National Park

“…Using certain chemicals, such as propidium monoazide, it is possible to detect only the live cells (Bae and Wuertz, 2009;Kim and Ko, 2012); however, such additional steps could increase cost and analytical time, which can discourage qPCR use in monitoring programs. Streams may accumulate microbial contaminants from multiple sources, such as connecting tributaries, storm run-off, septic systems, and wildlife (Byappanahalli et al, 2003(Byappanahalli et al, , 2012Forrester et al, 2017;Ishii and Sadowsky, 2008;Whitman et al, 2011). Some streams, such as PRiver, have the added pressure of visitor use from recreational activities (e.g., tubing down the river) that can potentially elevate indicator bacterial levels in the water (Forrester et al, 2017).…”

“…Streams may accumulate microbial contaminants from multiple sources, such as connecting tributaries, storm run‐off, septic systems, and wildlife (Byappanahalli et al, 2003, 2012; Forrester et al, 2017; Ishii and Sadowsky, 2008; Whitman et al, 2011). Some streams, such as PRiver, have the added pressure of visitor use from recreational activities (e.g., tubing down the river) that can potentially elevate indicator bacterial levels in the water (Forrester et al, 2017). Hydrometeorological events may also negatively influence stream water quality with additional inputs via resuspension of sediment‐borne bacteria (Olyphant, 2005; St Laurent and Mazumder, 2014).…”