An analysis of wilderness water in Kings Canyon, Sequoia, and Yosemite national parks for coliform and pathologic bacteria.

OBJECTIVE To determine the prevalence of coliform and potentially pathogenic bacteria in remote backcountry alpine lakes and streams of national parks in the Sierra Nevada mountains. METHODS Water was sampled at 55 predetermined lakes and streams that would stratify the risk, based on sites used by backpackers, sites used by pack animals, and uncontaminated wild areas. Sites were distributed among Kings Canyon (15), Sequoia (17), and Yosemite (23). Water was collected using Millipore bacterial samplers, which provided specific counts of coliform and other bacteria in each water sample and also served as a transport media from the wilderness to the laboratory. On return to the laboratory, bacteria were harvested from the samplers and subjected to specific identification and qualitative analysis using standard microbiology techniques for the analysis of water. RESULTS Coliform bacteria were detected in 22 of the 55 sites. All of these sites were below areas used by backpackers or pack animals. Thirty-three sites were free of coliforms. These sites included both those used lightly by backpackers and those with no human or domestic animal use. All samples contained expected amounts of normal aquatic bacteria including Pseudomonas, Rahnella aquatilis, Serratia spp, and nonpathogenic species of Yersinia. CONCLUSIONS Most sampling sites in these national parks are free of coliform or pathogenic organisms. Low levels of coliform bacteria are found in some bodies of water where the watershed has been affected by human or pack animal travel.