Backpackers may not have to be as careful with drinking water in the Sierra Nevada as they have in the past. According to a study by University of California, Davis School of Medicine researchers, Sierra Nevada lakes and streams are generally very clean.
"If you get sick in the Sierra, it's probably because you eat fast food before backpacking," said Robert Derlet, a UC Davis physician and one of the study's researchers.
Derlet and his colleague, pathology researcher James Carlson, studied water bodies in Yosemite, Sequoia and Kings Canyon national parks, as well as Desolation Wilderness.
The information - gathered in the summer of 2003 from nearly 100 locations throughout the Sierra Nevada - suggests that the risk of picking up giardia in the backcountry is slim.
"People always think of giardia as the culprit in the wilderness," Derlet said. "Essentially it's E. coli if they get water in the wrong place at the wrong time."
But Derlet, an avid outdoorsman who often ventures into Sierra backcountry, said it's not always necessary to use water filters or iodine tablets if backpackers pay attention to where they obtain their water.
"Personally, if I get (water) from a side stream, I will drink the side stream water without purifying it," he said.
Backpackers who aren't sure of water quality in a particular stream should continue to treat drinking water, especially if the stream is below roadways, popular trails or current or former cattle grazing areas.
"I think I would avoid areas where there was cattle," he said.
Derlet was surprised by findings that Sierra lakes are also often very clean. Ultraviolet rays "zap" bacteria in the top 12 inches or so of water, he said.
Derlet said the study's findings have a significant impact on California.
"The Sierra Nevada provides 50 percent of the fresh water for California from the snowpack," he said.