Last winter’s Sierra snowpack is melting fast in the summer sun, and backcountry streams are running high. Thirsty hikers may be tempted to gulp from the alpine springs, but experts say look out – the clear mountain water could be full of microscopic organisms just waiting to wreak havoc on your stomach.
Wilderness water can contain disease-causing agents such as giardia, E. coli and salmonella. The higher up and more remote the water is, the less likely it is to be contaminated by human and animal waste, but it’s always a good idea to treat natural water before drinking it, experts said.
“The water runoff is just spectacular – the waterfalls haven’t been like this in my memory,” said Dr. Paul Auerbach, professor of emergency medicine at Stanford and co-founder of the Wilderness Medical Society. “There’s a lot of fast-moving water that would normally give me some security for drinking, but there are just so many people and so many animals. Even direct snowmelt can’t be considered safe.”
Parasites, viruses and bacteria from feces can make their way into the watershed and lurk, invisible, until hikers slurp them up. Outdoor stores sell dozens of water filters and chemical treatments that are easy to carry and will keep you safe from water critters. When you’re shopping, look for products that block bacteria and parasites, such as giarda and cryptosporidium. If it removes viruses that’s even better, said Maggie Brandenburg, outdoor and youth programs manager for the Tahoe Rim Trail Association.
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Hand-held filters help to purify water from the stream directly into your bottle, but be careful to never put the spout of the bottle near the water source because it can get contaminated. Also beware when you’re hiking in low temperatures – filters can freeze, rendering them unusable. Brandenburg suggests sleeping with your filter at the foot of your sleeping bag on cold nights.
Many wilderness experts recommend packing chemical treatments such as iodine or chlorine dioxide tablets, which disinfect water over minutes or hours. Cloudy water should be strained with a bandana or coffee filter before chemical application, and colder water will need to sit longer than warm water. A SteriPEN, which disinfects water using UV light, is also a popular option.
“Be really familiar with the type of treatment you’re using and what the requirements are, and make sure you’re doing it right while you’re out there,” Brandenburg said. “Upkeeping the equipment makes a huge difference.”
Hikers also can do their part to keep natural waters clean for others. Avoid washing clothes, dishes or yourself within 100 feet of a water source because these activities can cause algae growth, according to the Pacific Crest Trail Association’s water safety guide. Dig your cat hole 200 feet away.
About 5 of every 100,000 Californians contract a giardia infection each year, according to the most recent surveillance report from the California Department of Public Health. The incidence has gradually declined since 2001 as more people become educated about water safety. Giardia symptoms include diarrhea, bloating, abdominal pain and fatigue.
“You could be sick for weeks or months,” Auerbach said. “Most infections are limited to your GI tract, but sometimes they progress to become systemic. … It’s all about prevention and avoidance. You can take reasonable steps to prevent most illnesses that don’t intrude on your outdoor experience.”