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Be Smart About Drinking Water in the Wilderness

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It’s summertime and the mountains are calling. Before you go, it’s good to remember a few tips for safe drinking water on the trail.

Giardia, a parasite that causes diarrhea, is a common concern for hikers but there are a multitude of pathogens in natural water sources that can make you sick. Parasites, bacteria, viruses and worms can all contribute to unclean water and lead to diarrhea.

“Bacteria is likely the most common cause of diarrhea from wilderness sources, but giardia is also common,” said Christopher Hart, PA-C, from Samaritan Depoe Bay Clinic. “Drinking untreated water from streams and rivers greatly increases your chance of getting an infection and becoming ill.”

No matter how pristine a mountain stream looks, it can still be filled with tiny pathogens. Your best bet is to drink only disinfected water.

How Illness Spreads

Wild animals can carry diseases even if they don’t look or act sick. The pathogens that cause digestive upset are passed through their stools to water sources. A beaver can release billions of giardia spores into the water but it only takes 10 to make you sick. A cold mountain stream offers the perfect environment for these microorganisms to survive.

If you hike with your dog, it’s best to filter his or her water as well. Although different types of bacteria, parasites and viruses affect canines, your dog is still vulnerable to an infection. Leptospirosis and giardia are both transmitted by the stools and urine of wild animals and can infect the water your dog is drinking.

Options to Disinfect Water

The four main ways to disinfect water are boiling, ultraviolet light, using a filter, and halogenation, which are tablets that contain iodine or chlorine to purify the water.

“Boiling is the most effective way to clean water, but it takes time, and you need fuel and a stove,” said Hart.

He notes that ultraviolet light purification is also a good option in many cases. It is effective in killing bacteria, viruses and protozoa such as giardia and cryptosporidium. It is lightweight and easy to use. However water must be clear, not cloudy or dirty in order to be effectively treated. The device also requires batteries which could die, and the overall cost is higher than other methods.

“I recommend having two sources available when you’re on the trail, and a combination of filtering and halogenation is an inexpensive and simple way to make water drinkable,” said Hart.

In the two-step process, filtering water removes bacteria and parasites that are physically larger, while halogenation kills any tiny viruses that remain.  

For a day hike you will likely be able to bring enough water with you from home, but having a filter and halogenation tablets in your backpack is a good idea in case of an emergency. Filters are small and lightweight and can be purchased for as little as $20. You can purchase a filter that is an external device, or as an integrated part of a water bottle if you will only be using the water only for drinking. If you will be gone overnight, an external filter can purify water for other uses like hand washing or cooking.

Iodine or chlorine tablets can be purchased for less than $10. Some brands are sold as a set with a taste-neutralizing tablet to add after the water is treated. You can also add vitamin C to neutralize an “off” taste to the water.

Water purification tablets and backpacking filters are widely available at outdoor supply stores like REI and Big 5, and stores with robust camping departments like Walmart.

Is It OK to Swim?

In order to become sick, you need to ingest a certain amount of each pathogen. According to Hart, swimming in a natural lake or stream won’t make you sick unless you drink the water. Just skip the dip if you have an open wound.

Tips for Safe Water

To help ensure your drinking water is safe, Hart recommends these tips:

  • Collect drinking water from a moving source like a stream.
  • Disinfect all drinking water before consuming.
  • Wash hands with soap and disinfected water after going to the bathroom and before preparing food. Hand sanitizer is also effective, but washing with soap and water is still a good idea if your hands look dirty or if you will be hiking for several days. Sanitizer can be drying and lead to cracked hands, which provide an entry point into the body for bacteria and infection.
  • Observe good trail habits to help protect others bury human waste eight to 10 inches deep and at least 100 feet from water sources.

If you do become sick, it can be in as little as a day after exposure in the case of the bacteria E. coli, or as much as nine days in the case of giardia. Many cases of diarrhea will resolve on their own after a few days, but if you are experiencing bloody stools, fever, or symptoms that last longer than three days then talk to a doctor.

See a provider today at a Samaritan urgent care or walk-in clinic near you.