Hikers Over a Lake

Like most backpackers, Robert Derlet has wondered about the purity of the wilderness lakes and streams that he relies on for drinking water. Unlike most backpackers, Derlet has the scientific chops to do some investigative work and satisfy his curiosity.

Readers, meet Bob Derlet. He is:

  • A professor at the University of California-Davis School of Medicine.
  • An affiliate faculty member of the school's John Muir Institute of the Environment.
  • A part-time emergency room physician at UC Davis Medical Center, a teaching hospital with more than 400 students.
  • A much-traveled hiker who has pounded trails for more than four decades.

Robert Derlet Robert Derlet

Since 1998 Derlet has been testing the water quality in lakes, creeks and streams in California's Sierra Nevada—a mountain range he has explored since his teens. He anticipates his research will eventually form a 20-year study on Sierra water quality.

In Derlet's younger days (he turns 59 in 2008), backcountry water-quality concerns were fairly minimal. The most prevalent hydration device in those days was the venerable Sierra Cup—no pumping, no tablets; just dip, sip and go.

Yet in the 1970s, tales of water-sickened hikers began making the rounds. Soon the word Giardia (the microscopic pests routinely cited as the culprits behind all this digestive distress) entered the backpacking lexicon. Water filters became an essential take-along on any lengthy backcountry excursion.

Had backcountry water suddenly and irretrievably become contaminated with legions of invisible-to-the-eye cooties?

Research on wilderness water quality is scarce. Yet two studies conducted in the 1990s indicate that poor sanitation practices, particularly unwashed hands, are likely more responsible for causing prolonged bouts of diarrhea, cramps and nausea in backpackers than ingesting giardia and other waterborne pathogens.

All of this spurred Derlet to undertake his own study. "I always had questions about the water," he says. "I have a background in infectious diseases, so I tried to match my background with my enthusiasm for hiking."

In each year of his study Derlet has tested 100 or more sites in California, taking samples as far south as Mineral King, as far north as Castle Lake near Mount Shasta, and at hundreds of points in between—in Yosemite, Sequoia and Kings Canyon national parks in addition to several wilderness areas throughout the central Sierra.

Among Derlet's findings:

  • Wilderness water in remote, less-traveled regions of the Sierra is usually free of waterborne pathogens (Giardia lamblia, Cryptosporidium parvum, et al.). Derlet says he routinely drinks untreated water in locations where his observations of the source and familiarity with the area indicate to him that the water is safe.
  • In any wilderness setting, poor sanitation practices—unwashed hands in particular—are a significant (and in Derlet's view, far greater) threat to backpacker health than untreated water. Hand-sanitizing gels or wipes are a smart addition to any pack.
  • Results in the Sierra cannot be universally applied to all wilderness areas. He says, for instance, he would treat water he collected along the Appalachian Trail due to that route's heavy traffic (by both humans and domesticated animals). But certain factors involving the water source (remoteness, very high elevation, no evidence of human or animal activity) generally indicate that the water should be pure.
  • Soap residue is a growing threat to otherwise pristine water sources. Uninformed people are lathering up and bathing directly in streams and lakes, and the residue provides nutrients that can sustain and expand populations of pathogens. Derlet's solution: Collect water in a portable plastic container (search for "sinks" at REI.com) and wash at least 200 feet from a water source. Pour any gray water on the ground far from any water source.

Our Q&A with Derlet

Below are excerpts from Derlet's conversation with REI.com in November 2007:

Q: How many samples have you taken since you began your research?

A: "For a ballpark figure, about 1,000."

Q: Is this the best science done on backcountry water so far?

A: There are a few studies that have been published—a couple in the 1980s, and I know there's at least one study on the Rocky Mountains. But there's not a lot looking directly at Sierra water quality."

Q: What prevailing trends have you detected?

A: "The biggest trend is what's obvious: In watersheds where cattle have grazed, the water is contaminated. This is really well-known, if you look at all the EPA literature on pasturing lands from the Midwest to the East Coast. Cattle contaminate the watershed with multiple types of pathogens. But no one has really shown this to be directly linked to the Sierras. I think that's the key point."

Q: What about above such watersheds? Does any evidence exist that backcountry water is contaminated?

A: "It depends on the land-use area, and I'm not sure how to phrase this appropriately. There are some areas where there's no risk except wild animals. There are other areas that are extremely high-risk—like areas where cattle graze. There are other moderate-risk, less-concerting areas, like areas where only backpackers go. If backpackers have followed the rules and have washed away from the streams and followed appropriate wilderness etiquette, the water should be good. In areas used extensively by pack animals, where the pack animals are allowed to poop near or directly into the streams, there will be problems."

"I might add that Congress passed the 1996 amendments to the Safe Drinking Water Act, which required states to conduct a source water allocation for every public water supply. So there is a direct mandate from Congress to know what's high up in the watersheds."

Q: How would you summarize your findings?

A: "For backpackers and hikers traveling in any areas where there cattle grazing is allowed, you need to be very cautious with the water. That's water I would certainly filter, and I'd use a filter that would remove both bacteria and protozoa. The pore size would have to be small enough so bacteria could not pass through. You also need to be cautious in areas where there are large numbers of pack animals, because pack-animal manure can carry many pathogens ranging from Giardia to Salmonella to E. coli. Here's a fact I recently uncovered: Giardia-infected cattle excrete nearly 100 million Giardia cysts per day, and pack animals excrete about 12 million per day. Twelve million! So be careful if you drink in those watersheds.

"In the areas where I'm doing research, in high-elevation regions of the Sierra, I'd say there is less than a 1 in 100 chance that a person would get sick drinking untreated water from side streams. By side streams, I mean a stream that has no upstream trail, no human presence and no grazing animals. Personally, for the simplicity of drinking untreated water, I don't mind taking the risk of getting a little sick. The probability is very low, and there's very little chance that anything will happen. Basically, where there is no evidence of cattle grazing, no activity involving large groups and no pack animals, the water is probably going to be fine."

Q: Does that apply to any wilderness area in North America?

A: "My research has been conducted in the high alpine areas of the West, where sometimes I'm as high as 13,000 feet. If I was hiking the Appalachian Trail, I would probably filter my water the entire length of the trail. In the East, historically there has been a lot of animal use at all elevations, and I would worry about the water. I believe there's a difference between very tall mountains in the West and what I would call lowland mountains like the Great Smoky Mountains in the East."

Q: Even at high elevations, aren't you concerned by how wild animals might taint the water?

A: "The biggest likelihood that something will get into the water is if birds drop something into it. Even if they do, the probability that it will make a human sick is very low."

Q: If you see only signs of humans, not animals, what's the risk factor then?

A: "In areas where we find evidence only of backpackers, we generally didn't find a lot of coliforms [bacteria associated with animal or human fecal matter]. But we noticed there was an increase in what are called heterotrophic bacteria, just general bacteria. It looks like an increase in dissolved organic carbon, which suggests that people are washing directly in the streams—at least some backpackers are, and they should not do that."

Q: Is the problem due to swimming or people actually using soap in the water?

A: "I don't really know the answer to that question. That's something we need to research. My guess would be that some people are using soap directly in the water. But people have sunscreen on their skin. So what's the harm of introducing sunscreen (or insect repellent) into the water? I don't really know the answer.

"In the Sierra, or some areas of the Cascades, these granitoid or high-alpine areas called oligotrophic environments. That means they have very little in the way of nutrients. So all of the natural ecology is based on low nutriments. If you introduce nutriments in the form of substances found in soaps or detergents, or I would suspect even sunscreens, it provides basically growth factors—not only for the algae that are there, but perhaps for new types of algae. It can also provide new growth factors to support bacteria that are introduced into the water."

Q: So people need to remember that using soap directly in a stream or lake is bad, true?

A: "Yes, it's very bad. I talked to one ranger this summer who talked to a guy who went into a stream and soaped up. The ranger said the guy had not even a clue. He had no idea about putting soap in the water, where it went from there or how it would affect the environment. He had just never been educated. Wilderness rangers who give out permits are really to be complimented. They give the lectures about how to be careful with the water, with campfires. They're really the front line for preserving the wilderness."

Q: How do you, a person who is highly concerned about keeping water quality pure, clean up in the backcountry?

A: "My personal plug is for people to buy these little plastic water buckets or sinks that REI sells, put water in them, take them more than 200 feet away from the stream or lake and then wash, well away from the stream. And that includes dishes. I come across areas where people have washed their dishes in a stream and there's leftover oatmeal on a rock in the creek. That's not good. For soap, I'll use a straight, simple, common soap, like Ivory. Something that doesn't have a lot of extra stuff in it."

Q: What about biodegradable soap?

A: "I really need to look into the analysis. From what I read in the literature, they can still biodegrade into something that can be used by microorganisms and become substances that can harm the environment. But I don't know the facts. We're trying to design an experiment for next summer up at a place called Castle Lake, which is near Mount Shasta. We'll use the lake water as the background. We'll know exactly how much algae there is, and how many, such as diatoms or other microorganisms. We're going to look at putting sunscreen in one tank and other soaps in other tanks and we'll see what happens. I don't think anyone has done that experiment."

Q: In addition to drinking only clean water, how important is personal sanitation to keep a backpacker healthy during a trip?

A: "It's very important. A couple of points: If someone gets sick after leaving the wilderness, they may have gotten sick from a hamburger they ate before they went into wilderness. You don't know, because there's an incubation time for illnesses. Another thing: When you're in the wilderness, somebody can be a carrier for some disease. If they don't wash their hands or use proper sanitation, they can transmit the bug—the disease,

Q: What about using sanitizing wipes?

A: "That would be great, as long as people pack them out. A gel would be absolutely wonderful."

Q: How often should a sanitizer be used?

A: "Use it before making meals and after going to the bathroom."

Q: Earlier you mentioned soap can spur algae growth. Does algae naturally occur in water?

A: Yes. To grow, algae need things such as nitrogen, phosphates and iron. When nutriments are added to their environment they can grow much more rapidly. Remember college biology? Growth factors and substance substrates? Think of grass on the lawn. If it's an anemic-looking color, you throw some fertilizer on it and it grows big and green. Same with algae."

Q: Are waterborne pathogens naturally occurring?

A: "We don't think the majority of serious pathogens are naturally occurring. The introduction of people, horses or livestock provides two things:

1) a basic substrate [the substances that organisms require in order to live] and

2) pathogens.

"The two together are worse than one alone. So let's say maybe the water is really pure. In fact we can do this outside the mountains, in a lab. If the water is really super-clean and you drop some E. coli in it, they don't survive very long. But if the water is very clean and you drop in some E. coli plus you drop in some nutriments, they'll survive."

Q: How can a wilderness traveler evaluate the quality of wilderness water?

A: "First of all is knowledge of the area. Say you've been there many times, and you know that upstream from where you get the water there's nothing—no cows, no trails, no livestock. Chances are the water is going to be pretty good. Now, there's always a small risk that a marmot or a bird dropped something in the water. So there's always a risk, but it's pretty small. But say you're a PCT thru-hiker. On such a long trail you don't really know what's up every side creek. You can look on a map and have a pretty good idea. But if you come to a water source and it's filled with algae or it's stagnant, that's high-risk water. If there was a lot of foam in the water, I would worry about it."

Q: How often do you drink water without treating it?

A: "I drink untreated water about 90 percent of the time. But I know the mountains of the Sierra Nevada very well, and I know where I can get water I don't have to worry about. Occasionally I get stuck on a river where there's no other source and I know there's a lot of activity upstream. I'll treat that water."

Q: Have you ever become ill from drinking water?

A: "Not that I can recall."

Q: Do you use a filter?

A: "No, I never have. I take some straight iodine, and I put some drops in as needed."

Q: Why iodine?

A: "Because I've have just used it for the last 20 or 30 years, and I've just adapted to using it."

Q: What would you recommend that a newcomer to water treatment use? What about chlorine dioxide for a chemical treatment?

A: "There are pros and cons to every one [method]. Chlorine dioxide works fine. A lot of people use [iodine] tablets. Tablets are more convenient. I'm just kind of like an old-timer. I started with drops, using drops in a lab, so I just continued with that. Besides, I use it so rarely; 90 percent of the time I don't treat it, so it's no big deal."

Q: But can someone in, say, North Carolina, draw the same conclusions about water in that state's mountains as you have about high alpine areas of the Sierra?

A: "It might be very difficult. In Appalachia, there's a lot of history of farming and farm animals and stock, and I would suspect that the water there has a higher risk of containing pathogens. For Washington and Oregon, I really can't comment. I would imagine some areas of Washington are similar to the Sierras, with glaciers and high-elevation rock. But where there have been farm animals, livestock or pack animals, there's higher risk."

Q: Is it wise for people to carry some sort of water-treatment option?

A: "Yes. There are lots of options. Iodine is a very personal thing. The chlorine tablets are probably the better way to go. Now, what if you're on the PCT and the only water has been contaminated by cows? Well, most of the halogens don't affect cryptosporidia In that case, if you're going to go where the cows have been, you can boil it. You can always boil it. Or you have to filter it."

Q: Devices marketed as purifiers also eliminate viruses, which are exceptionally tiny. Have you detected any viruses in your study of Sierra Nevada water?

A: "No, I haven't. That's a theoretic consideration, that there would be viruses there. Some viruses get very, very small. Most of the commercial filters on the market say that they protect against bacteria. They've looked at the standardized bacteria that you would worry about such as E. coli and Salmonella, but not the tiny, tiny ones."

Q: Have you found any tiny, tiny bacteria in your study?

A: "We've found small bacteria, but it hasn't been pathogenic. It's just been normal. Water normally contains 10,000 to 100,000 microorganisms per quart. That's normal water you would get from a wilderness river. It's teeming with bugs. But they're not harmful. In fact, some people believe that the bugs are good for your gut."

Q: Do you believe that?

A: "These little microorganisms, they don't hurt. They're basically called heterotrophic bacteria. They're just part of nature. In fact, I would worry—and I do worry on occasion—when I've come to water where actually no organisms exist. It's like the streams have been poisoned or something. Now, the exception to that are springs."

Q: Like a spring coming directly out the rock in a mountainside?

A: "Man, springs are some of the best places—and you can hardly find any bugs in that water. Some of the best water comes right out of the mountainside like that. It's unusual that there would be a marmot or anything like that up there. You're OK to drink that."

Q: If someone comes to a water source and wants to drink straight from it, what's your best advice? Should they or shouldn't they?

A: "It depends on their degree of experience. If they're not experienced, they should take a filter or purifier with them. Once they become more experienced, they have the ability to sense which water is coming out of a spring or water from a side steam. If there's nothing up a side stream, it's generally going to be safe. But it all depends on the person and how comfortable they feel."

Robert Derlet

Q: If in doubt, filter?

A: "Yes. Otherwise, take smart chances. I've basically spent most summers up there [the Sierra Nevada] for 40 years. I know the mountain range like the back of my hand. Someone who has not gone backpacking before may not know and may do things I obviously wouldn't do. If you have familiarity of the side streams and are aware there are no side streams or pastures, then water is low risk and people can drink it without filtering."

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