The WildeBeat

The audio journal about getting into the wilderness.


The WildeBeat edition 98: What's in Sierra Water?

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Folks say water from a clear mountain stream is as good as you can get. But how do you know what you're really getting? This week on The WildeBeat; What's in Sierra Water?

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News from the Wildebeat, the audio journal about getting into the wilderness.

This is program number ninety eight, made possible by your support and membership donations.

I'm Steve Sergeant.

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STEVE: One of the main planning considerations on any wilderness trip is about water sources. Where are you going to find water? How often are you going to be able to find it? How safe is that water? What treatment techniques are you going to have to use to make that water safe to drink? In California's Sierra Nevada, we have it pretty good. For years, backcountry travelers thought nothing of drinking directly from any flowing stream of water they found, without worry. But now, the land managers, such as the park and forest services, recommend that backcountry users treat all of their drinking water no matter the source. We're advised to use filters, boil our water, or add halogen chemicals like iodine or chlorine, for our safety. Are they over-reacting?

STEVE: I'm talking to Dr. Robert Derlet. He is a professor of medicine at UC Davis Medical Center in Sacramento. Doctor, welcome to the WildeBeat.


STEVE: So you have been focusing quite a bit of research on water quality in the Sierra Nevada backcountry. Can you summarize what some of that work is about?

DR. ROBERT DERLET: ...I've been hiking and backpacking in the Sierra Nevada for the past fifty years and it's a unique mountain range of all the mountain ranges in the world. And it's blessed with wonderful sunny weather most of the summer, that the winter snowpack lingers on until late spring. It serves as a frozen reservoir for California, providing about fifty percent of the drinking water of California. And these unique aspects of the Sierra Nevada have motivated me to actually study what's in the water.

STEVE: How do you actually find out what's in the water?

DR. ROBERT DERLET: Well, it's called field work. And as you remember, back from the 1930s, in the Indiana Jones days, much of science at the turn of the century involved field work and going out and working out in the field, collecting samples out in the field, making field observations, and unfortunately, I think, nowadays, most of the scientific work is done in the laboratory. Well, I enjoy the field work. So this involves going into the high mountain rangers, up to thirteen thousand feet throughout the summer months, collecting water, and analyzing it for a number of types of microorganisms, but also looking for other things in the water, such as algae and other substances that might alter natural ecosystems in the Sierra Nevada.

STEVE: So when you collect a vial of water or a bottle of water from some water source in the mountains, how many different living things might be in it?

DR. ROBERT DERLET: There are thousands of living things in it, and that's healthy. In a quart of water, there's on average about ten thousand bacteria. These are healthy bacteria, and they're good for you, and they're part of the natural ecosystem, and without these bacteria higher forms of life, whether it be zooplankton -- tiny organisms, fish, birds, et-cetera would not exist. So there's a lot in the water, even though it's crystal clear.

STEVE: Do we know what all these things are? Has every last one of these species in the water been catalogued, and we know which ones are good for us, and which ones aren't?

DR. ROBERT DERLET: Yes, in fact there's a subspecialty of water -- inland water -- called limnology, and they're numerous departments in universities throughout the world, who examine the microbiology flora in the lakes and streams throughout the world. What's unique about the Sierra is that the water is even purer than one would expect. And when I tell you there's ten thousand organisms per a quart of water on average in the Sierra, you might say "Wow, that's incredible!" But imagine in the Ohio River there might be a hundred thousand to five-hundred thousand.

STEVE: So how do you know which ones are harmful. I suppose you look them up in a book and say, Ok, I know this one has diseased people in the past.

DR. ROBERT DERLET: Right we have a catalogue of what we call pathogenic bacteria, viruses, and protozoa that we know can cause diseases in humans. Probably the best known is giardia. In the Sierra, I think the risk has been overblown. Yes, you can find giardia in the Sierra, but it's much less prevalent, than say, another type of bacteria, say E.coli, that could potentially cause an infection.

STEVE: I read somewhere, and I wish I could give you a citation, but one of the large HMOs in California actually says they've only seen less than a handful of real backcountry waterborne giardia, and that most of the illnesses that people are getting are from something else.

DR. ROBERT DERLET: I would agree with that. If someone goes into the wilderness and becomes ill with say, diarrhea, abdominal pain, or vomiting, most likely they've acquired that disease prior to entering the wilderness, even when they leave the wilderness, they might have had the disease before, and it incubated while they're were in the wilderness. There are some risky areas, and as you may know, cattle still graze in some of the national forest wilderness areas in the Sierra. And I think it's been accepted worldwide that water from watersheds where cattle have grazed does really need to be treated before you drink it, because cattle do excrete a number of harmful microorganisms that can cause serious disease in humans.

STEVE: So how does the average person make that decision about whether the water is safe? I mean, the advice of all the land management agencies is just to treat everything.

DR. ROBERT DERLET: Right, and as a general rule I can understand that if you are providing a general rule to people who basically do not have a lot of wilderness experience, it's best to treat the water. Only if you have extensive experience and know what is in that watershed where those drops come from, can you really make a decision. My gosh, there's no cows up here, there's no pack animal traffic, all there is is wild animals, and it's fresh, the water's probably fresh.

STEVE: Of the pathogens you know that seem to be the most common, the ones you've actually found present, do you feel that the commercially available treatments would be effective on them?

DR. ROBERT DERLET: The commercially available treatments area widely variable in what they can do. Even when you use halogens, for instance, many of the bacteria - E.coli- are highly sensitive. Polio virus, which hasn't been found in the Sierra in a long time, is exquisitely sensitive. When you move into areas such as the protozoa, for example giardia or cryptosporidia, they're much more resistant to halogen treatments, and in fact, cryptosporidium is almost entirely resistant. The way around that, these are larger organisms, protozoa, and can be more easily filtered out. And so I think most filters available commercially are effective against the protozoa. One would have to read the fine print to determine how effective against the different sized bacteria they are.

STEVE: It sounds like giardia is probably the most infectious of the different species that might be a problem for us in the Sierra water.

DR. ROBERT DERLET: In terms of the number of organisms to cause infection, yes.

STEVE: And is that also the most prevalent of the ones you found?

DR. ROBERT DERLET: No. In the Sierras, on average, you would have to drink over two hundred gallons in one day of water to acquire ten giardia cysts. Again, that's averaging the billions and trillions of gallons of water in the Sierra. There are pockets where some of the animals may harbor it, or where a domesticated animal may have brought it or imported it to the Sierra. You really don't know. It's just a roll of the dice.

STEVE: So what's your prescription for the general public? Does it vary at all from what the agencies are telling us for how they should choose and treat their water when they're back there?

DR. ROBERT DERLET: I think that for the general public, that they should follow the recommendations of the national Park Service or the National Forest Service.

STEVE: Doctor Robert Derlet is a professor of emergency medicine at UC Davis Medical Center, and a noted researcher on Sierra water quality. Thank you for appearing on the show.


STEVE: We'll here more from Doctor Derlet in a future program. We'd like to hear your thoughts on water quality and treatment, and your questions for Doctor Derlet. You can call our toll free comment line at 866-590-7373, or send your e-mail to comments at WildeBeat dot net.

STEVE: Wildebeat members can download a much longer extended interview with Doctor Derlet from our WildeBeat Insider web site.

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Our official website is WWW dot WILDEBEAT (that's W-I-L-D-E-B-E-A-T) dot NET. You can help assure future editions of this free service; please click on our support link and become a member. The WildeBeat is produced by Steve Sergeant, with help from Jean Higham, as a nonprofit educational project of Earth Island Institute.

This has been The WildeBeat, program number ninety eight. Thank you for listening.

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