Keeping it Raw? Actually Backpackers You Might Still Want to Treat Your Stream Water

Crossing Streams in the Andes

When I come across a bunch of raw water in the backcountry, what do I do? Sometimes I swim in it, sometimes I desperately try to avoid it in the hopes of staying dry, and sometimes I drink it. When I drink it, do I keep it raw? Very rarely. During my Appalachian Trail (AT) and Pacific Crest Trail (PCT) thru-hikes, the most popular approaches when it came to drinking raw water were to:

  • Filter it: Sawyer Squeeze Mini (0.1 Micron Filter, $20/2oz)
  • Chemically purify it: Aqua Mira ($15/2oz) or bleach (2 drops/liter)
  • Purify it with Ultraviolet (UV) light: Steripen ($69.95/2.6 oz)
  • Choose wisely and take your chances: select high-flow springs whenever possible; otherwise select lower flow springs or small spring- or glacier-fed streams
  • Boil the piss out of it

When I read the title of the link that started showing up in my feeds yesterday, “Actually Backpackers You Don’t Need to Filter Your Stream Water” my initial thought was, #notwrong. Unless my stream water is chunky or green I don’t usually don’t filter it, I purify it. I was surprised when I opened the article and realized that the title wasn’t a bait-and-switch about other water treatment options, the article was really suggesting that treating backcountry water sources for contamination was unnecessary:

“Treating backcountry water sources for contamination is a fundamental tenet of outdoor recreation education, ignored at the peril of contracting giardiasis, cryptosporidiosis, or worse. In this case, however, popular opinion is wrong: The idea that most wilderness water sources are inherently unsafe is baseless dogma, unsupported by any epidemiological evidence… research to date has failed to demonstrate any significant link between wilderness water consumption and infection with these threats”

Don't Fall In!

It is certainly true that the popular opinion in the backpacking community is that you should treat backcountry water sources for contamination, is it also true that there is no link between untreated backcountry water sources and giardia or other water-borne illnesses? (Spoiler Alert: the CDC released epidemiological evidence in 2015 and 2017 linking giardia outbreaks to a backcountry water sources). I settled in and made myself comfortable, curious to see whether the Slate was going to impress me with their SCIENCE or or with their SPIN. Ok, are you ready for it?

“A 1993 study looking at the incidence of Giardia infection and gastrointestinal illness in backcountry travelers in a high-use area of California’s Sierra Nevada found only 5.7 percent tested positive, none of whom exhibited symptoms. Broader-scale approaches have similarly failed to justify concerns: Both a survey of health departments and a meta-analysis found that while giardiasis was prevalent enough to justify concern, there was no connection between recorded cases and drinking backcountry water.” 

I started by looking up the cited 1993 study, “Cyst acquisition rate for Giardia lamblia in backcountry travelers to Desolation Wilderness, Lake Tahoe.”  (Zell et al, 1993):

  • 5.7% (2/35) of the backcountry travelers (1988-1990) acquired giardia cysts during their backcountry trips but remained asymptomatic
  • 16.7% (6/36?) of the backcountry travelers (1988-1990) experienced acute gastrointestinal illness (AGI), but did not show giardia in their stool. However, 1 of the 6 was diagnosed with giardia and treated with flagyl.
  • ≤25 giardia cysts per 100 gallon water sample (sampled at 2 gallons/minute) were found in the one trailside creek (Meek’s Creek) they evaluated in 1988

In summary, they showed that ~6% of backpackers acquired giardia in the backcountry, ~17% of the backpackers suffered from some sort of gastrointestinal illness, and they found giardia cysts in the one wilderness creek that they looked at. Given that their data was collected roughly 30 years ago, I was actually surprised that they found as much giardia as they did. Since the number of humans are one of the largest sources of giardia contamination, and the number of humans heading into the backcountry (and pooping in it) has been increasing over the last 30 years, I’d expect the amount of Giardia to be even higher now. For example, in 1988 there were 31 thru-hikers that hiked through the Desolation Wilderness on their way to completing their Pacific Crest Trail thru-hikes, whereas 717 backpacker passed through there on the way to successfully completing their thrus in 2016. I think it’s also important to note that the quotes in the Slate.com article about wilderness are all referring back to this one wilderness, which is wilderness as defined by the Wilderness Act, and not generic wilderness areas.

Desolation Wilderness

Although I enjoyed reading the 1993 paper, it didn’t convince me that backpackers in 2018 should drink raw, untreated water from streams.  I’d hiked through the Desolation Wilderness during my 2014 PCT thru-hike and opted not to drink the raw stream water then, and the evidence they’d presented so far wouldn’t lead me to make a different decision now. My general rule is to always filter, purify, or otherwise treat my water if there’s any chance that animals have been pooping, bathing, or swimming in it (especially if those animals are humans, beavers, or domesticated animals). Even though the glacially-fed mountain lakes and streams of the High Sierra were some of the most beautiful waters I’ve seen, I still always treated my stream water before drinking it because there was still a chance that someone or something higher upstream had been pooping in it. (As an aside, the backcountry contaminant I was most worried about as I hiked into the High Sierras was uranium, which is found in almost all of the groundwater of the high sierras; I shared my thoughts about the PCT water situation at the time in my trail blog: PCT Days 40-42).

Knee Deep in Raw Water

The next paper the slate article cited, the 1995 survey of health departments, was based on data more than 25 years old that found that 10.5% (2/19) of reported giardia outbreaks from contaminated drinking water were reported by campers/backpackers. The final scientific paper the slate article mentions was a meta-analysis published by Welch in 2000, which initially looked promising, but on further investigation, the only data that they included (met their inclusion criteria) about backcountry scenarios was from 1977. I wasn’t feeling wowed by the Science in the slate article at that point, so I decided that instead of  jumping into the way-back machine and delving into data collected from before I was born, I would see if there was a more recent discussion about giardia in the backcountry in the scientific literature.

It didn’t take me long to find it. In November 2017 the CDC released information about waterborne disease outbreaks collected during 2013 and 2014 (the years I did my thru-hikes of the AT, and PCT, respectively), which included outbreaks of giardia in backcountry settings and in national forests that were caused by drinking water from a river, stream, or spring. The 2011 and 2012 data also specifically cites giardia outbreaks that occurred from drinking untreated water directly from streams or rivers in outdoor settings. These giardia outbreaks are only the ones that met the CDC’s criteria and don’t include individual cases that may be scattered along the trail (e.g. my 2013 case of Giardia from the 100 mile Wilderness on the AT isn’t included in the CDC statistics).

CDC_table

Update: 2/5/2018. Selected outbreaks caused by backcountry, wilderness, and other outdoor water sources (river, stream, and/or spring) reported by the CDC. AGI: acute gastrointestinal illness, G.duodenalis: giardia duodenalis, G. intestinalis: giardia intestinalis

In addition to the epidemiological data from the CDC, I also found a meta-analysis looking at data in both the US and Canada from 1971 to 2014 (published in 2015) that stated that “Half of the outbreaks… were located in camps/ campgrounds/ cabins/ parks“, and found that 35% (101) of outbreaks were from camp/ campgrounds.

Stream or Trail?

After spending some time wading through the science (additional links available at the end of this post), I wasn’t feeling tempted to save money and lighten my pack by choosing to drink lots of raw, completely untreated stream water. The perspective shared in, “Actually Backpackers You Don’t Need to Filter Your Stream Water”, seems outdated in terms of the science, the technology, and the culture. Sure, back in the 1980’s and 1990’s the dogma in the outdoor community was that the average hiker needed to carry a $99.95 water filter that weighed almost a pound, but in 2018 most folks (myself included) are more likely to suggest lighter (2-3 oz) and less expensive (<$25) water treatment solutions. The scientific data from Slate’s sources show that giardia is present in at least some backcountry water sources, and the epidemiological data I found links giardia to at least some backcountry and wilderness water sources. Overall, the data suggests that there is some risk associated with drinking raw, untreated water. Whether or not you feel it is an acceptable risk is a completely different question.

Raw Water on the Appalachian Trail

I almost always filter or treat raw water from backcountry water sources. Although often my options when it come to backcountry water sources are limited, if I have a choice I have a preference. My personal preferences (along with the treatment options I use) are:

  • Springwater coming out of the side of a mountain (raw or purified)
  • Bubbling spring with a high flow rate (raw or purified)
  • Piped springs (purified or raw)
  • Beautifully clear waterfalls (purified or filtered)
  • Streams (purified or filtered)
  • Rivers or Glacial Lakes (purified or filtered)
  • Cisterns (purified and/or filtered)
  • Lakewater and pond water (purified & filtered)
  • Chunky and/or green water (pre-filtered, filtered &/or purified)
  • Cow pasture water (purified & filtered & boiled)

Raw Water in Iceland

Over the years I’ve consumed thousands of liters of water from backcountry water sources in the US, and I’ve only gotten giardia once…

 I got giardia from a pristine looking stream near a shelter in the 100 Mile Wilderness in Maine on Day 147 of my 2013 Appalachian Trail thru-hike. I was really shaken up from having a tree almost fall on me, and distractedly gulped down a whole bunch of my water 20 seconds after adding Aquamira to it. I realized my error almost immediately, but the water was clear and the stream was pretty, so I was cautiously optimistic. About 10 minutes later the trail led me to the beaver pond that my stream had flowed from. Doh! I summitted Katahdin, finished my AT thru-hike, and didn’t think any more about it until a couple weeks later when a gastroenterologist suggested that town food wasn’t my problem, giardia was.

Once was more than enough for me. For me, $20 and 2 oz seems like a pretty low cost (both in terms of $$ and weigh) to decrease the odds of having to go through that again.

Beaver Activity in the 100 Mile Wilderness

7 Questions to Ask Before Drinking Raw Water

As we do more and more research on the importance of microbiomes in human health, I expect that conversations about raw water will grow. Over time our interactions with backcountry water sources may evolve, and we may develop better tools to guide our interactions with raw water. In the meantime, here are 7 questions I ask myself, and would encourage others to ask themselves, before drinking untreated raw water from backcountry sources (or any other source really):

  1. Are you in a long-term monogamous relationship with your raw water source?
  2. Does you raw water get routine testing for water-borne infections (WBIs)?
  3. Does it have unprotected contact with the bodily fluids (or solids) of other people? strangers? beavers? livestock?
  4. Does it have a history of unprotected contact with bodily fluids or other substances that could negatively impact your health?
  5. Sure, it’s beautiful, but how much do you really know about it?
  6. Who and/or what was your raw water with before it was with you?
  7. Do you really know enough about its history to want to be fluid-bonded with it?

In general, I would strongly advise hikers and backpackers to treat the water they take from streams before drinking it. If you do decide to drink raw backcountry stream water, you might want to consider abstaining during periods of heavy rainfall when the risk of drinking raw stream water is higher than usual because waterborne contaminant levels in streams (even in the high sierra) are highest after large amounts of rainfall.

NOTE: Although I know a few people that got giardia on the Appalachian Trail and the Pacific Crest Trail, I know a lot more people that got Norovirus or Lyme disease (see links below) on their Appalachian Trail thru-hikes.


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Related Posts I’ve Written:

Links to Additional Information About Giardia:

Water! (PCT Days 40-42)

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When hiking long distance trails your relationship with water changes. This has been especially true for me as I’ve hiked through the first 700 miles of the PCT, which spends a lot of time in the desert. Water is something that I can’t afford to take for granted so before I leave the water source I’m at, I sit down and figure out where my next water is going to come from.

One of the best resources for figuring out water on the PCT is Halfmile’s water report (a list of the water sources along the route, directions for how to get to the water, as well as comments recent hikers have left about how well the water is flowing or if the source has dried up for the year/drought).

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The northern part of the desert was where I ended up having to go for the longest stretches of time without water. Leaving the town of Mojave it was going to be 30-35 miles before the next reliable water source and 144 miles before I was going to be able to get my next food resupply. If I assumed that I was going to hike 15-20 miles a day that meant I needed to carry enough water for 2 or 3 days and enough food for seven or eight days. Yikes, that’s a lot of food and water! And very heavy! 2 days of water is five or six liters (carefully monitoring water use) and 10-12 pounds and 8 days of food is another 15 pounds… So 25+ pounds of food and water. Definitely a very heavy pack, the heaviest pack I’ve had to carry so far!

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The first water source we encountered after leaving Mojave (golden oaks spring) looked rather….green. The water trough was covered with algae and didn’t really look like anything anyone would ever want to drink, though there was a tiny pipe feeding into it at one end that was dribbling into the trough. Theoretically we could refill our water bottles from that drip (if we were very very patient… Not my strong suit)!

Luckily I’d met a Southbound hiker earlier that had told me the secret to this water source… If you followed the barbed wire fence uphill you’d come to a spot where you could duck under the wire, crawl over a bunch of bushes (and a brick/stone wall), and then draw your water directly from the cistern. After seeing the other two options the search for the cistern seemed like a good idea.

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I picked up the cover of the cistern and looked inside… There was definitely water in there. It didn’t look good, but it looked much much better than the water from the trough down below. I looked down into the cistern, it was going to be a reach to draw the water out, but I was pretty sure I could do it.

I sat down on the ground beside the cistern (falling into a well/cistern is definitely on my NO list) and reached about 2 and a half feet down to the water and slowly refilled my water bottles. Though the water seemed nicer than that from the trough I definitely wasn’t feeling confident about it so I both filtered it (with my sawyer squeeze filter) and chemically treated it (with aquamira).

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Since I was 25-30 miles from the last water source, and many miles away from the next water source I couldn’t afford to be too picky. Even still, Having had giardia once, and not wanting to think about what had leached into the water from the eroding cistern, I was definitely motivated to treat my water very carefully.

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The place I got water from the next day was a trough, but it looked much much nicer and cleaner (and was also a lot easier to access!) than the last one. Even though the water looked clean, I still treated it (I always do) because giardia spores etc don’t necessarily make the water look dirty. It was nice not to have to filter out all the little green, orange, and black floaty bits though.

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Sometimes finding the water sources, even when you theoretically know where they are, is like being on a treasure hunt… you follow notes and signs and scratch marks on the ground and hopefully at the end you find one of the most valuable treasures of all… Water!!!

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And sometimes, just sometimes, you run into trail angels on birding expeditions in the California mountains that offer you water and save you from having to go on yet another wild goose chase!

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Most of the time the water sources are appealing enough that you don’t worry too much about the actual water you’re drinking as long as you’ve filtered it and/or treated it. Sometimes, however, you can’t help but wonder about the extras that you’re getting with your water. The first time that happened to me on the PCTwas at deep creek hot springs where there were rumors of lithium in the water. My filter and my chemicals weren’t going to filter that out, but I was generally more interested in its potential effects than concerned about them.

Looking ahead about 40 miles to the next reliable water source listed in the halfmile water report I read, “BLM website and others report Uranium at Joshua Tree Spring.” Hmmm… Uranium in the water…. That definitely conjured up very different images in my mind than lithium in the water.

Well, how far was is from there to the next water source? How much did I actually *need* that Uranium water anyway? Hmmm… Looked to be about another 20 miles to the next really reliable water source, though there might be some other options since I was pretty early in the season… Then again, it’s the third year of drought in the Californian desert.

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Reading the fine print in the water report was vaguely reassuring? It said that uranium was in most of the of the water in the Sierras, it’s just that Joshua Tree spring was the one of the only ones that had been tested.

Hmmm… Drink the water with Uranium in it, be thirsty, or carry lots of extra water with me and pretend that ignorance is bliss for the rest of the Sierra. Since the temperatures were in the 90s I figured I’d go with the uranium water. Chances were pretty good that the small dosings during the period of time I was going to be in the Sierras were ok, right? Also, dehydration, heat stroke, joint injuries or the combination of all of the above seemed likely to be both more immediate and graver threats.

Despite my decisicion, when I got to Walker Pass and found a spring with cattails growing out of it I decided to fill up with water (carried 4L out and drank 1L), no need to drink excessive amounts of Uranium water when there was cattail water to be found.

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The next day dawned and the temperatures climbed as I climbed what felt like mountain after mountain. I was going through a lot of water. When I got to Joshua Tree spring I consulted my water report. Therewas probably water at Spanish Needle Creek 7 or 8 miles ahead, but it sounded a bit confusing… I decided I didn’t need to get a lot of water, but the addition of one Liter of water would make my life a whole lot better… It was time to try out the uranium water.

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When I got down to the spring there were two signs. One which said that the water wasn’t fit for drinking and one that had the standard list of backcountry water caveats essentially telling you to filter and treat your water. I looked at the stuff growing in the water of the trough… It looked like all the usual floaty buggy things. Since there weren’t any three eyed fish mixed in I figured it must be fine (please note appropriately level of sarcasm here). Besides, uranium water is probably good for fighting off precancerous cells if you have any, right?

As the day progressed it got hotter and hotter and I was glad to have my uranium water on hand. The next water source, Spanish needle creek, was pitiful at best (I’d be surprised if there is any water left there in a couple of weeks), and looked more like the runoff water from a recent storm than a creek. I filled up with another liter of water there (which took about five minutes) and figured that that combined with the water I had left would cover me for the 10 miles or so to the next water source.

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As I hiked north and got to the places where the more reliable branches of the creek were supposed to be and found them dry I started getting a little bit nervous… It was really hot out, and it was really exposed, and what if the upcoming water sources were all dry? After having hiked 20+ miles that day, hiking more than the 24 mile total I’d planned on was a truly daunting thought.

As I crossed the dry bed of chimney creek (mile 24 if the day where is been hoping to find water) my heart sank. It was at least 2 miles uphill to the next spring and what if it was dry too? I still had water left (my emergency half liter) and was still pretty well hydrated, but it wasn’t going to be fun. By the time I got there it would be almost dark and probably cooler out… That would be a plus.

As I turned the corner and looked at the mountain in front of me with grim determination I heard voices. Huddled in the shade of a nearby bush/tree were at least half a dozen thru-hikers. “Water, the most amazing water is here!” They called out to me.

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I dropped my pack and joined them in the shade. Water, glorious water… it felt like the best news I’d ever heard. It seemed funny in a way, the places where I thought that I needed to be really careful about water I hadn’t had any trouble, but when the section where there was supposed to be easy water (water every ten miles or so) is when I was happiest to find water. Though the desert has been awesome, I’m looking forward to some of the upcoming sections of the trail where I won’t have to worry about water nearly as much!

P.S. I apologize for the images, I installed a WordPress update and ever since then I’ve been having trouble with my image uploads. I’m working with wordpress now and hope to have the issue resolved soon!

P.P.S. Check out this USGS fact sheet about where the Uranium is near Joshua Tree Spring (the southern sierra), or this report for the central sierrras.