Lake Water? Caution Is Good, Fear Is Not by
Thirty years ago, we didn't fret about lake-water microbes. We just
drank the water straight or spiked it with iodine. Today, that is
changed. Many of us grip our water filters and cautiously take a sip. In
fact, Giardia and other water-borne pathogens often star in those
scary mind-flicks we conjure from bears, bugs, and huge, wind-swept
Don't get me wrong. I'm not saying that six months of recurring
diarrhea isn't something to ponder. Just don't panic if you swallow a
mouthful of lake water. The Boundary Waters isn't a New York sewer. Much
of the water is clean. The problem is, we can't distinguish the clean
sources from the dirty ones.
To Treat or Not To Treat?
That's why I filter, boil, or chemically disinfect the water I use
for drinking, washing dishes, and brushing my teeth. On the other hand,
canoe-country author Michael Furtman has roamed the Boundary Waters for
nearly 40 years, and hasn't treated a drop and has never been sick. He's
not alone. Quite a few Boundary Waters old-timers and wilderness guides
drink the water. But they are careful about where they collect it. More
on that later.
Furtman recently met a canoe party that was rationing bottled water.
''It was warm, humid, and all were sweating profusely,'' Furtman says.
''They needed water, but weren't drinking enough because they were
worried about drinking from the lake. I think it's riskier to not drink
the water. I see too many people not drinking water on trips.''
Even those who filter tend to be dehydrated because pumping takes
time and effort, he says. ''Dehydration is, I believe, a far more common
malady among wilderness travelers than Giardia, at least as far
as the Boundary Waters/Quetico is concerned.''
Scientists who study wilderness water agree that staying hydrated is
important, but say microbes shouldn't be part of the mix. ''When I see a
stream, all I see is a toilet,'' says Charles Gerba, a University of
Arizona professor of environmental engineering. ''My feeling is you
never know who used it as a toilet upstream; and every stream is a
Ryan Jordan, a Montana State University senior research engineer in
the Center for Biofilm Engineering, is an avid backpacker who has tested
many backcountry water sources. He has found pathogens in clear water in
places that would seem least suspect, and tested some nasty-looking
sources that turned out to be pathogen-free.
''The bottom line is this: If you play backcountry water roulette for
long without using a form of treatment, sooner or later, your number
will come up. And that won't mean you're a winner,'' he says.
Patricia Bloomgren agrees. She directs the division of environmental
health for the Minnesota Department of Health. ''We would not consider
the water safe to drink even in the pristine Boundary Waters,'' she
says. Her agency requires that even resorts adjacent to the Boundary
waters clean their drinking water to meet the surface water treatment
rule of the Safe Drinking Water Act.
Bloomgren says that she has several friends who have contracted
giardiasis on Boundary Waters canoe trips. ''Some people can go up there
year after year after year and never treat the water and don't get
sick,'' she says. ''And someone else goes up there and does. If I did a
canoe trip, I would be treating my water.''
What Are the Odds?
So what are the odds that pathogens will find their way into your
About 15 years ago, the Superior National Forest conducted a small
administrative study that looked for coliform bacteria in BWCA lake
water. Not surprisingly, they found more bacteria near the shore than in
the middle of the lake, says forest hydrologist Bob Berrisford.
Several years ago, the forest also looked at the incidence of
giardiasis in counties adjacent to the Boundary Waters. During a
three-year period, two counties had one reported case and another had
two or three. But many cases might go unreported because most visitors
aren't from the area and are back home when the illness hits.
''We haven't gotten much feedback from the public indicating there is
a problem,'' he adds. ''If a lot of folks thought it was, I think we
would be hearing about it.''
Still, Berrisford endorses the forest service recommendation that
Boundary Waters visitors treat or filter all their drinking water. Those
with compromised immune systems should particularly heed the forest
service advice, says LeRoy Halberg, registered sanitarian for Cook
County in Grand Marais, Minnesota. This can include diabetics or anyone
with an illness. It also includes anyone over age 55 or under age two,
Gerba says. ''If you're over 55, you should take full precautions. This
is a major susceptible group.''
Start With the ''Cleanest'' Water!
Start with the cleanest water you can find. There's no way to tell by
looking whether a source has disease-causing pathogens, but there are
ways to play the odds.
''I consider water sources near heavily used locations to be suspect,
particularly if those locations are near a road and thus easily
accessible by folks not normally aware of good backcountry practices,''
Jordan says. '' In April, I was camped on the Appalachian Trail near the
Big Spring Shelter (North Carolina), and found a pile of human feces
about five yards upstream of a presumably pristine spring.''
Beaver are notorious Giardia carriers, so stay away from
beaver ponds or areas downstream, Gerba adds.
Also, avoid places where people swim, such as areas near campsites.
Gerba, who studies stuff like this, says the average person carries a
quarter-peanut-sized bit of fecal matter in his or her shorts. When they
go swimming, microbes spread from this material into the water.
''Any activity that causes untreated water to be ingested (swimming,
fishing and so on) could be an avenue for infection,'' Jordan adds.
''You have to use common sense here. One person swimming in a remote
mountain lake is probably not going to infect the lake for the rest of
And pass on stagnant water, Jordan advises. ''Stagnant water,
standing water with no influent or effluent streams to replenish the
source, is certainly a candidate for chemical treatment. So are waters
that are rich in suspended solids, like algae-rich and silt- or
Deep areas of large lakes may be one of the safest places to fill
your bottles. Furtman recommends staying away from shorelines or
streams, unless the water is going to be boiled for cooking, because
beavers travel there and moving water can suspend Giardia.
Jordan notes, however, that Giardia cysts still can be found
in the middle of a deep lake. Conventional wisdom has it that cysts sink
to the bottom in these areas but Jordan says microbes don't settle in
the same way that sand particles do.
''A lake harbors convection currents induced by both thermal
gradients in the water and surface chop from the wind, and there are few
places in a lake that are truly quiescent,'' he says. These currents are
strong enough to suspend microorganisms.
Cysts also can be found on algae and other organic matter that forms
a film on the lake's surface, which is held in place by surface tension.
To keep lake film out of your bottle, plunge it into the water
mouth-down at arm's length. Let the air escape only when it's beneath
the surface to avoid taking in surface debris.
Filter, Treat or Both?
Gerba recommends filtering the water and then treating it with a
disinfecting agent such as iodine, Aquamira™ or Pristine®. (Aquamira™
and Pristine® are chlorine dioxide disinfectants. More about them
He advises using filters and chemicals together because filters stop
bacteria that cause diarrhea, but they don't block viruses, which are
much smaller. Meanwhile, iodine alone can kill Giardia, bacteria,
and viruses, but doesn't stop Cryptosporidium, which causes a
7-day-long cholera-like diarrhea. At the proper concentration Aquamira™
and Pristine® kill just about everything. However, disinfectants won't
remove silt, so cloudy water needs to be filtered, unless you like grit.
Microorganisms also cling to particles in the water, making them harder
''There is no question that a filter in combination with chemical
methods provides one of the best combinations of treatment for
backcountry water,'' Jordan says. ''But there are limits to patience and
you have to define for yourself what level of acceptable risk you want
to take. If I'm drinking out of a riparian stream frequented by cattle,
you can bet that I'm going to combine a chemical treatment like Aquamira™
with my filter. But if I'm dipping out of the headwaters of a mountain
creek at 12,000 feet, the chances of encountering a deadly virus or
bacterium are probably pretty slim.''
When using both the filter and a disinfectant, filter first, and then
add the chemical treatment, Jordan advises. The residual disinfectant
helps protect the water from pathogens, such as those from dirty hands,
that might later contaminate it.
Boiling is a third alternative. ''We boil water at night before we go
to bed,'' Halberg says. ''By morning, the water is at 45 degrees, and we
make some of it into juice, and use the rest to fill our water
What To Buy
Not all filters are created equal. Anyone can slap together a filter
element and a couple hoses, but that doesn't mean it will work properly.
''You need a good engineer to design these,'' Gerba says. If the
seals don't hold up or water leaks past the filter element when pressure
builds up, the microbes get a free ride into your glass.
So make sure the filter is registered with the EPA. Gerba's lab does
EPA certification testing for point-of-use water filters and the
procedure is rigorous. In fact, one technician in his lab does nothing
but test filters. ''These are really mini water treatment plants and we
have to make sure the units perform throughout their lifetime,'' Gerba
says. ''The EPA tests give these filters some rough challenges.''
REI and L.L. Bean require testing before they will sell a product, so
those are good places to buy a filter, Gerba adds.
Most backpacking water filters require hand pumping, which can turn
into real work if you're supplying a group. Some backpackers have
recently switched to gravity-fed systems in which a water bag is filled,
hung from a tree, and attached to the filter by a hose. Another hose
below the filter goes to the clean water bag. The water flows through
the filter while you set up camp. (See ''Additional
Resources'' below for more information on gravity filters.)
Iodine was the standard water treatment method for wilderness
travelers until filters came along. Today, it's less popular because it
doesn't kill Cryptosporidium. However, the new disinfectants,
such as Aquamira™ and Pristine®, are much more effective than iodine
and will kill Cryptosporidium. They use chlorine dioxide to kill
pathogens, and, in foul-smelling water, can significantly improve the
taste and odor. (Aquamira™ is available from Campmor. Pristine® can
be purchased from the company's web site. See the ''Additional
Resources'' listing below.)
Cloudy water tends to neutralize treatment chemicals, so try to start
with clear water, says George Farkas, of McNett Corp, which makes
Aquamira™ . Just running the water through a coffee filter before
treatment will help significantly.
Although water treated with Aquamira™ is ready to drink in as
little as 15 minutes, it's best to allow as much time for disinfection
as possible. Some wilderness guides will treat a gallon or two in the
evening, let it stand overnight, and then fill water bottles in the
morning. ''This enhances the safety margin, especially when using lake
water, which is often teeming with microscopic life,'' Farkas says.
Although microbes can be a problem, the Boundary Waters is protected
from municipal and industrial pollutants by its topography and remote
location. Furtman notes that no watersheds flow into the Boundary Waters
or Quetico from outside. So no large concentrations of municipal and
industrial pollutants can flow into canoe-country waters. And airborne
pollutants are present in such low levels that ''you'd have to drink the
water the rest of your life for there to be any chance at all of
accumulating significant amounts of mercury, PCBs, and so on,'' he says.
It's Not Just the Water
In Long Distance Hiking: Lessons from the Appalachian Trail,
Roland Mueser interviewed thru-hikers who spent months walking the
entire 2,150-mile-long trail. He asked about their water treatment
strategies and illnesses, and found no difference in the rate of illness
between those who treated or filtered the water, those who sometimes did
and those who didn't filter or use disinfectants.
The sample was small and the results were based on what people said
they did, rather than direct observation. So the results aren't
scientifically rigorous. But they do raise some interesting questions.
Why did those who faithfully treated their water still get sick? It
could have been poor filtering or treating technique, but Mueser
speculates that some illnesses might have come from other hikers, not
Stomach illness can be transmitted by sharing cups, dishes or food,
such as a bag of gorp. Other illnesses can result from spoiled food and
Gerba says Shigella, which lives in human intestines, is
easily spread through a camping group. This happens when a person
doesn't wash after defecating and prepares or shares food with others. Shigella
causes diarrhea that is often bloody and accompanied by fever and
To test how bacteria spreads in camping situations, Gerba took a
group into the Santa Catalina Mountains north of Tucson, Ariz. He split
the campers into three subgroups: those who didn't wash their hands,
those who washed with soap and water, and those who used alcohol gels.
The hands of those who didn't wash were soon covered with E. coli
bacteria. Those who used soap and water had some E. coli, and
those who used alcohol gels had the cleanest hands.
''You can use either the disinfectant wipes or gels,'' Gerba says.
''I would use this as an adjunct to washing hands.'' He recommends
washing for at least 30 seconds and rinsing well. And he cautions that
sharing anything such as food, dishes, or water bottles can transmit
Dishes that aren't properly washed also can spread disease. Gerba
recommends rinsing dishes with boiling water. Rinsing with water
straight from the lake and letting the dishes dry won't eliminate Giardia
and Cryptosporidium, Jordan notes. Many species of bacteria and
protozoa retain water in their cell structures and can remain viable for
a long time on dry surfaces.
Go Out and Have Fun
OK, lets put all this into perspective. Remember that more than
200,000 people visit the Boundary Waters each year and most have a great
time and stay healthy. So consider the experts advice and do your best
to keep your drinking water, hands, and dishes clean. Then forget about
the microbes and enjoy yourself. After all, we don't stop driving
because people die in cars. Instead, we drive defensively, use our seat
belts, and trust our luck. The same goes for the water.