Filter your water or not?

[oldranger]

I think maverick has it right about the Kern. Besides best as I can tell from reading the map the JMT and PCT cross several tribs that feed into the Kern. Also despite our preference for moving water as I recall it giardia are slightly heavier than water so risk of picking it up is greater where it is churned up in a stream compared to a lake. George can confirm or deny that point but I am certain that he will not claim ignorance! Also as I recall in the eighties 2 backcountry rangers got giardiisis (or however you spell it). I never used a filter until I stopped being a ranger. Now I figure for 7 to 11 oz I can avoid the risk, which I admit is infinitesimal with any single cup of water but the more you drink the more the odds are to catch up with you. The other thing I seem to recall is that a percentage of the population are asymtomatic carriers and basically immune to the little critter. George, help me here!

Mike

[rlown]

i know that filters take giardia out of the water pumped. Does anyone know about filters effectiveness on e. Coli?

Russ

[trav867]

You'd have to check the specific filter, but I believe that most filters are like 99.99% effective against all bacteria (e. coli incuded). In order to kill viruses however, you need a chemical like bleach or iodine. Boiling kills pretty much everything.

[gdurkee]

OK. The Kern in Sequoia Park gets a lot of traffic -- both hikers and stock. The trail crew camps there for weeks with about 10 head. In addition, there's a fair amount of private stock traffic through there. It also gets a pretty good amount of hiker traffic from the Hot Springs up. That's one area I'd be kind of cautious about just drinking the water out of the main river. Odds are, it's OK, but the risk is somewhat higher than other water sources. Also, there are definitely beaver there. Not completely sure of the history, but I think they were introduced in the 30s. There's no eveidence that they're any greater source of giardia in that part of the Sierra than any other mammal, but they do live in the water so any cysts they do carry would go directly in.

There's an unpublished paper that finds that something like 7% of horses in Yosemite carry giardia. The same research team also measure the amount of, ummmm, feces they left per mile of travel and, from that, derived the number of giardia cysts they shed. Although only 7%, it's a huge amount of giardia potentially reaching the rivers and streams. It's a little suspicious it hasn't been published. But, I have the raw data and it's public domain because it was done in a National Park. As soon as Nature Notes comes back up (down for a remodel), I'm hoping to publish that as an article.

Mike's correct on asymptomatic carriers. I've read several percentages, but something like 20% of the population carry giardia but have no symptoms. I'm less sure of "safest" place to drink. Dr. Bob Derlet thinks the top 3" or so of a lake is best because of the UV light hitting that. In the great scheme of things, giardiasis is pretty rare in either Yosemite or Sequoia Kings. Definite cases, but only a few per season. Mostly, it's cows and not washing your hands after taking a crap (or, I suppose, cow tipping).

E. Coli itself is not the problem, usually, but is an indicator of other pathogens that could be there as a result of feces in the water.

g.

[maverick]

GD thanks for the horse info, even more reason to be wary of routes where stock
travels!

[rlown]

Thought i'd post this cross ref to Hetchy's PCT adventure. I've been following his postholer log, and he appears to be making great time against plan, despite his bout with Giardia. http://postholer.com/journal/viewJourna ... ent_id=414

I think he's carrying a filter and clorox, but he'll have to tell us more when he finishes/reports.

[gregw822]

I've been a high Sierra backpacker for many years. I've never filtered my my water. I don't even carry a filter. I've never met anyone who picked up giardia in the Sierra. In fact, I've never known anyone who knows anyone else who has suffered from drinking the water in the Sierra. Rangers will tell you to filter the water, but I think that's just Forest Service policy to eliminate liability.

[ERIC]

Here is a link to a previous discussion on the subject:
viewtopic.php?f=1&t=1968&p=12599&hilit=giardia#12599

Here is another link with a lot of info:
http://www.yosemite.org/naturenotes/Giardia.htm" onclick="window.open(this.href);return false;

And another:
http://www.highsierrahikers.org/Derlet-" onclick="window.open(this.href);return false; ... n-2006.pdf

Other previous discussions:

viewtopic.php?f=9&t=113" onclick="window.open(this.href);return false;

viewtopic.php?f=15&t=3092" onclick="window.open(this.href);return false;

http://sierrapacktrip.proboards.com/ind ... thread=483" onclick="window.open(this.href);return false;

[rlown]

ok.. i was just crossposting Hetchy's experience. nothing more. If you don't filter, i'm not judging. Personally, i filter all my drinking water. For cooking uses, it's boiled. thanks for the backpost references though, Eric.

[ERIC]

ok.. i was just crossposting Hetchy's experience. nothing more.

Ya..I know.

thanks for the backpost references though, Eric.

You're welcome.