Sierra Water

[gdurkee]

Quintinc:

Well, if you'll excuse the expression, it's all a crap shoot anyway. Derlet (Note: I don't want to hold him to my imperfect memory, so take my quotes of him with some unknown margin of error...) said that only about 5% of stock in the areas he sampled show giardia in their manure. That's not huge, but it's still there. Then the cysts have to get from the trail/meadow into the water, so that cuts down on exposure even more. Still, there's a potentially increased risk around areas that receive stock use.

What I do is look for side streams coming into a main canyon or springs. I always favor those water sources over a main river. Also, as I'm sure you've noticed, stock tends to crap & urninate at streams crossings when they stop to drink. A map can pretty much tell you whether there's stock grazing above you -- if there's a trail, there's a good chance of it.

So anyway, the risk appears to be small, even with stock use. Once again, though, if there have been cattle in an area, that ups the risk considerably for several years after.

Good luck,

George

[JM21760]

In 30 years, I was only bit once. The only explanation I could come up with, was Giardia. However, the onset was within 5 or 6 hours, and I was under the impression that there was a incubation period, longer than that, once ingested. Upon walking around the area I was camped, (Upper Cathedral Lake, Yosemite) I found the trail on the east side of the lake to be fairly swampy, with water oozing out of the turf, and into the lake. This trail was also covered with horse apples galore. On a side note, when I awoke with boiling bowels in the middle of the night, was the same exact moment a sow and 2 cubs decided to visit, and hang out. I was able to hold out though, and lived to finally get out of the tent. It was not an easy endeavor to be honest.
Otherwise, I try to draw my water from headwater country, snow melt rills, or unfrequently traveled areas. I've never had any problems in over 3 decades, but for that moment in the Yosemite back (?) country. I think if you are careful, and use common sense, you'll be fine. Just be sure to evaluate the source. If you're in a popular spot, yeah, you bet I'd filter. But, if you're running high basins, and trailess watersheds, I think the risk is almost nil.