treating water in the alpine

DG, snow worms are only on glaciers and tend to come out in the spring (and typically in the late afternoon before dusk). On snowfields, there are many little creatures for sure, but usually it isn't so bad especially in the winter. Here's a blurb on wiki about them: en.wikipedia.org/wiki/Ice_worm I find these worms kinda fascinating.

I find myself rarely filtering unless it is in summer and/or out of state where I am not as familiarized with the trails, roads, etc. In the winter, I do find myself drinking unfiltered water out of lakes (out of the outlets), even ones I'd never dare do so in the summer. No ill affects. I've drank water everywhere in the Olympics, even near sea level. Ha. When white water boating I've pretty much drank out of every creek and river in the state. I sometimes wonder how real getting sick from water is on the west side of the cascades? Sure it happens, but it must be rare as every person I climb as ski with does as I do with no ill effects.

Jason I'm a little confused by the overlapping parts of your statement. Do you drink water in the Olympics @ sea level only in the winter or also in the summer? Do you drink out of any stream you're boating in the summer? Is the decision threshold that the water is fast moving?

FWIW, I've since done a little reading on Giardia (not the only baddie, but culprit #1) and it appears that (according to medical research) the amount of cysts required to produce an infection is pretty low, enough that an errant mouthful of lakewater will cause it. So the logical conclusions is that when you swallow that wave in Lake Washington, it's either (shockingly) clean or you're already immune due to multiple previous exposures (most likely to occur under age 5).

... according to medical research) the amount of cysts required to produce an infection is pretty low, enough that an errant mouthful of lakewater will cause it.  So the logical conclusions is that when you swallow that wave in Lake Washington, it's either (shockingly) clean or you're already immune due to multiple previous exposures (most likely to occur under age 5).

That is what I was taught in my parasitology courses. If you grew up drinking wild water or if you had been infected as an adult, the chance of reinfection is low. The biggest Giiardia outbreaks have been at western ski areas where drinking water was contaminated with sewage water; the other biggest source of Giardia infections was from pet dogs defecating along streams and then people, not previously infected, drinking from the stream. But rest assured, many (if not most) wild animals harbor Giardia as well, from elk to marmots. These Giardia are nominally different species but a colleague of mine used to have his new previously uninfected graduate students drink them in coffee to ascertain/demonstrate they were pathogenic and when passed indistinguishable from Giardia lamblia (human Giardia). Whether this info is currently true I don't know; but the take away for me was if you were a country boy, drink the water, if an urban naif, filter it. All this assuming, as mentioned above you are not in the vicinity of Camp Muir or some other camp or along a well traveled route or just downstream from Paradise .

in my parasitology courses. 

That is so cool.

I use tincture of iodine and I've considered how interesting it would be to experiment with various concentrations and temperatures of solution and figure out just what it takes to destroy the cysts.  I'm not smart enough actually do that experiment, but it would be nice to know.  Do I really need 7 drops?  Is 10 minutes enough time?  Anyway, formal exposure to parasite info is pretty neat.

What is the rationale behind distinguishing between lakes and creeks i.e. lakes are no-no and fast moving water is OK?Is the anaerobic flagellated protozoan parasite partial to lakes only?

I admit if I have to drink untreated water I will choose creeks over lakes but I do not have a reason for this decision.

My understanding is that giardia cysts are not buoyant, thus settle out in still water. Finally contracted giardiasis after fifty years, now using a steripen.