[pct-l] Giardia Myth... or truth?

[Eric Lee (GAMES)]

Timmy wrote:
>
On a recent trek of the Uinta Highline Trail in Utah my friend mentioned that there was a story out there that water tumbling over rocks for 20 feet or more would be "pure", anyone out there heard this story or better yet have links to more information in direct relation to this story?
>

That is definitely a myth.

I don't have the link handy right now, but I once read a study of backcountry water sources that showed that the least pathogenic water tends to come from the top two inches of (reasonably clean) lakes, since that water has been thoroughly bathed in ultraviolet radiation from the sun.  I'll see if I can find the source and give everyone the link.

That said, if I have the choice between a lake or a swiftly-moving stream, I'll generally choose the stream because streams on steep mountainsides (at least in Washington) tend to have originated from high, inaccessible places where there aren't any humans, cows, or horses to foul the water.  That's just my flawed intuition, though, and it's probably not backed by any scientific evidence.

Eric