I've done many tours in extremely remote places -
From the deserts of Arizona and Nevada up to the Northwest Territories and the Yukon.
There are three basic positions on water that have changed over the past twenty years.
1. Most people can drink most natural water without treatment.
2. Flowing water needs to be treated, but campground and town sources are O.K.
3. Even many park and rural water sources fail to meet current water standards.
Regarding #1 -
here is a scholarly article on the incidence of Giardia and the incidence of effects:
http://www.yosemite.org/naturenotes/Giardia.htm
The reality is that federal water safety levels permit low levels -
And we all consume them without harm
Thus, water close to a source is most likely O.K.
Regarding #2 -
Flowing water needs to be treated less because of giardia
And more because of cows grazing on public lands - e-coli, bacteria, pesticides, etc.
As water standards have increased, forest service campgrounds and local parks have been forced to cap their wells because they cannot justify the cost to upgrade. This is a real bummer for cyclists. I can't tell you how many campgrounds that used to have drinking water 15 years ago no longer have it.
Regarding #3 -
Even campgrounds that do have water will now have signs saying that it must be boiled. This usually reflects more stringent testing standards - although it can be a localized contamination. Doesn't hurt to ask in town at the forest service or BLM office about water sources - and if restricted - the nature of the problem. I've had rangers tell me that one test all summer was barely over the limit - a level which was perfectly acceptable in the 1980s.
Of course with any of these situations - the choice rests with you.
As for treating water -
The best treatment is:
1. A water filter - Katadyn Hiker - lightweight and easy to use. Best taste.
2. Boiling - but you have to let it cool overnight - wastes a lot of fuel.
3. Iodine tablets - tastes yucky - good for emergencies -
take a couple of packe of lemonade to cover the taste.
Remember that cow tanks are a great emergency source of water -
Look for the windmills - if it's public land, it's fine to go out to them -
BUT - make sure to reclose any and all gates!!!
No - you don't drink from the cow tank -
You get water from the outlet pipe as the windmill is pumping it up the well.
I have had some of the coolest, sweetest water at cow tanks.