Sara,
I've drunk the Sierra waters for more than 50 years--straight out of the streams. In fact, my first drink in a Sierra river was the Merced River. I have never had a bad reaction, except two times I drunk out of non-Sierra waters and paid dearly for my stupidity, as my drinking spots were bad and I should have known better. Obviously, drink smart. If you see soap suds on the water, don't drink it. If you see, for example, campers washing pots in the pond at Trail Camp, don't drink it. (In fact, it is best to drink the water at the pond's inlet, rather than below.)
Bob Rockwell is our Whitney water expert, and he has posted many times on Whitney's highest water quality.
Do what you are comfortable with. It's your health and well-being, but I think most of us old timers on Whitney drink the water straight.
