When getting water to pump through a water filter or add iodine tabs for treatment, lower the number of pathogens by collecting the water from a still pool or center of the lake where the bacteria and amoebas will have had a chance to settle out. Never collect water from the inviting froth of waterfalls. Some wilderness travelers get water from the center of lakes and forgo treatment! Although such practice would be unwise as a regular regimen, it may help in a pinch.
Tom Valone, Founder