Hike..sometimes in the land of lakes it's a water everywhere but not a drop to drink situation.not all of it is %100 pure,a dead moose up stream or pond filled with duckweed can really put you off. there is a spring at the end of my street here in South Minneapolis,Cold Water spring, that i would and have taken drinking water from before some of the beaver ponds i've paddled thru in the far north.the other dehydration problem is that it can sneak up on you.many years ago i was getting headaches during the day on canoe trips.i would take a Alka-Selzer for relief thinking it was brought on by eye strain,the long view over the lakes V.S. a close up computer screen.later i found out that headaches were the first sign of dehydration.after that i made a point of drinking lots of water,knocking back a extra gulp need it or not,the headaches went and never returned.and i guess it was the water and salts in the Selzer more than the aspirin in it that helped.