In emergency, if you cannot locate water, you are going to be in deep trouble as you may not able to survive more than couple of days without any water. The Ranger Digest has a page on water – it has some basic water facts, tips for locating, filtering and purifying water:
… So what do you do if you’re dying of thirst and come across some water that you’re not sure is safe to drink? Well, it’s entirely up to you and depends on how desperate you are for water. But if you’ve been wandering around for days without any water and you’re starting to feel weak, delirious, and downright desperate for something to drink. You got a choice, you can either die from dehydration or risk dying from unsafe/contaminated water.
Now personally, if I was wondering around for days without any water and suddenly came across some, provided it wasn’t discolored or have a strange odor� I’d drink it. Why? I’d rather risk drinking unsafe water and hope it would give me enough strength to travel/continue on just little bit further and longer than to give up and die right there on the spot from dehydration. After all, whether you feel ill after drinking some suspected contaminated water or not, if it gives you the strength to place one-foot-in-front-of-the-other and move on, your chances of surviving and being rescued before it actually overcomes you with severe illness is greater then giving up and lying down somewhere and dying, don’t ya think? Sure it is! …
Filtering & Purifying Water – [The Ranger Digest]