I've posted before about the idea that we may not need as much water as is sometimes prescribed. This 8 glasses a day thing is a myth and in fact thirst is the best guide to how much you need.
Mark Sisson has put up a good article on this idea - Drink Less Water?
It got me thinking that when I am hillwalking, water is the heaviest thing in my pack. I know someone that sets off with 4 litres - and that is a huge extra weight. Personally, setting off with 2 litres of water, it is rare that I will have drunk it all even at the end of an 8 or 10 hour walk unless it is really hot. So it is just extra weight to heft around.
Of course I could drink from streams but I've not got that hardcore yet. I also remember once seeing some guys camping near a stream and taking water from it, then 100 yards away, seeing a rotting dead sheep lodged in the rocks at the bottom of a waterfall just upstream. I'm sure they were ok but the memory of the smell of that sheep still lingers.