I did find this. It attacks the premise of the question you proposed:
"
The fact is, you cannot ration water in your canteen any more than you can ration gas in a car's tank. If you have a quarter tank of gas and sixty miles to go to get to the next station, giving the car "a few sips" cannot do it. Instead, you use the available gasoline conservatively by driving slower, coasting downhill, and avoiding rapid acceleration. It is the same way with the body. By waiting until cooler times to walk and limiting physical activity (such as not digging several holes for stills) the available water is used wisely.
It is important to drink enough to keep the brain hydrated. The recommended sipping and wetting the lips is a misuse of available water. Such rationing causes the less important cells of the body to pirate the water away from the brain, which will result in irrational decisions and increased body temperature. "
http://ridgerunnersurvival.tripod.com/da1.htm
It goes on to talk about a foolish woman who died of thirst with water still in her canteen. The premise in that article and what I have heard elsewhere is you can not expect to ration water like you can food (basically since the body has not water supplies to tap open, no matter what one's fat girlfriend might say). We can control activity, and try not to over-exert and lose water needlessly.
I gauge my canteen by weight or I peer into it. Often they are clear. I have no experience with camelbacks other than learning that taking water from a man's teat is awkward, no mater the desperation. ("You have to bite it. Yeah! that is nice. Now touch yours.")
Seems the best method is if you thirst, drink; if you want for drink, find it.
Afterthought: That article does have this:
Even if you can identify edible types, most mushrooms contain fewer calories than they take to digest, which do not make them valuable as survival food. It is protein that does not move, and a good find for a hungry, lost mycologist.
thanks!
