These numbers are right-on! One pound of DRIED rations, per person, per day, and one gallon of drinking water, per person, per day, under normal conditions, meaning temperatures around 72 degrees F, doing "normal" exertion (walking, but not running, working, but not strenuously). When exerting strenuously, double the water, and when in hot weather, double it, again.
Now note, this is enough water for surviving on DRIED food, and not exhausting the body's resources. Yes, you CAN get by on one quart of water, per person, per day, but if you are also eating DRIED Food, you will have parched mouth, and be VERY uncomfortable! If you can get fresh plant food, with water within it, you can probably get by on that... OTHERWISE, you will begin dehydrating (and that's bad)!
Also note that, in a hot desert (two gallons of water, per person, per day), when doing strenuous work (four gallons, per person, per day), that this includes enough water to COOK with (and also a modicum to wash with, occassionally). If you are doing no cooking, and no washing, you can get along with a bit less (and about one quarter that, for short periods, although the risks of heat exhaustion & stroke go up, and the body begins to dehydrate).
Also note that, when low on water, the eating of fat is to be avoided! Lean meat can be eaten (and if cooked in some broth is very good for you), but that breaking down the fat, in the body, sucks the water out of it, as water is necessary to metabolize the fat!
Surviving on dried rations, high in nuts and fat (as granola, nuts, trail mixes, etc., usually are), with only one quart of water, per person, per day, will get you killed. It is possible, in the short run, but expect to lose body weight (and more importantly, muscle mass), dehydration, and generally weakening yourself. You might survive, but it's a lousy idea to try it!
One gallon of water, per person, per day, doubling that for strenuous exertion, doubling for heat, is the amount that a human needs. I believe that the DMG says that a horse being fed with a Murlynd's Spoon needs four times that much, IIRC (you can look it up). With FRESH food, maybe you could halve that, but the cooking would require some water...
Lizards mostly eat their foods raw, so no cooking. They mostly eat insects, IIRC, so that adds some fresh water (eh, ichor!) to their diet, which is low in fat, so multiply by your 16x, or whatever, then halve that, due to low fat diet & no cooking, and cold blooded metabolism. That seems about right, to me...
