True - however, unless you're strong and in shape you will struggle carrying something like 30-40lbs of water in scorching heat. More exertion means more sweating, hence wasting precious body fluids. Getting a suitable container and/or a backpack large enough to accomodate it might be a problem even if you have plenty of water available.

Also, drinking enough water could be physically difficult if not impossible. FM 21-76 says a person doing hard work in 43°C requires 19 liters of water per day. That's a lot. Drinking like 1-2 quarts of water per hour to prevent dehydration is likely to upset the stomach after a while. Again a bad thing to happen when you're close to dehydration already.

In my own modest experience, the only solution in the desert is to limit hard physical activity to the cooler hours of the day - dusk, night, morning. During midday your only option is to stay still in shade if you want to last more than a couple of days.