DTape is correct.
Growing up in a place called "waterfall valley" we never carried water except for the last "dry" 1000-1500' going to the top of a mountain (we started at 3000' and ended at 7000/9000')
(day walks)
Here in Australia I have carried up to 6 L in dry areas or where unreliable sources are.
I am convinced that drinking water is a bit like eating. The more you do the more you need. (up to a point...)
On a hike last year, (Olympic National Park) we arrived at a spot where there was a water source marked on the map however it had been sealed up and a few people around camp told us there was no water there.
I had about 1.5L left and was happy to see the night there and hike out the remaining 6-8 miles the next day with that. One of my mates who constantly drinks from a tube (20 years younger than me and supposedly fit for going to the gym 2-3 times a week) absolutely lost it because he was down to a bit more than 2 liters.
As it happen we saw some dear nearby (it was late in the afternoon) so we knew there had to be water, and found a small source about half an hour later.
BTW, I drink about 2 L a day max (outside meals) even at 100F.
Franco