The guy to the right was wandering down from a hike in the hills with the remains of a 21/2 gallon water container under his arm.
We went with 50 gallons of water for Wednesday through Monday. The car was air conditioned, so we were really there 4 days plus Wednesday afternoon and Monday morning for teardown. We went through 25 gallons, including two baths (you can wash a person with short hair with about a quart of water. We used a gallon between the two of us each time, which felt like decadence). We drank about 2 gallons per person per day, the rest for washing and tooth brushing and such.
Take a bottle with you every time you leave camp. There's always something cool to go see or do or get distracted by, and you will be uncomfortable if you're not drinking all the time.
We froze nearly everything, including lots we didn't plan on; I bought 100 lbs of dry ice before we left, 50 lbs per cooler, and lots of stuff was too cold. Next year we'll take a bunch of frozen veggies, probably freeze some made up pastas (pesto worked really well), some yoghurt, and keep one cooler with just regular ice in it for the sensitive things.
But the dry ice was handy for refreezing things; our neighbors had brought several bags of popsicles that had melted because they tried to keep them cold with regular ice. A little dry ice and they refroze quite nicely, we handed them out at the camp center the next day, where they were well received.
The temperature didn't get all that far over 100, mostly it was in the '90s. With weather like that you can take onions, avocado, tomatoes, citrus and other tropical fruits, and get several days out of them without refrigeration.
Salt! We nearly forgot this, and got some in Reno. We would have been seriously hurting without it.
Wednesday, December 30th, 1998 firstname.lastname@example.org