(Kelly of the Clue Crew reports from  White Sands National Monument, New Mexico.)  In desert conditions, you need at least one gallon of water per person per day, have reusable water containers, & a tincture of a small percentage of this to purify the water
... Water stored in thoroughly clean plastic or glass containers can be... [DOC] [TLE] Potable Water | Burning Man [PAR] The bottom line: 1.5 gallons of water per day per person.