Dan! "Being able to carry food and water for a week in arid areas like Big Bend NP or Coronado NF is the goal." That would be desert. I carry and use a purifier. Just to clarify. If there has been rain or snow there may be springs available, but often they are dry. If springs are running and I don't have to carry as much water I could carry more food and stay out in the remote back country roads longer. It just depends on the weather.

jankdc! Thank you for sharing your experience. Under what circumstances were you carrying 4 gallon of water?