For one four-day ascent of Mauna Loa in Hawaii, I knew that there was no running water on the volcano. In order to be self-sufficient, I had to carry all of the water that I needed for those four days. I figured that I could get by on one gallon per day, but that meant that I was carrying 32 pounds of water at the start, plus all the rest of my food and camping gear, plus camera equipment. I got some breaks and cool weather, so my actual consumption was maybe 75% of that.
Water is heavy!