Survival skills
A human being can survive an average of three to five days without the intake of water. The issues presented by the need for water dictate that unnecessary water loss by perspiration be avoided in survival situations. The need for water increases with exercise.
Feeding Everyone No Matter What
As a backup plan, it is even possible that humans could eat this predigested biomass. In a sun-obscuring crisis, stored food would last the human population less than one year. The book shows how many of these solutions can be ramped up in less than one year.