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.
Equine nutrition
Water makes up between 62-68% of a horse's body weight and is essential for life. Horses can only live a few days without water, becoming dangerously dehydrated if they lose 8-10% of their natural body water. Therefore, it is critically important for horses to have access to a fresh, clean, and adequate supply of water.