Paul swallowed, suddenly aware of the moisture in his mouth, remembering a dream of thirst. That people could want so for water they had to recycle their body moisture struck him with a feeling of desolation. “Water's precious there, ” he said.
From the novel Dune by F. Herbert (1965) 2
Just as an animal can't live without food, so too can it not live without water, a fact that Frank Herbert used to enormous effect in his classic work of science fiction, Dune. When I first read this book and journeyed with Paul and the other characters across the sands of the desert planet of Arrakis, I repeatedly felt thirsty. Gradually, through Herbert's absorbing prose, I became aware of the enormous role that water and thirst play in our lives.
There are several reasons that we may not always be aware of the prominent role of water and thirst. First, for most of us most of the time, water is easily and abundantly available. Schools, businesses, and public parks have water fountains; grocery stores and street vendors sell bottled water and other thirst-quenching beverages; restaurants serve water; and virtually every house and apartment contains a water faucet. Second, because many foods contain at least some water, eating can help to satisfy thirst. For example, a person is unlikely to feel thirsty after eating large amounts of lettuce-lettuce is 96% water. 3 Thus we may not always be aware of how much water we need or of how powerful thirst can be; we rarely reach a state of extreme thirst.
Nevertheless, loss of water can occur very quickly. For example, when sweating, people typically lose about 1 quart of fluid per hour, which is about 2% of the total fluid contained in our bodies. 4 Given this fact, and given that