The sensation of thirst is central to our very existence.  It is, as Rullier said in 1821…’le sentiment le plus vif et le plus imperieux de la vie’..  The gratification of thirst is universally held to be one of the pleasures of life; the sensation cannot be ignored, and if water be lacking, thirst comes to dominate our thoughts and behaviour; it drives us to the utmost endeavour and achievement…or to the depths of despair and degradation. 
J T Fitzsimons(1979) The Physiology Of Thirst And Sodium Appetite.  Cambridge University Press, Cambridge.

Water has long been a critical problem for poor people.  In many places, access to clean water all but defines poverty.  The consensus among experts in that 1.4 billion people in the world do not have access to safe water (…roughly one in four) ….  If you live in North America or Japan, you use on average 158 gallons of water a day…If you live in Europe you use about 80 gallons, and if you live in sub-Saharan Africa 2.5 to 5 gallons.
Bill McKibben (2003) Our thirsty future. New York Review of Books, vol 50 pp 58-60

‘Water!’
As  in the sea at a moment of desperate crisis his body changed, became able and willing.  He scrambled out of the trench on legs that were no longer wooden…….he came to the edge of the cliff and a solitary gull slipped away from under his feet…..He worked himself round on his two feet but the horizon was like itself at every point……He went around again.  At last he turned back to the rock itself and climbed down……When he was below the level of the bird droppings he stopped and began to examine the rock foot by foot….He saw water on a flat rock, went to it, put his hands on either side of the puddle, and stuck his tongue in.   His lips contracted round his tongue, sucked.  The puddle became nothing but a patch of wetness on the rock.
William Golding (1956) Pincher Martin. Faber and Faber, London.

I had to have water.  I brought my hand down and quietly undid the hasp.  I pulled on the lid. It opened onto a locker…… [he drinks from a can]

My feelings can perhaps be imagined, but they can hardly be described.  To the gurgling beat of my greedy throat, pure delicious, beautiful, crystalline water flowed into my system.  Liquid life, it was.  I drained that  golden cup to the very last drop, sucking at the hole to catch any remaining moisture.  I went, “Ahhhhhh!”, tossed the can overboard and got another. I opened it the way I had the first and its content vanished just as quickly.  That can sailed overboard too, and I opened the next one….I drank four cans, two litres of that most exquisite of nectars, before I stopped.  You might think such a rapid intake of water after prolonged thirst might upset my system. Nonsense! I never felt better in my life…
Yann Martel (2002) Life of Pi . Canongate Books Ltd Edinburgh