George Will thinks some folks underestimate the importance of beer.
UPDATE: Professor Bainbridge thinks it's really "No Wine, No Civilization." Redheadlaw7 likes that story better.
The only common drinks that produce a net loss of fluids are those containing alcohol -- and it usually takes more than one of those to cause noticeable dehydration, doctors say.
Alcohol stimulates urination over and above that induced by just drinking water.
Also, you don't have to boil the water to make wine, do you? That could be an additional reason why beer was more effective at hydrating city masses safely.
The following is from a tale related by the Chief Curator of the National Park Service, and printed in no less an authoritative source than "Oceanographic Ships, Fore and Aft", published by the Oceanographer of the Navy. It has to do with a cruise of the 204-foot frigate USS Constitution, commonly known as Old Ironsides, in 1779. The quote:
On 23 August 1779, the USS Constitution set sail from Boston loaded with 475 officers and men, 48,600 gallons of water, 74,000 cannon shot, 11,500 pounds of black powder and 79,400 gallons of rum. Her mission: to destroy and harass English shipping.
On 6 October, she made Jamaica, took on 826 pounds of flour and 68,300 gallons of rum. Three weeks later the Constitution reached the Azores, where she provisioned with 550 pounds of beef and 6,300 gallons of Portuguese wine.
On 18 November, the ship set sail for England where her crew captured and scuttled 12 English merchant vessels and took aboard their rum.
But the Constitution had run out of shot. Nevertheless, she made her way unarmed up the Firth of Clyde for a night raid. Here her landing party captured a whiskey distillery, transferred 40,000 gallons aboard and headed for home.
On 20 February 1780, the Constitution arrived in Boston with no cannon shot, no food, no powder, no rum, no whiskey. Just 48,600 gallons of water.