http://www.ecoworld.com/Home/Articles2.cfm?TID=37

Thirsty Planet

How much water have we really got? It would seem like quite a lot, since the earth's surface is 71% water. But appearances can be deceiving.

All the water on earth would fit into a cube not quite 700 miles on a side. If that seems like a lot, remember this includes oceans and icecaps. All the fresh water in the world, including icecaps and groundwater, would fit into a cube just over 200 miles on a side. And if you limit your water to lakes and rivers, all of them in the world would fill a cube a mere 36 miles on a side. Since the icecaps are frozen, and groundwater is replenished very slowly, this 36 mile cube, representing all the water in all the lakes and rivers of the world, is all we've got

Moreover, only about half the amount stored in Earth's lakes and rivers is replenished each year by snow and rainfall. This renewable amount is how much humans, plants, animals and ecosystems get per year to live.

It's not enough. Industrialized, developed nations consume far more water than developing nations, and the world is developing at a pace unprecedented in human history. Throughout Asia and Latin America, standards of living are increasing and with them, per capita usage of water. Currently an American or Western European uses four times as much water as someone in the developing world. What happens when 1.3 billion Chinese, .5 billion other East Asians, 1.1 billion Indians, and nearly 1.0 billion Latin Americans begin to enjoy a lifestyle that approaches western standards? More meat, which requires grain-fed livestock, more showers, more flush toilets, more factories, more irrigated land. There is not enough fresh water on this planet to allow the per-capita consumption of water in the western world to be matched by the rest of the world.

Water scarcity has become a big issue for environmentalists in recent years, because humans have been living beyond their means for decades, and the day of reckoning is not far off...............