Science Forums 2

[Michaelangelica]

Originally Posted by TheBigDog

There is more than enough water, and there will continue to be more than enough water. The issue is not quantity, it is distribution. People need to move to the water. Infrustructures need to be built to supply water to city centers. It is a matter of engineering and political will.

Bill

Here is a site with some sums
Human Appropriation of the World's Fresh Water Supply
A few quotes from it:-

< 1% of the world's fresh water (~0.007% of all water on earth) is accessible for direct human uses.
This is the water found in lakes, rivers, reservoirs and those underground sources that are shallow enough to be tapped at an affordable cost.
Only this amount is regularly renewed by rain and snowfall, and is therefore available on a sustainable basis.

The water cycle on Earth is essentially a closed system – we always have the same amount of water.

Worldwide, new dams (> 15 m ht) were constructed at rate of 885 per year during 1950-80, present rate is 500/yr, and future rate is estimated at 350/yr.
Over next 30 years, assuming size of reservoirs is unchanged, new construction adds 1200 km3 to accessible supply, and raises total AR in 2025 to 13,700 km3/hr.
Assuming average per capita water demand stays unchanged, but adjusting the pollution dilution for additional population, the total human appropriation in 2025 would be 9830 km3/yr, or 70% of estimated AR (compared to current 54%).
Clearly we are approaching the limit of available fresh water supply.

If all the Earth's water fit into a gallon jug, available fresh water would equal just over a tablespoon.
And the little bit we have is heavily used and abused by humans. We spend billions of dollars and tons of fossil fuels piping fresh water to semi-arid deserts such as Southern California only to flush it down the sewer at six gallons a wee. We befoul rivers and streams and oceans with all manner of toxic effluent, making them life-threatening to swim or surf in. We suck up ancient ground water supplies to grow yuppie tomatoes in November or water golf courses in the Sahara. As planetary stewards, we suck.

Surfrider Foundation Snowrider Project