LiveScience: Fresh water. The planet has only so much to meet the needs of a growing world population. And global warming throws more uncertainty into the mix by increasing chances of extreme weather, such as more intense droughts in some places. Dry spells, such as the devastating drought that gripped much of the United States last year, come with economic costs in the developed world and deadly consequences in poorer countries. There is no secret source of water of the future. Conservation is the best answer,...