It's become commonplace in the sustainability world to say water is the oil of the 21st century. But it may be more accurate to say it's the new carbon. The problem is not about absolute scarcity--after all, the world's supply of water has remained constant since forever. Instead, we must allocate the resource fairly among competing human needs such as industries, agriculture, and cities. And the solutions have to do with finding efficiencies and closing loops to achieve "water neutrality"--when an enterprise returns the same amount of clean water to the world as it uses.
According to Joel Makower and the folks at GreenBiz.com , in their new State of Green Business report, Coca-Cola  is one of the biggest companies to announce a water neutral goal. By 2010 they pledge all their manufacturing facilities will return all the water they use to the environment, clean enough for fish and farms. GE  has a 20 percent reduction  goal for freshwater by 2012. IBM  is investing in a new water management resource center. Frito-Lay  has cut water 50% since 1999.
But the challenges go far beyond business. China, South Korea, and Saudi Arabia have all taken steps to lease agricultural land in Africa. Water is the main reason these countries can't grow enough food for their people. According to the BBC News ,"When water availability drops below 1500 cubic meters per person per year, a country needs to start importing food, particularly water intense crops." 14 countries will cross that line by 2030.
And here comes another parallel with carbon. In the UN and elsewhere, a global water trading scheme  is hotly debated, similar to one already in use in drought-plagued Australia. Is water an industrial resource, an overly subsidized government commodity, or a priceless human right? The answer will be worked out in court if we're lucky, on battlefields if we're not.
Image: LIFE magazine archive