Any picture from space shows that Earth has water, water everywhere. But finding a glassful to drink is another matter. Americans eagerly grab a pricey bottle of water at even the hint that what comes from their tap might be tainted or just not tasty.
Water is like land: Nobody is making any more of it. But, then again, there's no need. Water is never "used up": It's the ultimate recyclable, constantly changing forms and locations between glacier, cloud, river, pond, ocean, or underground aquifer.
Of Earth's plenteous supply, only 2.5 percent is fresh water, suitable for agriculture and consumption. Still, that should be ample for humanity if it were uncontaminated and universally available.
Yet most of the world struggles with serious aqua issues. The World Health Organization estimates that about 1.1 billion people - more than 1 out of every 6 people on the planet - don't have clean drinking water. It's also estimated that in developing countries, the average woman walks nearly four miles each day to fetch water for her family. And officials attribute more than a million deaths per year to lack of access to clean water and poor sanitation caused by water problems.
At the turn of the millennium, the United Nations set a target to cut in half the number of people without access to clean water or sanitation by 2015. As the years tick by, that target looks more and more difficult to hit.
To highlight water issues, the United Nations has designated Wednesday as World Water Day. This year it also coincides with the end of a six-day World Water Forum that has brought thousands of people from governments, nonprofit groups, and businesses in more than 100 countries to a conference in Mexico City.
This World Water Forum seems to be (pardon the expression) a watershed moment for finding solutions.
In some countries, municipal water systems lose up to 40 percent of their water on the way to households because of leaks in canals and pipes or illegal connections. Government mismanagement has prompted a big push in recent years toward privatization in some parts of the world.
But turning water supplies over to foreign corporations has also backfired, especially in Latin America, where "water wars" have emerged. After peasant protests, Bolivia sent French company Suez packing for failing to provide promised fresh water and sewage systems. Water privatization protests have raged in Argentina and Uruguay, too.
The challenge for citizen activists now is to find creative solutions that include watchdogs on whoever provides service. And privatization may still prove effective in other settings.
Expensive water projects, such as massive dams, need honest vetting to ensure they will be cost-effective. The need for mega-projects will diminish if wasteful practices in farming, which consumes 70 to 90 percent of humanity's water use, can be reduced. Meanwhile, small projects at low cost can have big benefits: Moving taps closer to villages increases school attendance as children no longer have to fetch water.
Some activists want access to water to be declared a "human right." It's clearly a human need, one that no one should be denied. And it's a precious resource, one that needs our best stewardship.