Drip, trickle, splash. Water is one of the most common substances in the universe, and our ocean-wrapped planet is blessed with a generous share of it. Unfortunately, 97 percent of that share is salty, and much of the rest is locked up in ice. Obtaining an adequate supply of freshwater has consequently been the focus of human ingenuity and passions throughout history. Water has been the prize (and sometimes the weapon) in conflicts around the world. Even in the century ahead, impressive gains in technological capabilities to find, transport and conserve freshwater may not be able to accommodate increasing demand, particularly in the developing world. Local mismatches between need and supply could push groups to violence, retard economic progress and devastate populations.

In the following pages, Peter H. Gleick of the Pacific Institute for Studies in Development, Environment and Security describes the magnitude of the world's pressing water problems in terms of skyrocketing usage and ominous limits to the known supplies. Sandra Postel of the Global Water Policy Project then narrows the discussion to irrigation, the single largest use for freshwater, and to the prospects for improving this vital agricultural technology. Lest anyone think that other options for staving off water shortages are lacking, we also consider a quartet of other approaches, including desalination, "bag and drag" transport, recycling and increased plumbing efficiency. A water crisis may be in the cards for some, but not if we act quickly to develop all the solutions at our disposal. --The Editors

   
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