By Hillary Mayell Grain being picked in a watered field in Sudan. Lack of water has been tied directly to food insecurity. Water tables are falling on every continent and major rivers are being drained dry before they reach the sea, according to a report by the Worldwatch Institute that draws a direct link between water availability, population growth and food security. The book was funded by the Wallace Genetic Foundation and the Pew Fellows Program of the Pew Charitable Trusts. Water tables fall Postel estimates that 40 percent of the world's food comes from irrigated cropland and she points out that historically, most irrigation-based civilizations have failed.
Problems associated with irrigated farming include water-logging, salting and silting.
The International Water Management Institute estimates that India's grain harvest could be reduced by up to one fourth as a result of aquifer depletion. The country's population reached 1 billion in August and is expected to add an additional 18 million people a year for the foreseeable future. Depletion of the Ogallala aquifer in the southern Great Plains of the United States has led to irrigation cutbacks in farming states Texas, Oklahoma, Kansas and Colorado have been losing irrigated land over the last two decades. Texas has lost irrigated land at roughly one percent a year since 1980. Water tables are falling in China almost everywhere that the land is flat.