Across the world, human civilizations depend largely on tapping vast reservoirs of water that have been stored for up to thousands of years in sand, clay and rock deep underground. These massive aquifers — which in some cases stretch across multiple states and country borders — provide water for drinking and crop irrigation, as well as to support ecosystems such as forests and fisheries.
Yet in most of the world’s major agricultural regions, including the Central Valley in California, the Nile delta region of Egypt, and the Upper Ganges in India and Pakistan, demand exceeds these reservoirs' capacity for renewal.
“This overuse can lead to decreased groundwater availability for both drinking water and growing food,” says Tom Gleeson, a hydrogeologist at McGill University in Montreal, Quebec, and lead author of the study. Eventually, he adds, it “can lead to dried up streams and ecological impacts”.
A nice world map of water stress accompanies the summary of the story that is available to the public free of charge. Look at the map and remember when you turn on the tap that you don't really have water up the ying yang, even though it may seem like it.