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Almost anywhere arid, the water underground, once largely ignored, has come to be seen as especially valuable as the demands of farmers have outgrown their supplies of rain and surface water. Groundwater has come to the rescue, and for a while it seemed a miraculous solution: drill a borehole, pump the stuff up from below and in due course it will be replaced. In many places, however, from the United States to India and China, the quantities being withdrawn exceed the annual recharge. This is serious for millions of people not just in the country but also in many of the world's biggest cities, which often depend on aquifers for their drinking water.
幾乎在所有的干旱地區(qū)，過去基本被忽視的地下水，如今因為農(nóng)民對水的需求超過了雨水和地表水的供應(yīng)而顯得尤其珍貴。地下水成了救命水，一時間，有了它，缺水問題似乎有了一個奇跡般的解決方法：鉆個洞，把水從地底下抽上來，到時候地下水自然又能得到補充。不過在許多地方，從美國到印度和中國，抽出的水量已經(jīng)超過每年能補充的水量。這對千百萬的人來說已經(jīng)是非常嚴(yán)重的問題，不僅在農(nóng)村如此，世界上許多大城市也是如此，這些城市里，人們的飲用水往往依靠地下的蓄水層。
The 20 million inhabitants of Mexico City and its surrounding area, for example, draw over 70% of their water from an aquifer that will run dry within 200 years, maybe sooner. Already the city is sinking as a result. In the Hai river basin in China, deep-groundwater tables have dropped by up to 90 meters.
比如，居住在墨西哥城及周邊地區(qū)的兩千萬人，70%的用水要從地下蓄水層抽取，而這個蓄水層將會在200年內(nèi)枯竭，或許比這更快。這個城市因地下水面的降低已經(jīng)在下沉。在中國的海河流域，地下深水層水位已經(jīng)下降了90米。
