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December 2nd, 2014
Via The Financial Times, a new report on the global water crisis:
Crucial supplies of water in China, the US, India and other major economies are dwindling so fast that the threat to the world’s water security is far worse than is commonly understood, a prominent hydrologist has warned.
The groundwater stored below the earth’s surface in soil and aquifers accounts for up to one-third of the water used globally and is the main source of water for more than 2bn people.
It accounts for around half the irrigation water used to grow the world’s food and is an especially important reserve during serious droughts, such as those gripping California and Brazil at the moment.
But it is being pumped out so rapidly in some of the driest regions that it can no longer be easily replenished naturally, according to research by Professor Jay Famiglietti, senior water scientist at NASA’s jet propulsion laboratory at the California Institute of Technology.
“Many of the largest aquifers on most continents are being mined,” Prof Famiglietti wrote in the latest edition of the journal Nature Climate Change.
“Without a sustainable groundwater reserve, global water security is at a far greater risk than is currently recognised.”
The affected regions include the North China Plain, the High Plains and Central Valley aquifers in the US, Australia’s Canning Basin and the aquifers beneath northwestern India and the Middle East.
Nearly all the aquifers lie under important farming regions, highlighting the risks posed to economic growth as well as the environment.
In drought-struck California, for example, the Sacramento and San Joaquin river basins have been losing about 15 cubic kilometres of water annually since 2011, more than all the water the state’s 38m residents use for domestic and municipal purposes in a year.
Groundwater pumping in California’s Central Valley, one of the most productive agricultural regions in the US, accounts for more than half the losses, says Prof Famiglietti, who has used Nasa satellite data to pinpoint regions of greatest concern.
Even though groundwater is vitally important, it is poorly monitored and managed compared with more visible sources of water in reservoirs and rivers.
This is especially true in developing countries and the result has been a virtual free-for-all in which farmers and property owners can drill wells as deeply as they like to extract groundwater.
In parts of the Middle East, north Africa and South Asia, it has become common to drill down more than 2km to reach groundwater, says Prof Famiglietti.
Some countries, such as India, have also subsidised the cost of electricity for pumping to boost farm productivity.
Efforts to reform the problem are under way in some places, including California, which earlier this year passed new laws that will require better management of groundwater supplies.
But governments need to do much more globally to address the problem, said Prof Famiglietti, especially since climate change is likely to complicate the challenge in coming years.