Around the world, groundwater reserves that support more than 1.7 billion people are under threat. Scientists from McGill University and the Netherlands’ Utrecht University have published a new study in Nature showing that many underground water sources are being depleted faster than they can be replenished.

The threat is most serious in certain areas in North America and Asia. Globally, the world is using 3.5 times more water than aquifers can support. In certain areas in India, however, water is being used at a rate that is 54 times greater.

In the United States, critical areas of groundwater depletion include the Central Valley of California and parts of the High Plains, especially in the Texas Panhandle and western Kansas. Both areas rely on groundwater to irrigate agriculture and to support cities and towns. Other studies have shown that if current trends continue in the High Plains, some areas will be unable to support agriculture within a few decades. In California, during the drought from 2006 to 2009, farmers in the Central Valley used groundwater equal to all of the water in the largest reservoir in the U.S., Lake Mead.

In the Central Valley of California, groundwater use from 1925 to 1977 caused the ground level to subside 27 feet. Photo by US Geological Survey.

Over 99 percent of the world’s freshwater is underground. The scientists say that 80 percent of groundwater is managed in a way that is sustainable, but the areas that are overconsuming water are critical to agriculture. Possible solutions include more efficient irrigation, limits on water extraction, and promoting diets with less meat. Other studies have shown that it takes 2,400 gallons of water to produce one pound of meat.

Main image by Flickr user Agrilifetoday