California farms represent 8% of the US's agriculture value, and the Central Valley is where most of that growing takes place. However, as the state struggles with ongoing droughts, the groundwater supplies are dwindling at a frightening rate. According to satellite technology used by NASA, over a 6.5 year period the groundwater supplies in Central Valley leaked away by an amount equal to 63% of the capacity of Lake Mead, the nation's largest reservoir. With that much water disappearing, it is harder to replenish supplies when it finally does rain. Does this water debt mean a future food crisis?
National Geographic's Sandra Postel reports, "Rarely is groundwater use monitored, measured or regulated. This is true for most of the world, as well as for California's Central Valley-the fruit and vegetable bowl of the United States. Farmers in the 52,000 square-kilometer valley produce 250 different kinds of crops that together account for 8 percent of the nation's agricultural value. But thanks to the National Atmospheric and Space Administration's (NASA) satellite mission called GRACE (the Gravity Recovery and Climate Experiment), we're getting some excellent assessments of what's happening to water underground-and the picture is sobering."
According to analysis of data from GRACE, which can paint an accurate picture of changes in groundwater supplies, California's Central Valley lost 20.3 cubic kilometers, or 16.4 million acre feed of water between October 2003 and March 2010, most of it lost during the 2006-2010 drought. Additionally, northwest India, where the majority of the country's grains are grown, lost 109 cubic kilometers or 88.3 million acre feet of groundwater between 2002 and 2008 -- an amount triple the capacity of Lake Mead.
During droughts, farmers use more groundwater to make up for what isn't falling from the sky. However, dipping into groundwater supplies makes it that much harder for aquifers to replenish their stocks during rainy times. Farmers are pumping from their life savings account, but only spare change is returning to the piggy bank.
As the article from National Geographic points out, our future food security depends on sustainable use of freshwater supplies, primarily groundwater. Now that we have better technology to track use of groundwater supplies, how are we going to ensure that the resources are used wisely?
Policy changes are no longer just something to debate about when it comes to agricultural water use. It's something that absolutely must happen. But with a resource as precious and as precarious as water, lawmakers are nervous about change. We have the technology to implement intelligent irrigation practices, including dry farming some crops, drip irrigating others, using sensors to detect when watering is needed for yet others. Yet none of this is being used on a large scale. Instead, because of archaic and illogical water rights regulations, US farmers are encouraged to use more water than they need just to be sure they'll be allotted the same amount the following year when they might need it. We need to flip that so farmers are encouraged to take up smart water practices and use only what they absolutely need.
As Postel pointed out last Fall, "With modern satellite capabilities and new modeling and monitoring techniques, it is now possible to know what is happening to our water supplies underground. The picture is not good. The challenge now is to encourage the adoption of more efficient irrigation systems, more appropriate cropping patterns, and other measures to bring the world's groundwater accounts into balance. The future food security of hundreds of millions of people depends on this."
The warning may sound a little shrill now, when your local supermarket is stocked to bursting and your local farmers' markets never fail to appear each spring. But if you walk into a food market and find next to nothing on the shelves, groundwater depletion due to dumb agriculture methods will finally loom as large an issue as it should.