Our climate is changing, making polar ice, glaciers and icebergs melt, causing the sea level to rise — even threatening our famous historical and cultural treasures. That pretty much seems to be the story, reported again and again. But, worrisomely, there’s even more to be concerned about. We’re making the sea level rise even more than it would otherwise, by pumping too much groundwater. Yup, seems like we can’t do anything right.
It happens when water is hoisted out of the earth to irrigate crops and supply towns and cities, then finds its way via rivers and other pathways into the world’s oceans. Since 1900, some 4,500 cubic kilometers of groundwater around the world – enough to fill Lake Tahoe 30 times – have done just that.
In the last 100 years, sea levels have crept up 7 to 8 inches. Melting glaciers and other ice, as well as thermal expansion of the warming oceans themselves, are largely the direct cause. But groundwater extracted and running to the sea is responsible for another half-inch from 1900 to 2008, according to a Geophysical Research Letters article. The prediction is that sea levels will rise even faster in the next 100 years.
While gripped by droughts in much of the West, the U.S. has been responsible for about 22 percent of global groundwater draw in that same period, the study author, hydrologist Leonard Konikow reports. We’re pumping out water so fast that its not replenishing, reports Scott K. Johnson for ArsTechnica:
The Ogallala Aquifer, which extends from Nebraska to Texas, is a prime example. There, groundwater irrigation has made productive agriculture possible in an otherwise dry region. The rate of water use, unfortunately, is not sustainable. In some places, groundwater is pumped over 20 times faster than it is recharged by precipitation, and water levels have steadily dropped. Some refer to this as “groundwater mining” because it took some 30,000 years to fill the aquifer—once it’s pumped dry, it won’t soon refill.
California has even started pumping out water that fell to Earth during the Stone Age. It’s tough to weigh the risk of something as seemingly distant as rising sea levels against the immediate need for drinking and irrigation water. Yet if we don’t start doing exactly that we will be in deep trouble sooner than we’d like to think.