Across California’s vital agricultural belt, nervousness over the state’s epic drought has given way to alarm. Streams and lakes have long since shriveled up in many parts of the state, and now the aquifers — always a backup source during the region’s periodic droughts — are being pumped away at rates that scientists say are both historic and unsustainable.
The shrinking of the aquifers has added a new dimension to the concerns over the historic drought that continues to shatter records across the Western United States. The parched zone now spans a dozen states and nearly 600 counties, from southern Texas to the northern Rockies, and includes fields and grazing land that produce a third of the country’s beef cattle and half of its fruit, vegetables and winter wheat. Prices for most of these products have soared this year.
Throughout the western United States, a network of Global Positioning System (GPS) stations has been monitoring tiny movements in the Earth’s crust, collecting data that can warn of developing earthquakes.
To their surprise, researchers have discovered that the GPS network has also been recording an entirely different phenomenon: the massive drying of the landscape caused by the drought that has intensified over much of the region since last year.
The recent uplift is consistent across the West, and consistent with recent declines in precipitation, streamflow, and groundwater levels. With a great weight of water removed, the crust is rebounding elastically across the whole region.
The median rise across all the western GPS stations has been four millimeters, just under a sixth of an inch. But the Sierra Nevada mountains, which have lost most of their snowpack, have risen 15 millimeters—nearly six-tenths of an inch.