Fast forward to yesterday (August 26, 2014), the Washington Post posted a story with this headline: "Why no one should freak out about the giant crack that opened in the Mexico desert." The Post reports:
The chair of the geology department at the University of Sonora, in the northern Mexican state where this “topographic accident” emerged, said that the fissure was likely caused by sucking out groundwater for irrigation to the point the surface collapsed.
“This is no cause for alarm,” Inocente Guadalupe Espinoza Maldonado said. “These are normal manifestations of the destabilization of the ground.”I'm sorry, no. These are not normal manifestations of natural activity, this is the result of human activity run amok. Just because Cthulhu isn't clambering out of the breach to wreak havoc on humankind DOES NOT MEAN we shouldn't be alarmed by the fact we've sucked so much water out of the ground that the surface of the earth is collapsing.
Barely a month ago NASA's Jet Propulsion Laboratory warned of 'shocking' groundwater losses in the Colorado River basin, a major watershed to the north of Sonora with similar climate and landuse. Using gravitational data from the satellite-based Gravity Recovery and Climate Experiment (GRACE) instrument, scientists found "the basin lost nearly 53 million acre feet (65 cubic kilometers) of freshwater. That's almost double the volume of the nation's largest reservoir, Nevada's Lake Mead. More than three-quarters of the total -- about 41 million acre feet (50 cubic kilometers) -- was from groundwater."
NASA's measurements of groundwater based on gravity. Areas in red show a deficit in groundwater, blue indicates surplus. Image Credit: NASA/JPL
The Post also reports that cotton used to be a major crop, but intrusion of saltwater from the Sea of Cortez caused some areas to become unusable for agriculture. However, there is still plenty of large-scale agriculture as evidenced by the Landsat image below.
Image Credit: NASA/USGS via SkyTruth
(Above) Hermosillo region of Sonora, Mexico, as seen by Landsat 8, on August 17, 2014. Bright green rectangles in the middle of the desert are irrigated fields. However, around the green fields, there appear to many fields that are not being irrigated this season – seen as tan rectangles with a faint grid of roads in between parcels. The blue geometric shapes on the left appear to be salt-drying pans.
Groundwater reserves can take centuries to recharge, so industrial-scale extraction of water for big agriculture in the middle of the desert cannot continue forever. In the US, water managers are facing an uphill battle to control water use in the Colorado River Basin and from the Ogallala Aquifer which stretches from Texas to South Dakota. Factor in that hydraulic fracturing is permanently removing water from the hydrological cycle in some of the most drought-stressed regions of the West, and you have a serious problem.
To be clear, the southwestern US and western Mexico are not necessarily about to fall in on themselves all at once, but they are struggling to support large-scale agriculture, enormous demand for water from a revitalized onshore oil and gas industry, and a growing population. Maybe this chasm in the desert doesn't herald the coming of Judgement Day, but perhaps we should be 'freaking out' about our poor judgement.