Mike Conway of the Arizona Geological Survey started getting phone calls from realtors several months ago. With the Phoenix-area real estate market heating back up, they needed to know if their clients are looking at land run through with cracks that might open up and damage their homes, or worse. In 2008, a fissure known as the Y-crack became famous when it split open in the wake of heavy summer rains and swallowed a horse southeast of Phoenix.
Looking at a national scale, since 1900, there’s been enough water pumped from underneath the U.S. to fill Lake Erie twice over. In a related 2011 study, Konikow calculated that it’s enough water to raise sea level by about 2.8 millimeters, accounting for a little over two percent of global sea level rise between 2000 and 2008 (this happens because taking water from underground puts it into the water cycle, where most paths lead to the ocean, and not back underground).
In 1911, Nevada’s state engineer, W.M. Kearney, pleaded for water to be used “… with economy instead of the lavish wasteful manner, which has prevailed in the past.” The opposite has happened: as a nation, we’ve been extracting water faster than ever, mocking Kearney’s quaint Gilded Age plea. Even Konikow was surprised by his results: After 2000, groundwater depletion shot up by 25 percent. (In the graph below an increasing line on the graph means more depletion, and less water underground).
In places like Las Vegas, Los Angeles, and parts of Arizona (graph below) where the water table is no longer plummeting, it’s usually thanks to some combination of improving groundwater management and shipping in river water from somewhere else. For example, faced with falling water tables and sinking land, Arizona adopted state policy in 1980 to try to slow pumping. In the 90s it also began importing Colorado River Water to Phoenix and Tucson via the Central Arizona Project. Ironically, land subsidence (the technical term for sinking) from groundwater pumping damaged the project’s canal in 1999, and threatened to reduce Colorado River water deliveries to farms and cities.
According to Konikow, adding up all of the depletion in his report means that there’s going to have to be some (more) oversight of groundwater. Solutions to groundwater problems are usually local endeavors. For an example, see Cally Carswell’s High Country News story on San Luis Valley farmers self-regulating irrigation.
All of this begs the question, how much time do these aquifers have left? That’s even harder to figure out than estimating how much we’ve used up. Since California’s Central Valley (graph below) and the Oglala aquifers are so extensive and important for growing food, they’ve been watched closely, but the difficulty of estimating how much water is hiding within rock and soil means that others are less well-documented. A 2012 study [pdf] on groundwater and irrigation sustainability in the Central Valley and High Plains cited an estimate of 240 years left for Kansas and 140 years of water remaining in Texas. For the Central Valley the estimate was 390 years.
It’s important to note that those estimates are for
“At some point the problems are going to be more and more frequent in more and more places — and people may not notice until it’s really severe,” says Konikow.
Sarah Jane Keller is a High Country News intern.
Arizona’s Y-crack fissure in 2007, courtesy of Arizona Geological Survey (check out this site for maps of fissures).
Graphs courtesy of U.S. Geological Survey: Groundwater Depletion in United States (1900-2008).
Republish our articles for free, online or in print, under a Creative Commons license.
