Pumping Groundwater in a Drought Is Great, As Long As You Have Groundwater

Photographer: Kevork Djansezian/Bloomberg

A dead lawn, left, is seen next to a green lawn in Los Angeles on July 18, 2014. Close

A dead lawn, left, is seen next to a green lawn in Los Angeles on July 18, 2014.

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Photographer: Kevork Djansezian/Bloomberg

A dead lawn, left, is seen next to a green lawn in Los Angeles on July 18, 2014.

Water is becoming so precious in the drought-stricken U.S. West that -- why not -- states are even taking steps to figure out how much of it they have.

California governor Jerry Brown in January challenged towns and state agencies to cut their water use by 20 percent. Now they're trying to measure what 20 percent means. It's hard. Cities and the state in some cases are coming up with estimates that differ by up to 10 times.

“Despite our longstanding water problems, we don’t accurately report and measure water in any sector -- urban or agricultural,” Peter Gleick, president of the Pacific Institute, a water think tank in Oakland, told James Nash of Bloomberg News. “That makes it difficult to implement programs to conserve water and deal with this crisis.”

All of California is in severe drought, according the U.S. Drought Monitor. Nearly 82 percent is in extreme drought and more than 36 percent is in exceptional drought, which is marked by crop and pasture loss and water shortage that fall within the top two percentiles of drought indicators.

In the Southwest, the Colorado River Basin remains “the most over-allocated river system in the world,” according to a study that will be published in Geophysical Research Letters.

U.S. Drought Monitor map from July 22. Yellow areas are "abnormally dry." Light orange areas have "moderate drought." Darker orange places are under "severe drought." Red areas have "extreme drought," and brown areas are under "exceptional drought." Source: David Miskus/NOAA/NWS/NCEP/CPC

U.S. Drought Monitor map from July 22. Yellow areas are "abnormally dry." Light orange areas have "moderate drought." Darker orange places are under "severe drought." Red areas have "extreme drought," and brown areas are under "exceptional drought." Source: David Miskus/NOAA/NWS/NCEP/CPC

The basin lost 64.8 cubic kilometers (15.5 cubic miles) of freshwater -- two-thirds of that disappearing from underground reservoirs -- over the time period in the study. That’s an amount of water almost twice the size of Lake Mead, the biggest U.S. reservoir, gone from the basin.

The study is important because using groundwater has become a way for communities to compensate for reduced surface water levels during drought. That could be a dangerous practice without knowing how much water is down there, or how quickly they’re using it. Drawing on satellite data, the researchers studied surface and groundwater volumes between December 2004 and November 2013.

The groundwater decline shocked the researchers, who conclude that the combination of less surface and groundwater “poses a significant threat to the long-term water security of the region.”

The upside of drought can be hard to see, but the beginning of a familiar tale is there: Counting things tends to provide a sense of how much you have; and knowing how much you have tends to provide incentive for taking better care of them.

More by Eric Roston (@eroston on Twitter):

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