New data being presented by NASA scientists at this week’s AGU meeting shows how truly remarkably fast California’s aquifers are being sucked dry:

New space observations reveal that since October 2003, the aquifers for California’s primary agricultural region — the Central Valley — and its major mountain water source — the Sierra Nevadas — have lost nearly enough water combined to fill Lake Mead, America’s largest reservoir. The findings, based on data from the NASA/German Aerospace Center Gravity Recovery and Climate Experiment (Grace), reflect California’s extended drought and increased rates of groundwater being pumped for human uses, such as irrigation.

It is worth remembering here the regulatory environment. California doesn’t keep track of or regulate in any way groundwater pumping. It’s a classic “common pool resource”, and the farmers have no incentive not to pump in a drought like they’re in now. If Farmer Brown shows restraint, Farmer Jones down the road can still pump just as much. This is the sort of thing Elinor Ostrom talks about when folks don’t get together voluntarily to manager their commons.