A NASA report summarizing data collected from new satellites confirms what most water observers have known for a long time. Massive amounts of groundwater are being sucked out of California’s Central Valley groundwater aquifers — unreported, unmonitored, and unregulated.
Water Number: Between October 2003 and March 2009, more than 24 million acre-feet (30 cubic kilometers) of groundwater were pumped out of California’s Central Valley. This is overdraft of groundwater — the pumping of groundwater faster than nature recharges it. Most of the overdraft is occurring in the San Joaquin Valley and it is occurring at a rate far faster than previously reported by the California Department of Water Resources.
This rate of over pumping is more than 4.4 million acre-feet per year — more than three times above DWR’s previous estimates. DWR estimates are grossly unreliable because, as I have discussed many times in this column before, no one actually measures, monitors, or reports groundwater use. Whoever can pump it can have it, to the detriment of everyone else, our wetlands, and runoff into our rivers and streams. As one of the scientists on the project, Jay Famiglietti said, “GRACE data reveal groundwater in these basins is being pumped for irrigation at rates that are not sustainable if current trends continue.”
Groundwater storage changes in the Sacramento-San Joaquin River Basins from GRACE and supplementary data, October, 2003 Ã¢â‚¬â€œ March, 2009
The pumping has been so extreme that NASA’s twin GRACE satellites can detect the changes in local gravity caused by the massive loss of water. The two satellites are so sensitive to gravity that they are affected by changes in mass on earth’s surface — and water is very heavy. Ironically, a few months ago this same research group at NASA reported a massive loss of groundwater in India over approximately the same period of time, but the California loss is nearly twice as large.
The rapid loss of groundwater is largely the result of a vast increase in agricultural pumping because of drought and a reduction in recharge due to the last several dry years. The recent water legislation passed in Sacramento calls for some limited groundwater level measurements, but it does not provide for comprehensive monitoring of groundwater use or regulation of that use. California is heading for a catastrophe of huge proportions if the overdraft of groundwater continues at the same rate as the last few years. Groundwater levels will drop, the economic and energy cost of pumping will go up, and agricultural production will falter.
It is long past time to monitor and regulate all groundwater in California so that farmers and cities can use it as efficiently and sustainably as possible. The legislature must go back to work immediately and fix this oversight — we are the last state in the country without reasonable groundwater management and the state that needs it the most.
Dr. Gleick’s blog posts are provided in cooperation with the SFGate. Previous posts can be found here.