Report Shows Groundwater Basins with Impending Water Shortages and Gaps in Monitoring

A report released by the California Department of Water Resources concludes that groundwater levels throughout the state have reached all-time historic lows and that many areas lack adequate groundwater monitoring. Gov. Brown’s Jan. 17 Emergency Drought Proclamation required DWR to report on groundwater shortages and gaps in monitoring at the statewide level. Sustainable groundwater management has become a key priority of the Governor’s office, and the 2014-15 budget, potential groundwater legislation, and DWR’s report demonstrate the intensified focus on this critical resource. DWR will conduct intensive outreach and provide technical assistance to local agencies to increase groundwater monitoring.

Conclusions of DWR’s Report:

1) Groundwater levels throughout the state have reached all-time historic lows.

• Groundwater levels have decreased statewide since spring 2013.
• Groundwater levels have decreased even more significantly since spring 2010.
• Groundwater levels have dropped most significantly in the San Francisco Bay Hydrologic Region, the South Lahontan and South Coast areas, and the San Joaquin Valley.
• Nevada, Placer and El Dorado counties have the greatest concentration of well deepening activity.
• Thirty-six alluvial groundwater basins in the state serve as the primary water source for their regions and are most likely to incur drought-related shortages. These basins are in the North Coast, Central Coast, Sacramento River, Tulare Lake, and South Coast regions and serve a population of 6.18 million total.

2) Areas throughout the state lack adequate groundwater monitoring.

• Groundwater monitoring is critical for maintaining the health of basins, especially in drought conditions.
• Only 169 out of 515 alluvial groundwater basins are fully or partially monitored under the California Statewide Groundwater Elevation Monitoring.
• Forty of the 126 high and medium priority basins are not monitored under CASGEM.
• Some basins are partially monitored but have data gaps.
• The lack of monitoring and absence of groundwater management plans subject these basins to increased stress under drought conditions.

In preparing its report, DWR analyzed data from the CASGEM Program, the Water Data Library groundwater database, the draft Bulletin 160 California Water Plan Update 2013, and the well drillers’ logs submitted to DWR. DWR is also working with NASA and the NOAA to evaluate land subsidence and agricultural land fallowing using satellite monitoring.

Groundwater pumping is expected to increase throughout the summer as the effects of this year’s drought continue to manifest. Increased pumping can create dry wells, land subsidence, decreased water quality, saline intrusion, and stream depletion. Groundwater rights can also be threatened as competing demands vie for a limited supply.

DWR is required to issue a follow-up report by Nov. 30. That report will address areas where the drought has had significant impacts on groundwater resources.