Following one of the driest years on record when groundwater resources have provided an increasing percentage of California’s water supply.  A recent report on groundwater basins that details groundwater level changes, potential water shortages, land subsidence, farmland fallowing and gaps in groundwater monitoring.

Drought conditions typically result in an increase in groundwater well activity and pumping to compensate for surface water supply shortages. Collectively, groundwater basins are the state’s largest reservoir, 10 times the size of all its surface reservoirs combined. More than 80 percent of Californians rely, in part, on groundwater for their drinking water.

Directed by Governor Edmund G. Brown Jr.’s Proclamation of a State of Emergency in April and following a previous DWR report on groundwater in April, the report shows groundwater basins in most areas of the state at historically low levels.

In September, Governor Brown signed a package of three bills which together create a framework for sustainable, local groundwater management for the first time in state history.  The legislation, known as the Sustainable Groundwater Management Act, allows local agencies to tailor groundwater sustainability plans to their regional economic and environmental needs.  For more information about the legislation, visit

If we fail to manage our groundwater basins sustainably, we risk losing the water supply savings account that can help cities, farms, and businesses survive drought with minimal disruption.

State and local agencies will be working together over the next several years to craft local sustainability plans in regions where groundwater basins are vulnerable to overdraft. Groundwater accounts for approximately 40 percent of the state’s total annual water supply, and in some regions of the state, as much as 60 percent of the supply during dry or drought years.

In the meantime, as documented in the report released today, California’s four-year-long drought is taking a heavy toll on many groundwater basins.  Basins with artificial grass notable decreases in groundwater levels are in the Sacramento River, San Joaquin River, Tulare Lake, San Francisco Bay, Central Coast and South Coast hydrologic regions.