The Sustainable Groundwater Management Act (SGMA) directs the Department of Water Resources (DWR) to identify groundwater basins and subbasins that show obvious and significant negative impacts from chronic groundwater pumping. Those impacts include seawater intrusion, land subsidence, groundwater depletion, and/or chronic lowering of groundwater levels. DWR identified such basins in Bulletin-118, 1980 and in Bulletin 118, Update 2003.
Bulletin 118 is a comprehensive report on California groundwater resources that is periodically updated by DWR. As required in the SGMA, all Bulletin 118 basins designated as high or medium priority and subject to critical conditions of overdraft shall be managed under a groundwater sustainability plan or coordinated groundwater sustainability plans by January 31, 2020; all other high and medium priority basins must be managed under a groundwater sustainability plan by January 31, 2022. The final results will be published in the next update of Bulletin 118 expected in late 2016.
DWR has identified 21 groundwater basins and subbasins to be in conditions of critical overdraft. Details on the draft, public meetings, and webinar can be accessed here. The map and list of DWR identified critically overdrafted basins can be accessed here.