This polygon shapefile contains the boundaries of 517 groundwater basins and subbasins as defined by the California Department of Water Resources as last modified by the Basin Boundary Emergency Regulation adopted on October 21, 2015. Groundwater basins are represented as polygon features and designated on the basis of geological and hydrological conditions - usually the occurrence of alluvial or unconsolidated deposits. When practical, large basins are also subdivided by political boundaries, as in the Central Valley. Basins are named and numbered per the convention of the Department of Water Resources. The associated data are considered DWR enterprise GIS data, which meet all appropriate requirements of the DWR GIS Spatial Data Standards.Bulletin 118 defines the recognized groundwater basins and subbasins throughout the State of California. The Bulletin 118 document provides information on these basins/subbasins and the nature and extent of groundwater occurrence and management within the State. The Bulletin 118 dataset makes the geographic locations and extent of the 517 basins/subbasins publically available, for use in external mapping/GIS applications.