South Coast hydrologic region

[1] The state-defined South Coast hydrologic region is roughly equivalent to the federally-defined Southern California Coastal water resource subregion.

The South Coast hydrologic region has 78 state-recognized alluvial groundwater basins and subbasins.

The South Coast hydrologic region overlies an aquifer with a number of identified alluvial groundwater basins and subbasins.

An alluvial groundwater basin is essentially the top level of an aquifer, above less-permeable rocks below, such as limestone and shale.

[2] Alluvium (from Latin alluvius, from alluere 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings.