The shape file shows groundwater basins and subbasins as defined by the California Department of Water Resources. The file is intended for use with GIS software able to import files of suffix '.shp'. Groundwater basins are designated on the basis of geological and hydrological conditions, these usually being 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.

PROJECTION PARAMETERS

Datum:    

NAD83

Projection:

Geographic, Lat./Long. (Unprojected)

Spheroid:

Clarke 1866

Units:  

Meters

Source:

Department of Water Resources

KEY ATTRIBUTES

DWR_

DWR Number - includes hydrologic region number in first position.

SUBBSN_

DWR subbasin number only.

BAS_SBBSN

Combined field of basin and subbasin number.

GWBASIN

Name of groundwater basin.

BUDGET_TYP

A, B, or C type basin budget, as described in Bulletin 118 (2003)

SUBNAME

Subbasin name, where applicable

REGIONAL_O

DWR Region Office responsible for individual basin delineation and description
1 = Northern
2 = North Central
3 = South Central
4 = Southern

ACRES

Area of basin or subbasin in acres

Additional Information
The basin boundaries for the revised groundwater basin map were primarily defined using geologic contacts and hydrogeologic divides. Specifically the identification of the groundwater basins was initially based on the presence and areal extent of unconsolidated alluvial soils identified on 1:250,000 scale geologic maps provided by the California Department of Conservation, Division of Mines and Geology. The identified groundwater basin areas were then further evaluated through review of relevant geologic and hydrogeologic reports, well completion reports, court-determined adjudicated basin boundaries, and contact with local agencies to refine the basin boundaries.

Metadata Update - December 09, 2010
B118_v3_BasinBoundaries_NAD83_unprojected file was developed from B118v3NAD27UTM10 (dated 15-September-2006) which had a UTM 10 NAD 27 projection. The new file projection is defined as Latitude/Longitude NAD 83 and was converted using ESRI's Project tool in a two step process. Set one changed the Datum from NAD27 to NAD 83. The second step was to re-project the file from Universal Transverse Mercator 10 to Lat/Long Geographic projection for the use of CASGEM.

Metadata Update – June 20, 2012
The shapefile B118_BasinBoundaries_v4_1.shp  replaces B118_v3_BasinBoundaries_NAD83_unprojected.shp.   Changes in the update include restoration of the northern portion of the North Yuba subbasin which was inadvertently removed during the 2003 B-118 Update.  Also, the DWR District field (DWR_DIST) in the feature attribute table has been replaced by Regional Office Field (Regional_O).  Basin boundary features in previous versions that were comprised of multiple polygons are now represented by single multi-part polygons.