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California's Groundwater: Bulletin 118

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Example of Basins Map in IWRIS - Click to enlarge Example of Basin Description in IWRIS - Click to enlarge
Example of groundwater basin/subbasin
map and description available in IWRIS

Groundwater Basin Maps and Descriptions

Out of 431 delineated groundwater basins, 24 basins are subdivided to create an additional 108 subbasins. These 515 distinct groundwater systems underlie about 40 percent of the surface area of the State.

Many of the subbasin boundaries were developed or modified with public input, but little physical data. Because they should not be considered precise boundaries, a detailed local study should determine whether any specific area lies within a groundwater basin boundary.

   North Coast (list of basins, map)

   San Francisco Bay (list of basins, map)

   Central Coast (list of basins, map)

   South Coast (list of basins, map)

   Sacramento River (list of basins, map)

   San Joaquin River (list of basins, map)

   Tulare Lake (list of basins, map)

   North Lahontan (list of basins, map)

   South Lahontan (list of basins, map)

   Colorado River (list of basins, map)


Basin descriptions are based on the best available information. In basins where many studies have been completed and the basin has been operated for a number of years, the basin response is fairly understood and the boundaries are well defined. Even in these basins, however, there are many unknowns and the boundaries may change as more information is collected and evaluated.

Integrated Water Resources Information System    To view groundwater basin and subbasin descriptions, go to DWR's Integrated Water Resources Information System (IWRIS) web site.

IWRIS is a GIS-based web application that allows the user to access, query, integrate, and visualize different sets of data.

How do I use IWRIS?