The California Department of Water Resources (DWR) has long recognized the need for collection, summary, and evaluation
of groundwater data as tools in planning optimal use of the groundwater resource. An example of this is DWR's Bulletin 118 series.
Bulletin 118 presents the results of groundwater basin evaluations in California.
Place your mouse pointer over each link below to learn more about major events in Bulletin 118 history.
Ground Water Basins in California
Water Quality Investigations Report No. 3
The Bulletin 118 series was preceded by Water Quality Investigations Report No. 3, Ground Water Basins in California,
published in 1952 by the Department of Public Works and Division of Water Resources (the predecessor of DWR).
Ground Water Basins in California created a base index map of the primary water basins used to carry out DWR's mandate in
Section 229 of the Water Code. Section 229, which directed Public Works to:
"... investigate conditions of the quality of all waters within the State, including saline waters, coastal and inland, as related to all sources of pollution
of whatever nature and shall report thereon to the Legislature and to the appropriate regional water pollution control board annually, and may recommend any steps
which might be taken to improve or protect the quality of such waters."
Ground Water Basins in California identified 223 alluvium-filled valleys that were believed to be basins with usable groundwater in storage.
A statewide numbering system was created in cooperation with the State Water Pollution Control Board (now the State Water Resources Control Board)
based on the boundaries of the nine Regional Water Quality Control Boards.
California's Ground Water
Bulletin 118-75
Bulletin 118, California's Ground Water summarized available information from DWR, U.S. Geological Survey, and other agencies for individual groundwater basins to
"help those who must make decisions affecting the protection, additional use, and management of the State's ground water resources."
Bulletin 118-75 contains a summary of technical information for 248 of the 461 identified groundwater basins, subbasins, and what were referred to as
"areas of potential ground water storage" in California as well as maps showing their location and extent. The Bulletin 118-75 basin boundaries were based
on geologic and hydrogeologic conditions except where basins were defined by a court decision.
California Water Code Update
Section 12924 added to the California Water Code:
"The Department shall, in conjunction with other public agencies, conduct an investigation of the State's groundwater basins. The Department shall identify the State's groundwater basins on
the basis of geologic and hydrogeologic conditions and consideration of political boundary lines whenever practical. The Department shall also investigate existing general patterns of groundwater
pumping and groundwater recharge within such basins to the extent necessary to identify basins which are subject to critical conditions of overdraft."
Ground Water Basins in California:
A Report to the Legislature in Response to Water Code Section 12924
Bulletin 118-80
Ground Water Basins in California: A Report to the Legislature in Response to Water Code Section 12924 updated boundaries on 36 groundwater basins. The changed boundaries combined several basins
based on geologic or political considerations and divided the San Joaquin Valley groundwater basin into many smaller subbasins based primarily on political boundaries. These changes resulted in
the identification of 447 groundwater basins, subbasins, and areas of potential groundwater storage. Bulletin 118-80 identified 11 basins as subject to critical conditions of overdraft.
Budget Act of 1999
Despite California's heavy reliance on groundwater, basic information for many of the groundwater basins is
lacking. Particular essential data necessary to provide for both the protection and optimal use of this resource is
not available. To this end, the California Legislature mandated in the Budget Act of 1999 that DWR prepare:
"...the statewide update of the inventory of groundwater basins contained in Bulletin 118-80,
which includes, but is not limited to, the following: the review and summary of boundaries and
hydrographic features, hydrogeologic units, yield data, water budgets, well production
characteristics, and water quality and active monitoring data; development of a water budget for
each groundwater basin; development of a format and procedures for publication of water
budgets on the Internet; development of the model groundwater management ordinance; and
development of guidelines for evaluating local groundwater management plans."
California's Groundwater
Bulletin 118 - Update 2003
The long-awaited update to California's Groundwater, Bulletin 118 was released to the public in early
October 2003. Bulletin 118 - Update 2003 is the first comprehensive report on groundwater since 1980 when Bulletin
118-80 was published.
California's Groundwater includes guidance and tools that will assist local agencies in effectively managing
groundwater as a sustainable part of their water supplies. California's Groundwater includes a description of
current groundwater management efforts by local water agencies, required and recommended components
of effective groundwater management plans, and a model ordinance that can be used by local governments.
In addition, the bulletin describes the roles of state and federal agencies in protecting groundwater quantity
and quality.
Online technical descriptions and GIS compatible maps of 515 groundwater basins and subbasins were part of
the effort to publish the bulletin. The basin/subbasin descriptions include information about the geology,
groundwater quantity and quality, and current groundwater management practices in the basins.
This supplemental material will be updated as new information becomes available.
