Groundwater Basins in California

California Department of Water Resources (DWR) | November 1st, 1952

Section 229 of the Water Code directs that the California Department of Public Works, acting by and through the State Engineer, shall "investigate conditions of the quali

Section 229 of the Water Code directs that the California Department of Public Works, acting by and through the State Engineer, shall "investigate conditions of the quality of all the 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." In order to carry out the intent of Section 228 of the Water Code with respect to investigations of quality of ground waters within the State, it has been necessary first to compile available geologic data in order to locale and define the approximate boundaries of the more important ground water basins. A base index map showing the principal areas of groundwater storage in the State of California has not been previously prepared.  Such a map has been complied for this report in order to establish a uniform name and numbering system for groundwater basins, which can be expanded as new areas of ground water storage are identified, or as it is found necessary to divide the larger areas into subbasins.  It will serve as a basis for the planning of future investigations of the groundwater resources of California. This report identifies alluvial or valley fill areas which contain the principal groundwater resources in California.  However, the report is necessarily not complete because of lack of information for many areas of the state. In general, the areas of groundwater storage indentified include: (a) the major alluvium-filled areas of known groundwater storage and extraction; (b) the extensive areas of alluvial-fill in the Colorado, Mojave, and Basin and Range desert areas which may contain usable groundwater, though little is known of their storage capacity or recharge; and (c) some of the smaller alluvium-filled areas which may furnish a portion of local domestic, irrigation, municipal, and industrial water supplies.

Groundwater Level Monitoring and the Importance of Long-Term Water-Level Data

U.S. Geological Survey (USGS) | December 18th, 2001

Ground water is among the Nation’s most precious natural resources. Measurements of water levels in wells provide the most fundamental indicator of the status of this r

Ground water is among the Nation’s most precious natural resources. Measurements of water levels in wells provide the most fundamental indicator of the status of this resource and are critical to meaningful evaluations of the quantity and quality of ground water and its interaction with surface water. Water-level measurements are made by many Federal, State, and local agencies. It is the intent of this report to highlight the importance of measurements of ground-water levels and to foster a more comprehensive and systematic approach to the long-term collection of these essential data. Through such mutual efforts, the Nation will be better positioned in coming decades to make wise use of its extensive groundwater resources.

Groundwater Management and Safe Drinking Water in the San Joaquin Valley

Water Foundation | June 2nd, 2020

Groundwater Management Plan Goleta Groundwater Basin

Goleta Water District (GWD) | May 11th, 2010

Goleta Water District (“GWD”) and La Cumbre Mutual Water Company (“La Cumbre”), the purveyors of groundwater in the Goleta Groundwater Basin, joined in developing

Goleta Water District (“GWD”) and La Cumbre Mutual Water Company (“La Cumbre”), the purveyors of groundwater in the Goleta Groundwater Basin, joined in developing a Groundwater Management Plan (“Plan”) for the basin. This Plan reiterates current adjudication and voter-passed components of groundwater management, addresses groundwater issues, adopts Basin Management Objectives, outlines management strategies for the basin, and recommends future tasks and timelines associated with these tasks.

Groundwater Pumping Allocations under California’s Sustainable Groundwater Management Act: Considerations for Groundwater Sustainability Agencies

Environmental Defense Fund (EDF) | July 1st, 2018

The Sustainable Groundwater Management Act (SGMA) became law on January 1, 2015, forever changing the manner in which groundwater will be managed in California. It requir

The Sustainable Groundwater Management Act (SGMA) became law on January 1, 2015, forever changing the manner in which groundwater will be managed in California. It requires local Groundwater Sustainability Agencies (GSAs) to be formed and Groundwater Sustainability Plans (GSPs) to be prepared in order to achieve sustainable groundwater management within 20 years of adopting a GSP. SGMA applies to 127 medium and high priority groundwater subbasins around the state. Over 100 of the medium and high priority groundwater subbasins are in conditions of chronic overdraft (DWR, 2018), meaning average annual groundwater extractions exceed average annual water replenishment to many of the subbasins. These conditions have resulted in a variety of undesirable impacts to the subbasin, including, but not limited to, increasing depth to groundwater, reductions of groundwater storage, seawater intrusion, degraded water quality, and land subsidence. In many subbasins, groundwater overdraft conditions will require GSAs to impose reductions in pumping in order to achieve sustainable conditions in the subbasin. To do this, GSAs will need set a limit or “cap” on the overall amount of groundwater that is removed from the subbasin, assigning portions of this capped amount to groundwater pumpers in the form of a pumping allocation. Making pumping allocation decisions will be a difficult task for GSAs, as it will require restricting access to groundwater resources upon which the agricultural community, cities and towns, and others depend. SGMA expressly does not create or adjust groundwater rights and the basic law of groundwater rights remains largely unchanged. Simply put, this means that while GSAs are tasked with managing groundwater with the goal of bringing groundwater conditions into balance and stopping further depletions and other undesirable impacts, they do not have the authority to change or modify groundwater rights. Thus, GSAs should be mindful of the basic law of groundwater as articulated by the common law and a series of adjudicatory court decisions over the last 100 plus years. The subject of this paper is how to address this dilemma, with the reasoning that if GSAs devise groundwater allocation schemes in a manner consistent with the fundamental principles of groundwater law, the schemes are likely to be more durable, and GSAs are more likely to achieve sustainable groundwater management in a legally defensible manner. To do this, we first provide background on the nature of groundwater rights and how the hierarchy of groundwater rights may affect the legal defensibility of pumping allocations imposed by GSAs upon pumpers. We then discuss the role of groundwater allocations and methods for allocating groundwater pumping rights, and then offer a suggested allocation approach with criteria for consideration when using this approach. To help readers work through the allocation process, the paper includes a hypothetical decision tree graphic. We also discuss the importance of measurement, tracking, and enforcement, as well as additional considerations under SGMA before offering some concluding remarks.

Groundwater Quality Protection Strategy: A "Roadmap" for the Central Valley Region

Central Valley Regional Water Quality Control Board (CVRWQCB) | January 8th, 2010

The California Regional Water Quality Control Board, Central Valley Region (Central Valley Water Board) recognizes that past regulatory approaches have not protected all

The California Regional Water Quality Control Board, Central Valley Region (Central Valley Water Board) recognizes that past regulatory approaches have not protected all groundwater from historical and current practices associated with land applications of waste. For example, in some areas of the Central Valley Region groundwater produced from some aquifers that serve individual and community drinking water systems have been polluted and are unsafe to drink. In response, the Central Valley Water Board adopted Resolution R5-2008-0181 directing staff to develop a Groundwater Quality Protection Strategy (Roadmap) through an active stakeholder process. Developing a Roadmap for the Central Valley Region is not initiating a new regulatory program. This Roadmap is intended to be an overarching framework or an outline for long range planning. By presenting it to the Central Valley Water Board it allows the Board review and approval of the overarching plan as well as an opportunity to provide direction to staff. Further, it defines the regulatory programs to be enhanced, and identifies ways to expand on all partnering opportunities with other federal, state, and/or local agencies to protect groundwater quality. Following approval of the Roadmap, workplan(s) will be developed for the higher priority future actions to provide a more detailed description of tasks, timelines, and resources required to implement those actions. In order to make this Roadmap useful to the public, policy-makers, and the Central Valley Water Board, a starting point to map a course for the future had to be identified. The starting point for the Roadmap is the background (Section 3) information on agencies and organization, the Central Valley Region’s basins, and primary constituents of concern. Current Groundwater Quality Protection Programs (Section 4) being implemented by the Central Valley Water Board describe how groundwater quality is being protected now. To assist in the evaluation of existing groundwater quality protection programs and identification of future actions, Stakeholder’s Concerns and Issues (Section 5) were also considered. The final section of the Strategy is the “Roadmap” (Section 6) which focuses on future actions that can be implemented within the next five to twenty years. To illustrate the Roadmap, a description is provided of three basic elements: a) future actions; b) how the actions are prioritized; and c) resource needs to implement the actions. Implementation of future actions, are not limited to the Central Valley Water Board. Future actions may be implemented by: the Central Valley Water Board; other agencies or organization; or through a partnership between agencies.

Groundwater Quality Protection Strategy: A “Roadmap” for the Central Valley Region

California Environmental Protection Agency (CalEPA) | August 2nd, 2010

The California Regional Water Quality Control Board, Central Valley Region (Central Valley Water Board) recognizes that past regulatory approaches have not protected all

The California Regional Water Quality Control Board, Central Valley Region (Central Valley Water Board) recognizes that past regulatory approaches have not protected all groundwater from historical and current practices associated with land applications of waste. For example, in some areas of the Central Valley Region groundwater produced from some aquifers that serve individual and community drinking water systems have been polluted and are unsafe to drink. In response, the Central Valley Water Board adopted Resolution R5-2008-0181 directing staff to develop a Groundwater Quality Protection Strategy (Roadmap) through an active stakeholder process.  Developing a Roadmap for the Central Valley Region is not initiating a new regulatory program. This Roadmap is intended to be an overarching framework or an outline for long range planning. By presenting it to the Central Valley Water Board it allows the Board review and approval of the overarching plan as well as an opportunity to provide direction to staff. Further, it defines the regulatory programs to be enhanced, and identifies ways to expand on all partnering opportunities with other federal, state, and/or local agencies to protect groundwater quality. Following approval of the Roadmap, workplan(s) will be developed for the higher priority future actions to provide a more detailed description of tasks, timelines, and resources required to implement those actions.  In order to make this Roadmap useful to the public, policy-makers, and the Central Valley Water Board, a starting point to map a course for the future had to be identified. The starting point for the Roadmap is the background (Section 3) information on agencies and organization, the Central Valley Region’s basins, and primary constituents of concern. Current Groundwater Quality Protection Programs (Section 4) being implemented by the Central Valley Water Board describe how groundwater quality is being protected now. To assist in the evaluation of existing groundwater quality protection programs and identification of future actions, Stakeholder’s Concerns and Issues (Section 5) were also considered.  The final section of the Strategy is the “Roadmap” (Section 6) which focuses on future actions that can be implemented within the next five to twenty years. To illustrate the Roadmap, a description is provided of three basic elements: a) future actions; b) how the actions are prioritized; and c) resource needs to implement the actions. Implementation of future actions, are not limited to the Central Valley Water Board. Future actions may be implemented by: the Central Valley Water Board; other agencies or organization; or through a partnership between agencies.  Also: Groundwater Quality Protection Strategy for the Central Valley Region, a Roadmap - Addendum 2015/2016 Home page of Groundwater Quality Protection Strategy for the Central Valley Region, R-5

Groundwater Resource Management Fundamentals: Groundwater Basin Connectivity

United Water Conservation District (UWCD) | May 14th, 2014

As Ventura County and the rest of the State of California continue to deal with drought conditions there is an increased interest and reliance on groundwater reso

As Ventura County and the rest of the State of California continue to deal with drought conditions there is an increased interest and reliance on groundwater resources. Over the past decade or so the CA Department of Water Resources and others have promoted water supply planning by watershed groups or other local entities, and this approach has generally been accepted by planners and stakeholders. In Ventura County, there is significant groundwater flow between defined groundwater basins both within and between watersheds, and stream flow in the dry seasons is commonly dependent on groundwater discharges to stream channels. Groundwater flow between connected subbasins has long been recognized in southern Ventura County, most notably in the groundwater basins that underlie the watersheds of the Santa Clara River and Calleguas Creek. The intent of this Open-File Report is to document the historical evolution of the concept of the hydrologic connectivity of groundwater basins in the Santa Clara River valley and the Oxnard Plain coastal area, and to summarize the underlying scientific data supporting the hydrologic connectivity principle. The idea of groundwater basin connectivity is not new, and in fact, predates the formation of United Water Conservation District (United), but is a concept that is embraced by United as a key tenet of their groundwater management activities. As a primary groundwater management entity for the Santa Clara River valley and Oxnard Plain area, United has extensive datasets supporting the concept of groundwater flow or movement (i.e., connectivity) between the subbasins in its jurisdiction. The current drought conditions being experienced in Ventura County have reinvigorated a desire by several entities to develop basin-wide or regional water supply management plans. Clearly, the hydrologic relationships between the groundwater basins are important factors for recognition in water supply management plans. The effects of groundwater extraction or wastewater discharge, for example, impact downgradient subbasins and respective stakeholders. Recognition of this important hydrologic relationship is fundamental to creating long-term sustainable groundwater resource management strategies. The current regulatory setting in California includes several attempts to “manage” groundwater resources or water resource, in general, but those attempts are often focused at a local level (e.g., Urban Water Management Plans, Agricultural Water Management Plans) that do not account for the regional nature of this resource. These “entity-specific” plans are not, by themselves, sufficient for water resource sustainability planning purposes as they frequently ignore or minimize the importance of the regional nature of the hydrologic system. This Open-File Report has been prepared to provide Ventura County water resource management agencies (e.g., Fox Canyon Groundwater Management Agency, Ventura County Watershed Protection District, United Water Conservation District) and local municipalities and businesses that may be stakeholders in the development of water resource management and sustainability plans a guiding framework for thinking about how the hydrologic systems in the Santa Clara River valley and the greater Oxnard Plain coastal area function.

Groundwater Sustainability Agency Support and Sustainable Groundwater Management Planning

Freshwater Trust | January 16th, 2018

California’s Sustainable Groundwater Management Act (SGMA) poses significant challenges for the expedited establishment of Groundwater Sustainability Agencies (GSA) and

California’s Sustainable Groundwater Management Act (SGMA) poses significant challenges for the expedited establishment of Groundwater Sustainability Agencies (GSA) and the development of effective Groundwater Sustainability Plans (GSP) or alternative compliance plans. The Freshwater Trust has experience working with eligible agencies, counties, and the California Department of Water Resources to support GSA development. We partner with the respective technical and administrative staff to streamline the governance process and to meet the schedule for implementation.

Groundwater Sustainability Plan Fillmore Basin (Final - Revised)

Fillmore and Piru Basins Groundwater Sustainability Agency | July 8th, 2024

In January 2024, the California Department of Water Resources (DWR) informed the Fillmore and Piru Basins Groundwater Sustainability Agency (FPBGSA or Agency) that the Gr

In January 2024, the California Department of Water Resources (DWR) informed the Fillmore and Piru Basins Groundwater Sustainability Agency (FPBGSA or Agency) that the Groundwater Sustainability Plan (GSP) submitted to DWR in January 2022 for the Fillmore Basin was deemed incomplete and provided the Agency with a 180-day period to address the deficiencies. In consultation with DWR, the Agency Board of Directors, and stakeholders, the Fillmore Basin GSP has been revised to address the deficiencies. This revised version of the GSP is not a complete update of the GSP; rather, it only revises those sections of the GSP (and associated appendices) to address the DWR-identified deficiencies. A more robust revisit of the GSP will be part of the 5-year update due in 2027. Due to size, this file has been divided. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9, Part 10, Part 11, Part 12, Part 13