The Magnitude of California's Water Challenges

UnIversity of California, Davis (UC Davis) | June 4th, 2024

California will see increasing water scarcity from climate change, the end of overdrafting groundwater and the Colorado River’s massive reservoirs, increased water dedi

California will see increasing water scarcity from climate change, the end of overdrafting groundwater and the Colorado River’s massive reservoirs, increased water dedications for environmental flows, and other factors, such as salination of aquifers and land subsidence reducing canal capacities. Total reduction in average water availability in the coming decades will likely range from 4.6 to 9 million acre-feet per year. For context, this is equivalent to the water use of 1 – 2.8 million acres of irrigated agriculture or most urban water use in California. Perhaps 20-30% of this loss will likely be addressed by ongoing water conservation and supply improvements, being planned and implemented, leaving a 3 – 7.2 million acre-feet/year likely net average difference between statewide water demands and availability.

The Mohave Desert region, California--a geographic, geologic, and hydrologic reconnaissance

U.S. Geological Survey (USGS) | July 15th, 1929

The pattern of fresh‐water flow in a coastal aquifer

American Geophysical Union (AGU) | April 1st, 1959

Formulas are developed for the flow pattern followed by the seaward‐moving fresh ground water as it nears a beach. It is found that, under steady flow conditions, a sha

Formulas are developed for the flow pattern followed by the seaward‐moving fresh ground water as it nears a beach. It is found that, under steady flow conditions, a sharply defined interface is formed between the fresh and salt water. Along the interface the pressure of the static salt water, owing to its greater density, is counterbalanced by the pressures which drive the fresh water seaward. The fresh water escapes through a gap between this interface and the shore line. An increase in the flow of fresh water widens the gap. Tidal action causes a diffusion of salt water across the interface. This salt is carried back to sea with the fresh‐water flow.

The Radical Groundwater Storage Test

Scientific American | October 19th, 2017

IN BRIEF California could better survive flood years and drought years by capturing floodwaters and using them to recharge underground aquifers that farmers and muni

IN BRIEF California could better survive flood years and drought years by capturing floodwaters and using them to recharge underground aquifers that farmers and municipalities now pump from when rains are scarce. To do so, water users and managers have to regard surface water and groundwater as one connected resource. A variety of test projects are proving that this approach can work. For example, farm fields can be flooded even when crops are growing so the water can percolate down into aquifers. Revising water rights and paying landowners to allow flooding can help the techniques work across California and the world.

The relative contributions of summer and cool-season precipitation to groundwater recharge, Spring Mountains, Nevada, USA

Hydrogeology Journal (Springer) | June 1st, 1998

A comparison of the stable-isotope signatures of spring waters, snow, snowmelt, summer (July thru September) rain, and cool season (October thru June) rain indicates that

A comparison of the stable-isotope signatures of spring waters, snow, snowmelt, summer (July thru September) rain, and cool season (October thru June) rain indicates that the high-intensity, short-duration summer convective storms, which contribute approximately a third of the annual precipitation to the Spring Mountains, provide only a small fraction (perhaps 10%) of the recharge to this major upland in southern Nevada, USA. Late spring snowmelt is the principal means of recharging the fractured Paleozoic-age carbonate rocks comprising the central and highest portion of the Spring Mountains. Daily discharge measurements at Peak Spring Canyon Creek during the period 1978–94 show that snowpacks were greatly enhanced during El Niño events.

The source of water derived from wells— Essential factors controlling the response of an aquifer to development

American Society of Civil Engineers (ASCE) | May 1st, 1940

The paper presented herewith, as a Ground Water Note, was first published by the American Society of Civil Engineers in its Civil Engineering magazine (p. 277-280

The paper presented herewith, as a Ground Water Note, was first published by the American Society of Civil Engineers in its Civil Engineering magazine (p. 277-280) for May 1940. A number of years ago the Ground Water Branch reprinted the paper in limited quantity for distribution to the field offices and some field personnel. The original paper is faithfully reproduced herein, except for minor changes in notation to conform with current Branch usage. Theis’ extremely lucid discussion of the source of water discharged by wells should be clearly understood by all who would attempt to analyze how a preexisting balanced hydraulic system will adjust to newly imposed well discharge.

The State Water Project Delivery Capability Report 2023 Addendum - Impacts of Subsidence

California Department of Water Resources (DWR) | May 7th, 2025

The purpose of this addendum is to show how ongoing subsidence effects on the California Aqueduct will impact operation of the State Water Project (SWP). The addendum pro

The purpose of this addendum is to show how ongoing subsidence effects on the California Aqueduct will impact operation of the State Water Project (SWP). The addendum provides information to SWP water users about a potential range of water delivery impacts over the next 20 years if no corrective action is taken to address the subsidence effects. However, the California Department of Water Resources (DWR) is committed to restore the conveyance capacity of the California Aqueduct and has an engineering plan for near-term fixes. DWR is also working with its partners to secure additional funding sources for this work. DWR is confident that the California Aqueduct capacity will be restored and the SWP will not see the impacts outlined in this addendum. Thus, long-term water supply planning activities by water users should rely on the potential future SWP allocation results presented in the 2023 Delivery Capability Report (DCR 2023) released in 2024.

The Sustainable Groundwater Management Act challenges the diversity of California farms

California Agriculture (UCANR) | November 16th, 2016

California’s agricultural sector, a major groundwater user, finds itself in the midst of the implementation of the Sustainable Groundwater Management Act (SGMA). The la

California’s agricultural sector, a major groundwater user, finds itself in the midst of the implementation of the Sustainable Groundwater Management Act (SGMA). The law mandates the formation of local groundwater sustainability agencies (GSAs) and adoption of groundwater sustainability plans (GSPs) for all overdrafted groundwater basins across the state by 2020. Each GSA will be unique, with its own governance structures and rules, including the size and composition of the governing board, mechanisms for representing different interests, opportunities for stakeholders to participate, and rules concerning the allocation of pumping “rights” and the use of economic instruments, such as pumping permits, pumping taxes or tiered pricing, to incentivize pumping curtailments (DWR 2016). This new water management landscape may threaten the diversity of the state’s farming operations.

The Sustainable Groundwater Management Act Governance Conference: Research and Practice Synthesis Report 2018

University of California, Davis (UC Davis) | June 8th, 2018

“The Sustainable Groundwater Management Act Governance Conference: Research and Practice,” held at the UC Davis in February 2018, assembled 55 social science research

“The Sustainable Groundwater Management Act Governance Conference: Research and Practice,” held at the UC Davis in February 2018, assembled 55 social science researchers as well as practitioners from across the state to discuss the ongoing implementation of the Sustainable Groundwater Management Act (SGMA). The California Legislature passed SGMA in 2014. SGMA required the formation of new groundwater sustainability agencies (GSAs) by June 2017 in order to develop and implement Groundwater Sustainability Plans (GSPs) for 127 medium- and high-priority groundwater basins by 2020 and 2022. With such a large task at hand, and given the importance of groundwater to California’s public health, environment, and economy, strengthening collaboration across research teams as well as between researchers and practitioners is crucial to increasing the capacity for learning about governance processes and to bridging the science-policy divide in order to support the creation of effective governance institutions. The goals of this report are to synthesize key lessons learned about SGMA at the nexus of research and practice, and to create a roadmap and research agenda going forward. Sharing information and knowledge among research teams enables a comparative perspective that cannot be achieved by one team alone. Furthermore, perspectives from practitioners inform research directions, focus attention on relevant issues and knowledge gaps, and build relationships among the SGMA community for more collaborative applied research. Conference discussions focused on discovering what has been learned in the first three years of SGMA implementation and GSA development, identifying high priority questions for the next stage of GSP development, sharing research methods, and coordinating research activities.

The Water Quality Control Plan (Basin Plan) for the Sacramento River and San Joaquin River Basins Fifth Edition

Central Valley Regional Water Quality Control Board (CVRWQCB) | May 31st, 2018

The preparation and adoption of water quality control plans (Basin Plans) is required by the California Water Code (Section 13240) and supported by the Federal Clean Wat

The preparation and adoption of water quality control plans (Basin Plans) is required by the California Water Code (Section 13240) and supported by the Federal Clean Water Act. Section 303 of the Clean Water Act requires states to adopt water quality standards which "consist of the designated uses of the navigable waters involved and the water quality criteria for such waters based upon such uses." According to Section 13050 of the California Water Code, Basin Plans consist of a designation or establishment for the waters within a specified area of beneficial uses to be protected, water quality objectives to protect those uses, and a program of implementation needed for achieving the objectives. State law also requires that Basin Plans conform to the policies set forth in the Water Code beginning with Section 13000 and any state policy for water quality control. Since beneficial uses, together with their corresponding water quality objectives, can be defined per federal regulations as water quality standards, the Basin Plans are regulatory references for meeting the state and federal requirements for water quality control (40 CFR 131.20). One significant difference between the state and federal programs is that California's basin plans establish standards for ground waters in addition to surface waters. Basin Plans are adopted and amended by Regional Water Boards under a structured process involving full public participation and state environmental review. Basin Plans and amendments thereto, do not become effective until approved by the State Water Resources Control Board (State Water Board). Regulatory provisions must be approved by the Office of Administrative Law. Adoption or revision of surface water standards are subject to the approval of the U.S. Environmental Protection Agency. Basin Plans complement water quality control plans adopted by the State Water Board, such as the Water Quality Control Plans for Temperature Control and Ocean Waters. It is the intent of the State and Regional Water Boards to maintain the Basin Plans in an updated and readily available edition that reflects the current water quality control program. This Basin Plan covers the entire Sacramento and San Joaquin River Basins. A separate Basin Plan covers the Tulare Lake Basin. The Basin Plan was first adopted in 1975. In 1989, a second edition was published. The second edition incorporated all the amendments which were adopted and approved since 1975, updated the Basin Plan to include new state policies and programs, restructured and edited the Basin Plan for clarity, and incorporated the results of triennial reviews conducted in 1984 and 1987. The Third Edition - 1994 incorporated all amendments approved between 1989 and 1994, included new state policies and programs, edited and restructured the Basin Plan to make it consistent with other regional and state plans, and substantively amended sections dealing with beneficial uses, objectives, and implementation programs. The current edition (Fourth Edition - 1998) incorporates two new amendments approved since 1994. One amendment deals with compliance schedules in permits and the other addresses agricultural subsurface drainage discharges. In this Basin Plan, "Regional Water Board" refers to the Central Valley Regional Water Quality Control Board and "State Water Board" refers to the State Water Resources Control Board. Appendix Updates and amendments  are at the State Water Board "Basin Plan" page