California’s Groundwater Conditions: Semi-Annual Update, October 2023, Fall Bulletin 118 Information Update

California Department of Water Resources (DWR) | October 12th, 2023

This semi-annual report presents data received by DWR as of August 31, 2023, and partially reflects the impacts of recent storms, flooding, and natural and managed aquife

This semi-annual report presents data received by DWR as of August 31, 2023, and partially reflects the impacts of recent storms, flooding, and natural and managed aquifer recharge. However, it should be noted that groundwater response is a slow process and takes months to years to fully respond to changes in surface water conditions.

California’s groundwater overdraft: An environmental Ponzi scheme?

Journal of Hydrology (Elsevier) | January 23rd, 2023

Groundwater levels have been decreasing in most agricultural areas, motivating research to find optimal solutions to balance socio-economical and environmental demands. T

Groundwater levels have been decreasing in most agricultural areas, motivating research to find optimal solutions to balance socio-economical and environmental demands. Traditionally, groundwater optimization aims at long-term profit maximization, while accounting for the extraction costs. Following this approach, we find exploitation protocols characterized by pumping rates that slowly decrease in time toward a long-term sustainable value. However, the comparison of the model prediction with water extraction data for the period 1985–2021 from Kern County in California points out the inconsistencies between real management and long-term optimal behavior. Rather, the observed trajectory resembles those obtained by finite-time optimization horizons, which provide short-term high profits by over-drafting, while leading to long-term dilapidation of the capital and the exhaustion of the aquifer. Such myopic planning results in a Ponzi scheme for groundwater extraction. Like the infamous fraudulent scheme, ‘more-than-optimal’ profits are achievable by excessive short-term consumption by the early investors (the past and current aquifer exploiters), leaving the later comers (the future generations) with an impossible cost to sustain. Including the environmental costs of aquifer over-exploitation, the myopic nature of human planning can be corrected and reconciled with a more sustainable use of groundwater.

California’s Groundwater Update 2013: A Compilation of Enhanced Content for California Water Plan Update 2013

California Department of Water Resources (DWR) | April 1st, 2015

The primary goal of California’s Groundwater Update 2013: A Compilation of Enhanced Content for California Water Plan Update 2013 (California’s Groundwater Update 201

The primary goal of California’s Groundwater Update 2013: A Compilation of Enhanced Content for California Water Plan Update 2013 (California’s Groundwater Update 2013) is to provide foundational information to improve the statewide and regional understanding of groundwater conditions and management programs. The set of data, information, and analyses developed by the California Department of Water Resources (DWR) will help set the stage for future Bulletin 118 and California Water Plan updates, and help local and regional agencies plan for sustainable groundwater management by providing an on-going reporting of essential groundwater data, information, and analyses. A second goal is to identify data gaps and groundwater management challenges that are meant to serve as a guidepost for prioritizing future groundwater data collection and funding opportunities. The final goal is to develop a set of recommendations to improve groundwater management in California. Findings, data gaps, and recommendations were developed for the state as a whole and for each of the 10 hydrologic regions. Statewide findings, data gaps, and recommendations presented herein serve as a summary of those commonly identified at the regional level.

California’s Groundwater: Bulletin 118 — Update 2025 Highlights

California Department of Water Resources (DWR) | October 20th, 2025

California’s Groundwater: Bulletin 118 — Update 2025 (CalGW Update 2025) serves as the most up-to-date and comprehensive compendium of statewide data and information

California’s Groundwater: Bulletin 118 — Update 2025 (CalGW Update 2025) serves as the most up-to-date and comprehensive compendium of statewide data and information on the occurrence, nature, uses, management, climate change vulnerability, monitoring, and conditions of California’s groundwater resources. Building on the legacy of Bulletin 118 and past California Water Plans, CalGW Update 2025 synthesizes recent data — available up to December 2023 — and closes key knowledge gaps to inform more effective statewide groundwater planning and decision-making.  CalGW Update 2025 consists of this Highlights document and a detailed statewide report, supported by a series of appendices. 

California’s Severe Drought Has Only Marginal Impacts on Food Prices

University of California Giannini Foundation of Agricultural Economics | May 14th, 2015

The extreme drought that has gripped California over the past several years is causing onerous adjustments in the natural and human environments. Agriculture, which uses

The extreme drought that has gripped California over the past several years is causing onerous adjustments in the natural and human environments. Agriculture, which uses much of the state’s water, is at the center of many of these arduous responses. The 2015 impacts of the continuing drought are still underway, but in this special Agriculture and Resource Economics Update issue, we project responses and consequences within agriculture and more broadly. In this issue, Hanak and Mount put this drought in the context of California’s history and put agriculture in the context of water institutions, management, and distribution throughout the state. Next, Medellin-Azuara and co-authors develop detailed, and albeit preliminary, assessments of 2015 irrigation water distribution. They estimate a cut to agriculture of about 8.8 million acre-feet, or about 30% of what might be available in a normal year. (This number may be an underestimate given recent events.) During droughts, farms increase groundwater pumping. The authors estimate that farmers and ranchers will replace about 6.2 million acre-feet of lost surface water deliveries with costly increases in groundwater pumping, where possible in 2015. Another painful response to drought is to leave land idle. The authors estimate about 564,000 more acres, mostly field crop land in the Central Valley (including irrigated pastures), will be idled in 2015. This too may be an underestimate. USDA reported on June 30, that 2015 California acreage of “principal crops,” (defined as field crops such as hay, grains, oilseeds, cotton and potatoes) is about 900,000 acres below the 2013 total of about four million acres. Over this period, tree nut and tomato acreage increased by about 180,000 acres. So, even accounting for the steady shift to tree nuts and some other higher revenue per acre (and per acre-foot) crops, there is a strong indication of severely accelerated reductions in field crop acreage in California. The economic toll of the drought is fewer jobs and smaller value of output and economic contribution that would have otherwise occurred. Based on 564,000 idled acres, Howitt et al. estimates farm revenue losses of $1.8 billion, economy-wide revenue losses of $2.7 billion, and 18,600 fewer jobs due to the agricultural drought. That these economic impacts are not even larger is a testament to the extraordinary efforts and innovations by farmers, and others in California agriculture. Idling land, shifting water across crops, and using each acre-foot more economically all have led to smaller losses of revenue and jobs, and only very small price increases for consumers.

California’s Sustainable Groundwater Management Act and the Half-Exemption of Owens Valley Groundwater Basin

University of California, Los Angeles (UCLA) | May 1st, 2024

This Comment first uses historical accounts and secondary sources to describe the history of Owens Valley groundwater. It next describes the Governing Documents that curr

This Comment first uses historical accounts and secondary sources to describe the history of Owens Valley groundwater. It next describes the Governing Documents that currently manage this groundwater. It ends its history by relying on the content of OVGA meetings to tell the recent story of SGMA’s implementation in Owens Valley.

California’s Water Market, By the Numbers, Update 2012

Public Policy Institute of California (PPIC) | November 21st, 2012

This report provides a check-up on California’s progress with two innovative water management tools: water marketing and groundwater banking. These tools are part o

This report provides a check-up on California’s progress with two innovative water management tools: water marketing and groundwater banking. These tools are part of a modern approach that will enable California to manage its scarce water resources more flexibly and sustainably.

California’s Water Market, By the Numbers, Update 2021

Public Policy Institute of California (PPIC) | December 31st, 2021

This appendix serves as an update to the data on surface water trading and groundwater banking provided in the PPIC publication, California’s Water Market, By the Numb

This appendix serves as an update to the data on surface water trading and groundwater banking provided in the PPIC publication, California’s Water Market, By the Numbers: Update 2012 (Hanak and Stryjewski 2012). In each section, we describe data sources and methods and present summary statistics.

Can Los Osos Valley Groundwater Basin Provide a Sustainable Water Supply?

California State University, Monterey Bay (CSUMB) | September 16th, 2010

The aquifers underlying the community of Los Osos in California are impaired by nitrate pollution from septic systems (shallow aquifers) and saltwater intrusion f

The aquifers underlying the community of Los Osos in California are impaired by nitrate pollution from septic systems (shallow aquifers) and saltwater intrusion from overdraft (lower aquifers). The development of a centralized waste water system, now in the final pre- construction stages, is proceeding concurrently with an adjudicated basin planning process involving local water purveyors in an effort to develop a management plan for a sustainable basin and water supply. Development of the wastewater system aimed at protecting the shallow aquifer has highlighted the need for a comprehensive groundwater basin management plan that focuses the County, the local water purveyors, the residents, and resource agencies on a common set of actions to stop seawater intrusion and protect the entire basin. The final basin management plan will be scrutinized and critiqued as a potential model for myriad other hydrologically independent communities that are, or will soon be, undergoing the similar quest for reliable water. Stakeholders in the Los Osos Valley Water Basin have the opportunity to lead coastal California on the difficult path toward sustainable water supply through creative local solutions that do not presume the long-term viability of imported water or desalination. While there are a number of detailed analyses and suggested actions in this report, the overarching conclusions/recommendations include: The saltwater intrusion models used in the draft EIR and technical memoranda (TMs) recently developed for the purveyor basin planning process attempt to balance saltwater intrusion against inputs and outputs to and from the aquifers. The net groundwater extraction amounts simulated in the models (corresponding to the purported safe yields) are considered aggressive (too much extraction) because they do not stabilize, or result in seaward migration, of the saltwater/freshwater interface (toward the northwest). In fact, the TM safe yield may allow the saltwater to move inland, especially if California climate becomes drier, as projected by State Government. Modeling results presented in our report indicate that if rainfall patterns persist as they have in the past, there is a reasonable chance that saltwater intrusion will progress farther, rather than remain stable, under anticipated pumping conditions. Further investigation is recommended to resolve uncertainties associated with the TM safe yields, including permeability of the regional (AT2) aquitard, how the AT2 affects lower aquifer recharge, and whether sufficient recharge will occur to prevent seawater intrusion in the upper aquifer. These uncertainties are under- appreciated in the EIR and TMs. We recommend the development of a “contingency plan” that allows flexible adaptive management to address unintended consequences that may occur following the implementation of the Los Osos Valley Wastewater Plan. Contingency plans identify mission-critical sections of the plan that have uncertainties, recommend monitoring to ascertain progress of the plan, and define remedial actions that will mitigate various unintended consequences, including divergence from, or failure of the plan. Several mission-critical arenas are discussed in the report. Rooftop rainwater harvesting and low impact development (LID) options could produce a substantial amount of water for local irrigation, reducing potable water use, while also augmenting groundwater recharge. Some LID alternatives, e.g., rain gardens and vegetated swales, can also provide attractive low-water using landscape features that may also help Los Osos residents adapt to the potential changes in groundwater levels and soil moisture content resulting from project implementation that may affect landscaping. Both on-site and community LID features will also reduce pollution of surface waters in the area. While the method used to calculate potential basin recharge from rainwater and LID features in this report is inconclusive, it suggests that the benefits of these measures may be considerable. Rainwater harvesting and LID are proven technologies that should be considered on a broad basis in the Los Osos Valley to help balance the basin and adapt to potential impacts from the project. Treatment wetlands can provide economical, efficient waste water treatment systems and/or the means to provide additional treatment, storage, and recharge of the groundwater basin. They also provide habitat and quality of life benefits (open space and passive recreational opportunities, such as hiking trails). Nitrate removal in wetlands has been studied in small scale experiments in Monterey County, has been implemented in large scale applications with positive success. Wetlands to treat surface water and wastewater have been used successfully in many communities around the world. We recommend an emphasis on agricultural exchange to maximize its benefits on seawater intrusion and help balance the basin. Tertiary-treated waste water is safe for irrigation and can reduce groundwater pumping, as well as energy and fertilizer use for farmers, with related costs savings. When well water from farms is exchanged for recycled water, potable water can be used to offset pumping causing seawater intrusion. While it is best to balance the hydrologic budget using resources within the basin, there is also an option to trade agricultural-grade treated water to regional farms in exchange for drinking grade water from wells outside the basin if ample water reserves are developed in the future. The draft Los Osos Valley sustainable water basin management plan, “Achieving a sustainable Los Osos Valley Water Basin: Framework for a 21st century basin management plan” (Wimer 2009) presents realistic, well-supported solutions for addressing the water needs of the Los Osos Community using sustainable, water saving and LID methods while preserving the basin for future use. The plan integrates methods reviewed in this report (rainwater harvesting, LID, and agriculture exchange), with urban reuse and intensive indoor and outdoor conservation to balance the basin and provide flows to sensitive ecosystems, with margins of safety that also address current and future uncertainties. We recommend that the plan is further developed, possibly with the help of water use efficiency expert, and considered for implementation. To answer the question posed by the title--yes, Los Osos can become a model of sustainable water use for coastal California if stakeholders implement reasonable conservation measures to complement an appropriate waste water treatment strategy and an adaptive management plan. The great number of uncertainties in the system makes any plan “experimental.” Given the uncertainties, due diligence will include erring on the side of caution (being conservative, not aggressive, in planned groundwater production), and devising a realistic contingency plan that includes adaptive management strategies. The Advanced Watershed Science and Policy (ENVS 660) graduate course at California State University Monterey Bay produced this report. It presents the results of extensive literature review, synthesis, and new analyses. The breadth of the report spans many of the key water supply issues facing the people of the Los Osos Valley. It provides information that can help this region move toward a sustainable water supply through innovative waste water management and sound conservation measures.

Carbon Sequestration and Subsidence Reversal in the Sacramento–San Joaquin Delta and Suisun Bay: Management Opportunities for Climate Mitigation and Adaptation

University of California, Davis (UC Davis) | August 28th, 2023