Ground-Water Resources of Honey Lake Valley, Lassen County, California, and Washoe County, Nevada

U.S. Geological Survey (USGS) | December 15th, 1990

Honey Lake Valley is a 2,200-square-mile, northwest-trending, topographically closed basin about 35 miles northwest of Reno, Nevada. Unconsolidated basin-fill deposits on

Honey Lake Valley is a 2,200-square-mile, northwest-trending, topographically closed basin about 35 miles northwest of Reno, Nevada. Unconsolidated basin-fill deposits on the valley floor and fractured volcanic rocks in the northern and eastern uplands are the principal aquifers. Ground water in the Nevada part of the basin is being considered as a potential source of public supply to the Reno area. This report describes the ground-water resources of the basin and the potential hydrologic effects of ground-water development in its eastern part. During an average year, about 1.1 million acre-feet of precipitation falls on the 1,700-square-mile study area within the valley, and an estimated 86,000 acre-feet enters the study area as streamflow in the Susan River and Long Valley Creek. Almost 90 percent of this water runs off, evaporates, or is transpired by plants before it can infiltrate and become ground-water recharge; this includes about 130,000 acre-feet per year that reaches Honey Lake as surface-water inflow. About 130,000 acre-feet recharges the aquifer system annually, about 40 percent by direct infiltration of precipitation over the study area and about 60 percent by infiltration of streamflow and irrigation water. Balancing this is an equal amount of ground-water discharge, of which about 65 percent evaporates from the water table or is transpired by phreatophytes, about 30 percent is withdrawn from wells, and about 5 percent leaves the basin as subsurface outflow to the east. A ground-water flow model of the eastern part of the study area, where withdrawals for public supply have been proposed, was used to evaluate components of the water budget and to estimate the long-term hydrologic effects of hypothetical increased development. Results of the evaluation indicate conditions under which a new equilibrium would be established if 15,000 acre-feet of water were withdrawn from the Fish Springs Ranch area annually. The model indicates that, as a result of such an increase in pumpage, water levels would decline more than 100 feet from present (1988) levels in the vicinity of the pumping, and as much as 40 feet at the California-Nevada State line. Evapotranspiration and subsurface outflow to the east would each be reduced by about 60 percent, but hydrologic effects would be minimal at the western boundary of the flow-model area (just east of Honey Lake). Within the modeled area, the simulation indicates that the increased withdrawals would cause the net flow of ground water eastward across the State line to increase from about 700 acre-feet per year to about 2,300 acre-feet per year.

Groundwater Accounting Platform — Real-World Impact from DWR Investment in Open, Scalable SGMA Tools

Environmental Defense Fund (EDF) | November 3rd, 2025

Groundwater and Stream Interaction in California's Central Valley: Insights for Sustainable Groundwater Management

Nature Conservancy | June 16th, 2016

Sustainable water management requires ensuring ecosystem water needs are met in balance with water needs for people. The Nature Conservancy (TNC) is working across Califo

Sustainable water management requires ensuring ecosystem water needs are met in balance with water needs for people. The Nature Conservancy (TNC) is working across California to demonstrate how to achieve this balance in the context of integrated water management programs. Sustainable water management must also recognize that surface water and groundwater resources are interconnected and that proper management of these resources includes understanding this interaction and managing the resources accordingly. Management of groundwater and surface water systems in an integrated manner is impeded by California water law and policy, which has separate rules and regulations for managing groundwater and surface water resources. The Central Valley of California is the hub of the state’s water supply system. An extensive network of dams and canals supplies surface water to users within the Central Valley as well as to the San Francisco Bay Area, the Central Coast, and Southern California. Analysis of information collected in this study reveals that just within the Central Valley, agricultural and urban sectors use an average of 13 million acre-feet (MAF) of surface water and over 8 MAF of groundwater per year. Approximately 2 MAF of water is exported annually to areas outside the Central Valley. Because the availability of surface water supplies varies significantly from year to year, groundwater use also varies considerably on annual basis. In an average year, groundwater meets about 40% of the state’s water demand and up to 60% or more during droughts, when groundwater provides a water supply buffer against economic and environmental harm from water scarcity (DWR, 2014). In some areas, groundwater provides 100% of the supply, even in wetter years, and then is heavily pumped during drought. In other locations, where surface water supplies are reasonably abundant, groundwater use may be relatively light during wetter years, but more heavily pumped during drier years when surface water supplies are cut back. Accordingly, the impact of groundwater use is much more evident during dry years, and especially in drought conditions. A case in point is the drought condition of 2013-15. This drought is exerting significant stress on the state’s water supply. The surface water deliveries have been reduced dramatically, to near zero in many regions; therefore, agricultural and municipal water users in the Central Valley and other parts of the state that normally rely on surface water for much of their supplies, are now greatly increasing their use of groundwater to meet their needs. A 2014 UC Davis report indicates that expected increase in Central Valley groundwater pumping would be in the range of 20% to 25%, during the 2014 irrigation season. To the authors’ knowledge, there are no reports of actual estimates of increase in groundwater use for the recent drought conditions. The long-term increase in groundwater pumping and especially recent drought related increases in pumping would translate into significantly more adverse impacts on the surface water and stream systems, as well as groundwater dependent ecosystems. In addition, this increase in groundwater pumping could potentially result in more land subsidence throughout the valley. The drought has also affected the irrigated lands under cultivation. A November 2014 DWR publication “Public Update for Drought Response” 3 reported that based on NASA satellite imagery, approximately 700,000 acres of land were estimated idled between 2011 and 2014. Majority of these acreages idled are reported to be due to the drought conditions, although, some were also due to normal agronomic practices, crop markets, and other reasons. This report provides the results of a number of analyses and evaluations of Central Valley hydrologic conditions using the California Central Valley Groundwater-Surface Water Simulation Model (C2VSim). The study examines important hydrologic and operational characteristics and behaviors of the California’s Central Valley water system during the historical development in the Valley. In addition, the study presents results of model simulations conducted to assess potential impacts of several water management scenarios. The results of this study contribute significantly to the understanding of how management of groundwater and surface water are interrelated and will inform the development of more effective integrated water management in the Central Valley and throughout California. The interaction between groundwater and surface water resources has been evaluated and illustrated by many researchers. As early as 1941, Theis (1941) documented the hydraulic connection between stream and aquifer systems and quantitatively described the general behavior of stream-groundwater systems. Many others, including Glover & Balmer (1954) and Hantush (1965) built on Theis’ work, which demonstrated and confirmed the basic principles of hydraulic connection between stream and aquifer systems. In recent years, significant work has been conducted regarding regional impacts of groundwater pumping and operation on regional surface water systems. For example, the recent USGS study (Barlow & Leake, 2012) presents original findings of the stream-aquifer interaction in the context of sustainable groundwater management. In an effort to quantify the interaction between the groundwater and the surface water system, DWR’s C2VSim model was employed in this study. The C2VSim model was originally developed in 1990 for DWR, U. S. Bureau of Reclamation (USBR), and California State Water Resources Control Board (SWRCB) as the Central Valley Groundwater and Surface water Model (CVGSM) (James M. Montgomery Consulting Engineers, 1990a). Subsequently, the model was enhanced through numerous key applications, including the Central Valley Project Improvement Act – Programmatic Environmental Impact Statement (CVPIA-PEIS). In 2005, the CVGSM model was upgraded to the newly developed Integrated Water Flow Model (IWFM) platform, and was renamed the C2VSim model. The detailed features of the model are described and presented in Section 2 of this report. The C2VSim model is a leading Central Valley-wide integrated hydrologic model adopted by DWR and many other regional and state-wide agencies, as well as non-governmental organizations (NGOs) to evaluate various water management scenarios throughout the Valley. This report is organized in six sections: Section 1: Provides the background information and lays out the goals and objectives of this study. Section 2: Provides information on the status of C2VSim model, refinements made during this study, and assumptions on the modeling analysis. Section 3: Discusses simulation of the historical hydrologic conditions in the Central Valley. Section 4: Provides the assumptions and results of the existing baseline conditions, assuming that no changes to the facilities and their operations, as well as water management actions, take place over the course of a predetermined hydrologic condition. Section 5: Provides a description of three water management scenarios that may have major impacts on the future of surface water and groundwater interaction in Central Valley. Results of simulation of these management scenarios are presented and discussed in detail. Section 6: Provides conclusions from this study and a list of recommendations for future work.

Groundwater and Urban Growth in the San Joaquin Valley

Public Policy Institute of California (PPIC) | September 20th, 2021

The San Joaquin Valley is ground zero for the Sustainable Groundwater Management Act (SGMA). It has the largest groundwater deficit in California and faces some of the

The San Joaquin Valley is ground zero for the Sustainable Groundwater Management Act (SGMA). It has the largest groundwater deficit in California and faces some of the worst impacts from overdraft, including land subsidence and drying wells. SGMA will help the region address these issues—while also building its climate resilience. But this will require hard work, not only by farmers—the largest groundwater users—but also by the valley’s urban water utilities, which serve a growing population while relying mostly on groundwater. As the valley confronts limits on groundwater pumping, urban utilities, local land use authorities, other water users, and state agencies must all engage to ensure a smooth transition for the region’s residents.

Groundwater Availability of the Central Valley Aquifer

U.S. Geological Survey (USGS) | July 15th, 2009

California’s Central Valley covers about 20,000 square miles and is one of the most productive agricultural regions in the world. More than 250 different crops are grow

California’s Central Valley covers about 20,000 square miles and is one of the most productive agricultural regions in the world. More than 250 different crops are grown in the Central Valley with an estimated value of $17 billion per year. This irrigated agriculture relies heavily on surface-water diversions and groundwater pumpage. Approximately one-sixth of the Nation’s irrigated land is in the Central Valley, and about one-fifth of the Nation’s groundwater demand is supplied from its aquifers. The Central Valley also is rapidly becoming an important area for California’s expanding urban population. Since 1980, the population of the Central Valley has nearly doubled from 2 million to 3.8 million people. The Census Bureau projects that the Central Valley’s population will increase to 6 million people by 2020. This surge in population has increased the competition for water resources within the Central Valley and statewide, which likely will be exacerbated by anticipated reductions in deliveries of Colorado River water to southern California. In response to this competition for water, a number of water-related issues have gained prominence: conservation of agricultural land, conjunctive use, artificial recharge, hydrologic implications of land-use change, and effects of climate variability. To provide information to stakeholders addressing these issues, the USGS Groundwater Resources Program made a detailed assessment of groundwater availability of the Central Valley aquifer system, that includes: (1) the present status of groundwater resources; (2) how these resources have changed over time; and (3) tools to assess system responses to stresses from future human uses and climate variability and change. This effort builds on previous investigations, such as the USGS Central Valley Regional Aquifer System and Analysis (CV-RASA) project and several other groundwater studies in the Valley completed by Federal, State and local agencies at differing scales. The principal product of this new assessment is a tool referred to as the Central Valley Hydrologic Model (CVHM) that accounts for integrated, variable water supply and demand, and simulates surface-water and groundwater-flow across the entire Central Valley system. The development of the CVHM comprised four major elements: (1) a comprehensive Geographic Information System (GIS) to compile, analyze and visualize data; (2) a texture model to characterize the aquifer system;(3) estimates of water-budget components by numerically modeling the hydrologic system with the Farm Process (FMP); and (4) simulations to assess and quantify hydrologic conditions. Chapter A: Introduction, Overview of Hydrogeology, and Textural Model of California’s Central Valley Chapter B: Groundwater Availability in California’s Central Valley Chapter C:  Numerical Model of the Hydrologic Landscape and Groundwater Flow in California’s Central Valley Appendix 1: Supplemental Information—Modifications to Modflow-2000 Packages and Processes

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 depletion in California’s Central Valley accelerates during megadrought

Nature Portfolio (Springer Nature) | December 19th, 2022

Groundwater provides nearly half of irrigation water supply, and it enables resilience during drought, but in many regions of the world, it remains poorly, if at all mana

Groundwater provides nearly half of irrigation water supply, and it enables resilience during drought, but in many regions of the world, it remains poorly, if at all managed. In heavily agricultural regions like California’s Central Valley, where groundwater management is being slowly implemented over a 27-year period that began in 2015, groundwater provides two–thirds or more of irrigation water during drought, which has led to falling water tables, drying wells, subsiding land, and its long-term disappearance. Here we use nearly two decades of observations from NASA’s GRACE satellite missions and show that the rate of groundwater depletion in the Central Valley has been accelerating since 2003 (1.86 km3/yr, 1961–2021; 2.41 km3/yr, 2003–2021; 8.58 km3/yr, 2019–2021), a period of megadrought in southwestern North America. Results suggest the need for expedited implementation of groundwater management in the Central Valley to ensure its availability during the increasingly intense droughts of the future.

Groundwater Flow Model of the East and South Las Posas Sub-Basins – Preliminary Draft Report

Calleguas Municipal Water District (CMWD) | January 17th, 2018

INTERA Incorporated (INTERA) was retained by the Calleguas Municipal Water District (CMWD) to develop a numerical groundwater model of the East Las Posas Management Area

INTERA Incorporated (INTERA) was retained by the Calleguas Municipal Water District (CMWD) to develop a numerical groundwater model of the East Las Posas Management Area (ELPMA), which includes the locally-recognized east and south sub-basins of the Las Posas Valley Basin (LPVB). Groundwater in the ELPMA is found in a multiple-aquifer system characterized by intense faulting and folding, which is known to exert structural controls on groundwater flow and movement. The ELPMA is known to receive recharge from surface water flows in Arroyo Las Posas/Simi that runs east to west along the southern edge of the basin. Flows in the Arroyo have become perennial as a result of discharges from wastewater treatment plants and dewatering wells within and upstream of the ELPMA. Hence, understanding and modeling the surface-water/groundwater interaction along the Arroyo is an important component of the numerical model development. CMWD also owns and operates the Las Posas Basin Aquifer Storage and Recovery (ASR) Project, consisting of eighteen high capacity ASR wells and associated facilities located in the ELPMA that are used to inject and recover potable water purchased from Metropolitan Water District of Southern California (Metropolitan). Basin response to injection/extractions at the ASR well fields and the evaluation of storage capacity of the ASR well field are key considerations for this modeling project. 

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 Quality in the San Fernando–San Gabriel Groundwater Basins, California

U.S. Geological Survey (USGS) | March 31st, 2012