A geohydrologic reconnaissance of the Saratoga Spring area, Death Valley National Monument, California

U.S. Geological Survey (USGS) | March 1st, 1966

Annual Ground-Water Discharge by Evapotranspiration from Areas of Spring-Fed Riparian Vegetation Along the Eastern Margin of Death Valley, 2000–02

U.S. Geological Survey (USGS) | July 1st, 2006

Coupling a spatiotemporally distributed soil water budget with stream-depletion functions to inform stakeholder-driven management of groundwater-dependent ecosystems

Water Resources Research, American Geophysical Union | November 12th, 2013

Groundwater pumping, even if only seasonal, may significantly impact groundwater-dependent ecosystems through increased streamflow depletion, particularly in semiarid and

Groundwater pumping, even if only seasonal, may significantly impact groundwater-dependent ecosystems through increased streamflow depletion, particularly in semiarid and arid regions. The effects are exacerbated, under some conditions, by climate change. In social sciences, the management of groundwater-dependent ecosystems is generally considered a “wicked” problem due to the complexity of affected stakeholder groups, disconnected legal frameworks, and a divergence of policies and science at the cross road between groundwater and surface water, and between ecosystems and water quality. A range of often simplified scientific tools plays an important role in addressing such problems. Here we develop a spatiotemporally distributed soil water budget model that we couple with an analytical model for stream depletion from groundwater pumping to rapidly assess seasonal impacts of groundwater pumping on streamflow during critical low flow periods. We demonstrate the applicability of the tool for the Scott Valley in Northern California, where protected salmon depend on summer streamflow fed by cool groundwater. In this example, simulations suggest that increased recharge in the period immediately preceding the critical low streamflow season, and transfer of groundwater pumping away from the stream are potentially promising tools to address ecosystem concerns, albeit raising difficult infrastructure and water trading issues. In contrast, additional winter recharge at the expense of later spring recharge, whether intentional or driven by climate may reduce summer streamflows. Comparison to existing detailed numerical groundwater model results suggests that the coupled soil water mass balance—stream depletion function approach provides a viable tool for scenario development among stakeholders, to constructively inform the search for potential solutions, and to direct more detailed, complex site-specific feasibility studies. The tool also identifies important field monitoring efforts needed to improve the understanding and quantification of site-specific groundwater-stream interactions.

Coupling a spatiotemporally distributed soil water budget with stream‐depletion functions to inform stakeholder‐driven management of groundwater‐dependent ecosystems

American Geophysical Union (AGU) | November 12th, 2013

Groundwater pumping, even if only seasonal, may significantly impact groundwater‐dependent ecosystems through increased streamflow depletion, particularly in semiarid a

Groundwater pumping, even if only seasonal, may significantly impact groundwater‐dependent ecosystems through increased streamflow depletion, particularly in semiarid and arid regions. The effects are exacerbated, under some conditions, by climate change. In social sciences, the management of groundwater‐dependent ecosystems is generally considered a “wicked” problem due to the complexity of affected stakeholder groups, disconnected legal frameworks, and a divergence of policies and science at the cross road between groundwater and surface water, and between ecosystems and water quality. A range of often simplified scientific tools plays an important role in addressing such problems. Here we develop a spatiotemporally distributed soil water budget model that we couple with an analytical model for stream depletion from groundwater pumping to rapidly assess seasonal impacts of groundwater pumping on streamflow during critical low flow periods. We demonstrate the applicability of the tool for the Scott Valley in Northern California, where protected salmon depend on summer streamflow fed by cool groundwater. In this example, simulations suggest that increased recharge in the period immediately preceding the critical low streamflow season, and transfer of groundwater pumping away from the stream are potentially promising tools to address ecosystem concerns, albeit raising difficult infrastructure and water trading issues. In contrast, additional winter recharge at the expense of later spring recharge, whether intentional or driven by climate may reduce summer streamflows. Comparison to existing detailed numerical groundwater model results suggests that the coupled soil water mass balance—stream depletion function approach provides a viable tool for scenario development among stakeholders, to constructively inform the search for potential solutions, and to direct more detailed, complex site‐specific feasibility studies. The tool also identifies important field monitoring efforts needed to improve the understanding and quantification of site‐specific groundwater‐stream interactions.

Depletion and Capture: Revisiting “The Source of Water Derived from Wells”

National Ground Water Association (NGWA) | May 28th, 2014

A natural consequence of groundwater withdrawals is the removal of water from subsurface storage, but the overall rates and magnitude of groundwater depletion and capture

A natural consequence of groundwater withdrawals is the removal of water from subsurface storage, but the overall rates and magnitude of groundwater depletion and capture relative to groundwater withdrawals (extraction or pumpage) have not previously been well characterized. This study assesses the partitioning of long‐term cumulative withdrawal volumes into fractions derived from storage depletion and capture, where capture includes both increases in recharge and decreases in discharge. Numerical simulation of a hypothetical groundwater basin is used to further illustrate some of Theis' (1940) principles, particularly when capture is constrained by insufficient available water. Most prior studies of depletion and capture have assumed that capture is unconstrained through boundary conditions that yield linear responses. Examination of real systems indicates that capture and depletion fractions are highly variable in time and space. For a large sample of long‐developed groundwater systems, the depletion fraction averages about 0.15 and the capture fraction averages about 0.85 based on cumulative volumes. Higher depletion fractions tend to occur in more arid regions, but the variation is high and the correlation coefficient between average annual precipitation and depletion fraction for individual systems is only 0.40. Because 85% of long‐term pumpage is derived from capture in these real systems, capture must be recognized as a critical factor in assessing water budgets, groundwater storage depletion, and sustainability of groundwater development. Most capture translates into streamflow depletion, so it can detrimentally impact ecosystems.

Evaluation of the Hydrologic System and Selected Water-Management Alternatives in the Owens Valley, California

U.S. Geological Survey (USGS) | May 9th, 2000

The Owens Valley, a long, narrow valley along the east side of the Sierra Nevada in east-central California, is the main source of water for the city of Los Angeles. The

The Owens Valley, a long, narrow valley along the east side of the Sierra Nevada in east-central California, is the main source of water for the city of Los Angeles. The city diverts most of the surface water in the valley into the Owens River–Los Angeles Aqueduct system, which transports the water more than 200 miles south to areas of distribution and use. Additionally, ground water is pumped or flows from wells to supplement the surface-water diversions to the river–aqueduct system. Pumpage from wells needed to supplement water export has increased since 1970, when a second aqueduct was put into service, and local residents have expressed concerns that the increased pumping may have a detrimental effect on the environment and the native vegetation (indigenous alkaline scrub and meadow plant communities) in the valley. Native vegetation on the valley floor depends on soil moisture derived from precipitation and from the unconfined part of a multilayered ground-water system. This report, which describes the evaluation of the hydrologic system and selected water-management alternatives, is one in a series designed to identify the effects that ground-water pumping has on native vegetation and evaluate alternative strategies to mitigate any adverse effects caused by pumping. The hydrologic system of the Owens Valley can be conceptualized as having three parts: (1) an unsaturated zone affected by precipitation andevapotranspiration; (2) a surface-water system composed of the Owens River, the Los Angeles Aqueduct, tributary streams, canals, ditches, and ponds; and (3) a saturated ground-water system contained in the valley fill. Analysis of the hydrologic system was aided by development of a ground-water flow model of the “aquifer system,” which is defined as the most active part of the ground-water system and which includes nearly all of the Owens Valley except for the area surrounding the Owens Lake. The model was calibrated and verified for water years 1963–88 and used to evaluate general concepts of the hydrologic system and the effects of past water-management practices. The model also was used to evaluate the likely effects of selected water-management alternatives designed to lessen the adverse effects of ground-water pumping on native vegetation. Results of the model simulations confirm that a major change in the hydrologic system was caused by the additional export of water from the valley beginning in 1970. Average ground-water pumpage increased by a factor of five, discharge from springs decreased almost to zero, reaches of the Owens River that previously had gained water from the aquifer system began losing water, and total evapotranspiration by native plants decreased by about 35 percent. Water-management practices as of 1988 were defined and evaluated using the model. Simulation results indicate that increased ground-water pumpage since 1985 for enhancement and mitigation projects within the Owens Valley has further stressed the aquifer system and resulted in declines of the water table and reduced evapotranspiration. Most of the water-table declines are beneath the western alluvial fans and in the immediate vicinity of production wells. The water-table altitude beneath the valley floor has remained relatively constant over time because of hydrologic buffers, such as evapotranspiration, springs, and permanent surface-water features. These buffers adjust the quantity of water exchanged with the aquifer system and effectively minimize variations in water-table altitude. The widespread presence of hydrologic buffers is the primary reason the water-table altitude beneath the valley floor has remained relatively constant since 1970 despite major changes in the type and location of ground-water discharge. Evaluation of selected water-management alternatives indicates that long-term variations in average runoff to the Owens Valley of as much as 10 percent will not have a significant effect on the water-table altitude. However, reductions in pumpage to an average annual value of about 75,000 acre-ft/yr are needed to maintain the water table at the same altitude as observed during water year 1984. A 9-year transient simulation of dry, average, and wet conditions indicates that the aquifer system takes several years to recover from increased pumping during a drought, even when followed by average and above-average runoff and recharge. Increasing recharge from selected tributary streams by additional diversion of high flows onto the alluvial fans, increasing artificial recharge near well fields, and allocating more pumpage to the Bishop area may be useful in mitigating the adverse effects on native vegetation caused by drought and short-term increases in pumpage. Analysis of the optimal use of the existing well fields to minimize drawdown of the water table indicates no significant lessening of adverse effects on native vegetation at any of the well fields at the end of a 1-year simulation. Some improvement might result from pumping from a few high-capacity wells in a small area, such as the Thibaut–Sawmill well field; pumping from the upper elevations of alluvial fans, such as the Bishop well field; or pumping in an area surrounded by irrigated lands, such as the Big Pine well field. Use of these water-management techniques would provide some flexibility in management from one year to another, but would not solve the basic problem that increased ground-water pumpage causes decreases in evapotranspiration and in the biomass of native vegetation. Furthermore, the highly transmissive and narrow aquifer system will transmit the effects of pumping to other more sensitive areas of the valley within a couple of years. Other possible changes in water management that might be useful in minimizing the short-term effects of pumping on native vegetation include sealing well perforations in the unconfined part of the aquifer system; rotating pumpage among well fields; continuing or renewing use of unlined surface-water features such as canals and ditches; developing recharge and extraction facilities in deeper volcanic deposits near Big Pine or in alluvial fan deposits along the east side of the valley; installing additional wells along the west side of the Owens Lake; and conjunctively using other ground-water basins between the Owens Valley and Los Angeles to store exported water for subsequent extraction and use during droughts.

Fish & Wildlife Groundwater Planning Considerations

California Department of Fish and Wildlife (CDFW) | June 6th, 2019

In 2014, California passed the Sustainable Groundwater Management Act (SGMA) (AB1739, SB 1168, SB 1319), authorizing local groundwater sustainability agencies (GSAs) to d

In 2014, California passed the Sustainable Groundwater Management Act (SGMA) (AB1739, SB 1168, SB 1319), authorizing local groundwater sustainability agencies (GSAs) to develop groundwater sustainability plans (GSPs) for a subset of California’s alluvial aquifers. To comply with SGMA, GSAs must achieve sustainable groundwater management, defined by SGMA as the avoidance of locally-defined undesirable results. To achieve sustainability, GSAs must develop and implement effective groundwater management plans that consider the interests of all beneficial uses and users of groundwater, including environmental users of groundwater. [Water Code § 10723.2.] In many groundwater basins, fish and wildlife that rely on groundwater are among these beneficial uses and users. Many sensitive species and habitats comprise groundwater dependent ecosystems (GDEs), which are natural communities that rely on groundwater to sustain all or a portion of their water needs. The unsustainable use of groundwater can impact the shallow aquifers and interconnected surface waters on which GDEs depend and may lead to adverse impacts on fish and wildlife. As trustee for California’s fish and wildlife resources, CDFW intends to engage as a stakeholder in groundwater planning processes (where resources are available) to represent the groundwater needs of GDEs and fish and wildlife beneficial uses and users of groundwater. The information provided here is intended to help local groundwater planners, groundwater planning proponents and consultants, and CDFW staff work together to consider the needs of fish and wildlife when developing groundwater management plans and implementing SGMA. The document includes three categories of groundwater planning considerations: Scientific Considerations Management Considerations; and Legal, Regulatory, and Policy Considerations. Links to additional guidance and considerations developed by CDFW and other organizations that address the impacts of groundwater pumping on GDEs and depletion of interconnected surface water can be found at the end of this document. Except to the extent that this document directly references existing statutory or regulatory requirements, use of these groundwater planning considerations is not mandated under law and should not be interpreted as a rule, regulation, order, or standard for local groundwater plans. Practical application of these considerations must be based on the best available information and groundwater basin-specific conditions.

Fish & Wildlife Groundwater Planning Considerations: Freshwater Wetlands

California Department of Fish and Wildlife (CDFW) | June 6th, 2019

 In 2014, California passed the Sustainable Groundwater Management Act (SGMA) (AB1739, SB 1168, SB 1319), authorizing local groundwater sustainability agencies to develo

 In 2014, California passed the Sustainable Groundwater Management Act (SGMA) (AB1739, SB 1168, SB 1319), authorizing local groundwater sustainability agencies to develop groundwater sustainably plans for a subset of California’s alluvial aquifers. This document provides considerations to assist local groundwater sustainability agencies in avoiding or minimizing adverse impacts to freshwater wetland beneficial uses and users of groundwater in local groundwater management planning and implementation. The information provided is intended to help local groundwater planners, groundwater planning proponents and consultants, and California Department of Fish and Wildlife (CDFW) staff work together to protect wetlands as a public trust resource. 

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

The 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 Dependent Ecosystems under the Sustainable Groundwater Management Act

The Nature Conservancy | February 1st, 2018

The Sustainable Groundwater Management Act (SGMA) of 2014 is landmark legislation in California that empowers local agencies, known as groundwater sustainability agencies

The Sustainable Groundwater Management Act (SGMA) of 2014 is landmark legislation in California that empowers local agencies, known as groundwater sustainability agencies (GSAs), to sustainably manage groundwater resources for current and future social, economic, and environmental benefits. In addition to balancing these multiple benefits, SGMA includes specific requirements to identify and consider impacts to groundwater dependent ecosystems (GDEs). Recognizing data and resource limitations, The Nature Conservancy developed this guidance document based on best available science to help agencies, consultants, and stakeholders efficiently incorporate GDEs into groundwater sustainability plans (GSPs). The Nature Conservancy’s tools and resources are intended to reduce costs, shorten timelines, and increase benefits for both people and nature.