Sustainable Groundwater Management Act Research Articles

Groundwater Sustainability and Land Subsidence in California’s Central Valley

The Central Valley of California is one of the most prolific agricultural regions in the world. Agriculture is reliant on the conjunctive use of surface-water and groundwater. The lack of available surface-water and land-use changes have led to pumping-induced groundwater-level and storage declines, land subsidence, changes to streamflow and the environment, and the degradation of water quality. As a result, in part, the Sustainable Groundwater Management Act (SGMA) was developed. An examination of the components of SGMA and contextualizing regional model applications within the SGMA framework was undertaken to better understand and quantify many of the components of SGMA. Specifically, the U.S. Geological Survey (USGS) updated the Central Valley Hydrologic Model (CVHM) to assess hydrologic system responses to climatic variation, surface-water availability, land-use changes, and groundwater pumping. MODFLOW-OWHM has been enhanced to simulate the timing of land subsidence and attribute its inelastic and elastic portions. In addition to extending CVHM through 2019, the new version, CVHM2, includes several enhancements as follows: managed aquifer recharge (MAR), pumping with multi-aquifer wells, inflows from ungauged watersheds, and more detailed water-balance subregions, streamflow network, diversions, tile drains, land use, aquifer properties, and groundwater level and land subsidence observations. Combined with historical approximations, CVHM2 estimates approximately 158 km3 of storage loss in the Central Valley from pre-development to 2019. About 15% of the total storage loss is permanent loss of storage from subsidence that has caused damage to infrastructure. Climate extremes will likely complicate the efforts of water managers to store more water in the ground. CVHM2 can provide data in the form of aggregated input datasets, simulate climatic variations and changes, land-use changes or water management scenarios, and resulting changes in groundwater levels, storage, and land subsidence to assist decision-makers in the conjunctive management of water supplies.

The relationship between how agencies work together and coordinated outcomes: a configurational analysis

Abstract Coordination mandates are used to steer collective action between local government agencies. When higher levels of government allow agencies to choose how to work together, the organizational forms and institutional arrangements they adopt likely influences their ability to achieve mandated coordinated outcomes. How group-level interactions influence achievement of coordinated outcomes is not well understood. California’s Sustainable Groundwater Management Act (SGMA) provides opportunity to shed light on this topic. SGMA is a state-legislative mandate that requires local agencies who share groundwater basins to undertake groundwater sustainability planning. The mandate affords agencies leeway in deciding how they engage with one another so long as they meet multiple requirements for coordinated outcomes. Drawing on institutional theories of collective action and ethnographic data collected from 2018 to 2022, we employ multi-value Qualitative Comparative Analysis to examine how configurations of organizational forms and institutional arrangements adopted by agencies in eighteen groundwater basins influenced their achievement of coordinated outcomes. Our findings highlight the importance of adopting collaborative institutional arrangements. Yet, the specific configuration of collaborative institutional arrangements varies depending on the type of coordinated outcomes agencies are mandated to achieve. These findings point to the need for mandates to require adoption of collaborative institutional arrangements, the specific configurations of which will be dictated by the requirements of the mandate.

Thousands of domestic and public supply wells face failure despite groundwater sustainability reform in California’s Central Valley

Across the world, declining groundwater levels cause wells to run dry, increase water and food insecurity, and often acutely impact groundwater-dependent communities. Despite the ubiquity and severity of these impacts, groundwater research has primarily focused on economic policy instruments for sustainable management or the quantification of groundwater depletion, rather than assessing the impacts of management decisions. In particular, how definitions of groundwater sustainability shape the fate of resource users remains unexplored. Here, we examine one of the world’s largest-scale environmental sustainability reforms, the California Sustainable Groundwater Management Act (SGMA), and estimate the impact of sustainability definitions proposed in groundwater sustainability plans (GSPs) on well failure. We show that locally-proposed sustainability criteria are consistent with business as usual groundwater level decline, and if reached, could impact over 9000 domestic wells and around 1000 public supply wells. These findings highlight the necessity of careful and critical evaluation of locally-developed sustainability definitions and their implementation to prevent detrimental impacts, such as threats to household and municipal water supply.

How water features: negotiating and reassembling the sociomaterial politics of central Californian groundwater

ABSTRACT This article explores responses to the California Sustainable Groundwater Management Act (SGMA) to challenge post-political and governmentality perspectives on environmental management. I chart how SGMA reconfigured sociomaterial orderings in the Central Valley region, enacting a liminal moment for groundwater culture, between a historically entrenched libertarianism and an emergent communitarianism. Local organizations functioned as boundary organizations, re-shaping groundwater assemblages by negotiating boundaries between authority and marginalized communities. I argue that the structures and institutions typically critiqued in post-political and de-political theorising can be more fruitfully conceptualized as part of sociomaterial assemblages within which there lies potential for transformative groundwater politics.

From fallow ground to common ground: Perspectives on future land uses in the San Joaquin valley under sustainable groundwater management

Agriculture dominates California's San Joaquin Valley with over five million acres of farmland produces 400 different commodities ranging from nuts, tree fruits, vines, and row crops. During dry years agricultural production in the San Joaquin Valley uses about 53% of total applied water in the state. Implementation of California's Sustainable Groundwater Management Act (SGMA) will restrict groundwater pumping, likely reducing irrigated agricultural land use resulting in conversion to alternative land uses. To promote collaborative and inclusive efforts to repurpose agricultural land, California's legislature established a funding program administered by the Department of Conservation, the Multibenefit Land Repurposing Program (MLRP), in 2021. To ensure that land repurposing plans under the MLRP and SGMA represent San Joaquin Valley community needs this paper examines public perceptions of future land uses under SGMA through a phone survey. Respondents (n = 197) were recruited through a stratified random sample of mobile numbers registered within communities in the San Joaquin Valley classified as disadvantaged communities (DACs) (n = 32). Our results show that most respondents were somewhat (33%) or not at all (54%) familiar with SGMA, highlighting the need for outreach efforts to overcome barriers to representation, translation, and education about future water and land use decisions. Survey respondents identified secure water supplies (e.g., groundwater recharge) (35%) and less-water intensive agriculture (27%) as their top land use priorities to address groundwater overdraft under SGMA, indicating that the status quo for land use is preferred to alternative land uses. Preference for maintaining agriculture as primary land use (27%), we correlated with agricultural identity and lack of interest in community or global benefits such as schools and climate change mitigation. The findings from this study underscore the local variability in land use values and the importance to engaging local communities in land use decision-making, especially as they relate to changing current practices toward a more climate-resilient but agriculturally productive future with less land and less water.

Development and Validation of an In Situ Groundwater Abstraction Sensor Network, Hydrologic Statistical Model, and Blockchain Trading Platform: A Demonstration in Solano County, California.

Megadrought in the western United States is jeopardizing water security. Groundwater regulations, such as California's Sustainable Groundwater Management Act (SGMA), aim to preserve groundwater resources in overdrafted basins. Water agencies must establish sufficient monitoring systems to measure local groundwater abstraction and devise plans to moderate groundwater use. However, few technologies are available to monitor and regulate groundwater abstraction spatially and temporally. In this study, we deployed satellite-connected electrical current sensors on 11 agricultural groundwater pumps in Solano County, California over 2019-2022. A high correlation (R 2 = 0.706) was found between the in situ sensors and in-line flow meters. We then combine in situ sensor data with a land surface model to develop a multiple linear regression model of groundwater abstraction and groundwater level. Using a 10-fold cross-validation, it is found that our predictive groundwater abstraction model has approximately a 3.5% bias and a mean absolute error of 1.21 acre-feet, while our predictive groundwater level model has approximately 4.2% bias and about 5.9 acre-feet mean absolute error. Finally, we integrated these data with a blockchain-based groundwater credit trading platform to demonstrate how such a tool could be used for SGMA compliance.

Winter flooding recharges groundwater in almond orchards with limited effects on root dynamics and yield

California signed the Sustainable Groundwater Management Act (SGMA) into law in 2014. SGMA requires groundwater-dependent regions to halt overdraft and develop plans to reach an annual balance of pumping and recharge. Groundwater aquifers can be recharged by flooding agricultural fields when fallow, but this has not been an option for perennial crops such as fruit and nut trees. While flooding these crops might be possible during the dormant season, it is not known what impact flooding might have on tree-root systems, health and yield. We followed root production, tree water status and yield in two almond orchards in Northern California for 2 years to test the impact of applying captured winter water runoff for groundwater recharge purposes on tree performance. Results showed that more than 90% of the water applied to sandy soil and 80% of the water applied to loamy soil percolated past the root zones, with no measured adverse effects on tree water status, canopy development or yield. Groundwater recharge did not negatively affect new root production and tended to extend root lifespan. Based upon these data, applying additional water in late December and January is not likely to have negative impacts on almond orchards in moderately drained to well-drained soils.

Linkages between land-use change and groundwater management foster long-term resilience of water supply in California

Study RegionWe created a 270-m coupled model of land-use and groundwater conditions, LUCAS-W[ater], for California’s Central Coast. This groundwater-dependent region is undergoing a dramatic reorganization of groundwater management under California’s 2014 Sustainable Groundwater Management Act (SGMA). Study FocusUnderstanding land-use and land-cover change supports long-term sustainable water management. Anthropogenic water demand has depleted groundwater aquifers worldwide, while future water shortages will likely affect land-use change, creating system feedbacks. Our novel participatory approach fused changes in land-use and associated water use from county-scale data to local water agencies’ estimates of total sustainable supply, scaling up local hydro-geologic knowledge from heterogeneous aquifers and diverse management approaches to a regional level. We assessed five stakeholder-driven scenarios with the same historic rates of urban and agricultural land-use change, but different water and land-use management, analyzing how management strategies altered both the spatial pattern of development and subsequent water sustainability from 2001 to 2061. New Hydrological Insights for the RegionTransformative strategies using demand-side interventions that coupled water availability to land-use more effectively achieved long-term sustainability than adaptive strategies using supply-side interventions to increase water supplies. Limiting water withdrawals within SGMA regulated basins resulted in leakage of development into unregulated basins, increasing groundwater pumping there. Protecting ecosystems, farmlands, and recharge areas from development reduced leakage into undeveloped basins without negatively affecting water sustainability.

When Agency Priorities Matter: Risk Aversion for Autonomy and Turf Protection in Mandated Collaboration

AbstractMost studies in collaborative governance examine system-level or agency-level drivers of the horizontal dimension of collaboration, that is, the specific forms of collaboration among an existing set of actors. Few have examined the vertical dimension, that is, what actors are involved and the scope of collaboration. This study examines the latter issue by studying the implementation of the California Sustainable Groundwater Management Act (SGMA), passed in 2014, mandating collaboration among local agencies. We theorize that when their core mission and key constituencies’ interests are at stake under a mandate, agencies focus on protecting organizational autonomy and bureaucratic turf in determining the scope of the collaborative arrangement, rendering other usual collaboration drivers less relevant. With data derived from administrative records and a statewide survey of local groundwater managers, we test this argument using several analytical methods, including probit regression, two-step estimation of an ordered probit selection model, and a linear probability model. The analyses consistently show that agencies are more likely to commit to regionally integrated collaboration that matches the scale of a groundwater basin if (1) their mission addresses a broader issue focus (lower issue specificity), (2) their core stakeholder groups have less concentrated interests, and (3) the organizational culture is less rigid and risk averse. In contrast, other well-known horizontal collaboration drivers do not matter. By unpacking the agency-specific sources of turf and reputation protection, this study contributes to an understanding of collaboration risk management.

Evaluating California’s Sustainable Groundwater Management Act: The First Five Years of Governance and Planning

AbstractCalifornia’s landmark 2014 Sustainable Groundwater Management Act (SGMA) requires local officials to form new Groundwater Sustainability Agencies (GSAs) and to write new groundwater sustainability plans capable of eliminating overdraft within 20 years. To assess progress achieved during SGMA’s first five years of implementation, we surveyed officials who manage or participate in GSA governance. The most common obstacles to GSA formation have involved horizontal and network governance issues such as too many diverse interests or lack of trust among stakeholders. The most common obstacles to groundwater planning include a lack of financial resources and the requirement to coordinate plans among GSAs in the same basin. Respondents usually report that their own GSA performs well on seven measures of good governance, such as representing all major stakeholders, granting members sufficient power, and generating trusted data for decision making. On the other hand, many GSA managers acknowledge that some types of stakeholders remain underrepresented in the governing structure despite SGMA’s mandate to “consider the interests of all beneficial uses and users of groundwater.” Overall, most respondents are optimistic that SGMA will enhance groundwater sustainability locally and statewide. If successfully implemented and fully funded, SGMA could become a model worldwide for sustainable resource governance that combines top‐down mandates and local incentives.

Innovations in Sustainable Groundwater and Salinity Management in California’s San Joaquin Valley

The Sustainable Groundwater Management Act (SGMA) of 2014 and the Central Valley Salinity Alternatives for Long-Term Sustainability (CVSALTS) initiative were conceived to reverse years of inaction on the over-pumping of groundwater and salination of rivers that both threaten agricultural sustainability in the State of California. These largely stakeholder-led, innovative policy actions were supported by modern tools of remote sensing and Geographic Information System technology that allowed stakeholders to make adjustments to existing resource management and jurisdictional boundaries to form policy-mandated Groundwater Sustainability Agencies (GSAs) and Salinity Management Areas (SMAs) to address future management responsibilities. Additional resources mobilized by the California Department of Water Resources (CDWR) and other water resource and water quality management agencies have been effective in encouraging the use of spreadsheet accounting and numerical simulation models to develop robust and coherent quantitative understanding of the current state and likely problems that will be encountered to achieve resource sustainability. This activity has revealed flaws and inconsistencies in the conceptual models underpinning this activity. Two case studies are described that illustrate the disparity in the challenges faced by GSAs in subregions charged with developing consensus-based Groundwater Sustainability Plans (GSPs). These case studies also illustrate the unique aspect of SGMA: that alongside mandates and guidelines being imposed statewide, local leadership and advocacy can play an important role in achieving long-term SGMA and CVSALTS goals.

Point- and reach-scale measurements are important for determining accurate seepage rates in controlled flow channels

A critical component of water-resources management in the irrigated agriculture landscape, particularly those landscapes dependent on groundwater availability, is determining groundwater recharge rates from streams and other channels. In California, flows in many such channels are “controlled” by upstream reservoir releases to meet downstream urban, irrigation and environmental water requirements. Seepage volumes from these channels and how they might vary during controlled release periods is a key component of meeting downstream riparian and groundwater-pumping needs. Understanding annual seepage from streamflow channels is also important in developing water budgets as part of the management of groundwater resources under the Sustainable Groundwater Management Act (SGMA) in California. However, direct measurements of channel seepage rates are infrequent or unavailable, and these rates, or associated volumes, are most often only estimated. Here we describe direct point- and reach-scale field measurements of channel seepage rates in Lower Putah Creek (Solano County) and in distribution lateral channels of the Oakdale Irrigation District on the east side of the San Joaquin Valley (San Joaquin and Stanislaus counties). We measured overall average seepage rates of about 2 feet (610 mm) per day at both locations and determined how these rates varied spatially and temporally during the summer when channel flows are controlled for downstream requirements.

Characterization of Groundwater Recharge and Flow in California's San Joaquin Valley From InSAR-Observed Surface Deformation.

Surface deformation in California's Central Valley (CV) has long been linked to changes in groundwater storage. Recent advances in remote sensing have enabled the mapping of CV deformation and associated changes in groundwater resources at increasingly higher spatiotemporal resolution. Here, we use interferometric synthetic aperture radar (InSAR) from the Sentinel‐1 missions, augmented by continuous Global Positioning System (cGPS) positioning, to characterize the surface deformation of the San Joaquin Valley (SJV, southern two‐thirds of the CV) for consecutive dry (2016) and wet (2017) water years. We separate trends and seasonal oscillations in deformation time series and interpret them in the context of surface and groundwater hydrology. We find that subsidence rates in 2016 (mean −42.0 mm/yr; peak −345 mm/yr) are twice that in 2017 (mean −20.4 mm/yr; peak −177 mm/yr), consistent with increased groundwater pumping in 2016 to offset the loss of surface‐water deliveries. Locations of greatest subsidence migrated outwards from the valley axis in the wetter 2017 water year, possibly reflecting a surplus of surface‐water supplies in the lowest portions of the SJV. Patterns in the amplitude of seasonal deformation and the timing of peak seasonal uplift reveal entry points and potential pathways for groundwater recharge into the SJV and subsequent groundwater flow within the aquifer. This study provides novel insight into the SJV aquifer system that can be used to constrain groundwater flow and subsidence models, which has relevance to groundwater management in the context of California's 2014 Sustainable Groundwater Management Act (SGMA).

Surface Reservoir Reoperation for Managed Aquifer Recharge: Folsom Reservoir System

As is much of the world, California increasingly is challenged by water scarcity. A recent multiyear drought depleted surface reservoir and groundwater storage in many places of the state. The Sustainable Groundwater Management Act (SGMA), passed in 2014, promises sustainable groundwater management in California and suggests managed aquifer recharge (MAR) as one of the key practices to eliminate groundwater overdraft by groundwater sustainability agencies. Questions remain, however, about the amount of water available for MAR. Conjunctive management provides the opportunity to modify reservoir operations and enhance recharge long before any drought occurs. However, the amount by which reoperation of surface reservoirs can increase the available water for MAR has not been thoroughly investigated. Folsom reservoir is operated to meet a variety of objectives, including flood control, water supply, hydropower, and environmental flow. The inclusion of water discharge for groundwater recharge adds another objective for the operation of the reservoir and complicates the decision-making. Various management strategies were developed and applied to evaluate performance of the system during a historical period, and a new objective was added to maximize the available water for recharge from Folsom reservoir. Although the reoperation strategy offers additional storage in the system and increases the expected value of recharge from 280 to 430 million cubic meter (mcm) per year, trade-offs between different objectives showed that new operating rules perform quite satisfactorily, with nonsignificant deficits and violations of old objectives.

Groundwater and Drought Resilience in the SGMA Era

Projections are that climate change will increase drought risk and intensity globally. Groundwater is critical during drought, but worldwide aquifers are experiencing unrecoverable groundwater declines. California is ideal to explore strategies for managing groundwater for drought resilience. Many areas rely on groundwater, yet multiple basins are in overdraft. Management was historically centered in local water districts, but in 2014, the state passed the Sustainable Groundwater Management Act (SGMA) establishing mandatory groundwater management rules. This paper discusses strategies used prior to and post SGMA to sustainably manage groundwater for drought resilience, and evaluates the effectiveness of these strategies. It highlights two recent approaches that can increase drought resilience under climate change: flood-MAR – using flood flows for both recharge and irrigation; and the development of locally sited groundwater drought reserves that can serve as a buffer during extreme droughts.

Quantifying uncertainty in groundwater depth from sparse well data in the California Central Valley

Groundwater is a critical freshwater resource for irrigation in the California Central Valley, particularly in times of drought. Groundwater depth has dropped rapidly in California’s overdrafted basins, but irregular monitoring across space and time limits the accuracy of the groundwater depth projections in the Groundwater Sustainability Plans required by the California Sustainable Groundwater Management Act (SGMA). This work constructs a Bayesian hierarchical model for predicting groundwater depth from sparse monitoring data in three Central Valley counties. We apply this model to generate 300 m resolution monthly groundwater depth estimates for drought years 2013–2015, and compare our smoothed groundwater depth map to smoothed rasterized maps published by the CA Department of Water Resources. Finally, we quantify uncertainty in groundwater depth predictions that are made by imputing missing well data and interpolating predictions across the study domain, which is helpful in directing future sampling efforts towards areas with high uncertainty. The BHM model accurately captures the spatiotemporal pattern in groundwater depth, as evidenced by 94.54% of withheld test samples’ true depth being covered by the 95% prediction interval drawn from the BHM posterior distribution. The model converged despite a very sparse dataset, demonstrating broad applicability for evaluating changes in regional groundwater depth as required by SGMA. Depth prediction intervals can also help prioritize future groundwater depth sampling activity and increase the utility of groundwater depth maps in total storage predictions by enabling sensitivity analysis.

A glass half empty: Limited voices, limited groundwater security for California

Groundwater is a common pool resource that supports agriculture, human communities, and the environment. Public participation in common pool natural resources management can be affected by media representation of stakeholders and perceptions of identity as a stakeholder. Newspaper media has an outsized influence on framing subject matter, expertise, organizations, and who should participate. Media shapes individual, local, and regional perspectives around resource management and defines potential solutions to natural resources management. This study analyzes media coverage about California's new Sustainable Groundwater Management Act (SGMA) to understand impacts on public participation in common pool natural resources management and to identify represented stakeholders and solutions involved in groundwater sustainability. A total of 365 newspaper articles were collected from California newspapers in three readership locations. We also searched for representation of SGMA in Spanish-language publications. Article characteristics were analyzed through qualitative content analysis and quantitative nonparametric analysis. Results indicate bias for featuring agricultural industry, politician, and water managers' voices. Solutions for managing water resources were focused on new supply, demand reduction and infrastructure investment, though novel solutions were also presented. Most newspaper articles included few stakeholders and solutions, illustrating isolated, short narratives about a common pool resource. The trends and gaps in representation in California media coverage may contribute to the public's low levels of engagement in groundwater planning.

What is Fair in Groundwater Allocation? Distributive and Procedural Fairness Perceptions of California’s Sustainable Groundwater Management Act

Fairness perceptions can contribute to trust or distrust in a policy process. Under California’s Sustainable Groundwater Management Act (SGMA) basins may limit groundwater extraction for users, including farmers. Using a 2017 survey of 137 farmers in Yolo County, we adapt a typology of fairness principles, previously applied to climate policy, to examine farmers’ fairness perceptions for groundwater allocation strategies and reconciliation options. Yolo farmers show clear preference for allocation by overlying land area and dispute reconciliation by the local Groundwater Sustainability Agency. Using ordered logit regression models, we find that positive procedural perceptions of SGMA predict both allocation and dispute resolution preferences. We find no evidence for self-interested bias in allocation preferences, but rather the contextual default for allocation (egalitarian) appears to drive current fairness perceptions. Insight into contextual norms and perceptions of the policy process can align allocation and dispute resolution decisions with stakeholder fairness assessments.

Detection and measurement of land subsidence and uplift using interferometric synthetic aperture radar, San Diego, California, USA, 2016–2018

Abstract. Land subsidence associated with groundwater-level declines is stipulated as an “undesirable effect” in California's Sustainable Groundwater Management Act (SGMA), and has been identified as a potential issue in San Diego, California, USA. The United States Geological Survey (USGS), the Sweetwater Authority, and the City of San Diego, undertook a cooperative study to better understand the hydromechanical response of the coastal aquifer system using Interferometric Synthetic Aperture Radar (InSAR) techniques. Three periods of interest were analyzed for this study that correspond to the periods before and after two substantial changes were made to the location and volume of pumpage: (1) April–August 2016 when groundwater levels and land surface elevation were relatively stable during normal pumping, (2) September 2016–May 2017 when groundwater levels recovered and the land surface uplifted during a period of substantially reduced pumping, (3) June 2017–October 2018 when groundwater levels declined and land subsidence occurred when pumpage resumed and expanded to new wells. Spatial and temporal characterization of the hydromechanical response to changes in pumpage is important for managing land subsidence. Further study using InSAR techniques, especially when combined with ground-based geodetic and monitoring-well networks, will provide water managers information to help effectively manage groundwater resources as stipulated in the SGMA.

Concurrent Governance Processes of California’s Sustainable Groundwater Management Act

California’s Sustainable Groundwater Management Act (SGMA) is a landmark policy that requires achievement of sustainability at the groundwater basin level. In this policy review and analysis, we describe the horizontal, vertical, and network governance processes occurring under SGMA and discuss how they interact with one another. In doing so, we review existing governance theories that can help to shed light on how each governance process may unfold. Depicting SGMA as a complex system of simultaneous and interacting governance processes provides a useful platform for future evaluations of SGMA successes and failures as well as for transferring lessons learned from California’s implementation of SGMA to groundwater governance in other locations.