https://orcid.org/0000-0003-3136-2576
Figures
Abstract
Societies globally are struggling to meet freshwater demands while agencies attempt to address water access inequities under a rapidly changing climate and growing population. An understanding of dynamic interactions between people and water, known as sociohydrology, regionally could provide approaches to addressing local water mismanagement and water access inequity. In semi-arid California, local water agencies, primarily agricultural irrigation districts, are at the intersection of rethinking approaches to balance freshwater demands. More than 150 years of complex water governance and management have defined San Joaquin Valley irrigation districts and the region’s water access inequities and sociohydrologic instability. Older irrigation districts have higher surface water allocations and less groundwater dependence. About 60% of irrigation districts with pre-1914 water rights have twice the crop water demand in surface water allocations. In contrast, 86% of irrigation districts depend on groundwater, of which 12% rely exclusively on groundwater to supply irrigation demands. This study found that disadvantaged communities within irrigation districts do not have increased water access or better environmental conditions than those outside irrigation district boundaries, which underscores the need for inclusive water management structures to address the multifaceted water and environmental inequities. Groundwater overdependence across irrigation districts shows that imbalanced surface water allocations and inflexible crops could imperil agriculture and impact agricultural disadvantaged communities, especially under California’s SGMA and prolonged drought events. It is imperative that underserved communities are prioritized communities in achieving equitable water rebalance in California in addition to developing and implementing essential infrastructure and policy changes.
Citation: Espinoza V, Viers JH (2024) The paradox of production: Surface water supply drives agricultural productivity but not prosperity in California’s San Joaquin Valley. PLOS Water 3(6): e0000192. https://doi.org/10.1371/journal.pwat.0000192
Editor: Majid Shafiee-Jood, University of Virginia, UNITED STATES
Received: May 11, 2023; Accepted: May 9, 2024; Published: June 13, 2024
Copyright: © 2024 Espinoza, Viers. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: Data is publicly available via Dryad: https://doi.org/10.5061/dryad.3xsj3txnw Code is available on Github: https://github.com/vicelab/irrigation_district_analysis.
Funding: VE was partially supported by USDA Agriculture and Food Research Initiative Competitive Grant no. 2021-69012-35916 from the USDA National Institute of Food and Agriculture, the AI Research Institutes program supported by NSF and USDA-NIFA under the AI Institute: Agricultural AI for Transforming Workforce and Decision Support (AgAID) award No. 2021-67021-35344, and 2021-2022 University of California President’s Dissertation Fellowship. The funders had no role in study design, data collection, and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
1. Introduction
The global water crisis is frequently framed in terms of water availability [1]. Yet, the challenges of water access inequality, often rooted in governance shortcomings, remain underemphasized [2]. Factors such as the growing human population and climate-related extreme events, including droughts, amplify the dependence on groundwater, especially for irrigated agriculture [3–6]. In arid and semi-arid regions, groundwater stands as a pivotal freshwater source, catering to the needs of over two billion people for both drinking water and irrigation [5, 7]. However, this heavy reliance has led to groundwater being extracted faster than it can naturally recharge [8]. As climate change impacts surface water sources, like altering precipitation patterns and reducing snowpack, the exploitation of groundwater is anticipated to rise, further exacerbated by population growth [9]. Globally, water management entities grapple with the consequences of past water resource management decisions and aging infrastructure [10]. These agencies face the daunting task of adapting to changing climate conditions and growing populations, often without the necessary tools or frameworks [11].
In this paper, we address the paradoxical sociohydrologic dynamics in California’s San Joaquin Valley, where abundant water resources drive agricultural productivity but fail to translate into equitable water access and prosperity for all communities. Specifically, the paper seeks to answer the following research questions: 1) How have historical water rights and governance structures contributed to current groundwater dependence in the region? 2) What are the socio-economic and environmental impacts of this groundwater dependence, particularly on disadvantaged communities? 3) How does the Sustainable Groundwater Management Act (SGMA) interact with existing water management practices, and what challenges does it pose? 4) What strategies can be employed for more resilient and equitable water management in the face of climate change? Through the lens of sociohydrology, we explore the complex interplay between water resources, social inequities, and governance in the San Joaquin Valley with the intent to inform a more sustainable, equitable, and secure water future. This work highlights the need to consider social integration in water management along with a combination of infrastructure and policy changes to balance surface water and groundwater resources in the state.
1.1 Sociohydrological context
Recent advances in water governance emphasize the role of sociohydrology in addressing both climate change adaptation and the equitable distribution of water resources [12, 13]. The overarching challenge in water lies in reconciling maximizing the utility of water with sustainable use of shared natural resources, as this often culminates in overexploitation [14]. Sociohydrology aims to understand the interplay of human values and norms and their influence on water resource management. It also examines how water resource management decisions can impact societal well-being across spatio-temporal scales. The ultimate need for a more water-secure future is to devise water resource management strategies that consider the effects of human behavior on hydrological systems. Embedded within sociohydrological systems, various governance models exist. While some of these models may appear contradictory, they are deeply rooted in historical contexts and are particularly evident in perceptions of water as property [15–17]. Franz von Benda-Beckmann, a legal scholar, explored the intricate connections between water resources, legal frameworks, and human behavior. He concluded that local history and cultural norms significantly influence both water rights and the interpretation of water laws [18]. Building on this, von Benda-Beckmann linked human behavior to resource management through water rights, irrigation practices, and human decision-making and how we collectively shape sociohydrological governance systems [16]. By extension, humans establish, organize, and enforce rules, responsibilities, and rights to govern water use, often to facilitate economic and social investments in water infrastructure like irrigation and conveyance [19]. Consequently, the control of water is tantamount to the control of society, a concept that has remained constant throughout human history [15, 20]. Local water governance structures in California have significantly influenced the intricate connections between irrigation district supplies, shaping rules, policies, and management to facilitate investments in water infrastructure and ultimately perpetuating a historical and current scenario marked by the disproportionate overallocation of surface water, water access inequity, and an agricultural poverty paradox across DACs in the region, reflecting regional values and norms rooted in an agriculturally-dominant culture (Fig 1). Aligning water governance structures with societal values and community priorities is essential for achieving sustainable well-being outcomes in a dominantly agricultural region, and ensuring the responsible management of water resources, especially under SGMA. In regions with complex sociohydrologic histories, a nuanced evaluation of these sociohydrologic relationships is essential for effectively addressing modern resource conflicts now exacerbated by climate change [21].
(2014) applied to the San Joaquin Valley’s irrigation district water supply, agricultural demand, and societal priorities.
1.2 California’s contemporary sociohydrological context
California is an example of the global water crisis and the study of sociohydrology (sensu [12])—an increasing human population, competing demands for surface water, complex surface water rights, groundwater overdraft, water access inequity, poverty, food insecurity, and climate change. Despite California’s status as the largest U.S. state by population and its annual agricultural and livestock revenue of USD 50.1 billion [22], it’s not as water-rich as one might assume. However, in reality this water-thirsty state is an altered desert. California’s water conveyance system of 1,500 reservoirs, 1,135 km of the State Water Project, 644 km of the Central Valley Project [23]—nourishes the state’s agricultural economy and redistributes water to the water-scarce south, but this transfer of resources is facilitated by an arcane and contradictory patchwork of water rights and regulatory jurisdictions [24, 25]. Despite the past success of extensive water distribution networks that boosted urban and agricultural prosperity, there remains a persistent problem of unequal access to water due to current management practices. Moreover, the western United States is now approaching its water capacity limit for sustaining cities, agriculture, and ecosystems [26]. While agriculture in California uses 40% of annual surface water runoff compared to 10% used by cities [27], about one million people in California live in underserved, unincorporated communities without access to safe, clean drinking water [28]. Disadvantaged communities (DACs) in the San Joaquin Valley represent the region’s poverty paradox—communities surrounded by the productive agricultural fields that drive local economies, and yet are disproportionately burdened with poor air and water quality, poverty, food insecurity, and political underrepresentation [28–32]. California’s conflicting water demands between agricultural, environmental, and urban centers often stem from overly optimistic estimates of available surface water [26]. Thus, it is not surprising that California’s surface water has been claimed several times more than the amount available [15, 24] (Grantham & Viers, 2014; Hundley, 2002) and has been the focus of many popular recitations [33–35]. In California, the pursuit of climate resilience and fair water access hinges on the intersection of social integration, infrastructure development, and policy constraints, with a primary focus on the Sustainable Groundwater Management Act (SGMA). Prior to SGMA, groundwater in the state was inadequately monitored and regulated, resulting in a massive annual overdraft of 1.7 billion cubic meters (m3) [36]. SGMA, enacted in 2014, aims to rectify this by balancing surface water and groundwater use, targeting sustainability by 2040. This transformative legislation empowers local water agencies, including irrigation and municipal districts, organized into Groundwater Sustainability Agencies (GSAs), to spearhead the effort [9]. Beyond hydrological aspects, GSAs must actively involve communities and address their diverse needs, ensuring equitable access and resilience. Some of the suggested solutions to addressing groundwater overdraft as per SGMA, include increased infrastructure, water trading, strategic multibenefit land repurposing, and changes in policy [37]. It is important to note that achieving sustainable water management requires a multifaceted approach that combines various strategies while prioritizing communities, as no single solution can comprehensively address water issues.
1.3 California’s historical sociohydrological context
Water law and infrastructure development in California was an outcome of gold mining operations from the mid-1800s and formed a foundation for urban and agricultural prosperity. The late 1800s was formative for this economic growth as water rights were formalized, and the land was converted to agriculture. Water use during this period favored wealthy landowners, and riparian surface water rights (i.e., water rights associated with land adjacent to water body) were prioritized over appropriative water rights (i.e., water rights approved for water diversion for beneficial uses) [38]. The Wright Act of 1887 was passed to break the monopolization of the land and water spell by forming irrigation districts. Under this act, residents and farmers formed irrigation districts to represent the best interests of family farms and keep water rights in the irrigation district instead of private corporations or individuals [15]. The early formation of irrigation districts in 1887 also catalyzed the creation and transformation of agricultural communities in California, especially the San Joaquin Valley, by governing water resources in the interest of local water users [39, 40].
In California, water rights allocations with the most water by volume are allocated to public entities (e.g., water agencies) (78%), and agriculture has the highest count of designated water rights (70%) [24]. For irrigation districts, the date of formation is critical in determining the type of surface water right (pre-1914 or post-1914 appropriative rights), which dictates differences in management regulations and priorities. The lack of a surface water rights permitting system before 1914 allowed water users to claim a surface water right to be used for beneficial and reasonable use without the approval of a governing agency. When the Water Commission Act of 1914 was established to regulate the surface water rights permitting system, claims prior to 1914 were grandfathered into the water rights system as existing and senior. These senior pre-1914 water rights are given allocation priority, even in times of water scarcity, over post-1914 or junior water rights [41]. Irrigation districts and water users that do not receive surface water allocations, either due to junior or non-existent surface water rights, turn to groundwater to supply irrigation demands [42]. While all rights holders, riparian and appropriated, may get their share of surface water supplies during wet years, California’s frequent droughts create access disparities and generate conflicts among water users. In September of 2021, climate change amplified drought conditions led to the curtailment of water rights diversions for all pre-1914 and post-1914 water rights holders in the Sacramento-San Joaquin watersheds [43]. The Sacramento-San Joaquin watersheds provide surface water for 25 million Californian’s drinking water supply and irrigation for more than three million hectares of agricultural land.
1.4 Applying sociohydrology to secure a climate-resilient water future
California’s San Joaquin Valley is home to the state’s most critically overdrafted groundwater basins [27]. Consequently, the local water districts in this region serve as a needed case study for understanding sociohydrology—the interplay between water resources, human behavior, and governance. In this paper, we aim to inform our understanding of these dynamics by employing geospatial analysis to identify and assess the sociohydrologic vulnerabilities of irrigation districts in the San Joaquin Valley, which serves as the agricultural backbone of the state (Fig 2). Our analysis considers a range of interconnected factors, such as geographical location, formation date, and surface water rights (see S2 Table for a complete list of variables). This sociohydrologic approach allows us to assess two critical dimensions: socioeconomic equity and water reliability, both of which are paramount for climate change adaptation. This paper shows that certain irrigation districts are more vulnerable than others when it comes to their water supply and demand imbalance. We further employ cluster analysis to identify similarities and differences among irrigation districts, thereby providing insights into how SGMA may impact Disadvantaged Communities (DACs). Our focus on DACs within the boundaries of irrigation districts allows us to highlight the ’poverty paradox’ and the environmental inequities that persist in these communities. By doing so, we aim to contribute to the development of more equitable and climate-resilient water management strategies for California.
The state boundary was obtained from U.S. Census Bureau: https://catalog.data.gov/dataset/tiger-line-shapefile-2019-state-california-current-county-subdivision-state-based. The administrative boundaries were obtained from https://hub.arcgis.com/datasets/CALFIRE-Forestry::california-counties/about. This map was generated in ESRI ArcGIS Pro.
2. Materials and methods
2.1 Data availability & software
This study brings together detailed data from different local and state sources about irrigation districts. It uses this data to figure out the factors (e.g., the district’s history, politics, environment, and cultural characteristics) that influence the shortage of surface water and the dependence on groundwater in this agricultural area. S1 Table lists datasets and sources. S2 Table documents the variables calculated from the datasets highlighted in S1 Table. The major variables used in this analysis show an irrigation district’s history (i.e., age, dedicated water amount), surface water allocation and delivery, and crop composition within the district’s boundaries (e.g., total crop fraction, perennial crop fraction, annual crop fraction, and revenue). Additional data tables are published in Dryad (doi:10.5061/dryad.3xsj3txnw): Table 7 the variable values per irrigation district (freshwater variable normalized values reported). Table 8 includes the surface water allocation amounts for irrigation districts in this study and the source of information. Table 9 specifies the Land IQ crop types that make up the annual, perennial, and irrigated forage categories. Table 10 lists the crop revenue values and the associated crop type used in the analysis for irrigation districts within the eight San Joaquin Valley counties. The 2016 county crop report for each county is used to derive crop revenue values. The code used to generate the era analysis figure (Fig 3B) and irrigation district clusters (data for Fig 5) of the manuscript are published in GitHub (https://github.com/vicelab/irrigation_district_analysis). The primary software used to facilitate this analysis is ESRI ArcPro GIS [44] and R software [45].
a) Timeline of major California water development events from 1885 to 2020 per era (intervals in blue) to compare with b) irrigation district surface water allocation (purple) and average surface delivered from 2001–2015 (light blue) per era. Eras are based on Hanak et al. (2011).
2.2 Irrigation district boundaries
The most up-to-date irrigation district boundaries were obtained directly from the Local Agency Formation Commission (LAFCO) for seven counties in the San Joaquin Valley—San Joaquin, Stanislaus, Merced, Fresno, Madera, Tulare, and Kern. Kings County LAFCO could not provide updated boundaries, and the Department of Water Resources 2015 water agency boundaries were used for irrigation districts in this county. This study focuses solely on water agencies in the San Joaquin Valley floor (Fig 2, shaded grey) that distribute water for irrigation and exclude water conservation, domestic, and municipal water agencies. The irrigation district boundaries from these various sources were combined to create a single geospatial data file of irrigation districts in the San Joaquin Valley using ArcGIS software.
Era analysis.
Statistical analysis of the variables in S2 Table is done for irrigation districts within four major historical eras to shed light on how key water management events may have shaped irrigation districts over their formation. Irrigation district formation dates were categorized into major water management historical eras for infrastructure investments and economic development as outlined by [23]. The four major eras considered are the Era of Local Organization (1887–1913), Hydraulic Era (1914–1968), Era of Conflict (1969–2000), and Era of Reconciliation (2001–2020), mainly following [23].
2.3 Groundwater reliance calculation
Groundwater use in the San Joaquin Valley has been measured by irrigation districts and estimates have relied mostly on crop use estimated modeling studies for decades [7]. Hence, resolving disaggregated data and understanding of groundwater use across the region will be improved through the implementation of SGMA. Key datasets used to quantify the estimates of groundwater reliance per irrigation district in this study were Land IQ 2016 for California [46], electronic Water Rights Information Management System (eWRIMS) [41], U.S. Bureau of Reclamation agricultural contractors list, and a gridded-based water balance model called Water Footprint Analysis in R (WAFR) [47] that uses crop coefficients to calculate crop water requirements. The Land IQ 2016 dataset includes primary agricultural land use, wetlands, and urban boundaries for 58 counties in California derived for 2016 commissioned by the California Department of Water Resources. This study uses only agricultural land use classifications from the Land IQ 2016 dataset to calculate crop composition within irrigation district boundaries. Crop composition within irrigation districts also served as an input to the WAFR model to calculate crop water requirements for each district. Surface water allocation amounts were obtained from various sources—including eWRIMS, USBR agricultural contract amount lists and reports, Groundwater Sustainability Plans (GSP), Agricultural Water Management Plans (AWMP), and irrigation district web pages. Surface water delivery averages from 2001–2015 were obtained from [48] except for Banta Carbona Irrigation Districts, Byron-Bethany Irrigation District, and South San Joaquin Irrigation District. Average 2008–2019 surface water deliveries 2008–2019 for Banta-Carbona and Byron-Bethany irrigation districts were obtained from Tracy Subbasin GSP and South San Joaquin Irrigation District 2005–2019 average surface water deliveries were obtained from their 2020 AWMP.
The water budget equation (Eq 1) is used to derive estimates of groundwater reliance per irrigation district, meaning the amount of groundwater needed to make up for irrigation demand unmet by surface water, defined as:
(Eq 1)
Where ΔS is the change in water storage, P is precipitation, QGW is groundwater outflow, QSW is surface water runoff, and ET is evapotranspiration. For this project, a series of assumptions were made to quantify the reliance on groundwater for each irrigation district in the San Joaquin Valley using the water budget equation, these are:
- Precipitation, P, varies by irrigation district. Precipitation observations from the Parameter-elevation Regressions on Independent Slopes Model (PRISM) were used in the WAFR model to obtain the proportion of crop water requirements for irrigation districts. For more information on the data processing and WAFR model, refer to [47].
- QSW varies across irrigation districts, and values are based on surface water allocations determined by each irrigation district’s surface water right amount. This study assumes that irrigation districts have 100% allocation of their claimed water rights to meet irrigation demands (i.e., crop water requirements) to simulate a districts groundwater dependence and crop water demand during drought with full surface water capacity. Refer to S1 Table for more details on surface water allocation sources.
- Given that most groundwater basins in the San Joaquin Valley have been designated as critically overdrafted by the Department of Water Resources, the likelihood is that the volume of groundwater outflow, QGW is sufficiently substantial and included in the water budget is speculative. Although shallow groundwater drainage and water quality is a management concern, there has been a decline over time and limited discharge and water quality in delta. Therefore, the total volume of water from lateral exchange is not substantial in volume, but it is recognized that it could affect water quality [49].
- Crop water requirements (CWR) were calculated by accumulating daily crop evapotranspiration demand during the growing season within a given location and using a crop coefficient of evapotranspiration, ETc. For more information on the data processing and WAFR model, refer to [47].
This analysis quantifies irrigation district groundwater runoff, QGW, based on surface water allocation amounts (Eq 2) and average surface water delivery for irrigation districts (Eq 3).
SWallocation is an irrigation district’s surface water allocation, SWdelivery is an irrigation district’s surface water delivery, and CWR is an irrigation district’s crop water requirement. If Eqs 2 or 3 results in surface water surplus, SWS, then it is assumed that an irrigation district is not reliant on groundwater to meet irrigation demands or CWR. Whereas, if Eqs 2 or 3 results in surface water deficit, SWD, it is assumed that an irrigation district does not have enough surface water allocations or average surface water deliveries to meet irrigation demands and relies on groundwater to meet CWR amounts. Irrigation districts with surface water delivery of “no record” are assumed to receive no surface water delivery to facilitate calculating the surface water delivery surplus/deficit.
2.4 Irrigation district and GDC disadvantaged community comparison
The CalEnviroScreen 4.0 dataset is obtained for the most recent environmental health hazard assessment (2018) from the California Office of Environmental Health Hazard Assessment (OEHHA) [50], and the most up to date (2018) DAC census places boundaries were obtained from the Department of Water Resources (DWR) DAC Mapping Tool [51]. The CalEnviroScreen 4.0 dataset provides several indicators that reflect environmental conditions or poverty vulnerability for populations at the census tract level. The DAC census place boundaries provide the area, name, and location of DACs in California, reduced to the San Joaquin Valley floor (Fig 2, shaded grey area) for this analysis. To assess environmental and poverty conditions in San Joaquin Valley’s DACs, we combined the CalEnviroScreen 4.0 dataset with DAC census place centroids using ESRI ArcPro software. We also used irrigation district boundaries to identify GDCs on the valley floor, which are areas not served by irrigation districts and are highly dependent on groundwater to meet domestic water needs. Descriptive statistics (e.g., mean, median) were used to compare the traits between DACS with GDCs and irrigation districts, and an unpaired two-sample Wilcoxon test comparing the mean of the variables between the two groups is used to derive the p-value (α = 0.05).
3. Results and discussion
3.1 Age driven water and land ownership wealth
California’s irrigation districts and their water governance culture are shaped by historical water development contexts, including policy actions, infrastructure developments, the human relationship with water, and the predominant agricultural land use (Fig 3). This study categorized districts into four primary eras of change to determine how age drives surface water allocation and priority, affecting groundwater reliance for most districts. California’s transformative water management eras of change, adopted from Hanak et al. [23], are the Era of Local Organization (1887–1913), Hydraulic Era (1914–1968), Era of Conflict (1969–2000), and Era of Reconciliation (2001-today). This study shows that age influences irrigation districts’ surface water allocations, deliveries, service area sizes, and crop composition. This study highlights a clear correlation between the age of irrigation districts and their affluence in terms of surface water availability and land use. This correlation reflects the evolving dynamics of water and land use in the state of California. Irrigation districts with ample water resources can maximize unused water through strategies like water trading, banking, land repurposing, wildlife-friendly recharge, and several other strategies. Conversely, water-scarce districts may need to combine these approaches to ensure future water security.
3.1.1. Age influences water access.
Older irrigation districts formed during the Era of Local Organization have more significant annual surface water allocation and deliveries (Fig 3) compared to younger districts. This is due to the surface water rights claimed during that era before the establishment of the permitting system under SWRCB. Some surface water allocations within the SWRCB’s Electronic Water Rights Information Management System (eWRIMS) database are considered “pending,” primarily for irrigation districts formed during the Hydraulic Era (1914–1968) and one irrigation district recently formed. Many of these "pending" water rights petitions were submitted between 2014 and 2017. This shows that irrigation districts were quick to adapt, either by preparing for the need for more surface water to comply with SGMA through groundwater recharge methods or by reducing their dependence on groundwater pumping for irrigation purposes. Another potential outcome of SGMA is the recent formation of new irrigation districts that fall under the Era of Reconciliation (2001–2020). Under SGMA, water governance uncertainty may have led agricultural landowners to form districts after SGMA was passed to maintain greater control of water and land use management planning and implementation to address groundwater overdraft. This evolving landscape in water management approaches shows the historical legacy that has led to a disproportionate distribution of water access across irrigation districts across the Valley. Highlighting the unsustainability of requesting more water, it’s crucial to note that the state has taken proactive steps to address this issue. While various methods exist for decreasing water demands [37], pursuing additional water sources is neither sustainable nor likely viable in the long run, especially in a future marked by droughts and water scarcity. The adaptation strategies adopted by irrigation districts with different historical water security backgrounds underscore the significance of reducing demand rather than increasing water supply. This approach aligns with new and current state programs like The Department of Conservation’s Multibenefit Land Repurposing Program and the Department of Water Resources’ LandFlex Program, which aim to reduce groundwater use through considerations of alternative land uses that provide multiple benefits to DACs and the environment.
3.1.2 Land taxation laws impact service areas.
The decrease in the size of irrigation districts as they get younger reflects how California’s land taxation laws influenced agricultural land ownership in the San Joaquin Valley–a change that occurred over time. In 1909 irrigation districts started taxing land values instead of land improvements for district purposes [40]. These tax changes led to the dissolution of many large ranches into smaller land tracts, ultimately bringing more diversity in crops and prosperity to the region. While older districts tend to have larger service areas and greater surface water availability on average, they are less productive in terms of agriculture, based on the fraction of land dedicated to crops, when compared to younger districts. Specifically, districts formed during the Era of Local Organization and the Hydraulic Era have larger service areas but allocate 69% and 67% of their land to crops, respectively, whereas smaller and younger districts formed during the Era of Conflict and Era of Reconciliation allocate 81% and 71% of their land to crops, respectively.
Older districts from the Era of Local Organization and Hydraulic Era devote a smaller fraction of their land to perennial crops (53% and 59%, respectively). This reflects the fact that landowners within these districts had better access to water supplies for irrigation, which allowed them to focus on water-intensive and profitable crops. This may be due to higher surface water rights allocations and access to water conveyance infrastructure, such as local canals and aqueducts, as well as the State Water Project (SWP) and the Central Valley Project (CVP). Some older districts may choose to sell surplus surface water allocations to other districts or allocate them for other beneficial uses. For example, the Modesto Irrigation District, formed in 1887 under the Wright Act, illustrates the flexibility and control that pre-1914 surface water rights holders had over their water resources. They can use their surplus water supplies to meet irrigation demands and comply with new laws, especially during droughts. Modesto Irrigation District has, at times, delivered surplus water supplies to actively farmed agricultural lands outside their service area but within their sphere of influence to help meet the requirements of SGMA. However, during the early implementation of SGMA and the 2012–2016 California drought, they shifted to securing surplus surface water contracts with the county to keep surplus water supplies within the county. In contrast, younger irrigation districts formed during the Era of Conflict and Era of Reconciliation allocate the highest fraction of their land to perennial crops (69% and 92%, respectively). Although perennial crops are typically water-intensive, many growers choose them because of their high revenue potential, which can help offset the higher surface water prices for districts without senior pre-1914 surface water rights.
3.2 Managing groundwater overdependence: SGMA and land-water solutions
Irrigation districts are increasingly relying on groundwater due to climate change, droughts, and unequal access to water resources (Fig 4A–4F). In fact, 60% of irrigation districts with pre-1914 water rights have double the crop water demand in surface water allocations. On the other hand, 86% of irrigation districts in the San Joaquin Valley rely on groundwater for agriculture, with 12% using groundwater exclusively. When we assess their dependence on groundwater based on their surface water allocations, districts with ample surface water rights don’t fall into the groundwater-reliant category (Fig 4A–4C). However, when we consider average surface water deliveries from 2001 to 2015, we see a 32% increase in the number of districts dependent on groundwater for crop irrigation (Fig 4E, 4F).
Irrigation district groundwater dependence (c) is predetermined by their surface water allocation (a) and irrigation water demand (b), but their realistic groundwater dependence(f) is defined by the average surface water delivery (d) and irrigation demand (e). Irrigation districts with surface water delivery of “no record” are assumed to receive no surface water delivery to facilitate calculating the surface water delivery surplus/deficit. Data sources are outlined in S2 Table. The irrigation district boundaries were obtained from each county Local Agency Formation Commission (LAFCO) and consolidated for this analysis and these maps. This map was generated in ESRI ArcGIS Pro.
Irrigation districts with higher crop water needs are mainly found on the eastern side of the San Joaquin Valley, where citrus production is most significant. Those with pre-1914 water rights have up to three times more surface water rights than needed for their crop irrigation, making them less reliant on groundwater compared to districts with junior water rights. Districts without or with minimal surface water allocations become highly dependent on groundwater during droughts, often receiving their surface water deliveries after senior districts. Regardless of their age or formation, all irrigation districts in the San Joaquin Valley are at risk of groundwater dependence in a changing climate. However, districts with higher surface water allocations are better prepared to cope with surface water shortages than those without allocations, especially under SGMA (Fig 4A–4F).
To meet SGMA targets by 2040, Groundwater Sustainability Agencies (GSAs) need a realistic approach to water management [48]. Many plans submitted in 2017 for critically overdrafted basins focused on supply expansion (e.g., recharge, conveyance, and recycled water), which may not be feasible given increasing water scarcity and severe droughts. Surface water scarcity is becoming more frequent, as seen in the 2014–2016 drought and the start of the 2021 drought. California’s water rights already account for more than eight times the state’s annual runoff [24]. During the 2012–2016 drought, high-value, water-intensive crops in the Central Valley didn’t suffer production or revenue losses because of groundwater use [36]. To address groundwater overdraft under SGMA and in a more water-scarce future, it might be necessary to take over 10% of agricultural land out of production, on top of currently unused land in the San Joaquin Valley. This could particularly impact disadvantaged communities within groundwater-dependent irrigation districts [27]. Meeting the water challenges ahead will require a multifaceted approach that combines various strategies for reducing groundwater and surface water usage, as outlined in [37]. Equally crucial is the integration of community needs into these future solutions, emphasizing proactive and equitable community engagement.
3.3 Agricultural poverty paradox: DACs in irrigation districts and groundwater-dependent communities
Inequities in water access persist across both irrigation districts and communities heavily reliant on groundwater supplies, known as Groundwater-Dependent Communities (GDCs). To further understand the dynamics of irrigation districts, their constituents, and the complexities of water accessibility, this paper compares DACs within irrigation district boundaries (n = 97), hereafter ID DACs, and DACs in GDCs (n = 56), hereafter GDCs. Table 1 summarizes the comparison statistics.
The p-value is derived using the unpaired two-sample Wilcoxon test.
ID DACs, on average, exhibit smaller populations than GDCs, with average population sizes of 9,899 and 20,515, respectively. The median household income is slightly lower for ID DACs compared to GDCs. Both types of DACs share similar poverty burden percentiles, hovering around 83%. Notably, ID DACs face a higher exposure to pollution burden, averaging 81%, in contrast to GDCs, which average 74%. Both ID DACs and GDCs experience high exposure to particulate matter 2.5 microns in size (PM2.5), as well as a substantial prevalence of asthma. Pesticide burden exposure is also higher in ID DACs compared to GDC-DACs. This may contribute to a similar proportion of drinking water issues in both ID DACs and GDC-DACs. Importantly, threats to groundwater quality are consistent between ID DACs and GDC-DACs.
On average, ID DACs face greater burdens related to poor air quality and pesticide exposure compared to GDCs. Both types of DACs encounter high levels of poverty, issues with access to safe drinking water, and significant socioeconomic and environmental challenges. In summary, this comparison reveals that DACs under the jurisdiction of local government, such as irrigation districts, do not have better socioeconomic and environmental conditions than those located within GDCs. This underscores how historical and cultural contexts specific to irrigation districts shape the sociohydrological dynamics of agricultural regions.
It is important to note that irrigation districts were originally established to safeguard and ensure water availability for agriculture in the San Joaquin Valley, with their primary focus not necessarily encompassing the governance of water and agricultural practices to ensure safe drinking water or air quality for communities. This study underscores how, historically and culturally, farmers established irrigation districts in the late 1880s to promote irrigation and water conveyance infrastructure, catalyzing the region’s transformation into the world’s multi-billion-dollar fruit basket. The socioeconomic comparison underscores that local water agencies in the San Joaquin Valley are ill-prepared to address water access disparities among DACs within their jurisdiction. Prior to SGMA, irrigation districts were not mandated to engage with DACs to understand and incorporate community concerns regarding water management. To make SGMA effective, locally representative, and equitable in water management, future policies and funding programs related to water and land use management must foster diverse partnerships and community engagement. Programs that require diverse partnerships and community engagement are already being implemented in the state (i.e., Multibenefit Land Repurposing Program), yet there will be a need for continued guidance on best practices and approaches to community engagement if irrigation districts and GSAs are to develop and implement solutions that are equitable and effective in addressing groundwater overdraft long-term.
3.4 Water governance diversity and its role in driving sociohydrologic vulnerability
Water scarcity and droughts affect irrigation districts regardless of their seniority. However, water governance structures are shaped by sociohydrologic and historical factors, reflecting the unique contexts of each district and their commitment to safeguarding surface water for agriculture. Distinctions among districts in their ability to withstand droughts are determined by their history, location, water rights, and irrigation demands. We identified five types of irrigation districts (Fig 5) based on their groundwater dependency, ranked from highest to lowest:
For a list of variables used for this analysis, refer to S2 Table. The irrigation district boundaries were obtained from each county Local Agency Formation Commission (LAFCO) and compiled for this analysis and this map. This map was generated in ESRI ArcGIS Pro.
Groundwater Dependent Vineyards (GDV).
These districts, mainly situated in the eastern San Joaquin Valley (Fig 5, brown), have a history spanning all formation eras. They rely heavily on groundwater due to minimal surface water deliveries (ranging from -5 to -15 ML/Ha). Approximately 43% of districts received no surface water between 2001–2015, and 48% had zero surface water allocations. To compensate for reduced groundwater use under SGMA and limited surface water claims, these districts have numerous pending surface water rights requests (ranging from 0.6 to 27 ML/Ha). Their demand for surface water is driven by high-value crops, primarily grapes (averaging 23% of crop area).
California Citrus Belt (CCB).
These districts, primarily located in the Central Eastern and Southern San Joaquin Valley (Fig 5, dark orange), mostly formed during the Hydraulic Era (82%). They have the highest proportion of perennial crops (average 92% of crop area) and revenue (USD 2,300 to 3,570), with citrus being the dominant perennial crop (averaging 44% of the crop area). While 91% have surface water allocations and 96% receive surface water deliveries, all are groundwater dependent. The surface water deficit/surplus varies (-11 to 4 ML/Ha). Vulnerability to groundwater overdependence in this group is attributed to high crop water requirements (~12 ML/Ha) and insufficient surface water deliveries (~5 ML/Ha). The CalEnviroScreen vulnerability score percentile for DACs within this group averages 68%.
Sizeable Crop Generalists (SCG).
This group consists of 13 districts formed during the Hydraulic Era and one pre-1914 (Fig 5, light orange). They have moderate surface water availability, with all districts receiving moderate surface water allocations (average 7 ML/Ha) and deliveries (average 6 ML/Ha). While they all have surface water allocations, 93% are groundwater-dependent. This group contains the highest count in DACs.
Forage and Cotton Corridor (FCC).
Comprising 27 districts along the western side of the San Joaquin Valley (Fig 5, yellow), most formed during the Hydraulic Era (n = 23). These older districts have relatively small service areas (347 to 41,250 Ha) and lower surface water availability. Although they have low crop water requirements (averaging 9 ML/Ha), around 81% are groundwater dependent. Despite their low crop water demands, most FCC districts may not exhibit high groundwater overdependence compared to irrigation districts in other groups.
Senior, Secure Nut Growers (SSN).
This group includes seven older and water-secure districts in the northern San Joaquin Valley (Fig 5, beige). They have large service areas (6,700 to 77,300 Ha) and the highest surface water allocations (31 to 50 ML/Ha) and deliveries (0.09 to 10 ML/Ha) among all groups. Despite a significant portion of crop area dedicated to almonds (41%) and walnuts (8%), their perennial crop revenue is comparatively lower (USD2,200). These districts are the least groundwater-dependent, with 30% relying on groundwater to meet irrigation demand. DACs within this group have high CalEnviroScreen vulnerability score percentiles (average of 86%) and the second-highest DAC count (18) compared to other groups.
Based on the findings, several key water management recommendations can be deduced to address the vulnerabilities and challenges faced by different irrigation district groups. Firstly, for districts heavily reliant on groundwater like the GDV, there may be a higher need for the implementation of a combination of water demand reductions (e.g., land repurposing, water trading, and shifts to less-water-intensive crops). Additionally, promoting crop diversification, particularly in districts dominated by a single crop like grapes in GDV or citrus in CCB, can help reduce overall water demand and provide flexible land use adaptation strategies during droughts and enhance resilience. Efficient irrigation practices, such as drip or sprinkler systems, and a combination of water and land use management strategies should be encouraged to minimize water use, especially in high-water-demand districts like CCB and GDV. Moreover, optimizing surface water allocation, groundwater recharge, and land use across groundwater dependent groups could help reduce vulnerabilities. Complying with SGMA is essential for heavily groundwater-dependent districts, and support in developing groundwater sustainability plans is crucial. Investing in water storage, such as groundwater recharge, can mitigate surface water shortages during droughts. Streamlining water rights administration, promoting regional collaboration, continuous monitoring, community support, and education are additional strategies to enhance water management and resilience, tailored to the specific needs and vulnerabilities of each district. Lastly, ongoing research and innovation efforts are essential to develop water-saving technologies and strategies applicable across all irrigation districts. Collaboration between government agencies, water authorities, and local communities is pivotal in implementing these recommendations effectively.
4. Conclusion
This geospatial study delves into the intricacies of local water governance and management, focusing specifically on irrigation districts within California’s San Joaquin Valley. By examining the historical and cultural factors embedded in these irrigation districts and their water management practices, this study aims to shed light on the complex interplay among water resources, society, and the legal system. These insights are crucial for developing resilient water management plans in the face of climate change while also addressing prolonged water access inequities.
Early in California’s water development history, the concept that "water is property, and control of water is control of society" played a pivotal role in shaping the state’s water management landscape. This philosophy significantly influenced the formation and governance structures of irrigation districts and surface water rights in California, reflecting historical and cultural contexts. These laws and governance entities underscore the role of human agency in shaping water control for irrigation and the utilization of surface water supplies across California’s agricultural regions.
The period in which irrigation districts were established has had a lasting impact on their ability to adapt to climate change and evolving water laws, such as SGMA. For example, older irrigation districts formed before 1914 are less reliant on groundwater compared to more recently established districts. Their substantial claims to surface water supplies provide them with greater control and flexibility in managing water resources, enhancing their resilience in the face of climate change. It’s worth noting that a substantial 86% of irrigation districts in the San Joaquin Valley currently depend on groundwater for agricultural irrigation, with 12% relying exclusively on it. Regardless of age or formation era, all districts are vulnerable to groundwater dependence in a changing climate and amid population growth. However, an inherent water access inequity exists in irrigation water governance, favoring older districts with stronger claims to surface water. These districts enjoy higher surface water capacity and greater autonomy in water control, lessening their susceptibility to interference from the SWRCB.
The primary drivers of groundwater dependence across irrigation districts are instances where crop water requirements surpass surface water delivery capacities. For effective climate change adaptation strategies, policies must collaborate with existing frameworks to address and narrow the water access inequity gap in current governance structures. This study also reveals that DACs within local government jurisdictions are not significantly better off than GDCs. This can be traced back to the historical and cultural context in which irrigation districts were established, primarily to secure water for irrigated agriculture. To create water management solutions that balance competing freshwater demands and tackle water access inequities in marginalized communities, water governance entities must engage inclusively and meaningfully.
To ensure a secure future for food and water in California and beyond, the state must implement climate change adaptation strategies at the local, regional, and state levels that address water access inequities faced by marginalized groups. SGMA presents an opportunity to revamp surface water and groundwater management for climate change resilience. Addressing excessive water allocation, particularly through the surface water rights system, which represents 861% of the San Joaquin River’s natural surface water supplies, is vital [24]. The onset of California’s 2021 drought highlighted the unsustainability of current surface water allocations under the existing water rights system. In August 2021, the SWRCB curtailed water claims for all principal water rights in the Sacramento River, San Joaquin River, and the Delta (the waterwheel of California water supplies) [52]. California must also learn from the experiences of countries like Australia and South Africa, which reformed their water rights systems to promote sustainability, efficiency, and social justice. These reforms were necessitated by the failure of existing regulatory frameworks to effectively and equitably manage water allocation and distribution [53]. California’s challenges in the San Joaquin Valley share similarities with those faced by these countries, including long-standing mismanagement of natural water resources driven by market-oriented decision-making and governance that often favors vested interests. To move forward, California must develop climate change adaptation strategies for water management while avoiding the pitfalls seen in Australia’s Murray-Darling Basin Plan [54, 55]. Achieving this requires policies and governance structures that reduce bias and ensure a balance between freshwater demands, all while addressing water access inequities in future water and land use decisions.
Supporting information
S1 Table. List of major datasets and sources.
https://doi.org/10.1371/journal.pwat.0000192.s001
(DOCX)
S2 Table. Irrigation district variables and their associated acronyms, units, and descriptions.
https://doi.org/10.1371/journal.pwat.0000192.s002
(DOCX)
S3 Table. Irrigation district DAC (ID_DAC) and groundwater dependent communities (GDC) list and statistics.
https://doi.org/10.1371/journal.pwat.0000192.s003
(DOCX)
Acknowledgments
We are grateful to Timothy H. Quinn, Harrison B. Zeff, Matt Angell, Jason Peltier, Bob Kelley, George Kelley, Ric Ortega, Jelena Jezdimirovic, Alvar Escriva-Bou, Colleen Naughton, Josue Medellin-Azuara, Leigh Bernacchi, Erin Hestir, and On the Public Record (onthepublicrecord.org) for insightful conversations and insights that helped shape this paper. We thank the San Joaquin Valley irrigation district managers for their time and help to confirm the accuracy in surface water allocation and delivery amounts and other related irrigation district information. Local Agency Commission Formation offices (LAFCO) provided updated irrigation district service boundaries, and the State Water Resources Control Board provided up-to-date water rights data. We thank the reviewers for suggestions that helped improve this manuscript.
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