In the state of California, groundwater serves 85% of Californians for at least part of their water. During the last drought (2011–2016), a high proportion of domestic wells went dry, most of which were located in disadvantaged communities (DACs) in the California Central Valley. Prior to 2014, voluntary groundwater management plans (GMPs) existed as one of the main groundwater governance options. However, little is known about the adoption of these GMPs and their effect on groundwater management. This case study analyzes the adoption of voluntary GMPs statewide and their impact on DACs that primarily rely on groundwater for drinking water. Our analysis shows low adoption of voluntary GMPs (15% for Assembly Bill [AB] 3030 and 12% for Senate Bill [SB] 1938) by local agencies. Even though GMPs were most frequently adopted in the Central Valley, the majority of domestic well shortages and DACs are concentrated there. Furthermore, water agencies, such as irrigation and water districts, had the highest adoption rate (70%), followed by cities (18%) and counties (7%), which indicates that institutional capacity is key for groundwater management. However, since only public agencies were eligible to adopt GMPs, the inclusion of private groundwater users within public agencies is questionable. In sum, the lack of voluntary GMP adoption shows that they were unsuccessful in incentivizing or facilitating institutional action. Finally, restrictions on eligibility to design GMPs underscore the persistent challenge of involving all users in local water management, which may be key to close the gap between policy design and socio-ecological outcomes.

## INTRODUCTION

Groundwater is a critical resource in the state of California, especially in arid and semiarid regions where surface water supply cannot meet the demand. Because surface water is widely and unevenly distributed throughout the state, groundwater has for a long time supplied drinking water to urban and rural populations and irrigation water to farmers. It is more widely accessible and less vulnerable to quality degradation and droughts than surface water [1]. In average years, 40% of the state’s water supply comes from groundwater. During drought years, groundwater serves as a critical buffer against the impacts of drought, providing 60% of the state’s water supplies [2]. As a source of drinking water, groundwater serves 85% of Californians for at least part of their water [3]. In the Central Valley in particular, most disadvantaged communities (DACs)—communities with a median household income (MHI) that is less than 80% of the state median—rely on groundwater for up to 100% of their domestic water supply needs [4].

Since the 1930s, groundwater extraction in California has exceeded natural aquifer recharge, causing historically low groundwater elevations in many parts of the state, leading to undesirable results such as land subsidence, water quality degradation, seawater intrusion in coastal areas, and chronic lowering of the water table [5]. During the last California drought (2011–2016), the pace of well drilling increased dramatically, as farmers and communities sought new water depths from aquifers to substitute the absence of surface water. This rampant extraction was further stressed by the lack of statewide mandatory groundwater regulation or institutions to manage the resource. In some agricultural regions in the Central Valley, groundwater overdraft averaged 2 million acre-feet per year during the 2012–2016 drought [5]. Consequently, as water tables dropped, more than 3,500 shallow domestic wells went dry, most of which are located in DACs [4], showing that minority and disadvantaged populations are the most vulnerable to climate change events, such as droughts [6, 7]. In California, specifically, drinking water access, quality, and affordability disproportionately affect DACs of color, particularly in rural areas [811].

In 2014, the drought, coupled with unsustainable groundwater extraction, spurred the adoption of California’s Sustainable Groundwater Management Act (SGMA) [12]. The Act gives local agencies the tools and authority to develop and implement strategies to sustainably manage their groundwater resources by 2040 [13]. However, this requires multilevel stakeholder participation and coordination across political, geographic, and hydrologic boundaries. Therefore, it is important to examine previous efforts to manage groundwater to understand the development of new institutions under SGMA, and if and how it may include historically marginalized stakeholders who rely heavily on groundwater from water decision-making processes.

## CASE EXAMINATION

### California’s Hydrology

The majority of California’s accessible groundwater is stored in alluvial groundwater basins. California has 10 major drainage basins, also known as hydrologic regions: North Coast, Sacramento River, North Lahontan, San Francisco Bay, San Joaquin River, Central Coast, Tulare Lake, South Lahontan, South Coast, and Colorado River [5]. Hydrologic regions are divided into 515 groundwater basins and subbasins: 431 groundwater basins, 24 of which are subdivided into a total of 108 subbasins. These alluvial basins cover approximately 40% of the state’s geographic area [14, 15].

In California, there is a discrepancy between the distribution of water resources and demand due to the state’s large geographic scope, seasonal and climatic variability, and location of large population centers in the southern portion of the state relative to the primary sources of water in the north. Approximately 70% of the state’s average annual runoff occurs north of Sacramento, while about 75% of the state’s urban and agricultural water demands are to the south [14, 15]. This discrepancy poses water supply and management challenges.

### California Central Valley

Geographically located at the heart of California, the Central Valley can be divided into two regions: Sacramento Valley to the north and San Joaquin Valley to the south [16]. The two valleys are defined by the Sacramento and San Joaquin rivers, respectively, that converge in the Bay-Delta. For groundwater, the Sacramento Valley includes the Sacramento River basin, while the San Joaquin Valley includes the San Joaquin River and Tulare Lake basins. The California Central Valley, a rich agricultural region that faces socioeconomic disparities, provides an opportunity to evaluate the complexities and challenges of groundwater management both historically and currently.

#### Sacramento Valley

The Sacramento Valley accounts for approximately 40% of the Central Valley population with 3 million people and covers approximately 17.4 million acres [17]. Unlike the San Joaquin Valley, it is predominantly composed of non-Hispanic White and Hispanic or Latino residents (Table 1). The MHI in the Sacramento Valley is $52,182, with approximately 16% of residents falling below the poverty line (Table 1) [17]. The majority of the population resides in rural, agricultural areas [17]. Six out of the eight counties that comprise the Sacramento Valley qualify as DACs, with an MHI below 80% threshold. Overall, the Sacramento Valley has an MHI that is 73.3% of the state’s MHI [18]. For water supply, the Sacramento River and groundwater are important sources of drinking water. Groundwater provides about 31% of the water supply for urban purposes in the region [14, 15]. TABLE 1. Income, poverty, and demographic statistics RegionTotal populationMHI% Population below the poverty line% Hispanic or Latino California 39,250,017$64,500 15.3 38.8
San Joaquin Valley 4,173,563 $46,713 16.4 52.8 Fresno 979,915$45,233 25.2 52.4
Kern 884,788 $49,026 21.9 52.2 Kings 149,785$46,481 22.4 53.6
Madera 154,697 $45,073 22.6 56.7 Merced 268,672$42,462 25.9 58.2
San Joaquin 733,709 $53,274 17.5 40.8 Stanislaus 541,560$50,125 19.5 44.8
Tulare 460,437 $42,031 27.2 63.6 Sacramento Valley 2,987,788$52,182 16.1 26.2
Butte 226,864 $43,444 21.4 15.7 Colusa 21,588$52,168 13.2 58.5
El Dorado 185,625 $69,584 9.1 12.8 Glenn 28,085$39,349 18.5 41.1
Placer 380,531 $73,948 8.6 13.8 Sacramento 1,514,460$55,987 16.9 22.7
Shasta 179,631 $44,620 19.0 9.6 Sutter 96,651$52,017 17.5 30.0
Tehama 63,276 $41,001 22.5 24.4 Yolo 215,802$54,989 17.5 31.5
Yuba 75,275 $46,892 21.6 27.5 RegionTotal populationMHI% Population below the poverty line% Hispanic or Latino California 39,250,017$64,500 15.3 38.8
San Joaquin Valley 4,173,563 $46,713 16.4 52.8 Fresno 979,915$45,233 25.2 52.4
Kern 884,788 $49,026 21.9 52.2 Kings 149,785$46,481 22.4 53.6
Madera 154,697 $45,073 22.6 56.7 Merced 268,672$42,462 25.9 58.2
San Joaquin 733,709 $53,274 17.5 40.8 Stanislaus 541,560$50,125 19.5 44.8
Tulare 460,437 $42,031 27.2 63.6 Sacramento Valley 2,987,788$52,182 16.1 26.2
Butte 226,864 $43,444 21.4 15.7 Colusa 21,588$52,168 13.2 58.5
El Dorado 185,625 $69,584 9.1 12.8 Glenn 28,085$39,349 18.5 41.1
Placer 380,531 $73,948 8.6 13.8 Sacramento 1,514,460$55,987 16.9 22.7
Shasta 179,631 $44,620 19.0 9.6 Sutter 96,651$52,017 17.5 30.0
Tehama 63,276 $41,001 22.5 24.4 Yolo 215,802$54,989 17.5 31.5

### Groundwater in the Central Valley

The Central Valley relies heavily on groundwater. It has the highest concentration of domestic wells than any other region in the state. Approximately 91,576 domestic wells are located there, representing 60.5% (91,576/151,365) of all domestic wells statewide [21]. From January 2014 to February 2017, California Department of Water Resources (DWR) reported 3,511 household water shortages, with the majority reported in Central Valley counties: Tulare, Madera, Fresno, Mariposa, Merced, and Stanislaus [22]. However, not all household shortages may be included in these figures for various reasons: not all counties have reporting mechanisms; people who are financially able to deepen or drill wells are unlikely to report a well shortage; and people may choose not to report a shortage because they prefer avoiding interaction with government officials [23].

Starting in 2009, DWR prioritized California’s groundwater basins and subbasins through the California Statewide Groundwater Elevation Monitoring (CASGEM) program. Based on several criteria,1 groundwater basins are characterized as high, medium, low, or very low priority for groundwater management. CASGEM findings indicate that 127 of California’s 515 groundwater basins and subbasins are high and medium priority, 43 and 84, respectively [14, 15]. These 127 basins, primarily located in the Central Valley, account for 96% of California’s annual groundwater pumping (Table 2).

TABLE 2.

Statewide summary of CASGEM basin prioritization

CASGEM rankingPercentages for high- and medium-ranked basin

Hydrologic regionHighMediumLowVery lowBasin countGroundwater use (%)Overlying population (%)
North Coast 53 63 82 62
San Francisco Bay 26 33 90 63
Central Coast 15 36 60 97 90
South Coast 13 22 34 73 99 94
Sacramento River 18 61 88 96 98
San Joaquin River 11 100 100
Tulare Lake 10 19 99 98
North Lahontan 22 27 12 55
South Lahontan 67 77 84 96
Colorado River 50 64 82 61

Total 43 84 27 361 515 96 88
CASGEM rankingPercentages for high- and medium-ranked basin

Hydrologic regionHighMediumLowVery lowBasin countGroundwater use (%)Overlying population (%)
North Coast 53 63 82 62
San Francisco Bay 26 33 90 63
Central Coast 15 36 60 97 90
South Coast 13 22 34 73 99 94
Sacramento River 18 61 88 96 98
San Joaquin River 11 100 100
Tulare Lake 10 19 99 98
North Lahontan 22 27 12 55
South Lahontan 67 77 84 96
Colorado River 50 64 82 61

Total 43 84 27 361 515 96 88

Source: Adapted from DWR [34] data.

### California’s Historical Groundwater Management

Prior to SGMA, groundwater management was voluntary. Three basic methods existed for managing groundwater resources: adjudication through the court system (judicial route), creation of special act districts via the legislature (legislative route), or the creation of voluntary groundwater management plans (GMPs) through local governance and incentivized by the legislature [24]. Until 2014, there was no executive branch to regulate groundwater.

#### Voluntary Groundwater Management Plans

Assembly Bill 3030 (AB 3030) was signed into law in 1992 and provided a common framework for existing local agencies to develop GMPs (California Water Code Section 10750 et seq [24]). It was significant because it set forth a common framework for management by local agencies, although the action was entirely voluntary.

In 2002, the legislature passed Senate Bill 1938 (SB 1938), which amended Water Code section 10750 et seq, by including financial incentives and basic minimum requirements for the development of GMPs [24]. However, adoption remained voluntary.

#### Sustainable Groundwater Management Act

In 2014, Governor Jerry Brown signed the state’s first statewide groundwater management regulation into law—the SGMA or “Sigma”. SGMA does not empower the state to directly regulate groundwater use under its permitting system but instead directs local agencies to sustainably manage their basins [2]. Theoretically, it is part of an effort to respect local governance and control of groundwater resources in a way that is tailored to the unique resources and needs of communities [25]. However, decentralized local management is not new in water resource governance, and it is fraught with many challenges [26, 27]. Under SGMA, local agencies overlying any of the 127 high- or medium-priority groundwater basins in the state (Figure 1) were required to form groundwater sustainability agency (GSA) or groundwater sustainability agencies (GSAs) for each basin by June 30, 2017, excluding already adjudicated groundwater basins. GSAs are then required to develop and implement groundwater sustainability plan(s) (GSPs), which outline how GSAs may achieve sustainable groundwater management. GSPs must be adopted by 2020 or 2022, depending on the basin’s CASGEM priority. GSAs then have until 2040 to achieve groundwater sustainability [2].

FIGURE 1.

CASGEM basin priority map (Source: DWR [34]).

FIGURE 1.

CASGEM basin priority map (Source: DWR [34]).

## METHODS

### Database Creation

To understand the complexity and diversity of groundwater management in California, we created a master database by integrating the following four databases:

• (1)

The Environmental Protection Agency (EPA) Safe Drinking Water Information System (SDWIS) Database

• (2)

Water Districts Database (Department of Water Resources)

• (3)

Institutional database on institutional organizational structures, AB 3030 and SB 1938 adoption, and time of completion (compiled by members of the Center for Environmental Policy and Behavior at the University of California, Davis)

• (4)

CASGEM Groundwater Basin Prioritization Database

These four databases were merged to create a single database that embeds all public water agencies (i.e., irrigation and water districts) overlaying groundwater basin/subbasins in California. In many cases, a water agency is embedded in more than one basin/subbasin.

### Geographic Analysis of DACs

To our knowledge, there are currently no available data that georeference DACs within groundwater basins and little is known about the location and frequency of DACs by hydrologic region, especially with respect to groundwater access and domestic drinking water wells. This case study aims to fill that knowledge gap. To address this, we created a map (Figure 2) in ArcGIS using data from DWR’s Bulletin 118 groundwater basin/subbasin boundaries and DAC Mapping Tool, which provides shapefiles of DACs using US Census ACS 2010–2014 data (Census Block Groups). A spatial join was performed to extract data on the location and frequency of DACs per hydrologic region and groundwater basin/subbasin throughout California.

FIGURE 2.

Number of DACs per groundwater basin in California. A DAC is a community with an MHI that is less than 80% of the state median (Source: the authors).

FIGURE 2.

Number of DACs per groundwater basin in California. A DAC is a community with an MHI that is less than 80% of the state median (Source: the authors).

## RESULTS AND DISCUSSION

### Database Analysis

Of the 1,044 agencies identified in our database, the greatest proportion of public water agencies, such as irrigation and water districts, are in the Sacramento River hydrologic region (22%), followed by the South Coast (18%), Tulare Lake (16%), and the San Joaquin River (13%; Figure 3).

FIGURE 3.

Proportion of agencies by hydrologic region (Source: the authors).

FIGURE 3.

Proportion of agencies by hydrologic region (Source: the authors).

FIGURE 4.

Proportion of AB 3030 GMPs by hydrologic region (Source: the authors).

FIGURE 4.

Proportion of AB 3030 GMPs by hydrologic region (Source: the authors).

FIGURE 5.

Proportion of SB 1938 GMPs by hydrologic region (Source: the authors).

FIGURE 5.

Proportion of SB 1938 GMPs by hydrologic region (Source: the authors).

FIGURE 6.

Proportion of AB 3030 and SB 1938 GMPs by hydrologic region (Source: the authors).

FIGURE 6.

Proportion of AB 3030 and SB 1938 GMPs by hydrologic region (Source: the authors).

FIGURE 7.

GMP adoption rate by public agency (Source: the authors).

FIGURE 7.

GMP adoption rate by public agency (Source: the authors).

The majority of existing AB 3030 and SB 1938 GMPs (35% and 32%, respectively) are located in high- and medium-priority basins (Figures 8 and 9). In the Central Valley, where groundwater use is intense according to CASGEM basin prioritization (Table 2), voluntary GMPs were more likely to be adopted: 81% of AB 3030 and 80% of SB 1938 GMPs were adopted in the Tulare Lake, San Joaquin River, and Sacramento River hydrologic regions. This concurs with the institutional theory [29, 30] that has shown that low resource availability provides an important incentive for collective action. When competition for a scarce resource is high, such as groundwater in the Central Valley, the benefit of engaging with other stakeholders may be greater than seeking short-term individual gains. However, the design of GMPs did not necessarily mean that conditions of overdraft would be reduced or that groundwater would be managed sustainably in the absence of GMP implementation, compliance, or coordination with other groundwater users. As witnessed during the last drought (2011–2016), the presence of voluntary GMPs did not translate into cohesive and organized action to manage unrestricted and unsustainable groundwater extraction.

FIGURE 8.

Proportion of agencies with an AB 3030 plan by CASGEM basin priority (Source: the authors).

FIGURE 8.

Proportion of agencies with an AB 3030 plan by CASGEM basin priority (Source: the authors).

FIGURE 9.

Proportion of agencies with an SB 1938 plan by CASGEM basin priority (Source: the authors).

FIGURE 9.

Proportion of agencies with an SB 1938 plan by CASGEM basin priority (Source: the authors).

### Geographic Analysis of DACs

In California, the majority of DACs are concentrated in the Central Valley (Figure 9). Of the DACs identified in California, Tulare Lake, San Joaquin River, and Sacramento River hydrologic regions—which are all located in the Central Valley—and South Coast hydrologic region had the highest proportion of DACs, with 35%, 29%, 14%, and 13%, respectively (Figure 10). The high concentration of DACs in these regions makes them particularly susceptible to groundwater shortages, especially as DACs primarily or completely rely on groundwater. This highlights the inconsistency between plan adoption and socio-ecological outcomes in the Central Valley, while evidence suggests that collaborative governance improves environmental outcomes [31]. Engaging diverse stakeholder interests is thus critical for optimizing groundwater management to ensure equitable and sustainable outcomes while underscoring the limitations of voluntary GMPs.

FIGURE 10.

Proportion of DACs in California per groundwater basin. The majority of DACs are located in the Tulare Lake, San Joaquin River, Sacramento River, and South Coast hydrologic regions (Source: the authors).

FIGURE 10.

Proportion of DACs in California per groundwater basin. The majority of DACs are located in the Tulare Lake, San Joaquin River, Sacramento River, and South Coast hydrologic regions (Source: the authors).

Under SGMA, GSAs limit formal membership to local agencies (Water Code, § 10721, (j)(n)), which raises questions about the ability of the nonpublic agency groups, such as independent farmers or DACs with private wells, to participate in a GSA [32]. From a historical perspective, previous voluntary management efforts in California groundwater emphasize the importance of collective action and institutional design [33]. The direct and meaningful inclusion of DACs in decision-making processes through GSAs may allow vulnerable communities to ensure that the costs and benefits of groundwater extraction are equitably distributed, which requires careful institutional design that addresses environmental and social considerations and establishes fair mechanisms for participation.

Even though GMPs were most frequently adopted in the Tulare Lake, San Joaquin, and Sacramento River regions in the Central Valley, the majority of domestic well shortages occurred in these regions where DACs are concentrated. This gap highlights the inconsistency between plan adoption and socio-ecological outcomes, which may be explained by: 1) the voluntary nature of the GMPs; 2) the lack of requirements for the voluntary GMPs; and 3) the exlusion of DACs and private domestic well owners, despite being significantly impacted by the drought and groundwater over-extraction, in groundwater management and planning.

## CONCLUSION

As a fairly accessible resource and with no limits on extraction, groundwater has been heavily overextracted in California. Compounded with the effects of drought, groundwater overextraction led to substantial decreases in the water table, particularly the Central Valley. The analysis of previous efforts to manage groundwater can provide insights into the dynamics of new institutions forming under SGMA. Our analysis shows low adoption of voluntary GMPs (15% for AB 3030 and 12% for SB 1938) by local agencies. Even though GMPs were adopted most frequently in the Sacramento River, San Joaquin River, and Tulare Lake hydrologic regions (81% for AB 3030 and 80% for SB 1938)—all three of which are part of the Central Valley, the majority of domestic well shortages also occurred in these regions where DACs are concentrated (57%). Furthermore, water agencies such as irrigation and water districts had the highest adoption rate (70%), followed by cities (18%) and counties (7%) which indicates that institutional capacity is key for groundwater management. However, since only public agencies were eligible to adopt GMPs (same as SGMA), private domestic well owners were unable to formally participate in groundwater management and their inclusion within existing public agencies is questionable. In sum, the lack of voluntary GMP adoption, which primarily affected shallow well owners during droughts, shows that the promotion of voluntary GMPs was unsuccessful in incentivizing groundwater management or facilitating institutional action. Finally, restrictions on eligibility to design GMPs underscore the persistent challenge of involving all users in local water management, which may be key to close the gap between policy design, GMP adoption, and socio-ecological outcomes.

## CASE STUDY QUESTIONS

1. What lessons can be drawn about previous groundwater management efforts to inform the creation of sustainable groundwater institutions under SGMA?

2. SGMA places management authority at the local level, which can be contentious where there are competing interests and power asymmetries among local actors—what are legal ways to balance the power dynamics among stakeholders?

3. To what extent should the government be held accountable for not including certain, often marginalized, stakeholders, such as Native American tribes and DACs, into decision-making processes?

4. What are ways in which the government can encourage meaningful involvement of stakeholders in groundwater decision-making?

5. What role do race and ethnicity play in access to safe drinking water and historical patterns of exclusion in California?

## AUTHOR CONTRIBUTIONS

CM wrote the original draft and LEM reviewed and edited the case study. This was part of CM’s honor thesis, in which LEM guided and advised.

The authors would like to thank Dr. Mark Lubell at the Center for Environmental Policy and Behavior, University of California, Davis, for his guidance and constructive suggestions and Amanda Fencl for her valuable insights.

## FUNDING

LEM received funding from the National Science Foundation Graduate Research Fellowship and the Climate Change, Water and Society NSF IGERT at UC Davis.

## COMPETING INTERESTS

The authors have declared that no competing interests exist.

1.

The eight criteria include overlying population, projected growth of overlying population, public supply wells, total number of wells, irrigated acreage overlying the basin, reliance on groundwater as the primary source of water, impacts on groundwater, and any other relevant information (Cal. Water Code (CWC) (§10933)).

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