Groundwater models through stakeholders’ eyes: Evaluating benefits, challenges, and lessons for SGMA implementation

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

California's San Joaquin Valley is a major agricultural region, but its reliance on irrigated farming has caused severe groundwater overdraft, leading to land subsidence and potential seismic risks. To address this, the 2014 Sustainable Groundwater Management Act (SGMA) aims to achieve groundwater sustainability by 2040. Compliance with SGMA is expected to remove significant land from production, prompting efforts to repurpose former farmland for multibenefit uses. Since most of this land is privately owned, understanding producer perspectives is essential. This study explores those perspectives through interviews with 9 producers and analysis of 91 local newspaper articles. Data were coded using NVivo software to identify patterns related to SGMA impacts and land repurposing views. Results show producers experience uncertainty and frustration with SGMA but remain cautiously optimistic about future social and environmental benefits. SGMA has also encouraged more stakeholder collaboration. Solar energy projects and groundwater recharge were seen as promising repurposing options, while habitat conservation efforts were seen as less viable without financial incentives. These findings offer insights into how policy-driven land transitions are perceived by producers and provide guidance for similar efforts in other arid and semi-arid regions worldwide.

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.

California water law has traditionally treated groundwater and surface water as separate resources. The 2014 Sustainable Groundwater Management Act (SGMA) broke with this tradition by requiring groundwater managers to avoid significant and unreasonable adverse impacts to beneficial uses of surface water. This paper considers the trajectory of this partial integration of science, law, and resource management policy. Drawing on legal analysis and participatory workshops with subject area experts, we describe the challenges of reconciling the separate legal systems that grew out of an artificial legal distinction between different aspects of the same resource. Our analysis offers two main contributions. First, it demonstrates that laws that subdivide an interconnected resource can have legacy effects that linger long after lawmakers begin dismantling the artificial divides. Using SGMA as a case study, the article illustrates the complexities of reconciling law with science, showing that reconciliation is a process that does not end with updating statutes, or with any other single intervention. Second, we introduce a framework for evaluating the elements of an effort to reconcile law with scientific understanding, whether that reform effort involves groundwater or some other resource. Applying that framework helps reveal where lingering legacy effects still need to be addressed. More generally, it reveals the need for literature addressing science-policy interactions to devote more attention to the multifaceted nature of law and policy reform. Much of that literature describes policy-making in broad and undifferentiated terms, often referring simply to ‘the science-policy interface.’ But as the SGMA case study illustrates, the complex and multi-layered nature of policy-making means that a successful reform effort may need to address many science-policy interfaces.

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.

<p>Improving water resource management in the western United States is critically needed to achieve sustainability between the competing demands of water supplies for cities and towns, for agriculture, particularly irrigated regions, by industries principally for generating electricity, and for the environment (i.e., providing adequate ecosystem services). The last decade marked by historically severe droughts revealed the need for new water management policies and environmental regulations. Moreover, the impact of climate change not only has exacerbated droughts but also may be causing episodic extreme wet periods requiring a new paradigm on water management strategies for surface water reservoirs and groundwater aquifers. The Sustainable Groundwater Management Act (SGMA) is an example of developing a water management policy for sustainability of water resources in California. California produces 80% of the world’s almonds, is the 4<sup>th</sup> largest wine producer worldwide while also providing three-quarters of the fruits and nuts in the U.S. Much of the production requires reliable water sources for irrigation.  This has motivated research into designing networks of evapotranspiration (ET) flux tower measurements in grape and tree crop systems in conjunction with developing new remote sensing tools for mapping crop water use, ET, to efficiently use and conserve water resources across the over 1.5 million acres of woody perennial crop production fields.  This acreage is largely irrigated and uses approximately 70% of freshwater resources in the region.  The two projects, GRAPEX (Grape Remote sensing Atmospheric Profile and Evapotranspiration eXperiment) and T-REX (Tree-crop Remote sensing of Evapotranspiration eXperiment) have the overall goal to identify management opportunities to maximize water use efficiency in vineyard, almond and other woody perennial crops.  This presentation will describe the measurement network used for understanding the water and energy flux exchange of these complex cropping systems and in validating and refining remote sensing modeling tools from UAS and satellite platforms for estimating ET and crop water stress from plant and sub field to regional scales required for improving water management strategies of these agricultural systems.</p>

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.

Management of groundwater resources is increasingly reliant on numerical simulation. Unfortunately, decision-support modelling is often conducted under the premise that predictive reliability increases with modelling complexity. In truth, while modelling complexity can support quantification of predictive uncertainty, the latter is a function of data availability. Excessive complexity can often erode, rather than enhance, a model’s ability to quantify and reduce the uncertainties of decision-critical predictions by reducing its capacity to assimilate prediction-salient information. We submit that a groundwater model is more productively viewed as a data assimilator for decision-pertinent information than as simulating subsurface processes, even though the latter role (though imperfect) underpins the former. Assimilated data may, or may not, allow rejection of the hypothesis that a certain course of management action will have adverse consequences. Either way, the decision-making process requires that this hypothesis be tested. In the following document, we outline how decision-support environmental modelling can be implemented with the scientific method, and discuss how uncertainties of decision-salient predictions can be addressed with appropriate model complexity so that stakeholder expectations are better aligned with what models can and cannot deliver to the decision-making process.

Environmental restoration at the Shoal underground nuclear test is following a process prescribed by a Federal Facility Agreement and Consent Order (FFACO) between the U.S. Department of Energy, the U.S. Department of Defense, and the State of Nevada. Characterization of the site included two stages of well drilling and testing in 1996 and 1999, and development and revision of numerical models of groundwater flow and radionuclide transport. Agreement on a contaminant boundary for the site and a corrective action plan was reached in 2006. Later that same year, three wells were installed for the purposes of model validation and site monitoring. The FFACO prescribes a five-year proof-of-concept period for demonstrating that the site groundwater model is capable of producing meaningful results with an acceptable level of uncertainty. The corrective action plan specifies a rigorous seven step validation process. The accepted groundwater model is evaluated using that process in light of the newly acquired data. The conceptual model of ground water flow for the Project Shoal Area considers groundwater flow through the fractured granite aquifer comprising the Sand Springs Range. Water enters the system by the infiltration of precipitation directly on the surface of the mountain range. Groundwater leaves the granite aquifer by flowing into alluvial deposits in the adjacent basins of Fourmile Flat and Fairview Valley. A groundwater divide is interpreted as coinciding with the western portion of the Sand Springs Range, west of the underground nuclear test, preventing flow from the test into Fourmile Flat. A very low conductivity shear zone east of the nuclear test roughly parallels the divide. The presence of these lateral boundaries, coupled with a regional discharge area to the northeast, is interpreted in the model as causing groundwater from the site to flow in a northeastward direction into Fairview Valley. Steady-state flow conditions are assumed given the absence of groundwater withdrawal activities in the area. The conceptual and numerical models were developed based upon regional hydrogeologic investigations conducted in the 1960s, site characterization investigations (including ten wells and various geophysical and geologic studies) at Shoal itself prior to and immediately after the test, and two site characterization campaigns in the 1990s for environmental restoration purposes (including eight wells and a year-long tracer test). The new wells are denoted MV-1, MV-2, and MV-3, and are located to the northnortheast of the nuclear test. The groundwater model was generally lacking data in the north-northeastern area; only HC-1 and the abandoned PM-2 wells existed in this area. The wells provide data on fracture orientation and frequency, water levels, hydraulic conductivity, and water chemistry for comparison with the groundwater model. A total of 12 real-number validation targets were available for the validation analysis, including five values of hydraulic head, three hydraulic conductivity measurements, three hydraulic gradient values, and one angle value for the lateral gradient in radians. In addition, the fracture dip and orientation data provide comparisons to the distributions used in the model and radiochemistry is available for comparison to model output. Goodness-of-fit analysis indicates that some of the model realizations correspond well with the newly acquired conductivity, head, and gradient data, while others do not. Other tests indicated that additional model realizations may be needed to test if the model input distributions need refinement to improve model performance. This approach (generating additional realizations) was not followed because it was realized that there was a temporal component to the data disconnect: the new head measurements are on the high side of the model distributions, but the heads at the original calibration locations themselves have also increased over time. This indicates that the steady-state assumption of the groundwater model is in error. To test the robustness of the model despite the transient nature of the heads, the newly acquired MV hydraulic head values were trended back to their likely values in 1999, the date of the calibration measurements. Additional statistical tests are performed using both the backward-projected MV heads and the observed heads to identify acceptable model realizations. A jackknife approach identified two possible threshold values to consider. For the analysis using the backward-trended heads, either 458 or 818 realizations (out of 1,000) are found acceptable, depending on the threshold chosen. The analysis using the observed heads found either 284 or 709 realizations acceptable. The impact of the refined set of realizations on the contaminant boundary was explored using an assumed starting mass of a single radionuclide and the acceptable realizations from the backward-trended analysis.

Causes and implications of groundwater depletion in India: A review

Groundwater modeling has proved to be a powerful tool for understanding the behavior of the groundwater system. Generally, a groundwater model is a conceptual description or mathematical approximations that describe the physical system. Groundwater models are applied in groundwater resource management for sustainable development. It is important to understand general aspects of the groundwater flow models so that the application or the evaluation of these models are performed correctly. In this case, the governing equation, initial and boundary conditions, solving method, and modeling procedures are elaborated. The modeling procedures include constructing the conceptual model, designing the numerical model, providing inputs to the model, calibration and validation of the model. For illustrating the concept of this groundwater model, a simple hypothetical case study is presented. The hypothetical case is formulated by assuming a confined aquifer that is bound by two parallel rivers in the east and west. The north and south sides of the model domain are considered as an impermeable boundary. The first case was when there was no pumping and hence the model was run to simulate natural groundwater flow. It was observed that the groundwater level decreases approximately 0.5 m/200 m from the 228west river and the inflow from the river was 1728.46 m3/day. In the second case, where pumping was considered, the maximum drop of groundwater level was 2.7 m in the center of the cone of depression and inflow from the left river increased to 2241 m3/day. The output of the model demonstrated groundwater head distribution and the impact of groundwater pumping on the aquifer response. The software used to demonstrate the hypothetical case was Visual MODFLOW flex. The case studies helped in understanding the concept of the groundwater model which is essentially required for sustainable groundwater resources management.

The groundwater quality in semiarid aquifers can deteriorate very rabidly, due to many factors. The most important factor affecting the quality of groundwater quality in Gaza Strip aquifer is the excess pumping due to the high population density in the area. The aim of this study is to investigate the impact of pumping on groundwater salinity using artificial neural networks (ANNs)-based model. For detailed study of the impact of pumping on chloride concertation, hypothetical cases of input variables have been assumed to study the influence of the pumping on the chloride concertation. The developed model with three levels of uncertainty has generated these cases. Results proved that groundwater salinity would be improved if the pumping rate is reduced. Based on the results of this study, an urgent calling for developing other drinking water resources to secure the water demand is the most effective solution to decrease the groundwater salinity.KeywordsGroundwater qualitySalinityWater resourcesSemiarid aquifers

The Food and Agriculture Organization of the United Nations (FAO) estimates that food production must be increased 70% (from 2009 levels) in order to feed an additional 2.3 billion people by 2050 (FAO 2009). Irrigated cropland is extremely important to global food security. According to FAO (2009), although irrigated cropland currently occupies only about 20% of the total agricultural area worldwide, it supplies roughly 40% of the total yield (i.e. 3.6 times that of dryland). Groundwater is an extremely important source of irrigation water. An estimated 38% of irrigated areas depend on groundwater (Siebert et al. 2010) and in the U.S., groundwater supplies 43% of the irrigation water (Maupin et al. 2014). At the same time, an increasing number of countries and regions are reaching alarming levels of water scarcity. According to NASA satellite data, 13 of the largest 37 aquifers in the world are considered significantly distressed (Richey et al. 2015). Severe aquifer depletion evident in the Ogallala Aquifer, California’s Central Valley, the Mississippi Delta, and Arizona’s alluvial basins (Konikow 2013) threaten food production in the U.S. How will we meet growing food demands and the water needs of growing populations in these regions with declining aquifers? How do we prolong, sustain, or restore these aquifers? When restoration is not possible, how do we best support the conversion to dryland or grazing systems? This JCWRE special issue examines new technologies, cropping system management practices, decision support tools, incentives and policies to sustain food production, rural communities, and ecosystem services in these critical regions. In particular, recent research advances from the decades long USDA-ARS funded Ogallala Aquifer Program, recently funded USDA-NIFA Ogallala Water Coordinated Agricultural Project, and regional efforts in California and the Mississippi Delta are discussed. Brauer et al. describe the research and education efforts of the Ogallala Aquifer Program conducted over the last decade and a half. USDA-ARS laboratories in Bushland and Lubbock TX, with university partners at Kansas State University, Texas A&M AgriLife Research and Extension Service, Texas Tech University and West Texas A&M University are developing and evaluating water management strategies and technologies to reduce water withdrawals for irrigation by 20% in 2020 (compared to 2012) and increase the productivity and profitability of dryland cropping systems, including developing best management practices for production of high value and alternative crops for both dryland and irrigated systems. This consortium is also working to improve the understanding of hydrological and climatic factors affecting water use and agricultural profitability and determining the impacts of alternative water withdrawal/use policies on the economic viability of the agriculture industry of the Southern Ogallala Aquifer region. These efforts are extremely important, particularly with the warming trends documented by Lin et al. resulting in increased evapotranspiration loss, soil moisture stress, and associated management challenges in Kansas. This, coupled with declining water levels in the Ogallala Aquifer and increasing restrictions on pumping are challenging the production of corn and other crops. Xue et al. found in their review of long-term production and corn management practices that yields and water use efficiency have increased due to advances in corn genetics and irrigation technologies, and recommended continued research to improve grain quality, crop drought tolerance, and adoption of new technologies to sustain production in the High Plains. Water use-yield relationships are important for efficient water management (Siahpoosh et al. 2012) and models such as the Kansas Water Budget (KSWB) and Decision Support System for Agrotechnology Transfer (DSSAT) Cropping System Model (CSM) are important tools to assess these relationships. Moberly et al. evaluated the predictive accuracy of the KSWB model for crop water use and grain sorghum and winter wheat productivity, grown in a range of crop sequences. They found that the Kansas Water Budget model provided a useful analytic framework for predicting water supply constraints to grain production, but poorly predicted yield response for either grain sorghum or winter wheat. Adhikari et al. used the DSSAT-CSM model to simulate the long term cotton lint yield and seasonal crop ET and found it useful for scheduling ET-based irrigation management practices in the Texas High Plains and estimating future ET for other modeling experiments. In addition to these models, groundwater models that not only capture regional hydrogeologic characteristics but also human-hydrologic-climate interactions are crucial for guiding future water management and policy planning endeavors. A conceptual modeling framework built on this premise was applied by Uddameri et al. to a current regional-scale groundwater modeling study in the Southern High Plains where the lack of groundwater production data is a major limiting factor. To identify alternative approaches to fill this critical data gap and properly parameterize the model, they evaluate the importance of surface water groundwater interactions, determine whether explicit coupling of watershed and groundwater models is warranted, and assess limitations in simulating human-aquifer interactions. The study demonstrated the utility of several simple “first-cut” analysis techniques to evaluate groundwater interactions with other interconnected systems. Golden and Guerrero evaluate the likely economic impacts associated with the implementation of LEMAs, Local Enhanced Management Areas authorized by the 2012 Kansas Legislature. Under this Kansas water law, groundwater management districts have the authority to initiate a voluntary process to develop a conservation plan meeting local goals. Results suggest that the LEMA framework of groundwater management will provide benefits to both the agricultural producer and rural communities. However, Golden and Guerrero note that LEMA adoption may only result in short-lived reductions in groundwater consumption with water saved today eventually being used and the water resource exhausted. Similarly, in 2014, the Sustainable Groundwater Management Act was enacted in California to reform groundwater management and ensure groundwater is managed sustainably. To help groundwater managers create some of the baseline measures needed to develop a groundwater sustainability plan required by this Act for medium and high priority basins, Flores Marquez et al. introduce a novel method for development of a water budget and present the implementation of this method in the Ukiah Valley Groundwater Basin. Results indicate that because the groundwater basin is not experiencing a decrease in groundwater storage or a lowering of the water table, the groundwater sustainability agency is uniquely positioned to focus on proactive maintenance of current conditions when constructing their sustainability plan. In the final paper, Reba et al. describe key research efforts in the Lower Mississippi River Basin, an internationally-important region of intensive crop production heavily reliant on the Mississippi River Valley Alluvial Aquifer for irrigation. This region too is facing aquifer depletion and exploring innovative methods to address this issue. Reba et al. investigated innovations in rice irrigation, on-farm water storage, and managed aquifer recharge as means to reduce the on-going decline of this economically and ecologically important alluvial aquifer. They found that collaborative efforts to improve rice irrigation management as part of the Rice Stewardship Partnership effectively reduced the amount of water applied on nearly 30,000 hectares. Their inventory of on-farm reservoir tailwater recovery systems showed that significant investments have been made as part of efforts and supports the potential for surface water storage in critical groundwater areas. Finally, the novel test of managed aquifer recharge described will be used as the basis for further testing in areas where large-scale surface water projects are unlikely. As this special issue demonstrates, significant efforts and advances are ongoing throughout the U.S. and globe to ensure food and water needs are met into the future. However, continued research is needed to improve irrigation efficiency, crop genetics, cropping systems, and our understanding of the climate, hydrology, water use, and policy impacts. As noted by Golden and Guerrero, adoption may only result in short-lived reductions in groundwater consumption with water saved today eventually being used and production ultimately converted to dryland. Efforts today to improve dryland production will go a long way to ensuring food for future generations. Kevin L. Wagner is the Director of the Oklahoma Water Resources Center and holds the Thomas E. Berry Professorship in Integrated Water Research and Management. He provides leadership and administration of the Center’s water programs, leads Center efforts to increase engagement with the water resources community across Oklahoma and the nation, and facilitates development of inter-disciplinary teams to address high priority water resources issues. Wagner has more than 20 years of experience in watershed assessment and planning, stakeholder engagement and conservation practice research and education. He may be contacted at [email protected].

Global sensitivity analysis (GSA) and uncertainty quantification (UQ) for groundwater modeling are challenging because of the model complexity and significant computational requirements. To reduce the massive computational cost, a cheap‐to‐evaluate surrogate model is usually constructed to approximate and replace the expensive groundwater models in the GSA and UQ. Constructing an accurate surrogate requires actual model simulations on a number of parameter samples. Thus, a robust experimental design strategy is desired to locate informative samples so as to reduce the computational cost in surrogate construction and consequently to improve the efficiency in the GSA and UQ. In this study, we develop a Taylor expansion‐based adaptive design (TEAD) that aims to build an accurate global surrogate model with a small training sample size. TEAD defines a novel hybrid score function to search informative samples, and a robust stopping criterion to terminate the sample search that guarantees the resulted approximation errors satisfy the desired accuracy. The good performance of TEAD in building global surrogate models is demonstrated in seven analytical functions with different dimensionality and complexity in comparison to two widely used experimental design methods. The application of the TEAD‐based surrogate method in two groundwater models shows that the TEAD design can effectively improve the computational efficiency of GSA and UQ for groundwater modeling.

Pumping-accelerated soft ground compaction triggers iodine enrichment in saline groundwater of coastal plains.