HydroVisions | Spring 2024

V isions

HYDROVISIONS is the official publication of the Groundwater Resources Association of California (GRA). GRA’s mailing address is 808 R Street. Suite 209, Sacramento, CA 95811. Any questions or comments concerning this publication should be directed to the newsletter editor at hydrovisions@grac.org

The Groundwater Resources Association of California is dedicated to resource management that protects and improves groundwater supply and quality through education and technical leadership.

EDITOR

Rodney Fricke hydrovisions@grac.org

EDITORIAL LAYOUT

Smith Moore & Associates

EXECUTIVE OFFICERS

PRESIDENT

Christy Kennedy

Woodard & Curran

Tel: 925-627-4122

VICE PRESIDENT

Erik Cadaret

West Yost

Tel: 530-756-5905

SECRETARY

Moises Santillan

Water Replenishment District

Tel: 562-275-4279

TREASURER

Rodney Fricke

GEI Consultants

Tel: 916-407-8539

DIVERSITY, EQUITY AND INCLUSION OFFICER

Marina Deligiannis

Stantec

Tel: 916-418-8242

IMMEDIATE PAST PRESIDENT

HISSN 2837-5696

R.T. Van Valer

ADMINISTRATIVE DIRECTOR

Amanda Rae Hall

Groundwater Resources Association of California ahall@grac.org

DIRECTORS

Jena Acos

Brownstein Hyatt Farber Schrek

Tel: 805-882-1427

Trelawney Bullis

AC Foods, Central Valley

Tel: 530-205-8387

Dave Ceppos

Sacramento State University

Tel: 916-539-0350

Elis Haddad

Haley & Aldrich

Tel: 408-529-9048

Dr. Hiroko Hort

GSI Environmental, Inc

Tel: 720-273-6364

Annalisa Kihara

State Water Resources Control Board

Tel: 916-947-7938

Yue Rong

Los Angeles Regional Water Quality Control

Tel: 213-576-6710

Abhishek Singh INTERA

Tel: 217-721-0301

Clayton Sorensen

West Yost Associates

Tel: 925-949-5817

Savannah Tjaden

Environmental Science Associates

Roohi Toosi

APEX Environmental & Water Resources

Tel: 949-491-3049

John Xiong

Haley & Aldrich, Inc.

Tel: 714-371-1800

To contact any GRA Officer or Director by email, go to www.grac.org/board-of-directors

The statements and opinions expressed in GRA’s HydroVisions and other publications are those of the authors and/or contributors, and are not necessarily those of the GRA, its Board of Directors, or its members. Further, GRA makes no claims, promises, or guarantees about the absolute accuracy, completeness, or adequacy of the contents of this publication and expressly disclaims liability for errors and omissions in the contents. No warranty of any kind, implied or expressed, or statutory, is given with respect to the contents of this publication or its references to other resources. Reference in this publication to any specific commercial products, processes, or services, or the use of any trade, firm, or corporation name is for the information and convenience of the public, and does not constitute endorsement, recommendation, or favoring by the GRA, its Board of Directors, or its members.

President's Message Page 4

Synopsis of DWR Guidance Page 6

Navigating New Waters Page 10

Predicting Subsidence Page 14

Water Witching in California Page 18

2023 CGIC Highlights Page 20

Sustainability Plan Reporting Page 23

GeoH2OMysteryPix Page 24

Parting Shot Page 26

ISSN 2837-5696

President’s MessaGe

Greetings!

Last edition, I got to welcome in the new year as President of the Groundwater Resources Association (GRA) and reflect back upon my own start and journey with GRA. Now, we look forward - and right there in front of our industry and our lives is a changing climate. And as the impacts of climate change intensify, the need for innovation in the water industry and specifically groundwater management has never been greater. But how do we innovate within our industry to create meaningful change? After recently attending ImagineH2O’s Startup Summit held in Google’s Community Space in San Francisco, a space which seethes creativity and innovation - I was inspired by the 2024 cohort developing technologies that could revolutionize how we solve water issues. Most clearly, I knew that we have some work to do in stewarding GRA over the next couple years to ‘amp up’ technology, innovation, and partnerships outside of the norm.

Most importantly, we must embrace new thinking and new approaches in technology that intersects groundwater management. One example is the predictive flooding forecasting Google Research has created using artificial intelligence (AI), which is proving extremely accurate without relying on historical data. Bonkers! Right, am I right?! Seriously, check out that link. Satellite/sensor technology (AEM, anyone?) is also advancing rapidly and is changing how we model and analyze systems. Rather than relying on outdated methods and being gatekeepers, we must be curious, embrace change, and integrate these technologies.

GRA’s Board of Directors recognizes the urgent need to strategically focus on innovation and partnerships in 2024. Our first board meeting in February set time aside to better develop a strategic initiative of innovation & partnerships which has since continued advancement and may envelop our coursework under a broader educational model. We also hosted an in-person “Future of Water” symposium exploring the tech sector’s advancements in flood prediction, digital water and AI in our industry. We ended with an impactful learning session on Tribal Ecological Knowledge and elevated environmental ethics to center stage. As a Board, we will continue to advance GRA’s programming and collaboration across sectors to drive impact in sustainable groundwater. However, we cannot drive this change alone - we need your help.

I strongly encourage all our members to get involved in leveraging the convening power of GRA to address climate impacts. Provide feedback on our educational offerings, advocacy and events. Connect us to others working at the forefront of water technology whom you don’t see in the GRA room. Consider teaching a short course yourself on an emerging topic. Most importantly, share your bold ideas for how we can revolutionize management and address climate threats with greater speed and impact.

President’s MessaGe

The challenges before us demand that we think differently and work together in new ways at GRA. I hope you will answer this call to action - our future depends on accelerating innovation across organizations and industries. Please reach out to discuss how you can contribute to this critical mission of GRA so, that together, we can achieve the vision of sustainable groundwater for all.

Author’s Note: In an attempt to increase my own innovative spark, I wrote this article from a break in my daughter’s track meet, sitting in the car, using AI. To help spark your own embracing of the future - here is how I did it: I used the free version of the Otter.ai app on my iPhone to voice record a dictation (a little under seven minutes) of what I wanted this “Letter from the President” to be themed around. Next, still on my iPhone, I used prompts in the app’s chat feature to convert my ramblings to a “Letter to the Editor” style. These steps gave me a 200-word draft. I used more prompts to refine the draft in the app such as “expand by 50 to 100 words”, and “strengthen call to action”, until I was happy with the draft. Still on my iPhone between the 100-meter dash and the 4x100-meter relay, I copied the full draft into my OneNote app where it sat because the race was back on. A few days later, I spent 20 minutes editing (adding links, specific examples and making language sound more like me) on a plane and emailing to our HydroVisions editor for review and inclusion in the spring edition. Total development time was approximately 30 minutes. How did I do, and what should I do differently next time? More importantly, are you ready to try some of these tools to create more time in your day to solve the world’s toughest water challenges with GRA? Cheers!

Christy Kennedy

GRA President and clumsy AI enthusiast

Thank you to all of our Annual Sponsors!

Roscoe Moss Company

Hydro Visions

synoPsis of dwr Guidance on GsP iMPleMentation rePortinG requireMents

by Lisa Porta & Pete Dennehy, Montgomery & Associates

Introduction/Background

The Department of Water Resources’ Sustainable Groundwater Management Office (DWR SGMO or Department) continues to provide valuable guidance to Groundwater Sustainability Agencies (GSAs) to support their Groundwater Sustainability Plan (GSP or Plan) implementation to reach groundwater sustainability in their basins by 2040/2042. In October 2023, DWR SGMO published A Guide to Annual Reports, Periodic Evaluations, and Plan Amendments to help GSAs navigate the Water Code and GSP Regulations requirements for reporting. This comprehensive guidance document is a “one-stop-shop” for all GSP implementation reporting requirements. It describes the reporting roles and responsibilities of the GSAs and the review requirements for the Department. The document is accompanied by Department answers to Frequently Asked Questions and a list of Available Resources for GSAs to use in preparing reports.

This article provides some key information contained within the document to provide an overview and distinguish between the three types of reports that GSAs must submit to DWR SGMO at various times to comply with SGMA.

Key Messages

Once a GSP is adopted and submitted, SGMA and the GSP Regulations impose requirements on GSAs to demonstrate GSP implementation to the Department and interested parties. Annual Reports, Periodic Evaluations and Plan Amendments are all methods for GSAs to demonstrate GSP implementation and progress towards sustainability. In turn, the Department conducts Periodic Reviews of approved

GSPs, Annual Reports, Periodic Evaluations, and any Plan Amendments to determine whether the GSP continues to comply with SGMA and the GSP Regulations.

Each GSA deliverable demonstrates different aspects of GSP implementation:

• Annual Report: a report documenting current groundwater conditions, data gathering and monitoring efforts, activities to fill data gaps, water year comparisons, and GSP implementation progress (due by April 1 each year) – this is a progress tracking tool

• Periodic Evaluation: an evaluation and written assessment of an approved GSP to occur at least every five years (due no later than five years after initial GSP submittal) and when a Plan is amended – this is an implementation evaluation tool.

• Plan Amendment: a revised GSP that necessitates going through the Plan adoption process and submission to the Department for review (an agency may amend their GSP at any time; a Periodic Evaluation is required with every Plan Amendment) –this is an adaptive management tool

When prepared in conjunction with a Plan Amendment, duplication should be avoided between the Periodic Evaluation and the Plan Amendment; the Periodic Evaluation in such circumstances serves primarily to justify and explain the reasons for the Plan Amendment not simply to repeat the same text and information contained in the Amendment.

For Periodic Evaluations that accompany a Plan Amendment, GSAs must ensure the Periodic Evaluation is not:

• A copy/paste of the GSP sections that were revised or amended.

• A simple: “See Section X.”

isions

The Periodic Evaluation must provide specific explanations of what was amended, why, and the effects of those amendments on the implementation of the Plan (e.g., adapting the management program, adjusting projects and management actions). GSAs are expected to provide a detailed discussion of how the recommended corrective actions were addressed for each of the Plan elements.

The Department will use Annual Reports and Periodic Evaluations submitted by the GSAs for their Periodic Review and assessment of progress made toward achieving sustainability in each basin. A Periodic Evaluation must be submitted at least every 5 years, with or without a Plan Amendment.

Plan amendments are not required per the GSP Regulations or SGMA and are to be prepared at the discretion of the GSAs and their governing boards. A Plan Amendment, when submitted, always needs to be accompanied by a Periodic Evaluation.

GSP implementation follows an adaptive management process that was initiated by the adoption of a Plan by the GSA Board and approval by the Department. The adaptive management process continues with annual reporting, monitoring

conditions, project implementation, and periodic evaluation to reach and maintain sustainability during the planning and implementation horizon (i.e., 50 years). Figure 2 provides a graphical representation of the plan implementation adaptive management approach.

Annual Reports

GSA Requirements:

GSAs are required to develop Annual Reports every water year to provide annual data submittals and track whether their Plans are being implemented in a manner that will likely achieve the sustainability goal for their respective basins. The GSP Regulations require an Annual Report to:

• Compile and transmit groundwater data collected from established monitoring networks during the previous water year.

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Figure 1. Summary of implementation Deliverables for each Basin Determination Type. Shows the deliverables and timing for which a GSA should plan, depending on the Department's review process and determination of the GSP.

Figure 2. GSP implementation Adaptive Management Approach

• Assess groundwater conditions relative to the sustainable management criteria established in the GSP.

• Summarize total water use including groundwater extraction, total surface water received, and the volume of surface water used for recharge efforts.

• Estimate annual change in groundwater storage for each principal aquifer

• Describe progress made on GSP projects, management actions, and other implementation efforts such as continued outreach and engagement. Discuss how those efforts help the basin achieve their measurable objectives and sustainability goal.

Review by Department:

The Department will confirm receipt of Annual Reports and check completeness and accuracy of information and data provided in the Annual Report and the SGMA Portal. The Department will also review the Annual Reports each year to assess progress towards sustainability. If through their review, the Department determines additional information is required, the Department will provide a written response to plan managers. The Department will also utilize the Annual Reports when it conducts the Periodic Review of Plans.

Periodic Evaluations

GSA Requirements:

SGMA requires GSAs to evaluate their basin’s GSP at least every five years and provide a written assessment to the Department. A Periodic Evaluation is an opportunity for GSAs with an approved GSP to convey progress on GSP implementation to the Department, interested parties, and the public. The Periodic Evaluation should provide the status of groundwater conditions and progress toward meeting interim milestones and measurable objectives. The Periodic Evaluation should also describe the advancement of projects and management actions over the evaluation cycle including the associated quantified cumulative benefits. The Periodic Evaluation should explain how those cumulative benefits are contributing to the basin achieving its sustainability goal and operating within its sustainable yield. Conversely, the Periodic Evaluation should describe any unforeseen challenges encountered with the development or implementation of certain projects and management actions and the outcome of responding to those challenges. The Periodic Evaluation also acts as the document where a GSA articulates whether a Plan Amendment is needed.

The following questions can help with the organization and development of the written assessment, for each GSP section, as applicable:

• What new information has been collected?

• What is the status of the components of this section? Describe any changes.

• Was there a recommended corrective action associated with this section? Explain how it was addressed.

• How have actions taken in this section informed changes in basin management?

• Is there a need to change a section of the GSP that would lead to a Plan Amendment? Which section has or will be revised in the Plan Amendment?

Review by Department:

The Department’s Periodic Review will occur at least every five years with the first Periodic Review being initiated five years after submittal of the initial approved GSP. The Periodic Review involves evaluating the Plan, Annual Reports, and Periodic Evaluations. The Periodic Review will result in the Department providing an assessment of the basin’s GSP implementation and progress towards sustainability, ultimately issuing a determination of approved, incomplete, or inadequate. It should be noted that the approval of a previously submitted GSP does not guarantee continued approval by the Department during the implementation period.

Plan Amendments

GSA Requirements:

While SGMA and the GSP Regulations do not mandate when or how a GSP is amended, it is likely that many GSPs will be amended at times. Should a GSA elect to amend its GSP, it is important to be aware of some considerations for Plan Amendments.

Elements of the GSP that may warrant a Plan Amendment if significant or material changes were made:

• Changes to the overall management of the basin, including sustainable management criteria, sustainability goal, addition or removal of management areas, or wholesale modifications to the representative monitoring sites network.

• Revisions to projects and management actions, including addition or removal of projects or management actions that could affect the projected water budget, sustainable yield, or achievement of measurable objectives, or impact the ability to mitigate overdraft.

• Modifications to the administrative management of the basin, including addition or removal of GSAs, or the addition or removal of a GSP in a multiple-GSP basin, etc.

GSAs should evaluate whether any change, revision, or modification to the GSP requires approval from governing boards or necessitates outreach and engagement with interested parties. If the GSA determines that these actions are necessary to make the desired changes or modifications, then a plan amendment may be warranted. Plan amendments must go out for public notice and comment and must be formally adopted by the governing board.

A Plan Amendment, when submitted, always needs to be accompanied by a Periodic Evaluation.

Review by Department:

The GSP Regulations establish criteria for the Department when reviewing amended GSPs. The Department will focus its review on the revised portions of the amended GSP (and as described in the accompanying Periodic Evaluation written assessment), rather than reviewing the GSP in its entirety. To expediate the review process, the Department requests that GSAs submit both a clean version and a redline strikethrough version of the amended GSP. For the redline strikethrough version, the GSAs may submit only the portions of the GSP that were revised rather than the GSP in its entirety.

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Hydro Visions

naViGatinG new waters: artificial intelliGence’s role in securinG tHe future of Groundwater

by Sydney Nye and Haseeb Khan

Groundwater management is on the verge of a pivotal shift, moving away from complete dependence on decades-old traditional models and conventions that have long dominated the field. This transition is driven by advancements in Artificial Intelligence (AI), Machine Learning (ML) and Synthetic Data Augmentation which enable approaches more scalable, sustainable, unbiased, and primed for complexity than alternative more conventional technical options.

AI is the field of creating systems that mimic tasks typically requiring near human level intelligence, such as analysis and decision-making. ML is the main applied use of AI, concentrating on creating data-driven models designed to achieve these intelligent tasks by learning patterns and relationships. The application of ML to this field opens new doors in groundwater management, enabling us to ask more complex questions and understand natural systems in ways that were not possible before. This methodology not only enhances our current understanding but also equips us to explore the intricacies of these natural systems more deeply, fostering a more nuanced and sophisticated approach towards their stewardship.

Introduction to Machine Learning in Groundwater Studies

Groundwater has long been understood as vital for agriculture, industry, and life itself. Yet, its management is fraught with challenges, compounded by climate change and increasing demand. Traditional hydrological models have served us well, offering a window to view and predict, analyze, and dissect groundwater’s parameters and impacting variables

with a degree of accuracy and precision that scientific and planning communities grew to accept and work with. Machine Learning offers a quantum-leap forward from the current paradigm, clearing the smudges off that window and in many cases, expanding it, enhancing accuracy of current approaches and providing new insights into the impact of certain variables or elucidating complicated interconnected systems. ML, with its ability to parse complex datasets and unearth patterns invisible to the naked eye, stands ready to augment our traditional approaches, offering new pathways to understand – and thereby safeguard – this resource.

Navigating the Data Deluge: A New Chapter for Hydrology

As data continues to grow both in scope and granularity, ML’s role is becoming increasingly pivotal, offering a dynamic and nuanced approach to understanding and managing groundwater—a critical step forward in an era where precision is paramount, and change is the only constant.

The digital age has ushered in an era of unprecedented data growth (see Figure 1), with the digital universe set to continue its exponential expansion. This surge is propelled by humanand machine-generated data, growing at a rate ten times faster than traditional business data (Dignan, 2017). This tidal wave of information, especially evident in hydrology through advanced sensors and the Internet of Things (IoT), presents a unique opportunity for ML to transform water resource management. As traditional static numerical models struggle to keep pace, ML is specially equipped to analyze vast and complex datasets, uncover hidden patterns, and offer insights previously out of reach. This shift not only signifies an adaptation to the increasing volume of data but marks a proactive step towards

isions

1. Summary of Data Growth from 2010-2020 with Projections from 2020-2025. Note: One zettabyte is equal to a trillion gigabytes.

Source: IDC White Paper – #US44413318 (2018, refreshed in 2020)

leveraging big data’s potential to revolutionize hydrology and sustainably manage water resources.

The rise of real-time data, as depicted in Figure 2, is reshaping the management of all dynamic systems, with groundwater management being no exception. This trend towards immediate data availability allows for the dynamic updating of predictive models, an area where ML excels. With ML’s capability to instantaneously assimilate new data, groundwater models can now adapt in real-time, enhancing decisionmaking with up-to-the-minute accuracy, and enabling proactive responses to emerging hydrological events. This evolution points to a future where ML-driven systems will likely become essential in the management and conservation of groundwater resources.

Unpacking LSTM: A Glimpse into the Future

At the heart of this new wave is the Long Short-Term Memory (LSTM) network, a type of deep learning (a branch of Machine Learning) particularly adept at processing and predicting conditions, based on sequential data (e.g., time series of rainfall or river flow). A study from a few years ago (Kratzert, 2018) showcased LSTM’s potential in modeling discharge across diverse catchments using the “Catchment Attributes for Large-Sample Studies” (CAMELS) dataset, illustrating its potential to outperform traditional hydrologic models. Essentially, LSTMs can “remember” past data points, which is crucial for predicting future events in hydrology, as they are dependent on past conditions – a subtlety captured by this ML model architecture. The research indicates that LSTMs achieved a Nash-Sutcliffe Efficiency (NSE) of 0.65 or higher in over half of the studied catchments, with an average NSE of 0.63. This performance is notably superior in catchments affected by snow and in regions with higher annual precipitation. LSTMs outperform traditional models, especially in catchments where conventional approaches struggle, demonstrating their robustness and wider applicability.

Further analyses into regional hydrological modeling reveal that LSTMs can adapt to different Hydrologic Unit Codes (HUCs), particularly excelling in areas with correlated discharge patterns among catchments. This adaptability is enhanced through fine-tuning processes, where pre-trained models are specifically adjusted to individual catchments, improving performance significantly.

LSTMs not only offer comparable accuracy to established models like the SAC-SMA + Snow-17 model but also present a novel approach to transferring knowledge across various catchments (see Figure 3). This feature potentially reduces the data requirements for individual basins, suggesting a promising avenue for applications in ungauged basins or regions with limited data availability. The insights gained from dissecting LSTM internals further mitigate the “blackbox” nature traditionally associated with data-driven models, enhancing trust and paving the way for their expanded use in hydrology and beyond.

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Figure

Figure 2. Summary of Real-Time Data as a Percent of Total Data from 2010-2020 with Projections from 2020-2025. Source: IDC White Paper – #US44413318 (2018, refreshed in 2020)

Figure 3. Boxplot of the NSE for the validation period for Kratzert’s three experiments and benchmark model (NSE capped to -1, green diamond marking the mean, orange line marking the median). Source: Kratzert (2018), Fig 14

This trust has been furthered most recently by Google’s deployment of an LSTM-based global flood forecasting system in 2024 (Nearing, 2024), which not only matched but significantly surpassed the precision and reliability of existing methods – including the existing gold standard in global flood forecasting, GloFAS version 4 – in predicting flood timings and locations. For the hydrology community, accustomed to the inherent limitations of traditional modeling, the success of Google’s LSTM application represents a compelling argument for embracing ML technologies.

Specifically, the LSTM model reduced false alarms and missed forecasts by a substantial margin, presenting a clear utility not just for flood management but also for groundwater modeling. This leap in performance highlights the broader applicability of LSTMs, suggesting their potential to revolutionize not only how we predict and manage floods but also how we monitor and manage groundwater resources with greater accuracy and confidence.

Machine Learning’s Expanding Role in Groundwater Management

Predicting Groundwater Levels

Sadegh et al. (2022) demonstrated the capabilities of another ML type: Artificial Neural Networks (ANNs), which accurately forecasts groundwater levels. By “learning” from vast datasets, ANNs can discern complex patterns that traditional models might miss, enabling more precise predictions of groundwater fluctuations. This technique, similar to the way a human brain processes information, adapts based on the input data, improving its predictive capability over time. The review emphasizes that the performance of these models hinges more on the quality of input data than on the algorithm itself. It reveals that about 10 to 12 years of data are generally required to develop a reliable model with a monthly temporal resolution. Feed-forward ANNs are highlighted as the most utilized, most dynamic, and potentially most accurate ML model architecture for groundwater level forecasting, underscoring the pivotal role of data-driven approaches in enhancing groundwater management strategies.

This analysis underscores the increasing importance of ML, particularly through the use of ANNs, in groundwater studies. It signals a shift towards more advanced and data-reliant ML modeling techniques for predicting groundwater levels, emphasizing the critical role of quality data in enhancing model accuracy and reliability.

Assessing Water Quality

Water quality assessment is another area where ML shines, employing algorithms to classify water into various quality brackets for drinking and irrigation. Alsalem et al. (2023) explored the application of ensemble and time-series ML methods in classifying groundwater quality. These advanced ML techniques orchestrate a synergistic approach by amalgamating multiple models, analogous to harnessing the collective wisdom of a panel of experts, thereby enhancing prediction accuracy and reliability beyond what single-model approaches can offer.

The study illuminates how these methods adeptly handle the multiclassification of groundwater quality into categories essential for drinking and irrigation, setting a new benchmark in the field. Specifically, the Random Forest (RF) algorithm within this ensemble framework emerged as a standout, delivering unparalleled precision, recall, and accuracy metrics of approximately 98%, 89%, and 95% respectively, across diverse water quality levels. This performance underscores the effectiveness of ensemble ML in navigating the complex, nonlinear relationships inherent in groundwater quality data, outpacing traditional hydrologic models and even other ML approaches in predictive capability. ML offers a nuanced approach to more accurately distinguishing between various water quality levels, providing vital data for resource management and public health, and marking a progressive shift towards sophisticated, data-driven approaches in groundwater studies.

Capturing Ecosystem Interactions

The impact of groundwater levels on ecosystems can also be explored through these methods. Rohde et al. (2021) applied Random Forest models, an ensemble learning method previously highlighted, to assess how groundwater levels affect California’s ecosystems. This method efficiently navigates the complex interactions within ecological data, offering insights traditional approaches may overlook. By analyzing data from over 95,135 groundwater-dependent ecosystems, the study reveals a significant decline in groundwater levels across 44% of these ecosystems from 1985 to 2019, a trend not easily captured by conventional models. This decline, notably sharper in the last two decades, underscores the utility of ML in identifying critical shifts in water availability and its consequential effects on local biomes. Thus, Random Forest models provide a compelling tool for deciphering the nuanced ecological consequences of groundwater fluctuations, reinforcing the role of advanced ML techniques in informing sustainable ecosystem management strategies.

Overcoming Challenges and Looking Ahead

Integrating ML into groundwater management encompasses navigating challenges like data sparsity and the need to harmonize diverse data sources. Expertise in ML engineering plays a critical role, not just in mitigating these challenges but also in the foundational aspects of scoping, designing, engineering, developing, fine-tuning, training, debugging, customizing, deploying, and monitoring ML models to deliver actionable and reliable results. This effort ensures that ML applications in specialized fields like hydrology are effective, sustainable, and tailored to specific needs. Amidst the public interest stirred by tools like OpenAI’s “ChatGPT” and Generative AI as a whole—which differ significantly in purpose and design from the ML techniques focused on making real predictions—misconceptions about ML’s applications in specialized fields like hydrology may arise. Clear communication is essential to dispel these misunderstandings. Moreover, integrating ML with traditional hydrological models presents a promising frontier. Such a hybrid approach leverages ML to enhance predictive accuracy and gain insights beyond the reach of conventional methods alone, demonstrating that ML can significantly amplify traditional hydrology to solve complex environmental challenges.

Conclusion

As we venture into a new era of hydrology, the amalgamation of ML with groundwater management is setting the stage for groundbreaking advancements. This fusion is poised to elevate traditional models, infusing them with the analytical prowess of ML to unlock sustainable, innovative solutions for groundwater management. It’s a dynamic shift that not only preserves the essence of the human element but significantly amplifies it.

Central to this transformation is the emergence of a critical role: the ML Engineer with Domain Expertise. This unique blend of skills is becoming increasingly indispensable, marrying the intricate, specialized knowledge of groundwater systems with the technical acumen of AI. The significance of this role cannot be overstated—it represents a bridge between the nuanced challenges inherent in groundwater management and the sophisticated solutions offered by ML. Such professionals are vital for the accurate interpretation of complex datasets, turning vast streams of data into actionable insights that drive forward sustainable practices and innovation.

The broader application of AI in groundwater management promises to revolutionize how we approach this precious resource. With the capabilities of ML, we can anticipate more accurate predictions of groundwater levels, enhanced water quality assessments, and a deeper understanding of ecosystem interactions. AI empowers us to navigate the complexities of groundwater systems with a newfound clarity, ensuring that management strategies are not only reactive but proactive, aligning closely with the principles of sustainability and resilience.

As we embrace AI and ML in the discipline of groundwater management, we stand on the threshold of a future where our approaches to this critical resource are defined by greater precision, sustainability, and innovation. The role of the ML Engineer with Domain Expertise is central to this transition, embodying the synergy of technical prowess and specialized knowledge that will drive the field forward. In this new era, AI is not just a tool but a transformative force, reshaping the field of groundwater management for generations to come.

References

• Alsalem, K. O., et al. (2023). “Groundwater Management Based on Time Series and Ensembles of Machine Learning.” Processes. MDPI

• Dignan, L. et al. (2017). “The Exponential Growth of Data.” InsideBigData

• Kratzert, F., et al. (2018). “Toward improved predictions in ungauged basins: Exploiting the power of machine learning.” Water Resources Research. HESS

• Nearing, G., et al. (2024). “ Global prediction of extreme floods in ungauged watersheds.” Nature

• Reinsel, D., et al. (2017). “The Digitization of the World from Edge to Core.” IDC White Paper, sponsored by Seagate. Seagate

• Rohde, M. M., et al. (2021). “A Machine Learning Approach to Predict Groundwater Levels in California Reveals Ecosystems at Risk.” Frontiers in Earth Science. Frontiers

• Sadegh, M., et al. (2022). “Groundwater Level Modeling with Machine Learning: A Systematic Review and MetaAnalysis.” Water. MDPI

Hydro Visions

Models: tools for estiMatinG and PredictinG subsidence

by Vivek Bedekar1, Tyler Hatch2, Jonathan A. Traum3 , Gus Tolley4, Abhishek Singh2

, and

Claudia C. Faunt

3

Land subsidence5 as a result of groundwater extraction is an important concern in several parts of California, particularly the Central Valley, where excessive pumping of groundwater is leading to depressurization and compaction of clays (Faunt, 2009). Subsidence in response to this aquifersystem compaction may cause damage to infrastructure such as roads, pipelines, and canals. Previous articles in this series (Hatch and others, 2023; Neely and Hatch, 2024) have described the physical processes and methods used to quantify subsidence after it has occurred. This third article explores approaches, with a focus on models, that can be used to quantify and predict the magnitude and extent of subsidence. These models can be used for management of groundwater resources to reduce future subsidence and associated negative effects. These models also provide tools to help achieve effective groundwater management under the Sustainable Groundwater Management Act (SGMA) legislation (SGMA, 2014).

Models are simplified mathematical representations of physical properties and processes that incorporate aquifersystem characteristics, such as the presence of clay beds and groundwater pumping. A well-calibrated model becomes a diagnostic tool to estimate historical subsidence, predict future subsidence, analyze the effects of projected future conditions, and evaluate a variety of groundwater management strategies. Incorporating observed and estimated subsidence into a groundwater flow model can help constrain parameter value estimates during model calibration and subsequently improve subsidence predictions. This article provides a brief overview of the available methods, simulation software6, and model applications.

Process and Mechanics

The physical mechanics of sediment compaction were described by Terzaghi (1925) and extended to aquifer-system compaction by Jacob (1940). Compaction occurs when porewater pressure (that counteracts the overburden pressure) is reduced due to lowering of groundwater levels in response to a combination of increased groundwater pumping and reduced recharge, causing aquifer-system sediments to compress or rearrange into a more densely packed configuration. A majority of compaction occurs in clay beds, which respond at short and long timescales to changes in surrounding hydraulic pressure. Short-term responses consist of pore pressure changes in, and resultant water drainage from, the clays that do not lead to structural changes or rearrangement of the clay bed (elastic compaction). However, if the clay pore pressure lowers beyond a threshold (pre-consolidation pressure – typically the lowest pressure in the clay to date), water drained from the pores leads to irreversible structural changes (inelastic compaction) and permanent storage loss in the clay bed. Inelastic changes in clays typically occur over longer time scales of years to decades, leading to the phenomenon of “residual subsidence.” The delay in the inelastic response of clays is governed by the hydraulic conductivity, inelastic specific storage, and the thickness of the clay beds undergoing deformation. The most widely used method to compute this compaction process assumes that only one-dimensional (1D) vertical deformation occurs within clay beds (Leake and Prudic, 1991; Hoffmann and others, 2003; Leake and Galloway, 2007; IWFM Version 4, 2014; Boyce and others, 2020; Hughes and others, 2022; IWFM-2015, 2023). This approach simplifies the mathematical calculations, enabling the implementation of subsidence processes in simulation software (Figure 1). An alternative approach is available in

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theory that uses a three-dimensional (3D) compaction model (poroelasticity model) and considers horizontal deformation (Zhu and others, 2020). However, the stress-strain constitutive relationships are complex and difficult to represent in models.

Simulation software

A variety of subsidence simulation approaches exist, from relatively simple 1D analytical solutions to 3D numerical models. Simple 1D models have been developed since the 1970s (Helm, 1978), and modern 1D models can be used to simulate the interaction between groundwater levels and elastic and inelastic (including delayed) responses in clay beds at multiple depths (Lees and others, 2022). These 1D simulation approaches can be implemented using custom scripts (Lees, 2022) or even a spreadsheet. The IWFM (2023) and MODFLOW (Harbaugh, 2005; Langevin and others, 2017; Boyce and others, 2020) families of simulation software include various packages to simulate subsidence.

These models simulate the groundwater flow system in three dimensions but simulate vertical (1D) compaction of clays at different depths coupled with the groundwater flow equation. The IWFM and MODFLOW subsidence packages have varying capabilities to handle different aspects of the physical processes associated with subsidence. Earlier versions of the IWFM and MODFLOW subsidence packages only simulated instantaneous compaction. Later versions include time-delayed compaction and other more advanced features. Table 1 summarizes the capabilities of subsidence packages in various versions of IWFM and MODFLOW simulation software.

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Figure 1. Subsidence Processes and Model Representation (adapted from Hoffman and others, 2003, and Galloway and others, 1999)

Package Name

Interbed Storage (IBS)

Subsidence and Aquifer-System Compaction (SUB)

Subsidence and Aquifer-System Compaction Package for Water-Table Aquifers (SUB-WT)

Subsidence and Aquifer-system compaction (SUB-CR)

Subsidence and Aquifer-System Compaction (SUB2)

Skeletal storage, compaction, and subsidence (CSUB)

Subsidence Component Version 4.0 File

Subsidence Component Version 5.0 File

Software

Version where package is first available Notes

MODFLOW96

MODFLOW2000

MODFLOW2005

Simulation of instantaneous storage change. Several versions of IBS exist

Adds simulation of time-delayed storage change

Adds simulation of varying geostatic stress as a function of the water table

Reference

Leake and Prudic, 1991

Hoffmann and others, 2003

Leake and Galloway, 2007

MODFLOW2005 Considers additional geo-mechanical processes Kooi and Erkens, 2020

MODFLOWOWHM

Same features as SUB. Adds sublink option. More comprehensive output options. Schmid and others, 2014; Boyce and others, 2020

MODFLOW 6 Combines the delay features in SUB with the water table features in SUB-WT. Added option to separate coarse sediment elastic compaction and to separate water compressibility.

IWFM version 4.0

IWFM 2015

Simulation of instantaneous storage change

Adds Simulation of time-delayed storage change

Central Valley Regional Model Applications

The Central Valley Groundwater-Surface Water Simulation Model (C2VSim) (C2VSimFG, 2021) and the Central Valley Hydrologic Model (CVHM) (Faunt, 2009) are regional models developed to simulate groundwater conditions and aquifersystem responses to groundwater availability and climate variability in California’s Central Valley. C2VSim is developed and maintained by the California Department of Water Resources (DWR) and uses the IWFM simulation software. CVHM is developed and maintained by U.S. Geological Survey (USGS) and uses MODFLOW One-Water Hydrologic Flow Model (OWHM). C2VSim was initially developed to account for the groundwater gains and losses in the State Water Project surface water operations model (CalSim and its predecessor models (CalSim 3, 2021)). C2VSimFG is a refined version of C2VSim that was released in 2020 with an update in 2021, and its purpose has been expanded to improve understanding of water resources in the Central Valley and to provide an analysis tool that can be used for planning purposes. CVHM was originally released in 2009 and was developed to improve understanding of the groundwater availability in the Central Valley. Over time, C2VSim and CVHM have evolved to provide tools for water managers in

Hughes and others, 2022

IWFM Version 4, 2014

IWFM-2015, 2023

regional planning studies, particularly to support groundwater sustainability planning under SGMA.

C2VSimFG and CVHM simulate major hydrologic processes including land-use-based demands for estimating pumping and recharge, surface water and groundwater interaction, and subsidence. Digital subsidence datasets used to calibrate the CVHM and C2VSimFG are publicly available in a USGS data release (Faunt and others, 2022). These datasets include data from extensometers, continuous Global Positioning Systems (GPS), InSAR, and leveling survey data. More information on each of these data types is available in the previous article in this series discussing subsidence observation data (Neely and Hatch, 2024). Future versions of C2VSimFG are anticipated to include time-delayed storage changes in clay beds and inelastic and elastic storage properties.

Summary/Conclusions

The physical processes underlying subsidence are understood and have been incorporated into simulation software that can be used to characterize and predict subsidence. Publicly available simulation software like IWFM and MODFLOW, and regional applications of these software in the form of C2VSim and CVHM (and their subsequent releases) are

tools used to simulate subsidence in California’s Central Valley. InSAR and continuous GPS datasets are increasingly becoming available across California, and older extensometer data and leveling surveys are now readily available (Faunt and others, 2022). More refined basin-scale models are being developed to better represent groundwater conditions and operations and subsidence; and support decision-making and groundwater management. Future articles in this series are planned to present basin-specific case studies, demonstrating site-specific applications and the use of modeling tools and data to better understand and address the challenging issue of subsidence.

References

1. S.S. Papadopulos & Associates, Inc.

2. INTERA Incorporated.

3. USGS California Water Science Center.

4. Daniel B. Stephens & Associates, Inc.

5. Referred to as just “subsidence” in this article.

6. Sometimes called “model codes” but called “simulation software” in this article.

*Any use of trade, firm, or product names in this article is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Boyce, S.E., Hanson, R.T., Ferguson, I., Schmid, W., Henson, W., Reimann, T., Mehl, S.M., and Earll, M.M., 2020, One-Water Hydrologic Flow Model: A MODFLOW based conjunctive-use simulation software: U.S. Geological Survey Techniques and Methods 6–A60, 435 p., https://doi.org/10.3133/tm6A60

California Central Valley Groundwater-Surface Water Simulation Model–Fine Grid (C2VSimFG) (ver. 1.01): California Department of Water Resources web page, https://data.cnra.ca.gov/dataset/c2vsimfg

CalSim 3, 2021, California Department of Water Resources web page https://water.ca.gov/Library/Modeling-and-Analysis/Central-Valleymodels-and-tools/CalSim-3

Faunt, C.C. , ed., 2009, Groundwater availability of the Central Valley aquifer, California: U.S. Geological Survey Professional Paper 1766, 225 p., https://doi.org/10.3133/pp1766.

Faunt, C.C., Stamos-Pfeiffer, C.L., Brandt, J.T., Sneed, M., and Boyce, S.E., 2022, Central Valley Hydrologic Model version 2 (CVHM2): Observation data (groundwater level, streamflow, subsidence) from 1916 to 2018 (ver. 2.1, September 2023): U.S. Geological Survey data release, https://doi.org/10.5066/P980EHWV.

Galloway, D.L., Jones, D.R., and Ingebritsen, S.E., 1999, Land subsidence in the United States: U.S. Geological Survey Circular 1182, 175 p., https://doi.org/10.3133/cir1182

Harbaugh, A.W., 2005, MODFLOW-2005, the U.S. Geological Survey modular ground-water model -- the Ground-Water Flow Process: U.S. Geological Survey Techniques and Methods 6-A16, variously paged, https://doi.org/10.3133/tm6A16

Hatch, T., Neely, W., Bedekar, V., and Tolley, G., 2023, California’s sinking feeling: An introduction to subsidence, 2023, in HydroVisions, v. 33 (Fall 2023): Groundwater Resources Association of California, p. 10–12, https://issuu.com/hydrovisions/docs/2023_hydrovisions_-_fall. Helm, D.C., 1978, Field verification of a one-dimensional mathematical model for transient compaction and expansion of a confined aquifer system, Verification of Mathematical and Physical Models in Hydraulic Engineering, in Proceedings 26th Annual Hydraulics Division Specialty Conference: American Society of Civil Engineers, p. 189–196. Hoffmann, J., Leake, S.A., Galloway, D.L., and Wilson, A.M., 2003, MODFLOW-2000 Ground-Water Model–User Guide to the Subsidence and Aquifer-System Compaction (SUB) Package: U.S. Geological Survey Open-File Report 03–233 (ver. 1.1.1), 44 p., https://pubs.usgs.gov/of/2003/ofr03-233/.

Hughes, J.D., Leake, S.A., Galloway, D.L., and White, J.T., 2022, Documentation for the Skeletal Storage, Compaction, and Subsidence (CSUB) Package of MODFLOW 6: U.S. Geological Survey Techniques and Methods, book 6, chap. A62, 57 p., https://doi.org/10.3133/tm6A62

IWFM [Integrated Water Flow Model] Version 4, 2014: California Department of Water Resources web page, https://data.cnra.ca.gov/dataset/iwfm-version-4-0-331.

IWFM: Integrated Water Flow Model, 2023: California Department of Water Resources web page, https://water.ca.gov/Library/Modeling-andAnalysis/Modeling-Platforms/Integrated-Water-Flow-Model

IWFM-2015, 2023: California Department of Water Resources web page, https://data.cnra.ca.gov/dataset/iwfm-integrated-water-flow-model/ resource/311462d8-6cb5-4259-bd2c-c1e36a5475be

Jacob, C.E., 1940, On the flow of water in an elastic artesian aquifer: American Geophysical Union Transactions, v. 2, p. 674–686, https://doi.org/10.1029/TR021i002p00574

Kooi, H. and Erkens, G., 2020, Creep consolidation in land subsidence modelling; integrating geotechnical and hydrological approaches in a new MODFLOW package (SUB-CR): Proc. IAHS, v. 382, p. 499–503, https://doi.org/10.5194/piahs-382-499-2020.

Langevin, C.D., Hughes, J.D., Banta, E.R., Niswonger, R.G., Panday, S., and Provost, A.M., 2017, Documentation for the MODFLOW 6 Groundwater Flow (GWF) Model: U.S. Geological Survey Techniques and Methods, book 6, chap. A55, 197 p., https://doi.org/10.3133/tm6A55.

Leake, S.A., and Galloway, D.L., 2007, MODFLOW Ground-water model—User guide to the Subsidence and Aquifer-System Compaction Package (SUB-WT) for Water-Table Aquifers: U.S. Geological Survey Techniques and Methods, book 6, Chap. A23, 42 p., https://doi.org/10.3133/tm6A23.

Leake, S.A., and Prudic, D.E., 1991, Documentation of a computer program to simulate aquifer-system compaction using the modular finite-difference ground-water flow model: U.S. Geological Survey Techniques of Water-Resources Investigations, book 6, chap. A2, 68 p., https://doi.org/10.3133/twri06A2.

Lees, M., 2022, Compaction Model Documentation: Zenodo web page, https://zenodo.org/records/6081094.

Lees, M., Knight, R., and Smith, R., 2022, Development and application of a 1D compaction model to understand 65 years of subsidence in the San Joaquin Valley: Water Resources Research, v. 58, no. 6, article e2021WR031390, https://doi.org/10.1029/2021WR031390

Neely, W., and Hatch, T., 2024, Subsidence data: Techniques, availability, and interpretation, in HydroVisions, v. 34 (Winter 2024): Groundwater Resources Association of California, p. 10–12, https://issuu.com/ hydrovisions/docs/2024_hydrovisions_-_winter_-_issuu

Schmid, W., Hanson, R.T, Leake, S.A., Hughes, J.D., and Niswonger, R.G., 2014, Feedback of land subsidence on the movement and conjunctive use of water resources: Environmental Modelling & Software, v. 62, p. 253–270, https://doi.org/10.1016/j.envsoft.2014.08.006 Sustainable Groundwater Management Act (SGMA), 2014: California Department of Water Resources web page, https://water.ca.gov/ programs/groundwater-management/sgma-groundwater-management Terzaghi, K., 1925, Principles of soil mechanics, IV—Settlement and consolidation of clay: Engineering News-Record, v. 95, no. 3, p. 874–878. Zhu, L., Franceschini, A., Gong, H., Ferronato, M., Dai, Z., Ke, Y., Pan, Y., Li, X. Wang, R., and Teatini, P., 2020, The 3‐D facies and geomechanical modeling of land subsidence in the Chaobai Plain, Beijing: Water Resources Research, v. 54, no. 3, article e2019WR027026, https://doi.org/10.1029/2019WR027026

Hydro Visions

tHe sixtH sense: water witcHinG in california

by Todd Jarvis (todd.jarvis@oregonstate.edu)

The competition for hydrogeologists and groundwater engineers is getting stronger when your competitor makes it into the Wall Street Journal (WSJ) and New York Times (NYT). In a 2007 article of the WSJ “In Race to Find Water, It’s Science vs. ‘Witchers’”, Rob Thompson, a California dowser, is profiled; charged $200 an hour, plus $10 for each gallon per minute (gpm) produced in wells he has located and sometimes made $7,500 in a day’s work! Rob Thompson again made front page news in the 2021 NYT article “Two Rods and a ‘Sixth Sense’: In Drought, Water Witches are Swamped”, targeting a well location 750 feet deep and feeling it would make 50 to 60 gallons per minute. How many hydrogeologists can boast being front page news in major media - twice - over a period of 15 years?

Global Practice - Local Heroes

And some California dowsers are skilled multi-taskers to locate oil as “doodlebuggers”. Californians have a rich history in water dowsing and doodlebugging. “The Dowsers of San Diego” were profiled in an article, dated November 23, 1977, in the San Diego Reader where they reported “The practice certainly had reached San Diego by 1887, when the San Diego Union reported the “witched” location of an abundant supply of good water at sixty-one feet below the ground surface at Ocean Beach.

Water Witching, U.S.A. was written by cognitive psychologist Ray Hyman and anthropologist Evan Vogt while they were Research Fellows at Stanford University in the late 1950s. They showed that nearly every tool imaginable has been used to “divine” water in California; from pitchforks, car keys hung as a pendulum from bibles, pliers from a toolbox, and the classic “forked” stick, to custom-built devices to find water, oil and gold.

Figure 1. A dowser at work, from Pierre le Brun, Histoire critique des pratiques superstitieuses, (Jean-Frederic Bernard, 1733–1736). Public domain.

Figure 2. Industry sticker from author’s collection. Image used by permission from Baker-Hughes.

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Dowsing, water witching, and “questing” are a global practice despite considerable skepticism. Dowsing confronts the professional hydrogeologist with the paradoxes of dealing with faith-based ideologies and science-based methods,intersecting in the real world. According to the 2,000-member strong American Society of Dowsers located in Danville, Vermont - the dowsing capital of the world, California has the largest number of active chapters:

• Northern California - Redding

• Gold Country - Oroville

• Golden Gate - Corte Madera - near San Rafael

• San Jose

• Santa Cruz

• Sierra - Sacramento

• San Diego - (active in 1970s, currently inactive)

Perhaps the most famous dowser in California is “Winemaker and Water Witch Extraordinaire” Marc Mondavi. The December 30, 2012 edition of the SF Gate “A Mondavi branches out to water witching”, reported the successes of Mondavi locating wells in the Napa region. Apparently Mondavi used to offer his services as a water-witch for free, but currently charges $10 per gpm for pumped discharge like Rob Thompson. For example, if the site Mondavi selected produced 50 gpm, he charged $500. Mondavi also launched The Divining Rod varietals of wines to celebrate his skill as a dowser with the tagline “More than natural, supernatural”.

Fact, Folklore, or Freedom of Speech?

So who is right – the hydrogeologists or the water witches? “Finding” groundwater is considered by some to be a gift endowed to those with powers of magical divination. In “ The Complete Guide to Dowsing”, Applegate (2002) indicates dowsing is a learned skill.

Tension between the US Geological Survey (USGS) and dowsers dates back to 1917 with the publication of Water Supply Paper 416, which labeled dowsing a “curious supersition”. Christopher Bird’s (1993) remarkable treatise “ The Divining Hand” chronicles the 10-year debate between

the American Society of Dowsers and the USGS, resulting in the USGS releasing a public information circular on the veracity of the practice in 1977. Likewise, the National Ground Water Association developed a position paper on dowsing in 1989. In the 2021 NYT article, Timothy Parker, a Sacramento-based groundwater management consultant and hydrogeologist (and long-time GRA member), indicated “Hydrogeologists use a combination of satellite imagery, geology, drilling data, geophysical instruments and other hydrologic tools to assess water sources...Compared to dowsing, which is a person with a stick.”

The question of water witches offering their services as “professionals” lead the California Board of Geologists and Geophysicists to place a permanent injunction against a water witch in 2004. Later, the California Board indicated that water witchers are protected by the First Amendment of the US Constitution regarding free speech and the state can do little to protect consumers who hire witchers.

Criticize or Cooperate?

It is easy for groundwater hydrologists to be dismissive of dowsing. In 1999, the National Driller’s Journal called water dowsing “bad news” for groundwater, yet offered that “Obviously it is an issue we must be cognizant of to be effective in our business, and to be better communicators with dowsers and our clients”. Frank Chapelle (2000) estimated that approximately 5,000 hydrologists and 60,000 dowsers are practicing in the US in his book The Hidden Sea. With these numbers, coupled with the long history of practice predating modern day hydrogeology, hydrogeologists and groundwater engineers have no choice but to work with dowsers.

“It leaves me hot,” he said. “Just like if you short a battery.”

California Dowser Larry Bird, 2021

“You have it or don’t”

California Water Witch Marc Mondavi, 2012

“You can’t find water if you’re thirsty”

California Dowser Rob Thompson, 2007

Hydro Visions

HiGHliGHts froM tHe 2023 conteMPorary

Groundwater issues council worksHoP

by Abhishek

Singh, INTERA; Erik Cadaret, Yolo County Flood Control & Water Conservation District; Thomas Harter, UC Davis; Vicki Kretsinger, Luhdorff & Scalmanini; Tim Parker, Parker Groundwater; Dave Ceppos, California State University

Every year since 2011, GRA’s Contemporary Groundwater Issues Council (CGIC1) has brought together the leading voices from California groundwater to discuss the most pressing policy, technical, regulatory, and stakeholder issues related to California groundwater and water resources. The CGIC provides a forum for these voices to discuss key groundwater issues in a candid and transparent platform, providing GRA direction on how to best serve the needs of the state’s groundwater stakeholders through events, training, and education material. The backdrop of the thirteenth CGIC workshop, held at UC Davis on October 27, 2023, was the climatic whiplash California has been experiencing, with the historic drought of 2020 – 2022 being followed by record rain and flooding in the winter of 2023. Moreover, 2023 was also significant as the California Department of Water Resources (DWR) made final determinations on several groundwater sustainability plans from critically-overdrafted groundwater basins2, finding a majority acceptable but deeming six inadequate (and potentially subject to State intervention). In this setting, groundwater leaders and practitioners from across California came together to share their vision and brainstorm on “The Future of California Water Management, Managed Aquifer Recharge, and Water Infrastructure in the Face of Climate Uncertainty.” The overarching themes of the workshop included:

• Climate Change Evaluation and Adaption Management

• Extreme Wet and Dry Events

• Flood Control and Adaption Strategies to Support Recharge across California

Workshop participants included over 30 executives and leaders from State agencies, water districts, water management entities, groundwater sustainability agencies, non-profit organizations (NGO), academia, research laboratories, and consulting firms from across the state. Several GRA Board and Executive Team Members also participated in the event. The full-day workshop was split into two sessions: a moderated panel followed by a roundtable discussion during the morning, and three breakout sessions focusing on key topics and themes during the afternoon.

The morning panel brought together diverse perspectives from State and local agencies – Mr. Paul Gosselin (Deputy Director, Sustainable Groundwater Management, DWR) and Mr. Sam Boland-Brien (Supervising Engineer, Division of Water Rights, State Water Resources Control Board) represented State and regulatory agencies; Dr. Helen Dahlke (Professor in Integrated Hydrologic Sciences, University of California, Davis) brought in the academic, scientific, and technical perspectives; Mr. Soren Nelson (State Relations Advocate, Association of California Water Agencies) and Mr. Matt Hurley (General Manager, McMullin Area Groundwater Sustainability Agency) expressed the viewpoints of water supply and management agencies; and Mr. Chris Shutes (Executive Director, California Sportfishing Protection Alliance) brought to fore, the voice of environmental stakeholders. The panel was deftly moderated by Dave Ceppos (GRA Board Member and Director of the Consensus and Collaboration Program, California State University, Sacramento), who posed several pointed and pertinent questions to the panelists. The panel dug deep into how State and local agencies are responding to the weather extremes that California is experiencing and how the state can move towards a more sustainable, equitable, and efficient water management framework.

isions

The panel began by acknowledging that surface storage (on average) only provides two years’ worth of water supply for the State of California, hence managed aquifer recharge (MAR) and “FloodMAR3” are key to developing more resilient longterm water supplies. With climate change leading to higher temperatures, aridification, earlier snowmelt, and extremes in dry and wet conditions, capture and recharge of excess water (when available) into aquifers can augment storage in surface reservoirs and snowpack. However, the panel also recognized that recharge alone cannot dig groundwater basins in overdraft out of their hole; demand reduction needs to be an essential (if not primary) step toward reaching groundwater sustainability. The panel highlighted the fact that groundwater sustainability was essential to preserving multi-generational farming in the Central Valley, as continued overdraft, deepening groundwater levels, and subsidence may eventually lead to the multi-generational farms going out of business.

The focus of the panel shifted to the technical and regulatory aspects of MAR and FloodMAR. The discussion revolved around “Forecast Informed Reservoir Operations” (FIRO), wherein advanced weather and streamflow monitoring and forecasts are used to optimize surface reservoir operations to yield the maximum benefit across multiple objectivesflood prevention, water supply, and groundwater recharge. FIRO is making great strides in California, with promising results in Sonoma and Orange County basins. However, to see the full benefits of FIRO, regulatory changes need to be made at the federal level wherein the US Army Corps of Engineers (USACE) can allow for reservoirs to be operated for multi-benefit criteria (beyond flood control considerations). Moreover, FIRO needs to be linked with MAR and FloodMAR to maximize the benefit of groundwater recharge. The panel recognized significant data gaps, uncertainties, and regulatory hurdles when it comes to FIRO, MAR, and FloodMAR at the statewide level. More work needs to be done to understand big-picture questions such as: “What are the volumes, locations, and timing of water available for MAR and FloodMAR at statewide and basin scale?”; “Where can this water be recharged and stored underground?”; “How much water can be captured and diverted (if any) without impacting in-stream and downstream water uses, including

environmental impacts to aquatic species?”; “How do we distinguish between flood waters and normal flows in rivers and tributaries?”. Additional monitoring and data collection are needed at the statewide scale to answer these questions and develop a better understanding of the opportunities and solutions available.

As alluded to above, the panel also discussed the importance of considering all beneficial uses when evaluating recharge solutions. In particular, environmental water needs have to be balanced with urban and agricultural consumptive use. The point was made that ecosystems depend on more than just the volume of flows; the timing, temperature, and quality of surface water flows are also critical factors. Hence, practical and implementable “rules of river” need to be considered with consumptive use, recharge, and flood control criteria. Absent such “rules”, support from the environmental advocacy community may not be achievable for some MAR and FloodMAR approaches.

Several of these issues have implications for water rights and water permitting in the State. During the record high flows and flooding of 2023, Executive Orders N-4-23 and N-7-234 allowed for recharge under emergency flood conditions without MAR permit (with water quality protections). During the historic floods, DWR had to deploy a team that made weekly calls to downstream operators to try and optimize what floodwaters were diverted and captured. The panel agreed that while 2023 offered some valuable lessons learned, the State needs to move beyond executive orders and interim measures to a more holistic and integrated water rights and permitting framework. While the State has a well-established surface water rights system, improvements can be made in monitoring and implementation. Moreover, surface water rights have to be connected to subsurface storage, so aquifers may be operated the same way as surface reservoirs. This topic, in turn, prompted additional discussion about the current water rights and permitting framework and whether changes might be needed to streamline MAR and FloodMAR projects.

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The panel agreed that local MAR and FloodMAR solutions are only the first step. Eventually, California has to move towards more regional and integrated water banking solutions that will be necessary to link water supplies in one basin with demands in another. Opportunities are rife in the Central Valley, where sufficient aquifer storage space exists and can be used to develop regional water banks (once the basins have been brought out of overdraft conditions). Ultimately, these local and regional solutions will require funding. State and private funding will be key to making the investments the state needs to move towards more resilient water management strategies, especially at the regional or statewide scale.

The afternoon session consisted of parallel breakout groups centered around three topics: Recharge Infrastructure and Financing; Aquifer Recharge Regulatory and Statutory Factors; and Climate Change and Watershed Planning. Each group discussed examples and case-studies from across the state, along with lessons learned, challenges, and opportunities. The breakout groups highlighted several of the points made during the panel: the need to use groundwater storage to “equalize” the climate extremes; the advantage of integrating surface reservoir and aquifer storage operations; the importance of revamping the water rights framework in the state to support MAR and FloodMAR; the challenge of maintaining environmental flows (along with necessary temperature, water quality, and seasonality of flows for habitat needs) while facilitating diversions, recharge, and storage of floodwaters; and the need for better data, monitoring, and

forecasting tools. The groups emphasized that groundwater sustainability must balance demand management through land use change, with bold investments in MAR and FloodMAR to maximize aquifer storage and beneficial use of surface water when available. This effort will need to be supported by a more streamlined “21st-century” water rights and permitting framework that allows everyone to be at the table with fair and transparent monitoring and accounting.

As stated above, a foundational purpose of the CGIC is to parlay participants’ insights into actionable steps GRA can and will take in current and subsequent years. In this context and as informed by the CGIC outcomes above, GRA hopes to further initiatives by educating members and affected stakeholders about groundwater sustainability, demand management, and MAR/FloodMAR. In particular, GRA can provide forums and platforms to discuss the technical, legal, and regulatory aspects of MAR/FloodMAR and its linkage with water rights for all beneficial users.

1. https://www.grac.org/contemporary-groundwater-issuescouncil/

2. https://www.waterboards.ca.gov/sgma/groundwater_ basins/

3. https://water.ca.gov/programs/all-programs/flood-mar

4. https://www.waterboards.ca.gov/waterrights/water_ issues/programs/groundwater-recharge/

Groundwater sustainability Plan

rePortinG Process and requireMents

DWR’s Sustainable Groundwater Management Office staff presented on the groundwater sustainability plan reporting process, annual reporting process, and the expectations for how these various documents, required by SGMA regulations, are submitted by GSAs to DWR. Staff also provided information on the periodic update guidance document released in the fall of 2023, as well as other regulatory reporting process items.

• Groundwater Awareness Week Webinar recording: Groundwater Sustainability Plan Reporting Process and Requirements – YouTube, March 14, 2024

Ŝ Webinar recording with Spanish captions –Coming Soon

Ŝ Presentation slides from this webinar are now available

• SGMA Portal: All information related to GSAs, GSPs, Alternatives to GSPs, Adjudicated areas and Basin Boundary Modifications can be found on the SGMA Portal

DWR’s GSP Implementation Guidance A Guide to Annual Reports, Periodic Evaluations, and Plan Amendments and Frequently Asked Questions and Available Resources provide guidance to GSAs preparing Annual Reports, Periodic Evaluations, and GSP Amendments for GSP implementation and compliance with SGMA and the GSP Regulations.

Experts in Water Resources Planning and SGMA Implementation

With offices in Oakland, San Luis Obispo, Sacramento, and Monterey, we specialize in:

Hydro Visions

GeoH2oMysteryPix

by Chris Bonds, Sacramento Branch Member at Large

GeoH2OMysteryPix is a fun addition to HydroVisions that started in Fall 2022. The idea is simple; I share some questions, some cool supporting geology and/or water resources photo(s) along with a hint, and readers email in their guesses.

In a future issue of HydroVisions, I will share the answer(s) along with some brief background/historical information about the photos and acknowledge the first person(s) to email me the correct answer(s).

GRA looks forward to your enthusiastic participation in GeoH2OMysteryPix.

WINTER 2024 ANSWERS

What is this? Where is it Located?

Hint: A hidden gem of a historical site in the High Sierras.

Congratulations to GRA member Robert Gailey, Consulting Hydrogeologist PC for providing the following correct response to the Winter 2024 GeoH2OMysteryPix questions:

“That looks like the train tunnel near the top of Donner Pass Road and the Pacific Crest Trail. Beautiful spot!”

Background/History: These two photos show key features of the world-famous Donner Summit Tunnel No. 6 (ST6); the left photo shows the western portal of ST6, and the right photo shows the steel cover over the central construction shaft into ST6. The Central Pacific Railroad (CPRR) began excavation of ST6 on September 20, 1866, from the east

and west ends. One month after tunneling began (October 1866), a central construction shaft, about 12 feet in size, was started to allow for tunneling from the middle outward; so, four excavation faces simultaneously. The shaft took 85 days to excavate to a depth of about 90 feet. Blast hole drilling in the granitic terrain was done with a 3-worker team using a hand-held drill bit that was hit with two alternating 8-lb. sledgehammers, called a double jack to produce the 2.5-inch holes that were needed for black powder. Up to 300 lbs. of black powder were used daily.

The subsequent availability of nitroglycerine was a real time saver because of its greater explosive power, so smaller drill holes could be used, and more holes could be drilled each day. Each team could drill three 1.25-inch x 2.5-foot-deep holes in 12 hours for nitroglycerine. Railroad workers advanced

Cartoon of ST6 excavation at 4 faces simultaneously

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each tunnel face about 14 inches per day using hand tools and explosives. The best day ever resulted in 27 inches of progress.

The majority of the tunneling was done by Chinese immigrants, some of whom lost their lives to accidental explosions, falling rocks, and winter avalanches. In the tunnels, they worked by candle and lantern light. The ST6 air was filled with rock dust and explosives residue, and ventilation was poor. The working conditions were horrible. Break-through on the western and eastern ends occurred on August 3 and 28, 1867, respectively. ST6 was 1,659-feetlong, 19-feet-high, and 16-feet-wide at its base, had a curve, and a 30-foot elevation change over its length; a crowning achievement of mid-19th century engineering. When ST6 was finally completed in August 1867, engineers’ calculations were so precise that the four tunnels—two boring inward from east and west, and two moving outward from the central shaft—were off by less than two inches. ST6 was the longest of 15 tunnels excavated by CPRR in their quest to conquer the Sierra Nevada Mountains. On June 18, 1868, the first passenger train passed through ST6. The last Southern Pacific Railroad freight train to pass through ST6 was in 1993. All rail traffic has since moved over to the Track #2 grade crossing the summit one mile south of Donner Pass through the 10,322-foot-long Tunnel 41 running under Mount Judah between Soda Springs and Eder. Tunnel 41, aka the Big Hole (1925), was the third longest in the continental US. Granitic

SPRING 2024 QUESTIONS

rock excavated from ST6 filled in the ravine between Tunnels 7 and 8 and was used to build a free-standing, gravity retaining wall called the China Wall. No mortar was used in the construction of the wall, which continues to withstand the region’s harshest conditions over 150 years later and is a true engineering masterpiece. Using a tunnel boring machine today, ST6 would have taken about a month to excavate.

References:

DSHS 2012. Article Series on Summit Tunnel No. 6, Heirloom Newsletters #44-49, April – September, Donner Summit Historical Society (DSHS).

Signor, J.R., 1985. Donner Pass – Southern Pacific’s Sierra Crossing. Golden West Books. San Marino, California.

What is this? Where is it Located?

Hint: This innovative CA structure was built in the mid-20th century. Think you know What this is and Where it is Located? Email your guesses to Chris Bonds at goldbondwater@gmail.com

Topographic Map of Donner Summit showing the Locations of Hard-Rock Railroad Tunnels

PartinG sHot Hydro Visions

by John Karachewski, PhD

The Redwood Creek watershed in Northern California is mostly forested, steep mountainous terrain, with an area of approximately 280 square miles. Undammed Redwood Creek flows for 60 miles, with 18 of those miles winding through Redwood National Park and State Parks (RNSP) and through some of the tallest trees on earth. Redwood Creek is an important salmon stream that provides critical habitat for chinook, steelhead, and coho runs. The lower watershed is within RNSP, whereas the upper watershed is mostly private timber lands. Redwood Creek flows into the Pacific Ocean near the town of Orick.

By the mid 1960’s, over 90 percent of all the old-growth redwood forests had been logged in California. After much controversy and compromise with timber companies, Congress finally approved a federal park and, on October 2, 1968, President Lyndon B. Johnson signed into law the act that established Redwood National Park. In 1994, the National Park Service and California State Parks agreed to a unique partnership to jointly manage four regional parks for resource protection. RNSP is a World Heritage Site and protects 45% of the world’s remaining coast redwood old-growth forests.

Despite their ecological riches and beauty, these forests are far from pristine. Approximately, two-thirds of the 132,000-forested acres that are now in RNSP bear the scars of industrial-scale logging before the parks were established. Logging left behind steep denuded slopes, thousands of miles of abandoned dirt roads and skid trails, and forest debris. Significant erosion, especially during storms and by landslides, negatively impacted Redwood Creek, its trees, and wildlife. The high sediment runoff damaged fish habitat, filled stream pools, and destroyed riparian vegetation.

Watershed rehabilitation programs in the parks began in the late 1970s. Redwoods Rising unites Save the Redwoods League, California State Parks, and the National Park Service along with local communities, Tribes, and park visitors to protect and implement a landscape-scale restoration program.

A drive along Bald Hills Road in RNSP offers sweeping views of the Redwood Creek watershed, Pacific Ocean, Trinity and Siskiyou Mountains. The Bald Hills occur as discontinuous grasslands and oak woodlands alternating with coniferous forests along the ridge crest dividing the Klamath River and Redwood Creek drainages. The Bald Hills have a human history and stories going back to time immemorial. The cultural resources include prehistoric villages, seasonal camps, trails, and ceremonial sites representing use over the past 4,500 years; historic homesteading and ranching structures and sites dating to the gold rush in the 1850s; and contemporary Native American sites.

Photographed by John Karachewski, Ph.D., along Bald Hills Road in RNSP on May 3, 2024. GPS coordinates of the photo are 41.157343° and -123.891408°. Refer to Redwood National and State Parks website for additional park information.

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t H ank y ou t o o ur c ontributors

Dr. Abhishek Singh is a Principal Engineer with more than 20 years of experience and is President of INTERA’s Water Resources & Supply Line of Business, where he leads and manages operations, business development, strategic planning for the lob across the United States. He has authored several technical publications and journal articles on groundwater modeling and calibration, stochastic optimization techniques, uncertainty and risk analysis, climate change, and emerging contaminants. Dr. Singh is also the chair of the GRA technical committee and serves on the GRA board of directors.

Chris Bonds is a Senior Engineering Geologist (Specialist) with the California Department of Water Resources (DWR) in Sacramento. Since 2001, he has been involved in a variety of statewide projects including groundwater exploration, management, monitoring, modeling, policy, research, and water transfers. He has over 30 years of professional work experience in the private and public sectors in California, Hawaii, and Alaska and is a Professional Geologist and Certified Hydrogeologist. Chris received two Geology degrees from California State Universities. He has been a member of GRAC since 2010, a Sacramento Branch Officer since 2017, and has presented at numerous GRAC events since 2004.

John Karachewski, PhD, retired recently from the California-EPA in Berkeley after serving as geologist for many years in the Geological Support Branch of the Permitting & Corrective Action Division for Hazardous Waste Management. John has conducted geology and environmental projects from Colorado to Alaska to Midway Island and throughout California. He leads numerous geology field trips for the Field Institute and also enjoys teaching at Diablo Valley College. John enjoys photographing landscapes during the magic light of sunrise and sunset. Since 2009, John has written quarterly photo essays for Hydrovisions.

Haseeb Khan, a Stanford-educated Technologist, Mathematician and Computer Scientist focusing on Artificial Intelligence/AGI, is passionate about using AI and Big Data to unravel complex problems across a variety of fields, including Computational Fluid Dynamics, Pharmacokinetics, Healthcare, Finance, and Physical Systems. As a Senior AI/ML Engineer and Generative AI Ambassador at Google, his work is dedicated to exploring and expanding the boundaries of AI to offer solutions that traditional methods cannot fully address. Mr. Khan specializes in developing deep learning methods and reinforcement learning strategies that have wide-ranging implications, from improving medical diagnostics to enhancing our understanding of our planet. His commitment to AI is driven by a belief in its capability to provide novel insights into complex systems, demonstrating its potential to significantly impact various sectors, including the nuanced field of groundwater and rare earth mineral management.

Lisa Porta, PE, is a senior water resources engineer and California Water Strategy Lead with Montgomery & Associates, in Sacramento, CA. She has more than 15 years of groundwater modeling and integrated water resources planning experience in California and the Western United States. She specializes in SGMA implementation and supports local water agencies with navigating the increasingly complex regulatory environment with using appropriate data and tools.

Todd Jarvis, PhD, is the Director of the Institute for Water and Watersheds, Oregon State University, Corvallis. Todd has 30 years of experience as a hydrogeologist specializing in groundwater development and source water protection with emphasis in fractured rock and karst terranes. With professional licenses as a Certified Engineering Geologist, Certified Water Right Examiner, and Certified Mediator, his interests include transboundary aquifers, environmental conflict resolution, and education in water science and policy.

Tyler Hatch is a Principal Engineer with INTERA. In his previous role, he was part of the Sustainable Groundwater Management Office (SGMO) at the California Department of Water Resources for almost six and a half years. For the last three years, he was a member of the SGMO management team and led the Modeling and Tools Support Section for the last 3 years. One of the major projects Tyler led was the development of the Fine-Grid California Central Valley Groundwater-Surface Water Simulation model (C2VSimFG), which included improvements to simulating land subsidence in the Central Valley.

Sydney Nye heads the Machine Learning Division at GEI Consultants. Her work spans across various sectors, including the integration of Artificial Intelligence, Data Governance and Data Augmentation in groundwater management. A Stanford Alumna with extensive experience, Sydney combines academic rigor with practical industry applications to develop highly effective, state-of-the-art solutions. Her dedication to using technology for enhancing sustainability influences her approach to water resource management, infrastructure resilience and repair, and environmental conservation across projects. By prioritizing current and future industrial trends and needs in combination with cutting-edge AI technology, Sydney incorporates these methodologies into practical, impactful large scale applications for dynamic client needs.

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