TOOLS FOR ASSESSING GROUNDWATER-SURFACE WATER CONNECTIVITY UNDER THE SUSTAINABLE GROUNDWATER MANAGEMENT ACT Key findings and recommendations from a one-day workshop on assessing, monitoring and quantifying interconnected surface waters under SGMA

Prepared by Tara Moran, Tom Gleeson, Melissa Rohde, Ben Kerr and Christina Babbitt

February 2019

Acknowledgements

The authors would like to thank all those who participated in the dialogue and provided feedback during the development of this report. We would also like to thank Bea Gordon for her help with this report. In addition, the authors would like to thank Megan Glatzel and Athena Serapio for organizing meeting logistics. Finally, thank you to the S.D. Bechtel, Jr. Foundation for their ongoing financial support for this work.

Report Reviewers (alphabetical order)

Jessica Bean, State Water Resources Control BoardLetty Belin, ConsultantSam Boland-Brien, State Water Resources Control BoardMichael Kiparsky, UC BerkleyErik Ringelberg, The Freshwater TrustAnthony Saracino, ConsultantLeon Szeptycki, Stanford University

Thank you to all of our reviewers. Your comments and suggestions helped to significantly improve the report. The authors would like to note that reviewers were not asked to endorse the report’s conclusions or recommendations, nor did they see the final version of the report. As a result, responsibility for the final content of this report rests entirely with the report’s authors.

Suggested Citation: Moran, T., Gleeson, T., Rohde, M., Kerr, B., and Babbitt, C. (2018). Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act. Dialogue report prepared by Water in the West, University of Victoria, The Nature Conservancy, Foundry Spatial and the Environmental Defense Fund. Stanford Digital Repository. Available at: https://purl.stanford.edu/mn804jy8641.

This report was developed out of a workshop hosted by Water in the West in partnership with The University of Victoria, Foundry Spatial, Environmental Defense Fund and the Nature Conservancy.

TABLE OF CONTENTS

Introduction ..................................................................................................................................................................... 1

Focus area summaries .................................................................................................................................................... 2

1) Accounting for beneficial uses and users in GSP development and implementation ................................................. 2

Findings ............................................................................................................................................................. 2

2) Identifying physical or analytical approaches for characterizing, quantifying and monitoring ISW ............................. 3

Findings ............................................................................................................................................................. 4

3) Using hydrological modeling to assess effects of groundwater depletion on ISW and streamflow depletions ............. 5

Box 1. Overview of analytical and numerical model codes ..................................................................................... 5

Findings ............................................................................................................................................................. 6

4) Understanding the functionality and use of decision support tools from other jurisdictions ....................................... 6

Findings ............................................................................................................................................................. 8

Summary ......................................................................................................................................................................... 9

Summary findings and recommendations .................................................................................................................. 9

For GSAs ................................................................................................................................................................. 9

For state and federal agencies .................................................................................................................................. 9

References .................................................................................................................................................................... 11

Appendix A. Workshop attendees ................................................................................................................................ 12

Appendix B. Workshop agenda ..................................................................................................................................... 13

Appendix C. Workshop questionnaire ........................................................................................................................... 16

Appendix D. Supplementary tables .............................................................................................................................. 17

Table D1. Legal and regulatory requirements for interconnected surface water under SGMA. ..................................... 17

Table D2. Regulatory code pertaining to the consideration of beneficial uses and users under SGMA ......................... 18

Table D3. Overview of tools and approaches for assessing interconnected surface water and streamflow depletions. . 19

Table D3. References ............................................................................................................................................. 25

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INTRODUCTIONIn 2014, California enacted the Sustainable Groundwater Management Act (SGMA), which requires local agencies to develop and implement groundwater sustainability plans (GSPs) in all groundwater basins designated by the California Department of Water Resources (DWR) as high or medium priority1 by 2020 or 2022, depending on basin condition.2 For the first time in California’s history, agencies managing groundwater under SGMA must assess the impacts of groundwater pumping on water supply and surface water flows and avoid “significant and unreasonable adverse impacts on beneficial uses of the surface water.”3

SGMA’s legal and regulatory requirements pertaining to interconnected surface water – defined in SGMA as, “surface water that is hydraulically connected at any point by a continuous zone to the underlying aquifer and the overlying surface water is not completely depleted.”4 – represent a significant step forward in recognizing the interconnected nature of surface water and groundwater and for managing this resource accordingly. However, because groundwater-surface water connectivity was not a common management consideration prior to the enactment of SGMA, many basins lack data or models or technical capacity to adequately characterize interconnected surface water (ISW) and evaluate the impacts of groundwater pumping on these systems. Thus, meeting legal and regulatory requirements related to ISW may be hindered by a lack of information about both the location and timing of such waters, as well as the many beneficial uses and users that they support.

In March 2018, Water in the West, The University of Victoria, Foundry Spatial, The Nature Conservancy (TNC) and Environmental Defense Fund co-hosted a workshop on tools to assess ISW under SGMA. The workshop, which included a small, select group of hydrologists, water managers, water lawyers, nongovernmental organizations (NGOs) and academia, focused on four main areas:

1) Accounting for beneficial uses and users in GSP development and implementation;

2) Identifying physical or analytical approaches for characterizing, quantifying and monitoring ISW;

3) Using hydrological modeling to assess the effects of groundwater pumping on ISW and streamflow depletions; and

4) Understanding the functionality and use of decision support tools from other jurisdictions

This report summarizes key findings from the one-day workshop and a short questionnaire completed by workshop participants during the day. A list of workshop attendees, the workshop agenda and workshop questionnaire can be found in Appendices A-C, respectively.

1 The California Department of Water Resources (DWR) assigns all 517 of California’s alluvial groundwater basins to one of four categories. These categories are high, medium, low and very low priority (See California Water Code (CWC) §10722.4(a)). Groundwater basins designated as medium and high priority basins are subject to SGMA and must develop groundwater sustainability plans.

2 Groundwater sustainability plans (GSPs) must be completed by January 31, 2020, for the 21 groundwater basins that the DWR has designated as being in a state of critical overdraft. GSPs for all remaining high and medium priority basins must be completed by January 31, 2022. (CWC §10720.7.)

3 CWC §10721(x)(6)

4 23 California Code of Regulations (CCR) §351(o)

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FOCUS AREA SUMMARIES1) Accounting for beneficial uses and users in GSP development and

implementation

SGMA requires GSPs to avoid undesirable result #6, which is “significant and unreasonable adverse impacts on beneficial uses of the surface water.” The State Water Resources Control Board (SWRCB) formally defines 23 beneficial uses of surface water and groundwater.5 In addition to agricultural, domestic and municipal water uses, many beneficial uses of surface water may be impacted by depletions of interconnected surface waters, including habitat, refuges and reserves, cold or warm water ecosystems, estuarine and terrestrial ecosystems and others. For more detail on beneficial uses and the legal and regulatory requirements related to ISW under SGMA see Belin (2018), Cantor et al. (2018), and Tables D1 and D2 in Appendix D.

In addition to avoiding impacts on beneficial uses of surface water, SGMA also requires groundwater sustainability agencies (GSAs) (the local agencies developing GSPs) to “consider the interests of all beneficial uses and users of groundwater [emphasis added]”, including, but not limited to: (1) Overlying groundwater rights holders, including agricultural and domestic well owners; (2) Municipal well operators and public water systems; (3) Land use planning agencies; (4) Environmental groundwater users; (5) Hydrologically connected surface water users; (6) The federal government; (7) California Native American tribes; (8) Disadvantaged communities; and (9) Entities monitoring and reporting groundwater elevations in all or a part of a groundwater basin managed by the groundwater sustainability agency.6

Evaluating the impacts of groundwater depletions on beneficial users of surface water and groundwater will require GSAs to undertake several actions. First, GSAs will need to develop a comprehensive understanding of the location, quantity and timing of ISW7 as of the SGMA benchmark date (January 1, 2015) and thereafter. Second, GSAs will need to assess what the beneficial users of groundwater and surface water in each basin are, understand the conditions under which groundwater depletions in the basins would result in “significant and unreasonable impacts” on these users and translate these impacts into measurable objectives, interim milestones and minimum thresholds that can be incorporated into their GSPs.8 Finally, GSAs will need to develop a monitoring network with data of sufficient quality, frequency and distribution to characterize ISW in the basins and evaluate how they change as a result of Plan implementation.9 GSAs should take an iterative approach to understanding and monitoring the impacts of groundwater pumping on surface water and groundwater uses and users in their basin.

Findings

• Only basins with ISW are potentially vulnerable to undesirable result #6; thus GSAs will need to establish if there is ISW in their basins. At present, there is limited information about the spatial and temporal connectivity of surface water and groundwater systems in many groundwater basins throughout the state. 23 CCR §§353.2 and 354.16 require DWR to provide information, where possible, to identify ISW and “estimate the quantity and timing of depletions in those systems.”

• Uncertainty about the extent and timing of ISW should not hinder management actions and the development of meaningful

5 California State Water Resources Control Board (2014). Beneficial Use Definitions. Available at: https://www.waterboards.ca.gov/about_us/performance_report_1617/plan_assess/docs/bu_definitions_012114.pdf. Some Regional Water Resources Control Boards have identified additional beneficial uses that have also been approved by the SWRCB. Id., p. 5.

6 CWC §10723.2

7 23 CCR §354.16

8 23 CCR §§ 354.28 and 354.30

9 23 CCR §354.32

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measurable objectives and interim milestones. To account for this uncertainty, local agencies will need to take a conservative approach in developing the measurable objectives and minimum thresholds to ensure that they are protective of beneficial uses of groundwater and surface water. These thresholds can be revised over time as understanding of the system increases and the impacts of groundwater pumping on beneficial users becomes clearer.

• SGMA does not override preexisting laws that protect specific beneficial uses or users. For example, the Federal or State Endangered Species Act may have certain instream conditions (e.g., flow or temperature) that are impacted by groundwater pumping. Instream flow criteria to protect state or federally listed endangered species will need to be maintained regardless to what conditions existed on Jan 1, 2015. See Belin (2018) and Cantor et al. (2018) for more information on other legal requirements related to ISW under SGMA.

• GSAs will need to identify all beneficial uses and users of surface water and groundwater within a basin. Beneficial users should be included in discussions to define significant and unreasonable adverse impacts and the design of protective minimum thresholds.

• In some basins, existing instream flow criteria adopted by the SWRCB will serve as the basis for minimum thresholds for surface water depletions.10 However, even where instream flow criteria exist, GSAs will need to consult with local beneficial users to ensure that these criteria are protective of all interests.

• In basins without existing instream flow criteria, insight from DWR, SWRCB, the California Department of Fish and Wildlife and other state and federal agencies on the methodologies used for the development of instream flow criteria may be helpful in guiding GSA development of minimum thresholds for ISW.

• Research by Carlisle et al. (2016) provides estimates of natural monthly streamflow for streams throughout California which may be useful in estimating impacts to streamflow resulting from groundwater pumping and other factors.

• The Groundwater Resources Hub (TNC) provides maps, guidance and case studies of groundwater dependent ecosystems (GDEs) – one category of beneficial users of groundwater listed in CWC §10723.2.11

2) Identifying physical or analytical approaches for characterizing, quantifying and monitoring ISW

The technical challenges in determining the location and timing of ISW are substantial (Barlow and Leake 2012). These challenges are particularly acute in California because groundwater and surface water are considered legally separate resources governed by different legal regimes. This legal separation is partially responsible for the lack of information about the spatial extent and timing of ISW in most groundwater basins in the state. Additionally, there is a lack of technical expertise about the tools, methods and techniques to identify and monitor for ISW at the local and regional scale. Building on work by Cantor et al. (2018), workshop participants developed Table D3 in Appendix D, which provides an overview of some of the field- and model-based methods for assessing ISW, their benefits and their limitations.

SGMA allows for multiple GSAs and GSPs within a single groundwater basin.12 Where multiple GSPs exist within a basin, GSAs must use the same data and methodologies in developing their water balance, sustainable yield, groundwater extraction data and other assumptions.13 Data related to ISW are not explicitly addressed in this section of the legislation. However, inconsistencies in data and methods used to quantify ISW and the impacts of groundwater pumping on ISW may lead to conflicts between

10 California Department of Fish and Wildlife, (2018) CDFW Instream Flow Recommendations Map. Available at: https://www.wildlife.ca.gov/Conservation/Watersheds/InstreamFlow/Recommendations.

11 More information on the Groundwater Resources Hub can be accessed at: https://www.scienceforconservation.org/products/groundwater-resource-hub.

12 CWC §§10723(d) and 10727(b)

13 CWC §10727.6

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groundwater pumpers and surface water users. GSAs should seek to develop consistent and integrated data, methodologies and modeling approaches for assessing ISW within a basin and between hydrologically connected basins.

Findings

• Many of the methods described in the Table D3 in Appendix D are summarized in Barlow and Leake (2012); Rosenberry and LaBaugh (2008); and at the U.S. Geological Survey (USGS) Hydrogeophysics Branch website.14

• The importance of high quality, high resolution stream gauging data for understanding and modeling a watershed cannot be overstated. Despite having the technology and knowledge of its importance, insufficient stream gauge data remains a major limitation in watershed hydrology research and management in California. Federal, state, regional and local agencies should work together to support the ongoing maintenance and expansion of California’s stream gauging network. These efforts should include installing more gauges and ensuring adequate long-term funding for the maintenance of stream gauge networks.

• The majority of stream gauge data in California comes from the California Data Exchange Center and the U.S. Geological Survey (USGS). Despite the importance of stream gauge data for the evaluation of ISW, recent analysis by TNC found that 86% of the significant streams in California (those that drain over 1,200 acres) are poorly gauged, and that the number of gauged streams across the state has declined substantially over time.15

• Recent work by Miller et al. (2018) highlights the importance of stream gauge data to support water management decisions, including water infrastructure operation.

• Meeting the legal and regulatory requirements related to ISW will require significant technical expertise and resources. DWR should develop expertise and guidance on local-scale identification, assessment and monitoring of ISW under SGMA. Developing this expertise at the state level and sharing this expertise with resource-strapped GSAs would significantly improve their ability to meet the legal requirements relating to ISW under SGMA.

• Local agencies should seek to develop consistent and integrated data, methodologies and modeling approaches for assessing ISW within a basin and between hydrologically connected basins. Whenever possible, state and federal agencies, NGOs and academic institutions should support the development of consistent ISW assessment and monitoring efforts by coordinating their work on the topic to ensure consistency in messaging and outputs.

• DWR and the SWRCB should take an iterative approach in evaluating GSPs, particularly with respect to ISW.

• During GSP development GSAs should focus on: 1) correctly characterizing ISW that occurs within their basins; 2) installing a monitoring network capable of providing insight into spatial and temporal exchanges between the surface water and groundwater systems over time; 3) identifying all beneficial uses of groundwater and surface water in the basin, and conditions that would constitute significant and unreasonable impacts; 4) translating potentially significant and unreasonable impacts into minimum thresholds that are protective of beneficial users; and 5) developing a model that can be used to quantify the impacts of groundwater pumping on ISW.

14 United State Geological Survey, (2018). Hydrogeophysics Branch website. Available at: https://water.usgs.gov/ogw/bgas/.

15 The Nature Conservancy, (2018). Gage Gap Map. Available at https://water.usgs.gov/ogw/bgas/.

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3) Using hydrological modeling to assess effects of groundwater depletion on ISW and streamflow depletions

Well calibrated hydrologic models can be used to understand how hydrologic systems are likely to respond to future changes in climate, land use or other factors and to estimate the impacts of groundwater pumping on interconnected surface water (Barnett et al. 2012).

23 CCR §354.28(c)(6)(B) requires the use of a numerical groundwater and surface water model, “or an equally effective method, tool, or analytical model” to quantify surface water depletion in GSPs. Workshop discussions focused on the relative advantages and disadvantages of using numerical hydrological models and analytical models to model streamflow depletions. See Box 1 for more information on the differences between analytical and numerical model codes.

Box 1. Overview of analytical and numerical model codes

Analytical model codes describe the physical processes of groundwater flow or contaminant transport using one or more governing equations. These model codes are generally a greatly simplified version of a three-dimensional flow problem and generally assume that the system remains uniform through space and time.

While analytical model codes are not typically used to represent changing conditions (DEQ 2014), they are much faster and cheaper to build and run than their numerical counterparts. Importantly, they provide valuable insight into the fundamental behavior of an aquifer system in response to pumping, recharge or groundwater-surface water connection and how it relates to its hydrogeologic properties.

Numerical model codes solve the same mathematical equations as analytical models. However, to accommodate complex aquifer system and boundary condition geometries, numerical models divide the physical system being modeled into discrete cells or elements. The ability to model across both space and time enables the simulated environment (e.g., hydrogeologic conditions, pumping rates, etc.) to change.

Because of the complexity of aquifer systems and the extensive input requirements for numerical models, these model codes can be labor-intensive to build and calibrate (Anderson et al. 2015). Additionally, numerical model codes require sufficient data for model input and calibration (DEQ 2014). However, when developed and calibrated appropriately numerical models can serve as a powerful tool to simulate geologically complex or more developed hydrologic systems and to forecast long-term changes to the system.

The simplifying assumptions used in analytical models generally mean that these models require less data than numerical models and are faster and easier to build, run and maintain. Thus, analytical models are commonly used in regions where data is sparse (Barnett et al. 2012), to evaluate the impacts of pumping on surface water bodies in relatively underdeveloped regions (Huggins et al. 2018), or as a “screening” tool or “first-order” estimate of pumping impacts (Reeves et al. 2009).

By contrast, numerical models are capable of representing more complex aquifer systems and thus can provide a much more nuanced understanding of a system. Well-developed and calibrated numerical models can serve as a powerful tool to simulate geologically complex or more developed hydrologic systems and forecast long-term changes to the system. However, these models are labor-intensive to develop and calibrate, and require extensive data inputs.

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Integrating the use of analytical and numerical models, as is done in other states, may be a means of capturing the best attributes of both model types. For example, analytical models, which produce rapid, accessible information can be used as screening level tools across larger areas. More complex, detailed numerical models can be developed in areas with more data and with more complex management structures. See Section 4 for an example of an analytical model used as a screening tool in Michigan to differentiate between groundwater withdrawals that are not likely to cause an adverse resource impact upon streams and those that may have an adverse impact.

Findings

• There are many good summaries on the use of hydrologic models for estimating ISW, guidelines for their use and descriptions of model limitations, including Barlow and Leake (2012); Barnett et al. (2012); and Rathfelder (2016).

• There are advantages and disadvantages to using analytical versus numerical hydrological models for identifying and quantifying the impacts of groundwater pumping on streamflow. Integrating the use of analytical and numerical models across groundwater basins may be a means of capturing the best attributes of both model types. For example, in Michigan, an analytical model is used as a “screening tool” to identify groundwater withdrawals that are likely to have an adverse impact on fish populations, which then triggers a site-specific review that includes the use of a numerical model. Section 4 has more information on the Michigan Tool.

• As discussed in section 2, stream gauge data plays an essential role in developing and calibrating both analytical and numerical hydrologic models. Funding to support and expand the maintenance and development of the stream gauging network in California would provide foundational data to GSAs with ISW, as well as support many other hydrologic analyses.

• DWR is currently developing the Sacramento Valley Groundwater-Surface Water Simulation Model (SVSim) to, among other things, evaluate ISW in California’s Sacramento Valley (CDWR 2018). Similar steps should be undertaken to improve the California Central Valley Groundwater-Surface Water Simulation Model (C2VSim) – DWR’s hydrological model for California’s Central Valley. Doing so would improve consistency in groundwater modeling efforts within and between hydrologically connected basins, reduce redundancy and inefficiencies in model development and improve evaluation of ISW in California’s Central Valley.

• Further research to assess the performance of analytical and numerical models in similar scenarios could provide insight and guidance on the level of model complexity necessary and useful for groundwater management decisions in different hydrologic and institutional environments.

4) Understanding the functionality and use of decision support tools from other jurisdictions

There is a growing interest in using data integration, visualization and modeling tools to guide water management decisions. In this session, workshop participants heard from people involved in the development of two online tools used to support water management decisions in Michigan and British Columbia, Canada. These tools are the Michigan Water Withdrawal Assessment Tool (WWAT),16 an online screening tool used to identify new or increased groundwater withdrawals that may have adverse impacts on fish populations in Michigan (Hamilton and Seelback 2010), and the BC Water Tool,17 which integrates public, water-related data to support decisions for water use approvals and licenses.

16 http://www.deq.state.mi.us/wwat/(S(acxkwjuipqawhap521vwyq4m))/default.aspx

17 http://www.bcwatertool.ca/

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Michigan Water Withdrawal Assessment Tool

The Michigan Water Withdrawal Assessment Tool (WWAT) is an online tool used to assess proposed new or increased water withdrawals. This tool was developed as part of the water-withdrawal process mandated by State of Michigan Public Act 34 of 2006, which sought to determine “whether the proposed [water] withdrawal may cause an adverse impact to the waters of the state or to the water-dependent natural resources of the state.”

The WWAT combines three models: an analytical groundwater model, a streamflow model and a fish impact model, which rely on a mix of public and proprietary data (Huggins et al. 2018). Users input information about the proposed pumping withdrawal, including withdrawal source, pumping capacity and location, well depth, aquifer type and pumping schedule (Reeves et al. 2009). Withdrawal impacts are categorized into one of four adverse resource impact categories, which range from Zone A (low risk) to Zone D (high risk). Withdrawals categorized as Zone D are subject to additional agency review (Reeves et al. 2009).

WWAT has been in use for approximately 10 years and is considered to be the most prominent online conjunctive management screening tool to date (Huggins et al. 2018). It has relatively low data requirements and is easy to use. Despite its success, there are some lessons that have been learned during tool implementation. First, when developing online screening tools, agencies need to anticipate the resources and expertise necessary to conduct site-specific reviews when they are triggered, including the capacity to develop and run more complex models of the system, and processes for reviewing data and analysis from applicants. Second, tool development and implementation must include stakeholder outreach and communication to ensure transparency in the screening process. Finally, relatively minor differences in interpretation of the system can lead to distrust in the tool. Maintaining dialogue with users is essential to ensure these discrepancies are caught and addressed before they come issues.

BC Water Tool

Developed by Foundry Spatial for the British Columbia Ministry of Forests, Lands, Natural Resource Operations and Rural Development and the British Columbia Oil and Gas Commission, the BC Water Tool is a map-based water information tool used by applicants and the province to make decisions about water withdrawal permits.

The BC Water Tool uses analytical models to estimate streamflow depletions over the simulation period. Inputs to the BC tool include surface water data, groundwater extraction data and hydrogeologic data. Many of these inputs are pulled from publicly available sources, which can then be supplemented with higher-resolution data where available. For example, stream networks and flow rates have been mapped globally by Lehner et al. (2008). Similarly, some hydrogeologic data such as porosity and permeability have been mapped globally (Gleeson et al. 2014). The intent of the BC tool is to provide users with the ability to consider questions relating to water supply, demand and ecosystem needs at the stream, aquifer or well scale.

The ability to overlay higher resolution data enables the BC tool to be used in different settings; however, tool limitations exists. These limitations include data availability and the simplifying assumptions necessary to facilitate the use of all available data (Huggins et al. 2018). Unlike the WWAT, the BC tool does not serve as a screening tool for approving new water rights: rather, it outputs streamflow depletions that can be used by resources managers to support management decisions.

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The WWAT and the BC Water Tool demonstrate the value of online decision support tools to guide water management decisions. Key findings and lessons learned from these tools are summarized below.

Findings

• Data and visualization tools can help inform water management decisions. However, these tools require significant time, data and resources to develop. Thus, agencies developing tools should ensure sufficient budgetary and personnel commitments for tool development, ongoing support/maintenance and tool outreach and communication.

• Additionally, when developing online screening tools, agencies need to anticipate the resources and expertise necessary to conduct site-specific reviews when they are triggered, including the capacity to develop and run more complex models of the system, and processes for reviewing data and analysis from applicants.

• Bearing in mind the considerations outlined above, the state should consider developing screening or decision support tools to support the management of ISW.

• The development and implementation of screening or decision support tools should include extensive and ongoing stakeholder outreach and communication to ensure that tools meet user needs, are simple to use and understand, and communicate outputs in a comprehensible manner. Additionally, the stakeholder outreach process should seek to identify and address issues associated with tool development or implementation early in the process before they cause distrust in the tool.

• Tool developers should clearly convey data sources, methods, model assumptions and tool limitations.

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SUMMARYGroundwater and surface water are physically connected and are manifestations of the same resource. Developing a comprehensive understanding of the timing, nature and extent of this connection, as the basis to assess streamflow depletions resulting from groundwater pumping and other impacts on beneficial uses and users, as required under SGMA, will not be easy. However, it is essential for sustainable water management. Taking a thoughtful and systematic approach to developing a coordinated groundwater monitoring network that can serve as the basis for model development and project planning to address SGMA’s ISW requirements will provide local and state agencies with the data and tools necessary to manage this precious resource for all users in the future.

Summary findings and recommendations

For GSAs

• Only basins with ISW are subject to undesirable result #6, thus GSAs will need to establish whether there is ISW in their basins. At present, there is limited information about the spatial and temporal connectivity of surface water and groundwater systems in many groundwater basins throughout the state.

• GSAs with ISW should assess existing stream gauge networks in their basin and prioritize additional stations, where necessary.

• For existing guidance on legal challenges see Belin (2018) and Cantor et al. (2018). Building on work by Cantor et al. (2018), workshop participants developed Table D3 in Appendix D, which provides an overview of the some of the field- and model-based methods for assessing ISW, their benefits and their limitations.

• There are advantages and disadvantages to using analytical versus numerical hydrological models for identifying and quantifying the impacts of groundwater pumping on streamflow. Integrating the use of analytical and numerical models across groundwater basins may be a means of capturing the best attributes of both model types. For example, in Michigan, an analytical model is used as a “screening tool” to identify groundwater withdrawals that are likely to have an adverse impact on fish populations, which then triggers a site-specific review that includes the use of a numerical model. Section 4 has more information on the Michigan Tool.

• GSAs should take an iterative approach to understanding and monitoring the impacts of groundwater pumping on surface water and groundwater uses and users in their basin.

For state and federal agencies

• DWR should develop expertise and guidance on local-scale identification, assessment and monitoring of ISW under SGMA. Developing this expertise at the state level and sharing this expertise with resource-strapped GSAs would significantly improve their ability to meet the legal and regulatory requirements relating to ISW under SGMA.

• Additional guidance, data and support from state and federal agencies and others would dramatically improve GSAs’ assessments of ISW in their basins. Specifically,

– As outlined in 23 CCR § 354.16(f), DWR should provide data on ISW for all high and medium priority basins.

– DWR, SWRCB, the California Department of Fish and Wildlife, NGOs and other institutions should summarize the methodologies used for the development of instream flow criteria to assist GSAs in basins without existing instream flow criteria with the development of minimum thresholds for ISW.

– Similar to work done on the Sacramento Valley Groundwater-Surface Water Simulation Model (SVSim), DWR should modify the California Central Valley Groundwater-Surface Water Simulation Model (C2VSim) to better evaluate ISW.

– DWR and/or the State Board should consider developing an online decision support tool for ISW.

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• The importance of high quality, high resolution stream gauging data for understanding and modeling a watershed cannot be overstated. Despite the availability of gauging technology and the understanding of its importance, insufficient stream gauge data remains a major limitation in watershed hydrology research and management in California. Federal, state, regional and local agencies should work together to support the ongoing maintenance and expansion of California’s stream gauging network. These efforts should include installing more gauges, providing more grants to support the existing gauge network, and ensuring an adequate long-term funding stream for the maintenance of stream gauge networks.

• DWR and the State Board will need to take an iterative approach in evaluating GSPs, particularly with respect to ISW.

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REFERENCESBarlow, P. M., & Leake, S. A. (2012). Streamflow depletion by wells: understanding and managing the effects of groundwater pumping on streamflow. U.S. Geological Survey Circular 1376. Available at: https://pubs.usgs.gov/circ/1376/.

Barnett, B., L.R. Townley, V. Post, R.E. Evans, R.J. Hunt, L. Peeters, S. Richarson, A.D. Werner, A. Knapton, and A. Boronkay. (2012). Australian groundwater modeling guidelines, Waterlines report, No. 82, National Water Commission, Canberra. Available at: http://www.groundwater.com.au/media/W1siZiIsIjIwMTIvMTAvMTcvMjFfNDFfMzZfOTYwX0F1c3RyYWxRyY5fZ3JvdW5kd2F0ZXJfb-W9kZWxsaW5nX2d1aWRlbGluZXMucGRmIl1d/Australian-groundwater-modelling-guidelines.pdf.

Belin, A. (2018). Guide to Compliance with California’s Sustainable Groundwater Management Act: How to Avoid the “Undesirable Result” of “Significant and Unreasonable Adverse Impacts on Beneficial Uses of Surface Waters”. Stanford Digital Repository. Available at: https://purl.stanford.edu/kx058kk6484.

[CDWR 2018] California Department of Water Resources. (2018). Central Valley Groundwater-Surface Water Simulation Model. Available at: https://water.ca.gov/Library/Modeling-and-Analysis/Central-Valley-models-and-tools/C2VSim.

Cantor, A., D. Owen, T. Harter, N.G. Nylen, and M. Kiparsky. (2018). Navigating Groundwater-Surface Water Interactions under the Sustainable Groundwater Management Act. Available at: https://www.law.berkeley.edu/wp-content/uploads/2018/03/Navigating_GW-SW_Interactions_under_SGMA.pdf.

Carlisle, D. M., Nelson, S. M., & May, J. (2016). Associations of stream health with altered flow and water temperature in the Sierra Nevada, California. Ecohydrology, 9(6), 930-941.

Gleeson, T., Moosdorf, N., Hartmann, J., & Van Beek, L. P. H. (2014). A glimpse beneath earth’s surface: GLobal HYdrogeology MaPS (GLHYMPS) of permeability and porosity. Geophysical Research Letters, 41(11), 3891-3898.

Hamilton, D. A., & Seelbach, P. W. (2010). Determining environmental limits to streamflow depletion across Michigan. The book of the states, 42, 534-537.

Huggins, X., Gleeson, T., Eckstrand, H., & Kerr, B. (2018). Streamflow Depletion Modeling: Methods for an Adaptable and Conjunctive Water Management Decision Support Tool. Journal of the American Water Resources Association, 54(5), 1024-1038. doi.org/10.1111/1752-1688.12659.

Lehner, B., Verdin, K., & Jarvis, A. (2008). New global hydrography derived from spaceborne elevation data. Eos, Transactions American Geophysical Union, 89(10), 93-94.

Miller, K., N. Green Nylen, H. Doremus, A. Fisher, G. Fogg, D. Owen, S. Sandoval Solis, J. Viers, and M. Kiparsky. (2018). California’s Stream Flow Monitoring System is Essential for Water Decision Making. Center for Law, Energy & the Environment, UC Berkeley School of Law, Berkeley, CA. 4 pp. Available at: https://www.law.berkeley.edu/research/clee/research/wheeler/stream-monitoring/.

Rathfelder, K. (2016). Modelling Tools for Estimating Effects of Groundwater Pumping on Surface Waters. Province of BC, Ministry of Environment, Water Science Series WSS2016-09. Available at: http://a100.gov.bc.ca/appsdata/acat/documents/r51878/tools4streamdepletion_1484093475019_4092907088.pdf.

Reeves, H.W., Hamilton, D.A., Seelbach, P.W., and Asher, A.J., (2009). Ground-water-withdrawal component of the Michigan water-withdrawal screening tool. U.S. Geological Survey Scientific Investigations Report 2009–5003. Available at: https://pubs.usgs.gov/sir/2009/5003/pdf/sir2009-5003_web.pdf.

Rosenberry, D. O., & LaBaugh, J. W. (2008). Field techniques for estimating water fluxes between surface water and ground water. U.S. Geological Survey Techniques and Methods 4-D2. Available at: https://pubs.usgs.gov/tm/04d02/.

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 11

APPENDIX A. WORKSHOP ATTENDEES Christina Babbit – Environmental Defense Fund

Letty Belin – Water in the West

Jessica Bean – California State Water Board

Oliver Brandes – Polis Project

Daren Carlisle – United State Geological Survey

Mary Fahey – Colusa County Resources Conservation District

Graham Fogg – University of California, Davis

Laura Foglia – University of California, Davis

Tom Gleeson – University of Victoria

Bea Gordon – Water in the West

Megan Glatzel – Water in the West

Mary Hill – University of Kansas

Jeanette Howard – The Nature Conservancy

Jay Jasperse – Sonoma County Water Agency

Ben Kerr – Foundry Spatial

Michael Kiparsky – UC Water

Rosemary Knight – Stanford Unviersity

Sally Liu – The Naturel Conservancy

Tara Moran – Water in the West

Howard Reeves – United States Geological Survey

Erik Ringleberg – Freshwater Trust

Melissa Rhode – The Nature Conservancy

Leon Szeptycki – Water in the West

Gus Tolley – University of California, Davis

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 12

APPENDIX B. WORKSHOP AGENDA

Tools and Methods for Assessing Groundwater-Surface Water Connectivity under SGMA

Stanford University March 12, 2018

Water in the West, the University of Victoria, Foundry Spatial, The Nature Conservancy, and the Environmental Defense Fund are co-hosting a workshop entitled, “Tools for Assessing Groundwater-Surface Water Connectivity under SGMA”. The full-day workshop will take place on March 12, 2018 from 8:30 am to 5 pm at Stanford University.

This workshop seeks to:

1. Engage with individuals and entities working on groundwater and surface water connectivity and groundwater dependent ecosystems under SGMA;

2. Examine recent research and tool development to assess research gaps and areas to coordinate or collaborate research effort to help address surface water depletions under SGMA; and

3. Where new research or tools are necessary, identify their potential role in water management decisions, the data needs, essential functionality, and potential users, locations and partners for pilot studies.

Meeting DetailsWhen: March 12, 2018 (1 day)Where: Room 299, Y2E2 Building, 473 Via Ortega, StanfordHotel: Stanford Guest House

Dinner DetailsWhen: March 12, 2018, 5:00 pmWhere: Tea Room, Shriram Building, 443 Via Ortega

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 13

AGENDA

Monday, March 12, 2018

8:15 – 9:00 Light Breakfast and Registration

9:00 – 9:20 Welcome and Introductions Leon Szeptycki, Water in the West Tara Moran, Water in the West Tom Gleeson, University of Victoria

9:20 – 10:25 Session 1: Why are we here? (65 mins) What are groundwater hydrologists, groundwater managers, the state and others most worried about with

respect to groundwater-surface water requirements under SGMA?

Moderator: Leon Szeptycki, Water in the West

Presentations:

• Groundwater-surface water connectivity in hydrologic science: Tom Gleeson, University of Victoria (15 mins)

• Legal and regulatory requirements of interconnected surface water under SGMA: Jessica Bean, California State Water Resources Control Board (15 mins)

• Navigating Groundwater-Surface Water Interactions under the Sustainable Groundwater Management Act: Michael Kiparksy, UC Water (15 mins)

Discussion (20 mins)

10:25 – 10:35 Time to fill out Session 1 questions

10:35 – 12:00 Session 2: Can we go with the flow, people? (85 mins) What are the concerns in considering multiple beneficial uses of interconnected surface waters under SGMA?

How can these approaches address these concerns? Where is additional work needed?

Moderator: Tara Moran, Water in the West

Presentations:

• A Framework for Unimpaired Minimum Streamflow Requirements: Daren Carlisle, United States Geological Survey (15 mins)

• EDF’s Proposed Approach for Compliance with Surface Water Depletion Requirements in SGMA: Christina Babbitt, Environmental Defense Fund (15 mins)

• California’s Groundwater Dependent Ecosystems: Jeanette Howard, The Nature Conservancy (15 mins)

Discussion (40 mins)

12:00 – 12:10 Time to fill out Session 2 questions

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 14

12:10 – 1:00 Lunch (50 mins)

1:00 – 2:40 Session 3: Tools of the trade (100 mins) How can we leverage existing data and knowledge to improve water literacy? Is there a role for screening level

tools, to support decision making and identification of where more complex field investigations and numerical modeling is needed?

Moderator: Mary Hill, The University of Kansas

Presentations:

• B.C. Water Tool: Ben Kerr, Foundry Spatial (30 mins)

• The Michigan Tool: Howard Reeves, United States Geological Survey (30 mins)

Discussion (40 mins)

2:40 – 2:50 Time to fill out Session 3 questions

2:50 – 3:10 Break (20 minutes)

3:10 – 4:20 Session 4: To model or not to model? (70 mins) What level of model complexity is necessary and useful for groundwater management decisions in different

hydrologic and institutional environments?

Moderator: Laura Foglia, University of California, Davis

Presentations:

• Comparison of Analytical and Numerical Models: Tom Gleeson, University of Victoria (15 mins)

• Lessons Learned from Groundwater Modeling in California and Beyond: Graham Fogg, University of California, Davis (15 mins)

Discussion (40 mins)

4:20 – 4:30 Time to fill out Session 3 questions

4:30 – 4:50 Summarize key findings and next steps (20 mins) Leon Szeptycki, Water in the West Tom Gleeson, University of Victoria

4:50 – 4:55 Wrap-up, next steps

4:55 – 5:00 Time to fill out wrap up questions

5:00 Reception and Dinner

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 15

APPENDIX C. WORKSHOP QUESTIONNAIRESession 11. What are you most worried about with respect to groundwater-surface water requirements under SGMA?

2. How do you anticipate addressing (or think GSAs should address) the concerns outlined above in groundwater sustainability plans under SGMA?

Session 21. What is appealing about the approaches presented during session 2?

2. Do you have outstanding questions about these approaches and their potential application?

Session 31. What is appealing about the tools presented during session 3 of the workshop?

2. Do you have outstanding questions about these tools and their potential application?

Session 41. What is appealing about:

a. Analytical models for addressing interconnected surface waters under SGMA?

b. Numerical models for addressing interconnected surface waters under SGMA?

2. Do you have outstanding questions about these models and their potential application under SGMA?

a. Analytical models

b. Numerical models

Wrap up1. After today’s meeting, what are you most worried about with respect to groundwater-surface water requirements under SGMA?

Have your concerns changed or remained the same? Why?

2. What would most help you or others best address this concern on the necessary timeline?

3. Can we reach out to you for additional information? If so, please include your name below and your areas of interest or technical expertise.

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 16

APPENDIX D. SUPPLEMENTARY TABLES Table D1. Legal and regulatory requirements for interconnected surface water under SGMA.

Legal requirements

GSPs must: • Avoid chronic lowering of groundwater levels that result in significant and unreasonable depletion of supply (CWC 10721(w)(1))

• Avoid depletions of interconnected surface waters that have significant and unreasonable adverse impacts on beneficial uses of the surface water (CWC 10721(w)(6))

• Include impacts on GDEs (CWC 10727.4(l))

• Develop monitoring and management protocols to detect changes in surface flow…(CWC 10727.2(d)(2))

Regulatory requirements

GSPs must: • Include a hydrogeologic conceptual model characterizing surface water-groundwater interactions (CCR 354.14)

• Identify interconnected surface waters in the basin, including estimates of quantity and timing of depletions (CCR 354.16(f)

• Include water budgets that include estimates of inflows and outflows to and from the groundwater systems by and to surface water systems (354.18(b)(2&3)); historical and projected groundwater and surface water interactions using a numerical model or an equally effective method, tool, or analytical model (CCR 354.18(e))

• Include minimum thresholds for depletions of interconnected surface water avoid undesirable results. Minimum thresholds must consider the location, quantity, and timing of depletions (CCR 354.28(c)(6))

• Include a monitoring network capable of demonstrating the hydraulic gradients between principal aquifers and surface water features using monitoring wells (CCR 354.34(c)(1)); characterizing spatial and temporal exchanges between surface water and groundwater, and sufficiently calibrate models used to determine the impact of groundwater pumping on surface water depletions (CCR 354.35(c)(6))

• Evaluate and modify monitoring protocols to ensure that adequate detail about “site-specific” surface water and groundwater conditions and assess the effectiveness of management actions including in highly variable spatial and temporal conditions (CCR 354.38)

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 17

Table D2. Regulatory code pertaining to the consideration of beneficial uses and users under SGMA

Table provided by Melissa Rohde, The Nature Conservancy.

GSP Regulation Section

Required Consideration of Beneficial Uses and Users in Groundwater Sustainability Plans

Beneficial Uses and Users

of Groundwater

of Surface Water

Admin InfoGSP Regulations §354.10 (a)Each Plan shall include a description of the beneficial uses and users of groundwater in the basin

Yes

Basin Setting

GSP Regulations §354.16(d)Each Plan shall provide a description of groundwater quality issues that may affect the supply and beneficial uses of groundwater

Yes

GSP Regulations §354.18(e)Each Plan shall rely on the best available information and science to quantify and evaluate projected water budget conditions and the potential impacts to beneficial uses and users of groundwater

Yes

Sustainable Management Criteria

GSP Regulations §354.26(b)(3)Each Plan shall describe potential effects on the beneficial uses and users of groundwater that may occur or are occurring from undesirable results

Yes

GSP Regulations §354.28(b)(4)Each Plan shall establish minimum thresholds that quantify groundwater conditions for each sustainability indicator and describe how minimum thresholds may affect the interests of beneficial uses and users of groundwater.

Yes

GSP Regulations §354.28 (c)(6)The minimum threshold for depletions of interconnected surface water shall be the rate or volume of surface water depletions caused by groundwater use that has adverse impacts on beneficial uses of the surface water and may lead to undesirable results

Yes

Monitoring Networks

GSP Regulations §354.34 (b)(2)Monitor impacts to the beneficial uses or users of groundwater Yes

GSP Regulations §354.34(c)(6)When establishing a monitoring network for Depletion of Interconnected Surface water, monitor factors that may be necessary to identify adverse impacts on beneficial uses of the surface water

Yes

GSP Regulations §354.34(f)(3)The density of monitoring sites and frequency of measurements required to demonstrate short-term, seasonal, and long-term trends are based shall be based upon impacts to beneficial uses and users of groundwater that could affect the ability of that basin to meet the sustainability goal

Yes

GSP Regulations §354.38(e)(3)The Monitoring frequency and density of monitoring sites shall be adjusted to provide an adequate level of detail about site-specific surface water and groundwater conditions to assess the effectiveness of management actions under circumstances where adverse impacts to beneficial uses and users of groundwater may exist

Yes

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 18

Tabl

e D3

. Ov

ervi

ew o

f too

ls a

nd a

ppro

ache

s fo

r as

sess

ing

inte

rcon

nect

ed s

urfa

ce w

ater

and

str

eam

flow

dep

letio

ns.

Tabl

e m

odifi

ed fr

om C

anto

r et a

l. (2

018)

.

Tool

s/M

etho

dsDe

scrip

tion

Appl

icat

ion/

Use

Case

Bene

fits/

Lim

itatio

nsCa

se S

tudi

es/K

ey R

efer

ence

s

Fiel

d-ba

sed

met

hods

Stre

amflo

w g

agin

gSt

ream

flow

mon

itorin

g pr

ovid

es a

co

ntin

uous

reco

rd o

f stre

am d

isch

arge

at

a p

artic

ular

site

ove

r tim

e. I

is

the

com

bine

d in

terp

reta

tion

of: 1

) st

ream

gag

ing

data

, a c

ontin

uous

m

easu

rem

ent o

f sur

face

wat

er

heig

ht a

long

a s

tream

or r

iver

, and

2)

dis

char

ge e

stim

ates

, per

iodi

c m

easu

rem

ents

of t

he v

olum

e of

wat

er

at a

spe

cific

loca

tion

alon

g a

stre

am,

whi

ch a

re re

late

d to

one

ano

ther

us

ing

a st

age-

disc

harg

e re

latio

nshi

p.

Stre

amflo

w m

easu

rem

ents

take

n at

tw

o or

mor

e si

tes

alon

g a

river

can

be

use

d to

est

imat

e st

ream

flow

gai

ns

or lo

sses

bet

wee

n m

easu

rem

ent

loca

tions

.

Stre

amflo

w d

ata

prov

ides

info

rmat

ion

foun

datio

nal

to u

nder

stan

ding

a s

urfa

ce w

ater

sys

tem

and

its

conn

ectio

n to

the

broa

der h

ydro

logi

c sy

stem

. It c

an

be u

sed:

1. A

s an

inpu

t in

hydr

olog

ic m

odel

s an

d fo

r mod

el

calib

ratio

n,

2. T

o de

term

inin

g im

pact

s of

gro

undw

ater

pum

ping

on

loca

l sur

face

wat

er b

odie

s,

3. T

o es

timat

e an

d m

onito

r sur

face

wat

er d

eple

tions

,

4. T

o m

onito

r stre

amflo

w fo

r aqu

atic

hea

lth (e

.g.

inst

ream

flow

requ

irem

ents

)

5. T

o es

timat

e ba

seflo

w, a

nd

6. T

o as

sess

the

impa

cts

of c

hang

ing

cond

ition

s on

a

stre

am (e

.g. g

roun

dwat

er p

umpi

ng, l

and

use

chan

ge, c

limat

e ch

ange

, etc

.) w

hen

mea

sure

d th

roug

h tim

e.

BEN

EFIT

S

1. R

elat

ivel

y si

mpl

e an

d lo

w c

ost i

f stre

amflo

w g

ages

al

read

y ex

ist a

t app

ropr

iate

loca

tions

, and

2. C

an p

rovi

de a

n es

timat

e of

stre

amflo

w

cont

ribut

ion

from

gro

undw

ater

.

LIM

ITAT

ION

S

1. R

equi

res

cont

inuo

us s

tream

gag

ing

at a

ppro

pria

te

(ofte

n m

ultip

le) l

ocat

ions

, whi

ch c

an b

e di

fficu

lt an

d ex

pens

ive

to m

aint

ain,

2. M

ay n

ot p

rovi

de a

full

pict

ure

of c

ompl

ex

grou

ndw

ater

dyn

amic

s, a

nd

3. C

hang

es in

the

syst

em m

ust b

e la

rger

than

m

easu

rem

ent a

ccur

acy

to b

e de

tect

ed.

Witt

enbe

rg, H

., &

Siva

pala

n, M

. (19

99).

Barlo

w a

nd L

eake

(201

2).

Grou

ndw

ater

leve

l m

onito

ring

The

long

-ter

m m

onito

ring

of

grou

ndw

ater

leve

ls (t

ypic

ally

via

a m

onito

ring

or p

rodu

ctio

n w

ell)

at a

pa

rtic

ular

loca

tion

over

tim

e.

Grou

ndw

ater

leve

l mon

itorin

g pr

ovid

es in

form

atio

n fo

unda

tiona

l to

unde

rsta

ndin

g a

grou

ndw

ater

sys

tem

an

d its

con

nect

ion

to th

e br

oade

r hyd

rolo

gic

syst

em.

Thes

e da

ta c

an:

1. B

e us

ed a

s an

inpu

t for

hyd

rolo

gic

mod

els

and

for

mod

el c

alib

ratio

n,

2. M

onito

r cha

nge

in g

roun

dwat

er le

vels

thro

ugh

time,

3. B

e co

mbi

ned

with

gro

undw

ater

leve

ls th

roug

hout

th

e ba

sin

to d

eter

min

e hy

drau

lic g

radi

ents

and

flo

w p

atte

rns,

4. B

e co

mbi

ned

with

gro

undw

ater

pum

p te

sts

to

dete

rmin

e hy

drau

lic c

ondu

ctiv

ity,

5. B

e co

mbi

ned

with

stre

amflo

w m

onito

ring

to

asse

ss th

e de

gree

of h

ydro

logi

c co

nnec

tivity

be

twee

n sy

stem

s, a

nd

6. B

e co

mbi

ned

with

stre

amflo

w m

onito

ring

to

asse

ss th

e im

pact

s of

gro

undw

ater

pum

ping

on

surf

ace

wat

er d

eple

tions

.

BEN

EFIT

S

1. R

elat

ivel

y si

mpl

e an

d lo

w c

ost i

f exi

stin

g m

onito

ring

netw

ork

is s

uffic

ient

, and

2. U

sefu

l for

mon

itorin

g lo

ng-t

erm

tren

ds a

nd

impa

cts

to b

enefi

cial

use

rs w

hen

com

bine

d w

ith

othe

r app

roac

hes.

LIM

ITAT

ION

S

1. M

ay b

e ov

erly

sim

ple

for a

ll an

alys

es, p

artic

ular

ly w

here

hig

h sp

atia

l and

tem

pora

l inf

orm

atio

n ab

out

inte

rcon

nect

ed s

urfa

ce w

ater

is re

quire

d,

2. H

ighl

y de

pend

ent o

n th

e qu

ality

of t

he m

onito

ring

netw

ork,

incl

udin

g th

e ty

pes

of w

ells

bei

ng

mon

itore

d, th

e sp

atia

l cov

erag

e of

the

wel

ls, t

he

tem

pora

l mon

itorin

g fre

quen

cy, d

ista

nce

from

su

rfac

e w

ater

bod

ies,

and

the

com

plex

ity o

f the

sy

stem

, and

3. M

ay n

ot a

ccou

nt fo

r tim

e la

gs in

gro

undw

ater

pu

mpi

ng.

Hall

et a

l. (2

018)

.

Curr

ell,

M.J

. (20

16).

Rose

nber

ry e

t al.,

(200

8).

Tayl

or, C

. J.,

& Al

ley,

W. M

. (20

01).

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 19

Tool

s/M

etho

dsDe

scrip

tion

Appl

icat

ion/

Use

Case

Bene

fits/

Lim

itatio

nsCa

se S

tudi

es/K

ey R

efer

ence

s

Seep

age

met

ers

Seep

age

met

ers

mea

sure

the

exch

ange

of w

ater

bet

wee

n su

rfac

e w

ater

bod

ies

and

grou

ndw

ater

at a

po

int o

r site

sca

le.

Seep

age

met

ers

can:

1. M

easu

re fl

uxes

bet

wee

n su

rfac

e w

ater

bod

ies

and

grou

ndw

ater

,

2. M

easu

re lo

sses

from

unl

ined

irrig

atio

n ca

nals

,

3. M

onito

r sur

face

wat

er d

eple

tion,

and

4. B

e co

mbi

ned

with

dat

a fro

m h

ydra

ulic

po

tent

iom

eter

s (s

ee b

elow

) to

estim

ate

loca

l-sca

le

vert

ical

hyd

raul

ic c

ondu

ctiv

ity.

BEN

EFIT

S

1. L

ow c

ost a

nd s

impl

e to

use

.

LIM

ITAT

ION

S

1. N

umer

ous

sour

ces

of e

rror

exi

st,

2. N

ot w

ell s

uite

d fo

r sur

face

wat

er b

odie

s w

ith

curr

ents

or f

ast w

ater

, roc

ky s

edim

ent,

or v

ery

soft

sedi

men

t, an

d

3. P

rovi

des

loca

lized

info

rmat

ion

that

can

not

gene

rally

be

appl

ied

mor

e br

oadl

y.

Rose

nber

ry e

t al.,

(200

8).

Hydr

aulic

po

tent

iom

eter

sHy

drau

lic p

oten

tiom

eter

s pr

ovid

e an

est

imat

e of

loca

l-sca

le v

ertic

al

hydr

aulic

con

duct

ivity

in s

urfa

ce w

ater

bo

dy s

edim

ents

.

Hydr

aulic

pot

entio

met

ers

can:

1. P

rovi

de in

form

atio

n ab

out r

elat

ive

chan

ges

in

loca

l-sca

le, v

ertic

al h

ydra

ulic

con

duct

ivity

in

sedi

men

ts o

f a s

urfa

ce w

ater

bod

y, a

nd

2. B

e co

mbi

ned

with

mea

sure

men

ts fr

om a

see

page

m

eter

(see

abo

ve) t

o es

timat

e lo

cal-s

cale

hy

drau

lic c

ondu

ctiv

ity.

BEN

EFIT

S

1. P

rovi

des

insi

ght i

nto

rela

tive

varia

tion

in v

ertic

al

hydr

aulic

con

duct

ivity

in s

edim

ents

bel

ow s

urfa

ce

wat

er b

odie

s, a

nd

2. C

an b

e co

mbi

ned

with

see

page

met

ers

to e

stim

ate

flux.

LIM

ITAT

ION

S

1. N

umer

ous

sour

ces

of e

rror

exi

st,

2. N

ot w

ell s

uite

d fo

r fas

t flow

ing

wat

ers

or s

urfa

ce

wat

er b

odie

s w

ith s

igni

fican

t wav

e ac

tion,

3. B

est s

uite

d fo

r use

as

a re

conn

aiss

ance

tool

.

Rose

nber

ry e

t al.,

(200

8).

Fibe

r opt

ic

dist

ribut

ed

tem

pera

ture

se

nsor

s

Fibe

r opt

ic te

mpe

ratu

re s

enso

rs a

re

depl

oyed

as

long

cab

les

alon

g th

e ba

se

of th

e riv

er o

r stre

am o

r oth

er s

urfa

ce

wat

er b

ody.

Con

tinuo

us te

mpe

ratu

re

mea

sure

men

ts a

long

the

leng

th o

f th

e ca

ble

can

be u

sed

to e

stim

ate

grou

ndw

ater

dis

char

ge, w

hich

ge

nera

lly h

as a

dis

tinct

tem

pera

ture

si

gnal

from

the

surf

ace

wat

er, i

nto

the

surf

ace

wat

er s

yste

m.

Fibe

r opt

ic te

mpe

ratu

re s

enso

r can

:

1. I

dent

ify g

aini

ng re

ache

s in

inte

rcon

nect

ed

syst

ems,

2. P

rovi

de b

asel

ine

info

rmat

ion

abou

t a g

iven

sys

tem

an

d ho

w it

cha

nges

thro

ugh

time.

BEN

EFIT

S

1. R

eal-t

ime,

hig

h re

solu

tion

data

col

lect

ion,

and

2. T

rack

s m

ovem

ent o

f gro

undw

ater

thro

ugh

a co

nnec

ted

syst

em in

com

bina

tion

with

oth

er

met

hods

.

LIM

ITAT

ION

S

1. D

eplo

ymen

t can

be

chal

leng

ing

depe

ndin

g on

the

natu

re o

f the

sys

tem

and

may

resu

lt in

dis

turb

ance

to

the

sedi

men

ts, a

nd

2. C

an b

e la

bor-

inte

nsiv

e to

inst

all.

Mw

akan

yam

ale

et a

l. (2

012)

.

Slat

er e

t al.

(201

0).

Ons

ite im

ager

yPh

otog

raph

s of

the

sam

e lo

catio

n ov

er

time

to tr

ack

chan

ges

in in

frast

ruct

ure,

ph

enol

ogy

of v

eget

atio

n as

a p

roxy

fo

r gro

undw

ater

, and

oth

er re

leva

nt

para

met

ers

at a

site

sca

le.

Ons

ite im

ager

y ca

n:

1. B

e us

ed to

gro

und-

truth

rem

ote

sens

ing-

base

d da

ta, a

nd

2. P

rovi

de b

asel

ine

info

rmat

ion

abou

t a g

iven

sys

tem

an

d ho

w it

cha

nges

thro

ugh

time

if ph

otos

are

ta

ken

at th

e sa

me

loca

tion

thro

ugh

time.

BEN

EFIT

S

1. S

impl

e an

d in

tuiti

ve fo

r man

y us

ers

sinc

e it

requ

ires

very

littl

e ex

pert

ise

to o

btai

n pi

ctur

es.

LIM

ITAT

ION

S

1. S

mal

l sca

le o

bser

vatio

n m

ay b

e di

fficu

lt to

ex

trapo

late

ove

r lar

ger a

reas

.

Tabl

e D3

(con

tinue

d)

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 20

Tool

s/M

etho

dsDe

scrip

tion

Appl

icat

ion/

Use

Case

Bene

fits/

Lim

itatio

nsCa

se S

tudi

es/K

ey R

efer

ence

s

Hand

held

ther

mal

im

agin

g ca

mer

asHa

ndhe

ld th

erm

al im

agin

g ca

mer

as

can

be u

sed

to im

age

stre

ams

and

lake

s an

d to

loca

te v

aria

tions

in

tem

pera

ture

. Thi

s in

form

atio

n ca

n th

en b

e us

ed to

trac

e gr

ound

wat

er

disc

harg

e in

to a

stre

am.

Ther

mal

imag

ing

cam

eras

can

:

1. H

elp

iden

tify

gain

ing

reac

hes

in in

terc

onne

cted

sy

stem

s,

2. B

e us

ed to

gro

und-

truth

rem

ote

sens

ing-

base

d da

ta,

3. O

ptim

ize th

e lo

catio

n of

mor

e in

volv

ed s

tudi

es o

f in

terc

onne

cted

sur

face

wat

er, a

nd

4. P

rovi

de b

asel

ine

info

rmat

ion

abou

t a g

iven

sys

tem

an

d ho

w it

cha

nges

thro

ugh

time

if ph

otos

are

ta

ken

at th

e sa

me

loca

tion

thro

ugh

time.

BEN

EFIT

S

1. Q

uick

dat

a co

llect

ion,

and

2. C

an b

e us

ed in

diffi

cult-

to-a

cces

s ar

eas.

LIM

ITAT

ION

S

1. B

est s

uite

d fo

r use

as

a re

conn

aiss

ance

tool

.

USG

S, H

ydro

geop

hysi

cs B

ranc

h.

Brig

gs e

t al.

(201

3).

In-s

itu s

oil o

r ve

geta

tion

surv

eys

Vege

tatio

n an

d so

il su

rvey

s ar

e ty

pica

lly c

ondu

cted

to c

hara

cter

ize

plan

t and

or s

oil t

ypes

in a

spe

cific

ar

ea (e

.g.,

a w

etla

nd o

r an

upla

nd a

t th

e si

te o

r stre

am re

ach

scal

e).

In-s

itu s

oil a

nd v

eget

atio

n su

rvey

s ca

n:

1. B

e us

ed to

iden

tify

and

char

acte

rize

ripar

ian

spec

ies

or h

abita

ts th

at m

ay b

e to

o fin

e fo

r oth

er

met

hods

to re

solv

e, a

nd

2. G

roun

d-tru

th re

mot

e-se

nsin

g da

ta.

BEN

EFIT

S

1. P

rovi

des

expl

icit

insi

ght i

nto

loca

l veg

etat

ion

and

soil

char

acte

ristic

s, a

nd

2. I

ncre

ases

con

fiden

ce in

rem

ote-

sens

ing

base

d m

etho

ds.

LIM

ITAT

ION

S

1. R

esou

rce

inte

nsiv

e,

2. S

ubje

ct to

sam

plin

g an

d hu

man

err

or.

Isot

opes

and

trac

ers

Stab

le a

nd

radi

oact

ive

isot

opes

Stab

le a

nd ra

dioa

ctiv

e is

otop

e co

mpa

res

the

uniq

ue is

otop

ic s

igna

ture

of

sam

pled

wat

er a

gain

st th

e un

ique

is

otop

ic s

igna

ture

s of

pre

cipi

tatio

n an

d an

y ad

jace

nt s

urfa

ce w

ater

sou

rces

to

dete

rmin

e th

e so

urce

of t

he s

ampl

ed

wat

er. I

n th

is w

ay, i

soto

pic

sign

atur

e ca

n al

so b

e us

ed to

trac

k flo

w d

irect

ion

at a

var

iety

of s

cale

s (e

.g. s

ite, s

tream

re

ach,

bas

in, a

nd re

gion

).

Stab

le a

nd ra

dioa

ctiv

e is

otop

es a

re n

eces

sary

/re

com

men

ded

for:

1. T

rack

ing

grou

ndw

ater

flow

rate

s, c

ontri

butio

ns,

and

sour

ce,

2. E

stab

lishi

ng a

site

-spe

cific

geo

chem

ical

bas

elin

e fo

r fur

ther

ana

lyse

s,

3. E

stab

lishi

ng s

ourc

e in

puts

for d

iffer

ent t

ypes

of

mod

els,

and

4. D

eter

min

ing

rela

tive

cont

ribut

ion

of d

iffer

ent

sour

ces

to b

asefl

ow, i

n co

mbi

natio

n w

ith o

ther

to

ols

(e.g

. stre

amflo

w g

agin

g)

BEN

EFIT

S

1. T

rack

s m

ovem

ent o

f gro

undw

ater

thro

ugh

a co

nnec

ted

syst

em in

com

bina

tion

with

oth

er

met

hods

.

LIM

ITAT

ION

S

1. P

ossi

ble

need

for m

ore

sign

ifica

nt ti

me

and

mon

ey

to c

aptu

re te

mpo

ral a

nd s

patia

l res

olut

ion.

USG

S, R

esou

rces

on

Isot

opes

.

Philli

ps. (

1995

).

Tabl

e D3

(con

tinue

d)

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 21

Tool

s/M

etho

dsDe

scrip

tion

Appl

icat

ion/

Use

Case

Bene

fits/

Lim

itatio

nsCa

se S

tudi

es/K

ey R

efer

ence

s

Trac

er te

sts

Trac

er te

sts

add

trace

rs (e

.g. d

yes

and

salts

) a w

ater

bod

y to

det

erm

ine

flow

ra

tes,

cha

ract

erize

flow

pat

hs, s

ourc

e an

d de

stin

atio

n, a

nd d

eter

min

e m

ixin

g ra

tes.

Trac

er te

sts

can:

1. P

rovi

de e

stim

ates

of fl

ow ra

te,

2. P

rovi

de in

sigh

t int

o flo

w p

athw

ays,

wat

er s

ourc

es

and

dest

inat

ion,

3. D

eter

min

e m

ixin

g ra

tes,

and

4. B

e co

mbi

ned

with

oth

er m

etho

ds to

pro

vide

es

timat

es o

f res

iden

ce ti

me

at a

var

iety

of s

cale

s.

BEN

EFIT

S

1. C

an p

rovi

de d

irect

est

imat

es o

f flow

rate

an

d de

gree

of c

onne

ctiv

ity in

inte

rcon

nect

ed

hydr

olog

ic s

yste

ms.

LIM

ITAT

ION

S

1. B

est u

sed

in a

sys

tem

with

fast

resp

onse

tim

es,

2. P

rope

r tra

cer p

repa

ratio

n is

ess

entia

l, an

d

3. T

race

r ana

lysi

s m

ust b

e co

mpa

red

agai

nst

base

line

cond

ition

s.

Tayl

or a

nd G

reen

e. (2

008)

.

Geop

hysi

cal m

easu

rem

ents

, rem

ote

sens

ing,

map

ping

, and

imag

ery

Rem

ote

sens

ing

of

vege

tatio

nRe

mot

e se

nsin

g br

oadl

y re

fers

to a

ny

data

col

lect

ion

tech

niqu

e th

at d

oes

not r

equi

re th

e us

er to

be

phys

ical

ly pr

esen

t. Fo

r int

erco

nnec

ted

surf

ace

wat

er, r

emot

e se

nsin

g ha

s pr

imar

ily

focu

sed

on m

appi

ng o

f sur

face

-bas

ed

indi

cato

rs li

ke v

eget

atio

n (s

ee m

appi

ng

grou

ndw

ater

dep

ende

nt e

cosy

stem

s be

low

). Su

rvey

s ca

n be

con

duct

ed

at a

var

iety

of s

cale

s an

d re

sulti

ng

reso

lutio

ns, i

nclu

ding

by

dron

e an

d ai

rbor

ne a

nd s

pace

-bas

ed s

atel

lites

.

Rem

ote

sens

ing

can:

1. H

elp

iden

tify

and

mon

itor i

mpa

cts

on g

roun

dwat

er

depe

nden

t veg

etat

ion,

and

2. P

rovi

de a

n es

timat

e of

pla

nt h

ealth

, whi

ch c

an

serv

e as

a p

roxy

for g

roun

dwat

er le

vels

.

BEN

EFIT

S

1. P

rovi

des

data

at a

var

iety

of s

cale

s, d

epen

ding

on

met

hods

use

d,

2. C

an b

e lo

w o

r hig

h-co

st, d

epen

ding

on

met

hods

us

ed, a

nd

3. S

atel

lite

data

can

pro

vide

s hi

stor

ical

dat

a in

som

e ca

ses.

LIM

ITAT

ION

S

1. C

an b

e di

fficu

lt to

inte

rpre

t and

requ

ires

grou

nd-

truth

ing,

and

2. S

patia

l and

tem

pora

l cov

erag

e m

ay b

e lim

ited

for

som

e sa

tellit

e da

ta.

Eam

us e

t al.

(201

5).

Pai e

t al.

(201

7).

Map

ping

of

grou

ndw

ater

de

pend

ent

ecos

yste

ms

Iden

tifica

tion

of g

roun

dwat

er

depe

nden

t eco

syst

ems

(GDE

s) c

an

be d

one

usin

g a

varie

ty o

f met

hods

, in

clud

ing

diur

nal g

roun

dwat

er le

vel

fluct

uatio

ns, i

soto

pic

anal

ysis

, rem

ote

sens

ing

data

, and

the

com

pila

tion

of

vege

tatio

n da

tase

ts w

ith lo

cal g

eolo

gy

and

grou

ndw

ater

dep

th. S

tate

wid

e m

appi

ng o

f GDE

s in

Cal

iforn

ia b

y Th

e Na

ture

Con

serv

ancy

was

don

e us

ing

latte

r met

hods

.

GDE

map

ping

can

:

1. T

o id

entif

y an

d m

onito

r are

as in

terc

onne

cted

su

rfac

e w

ater

and

gai

ning

and

losi

ng re

ache

s, a

nd

2. M

onito

r GDE

s ov

er ti

me.

BEN

EFIT

S

1. P

rovi

des

a fir

st-o

rder

est

imat

e of

GDE

loca

tions

ac

ross

the

stat

e.

LIM

ITAT

ION

S

1. R

equi

re g

roun

dtru

thin

g an

d su

pple

men

tal

anal

ysis

via

veg

etat

ion

and

faun

a su

rvey

s or

oth

er

met

hods

.

TNC,

The

Gro

undw

ater

Res

ourc

e Hu

b.

Rohd

e et

al.

(201

7).

Klau

smey

er e

t al.

(201

0).

Tabl

e D3

(con

tinue

d)

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 22

Tool

s/M

etho

dsDe

scrip

tion

Appl

icat

ion/

Use

Case

Bene

fits/

Lim

itatio

nsCa

se S

tudi

es/K

ey R

efer

ence

s

Elec

trica

l Res

istiv

ityEl

ectri

cal r

esis

tivity

is a

tech

nolo

gy th

at

uses

ele

ctro

mag

netic

pro

pert

ies

of th

e so

il to

map

out

sub

surf

ace

elec

trica

l pr

oper

ties,

whi

ch c

an b

e in

terp

rete

d to

gi

ve g

eolo

gy a

nd s

ubsu

rfac

e st

ruct

ure.

Elec

trica

l res

istiv

ity c

an:

1. E

stim

ate

dept

h to

the

wat

er ta

ble,

2. I

mag

e th

e sa

lt an

d fre

shw

ater

inte

rfac

e,

3. P

rovi

de in

sigh

t int

o th

e de

gree

of c

onne

ctiv

ity

betw

een

surf

ace

wat

er a

nd g

roun

dwat

er s

yste

ms,

an

d

4. B

e co

mbi

ned

with

lith

olog

ical

, phy

sioc

hem

ical

, an

d ge

olog

ical

info

rmat

ion

to d

evel

op a

det

aile

d hy

drog

eolo

gica

l mod

el.

BEN

EFIT

S

1. P

rovi

des

non-

inva

sive

imag

es o

f the

sub

surf

ace.

LIM

ITAT

ION

S

1. R

equi

res

litho

logi

cal r

ecor

ds fr

om b

oreh

oles

for

inte

rpre

tatio

n,

2. R

equi

res

expe

rtis

e to

inte

rpre

t res

ults

, and

3. I

t can

be

diffi

cult

to d

iffer

entia

te c

hang

es

in li

thol

ogy

with

cha

nges

in m

oist

ure

valu

es

part

icul

arly

in a

reas

with

bra

ckis

h or

sal

ine

wat

er.

USG

S, H

ydro

geop

hysi

cs B

ranc

h.

Card

enas

and

Mar

kow

ski.

(201

1).

Mw

akan

yam

ale

et a

l. (2

012)

.

Syst

em-b

ased

app

roac

hes

Wat

er B

alan

ceA

wat

er b

alan

ce is

an

acco

untin

g of

al

l infl

ows

and

outfl

ows

of w

ater

in

a sy

stem

. Key

com

pone

nts

of th

e w

ater

bal

ance

(e.g

. gro

undw

ater

co

ntrib

utio

n, s

tora

ge, e

tc.)

can

be

isol

ated

for f

urth

er a

naly

sis.

Wat

er b

alan

ces

can:

1. P

rovi

de in

sigh

t int

o th

e do

min

ant h

ydro

logi

c pr

oces

ses

influ

enci

ng a

sys

tem

(e.g

., su

rfac

e w

ater

con

tribu

tions

, gro

undw

ater

pum

ping

, re

char

ge),

2. P

rovi

de in

sigh

t int

o th

e im

pact

s of

pro

ject

, clim

ate

chan

ge a

nd h

uman

impa

cts

whe

n ca

lcul

ated

and

co

mpa

red

thro

ugh

time,

3. H

elp

iden

tify

area

s of

unc

erta

inty

in th

e sy

stem

,

4. H

elp

to a

sses

s sp

atia

l and

tem

pora

l gro

undw

ater

-su

rfac

e w

ater

flow

dyn

amic

s; a

nd

5. A

ssis

t in

dete

rmin

ing

grou

ndw

ater

con

tribu

tion

(via

the

bala

nce

of in

puts

and

out

puts

) and

gai

ning

an

d lo

sing

reac

hes

in a

sys

tem

.

BEN

EFIT

S

1. R

elat

ivel

y si

mpl

e an

d lo

w c

ost,

but t

he c

ompl

exity

of

eac

h w

ater

bud

get c

an v

ary

subs

tant

ially

.

LIM

ITAT

ION

S

1. M

ay n

ot p

rovi

de a

full

pict

ure

of c

ompl

ex

grou

ndw

ater

dyn

amic

s, a

nd

2. R

elie

s up

on a

ccur

ate

wat

er b

alan

ce d

ata,

whi

ch

may

be

limite

d.

Heal

y et

al.

(200

7).

Ruud

et a

l. (2

004)

.

Tabl

e D3

(con

tinue

d)

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 23

Tool

s/M

etho

dsDe

scrip

tion

Appl

icat

ion/

Use

Case

Bene

fits/

Lim

itatio

nsCa

se S

tudi

es/K

ey R

efer

ence

s

Anal

ytic

al M

odel

sAn

alyt

ical

mod

els

rely

on s

igni

fican

t si

mpl

ifica

tions

of t

he s

yste

m (e

.g.,

linea

r stre

ams

of in

finite

leng

th,

fully

pen

etra

ting

stre

ambe

ds,

hom

ogen

ous

aqui

fers

, a s

ingl

e w

ell)

to

mat

hem

atic

ally

solv

e th

e gr

ound

wat

er

flow

equ

atio

n. T

hese

mod

els

are

rela

tivel

y si

mpl

e to

run

and

prov

ide

a go

od in

itial

est

imat

e of

a s

yste

m a

t the

re

ach

or b

asin

sca

le. M

ore

com

plex

an

alyt

ical

mod

els

have

bee

n de

velo

ped

for s

emi-c

onfin

ed a

nd la

yere

d aq

uife

rs,

part

ially

pen

etra

ting

stre

ambe

ds, a

nd

mul

tiple

wel

ls.

Anal

ytic

al m

odel

s ca

n:

1. P

rovi

de in

sigh

t int

o do

min

ant h

ydro

logi

c pr

oces

s go

vern

ing

a sy

stem

,

2. P

rovi

de a

goo

d in

itial

est

imat

e of

pum

ping

impa

cts

on s

tream

flow

, and

3. B

e de

velo

ped

in a

reas

with

lim

ited

data

and

re

sour

ces.

BEN

EFIT

S

1. A

llow

s fo

r bas

ic m

odel

ing

of s

tream

dep

letio

n,

2. S

impl

er a

nd lo

wer

cos

t tha

n a

num

eric

al m

odel

,

3. P

rovi

des

good

wor

king

kno

wle

dge

of tr

ends

and

ov

eral

l im

pact

s, a

nd

4. C

an b

e de

velo

ped

with

lim

ited

data

.

LIM

ITAT

ION

S

1. R

equi

res

sign

ifica

nt s

impl

ifyin

g as

sum

ptio

ns th

at

limit

pred

ictiv

e ca

pabi

litie

s, a

nd

2. B

est s

uite

d fo

r min

imal

ly de

velo

ped

syst

ems

or

syst

ems

with

lim

ited

data

or r

esou

rces

.

Oki

and

Mey

er. (

2001

).

Hugg

ins

et a

l. (2

018)

.

Num

eric

al M

odel

sNu

mer

ical

mod

els

are

com

pute

r m

odel

s of

a g

roun

dwat

er s

yste

m o

r in

tegr

ated

hyd

rolo

gic

syst

em th

at

allo

w fo

r irr

egul

ar g

roun

dwat

er b

asin

bo

unda

ries,

irre

gula

r stre

am o

r riv

er

geom

etry

, com

plex

pum

ping

sch

edul

es

at m

ultip

le w

ells

, and

cha

ngin

g bo

unda

ry c

ondi

tions

. Sim

ulat

ed re

sults

ca

n be

use

d to

ana

lyze

diff

eren

t m

anag

emen

t sce

nario

s as

wel

l as

test

hy

poth

eses

at t

he s

tream

reac

h, b

asin

, an

d re

gion

sca

le.

Num

eric

al m

odes

can

:

1. P

rovi

de in

sigh

t int

o do

min

ant p

roce

ss g

over

ning

a

syst

em,

2. B

e us

ed to

iden

tify

gain

ing

and

losi

ng re

ache

s in

a

syst

em a

nd m

odel

cha

nges

thro

ugh

time,

and

3. S

imul

ate

chan

ges

to th

e sy

stem

resu

lting

from

pr

ojec

ts (e

.g.,

rech

arge

bas

ins)

, lan

d us

e, c

limat

e ch

ange

or o

ther

fact

ors,

whe

n w

ell c

alib

rate

d.

BEN

EFIT

S

1. P

rovi

des

for t

he s

imul

atio

n an

d pr

edic

tion

of

the

mod

eled

sys

tem

, inc

ludi

ng c

hang

es in

in

terc

onne

cted

sur

face

wat

ers,

and

2. A

ccou

nts

for t

hree

-dim

ensi

onal

com

plex

ity o

f gr

ound

wat

er s

yste

m.

LIM

ITAT

ION

S

1. A

ccur

acy

depe

nds

on q

ualit

y of

inpu

t dat

a,

2. R

equi

res

high

qua

lity

data

with

a lo

ng re

cord

for

pred

ictiv

e ca

pabi

litie

s, a

nd

3. C

an b

e ex

pens

ive

and

labo

r int

ensi

ve to

dev

elop

an

d m

aint

ain.

Barlo

w a

nd L

eake

. (20

12).

Mor

an (2

016)

.

Flec

kens

tein

et a

l. (2

006)

.

Resp

onse

Fun

ctio

ns

and

Capt

ure

Map

sAn

alyt

ical

and

num

eric

al m

odel

s ca

n ge

nera

te s

tream

flow

-dep

letio

n re

spon

se fu

nctio

ns a

nd c

aptu

re m

aps,

w

hich

cha

ract

erize

the

rela

tions

hip

betw

een

loca

lized

pum

ping

in a

n aq

uife

r and

nea

rby

stre

am d

eple

tion.

Resp

onse

func

tions

and

cap

ture

map

s ca

n:

1. P

rovi

de in

sigh

t int

o ho

w a

stre

am o

r stre

am re

ach

is li

kely

to re

spon

d to

pum

ping

at a

par

ticul

ar

wel

l.

BEN

EFIT

S

1. P

rovi

de in

sigh

ts in

to th

e re

latio

nshi

p be

twee

n gr

ound

wat

er p

umpi

ng a

nd s

tream

flow

that

may

be

diffi

cult

to a

chie

ve v

ia m

onito

ring.

LIM

ITAT

ION

S

1. A

ccur

acy

depe

nds

upon

qua

lity

of in

put d

ata

and

mod

el c

alib

ratio

n, a

nd

2. D

ifficu

lty in

sep

arat

ing

depl

etio

n ch

ange

s fro

m

stre

amflo

w re

spon

ses

to o

ther

cha

nges

(e.g

., cl

imat

e, s

urfa

ce w

ater

div

ersi

ons

upst

ream

).

Barlo

w a

nd L

eake

. (20

12).

Fogl

ia, L

., et

al.

(201

3).

Tabl

e D3

(con

tinue

d)

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 24

Table D3. References

Barlow, P. M., & Leake, S. A. (2012). Streamflow depletion by wells: understanding and managing the effects of groundwater pumping on streamflow. U.S. Geological Survey Circular 1376. Available at: https://pubs.usgs.gov/circ/1376/.

Briggs, M.A., Voytek, E.B., Day-Lewis, F.D, Rosenberry, D.O., and Lane, J.W. (2013). The hydrodynamic controls on thermal refugia for endangered mussels in the Delaware River. Environmental Sciences and Technology, 47(20):11423-11431. doi:10.1021/es4018893.

Cardenas, M.B. and M. S. Markowski. (2011). Geoelectrical imaging of hyporheic exchange and mixing of river water and groundwater in a large regulated river. Environmental Science & Technology, 45(4): 1407-1411. doi: 10.1021/es103438a.

Currell, M.J. (2016). Drawdown “Triggers”: A Misguided Strategy for Protecting Groundwater-Fed Streams and Springs. Groundwater, 54(5): 619-622. doi:10.1111/gwat.12425.

Eamus, D., S. Zolfaghar, R. Villalobos-Vega, J. Cleverly, and A. Huete. (2015). Groundwater-dependent ecosystems: recent insights from satellite and field-based studies. Hydrology and Earth System Sciences, 19:4229-4256. doi:10.5194/hess-19-4229-2015.

Flickenstein, J.H., R.G. Niswonger, and G.E. Fogg. (2006). River-aquifer interactions, geologic heterogeneity, and low-flow management. Groundwater, 44(6);837-852. doi:10.1111/j.1745-6584.2006.00190.x.

Foglia, L. A. McNally, T. Harter. (2013). Coupling a spatiotemporally distributed soil water budget with stream-depletion functions to inform stakeholder-driven management of groundwater-dependent ecosystems. Water Resources Research, 49(11):7292-7310. doi.org/10.1002/wrcr.20555.

Hall, M., C. Babbitt, A. Saracino, and S. Leake. (2018). Addressing Regional Surface Water Depletions in California: A Proposed Approach for Compliance with the SGMA. Environmental Defense Fund, San Francisco, CA. Available at: https://www.edf.org/sites/default/files/documents/edf_california_sgma_surface_water.pdf?_ga=2.85387929.1406725339.1535393826-1822091738.1533678174.

Healy, R.W., T.C. Winter, J.W. LaBaugh, and O.L. Franke. (2007). Water Budgets: Foundations for Effective Water-Resources and Environmental Management. U.S. Geological Survey Circular 1308. Available at: https://water.usgs.gov/watercensus/AdHocComm/Background/WaterBudgets-FoundationsforEffectiveWater-ResourcesandEnvironmentalManagement.pdf.

Huggins, X., Gleeson, T., Eckstrand, H., & Kerr, B. (2018). Streamflow Depletion Modeling: Methods for an Adaptable and Conjunctive Water Management Decision Support Tool. Journal of the American Water Resources Association, 54(5), 1024-1038. doi.org/10.1111/1752-1688.12659.

Klausmeyer K., J. Howard, T. Keeler-Wolf, K. Davis-Fadtke, R. Hull, A. Lyons. (2018). Mapping Indicators of Groundwater Dependent Ecosystems in California: Methods Report. San Francisco, CA. Available at: https://groundwaterresourcehub.org/public/uploads/pdfs/iGDE_data_paper_20180423.pdf.

Moran, T. (2016). Projecting Forward: A Framework for Groundwater Model Development Under the Sustainable Groundwater Management Act. Stanford University, Water in the West, Stanford, CA. Available at: http://waterinthewest.stanford.edu/sites/default/files/Groundwater-Model-Report.pdf

Mwakanyamale, K., Slater, L., Day-Lewis, F.D., Elwaseif, M., Ntarlagiannis, D., and Johnson, C.D. (2012). Spatially variable stage-driven groundwater-surface water interaction inferred from time-frequency analysis of distributed temperature sensing data. Geophysical Research Letters, doi:10.1029/2011GL050824.

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 25

Oki, D.S. and W. Meyer. (2001). Analytical versus numerical estimates of water-level declines caused by pumping , and a case study of the Iao Aquifer, Maui, Hawaii. U.S. Geological Survey Water-Resources Investigations Report 00-4244. Available at: https://pubs.usgs.gov/wri/wri00-4244/pdf/wri00-4244.pdf.

Pai, H., H.F. Malenda, M.A. Briggs, K. Singha, R. González-Pinzón, M.N. Gooseff, S.W. Tyler, and the AirCTEMPS Team. (2017). Potential for small unmanned aircraft systems Applications for Identifying Groundwater-Surface Water Exchange in a Meandering River Reach. Geophysical Research Letters, 44(23):11868-11877. doi:10.1002/2017GL075836.

Phillips, F.M. (1995). The use of isotopes and tracers in subsurface hydrology. Reviews of Geophysics, 33(52): 1029-1033. doi.org/10.1029/95RG00247.

Rohde, M. M., S. Matsumoto, J. Howard, S. Liu, L. Riege, and E. J. Remson. (2018). Groundwater Dependent Ecosystems under the Sustainable Groundwater Management Act: Guidance for Preparing Groundwater Sustainability Plans. The Nature Conservancy, San Francisco, CA. Available at: https://groundwaterresourcehub.org/public/uploads/pdfs/GWR_Hub_GDE_Guidance_Doc_2-1-18.pdf.

Rosenberry, D. O., LaBaugh, J. W., and R.J. Hunt. (2008). Chapter 2: Use of monitoring wells, portable piezometers, and seepage meters to quantify flow between surface water and ground water, In: Field techniques for estimating water fluxes between surface water and ground water. U.S. Geological Survey Techniques and Methods 4-D2. Available at: https://pubs.usgs.gov/tm/04d02/pdf/TM4-D2-chap2.pdf.

Rosenberry, D. O., & LaBaugh, J. W. (2008). Field techniques for estimating water fluxes between surface water and ground water, U.S. Geological Survey Techniques and Methods 4-D2. Available at: https://pubs.usgs.gov/tm/04d02/.

Rudd, N., T. Harter, and A. Naugle. (2004). Estimation of groundwater pumping as closure to the water balance of a semi-arid, irrigation agricultural basin. Journal of Hydrology, 297(1-4): 51-74. doi.org/10.1016/j.jhydrol.2004.04.014.

Slater, L.D., Ntarglagiannis, D., Day-Lewis, F.D., Mwakyanamale, K., Versteeg, R.J., Ward, A., Strickland, C., Johnson, C.D., and Lane, J.W., Jr. (2010). Use of electrical imaging and distributed temperature sensing methods to characterize surface water–groundwater exchange regulating uranium transport at the Hanford 300 Area, Washington. Water Resources Research, 46:W10533. doi:10.1029/2010WR009110.

Taylor, C.J. and W.M. Alley. (2001). Ground-water-level monitoring and the importance of long-term water-level data. U.S. Geological Survey Circular 1217. Available at: https://pubs.usgs.gov/circ/circ1217/pdf/circular1217.pdf.

Taylor, C.J. and E.A. Greene. (2008). Chapter 3: Hydrogeologic characterization and methods used in the investigation of karst hydrology, In: Field techniques for estimating water fluxes between surface water and ground water. U.S. Geological Survey Techniques and Methods 4-D2. Available at: https://pubs.usgs.gov/tm/04d02/pdf/TM4-D2-chap3.pdf.

[TNC, The Groundwater Resource Hub] Groundwater Resource Hub: Understanding and Managing Groundwater Dependent Ecosystems. Website. Available at: https://groundwaterresourcehub.org/.

Wittenberg, H. and M. Sivapalan. (1999). Watershed groundwater balance estimation using streamflow recession analysis and baseflow separation. Journal of Hydrology, 219(1-2): 20-33. doi.org/10.1016/S0022-1694(99)00040-2.

WATER IN THE WEST Tools for Assessing Groundwater-Surface Water Connectivity Under the Sustainable Groundwater Management Act 26

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