Edward Potts

Welcome Edward Potts!

We are pleased to announce that Mr. Edward Potts has joined Todd Groundwater as Staff Geologist.

Mr. Potts is a geologist with professional experience in geophysical and petrophysical data collection, processing and interpretation; regional basin studies and geological research; and exploratory drilling. Ed earned a Master of Science degree from the University of Derby, England, where he graduated with merit. With his strong technical background in geophysics, geologic log correlation, three-dimensional interpretation, and large dataset management, he soon will be indispensable to Todd Groundwater's clients.

Congratulations, Chad Taylor!

Chad Taylor, PG, CHG

We are pleased to announce that Mr. Chad Taylor has been promoted to Vice President at Todd Groundwater.

Mr. Taylor is a licensed Professional Geologist and Certified Hydrogeologist with 23 years of experience-including 15 years with Todd Groundwater, where he has demonstrated his leadership in ensuring that Todd Groundwater can serve our clients with outstanding personnel in terms of experience and credentials and with the advanced technical tools that we use for data management, analysis and numerical modeling, project management, and communication.

His groundwater consulting experience ranges across a wide variety of disciplines from water supply well design and construction to sustainable basin management. Mr. Taylor has managed numerous projects involving groundwater sustainability, groundwater recharge, groundwater basin evaluations, groundwater resource assessment and management, design and installation of water supply wells, aquifer test data, and groundwater flow modeling. He has played key roles as project manager and/or project hydrogeologist in preparation of several Groundwater Sustainability Plans (GSPs) for basins across California, where he has contributed significantly to understanding of the hydrogeologic setting, water budgets, monitoring, data management systems, implementation programs, and outreach to stakeholders. He is now deeply involved in GSP implementation, including reporting, monitoring program expansion and Managed Aquifer Recharge including floodMAR, Aquifer Storage and Recover (ASR) and indirect potable reuse (IPR). Mr. Taylor is a skilled project manager who regularly works with water districts, and city and county governments, plus developers and legal counsel. He is active in the groundwater consulting community in California, particularly through participation in Association of California Water Agencies (ACWA) and Groundwater Association of California (GRA).

Arden Wells, PG promoted to Associate Geologist!!

Arden Wells, PG

We are happy to announce that Ms. Arden Wells, PG has been promoted to Associate Geologist at Todd Groundwater.

Arden joined Todd Groundwater in 2019 and since then has contributed to many important projects, including several groundwater sustainability plans. She specializes in groundwater quality and groundwater resources management, with experience ranging from geochemical modeling and statistical analyses to groundwater sustainability planning, implementation, and community engagement. She is an experienced field geologist involved in well design, lithologic logging, monitoring, test, production, and injection well construction, aquifer testing, and groundwater level and quality monitoring.

Arden demonstrates her commitment to wise use of groundwater through volunteer work; she is the Vice President of the San Francisco Bay Area branch of the Groundwater Resources Association of California and recently participated in water supply well construction overseas with Groundwater Relief and Oxfam International.

Congratulations Arden!!

Congratulations, Brent Johnson and Arden Wells!!

We are pleased to announce that Mr. Brent Johnson has been achieved credentials as a Certified Hydrogeologist and Ms. Arden Wells has earned licensure as a Professional Geologist.

Brent Johnson, PG, CHG

Arden Wells, PG

Arden has been with Todd Groundwater since 2019 after finishing a Masters of Science in Earth System Science at Stanford University. With Todd Groundwater, she has participated in multiple Sustainable Groundwater Management Act (SGMA) projects, providing her skills in data analysis, monitoring, and hydrogeologic and geochemical modeling Arden is also an accomplished field geologist with experience in lithologic logging, well construction, aquifer testing, and groundwater level and quality monitoring. Arden learned that she passed the Professional Geologist examination while in Cox's Bazar, Bangladesh where she has been volunteering with Groundwater Relief and Oxfam International to construct water supply wells for refugee camps.

Great work Brent and Arden!!

Evan Bosinger

Welcome Evan Bosinger

We are pleased to announce that Mr. Evan Bosinger has joined Todd Groundwater as Staff Geologist.

Mr. Bosinger is a hydrogeologist with project experience related to municipal water management, pollutant abatement, water quality analysis and treatment, and green infrastructure planning and development. He is well versed in California water policy and has assisted with compliance to local and state requirements on projects involving surface, storm, and groundwater. He utilizes techniques in data analysis and Geographic Information Systems (GIS) to provide support and solutions to hydrologic topics, including Groundwater Sustainability Plans (GSPs) and inputs for groundwater models.

Lindsay Hall

Welcome Lindsay Hall

We are pleased to announce that Ms. Lindsay Hall, EIT has joined Todd Groundwater as Associate Engineer.

Ms. Hall brings 21 years of agricultural engineering experience since graduating from the University of Arizona. She specializes in water budget investigations for agricultural water suppliers with skills in developing water budget models in spreadsheet and relational database environments, design of water budget applications, and application of quality control. She is highly experienced with various root zone/soil water balance models, particularly DWR's Integrated Demand Calculator, a module of Integrated Water Flow Model (IWFM), DWR's platform for integrated hydrologic modeling. In addition to developing water budget models for in-house use, Ms. Hall has developed several semi-automated water budget models for use by clients.

Pure Water Monterey Project Recognized for Engineering Excellence!

The Pure Water Monterey (PWM) project has been honored with two prestigious awards. The first was an Outstanding Civil Engineering Achievement awards from the American Society of Civil Engineers and the second was a 2022 Honor Award for engineering excellence from American Council of Engineering Companies of California. We extend our congratulations to our clients at Monterey One Water (M1W) and our colleagues at Kennedy Jenks Consultants!

This innovative project represents the first potable reuse project in Northern California and provides advanced treatment to industrial/agricultural wastewater, agricultural drainage, urban stormwater, and municipal effluent for potable reuse. This recycled water provides a safe and sustainable source of water for the Monterey peninsula. Through injection into the Seaside Groundwater Basin, the project provides stored water for future use, improves groundwater quality, and protects against seawater intrusion.

Todd Groundwater has had the opportunity to participate in the PWM project since 2006, contributing hydrogeologic expertise to early conceptual planning and engineering studies, monitoring program development and implementation, and recent injection well installation and testing. Current work involves expansion of the injection wellfields, wellfield operation, updates to the Engineering Report, and tracer testing. Todd Groundwater recognizes the former and ongoing contributions of Phyllis Stanin, Gus Yates, Brent Johnson, Garrett Erickson, Chad Taylor, Arden Wells, and Nicole Grimm and other contributing members of the Todd Groundwater team!

Garrett Erickson

Welcome Garrett Erickson!

We are pleased to announce that Mr. Garrett Erickson, GIT has joined Todd Groundwater as Staff Geologist.

Mr. Garrett Erickson is a hydrogeologist with broad consulting experience in water infrastructure, stormwater, and groundwater. He brings his clients experience in stormwater modeling and mitigation, fluvial geomorphologic studies, streambed restoration, surface water-groundwater analyses, well construction and maintenance, and permit compliance on all levels for a variety of project types proximal to waterways. His focus is production well siting, design, construction and maintenance, emphasizing effective design and field methods to maximize and maintain well efficiency.

He is currently engaged with Todd Groundwater in several projects involving GSP implementation.

Groundwater Sustainability Plan Takes the Cake!

Phyllis Stanin led the Todd Groundwater team in preparation of the Groundwater Sustainability Plan (GSP) for the Kern River Groundwater Sustainability Agency (GSA) in the Kern County Basin, comprising City of Bakersfield, Improvement District No. 4 of Kern County Water Agency, Kern Delta Water District, North of the River Municipal Water District/Oildale Mutual Water Company, and East Niles Community Services District and in cooperation with Greenfield County Water District GSA.

The Kern River GSP addresses 361 square miles on the Kern River Fan in the heart of the Kern Subbasin and was coordinated with four additional GSPs in the subbasin. The GSA has a diverse portfolio of surface water sources managed conjunctively with groundwater. The GSP provides a comprehensive basin setting, detailed water budgets, systematic and meaningful sustainability criteria, and useful monitoring and management actions—particularly managed recharge and conjunctive use—to support the Sustainability Goal.

Submittal of this GSP is a milestone in local and statewide groundwater sustainability. We extend our deep appreciation to the Kern River GSA managers and all who contributed!

Todd Groundwater to Present on Sustainable Groundwater

This conference, presented by Law Seminars International on July 25 and 26 in Sacramento, addresses current legal, technical, business, and regulatory information for preparing GSPs. Mr. Yates is participating on a panel addressing use of computer models; he will discuss surface water-groundwater hydrology, how to estimate surface flow depletion, and how to estimate effects of pumping and stream flow depletion on the sustainability of neighboring down-gradient basins.

David Todd and Iris Priestaf, Recharge Feasibility Study, Alpine County, 2002

Todd Groundwater is Celebrating 40 Years of Service to our Clients!

Todd Groundwater (originally David Keith Todd Consulting Engineers) was founded in May 1978 by Dr. David Keith Todd, author of the widely used textbook Groundwater Hydrology which is recognized as the first textbook to go beyond hydraulic equations to address groundwater basin management and critical issues of perennial yield, overdraft, and seawater intrusion.

The longevity and stability of our company attests to our ethic of providing excellent and responsive service to our clients and a stimulating and supportive work environment for our staff. We have participated in many changes in the groundwater industry over the years, from some of the first groundwater contamination investigations to the recent enactment of the California Sustainable Groundwater Management Act in 2014. As the groundwater industry has evolved and changed responding to threats to groundwater quality and supply, Todd Groundwater has been there to provide technical support. We look forward to continuing that support for many years to come.

Leadership of Todd Groundwater has evolved over the years. In 2003, Dr. Todd took on the role of Chairman, Dr. Iris Priestaf became President, and Ms. Phyllis Stanin was promoted to Vice President. Dr. Todd passed away in April 2006, but we carry on his vision of managing groundwater resources to benefit society and the environment.

Todd Groundwater to Present on Sustainable Groundwater

Dr. Priestaf will address technical issues of developing a Groundwater Sustainability Plan.

Todd Groundwater Presents at the Association of Groundwater Agencies/American Groundwater Trust Annual Conference

Ms. McCraven is an invited speaker for the February 17th session titled Water Reuse — A Growing Feature of California’s Supply Solutions. Sally will present findings from recent modeling conducted to help site and design advanced treated recycled water injection wells in the Montebello Forebay of the Central Basin in California

Upcoming Law Seminar on Groundwater Sustainability

Dr. Priestaf will address the elements of a Groundwater Sustainability Plan, including evaluation of sustainable yield and assessment of practical methods for getting to sustainability.

For more information, visit Groundwater Regulation in California.

Time for Planners to Get Their Feet Wet!

For more information, visit http://www.apacalifornia-conference.org/.

Todd Groundwater Presents Groundwater Impacts Analysis at Oil, Gas, and Groundwater Symposium

The program provided the latest information on petroleum industry practices — including hydraulic fracturing — relating to California groundwater, as described by recognized experts in the field. Ms. Stanin presented Todd Groundwater’s recent work on the California Statewide Programmatic Draft Environmental Impact Report titled Analysis of Oil and Gas Well Stimulation Treatments in California, published in January 2015. Ms. Stanin was part of an expert panel with Dr. Steven Bohlen, State Oil and Gas Supervisor for the Division of Oil, Gas, and Geothermal Resources (DOGGR) and Jonathan Bishop from the State Water Resources Control Board.

Todd Groundwater Completes Groundwater Impacts Analysis for Statewide EIR Regarding Well Stimulation Treatments Including Hydraulic Fracturing

The EIR provides the public with detailed information on potential environmental impacts associated with well stimulation treatments. The EIR was prepared in compliance with recent legislation: Senate Bill 4 (SB 4), adopted in 2013. Also in compliance with SB 4, the California Division of Oil, Gas, and Geothermal Resources (DOGGR) adopted regulations regarding well stimulation practices, including hydraulic fracturing. Although the DOGGR SB 4 regulations contain numerous protective measures for groundwater, the analysis concluded that well stimulation could have significant impacts to both groundwater quantity and quality without further mitigation. Seven key mitigation measures were developed. Collectively, the mitigation measures, DOGGR SB 4 regulations, and the resource protection standards incorporated into the project, along with required groundwater monitoring under SB 4, provide comprehensive protection for groundwater resources.

The Draft EIR contains 2,771 pages plus appendices. It can be obtained from the DOGGR website. Public comments are due by March 16.

Todd Groundwater to Present on Groundwater Sustainability Issues

Dr. Priestaf will address elements of a Groundwater Sustainability Plan, including evaluation of sustainable yield and assessment of practical methods for getting to sustainability.

Governor Brown signs historic groundwater legislation

Historic Groundwater Sustainability Legislation in California!

The Act, defined in three linked legislative bills (Senate Bill 1168, Senate Bill 1319, and Assembly Bill 1739), is detailed and comprehensive. It provides a priority list of groundwater basins, defines Groundwater Sustainability Agencies (GSAs), outlines the contents of Groundwater Sustainability Plans (GSPs), establishes the roles of State agencies, and sets a timeline with deadlines. Specifically, it mandates the preparation of management plans for more than 100 groundwater basins by 2022 with subsequent achievement of sustainability in another 20 years. While building on previous management legislation, it more than ever requires acknowledgment of multiple benefits and uses of groundwater, including maintenance of stream flows and environmental benefits, and supports collaboration between water agencies and planning agencies.

Todd Groundwater has been engaged for the past 35 years in assisting local water agencies, cities, and counties in groundwater management planning. For us, this is part of the legacy of Dr. David Keith Todd who placed groundwater management at the core of his textbook Groundwater Hydrology, defined the concept of perennial yield, and pioneered groundwater management techniques.

We stand ready to continue assisting local agencies, guided by this new policy of the State, that:

Todd Groundwater Presents Talk and Poster at the 14th Biennial Symposium on Managed Aquifer Recharge

TALK — Groundwater Replenishment in the Seaside Basin: Increasing Basin Yield with Recycled Water

Monterey Regional Water Pollution Control Agency and Monterey Peninsula Water Management District are developing a groundwater replenishment (GWR) project to substantially increase the perennial yield from the Seaside Groundwater Basin. A new advanced water treatment plant will be constructed to produce recycled water from numerous source waters including stormwater, industrial wash-water, agricultural drain water, and municipal wastewater. Recycling of these water sources has the potential for significant environmental benefits while enhancing the critically-limited water supply for the Monterey Peninsula area.

The project will provide replenishment to the two primary drinking-water aquifers in the basin. The deeper, semi-confined Santa Margarita aquifer will be recharged with deep injection wells (900 feet deep). The shallower, unconfined Paso Robles aquifer will be recharged using vadose zone wells about 200 feet deep. Water levels in both aquifers are currently below sea level and are at risk of seawater intrusion.

The project is being developed to coordinate with an ongoing Aquifer Storage and Recovery (ASR) project, which is operated to recharge and recover available Carmel River water through four ASR wells.

A field program was conducted in late 2013 and early 2014 to address knowledge gaps for recharging the shallow aquifer through vadose zone wells. The program included:

• continuous coring of the 400-feet deep vadose zone,
• sampling and analyses of hydraulic properties,
• leaching analyses of core samples with GWR product water,
• mineralogical analysis,
• installation of a monitoring well,
• extensive groundwater quality analyses including age dating and isotopic analyses in six nearby wells including an ASR monitoring well.

The data were used to support geochemical modeling in order to evaluate the geochemical compatibility of GWR water, ambient groundwater, and Carmel River ASR water. The presentation describes the results of the field program and demonstrates the need for and use of key hydrogeologic data for the GWR project planning and implementation.

POSTER — Optimizing Recharge and Recovery in the Pauba Valley: Balancing Short-Term Recovery with Long-Term Storage

The District has embarked on a study to optimize the Upper VDCR/RF operations through local-scale numerical modeling of numerous recharge and recovery scenarios. Operational scenarios evaluated included increased recharge in certain ponds or sub- portions of ponds, use of recovery wells adjacent to the ponds to control groundwater mounding, and selective operation of key downgradient recovery wells to increase extraction of the recharged water. Todd Groundwater applied numerical groundwater modeling and particle tracking to determine the fate of the recharged water.

Model flowpaths for current Recharge and Recovery Operations

A local-scale five-layer MODFLOW groundwater model was developed and well calibrated to simulate aquifer response to historical recharge events, and subsequently used to analyze various recharge and recovery alternatives. The local model is essentially a telescopic mesh refinement of a regional groundwater flow model with additional layer refinement.

Simulations showed that operation of new recovery wells could increase the recharge capacity of the Upper VDC Site to 60 cubic feet per second.

The District has proceeded with expansion plans for the Upper VDC Site and recently constructed additional facilities to increase recharge and recovery operations. Dan Craig, Senior Hydrogeologist/Modeler with Todd Groundwater, is an author along with District Staff Warren Back and Rich Ottolini.

Before the Well Runs Dry: Improving the Linkage Between Groundwater and Land Use Planning

Groundwater is a critical resource in California, providing from 30% of the state’s water supply in normal years to 40% or more in dry years. As unsustainable groundwater use driven by land use changes continues in many basins around the state, there is growing consensus that more effective integration of land use planning and groundwater management is needed. To address this growing concern, Water in the West convened thirty groundwater managers, land use planners, water lawyers, consultants, and academics at Stanford University in September 2013 in an Uncommon Dialogue, designed to bring leaders from different sectors to develop practical solutions to pressing environmental challenges centered on water. This report, shaped in part by the Dialogue, provides the background and regulatory context for land use planning and groundwater management in California, shares case studies that highlight the intersection of groundwater and land use, and makes specific recommendations to improve the linkage between land use decisions and groundwater management in the state.

Dr. Iris Priestaf, President of Todd Groundwater, assisted in organizing the Uncommon Dialogue, participated in the process, and provided review of the report. The report is available on the Water in the West website, at http://waterinthewest.stanford.edu/resources/publications-directory/groundwater_landuse.

Salt and Nutrient Management Plan Approved

SNMPs are intended to facilitate the implementation of recycled water projects by characterizing all salt and nutrient sources (including recycled water projects) and their impacts to groundwater quality. SNMPs also identify implementation measures to manage salts and nutrients in a sustainable manner to protect beneficial groundwater uses

Managed Aquifer Recharge in Urban Environments

Planned expansion of key water reclamation plants will increase the availability of tertiary and advanced-treated recycled water for recharge and reduce local reliance on imported water. Mr. Lin described Todd development of a Salt and Nutrient Management Plan for the CBWCB to characterize ambient salt/nutrient groundwater quality and evaluate the impact of salt/nutrient loading from existing and future planned MAR projects against anti-degradation criteria set forth in the State Water Resources Control Board’s Recycled Water Policy.

Todd was a sponsor for the symposium.

Todd Salt and Nutrient Plan Workshop and Presentation

The objective of the Salt and Nutrient Management Plan (SNMP) is to manage salts and nutrients (S/N) from all sources on a basin-wide or watershed-wide basis in a manner that ensures attainment of water quality objectives and protection of beneficial uses. This SNMP workshop focuses on the practical methodologies and technical analyses that are being applied for recently completed and ongoing SNMPs.

Sally McCraven, Principal Hydrogeologist with Todd, helped coordinate the workshop and Edwin Lin, Senior Hydrogeologist with Todd, presented technical approaches for S/N loading. The workshop agenda and presentation summaries are available at https://www.watereuse.org/conferences/california/13/workshops. In addition, Ms. McCraven’s session presentation entitled Calibration – An Important Tool in Making Loading Assumptions for Salt and Nutrient Management Plans describes Todd approach for several SNMPs being conducted across the state shown by the red stars on the map at right.

Sustainability from the Ground Up

Dr. Priestaf noted the importance of coordination of state and local water agencies with city and county planning agencies. Such coordination has been encouraged by subsequent legislation that mandates certain groundwater management actions and promotes sharing of information. For example, the 2009 Water Package included a Senate Bill (SBx7-6) that requires groundwater level monitoring of all groundwater basins in California. The resultant California Statewide Groundwater Elevation Monitoring (CASGEM) program, based on local monitoring entities, now provides public online access to groundwater level data from across the state. Also, the 2011 Assembly Bill 359 amends the water code, requiring that AB 3030/SB 1938 groundwater management plans include a map that delineates areas of significant groundwater recharge. When the groundwater management plan is adopted, the local water agency is required to provide this map to local planning agencies.

Beach Seep Flow

Todd Presents Talk in GRA Tools and Technology Series

Environmental forensics has been defined as the systematic examination of environmental information used in litigation. For the past decade, techniques such as fuel fingerprinting, stable and radiogenic isotope analyses have been used to determine and assess contaminant sources. However, forensic scientists have other investigative tools and techniques at their disposal, which can be tailored to the investigation; examples are described below. Dr. Motzer will present three case studies of how environmental forensics were used by Todd to solve environmental problems.

DNA Fingerprinting of Coliform Bacteria

Pit Lake

Using Surrogates to Determine Groundwater Contaminant Sources

Coastal Seep Flow

Using Multiple-Faceted Hydrogeological and Geochemical Investigations

Todd Presents Two Talks at the NWRI/WaterRF/OCWD Symposium

On Tuesday, January 25 in Session 6b: Modeling of Recharge Basin Performance, Dan Craig, Senior Hydrogeologist with Todd presented: Optimizing Recharge and Recovery at Recharge Basins in the Pauba Valley and Phyllis Stanin, Vice President of Todd, presented: Recharge and Supply Allocation in the Ames Valley Basin - Making it Happen.

Optimizing Recharge and Recovery at Recharge Basins in the Pauba Valley

Cross section of VDC Lower Ponds

At the Lower Ponds, alluvial fan and fluvial processes have deposited permeable channel sands that typically result in high infiltration rates and groundwater storage capacity. However, heterogeneity in the alluvial aquifers has created some problems of infiltration in certain areas.

Two local-scale MODFLOW models, based on the District's regional model, have been constructed by Todd over each area to simulate various scenarios of recharge and recovery. Numerous operational scenarios were evaluated including increased recharge in certain ponds, use of wells adjacent to the basins to control groundwater mounding, and selective operation of key downgradient wells to increase recovery of the recharge water.

Modflow model of VDC Lower Ponds	Modflow model of VDC Upper Ponds

Modflow simulated flowpaths for Ames Valley

Recharge and Supply Allocation in the Ames Valley Basin - Making it Happen

Todd constructed a groundwater model of the Pipes and Reche subbasins in the western Mojave Desert to verify basin sustainable yield, characterize groundwater flow conditions, and evaluate the hydraulic impacts of the planned recharge facility. The model included complex hydrogeologic features, including faults that serve as partial barriers to groundwater flow.

Todd assisted BDVWA in development of a GWMP for the basin, which included a description of the state of the groundwater basin, water supply and demand, basin management objectives, basin management strategies, and implementation plan, and a monitoring program (for levels, quality, storage, and subsidence).

Total future pumping allocations may exceed average basin perennial yield during future dry years. Imported water recharge will be conducted to increase storage and supplement supply. Based on future storage changes, pumping reductions may be implemented.

Protecting Water Quality: Todd Presentations at the 2010 GRA Annual Conference

The three presentations described below are illustrative of Todd current projects.

"Old" and "New" Emerging Contaminants

Dr. Motzer gave his talk on Wednesday, September 15, 2010 from 2:30 to 3:00pm in Session 2B: Emerging Contaminants -- From the Source to Groundwater.

City of San Jose South Bay Water Recycling Groundwater Monitoring and Mitigation Program Update

Mr. Craig presented his team's findings on Wednesday, September 15, 2010 from 3:30 to 4:00pm in Session 4B: Recycled Water Groundwater Recharge.

West Coast Basin Barrier Project (WCBBP) Intrinsic Tracer Study

Todd evaluated natural (or intrinsic) water quality parameters (primarily sodium, calcium, chloride, and sulfate ions) using Brine Differentiation Plots, which proved to be a powerful tool to differentiate the relative amounts of blended injectate, seawater, and baseline groundwater. Brine Differentiation Plots were effective in verifying the amounts of recycled water in WCBBP monitoring wells, identifying the influence of seawater, and in documenting the travel time of injected water to monitoring wells.

Mr. Lin gave his presentation on Thursday, September 16, 2010 from 9:00 to 9:30am in Session 4B: Recyceld Water Groundwater Recharge

Todd Study Cited in Court Decision on SB 610 Water Supply Assessments

For large development projects, the Water Code (section 10910, commonly referred to by its original legislation, Senate Bill 610 or SB 610) requires that water suppliers prepare a water supply assessment that determines whether water supplies are sufficient for the project and other planned growth over the long-term. If the water supply for the proposed project includes groundwater, the assessment must analyze the sufficiency of groundwater to meet the projected demand of the project.

In O.W.L. Foundation vs City of Rohnert Park, a key issue was the scope of the groundwater analysis. O.W.L. interpreted the water code to require analysis of all current and future pumping on the basis of a groundwater basin, with specific reference to groundwater basins as defined by the Department of Water Resources. The Court of Appeal rejected O.W.L.'s narrow interpretation, noting the large size of some groundwater basins and the impracticality of collection and analysis of basin-wide data in the 90-day statutory deadline for completion of a water supply assessment.

O.W.L. also argued that the study area used by Rohnert Park was inappropriate because it was based on watershed boundaries; these boundaries had been defined in large part by Todd in a 2004 study for Sonoma County, Groundwater Study for the Canon Manor West Subdivision Assessment District. However, the Court found the watershed study area to be legally adequate, indicating the Todd study not only provided an independent analysis, but also a rationale and evidentiary support including a discussion of the relationships between watershed boundaries and groundwater divides.

The Court's decision provides valuable guidance for preparation of water supply assessments and affirms that water suppliers and their experts must have discretion in selecting the study area and methodologies, as long as there is adequate empirical data and analysis.