Corona City Council
June 3, 2026

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TODD GROUNDWATER,
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Figure 6-2. Aerial Images of Riparian Vegetation 1994-2018.............................................. 6-42 Figure 6-3. Annual Groundwater Pumping Near Temescal Wash ....................................... 6-43 Figure 6-4. Water Levels in Wells Near Temescal Wash...................................................... 6-44 Figure 6-5. Wastewater Discharges to Temescal Wash 1989-2019 .................................... 6-45 Figure 7-1. Groundwater Level Wells, Dedicated and Other Monitoring Wells.................. 7-14 Figure 7-2. Water Quality Monitoring Wells........................................................................ 7-15 Figure 9-1. Schedule for GSP Implementation....................................................................... 9-6 Appendices (following text)
Appendix A – Joint Powers Agreement forming the Bedford-Coldwater Groundwater Sustainability Agency
Appendix B – Bedford-Coldwater GSA Notice of Decision to become a Groundwater Sustainability Agency
Appendix C – GSP Elements Guide
Appendix D – BCGSA Stakeholder Outreach Plan
Appendix E – Public Meeting Summaries
Appendix F – Draft GSP Comments and Responses
Appendix G – Bedford-Coldwater GSP Numerical Groundwater Model Documentation Report
Appendix H – Baseline Water Quality Sampling Results
Appendix I – Management Areas Designated in the Bedford Coldwater Subbasin to be Included in the Groundwater Sustainability Plan
Appendix J – Detailed Annual Surface and Groundwater Budgets Appendix K – Bedford-Coldwater GSP Data Management System Description Acronyms
Actions Management Actions
AF acre-feet
AFY acre-foot per year
Agreement Joint Powers Agreement forming the BCGSA
Basin Plan Water Quality Control Plan for the Santa Ana River Basin Basin Bedford-Coldwater Subbasin
BCGSA Bedford-Coldwater Groundwater Sustainability Agency bgs below ground surface
Board BCGSA Board of Directors

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CASGEM California Statewide Groundwater Elevation Monitoring CCED California Conservation Easement Database
CCR California Code of Regulations
CDFW California Department of Fish and Wildlife
cfs cubic feet per second
CIMIS California Irrigation Management Information System COC constituent of concern
Corona City of Corona
DDW Division of Drinking Water
DMS Data Management System
DPR Department of Pesticide Regulation
DWR California Department of Water Resources
DWSAP Drinking Water Source Water Assessment Program
EMWD Eastern Municipal Water District
ET evapotranspiration
ET0 reference evapotranspiration
EVMWD Elsinore Valley Municipal Water District
FMMP Farmland Mapping and Monitoring Program
ft feet
GAMA Groundwater Ambient Monitoring and Assessment
GDE groundwater dependent ecosystem
GIS geographic information system
GMZs groundwater management zones
GPS Global Positioning System
GSA Groundwater Sustainability Agency
GSP Groundwater Sustainability Plan
GWMP Groundwater Management Plan
in/yr inches per year
InSAR Interferometric Synthetic Aperture Radar
IRWMP Integrated Regional Water Management Plan
JPA Joint Powers Authority
km2 square kilometers
M&I municipal, commercial, and industrial
MA Management Area
MCL Maximum Contaminant Level
Metropolitan Metropolitan Water District of Southern California mg/L milligrams per liter
mi2 square miles
MO Measurable Objective
MODFLOW United States Geological Survey modular finite-difference flow model MSHCP Western Riverside County Multiple Species Habitat Conservation Plan msl mean sea level
MT Minimum Threshold
NAD83 North American Datum of 1983

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NAVD88 North American Vertical Datum of 1988
NCCAG Natural Communities Commonly Associated with Groundwater NCED National Conservation Easement Database
NDMI normalized difference moisture index
NDVI normalized difference vegetation index
NED National Elevation Dataset
ng/L nanograms per liter
NO3 nitrate
NOAA National Oceanic and Atmospheric Administration
NPS nonpoint source
NRCS US Department of Agriculture, Natural Resources Conservation Service
NTU nephelometric turbidity unit
NWIS National Water Information System
ORP oxidation-reduction potential
OWTS on-site wastewater treatment system
PFOA perfluorooctanoic acid
PFOS perfluorooctanesulfonic acid
ppt parts per trillion
Projects projects to support sustainability
QA/QC quality assurance and quality control
RCRCD Riverside County Resource Conservation District
RFP Request for Proposal
RWQCB Santa Ana Regional Water Quality Control Board
SARHCP Upper Santa Ana River Habitat Conservation Plan
SCADA Supervisory Control and Data Acquisition
SFR Streamflow Routing Package
SGMA Sustainable Groundwater Management Act
SMC Sustainable Management Criteria
SMCL Secondary Maximum Contaminant Level
SMP Surface Mining Permit
SNMP Salt and Nutrient Management Plan
SSURGO Soil Survey Geographic Database
SWP State Water Project
SWRCB State Water Resources Control Board
TDS Total Dissolved Solids
TNC The Nature Conservancy
TVWD Temescal Valley Water District
USDA United States Department of Agriculture
USGS United States Geological Survey
UTV Upper Temescal Valley
UWMP Urban Water Management Plan
WMWD Western Municipal Water District
WRF Water Reclamation Facility

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EXECUTIVE SUMMARY
The Sustainable Groundwater Management Act (SGMA) requires local agencies in groundwater basins designated as high- or medium-priority to form Groundwater Sustainability Agencies (GSAs) and develop a Groundwater Sustainability Plan (GSP) to plan for achieving and/or maintaining sustainability within 20 years of implementing the plan. The Bedford-Coldwater Groundwater Subbasin (Basin) has been designated by the California Department of Water Resources (DWR) as very low-priority, so the preparation of a GSP is not required. However, the City of Corona (Corona), Temescal Valley Water District (TVWD), and Elsinore Valley Municipal Water District (EVMWD), the three major water purveyors and groundwater users in the Basin, are committed to protecting and maintaining sustainable groundwater conditions in the Basin into the future.

The three agencies signed a Joint Powers Agreement (Agreement) creating a Joint Powers Authority (JPA) and forming the Bedford-Coldwater Groundwater Sustainability Agency (BCGSA). The BCGSA has volunteered to become the GSA for the Bain and prepare and implement this GSP.

BASIN SETTING
Figure ES-1 shows the Basin located in western Riverside County. Figure ES-1 also shows the adjacent Temescal Basin to the northwest and Elsinore Valley Subbasin to the south. The Basin is bound on the east and west by consolidated rocks of Estelle Mountain and the Santa Ana Mountains, respectively.

The Bedford-Coldwater Basin is composed of alluvial fan, alluvial valley, axial channel, and wash deposits. These deposits are sourced from the Santa Ana Mountains to the west of the Basin and the Peninsular Ranges to the east of the Basin. The alluvial fan deposits in the Coldwater area extend into the Bedford area and have been disrupted by faulting. Channel deposits along Temescal Wash and local tributaries define the eastern boundary of the Basin.

In the northern Bedford area, a variety of Tertiary sedimentary units crop out and the character of these deposits and the groundwater chemistry differs from the alluvial fans to the north in the Temescal Subbasin and those to the south in the Elsinore Groundwater Basin.

These deposits vary in depth from less than 40 feet up to 500 feet in the Bedford area (eastern portion of the Basin) and up to 800 feet in thickness in the deepest portions of the Coldwater area (western portion of the Basin).

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Figure ES-1. Bedford-Coldwater Basin
The Basin is divided into two Management Areas (MAs) designed to facilitate analysis, management, and implementation of the GSP. The MAs are shown on Figure ES-2. The Bedford MA occupies roughly the eastern two-thirds of the Basin. It is separated from the Coldwater MA by the Glen Ivy Fault, which is a partial barrier to groundwater flow. The Coldwater MA is the part of the Basin west of the Glen Ivy Fault. Because of downward movement on that side of the fault, Basin thickness is much greater than in the Bedford MA.

The partner agencies of the BCGSA are the primary groundwater users in the basin. There are no disadvantaged communities (DACs) or tribal lands in the Basin, and the BCGSA believes there are very few private wells, none of which are used for potable water supply in the Basin.

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Figure ES-2. Bedford-Coldwater Basin Management Areas

GROUNDWATER CONDITIONS
Basin groundwater elevations have been relatively stable in recent years. Groundwater elevations in the northern portion of the Bedford MA show a slight decrease during the 2013 through 2015 drought but have begun to recover. Groundwater elevations in the Coldwater MA declined over the last 24 years with significant fluctuations in response to wet and dry cycles. Water levels in the Coldwater area have varied more than 350 feet during this period and there have been multiple major and minor cycles of groundwater elevation decline and recovery. The wide water level fluctuations over time in the Coldwater area likely reflect the relatively small footprint and fault-controlled flow along with the fact that most of the pumping in the Basin occurs in this area. Although long-term declines in groundwater elevations have occurred in Coldwater in the past, recent groundwater elevations have stabilized due in part to shared management of the Basin between the BCGSA agencies.

Total Dissolved Solids (TDS) and nitrate are the primary constituents of concern in the Basin.

TDS concentrations are relatively low in the Coldwater MA, naturally higher in Bedford MA, and generally increase downstream. Groundwater in the Basin has been impacted by human activities in the Basin and watershed including agricultural, urban, and industrial land uses.

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Nitrate has historically been the most significant constituent of concern in the Basin. Water quality in the Basin is generally within drinking water standards.

WATER SUPPLY
Sources of water supply for agricultural, Municipal and Industrial (M&I), and domestic uses include groundwater, imported water, and recycled water. Metropolitan Water District of Southern California (Metropolitan) is the wholesaler for imported water and its sources of water include the Colorado River and the State Water Project. Both Corona and TVWD receive imported water from Metropolitan for distribution in the Basin. EVMWD also receives imported water from Metropolitan through Western Municipal Water District (WMWD), but only distributes imported water within the Basin when groundwater supply to customers is insufficient.

Groundwater has been an important component of water supply in the Basin for more than 100 years. Until the 1970s, most of the groundwater production in the Basin was for agricultural supply. A few well owners have also produced small amounts of groundwater for domestic use. Production for municipal supply increased in the 1960s and 1970s and continues today.

For more than 50 years, Corona, EVMWD, and TVWD have relied on groundwater from the Basin for municipal uses, and these agencies have long been responsible for managing groundwater conditions in the Basin. Corona and EVMWD have legal agreements for the management of withdrawals from the Coldwater portion of the Basin. Additionally, Corona, in coordination with TVWD, adopted a Groundwater Management Plan (GWMP) in 2008 that covers the Basin.

WATER BUDGET
A water balance (or water budget) is a quantitative tabulation of all inflows, outflows, and storage change of a hydrologic system. This GSP contains a detailed water balance for both the groundwater system and surface water system of the Basin. The water budgets were developed for time periods representing historical, current, future no project (baseline), and future growth plus climate change (growth plus climate change) conditions.

In the Bedford MA, the major inflow to the groundwater budget is percolation from streams, especially during wet years. In recent years (2012 to 2018), reclaimed water percolation has become another major inflow. The major outflows include M&I pumping and groundwater discharge to streams. Historically, agricultural pumping also contributed to outflow from the Basin, but this decreased to a negligible amount by 2007. Groundwater storage in the Bedford MA increased slightly during the historical period (Figure ES-3), primarily as a result of the decrease in total groundwater pumping. Outflows in the future scenarios (baseline and growth plus climate change) are predicted to increase in response to increased pumping.

However, as shown in Figure ES-3, the Basin is still expected to have a positive change in storage (more inflow than outflow) in the future, even in growth and climate change

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projections. This future increase in storage is due to continued groundwater management and increased imported water use in the Basin.

Figure ES-3. Cumulative Storage Change: Bedford Management Area In the Coldwater MA, percolation from streams occurs as infrequent, episodic events; stream percolation can range from 15,000 acre-feet (AF) in wet years to zero in dry years. M&I pumping has dominated outflows in this MA, although it has decreased from its peak in the late 1990s. Similar to the Bedford MA, agricultural pumping was a significant outflow historically, but decreased to a negligible amount by 2001.

Estimated historical storage in the Coldwater MA declined by a cumulative total of 60,000 AF from 1990 to 2004, as shown in Figure ES-4. EVMWD and Corona entered into an agreement to limit pumping in the MA to a periodically re-calculated safe or sustainable yield in 2008. As a result, there was little additional cumulative decline from 2005 to 2018. In contrast, storage in both future scenarios is predicted to increase steadily over the 50 year future simulation periods. Inflows are estimated to exceed outflows in the future because of increased urban recharge and continued limitation of pumping. The rate of storage increase is slightly higher under the growth plus climate change scenario relative to the baseline scenario, which can be attributed to increased urban return flow recharge.

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Figure ES-4. Cumulative Storage Change: Coldwater Management Area

SUSTAINABLE MANAGEMENT CRITERIA (SMC)
This GSP defines sustainable management as the use and management of groundwater in a manner that can be maintained without causing undesirable results, which are defined as significant and unreasonable effects caused by groundwater conditions occurring throughout the Basin, specifically in consideration of the following sustainability indicators:
• Chronic lowering of groundwater levels indicating a significant and unreasonable depletion of supply.
• Significant and unreasonable reduction of groundwater storage. • Significant and unreasonable seawater intrusion. 1
• Significant and unreasonable land subsidence that substantially interferes with surface land uses.
• Significant and unreasonable degraded water quality, including the migration of contaminant plumes that impair water supplies.
• Depletions of interconnected surface water that have significant and unreasonable adverse impacts on beneficial uses of the surface water.

For these sustainability indicators, a GSP must develop quantitative sustainability criteria that allow the GSA to define, measure, and track sustainable management. These criteria include the following:
1 Seawater intrusion is noted, but no risk of seawater intrusion exists in this inland basin.

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• Undesirable Result – significant and unreasonable conditions for any of the six sustainability indicators.
• Minimum Threshold (MT) – numeric value used to define undesirable results for each sustainability indicator.
• Measurable Objective (MO) – specific, quantifiable goal to track the performance of sustainable management.

The sustainability indicators and SMC are clearly defined and provide a quantitative analysis of the Basin’s sustainability. As the Basin is currently sustainable, and has been managed sustainably, the following sustainability criteria are defined in to avoid future undesirable results:
• The Minimum Threshold for defining undesirable results relative to chronic lowering of groundwater levels is defined by operational considerations to maintain water levels at or above current pump intakes or screen bottoms (whichever is higher) in municipal water supply wells represented by frequently monitored Key Wells.

Undesirable results are indicated when two consecutive exceedances occur in each of two consecutive years, in two-thirds or more of the currently monitored wells in each Management Area.
• The Minimum Threshold for reduction of groundwater storage for all Management Areas is fulfilled by the minimum threshold for groundwater levels as proxy. • The Minimum Threshold for land subsidence is defined as a cumulative decline equal to or greater than one foot of decline since 2015, which represents current conditions and the SGMA start date. This is equivalent to a rate of decline equal to or greater than 0.2 feet in any five-year period. The extent of cumulative subsidence across the Basin will be monitored and evaluated using Interferometric Synthetic Aperture Radar (InSAR) data available through the SGMA Data Viewer during the 5- year GSP updates. Subsidence as a result of groundwater elevation decline is closely linked to groundwater levels and it is unlikely that significant inelastic subsidence would occur if groundwater levels remain above their minimum thresholds. • The Minimum Thresholds for degradation of water quality address nitrate and total dissolved solids (TDS) for the entire Basin.
o The Nitrate Minimum Threshold (in both Management Areas) is defined as 5-year average concentrations of all monitored wells not exceeding the 10 milligrams per liter (mg/L) drinking water maximum contaminant level (MCL) for Nitrate as Nitrogen.
o The TDS Minimum Threshold (in both Management Areas) is defined as the 5-year average concentrations not exceeding the 1,000 mg/L secondary MCL for TDS.
• The Minimum Threshold for depletion of interconnected surface water is the amount of depletion associated with the lowest water levels recorded during the 2010 to 2015 drought. Specifically, undesirable results would occur if more than half of monitored wells near Temescal Wash had static water levels lower than 35 feet below the adjacent riparian vegetation ground surface elevation for a period of more than one year.

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MONITORING NETWORK
The monitoring network for GSP implementation has been established to document groundwater and related surface conditions as relevant to the sustainability indicators, MTs, and MOs. The components of the monitoring network are built from existing programs and will be carried out by the BCGSA.

The BCGSA has actively engaged in assessment and improvement of its monitoring network.

This process has been intensified as part of the GSP, given the need to identify data gaps and to assess uncertainty in setting and tracking sustainability criteria. Monitoring improvements such as adding or replacing monitoring infrastructure are part of GSP implementation and will be reviewed and updated for each five-year GSP update.

PROJECTS AND MANAGEMENT ACTIONS
During the preparation of the GSP, the BCGSA identified five specific management actions (Actions) and three projects (Projects) to achieve the sustainability goal. The Actions are generally focused on data collection, storage and reporting of information necessary to monitor sustainability, and assessment of when Actions may be necessary (i.e., when MTs are approached or exceeded). The projects are generally designed to reduce uncertainty in areas where data gaps have been identified during development of the GSP. The Projects and Actions in the GSP are as follows:
• Action 1 – Provide for Collection, Compilation, and Storage of Information Required for Annual Reports and Submit Annual Reports;
• Action 2 – Routinely Record Groundwater Levels and Take Action if Necessary; • Action 3 – Monitor Selected Groundwater Quality Constituents and Coordinate with the Regional Water Quality Control Board as Appropriate; • Action 4 – Track Trends in Groundwater Levels near Temescal Wash and Take Action as Necessary;
• Action 5 – Review Interferometric Synthetic Aperture Radar (InSAR) Data on the California Department of Water Resources (DWR) Dataviewer During 5-Year Updates;
• Project 1 – Investigate Groundwater/Surface Water Interaction at Temescal Wash and Install Monitoring Wells;
• Project 2 – Initiate a Survey of Active Private Wells; and • Project 3 – Evaluation of the Effects of Aggregate Pits on Groundwater Flow and Quality.

The Projects and Actions will be implemented by a combination of existing resources from the three agencies within the plan area and contracted resources.

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IMPLEMENTATION
The official adoption of the GSP by the BCGSA will initiate Plan implementation. After submittal of the GSP to DWR, and during the DWR review period, the BCGSA will continue to communicate with stakeholders via the BCGSA’s website and begin implementing the projects and management actions described in this GSP. The Plan will be implemented to sustainably manage groundwater in the Basin under the authority of the BCGSA and its member agencies.

The BCGSA is required to submit an annual report to DWR by April 1st of each year following adoption of the GSP. The first annual report will be due in April of 2022. The BCGSA has committed to implementing the GSP upon adoption and completing the projects and management actions necessary to monitor and maintain sustainability within the first 5 years of initiation of the GSP.

Bedford-Coldwater GSP 1-1

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1. INTRODUCTION
The Sustainable Groundwater Management Act (SGMA), effective January 1, 2015, was enacted in California to regulate and sustainably manage groundwater basins throughout the state. SGMA provides a framework to guide local public agencies and newly created Groundwater Sustainability Agencies (GSAs) in the management of their underlying groundwater basins, especially those considered critically affected as defined by the Department of Water Resources (DWR). The Bedford-Coldwater Groundwater Sustainability Agency (BCGSA) has elected to create a Groundwater Sustainability Plan (GSP) to maintain long-term groundwater sustainability in the Bedford-Coldwater Groundwater Subbasin (Basin, Figure 1-1) of the Elsinore Groundwater Basin.

1.1. PURPOSE OF THE GROUNDWATER SUSTAINABILITY PLAN
SGMA requires local agencies of all basins designated as high- or medium-priority to develop a GSP to halt groundwater overdraft and achieve sustainability within 20 years of implementing the plan. Although the Basin is designated as very low-priority and does not require a GSP, the BCGSA is committed to protecting and maintaining the current sustainable conditions into the future and has opted to create and implement a GSP.

The purpose of the GSP is to provide basic information on the groundwater conditions in the Basin and to provide a plan or roadmap to maintain sustainability of beneficial use of groundwater in accordance with SGMA. The goal of the GSP is to promote Basin health by maintaining the generally balanced water budget, continue to prevent chronic overdraft, and avoid undesirable results which SGMA has divided into the six categories, represented in Figure 1-2 below.

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Santa Ana Mountains
Bedford-Coldwater
Groundwater Basin
Path: T:\Projects\Bedford Coldwater GSP 80802\GIS\Maps\Figures\GSP Figures\Chapter 1 and 2 - ES, Intro, and, Plan Area\Figure 1-1 BC GW Basin and Adjacent Basins_r1.mxd Figure 1-1
Bedford-Coldwater
Groundwater Basin, GSA,
and Adjacent Basins
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Groundwater Sustainability Agency
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("N
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0 1,750 3,500
Scale in Feet
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Figure 1-2. SGMA Undesirable Results
The GSP assesses sustainability related to each of the categories listed above, defines thresholds for maintaining sustainability, outlines groundwater monitoring protocols, best management practices, management actions and projects designed to improve monitoring capabilities and/or to protect and enhance groundwater conditions. The GSP also includes a schedule and cost estimate for plan implementation. Each element of the GSP is designed to promote basin health and achieve and maintain the sustainability goal established for the Basin by the BCGSA.

1.2. SUSTAINABILITY GOAL
The BCGSA prepared this GSP with the goal of sustaining groundwater resources for the current and future beneficial uses of the Bedford-Coldwater Basin in a mannerthat is adaptive and responsive to the following objectives:
• Provide a long-term, reliable and efficient groundwater supply for municipal, industrial, and other uses;
• Provide reliable storage for water supply resilience during droughts and shortages; • Protect groundwater quality;
• Support beneficial uses of interconnected surface waters; and • Support integrated and cooperative water resource management.

This goal is consistent with SGMA and is based on information from the Plan Area, Hydrogeologic Conceptual Model, Groundwater Conditions, and Water Budget sections of this GSP that:
• Identify beneficial uses of Basin groundwater and document the roles of local water and land use agencies;
• Describe the local hydrogeologic setting, groundwater quality conditions, groundwater levels and storage, and inflows and outflows of the Basin; and • Document the ongoing water resource monitoring and conjunctive management of groundwater, local surface water, recycled water and especially imported water sources that help protect groundwater quality and maintain water supply.

Lowering
Groundwater
Levels
Reduction of
Groundwater
Storage
Seawater
Intrusion
Degraded
Water Quality
Land
Subsidence
Surface Water
Depletion

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1.3. AGENCY INFORMATION
This section provides contact information, management structure, and legal authority of the BCGSA.

BCGSA Mailing Address: Bedford-Coldwater Groundwater Sustainability Authority 31315 Chaney Street
Lake Elsinore, CA 92530

1.3.1. Organization and Management Structure
The BCGSA consists of representatives from the three agencies overlying the Basin: The City of Corona (Corona), Elsinore Valley Municipal Water District (EVMWD), and Temescal Valley Water District (TVWD). The BCGSA is governed by a Board of Directors (Board), composed of three governing members, one member appointed by the representatives from each agency.

The governing Board members will serve without terms, and at the discretion of the agency which appointed them. The Board designated a consultant to act as the Administrator for the BCGSA and provide administrative services as needed and required by SGMA and the BCGSA until the GSP is adopted. Information about the current BCGSA Board members can be found on the BCGSA website: https://www.bedfordcoldwatergsa.com/about-us/.

The point of contact for the BCGSA is the Plan Manager, Margie Armstrong. At the time of writing this GSP, the following is the current contact information:

BCGSA Plan Manager: Margie Armstrong
Deputy Treasurer
Bedford-Coldwater Subbasin GSA
31315 Chaney Street
Lake Elsinore, CA 92530
951-674-3146 Ext 8306
[email protected]
http://www.evmwd.com/
An organizational chart for the BCGSA is presented on Figure 1-3 below.

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Figure 1-3. BCGSA Management Structure

1.3.2. Legal Authority
A Joint Powers Agreement (Agreement) to create a Joint Powers Authority (JPA) for the management of the Basin was entered into as of February 28, 2017 (Appendix A). The Agreement to form the BCGSA is by and between Corona, a California General Law City organized and existing under the laws of the State of California, EVMWD, a Municipal Water District organized under Water Code §§ 71000 et seq., and TVWD, a California Water District organized under California Water Code §§ 34000 et seq.. BCGSA signed a resolution to become the GSA for the Basin on March 29, 2017 (Appendix B, BCGSA 2017).

1.3.3. GSP Implementation Cost Estimate and Schedule
GSP implementation cost and schedule is described in detail in Section 9, Plan Implementation. Costs associated with implementing the GSP are considered to be either continually ongoing (operating) costs, or GSP implementation costs associated with specific management actions and projects. Annual operating costs in 2021 dollars are expected to be approximately $60,000. Annual implementation of management actions is estimated at approximately $266,000 per year, while total costs for recommended, one-occurrence projects is approximately $990,000 (including the first 5-Year GSP update). Estimated costs for years after the 5-Year GSP update will be reevaluated within the first 5-Year GSP update.

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The BCGSA has committed to implementing the GSP upon adoption and completing the projects and management actions necessary to monitor and maintain sustainability within the first 5 years of initiation of the GSP. A preliminary schedule for implementation is provided in Section 9 as Figure 9-1.

1.4. GSP ORGANIZATION
This GSP was prepared according to guidance documents provided by DWR (DWR 2016a). The following outlines the GSP contents:
• Section 1 – Introduction, purpose of the GSP, sustainability goal, agency information, and GSP organization.
• Section 2 – Plan Area description, water use sectors, water supply sources, water resources monitoring and management programs, current general plans, other GSP elements.
• Section 3 – Hydrogeologic Conceptual Model, description of the physical basin setting including surface water features, soils, geologic setting, faults, and aquifers, defined basin bottom, recharge and discharge areas, and cross sections. • Section 4 – Current and Historical Groundwater Conditions, discussion of groundwater elevations, land subsidence, groundwater quality and current monitoring, constituents of concern regarding water quality, interconnection of surface water and groundwater and the effects on groundwater dependent ecosystems (GDEs).
• Section 5 – Water Budget, discussion of the water budget, groundwater model, surface water and groundwater balance, change in groundwater storage, and estimate of sustainable yield.
• Section 6 – Sustainable Management Criteria, sustainability goal, sustainability criteria for the six undesirable results.
• Section 7 – Monitoring Network, discussion of the monitoring that will continue to assess sustainability in the future.
• Section 8 – Projects and Management Actions, descriptions of projects and management actions for the Basin.
• Section 9 – Plan Implementation, estimate of GSP implementation costs, schedule, plan for annual reporting and periodic evaluations.
• Section 10 – References
The GSP Preparation Checklist providing the chapter locations for GSP content requirements is provided in Table 1-1 and the GSP Elements Guide detailing GSP content in comparison to SGMA articles is included in Appendix C. Figures in following sections are placed at the end of the section.

Table 1-1. GSP Preparation Checklist
GSP
Regulations
Section
Water Code
Section Requirement
352.2 Monitoring
Protocols
354.4 General
Information
354.6 Agency
Information
354.8(a) 10727.2(a)(4) Map(s)
354.8(b) Description of the
Plan Area
354.8(c)
354.8(d)
354.8(e)
10727.2(g) Water Resource
Monitoring and
Management
Programs
354.8(f) 10727.2(g) Land Use Elements
or Topic
Categories of
Applicable General
Plans
354.8(g) 10727.4 Additional GSP
Contents
354.10 Notice and
Communication
- Area covered by GSP (Figure 1-1)
- Adjudicated areas, other agencies within the basin, and areas covered by an Alternative (Figure 1-1) - Jurisdictional boundaries of federal or State land (Figure 2-1) - Existing land use designations (Figures 2-7, 2-8)
- Density of wells per square mile (Figures 2-3 through 2-6) Section 2
Article 5. Plan Contents, Subarticle 1. Administrative Information (Continued) - Summary of jurisdictional areas and other features
Article 5. Plan Contents, Subarticle 1. Administrative Information - List of references and technical studies Section 10
- GSA mailing address
- Organization and management structure
- Contact information of Plan Manager
- Legal authority of GSA
- Estimate of implementation costs
Section 1.3
Section 2.1
- Description of water resources monitoring and management programs - Description of how the monitoring networks of those plans will be incorporated into the GSP - Description of how those plans may limit operational flexibility in the basin - Description of conjunctive use programs
Section 2.1.4
Section 2.1.4.1
Section 2.1.4.2
Section 2.1.6
- Summary of general plans and other land use plans
- Description of how implementation of the GSP may change water demands or affect achievement of sustainability and how the GSP addresses those effects
- Description of how implementation of the GSP may affect the water supply assumptions of relevant land use plans
- Summary of the process for permitting new or replacement wells in the basin - Information regarding the implementation of land use plans outside the basin that could affect the ability of the Agency to achieve sustainable groundwater management Section 2.1.5
Section 2.1.5.3
Section 2.1.5.4
Section 2.1.5.5
Section 2.1.6
Description Section(s) or Page
Number(s) in the GSP
Article 3. Technical and Reporting Standards
- Monitoring protocols adopted by the GSA for data collection and management - Monitoring protocols that are designed to detect changes in groundwater levels, groundwater quality, inelastic surface subsidence for basins for which subsidence has been identified as a potential problem, and flow and quality of surface water that directly affect groundwater levels or quality or are caused by groundwater extraction in the basin
Section 7.2
Description of Actions related to:
- Control of saline water intrusion
- Wellhead protection
- Migration of contaminated groundwater
- Well abandonment and well destruction program
- Replenishment of groundwater extractions
- Conjunctive use and underground storage
- Well construction policies
- Addressing groundwater contamination cleanup, recharge, diversions to storage, conservation, water recycling, conveyance, and extraction projects
- Efficient water management practices
- Relationships with State and federal regulatory agencies - Review of land use plans and efforts to coordinate with land use planning agencies to assess activities that potentially create risks to groundwater quality or quantity - Impacts on groundwater dependent ecosystems
Section 2.1.6
- Description of beneficial uses and users
- List of public meetings
- GSP comments and responses
- Decision-making process
- Public engagement
- Encouraging active involvement
- Informing the public on GSP implementation progress
Section 2.1.7
Appendix J (pending)
Appendix J (pending)
Section 1.3.1
Appendix D
Section 2.1.7
Section 2.1.7
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GSP
Regulations
Section
Water Code
Section Requirement Description Section(s) or Page
Number(s) in the GSP
354.14 Hydrogeologic
Conceptual Model
9 10727.2(a)(5) Map of Recharge
Areas
10727.2(d)(4) Recharge Areas
354.16 10727.2(a)(1)
10727.2(a)(2)
Current and
Historical
Groundwater
Conditions
354.18 10727.2(a)(3) Water Budget
Information
10727.2(d)(5) Surface Water
Supply
354.20 Management
Areas
354.24 Sustainability Goal
354.26 Undesirable
Results
354.28 10727.2(d)(1)
10727.2(d)(2)
Minimum
Thresholds
354.30 10727.2(b)(1)
10727.2(b)(2)
10727.2(d)(1)
10727.2(d)(2)
Measureable
Objectives
Article 5. Plan Contents, Subarticle 2. Basin Setting
- Description of the Hydrogeologic Conceptual Model
- Two scaled cross-sections
- Map(s) of physical characteristics: topographic information, surficial geology, soil characteristics, surface water bodies, source and point of delivery for imported water supplies Section 3, Figure 3-8 and 3-
9 - Map delineating existing recharge areas that substantially contribute to the replenishment of the basin, potential recharge areas, and discharge areas
Figure 3-10
- Description of how recharge areas identified in the plan substantially contribute to the replenishment of the basin
Section 3.10
- Groundwater elevation data
- Estimate of groundwater storage
- Seawater intrusion conditions
- Groundwater quality issues
- Land subsidence conditions
- Identification of interconnected surface water systems - Identification of groundwater-dependent ecosystems
Section 4
- Description of inflows, outflows, and change in storage - Quantification of overdraft
- Estimate of sustainable yield
- Quantification of current, historical, and projected water budgets Section 5.7, Section 5.8,
and Section 5.9
- Description of surface water supply used or available for use for groundwater recharge or in-lieu use Section 2.1.2.1, Section

3.11, Section 5.6.2
- Reason for creation of each management area
- Minimum thresholds and measurable objectives for each management area - Level of monitoring and analysis
- Explanation of how management of management areas will not cause undesirable results outside the management area
- Description of management areas
Section 5.4
Article 5. Plan Contents, Subarticle 3. Sustainable Management Criteria - Description of the sustainability goal Section 6.1.1
- Description of undesirable results
- Cause of groundwater conditions that would lead to undesirable results - Criteria used to define undesirable results for each sustainability indicator - Potential effects of undesirable results on beneficial uses and users of groundwater Section 6.2.1
Section 6.2.2
Section 6.2.3
Section 6.2.4
- Description of each minimum threshold and how they were established for each sustainability indicator - Relationship for each sustainability indicator
- Description of how selection of the minimum threshold may affect beneficial uses and users of groundwater - Standards related to sustainability indicators
- How each minimum threshold will be quantitatively measured Sections 6.2 through 6.7
- Description of establishment of the measureable objectives for each sustainability indicator - Description of how a reasonable margin of safety was established for each measureable objective - Description of a reasonable path to achieve and maintain the sustainability goal, including a description of interim milestones
Sections 6.2 through 6.7
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Table 1-1. GSP Preparation Checklist

GSP
Regulations
Section
Water Code
Section Requirement Description Section(s) or Page
Number(s) in the GSP
354.34 10727.2(d)(1)
10727.2(d)(2)
10727.2(e)
10727.2(f)
Monitoring
Networks
354.36 Representative
Monitoring
354.38 Assessment and
Improvement of
Monitoring
Network
354.44 Projects and
Management
Actions
354.44(b)(2) 10727.2(d)(3)
357.4 10727.6 Coordination
Agreements - Shall
be submitted to
the Department
together with the
GSPs for the basin
and, if approved,
shall become part
of the GSP for
each participating
Agency.

Article 5. Plan Contents, Subarticle 4. Monitoring Networks - Description of monitoring network
- Description of monitoring network objectives
- Description of how the monitoring network is designed to: demonstrate groundwater occurrence, flow directions, and hydraulic gradients between principal aquifers and surface water features; estimate the change in annual groundwater in storage; monitor seawater intrusion; determine groundwater quality trends; identify the rate and extent of land subsidence; and calculate depletions of surface water caused by groundwater extractions
- Description of how the monitoring network provides adequate coverage of Sustainability Indicators - Density of monitoring sites and frequency of measurements required to demonstrate short-term, seasonal, and long-term trends
- Scientific rational (or reason) for site selection
- Consistency with data and reporting standards
- Corresponding sustainability indicator, minimum threshold, measureable objective, and interim milestone - Location and type of each monitoring site within the basin displayed on a map, and reported in tabular format, including information regarding the monitoring site type, frequency of measurement, and the purposes for which the monitoring site is being used
- Description of technical standards, data collection methods, and other procedures or protocols to ensure comparable data and methodologies
Section 7.1
Section 7.0
- Description of representative sites
- Demonstration of adequacy of using groundwater elevations as proxy for other sustainability indicators - Adequate evidence demonstrating site reflects general conditions in the area Section 7.3
- Review and evaluation of the monitoring network
- Identification and description of data gaps
- Description of steps to fill data gaps
- Description of monitoring frequency and density of sites Section 7.5
Section 7.5.1
Section 7.5.2
Section 7.1.1
Article 5. Plan Contents, Subarticle 5. Projects and Management Actions Article 8. Interagency Agreements
Coordination Agreements shall describe the following:
- A point of contact
- Responsibilities of each Agency
- Procedures for the timely exchange of information between Agencies - Procedures for resolving conflicts between Agencies
- How the Agencies have used the same data and methodologies to coordinate GSPs - How the GSPs implemented together satisfy the requirements of SGMA - Process for submitting all Plans, Plan amendments, supporting information, all monitoring data and other pertinent information, along with annual reports and periodic evaluations - A coordinated data management system for the basin
- Coordination agreements shall identify adjudicated areas within the basin, and any local agencies that have adopted an Alternative that has been accepted by the Department N/A
- Description of projects and management actions that will help achieve the basin’s sustainability goal - Measureable objective that is expected to benefit from each project and management action - Circumstances for implementation
- Public noticing
- Permitting and regulatory process
- Time-table for initiation and completion, and the accrual of expected benefits - Expected benefits and how they will be evaluated
- How the project or management action will be accomplished. If the projects or management actions rely on water from outside the jurisdiction of the Agency, an explanation of the source and reliability of that water shall be included.
- Legal authority required
- Estimated costs and plans to meet those costs
- Management of groundwater extractions and recharge
Section 8.0
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Table 1-1. GSP Preparation Checklist

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2. PLAN AREA
The following section, consistent with GSP Regulations §354.8, provides a description of the Plan Area.

The Bedford-Coldwater Subbasin (Basin) has been the focus of historical and ongoing collaborative groundwater basin management among three key agencies: City of Corona (Corona), Elsinore Valley Municipal Water District (EVMWD), and Temescal Valley Water District (TVWD). As noted in Chapter 1 of this Groundwater Sustainability Plan (GSP), the Basin is currently listed by the Department of Water Resources (DWR) as a very low priority groundwater basin. Therefore, preparation of a GSP is not required. The agencies that have been collaborating to manage the Basin, through the Bedford-Coldwater Groundwater Sustainability Agency (BCGSA), have confirmed their collective dedication to management for groundwater sustainability and have decided to prepare a GSP.

2.1. DESCRIPTION OF THE PLAN AREA
The following provides a general description of the Bedford-Coldwater Basin, including local jurisdictions, water resource management and monitoring programs, well permitting procedures, general plans and otherland use plans, and additional groundwater management elements.

2.1.1. Geographic Area
Figure 1-1 shows the boundaries of the Plan Area, namely the Bedford-Coldwater Groundwater Subbasin located in western Riverside County. Figure 1-1 also shows the adjacent Temescal Basin to the northwest (separated by a groundwater divide near Bedford Wash) and Elsinore Valley Subbasin located on the southern boundary. Both the Elsinore Valley Groundwater Sustainability Agency (GSA) and Temescal Subbasin GSA are in the process of developing GSPs for their respective subbasins. Bedford-Coldwater Basin is bound on the east and west by consolidated rocks of Estelle Mountain and the Santa Ana Mountains, respectively. The major drainage is Temescal Wash, traverses the three groundwater basins along its 26-mile course from Lake Elsinore to the Prado Wetlands on the Santa Ana River.

2.1.2. Jurisdictional Agencies
This section identifies agencies with land use management responsibilities. There are no economically distressed areas, disadvantaged communities, or severely disadvantaged communities in the Basin.

County. The Basin is located wholly within Riverside County. Riverside County has jurisdiction for land use planning for unincorporated areas. Riverside County also has responsibility for small water systems in the County that have between 15 and 199 service connections and those serving restaurants, schools, and industry. It also provides limited regulatory oversight to those water systems serving between 5 and 14 service connections. The County oversees

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on-site wastewater treatment systems (OWTS) through its Department of Environmental Health. The Department of Environmental Health also evaluates existing residential water wells and makes a determination if the water meets certain minimum standards.

City of Corona. Figure 2-1 shows the boundaries of the other jurisdiction that has land use management responsibilities, the City of Corona. General plan elements relevant to the GSP are discussed in Section 2.1.3. In addition to land use planning, Corona Department of Water and Power is responsible for stormwater management, sewage collection, and production and distribution of potable water for Corona, including the portion within the Basin.

Federal Lands. Federal lands within the Basin include United States Department of Agriculture Forest Service – Cleveland National Forest. The area is managed by the Forest Service.

Tribal Lands. There are no tribal lands in the Basin, however some tribes are included as stakeholders on the list of interested parties. The list of interested parties was developed to encourage public participation from any and all local and regional agencies, entities, and individuals. The list included tribes with land in the region even though they do not have land within the Basin. The BCGSA agencies have a long history of coordination with the regional tribal entities, and they always inform these entities of upcoming planning and/or infrastructure projects. The regional tribal entities take an interest in planning and infrastructure projects within the Basin and surrounding areas because there are important cultural resource sites within these areas. The BCGSA agencies and regional tribal entities coordinate to assess infrastructure project sites prior to groundbreaking to identify and protect potential cultural resources.

California Conservation Easement. According to the California Conservation Easement Database (CCED) there is an area of private land, Lee Lake Easement, with deed-based restrictions to limit land uses to those compatible with its status as open space. Lands under easement may be actively farmed, grazed, forested, or held as nature reserves. Easements are typically held on private lands with no public access. CCED represents California in the National Conservation Easement Database (NCED 2019), a national inventory of lands conserved as easements. NCED is managed by a consortium of non-governmental organizations including: Ducks Unlimited, the Trust for Public Land, Defenders of Wildlife, Conservation Biology Institute, and NatureServe.

Other. There are no state park lands or land owned by the California Department of Fish & Wildlife (CDFW) within the Basin.

2.1.3. Disadvantaged Communities
There are no disadvantaged communities (DACs) or severely disadvantaged communities (SDACs) mapped within the Basin (DWR 2019c).

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2.1.4. Water Supply Sources
Sources for water supply for agricultural, Municipal and Industrial (M&I), and domestic uses include groundwater, imported water, and recycled water. Metropolitan Water District of Southern California (Metropolitan) is the wholesaler for imported water and its sources of water include the Colorado River and the State Water Project. Both Corona and TVWD receive imported water from Metropolitan for distribution in the Basin. EVMWD also receives imported water from Metropolitan through Western Municipal Water District (WMWD), but only distributes imported water within the Basin when groundwatersupply to domestic users is insufficient.

Water Providers. The BCGSA was created through a Joint Powers Authority agreement between Corona, EVMWD, and TVWD. Figure 2-2 shows the service areas of these providers.

Othersmallsystems are operated by private mutual water companies and some communities do not have water purveyors and systems that provide water service. These small systems and communities—plus rural businesses, schools, parks, and residents—rely on private wells and groundwater.
• City of Corona. A portion of the City of Corona overlies the Basin, amounting to 1,213 acres or about 5 percent of the city’s area. Corona maintains three treatment facilities and serves water to more than 150,000 residents with water supply from a combination of imported water and groundwater.
• Temescal Valley Water District (TVWD). TVWD is the primary purveyor in the BCGSA. TVWD, formed in 1965 as Lee Lake Water District, provides water and wastewater services to the residents of the Temescal Valley in an area covering approximately 6,730 acres.
• Elsinore Valley Municipal Water District (EVMWD). EVMWD supplies water to customers within the Basin from a combination of groundwater and imported water supply sources.

Groundwater. Groundwater currently is a source of water supply in the Basin. Corona, EVMWD, and TVWD all pump groundwater from the Basin. Corona and EVMWD distribute this supply to users within and outside the Basin, while TVWD only supplies groundwater to users within the Basin. There are also a few private users that pump groundwater within the Basin. Groundwater produced within the Basin is used to supply municipal, agricultural, mining, recreational, and domestic uses and users throughout the Basin and in the neighboring Temescal and Elsinore Valley Subbasins (DWR 2019a).

Water Supply Wells. Figure 2-3 shows the density of water supply wells in and around the Plan Area; this map is based on the DWR Well Completion Report Map Application tool (DWR 2019b). As indicated, the density of supply wells is generally less than nine wells per square mile. Relatively high densities occur around the northern margins of the Basin, where the Corona and EVMWD wells are located. Figures 2-4, 2-5, and 2-6 show the estimated density of domestic wells, production wells, and public wells. Most of the production wells, as

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classified by DWR, are presumably irrigation wells but also include some industrial and commercial wells.

Outside of the three major purveyors, there is only one public water system; Glen Ivy Hot Springs has one well and serves an estimated population of 750 people. The Glen Ivy Hot Springs well is located in the southwestern portion of the Basin (Figure 2-2).

The BCGSA is aware that there are a small number of private wells used for non-potable supply in the Basin. However, a systematic well inventory identifying all active private wells has not been completed to date. This has been identified as a data gap in the GSP, as described in Section 6.2.7.1. The GSP also includes a project to address this data gap with a survey and inventory of active private wells throughout the Basin (Project 2, Section 8.7). This project was designed to locate and characterize the construction and use of existing private wells so that they can be included in sustainable management of the Basin.

Imported Water. Corona, TVWD, and EVMWD rely on imported water from Metropolitan.

Metropolitan imports water to Southern California from two main sources: the Sacramento and San Joaquin Rivers through the State Water Project and the Colorado River via the Colorado River Aqueduct. Corona receives imported water from Metropolitan through WMWD. Temescal Valley Water District receives State Water Project imported by Metropolitan and treated at the Henry J. Mills Treatment Plant in Riverside. EVMWD also receivesimported waterfrom Metropolitan through WMWD, but only distributes to domestic users if groundwater isinsufficient. Imported water and other water infrastructure are shown on Figure 2-7.

Recycled Water. Water recycling occurs in both Corona and TVWD. Recycled water use is a relatively small but increasing supply. In TVWD, recycled water is distributed to multiple sites within TVWD’s service area, including the Retreat Golf Course in the northern portion of the Basin and the Deleo Sports Park along Sycamore Creek in the south Basin (RMC and Woodard & Curran 2017).

2.1.5. Water Use Sectors
Water use sectors are defined in the GSP Regulations as categories of water demand based on the general land usesto which the wateris applied, including urban, industrial, agricultural, managed wetlands, managed recharge, and native vegetation. In the Basin, these are summarized as follows:
• Urban water use sectors are focused in the City of Corona area but extend through the center of the Basin.
• Areas of industrial water use are limited.
• Agricultural land uses comprise limited areas of citrus in the southwestern portion of the Basin (20.5 acres).
• There is no current managed aquifer recharge in the Basin. • Native vegetation, including rangeland, accounts for the remainder including upland areas and along streams.

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2.1.6. Water Resources Monitoring and Management Programs This section summarizes water resources monitoring and management in the Basin. Corona, EVMWD, and TVWD have entered into a Joint Powers Authority (JPA) agreement for the purpose of forming and executing the responsibilities of the BCGSA in accordance with the Sustainable Groundwater Management Act (SGMA). The BCGSA encompasses the entirety of the Bedford-Coldwater Subbasin of the Elsinore Groundwater Basin (Basin 8-004.2, DWR 2016b).

Groundwater has been an important component of water supply in the Basin for more than 100 years. Until the 1970s, most of the groundwater production in the Basin was for agricultural supply (Todd and AKM 2008). A few well owners have also produced small amounts of groundwater for domestic use (Todd and AKM 2008). Production for municipal supply increased in the 1960s and 1970s and continues today.

For more than 50 years, Corona, EVMWD, and TVWD have relied on groundwater from the Basin for municipal use, and these agencies have long been responsible for managing groundwater conditions in the Basin. Corona and EVMWD have longstanding legal agreements for the management of withdrawals from the Coldwater area portion of the Basin. Additionally, Corona, in coordination with TVWD, adopted a Groundwater Management Plan (GWMP) in 2008 that covers the Basin.

In 2008, Corona and EVMWD established a legal agreement for the Coldwater portion of the Basin where most of the pumping occurs. The 2008 agreement is intended to enhance groundwater supply in order to maximize the sustainable use of groundwater. One of the goals of the agreement is to give Corona and EVMWD the ability to estimate annual groundwater production that ensures the sustainability of the Subbasin as a water supply.

Historically, Corona and EVMWD account for most of the production in the Basin, with Corona historically pumping about twice as much as EVMWD (Todd and AKM 2008). The agreement is based on this historical distribution of groundwater use and also recognizes the presence of private pumpers in the Basin. This agreement allots four percent of annual groundwater use to private pumpers.

The agreement encourages development of joint groundwater management projects to enhance recharge including the recharge of local surface water by both parties. EVMWD also has surface water rights in the Basin that can be used for recharge enhancement. The 2008 agreement provides a process for allocating production on an annual basis, accounting for production rights and a groundwater storage account. Every five years, the native safe yield is re-evaluated, and each party’s share of that yield is adjusted. To date, four annual reports have been completed (WEI 2016 and 2017b).

The only pumpers in the Bedford area of the Basin are the three agencies of the BCGSA.

Corona and TVWD service areas cover almost all of the Basin; those portions outside of these service areas are not within the service area of any local water agency. The BCGSA is coordinating with Riverside County and other agencies for these areas.

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2.1.6.1. Water Resource Monitoring
The overall objective of the monitoring networks for this GSP is to yield representative information about water conditions in the Basin as necessary to guide and evaluate GSP implementation. Water resource monitoring programs considered in this section include:
• Climate
• Surface water flows
• Imported water deliveries
• Water recycling
• Land use and cropping
• Wells and groundwater pumping
• Groundwater levels
• Land subsidence
• Water quality
Monitoring programs undertaken by local, state, and federal agencies are summarized below as they are relevant to the GSP.

Climate. Climate data collection stations and records have been reviewed and assessed for the Basin and surrounding areas. Previous investigations (Todd and AKM 2008, SAIC 2007, MWH 2004) have revealed substantial variability in precipitation amounts because of elevation differences between the Temescal Valley and the nearby Santa Ana Mountains.

These orographic effects result in significantly more precipitation on the upland areas of the watersheds that contribute to the Basin. However, operational rain gages exist only in EVMWD, Riverside, and at the top of Santiago Peak. Therefore, precipitation on the Basin itself and on the slopes of the Santa Ana Mountains below Santiago Peak must be modeled.

There are three currently active climate monitoring stations near the Basin: the Lake Elsinore station maintained by the National Oceanic Atmospheric Administration (NOAA),the Santiago Peak station maintained by Orange County, and the UC Riverside California Irrigation Management Information System (CIMIS). The Lake Elsinore and UC Riverside stationsinclude daily precipitation and evapotranspiration data; the Santiago Peak station collects monthly precipitation data. Monthly data for the Santiago Peak station are from January 1949 to current, with a slight lag on recent data. The Lake Elsinore station has daily data from January 1961 through current, and monthly data from 1897. The UC Riverside station has daily data from January 1986 through the present.

In addition to station-specific climate records, PRISM Climate Group (PRISM) data are also available. PRISM gathers climate observations from a wide range of monitoring networks, applies sophisticated quality control measures, and develops spatial climate datasets. These datasets incorporate a variety of modeling techniques and are available at multiple resolutions covering the period from 1895 to the present. These datasets include elevationvarying average precipitation isohyets that can be used to estimate or simulate precipitation throughout the watershed contributing to the Basin (PRISM 2018).

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Surface water flows. There are three streamflow gage stations near the Basin that are maintained by the United States Geological Survey (USGS 2018). These stations are located on Temescal Creek at about Main Street in Corona (USGS 11072100), Temescal Creek at Corona Lake (USGS 11071900), and San Jacinto River near Elsinore (USGS 11070500). These stations are all active and have records that begin in October 1980, November 2012, and January 1950, respectively.

Imported water deliveries. Imported water data and locations are monitored and available from Corona, EVMWD, and TVWD. Data are available monthly for Corona from 2005 to present, annually for TVWD from 1990 to present, and monthly for EVMWD from 1995 to present.

Recycled water. Corona and TVWD monitor and maintain records of recycled water use records and distribution locations. TVWD supplies non-potable recycled water to Retreat Golf Course on the north end of the Basin and the Deleo Sports Park along Sycamore Creek on the south end.

Wells and groundwater pumping. Groundwater production in the Basin is tracked by the Santa Ana River Watermaster, along with production in the rest of the watershed. WMWD currently coordinates groundwater use data collection.

Groundwater levels. Multiple agencies have historically monitored groundwater levels in the Basin, including Corona, EVMWD, USGS, and DWR.

Land use. Land use map data were collected from DWR, the California Department of Conservation Farmland Mapping and Monitoring Program (FMMP), and Riverside County. The available land use maps are indicated below:
• DWR: 2014 statewide land use mapping specifically developed for SGMA and GSPs. • FMMP: 1984, 1986, 1988, 1990, 1992, 1994, 1996, 1998, 2000, 2002, 2004, 2006, 2008, 2010, 2012, 2014, and 2016
• Riverside County: 1993 and 2000
Agricultural land is currently limited to approximately 20.5 acres of citrus/subtropical fruits (avocados and others) located on the southwestern edge of the Basin.

Land subsidence. While the potential for subsidence was recognized in the 2008 Groundwater Management Plan, it has not been a known issue in the Basin and ground surface elevations have not been monitored until recently. The TRE Altamira Interferometric Synthetic Aperture Radar (InSAR) Dataset, provided by DWR through the SGMA Data Viewer (DWR 2019c) and showing vertical ground surface displacement from June 2015 to June 2018, indicates that the Basin has been characterized by uplift over that period, likely reflecting tectonic factors. No known available sources of data indicate subsidence in the Basin.

Groundwater levels have been managed to stay above historical low levels to minimize the potential for ground settlement.

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Water quality. Groundwater quality in the Basin is monitored by the BCGSA agencies and Glen Ivy Hot Springs for compliance with State Water Resources Board Division of Drinking Water (DDW) requirements, and by facilities regulated by the Santa Ana Regional Water Quality Control Board (RWQCB).

Section 7 of this GSP documents the BCGSA monitoring network including how these objectives are met, descriptions of how each sustainability criteria will be monitored, and protocols for measurements.

2.1.6.2. Water Resources Management
This section describes the water resources management plans developed for the Plan Area; note that monitoring is addressed in Section 2.1.4.1.

Groundwater Management Plan, 2008. A GWMP was adopted in 2008 that covers the Basin.

The GMP included projects in the Bedford-Coldwater area including the Coldwater Subbasin Enhanced Recharge Project and Lee Lake Water District’s (now TVWD) Recharge to Bedford Subbasin. The GMP includes a quantitative water balance forthe area, but Bedford-Coldwater was not included in the numerical model developed to evaluate management programs and projects (Todd and AKM 2008).

Numerical Groundwater Modeling. There is no pre-existing numerical model that covers the entire Basin. A model of the Coldwater area was prepared by MWH in 2004 (MWH 2004), and this is the only numerical groundwater model covering any portion of the Basin. This model is documented in the Coldwater Basin Recharge Feasibility Study (MWH 2004). Numerical groundwater modeling for the purpose of the GSP is discussed in later chapters of this document.

Integrated Regional Water Management Plan (IRWMP), 2008. The IRWMP is a collaborative effort led by WMWD to identify regional and multi-benefit projects within member agencies service areas. Adopted in 2008, the IRWMP describes the region, provides goals and objectives, and identifies and evaluates projects and programs, including assessment of climate change.

The IRWMP identifies and prioritizes integrated regional projects for the watershed to maximize benefits to the broadest group of stakeholders in the region. Projects in the Bedford-Coldwater area include new water wells for Corona and managed recharge using recycled water infiltration in surface recharge basins or injection wells in the Bedford area (Kennedy/Jenks 2008a and 2008b).

Salt and Nutrient Management Plan (SNMP), 2017. SNMPs are required for groundwater basins throughout California and are intended to help streamline permitting of new recycled water projects while ensuring attainment of water quality objectives and protection of beneficial uses. The Upper Temescal Valley (UTV) SNMP prepared by WEI was a joint management plan, prepared by the EVMWD and the Eastern Municipal Water District (EMWD) (WEI 2017a).

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Wastewater services include the treatment of wastewater generated in their respective service areas and the subsequent discharge and reuse of treated wastewater, hereafter referred to as recycled water. The goal of the SNMP was to define management activities to comply with the total dissolved solids (TDS) and nitrate concentration objectives of the groundwater management zones (GMZs) and surface water bodies that are impacted by recycled water discharge and reuse in the UTV Watershed. The UTV SNMP recommends updates to the Water Quality Control Plan for the Santa Ana River Basin (Basin Plan) for water quality objectives for the entire upper Temescal Valley but does not provide objectives for individual GMZs. Water quality objectives and ambient water quality numbers were estimated for both TDS and nitrate for the entire UTV SNMP. Ambient water quality will be recomputed periodically.

Recycled Water Plans 2007 through 2016. TVWD prepared a series of plans for its recycled water, including assessment of system-wide impacts to groundwater quality. The planning documents include:
• Recycled Water Master Plan (Lee Lake Water District 2007). • Water System Master Plan (Lee Lake Water District 2014). • Temescal Valley Water District Comprehensive Water, Recycled Water, and Wastewater Cost of Service Study Report (Raftelis 2016).

Water Quality Control Plan for the Santa Ana Region. The Basin Plan was approved in 1994 and provides the framework for how surface water and groundwater quality in the Santa Ana Region should be managed to provide the highest water quality reasonably possible. The Basin Plan lists beneficial uses, describesthe water quality which must be maintained to allow those uses, provides an implementation plan, details State Water Resources Control Board (SWRCB) and RWQCB plans and polices to protect water quality, and presents surveillance and monitoring programs. The most recent update in 2004 revises groundwater basin boundaries, updates beneficial uses, and presents GMZ water quality objectives.

Urban Water Management Plans (UWMPs). The California Urban Water Management Planning Act requires preparation of UWMPs by urban water providers with 3,000 or more connections. The UWMPs, generally required every five years, provide information on water supply and water demand—past, present, and future—and allow comparisons as a basis for ensuring reliable water supplies. UWMPs examine water supply and demand in normal years and during one-year and multi-year droughts. UWMPS also provide information on per-capita water use, encourage water conservation, and present contingency plans for addressing water shortages. UWMPs have been prepared for Corona, TVWD, and EVMWD (KWC 2016, RMC and Woodard & Curran 2017, MWH 2016).

Despite challenges of drought, climate change, and environmental and legal factors, the three agencies have been able to provide reliable supply. This has been achieved by actively managing the portfolio of water supplies (groundwater, imported water, recycled water), by improving facilities (e.g., water treatment plants), and by promoting conservation.

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2.1.7. General Plans, Land Use Planning, and Well Permitting This section presents elements of General Plans and other land use planning in the Basin as relevant to groundwater sustainability. It summarizes the goals, objectives, policies, and implementation measures as variously described in the General Plans for Riverside County and the City of Corona, which together encompass the Basin. This section also summarizes local well permitting procedures and well ordinances.

2.1.7.1. Land Use
The Basin includes developed urban area, rural residential areas, and limited agriculture.

Figure 2-8 shows land use for 2014 (DWR 2017), which indicates that active agricultural land was limited to 20.5 acres of primarily subtropical orchard in the southwestern Basin.

2.1.7.2. General Plans
Land use planning within the Basin is guided by the General Plans for Riverside County and the City of Corona.

Riverside County General Plan. The Riverside County General Plan, adopted in 2015, incorporates a set of 15 Consensus Planning Principles drafted and endorsed by a coalition of Riverside County stakeholders. The General Plan encourages water use efficiency and requires that new developments incorporate water conservation techniques, such as groundwater recharge basins, use of porous pavement, drought tolerant landscaping, and water recycling, as appropriate. Additional policies ensure compliance with water efficient landscape principles, promote water conservation, and encourage the use of recycled water (Riverside County 2015).

Figure 2-9 shows general Land Use Planning Designations of the Riverside County General Plan throughout the Basin. As indicated, broad areas are designated as low and medium density residential with commercial and industrial areas near the freeway.

City of Corona General Plan. The Corona General Plan (EIP Associates 2020) was adopted in 2004 and is scheduled for update beginning in 2019. Figure 2-9 shows the Corona planning area, including portions of the Basin.

Goals, policies, and implementation measures with relevance to groundwater sustainability include:
• Policy 1.1.4 – Accommodate the types, densities, and mix of land uses that can be adequately supported by transportation and utility infrastructure (water, sewer, etc.) and public services (schools, parks, libraries, etc.) • Policy 1.5.14 – Require that developers demonstrate water conservation in the landscape design of their proposed projects, such as the use of drought-tolerant species.
• Policy 1.5.16 – Promote the use of recycled water for landscape irrigation, where feasible.

Bedford-Coldwater GSP 2-11

TODD GROUNDWATER,
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In addition, there are several policies linked to the development of water infrastructure to ensure that water supply and treatment and delivery systems are sustainable and cost efficient. Other policies protect water quality and minimize impact on water resources.

2.1.7.3. General Plan Influences on GSA Ability to Achieve Sustainability Riverside County. The Riverside County General Plan addresses the importance of groundwater. The policies and implementation of the land use and public facilities/services elements indicate that the County role is to support and encourage local water agencies in ensuring that water supply is available. Similarly, with wastewater issues and protection of water quantity and quality, the County role is limited to encouragement of other agencies, developers, and landowners. The General Plan containslittle policy to manage land use within the constraints of available water supply other than to encourage drought resistant plants and the use of recycled water. In the Bedford-Coldwater area, the general plan provides land use designations in the Temescal Canyon Area Plan that were used to estimate future growth.

City of Corona. Corona serves a population that is predicted to increase from 170,100 in 2020 to about 182,800 residents by 2040 (KWC 2016). Some of this growth will be along the southern edge of Corona in the Eagle Creek area within and adjacent to the Basin. The general plan indicates that Metropolitan may build an additional treatment plant in the area to meet increased water demand. Corona land use policies generally are protective of agricultural land and hillsides, and conservation policies address water efficiency, water recycling, sustainability measures, and coordination with other agencies, including TVWD.

The increased development included in the general plans was simulated by the numerical model described in Section 5 and Appendix G. Based on these scenarios, the basin remains sustainable even with this projected development.

2.1.7.4. GSP Influences on General Plans
The BCGSA agencies will work together to implement this GSP and rely on their portfolio of watersupply to maintain sustainability. While future growth is expected based on the general plans, the agencies are committed to their agreements to limit pumping in Coldwater based on sustainable yield and import additional supplies to Bedford.

City of Corona. Implementation of the GSP will support Corona in providing continued groundwater that may be exported from the Basin to other areas of Corona. In addition, the GSP will ensure good quality water in sufficient quantities to serve its residents into the future, including drought periods.

Riverside County. The Riverside County General Plan generally assumes that local water agencies can ensure adequate high-quality water supplies into the future. The GSP provides additionalspecific information, documents potential challengesto watersupply, and explores undesirable results that may occur with future increases in groundwater demand.

Undesirable results will be defined with sustainability criteria, and if identified, will be addressed with management actions. These management actions may have ramifications for County land use planning. For example, GSPs are authorized within the GSP Plan Areas to impose well spacing requirements and control groundwater pumping and control extractions

Bedford-Coldwater GSP 2-12

TODD GROUNDWATER,
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by regulating, limiting, or suspending extractions from individual groundwater wells. Such regulation may present a constraint on potential land uses.

2.1.7.5. Well Permitting
Groundwater well permitting within the Basin is currently regulated by the Riverside County Department of Environmental Health as described in Riverside County Ordinance No. 682 (as amended through 684.4). The purpose of this ordinance is to provide minimum standards for construction, reconstruction, abandonment, and destruction of all wells in order to: (a) protect underground water resources, and (b) provide safe water to persons within Riverside County pursuant to the authority cited in Chapter 13801(c) of the California Water Code.

Wells regulated by Ordinance No. 682 include drinking water (domestic, industrial, community, or springs), agricultural, monitoring, and cathodic protection wells.

This ordinance is similar to the California State Guidelines for new wells under California Water Code Sections 13800 to 13806, which stipulates that local jurisdictions, including counties, cities, and water districts, have authority under the Water Code to adopt local well ordinances that meet or exceed the statewide standards. The Riverside County requirements exceed statewide standards with greater setback requirements from potentially contaminating activities such as septic systems.

The existing well permitting by the Riverside County Department of Environmental Health is the adopted standard for well permitting in this GSP.

2.1.8. Notice and Communication
As described in this section, groundwater is a source of supply in the Basin and supports a range of beneficial uses: agricultural, municipal, rural, and environmental. To some degree in the Basin, all land and property owners, residents, businesses, employees, farmers, and visitors are potentially affected by groundwater use.

The BCGSA have encouraged public participation in the ongoing planning and development activities supporting the GSP process. Domestic well owners were invited to participate and provide information on their wells, but none responded to the BCGSA data request. The BCGSA solicited information from private well owners during public meetings and through email and postal outreach but received no response. No well owners expressed concern with the GSP development.

Public workshops regarding development of the GSP have been conducted to encourage public participation and to provide educational outreach. Meeting notices have been provided to the list of interested parties that is maintained pursuant to Water Code Section 10723.2. Additionally, GSP development information and meeting notices have been posted to the BCGSA website.

Recognizing the importance of communication, multiple and diverse agencies and interested parties have been identified. These are listed in the BCGSA Stakeholder Outreach Plan, which is included as Appendix D.

Bedford-Coldwater GSP 2-13

TODD GROUNDWATER,
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In addition to quarterly BCGSA Board of Directors meetings open to the public, the BCGSA held two dedicated public meetings presenting information related to and components of the GSP. Summaries of these public meetings are presented in Appendix E.

On June 7, 2021, the BCGSA notified stakeholders, including local City and County agencies, of their intent to adopt this GSP after a 90-day review period. One letter with comments on the GSP was received in early September. This letter along with responses from the BCGSA and indications of how the GSP has been modified are included in Appendix F.

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* The Public Land Survey System (PLSS) is a way of subdividing and describing land in the United States. PLSS Sections are one-mile square rectangular grids of 640 miles each. All lands in the public domain are subject to subdivision by this rectangular system of surveys, which is regulated by the U.S. Department of the Interior, Bureau of Land Management (BLM). ("N 0 1,750 3,500
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Estimated Density of
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* The Public Land Survey System (PLSS) is a way of subdividing and describing land in the United States. PLSS Sections are one-mile square rectangular grids of 640 miles each. All lands in the public domain are subject to subdivision by this rectangular system of surveys, which is regulated by the U.S. Department of the Interior, Bureau of Land Management (BLM). ("N 0 1,750 3,500
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* The Public Land Survey System (PLSS) is a way of subdividing and describing land in the United States. PLSS Sections are one-mile square rectangular grids of 640 miles each. All lands in the public domain are subject to subdivision by this rectangular system of surveys, which is regulated by the U.S. Department of the Interior, Bureau of Land Management (BLM). ("N 0 1,750 3,500
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Statewide Crop Mapping 2014
DWR Standard Legend (modified for remote sensing)
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T | Truck, Nursery, and Berry Crops
F | Field Crops
C | Citrus and Subtropical
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Riverside County General Plan Designations
Very Low to Low Density Residential
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Corona General Plan Designations
Low to Medium Density Residential
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Bedford-Coldwater GSP 3-1

TODD GROUNDWATER,
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and Stantec

3. HYDROGEOLOGIC CONCEPTUAL MODEL
This chapter describes the hydrogeologic conceptual model of the Bedford-Coldwater Subbasin (Basin), including the basin boundaries, geologic formations and structures, and principal aquifer units. The chapter also addresses the interaction between groundwater and surface water and discusses groundwater recharge and discharge areas. The Hydrogeologic Conceptual Model presented in this chapter is a summary of relevant and important aspects of the Basin hydrogeology that influence groundwater sustainability. While the Chapter 1 Introduction and Chapter 2 Plan Area establish the institutional framework for sustainable management, this chapter, along with Chapter 4 Groundwater Conditions and Chapter 5 Water Budget, sets the physical framework.

The hydrogeologic conceptual model and basin conditions sections serve to document the technical aspects of the Basin’s hydrogeology. Later sections including the water budget and sustainability criteria will refer to and rely on the technical material contained here.

3.1. PHYSICAL SETTING AND TOPOGRAPHY
The Basin underlies a portion of the Elsinore Valley in western Riverside County and covers approximately 11 square miles. The Basin is adjacent to two other groundwater basins: the Temescal Subbasin of the Upper Santa Ana Basin to the north and the Elsinore Valley Subbasin of the Elsinore Basin to the south. Figure 3-1 illustrates the topography of the Basin and surrounding uplands.

Ground surface elevations along the valley floor are generally flat. Elevations range from approximately 1,000 feet above mean sea level (msl) at the northern boundary to approximately 1,200 feet above msl to the south, as shown by 200-foot contours on Figure 3-

1. The tributary watersheds reach up to more than 5,600 feet msl at the highest peak in the Santa Ana Mountain watersheds west of the Basin. Watersheds east of the Basin are significantly lower in elevation and rise only to about 1,800 feet.

Annual precipitation variesfrom below 12 inchesto more than 26 inches over the Study Area.

The long-term average annual rainfall is between 12 and 14 inches per year on the Basin floor and increases to more than 20 inches along the top of the local watersheds in the Santa Ana Mountains to the west.

3.2. SURFACE WATER FEATURES
Figure 3-2 shows surface water features including rivers, streams, springs, seeps, lakes, and ponds. The sub-watershed boundaries that drain into and through the Basin are shown on Figure 3-3.

The Basin covers a portion of the Santa Ana River watershed. Main tributaries to the Santa Ana River include Temescal Wash which flows through the Basin from the southeast to northwest and the Bedford Wash flowing toward the northeast along the northern boundary

Bedford-Coldwater GSP 3-2

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of the Basin. These waterways are ephemeral and are dry much of the year, flowing mainly during the winter.

3.3. SOILS
Characteristics of soils are important factors in natural and managed groundwater infiltration (recharge) and are therefore an important component of a hydrogeologic system. Soil hydrologic group data from the U.S. Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Soil Survey Geographic Database (SSURGO) (NRCS 2019) are shown on Figure 3-4. The soil hydrologic group is an assessment of soil infiltration rates determined by the water transmitting properties of the soil, which include hydraulic conductivity and percentage of clays in the soil, relative to sands and gravels. The groups are defined as:
• Group A – High Infiltration Rate: water is transmitted freely through the soil; soils typically less than 10 percent clay and more than 90 percent sand or gravel. • Group B – Moderate Infiltration Rate: water transmission through the soil is unimpeded; soils typically have between 10 and 20 percent clay and 50 to 90 percent sand.
• Group C – Slow Infiltration Rate: water transmission through the soil is somewhat restricted; soils typically have between 20 and 40 percent clay and less than 50 percent sand.
• Group D – Very Slow Infiltration Rate: water movement through the soil is restricted or very restricted; soils typically have greater than 40 percent clay, less than 50 percent sand.

The hydrologic group of the soil generally correlates with the potential forinfiltration of water to the subsurface. However, there is not necessarily a correlation between the soils at the ground surface and the underlying geology or hydrogeology.

3.4. GEOLOGIC SETTING
The Basin is located within one of the structural blocks of the Peninsular Ranges of Southern California. The Basin occurs in a linear low-lying block, referred to as the Elsinore-Temecula trough, between the Santa Ana Mountains on the west and the Perris Plain on the east (Norris and Webb 1990). The trough extends from Corona to the southeast some 30 miles and was formed along an extensive northwest-southeast trending fault zone including the Elsinore, Chino, and related faults. The Elsinore faultzone, including the Glen Ivy Fault, bound the Basin on the west and trend along the mountain front.

As shown on Figure 3-5, the oldest rocks in the Study Area crop out in the Santa Ana Mountains. These uplands are composed principally of volcanic (including the Santiago Peak Volcanics) and metamorphic rocks (including the Bedford Canyon Formation) of Jurassic and Cretaceous age. A thin rim of younger sedimentary units of Tertiary age crops out along the mountain front generally lying east of the Glen Ivy Fault within the Elsinore Fault Zone.

Bedford-Coldwater GSP 3-3

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This zone of sedimentary units broadens to the north and contains numerous mapped formations of Cretaceous and Tertiary age. The northeastern side of the valley is flanked primarily by granitic rocks of Cretaceous age. Erosion of these units has filled in the trough over time resulting in quaternary-age alluvial fan, channel, and other deposits making up the permeable portions of the groundwater Basin (Todd and AKM 2008).

The Elsinore Fault Zone forms a complex series of pull-apart basins(Morton and Weber 2003).

The deep portion of the Basin in the Coldwater area is one of these pull-apart basins. Pullapart basins are topographic depressions that form at releasing bends or steps in basement strike-slip fault systems. This initial deposition into the Basin is composed of rapid deposition of landslide and debrisflow deposits which are extremely poorly sorted with a mixture of clay, sand, gravel, and boulders asseen in deep well logs. Since the movement on the faultsisrightlateral, the oldest sediments are located at the lower levels in the northern part of the Basin.

As the pull-apart basin formed, progressively younger sediments have been deposited from north to south. Because of this type of deposition, the lower units of the pull-apart basin can be heterogeneous.

3.5. FAULTS
The Glen Ivy faultzone separatesthe Bedford area from the Coldwater area, having significant impact on the depth of the basin and thickness of alluvial units. The Coldwater area of the Basin is located within a pull-apart basin between the Glen Ivy fault and the Elsinore Fault Zone located at the base of the Santa Ana Mountains. Within the basin, the Glen Ivy faults truncate and offset the alluvial units by up to 250 feet. This offset is inferred from well logs that extend to bedrock near the fault (Todd and AKM 2008 and WEI 2015b).

The Glen Ivy fault limits deep groundwater flow, resulting in a limitation of the hydraulic connection between the Coldwater and Bedford areas. At depth, the offset geologic units place the alluvial deposits in the Coldwater area against the Tertiary Bedford Canyon Formation. When groundwater levels in the Coldwater area are low, there is reduced groundwater flow across the fault. This is especially apparent during the recent periods when the groundwater levels in the Coldwater area were especially low. During these low water periods in the Coldwater area, groundwater levels are higher across the fault in the Bedford area resulting in minor inflows from Bedford into the Coldwater area. This is shown in some recent groundwater level data and supported by the groundwater modeling (Appendix G).

However, at shallower depths, the fault offset is across alluvial deposits. During periods, or areas, when groundwater levels in the Coldwater area are high, groundwater elevation data suggests these areas appear to be well-connected when groundwater elevations in the Basin are high (Todd and AKM 2008), indicating more compartmentalization with depth. However, there isinsufficient groundwater elevation monitoring information to assess the extent of this potential barrier to flow and it is therefore not considered a complete barrier to groundwater flow in the Basin.

Bedford-Coldwater GSP 3-4

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3.6. PRINCIPAL AQUIFER
The following is a summary of the principal aquifer in the Basin, including the source and character of the sediments, lateral boundaries, and faults that potentially affect groundwater flow through the principal aquifer.

3.6.1. Description of Principal Aquifer
The principal aquifer of the Bedford-Coldwater Basin is composed of alluvium, including alluvial fan, alluvial valley, axial channel, and wash deposits. These deposits are sourced from the Santa Ana Mountains to the west of the Basin and the Peninsular Ranges to the east of the Basin. The Bedford Canyon Formation (a slightly metamorphosed sedimentary formation composed of interlayered argillite, slate, graywacke, conglomeratic graywacke, impure quartzite, and small masses of limestone and quartz-rich metasandstone) and adjacent granitic rocks are the primary source materials for these alluvial deposits. The alluvial fan deposits in the Coldwater area extend into the Bedford area and appear to have been disrupted by faulting (Figure 3-5). Channel deposits along Temescal Wash and local tributaries define the eastern boundary of the Basin. In the northern Bedford area, a variety of Tertiary sedimentary units crop outincluding the Silverado (Paleocene), Vaqueros(Miocene), Topanga (Miocene), and Puente (Miocene) formations (Figure 3-5). The alluvial aquifer materials in this portion of the Basin are sourced from these Tertiary sedimentary units. Assuch, the character of the deposits and the groundwater chemistry differ from the alluvial fans in the Coldwater area and those to the north in the Temescal Subbasin and south in the Elsinore Groundwater Basin.

Both older and recent alluvial fans have been deposited along the mountain front on the western edge of the Basin. These fans have prograded across both the Coldwater and Bedford areas from west to east. Although these deposits are relatively thick, the entire unit is heterogeneous. Sand lenses within the fan deposits collectively form the Alluvial Fan Aquifers.

These aquifers from less than 40 feet up to 500 feet in the Bedford area (eastern portion of the Basin) and up to 800 feet in thickness in the deepest portions of the Coldwater area (western portion of the Basin) (Todd and AKM 2008).

3.6.2. Description of Lateral Boundaries
The bedrock units of the uplands provide distinct lateral boundaries for the basin and its alluvial units. Basin alluvium is thin in some areas, which in itself impedes groundwater flow.

This is especially relevant at the northern and southern boundaries of the Basin.

3.7. DEFINABLE BASIN BOTTOM
The Basin bottom is defined by bedrock, which is shallow around the perimeter and deep in the center. Depth to bedrock ranges in depth from 10 feet to over 700 feet (Todd and AKM 2008 and WEI 2015b). The depth to the bottom of the alluvial materials in the Basin and the contact with the bedrock bottom of the Basin are shown in the contours presented in Figure

Bedford-Coldwater GSP 3-5

TODD GROUNDWATER,
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3-6. Aquifer thickness is greatest in the Coldwater portion of the Basin west of the Glen Ivy fault, as shown in Figures 3-6 and 3-8.

3.8. CROSS SECTIONS
Figure 3-7 is a map showing locations of two cross sections, Figures 3-8 and 3-9. The two hydrogeologic cross sections were constructed to identify hydrogeologic structures affecting groundwater, to characterize the thickness and distribution of aquifer sediments within the Basin, and to confirm aquifer descriptions presented above.

The crosssections and depth to bedrock map were prepared using available information from existing datasets and sources including the following:
• Surficial geology in geographic information system (GIS) coverage format (USGS 2004 and 2006).
• Fault locations and orientations (USGS 2004 and 2006). • Lithologic and well construction logs from local agencies. • Drillers Log files from California Department of Water Resources (DWR). • National Elevation Dataset (NED) ground surface digital elevation model data for Riverside County (USGS 2019).

The two cross sections (Figures 3-8 and 3-9) show the bedrock profile, location of faults, nature and maximum thickness of the alluvial fan aquifers and the relationship with the Temescal Wash deposits. Locations and general construction of wells also are shown. As indicated, alluvialsediments are more than 800 feet thick in the Coldwater area and up to 500 feet thick in the Bedford area, with the thickest section occurring near the Glen Ivy Fault. The crosssections are consistent with and support the conceptual model described above and the depth to bedrock (Figure 3-6).

3.9. STRUCTURES AFFECTING GROUNDWATER
The Basin is defined by the lateral extents of the alluvial material in the pull-apart basin described above. This material is bounded by bedrock in the Santa Ana Mountains on the west and the Peninsular Ranges to the east. The southern and northern boundaries of the Basin are formed by areas of thin alluvial material overshallow bedrock in narrow valleys (Todd and AKM 2008 and WEI 2015b). Within the Basin the groundwater is affected by faulting in the Elsinore Fault Zone, primarily the Glen Ivy fault as described in Section 3.5 above.

3.10. RECHARGE AND DISCHARGE AREAS
Areas of major recharge and discharge are shown in Figure 3-10. Recharge to the Basin occurs primarily from infiltration of runoff, and to a lesser extent from deep percolation of precipitation and urban return flows, wastewater recharge, and subsurface inflow from outside the Basin.

Bedford-Coldwater GSP 3-6

TODD GROUNDWATER,
H&H Water Resources,
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Most of the Basin recharge comes from the infiltration of runoff from precipitation in the Santa Ana Mountains west of the Basin and the Peninsular Ranges east of the Basin. Large amounts of runoff from the mountains flow into unlined channels and the shallow subsurface at the edges of the Basin and then on into and through the Basin. The amount of water available forrecharge varies annually with changesin rainfall and runoff. Runoff into the Basin is subject to evapotranspiration, infiltration, and continued surface flow to and in the Temescal Wash. The watersheds contributing to the Basin include multiple drainages, all of which flow across the Basin in generally east-west orientations. Wet years generate large amounts of water that exceed the recharge capacity of the Basin (Todd and AKM 2008).

Deep percolation of precipitation is the process by which precipitation enters groundwater.

Recharge to groundwater from deep percolation occurs throughout the Basin (Todd and AKM 2008).

Return flows are those portions of applied water (e.g., landscape irrigation) that are not consumed by evapotranspiration and returned to the groundwater system through deep percolation or infiltration. Return flows associated with urban, industrial, and agricultural water uses all have the potential to contribute to recharge to the Basin (Todd and AKM 2008).

Recharge associated with wastewater occurs with discharges from the wastewater treatment facilities within and upstream from the Basin (TVWD water reclamation facility [WRF] and Corona WRF-3, and Horsethief Canyon WRF, respectively; see Figure 4-14 for locations) and from on-site wastewater treatment systems (OWTS). Subsurface inflow occurs along the Basin boundaries both through bedrock inflow along the western and eastern Basin boundaries and from the Elsinore Subbasin to the south, but these are not considered to be a significant source of recharge to the Basin (Todd and AKM 2008).

Discharge from the Basin is almost entirely from groundwater pumping (see well locations on Figure 3-1), evapotranspiration, and mining operations (quarries on Figure 3-10). There is some limited discharge across the northern Basin boundary with the Temescal Subbasin of the Upper Santa Ana River Basin, but the thin alluvial material in this area limits the volume and timing of subsurface outflow along this boundary (Todd and AKM 2008 and Appendix G).

3.11. PRIMARY GROUNDWATER USES
The primary groundwater uses in the Basin are municipal pumping, with limited private pumping for small water system, commercial, and residential users. Groundwater use estimates are included in Section 5, Water Budget.

3.11.1. Bedford Area
Groundwater in the principal aquifer in the Bedford area is primarily used for non-potable municipal and irrigation water supply. There are no known potable water supply wells in the Bedford area.

Bedford-Coldwater GSP 3-7

TODD GROUNDWATER,
H&H Water Resources,
and Stantec

3.11.2. Coldwater Area
The principal aquifer in the Coldwater area is mostly used for municipal water supply. Most of the pumping in this area is from wells owned and operated by the BCGSA agencies, with some additional pumping by small community water system and small commercial users.

Non-potable pumping has occurred historically in this area to support agricultural, recreational, small residential, and industrial water uses.

3.12. DATA GAPS IN THE HYDROGEOLOGIC CONCEPTUAL MODEL
The hydrogeologic conceptual model has not identified data gapsin available information that affect the assessment of sustainability in the Basin.

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Figure 3-2
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Santa Ana
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Figure 3-3
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Soil Hydrologic Group
A: High Infiltration Rate
B: Moderate Infiltration Rate
C: Slow Infiltration Rate
D: Very Slow Infiltration Rate
No Data
Bedford-Coldwater Basin
Source:

Natural Resources Conservation Service (NRCS), 2019,
SSURGO soil survey online map database available at
http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx last accessed September 2019.
("N
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Figure 3-4
Basin Soil
Hydrologic Properties
3-11

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Temescal Canyon Road
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Glen Ivy Fault (Elsinore Fault Zone)
Glen Ivy Fault (Elsinore Fault Zone)
Elsinore Fault Zone
Santa Ana Mountains Qvof
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Qvof1
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Qof
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Kcg
Kvsp
Tp
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Tp
Tt
Trmu
Jbc
Qvof
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Tlm?
Kcto
Qvof
Kcg
Qvoa
Qvof
Tlm
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Kgb
Qya
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Tsi
Qaf
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Trmu
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Trmu
Qaf
Qyf
Qof
Tsi
Trms
Qaf
Qvof
Kcg
Kcg
Qaf
Qof
Qvoa
Kvem
Qaf
Tp
Trmu
Tf
Tsi
Tsi
Qaf
Tf
Qvoa
Qvof
Kcgb
Kcgb
Tlm
Tvs
Tf
Trmu
Qvof
Qaf
Kvsp
Qaf
Tvs
Qof
Qoa
Qvoa
Tsi
Qvof
Kcg
Khg
Tf
Qvof
Qols
Tf
Tsi
Qoa
Qyf
Tsi
Qvof
Qvof
Qaf
Qvoa
Tlm
Tf Qvof
QTn
Qols
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Kcg
Qyf
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Tf Tf
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Kcto Kcto
Qaf
Qyls
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Qols
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Tlm
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Qvof
Tp
Qyf
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Qof
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Tp
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Kcg
Qols
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Tt
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Kcg
Tvs
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Kvem
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Qvof Qvof
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Trmu
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Kvem
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Qyf
Qyf
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Qyf
Qvof
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Tsi
Qof
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Qyv
Qvof1
Kvspi
Trmu
Qvof1
Qvof
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Kvspi
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Qvof1
Tsi
Kvspi
Jbcm
Tsi
Qyf
Kvspi
Qof
Tsi
Qvof
Jbcm
Qyv
Qvof1
Kgt
Tsi
Qvof1
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Qaf
Qyf
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Qvof1
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Khg
Trmu
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Qvof
Kvspi
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Kvem
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Jbc
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Kvspi
Qoa
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Khg
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Ql
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Qya
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Qyls Qyls
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Fault Location, dashed where uncertain
Qaf, Artificial fill
Qw, Very young wash deposits
Qf, Very young alluvial-fan deposits
!
!
!
!! !
!
! !
!
!
!
Ql, Very young lacustrine deposits
! Qyw, Young wash deposits
Qyf/Qyf1, Young alluvial-fan deposits
! ! !
! !
!
!
!
! !
!
! !
!
!
!
! ! !
!
! !
Qya, Young axial-channel deposits
Qyv, Young alluvial-valley deposits
Qyls, Young landslide deposits
Qof, Old alluvial-fan deposits
Qoa, Old axial-channel deposits
Qov, Old alluvial-valley deposits
Qols, Old landslide deposits
Qvof, Very old alluvial-fan deposits
Qvoa, Very old axial-channel deposits
QTt, Conglomerate of Temescal area
!
!
!!
!! !
!
QTn, Sedimentary rocks of Norco area
Tf, Fernando Formation
Tp, Puente Formation
Tlm, Lake Mathews Formation
Tcgr, Rhyolite-clast conglomerate of Lake Mathews area
Tt, Topanga Group
Tvs/Tvss, Vaqueros and Sespe Formations, undifferentiated Tsi, Silverado Formation
Kgg/Kgt/Kgtf/Kgti/Kgh/Kgh/Kght, Gavilan Ring Complex
Katg, Granodiorite of Arroyo del Toro Pluton
Kcto/Kcg/Kcgd/Kct/Kcgq/Kcgb, Cajalco Pluton
Kgu, Granite, undifferentiated
Kgb, Gabbro, undifferentiated
Khg, Heterogeneous granitic rocks
Kvsp/Kvspi, Santiago Peak Volcanics
Kvem/Kvr/Ksv/Kvs, Estelle Mountain volcanics of Herzig
Jbc/Jbcm, Bedford Canyon Formation
Trms/Trmu, Rocks of Menifee Valley
Source:

United States Geological Survey (USGS), 2004,
Preliminary Digital Geologic Map of the Santa Ana 30’ x 60’ Quadrangle, Southern California, Version 2.0 compiled by D.M. Morton, Open-File Report 99-172,
http://pubs.usgs.gov/of/1999/of99-172/
and
United States Geological Survey (USGS), 2006,
Geologic Map of the San Bernardino and Santa Ana 30’ x 60’ Quadrangles, California, Version 1.0 compiled by
Douglas M. Morton and Fred K. Miller, Open-File Report
2006-1217, http://pubs.usgs.gov/of/2006/1217/
(
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Figure 3-5
Surficial Geology
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3-17

Bedford-Coldwater GSP 4-1

TODD GROUNDWATER,
H&H Water Resources,
and Stantec

4. CURRENT AND HISTORICAL GROUNDWATER CONDITIONS
The Sustainable Groundwater Management Act (SGMA) requires definition of various study periods for current, historical, and projected future conditions. Current conditions, by SGMA definition, include those occurring after January 1, 2015 and accordingly, historical conditions occurred before that date. A historical period must include at least 10 years.

The study period 1990 through 2018 is based on the cumulative departure from mean precipitation at Santiago Peak, Lake Elsinore, and Riverside climate monitoring stations. This period is representative and includes droughts and wet years, with an average annual rainfall of 12.97 inches, comparable to the long-term average of 12.9 inches (1875 to 2017).

Accordingly, groundwater conditions over time are described through 2018.

Groundwater conditions are described in terms of the six sustainability indicators identified in SGMA; these include:
• Groundwater elevations.
• Groundwater storage.
• Potential subsidence.
• Groundwater quality.
• Seawater intrusion (which is not likely to occur in this inland basin). • Interconnected surface water and groundwater dependent ecosystems.

4.1. GROUNDWATER ELEVATIONS

4.1.1. Available Data
Groundwater elevation records were collected from multiple sources, including previous investigations, City of Corona, United States Geological Survey (USGS) National Water Information System (NWIS), California Department of Water Resources (DWR), and California Statewide Groundwater Elevations Monitoring (CASGEM). Data from these sources were collected, reviewed, and compiled into a single unified groundwater elevation dataset. The wells with water level measurement records are shown on Figure 4-1.

4.1.2. Groundwater Occurrence
As summarized in Chapter 3, groundwater is present in one principal aquifer. Groundwater in the Bedford-Coldwater Subbasin (Basin) occurs under unconfined conditions and there are no data to suggest distinct vertical zones or to provide zone-specific groundwater elevation hydrographs or maps.

4.1.3. Groundwater Elevations and Trends
Hydrographs showing groundwater elevation trends over time were prepared for all 28 wells with elevation data in the Basin; these hydrographs then were reviewed to identify wells with

Bedford-Coldwater GSP 4-2

TODD GROUNDWATER,
H&H Water Resources,
and Stantec
long term data that could be used to present representative hydrographs. The selection of representative wells was based on a quantitative approach that considered hydrographs with long records characteristic of an area and distribution of wells across the Basin. All available groundwater elevation data were plotted as hydrographs and well locations were plotted on a basin-scale map. All wells with water level data are shown in Figure 4-1. Long term changes in groundwater elevations in the Basin are illustrated in representative hydrographs shown in Figures 4-2 through 4-6 and show conditions since January 1990, where available, thus showing the study period for the Groundwater Sustainability Plan (GSP).

Representative wells with long term hydrographs were selected based the following criteria:
• Location – Wells were prioritized considering broad distribution across the Basin and availability of other wells nearby.
• Ongoing and/or recent monitoring – Wells were selected that are part of the active monitoring network or have recent data.
• Trends – Each hydrograph was assessed for continuity of monitoring, representation of local or regional trends, and presence of outliers or unrealistic data.

The northern hydrograph wells in Figure 4-2 through 4-5 all reflect stable groundwater level conditions. These four wells show a slight decrease during the 2013 through 2015 drought but the net change is only 20 to 30 feet. The southernmost well, Corona 3 on Figure 4-6 shows conditions in the Coldwater area where there is more variation than other areas of the Basin.

Asshown on the hydrograph, water levels have declined over the last 24 years with significant fluctuations in response to wet and dry cycles. Water levels in the Coldwater area have varied more than 350 feet over the last 30 years with multiple major and minor cycles of groundwater elevation decline and recovery, as illustrated on the hydrograph. Some of the short-term fluctuations may have been influenced by incomplete recovery of pumping water levels in the well. The wide water level fluctuations over time in the Coldwater area likely reflect the relatively small footprint and fault-controlled flow along with the fact that most of the pumping in the Basin occurs in this area. Although long-term declines in groundwater elevations have occurred in Coldwater in the past, recent groundwater elevations have stabilized due in part to shared management of the Basin between the three BedfordColdwater Groundwater Sustainability Agency (BCGSA) agencies.

Recent water levels in the Coldwater area are just below 800 feet msl (as shown on Figure 4- 6) and reflect a recovery of approximately 60 feet from the historical low reached in late 2010.

This recovery is due, in part, to a production agreement between the City of Corona (Corona) and Elsinore Valley Municipal Water District (EVMWD) for the Coldwater portion of the Basin, where most of the pumping occurs.

4.1.4. Groundwater Flow
Figures 4-7 and 4-8 are groundwater elevation contour maps constructed to examine current groundwater flow conditions and using data from fall 2015 and spring 2018, respectively.

Contours were developed based on available groundwater elevation data for all wells and information from the numerical groundwater model (Appendix G). The fall 2015 groundwater

Bedford-Coldwater GSP 4-3

TODD GROUNDWATER,
H&H Water Resources,
and Stantec
elevation contours (Figure 4-7) show flow generally from south to north in the Basin and from the northwest to the northeast in the north of the Basin. A slight water table depression occurs in the Coldwater area around the active production wells. Water levels in the Bedford area near the Glen Ivy fault were higher than those across the fault in the Coldwater area, indicating flow from Bedford to Coldwater. The groundwater elevations in this period represent relatively dry conditions at the end of the most recent drought period. Spring 2018 groundwater elevation contours (Figure 4-8) also show flow generally south to north with easterly flow in the north of the Basin and a small depression in the Coldwater area. Spring 2018 followed a period of relatively wet conditions. However, water levels in the Basin were very similar to those during the fall 2015 dry conditions. This includes the depression in the Coldwater area and the indication of flow from Bedford to Coldwater acrossthe Glen Ivy Fault.

Both fall 2015 and spring 2018 contours show that groundwater elevations are relatively consistent.

4.1.5. Vertical Groundwater Gradients
The current monitoring network for groundwater elevations provides little information about vertical head (groundwater elevation) gradients within the Basin. Available data are almost entirely from water supply wells, which are typically screened between 200 and 500 feet below ground surface (bgs). The potentiometric head at the depth of the well screens can be different from the true water table, which is the first zone ofsaturation reached when drilling down from the ground surface.

4.2. CHANGES IN GROUNDWATER STORAGE
Change in storage estimates based on evaluation of groundwater elevation changes and water budget inflow and outflow have completed for the portions of the Basin in past studies (MWH 2004, SAIC 2007, WEI 2015a, 2015b, 2016, 2017b, and 2019). Such storage change estimates are based on available groundwater elevation data that are limited geographically and temporally and thusinclude uncertainty. In addition, the storativity, orstorage coefficient (the volume of water released from storage per unit decline in hydraulic head), is largely unknown across the Basin. The volume of groundwater storage change over time can be calculated by multiplying the groundwater elevation changes during a period by the storage coefficient. Storage coefficient value and storage change estimates for the Basin have been developed through calibration of the numerical model, as described in Appendix G.

Therefore, the numerical model is the best tool for estimating groundwater storage changes.

The resulting change in storage estimates are presented in the Water Budget chapter.

4.3. LAND SUBSIDENCE AND POTENTIAL FOR SUBSIDENCE
Land subsidence is the differential lowering of the ground surface, which can damage structures and facilities. This may be caused by regional tectonism or by declines in groundwater elevations due to pumping. The latter process is relevant to the GSP. While subsidence has not been a known issue in the Basin, groundwater elevation declines in the

Bedford-Coldwater GSP 4-4

TODD GROUNDWATER,
H&H Water Resources,
and Stantec
subsurface, resulting in dewatering and compaction of predominantly fine-grained deposits (such as clay and silt) can cause the overlying ground surface to subside.

This process is illustrated by two conceptual diagrams shown on Figure 4-9. The upper diagram depicts an alluvial groundwater basin with a regional clay layer and numeroussmaller discontinuous clay layers. Groundwater elevation declines associated with pumping cause a decrease in water pressure in the pore space (pore pressure) of the aquifer system. Because the water pressure in the pores helps support the weight of the overlying aquifer, the pore pressure decrease causes more weight of the overlying aquifer to be transferred to the grains within the structure of the sediment layer. If the weight borne by the sediment grains exceeds the structural strength of the sediment layer, then the aquifer system begins to deform. This deformation consists of re-arrangement and compaction of fine-grained units2 , as illustrated
on the lower diagram of Figure 4-9. The tabular nature of the fine-grained sediments allows for preferred alignment and compaction. As the sediments compact, the ground surface can sink, as illustrated by the right-hand column on the lower diagram of Figure 4-9.

Land subsidence due to groundwater withdrawals can be temporary (elastic) or permanent (inelastic). Elastic deformation occurs when sediments compress as pore pressures decrease but expand by an equal amount as pore pressures increase. A decrease in groundwater elevations from groundwater pumping causes a small elastic compaction in both coarse-and fine-grained sediments; however, this compaction recovers as the effective stress returns to its initial value. Because elastic deformation is relatively minor and fully recoverable, it is not considered an impact.

Inelastic deformation occurs when the magnitude of the greatest pressure that has acted on the clay layer since its deposition (preconsolidation stress) is exceeded. This occurs when groundwater elevations in the aquifer reach a historically low groundwater elevation. During inelastic deformation, or compaction, the sediment grains rearrange into a tighter configuration as pore pressures are reduced. This causes the volume of the sediment layer to reduce, which causesthe land surface to subside. Inelastic deformation is permanent because it does not recover as pore pressures increase. Clay particles are often planar in form and more subject to permanent realignment (and inelastic subsidence). In general, coarse-grained deposits (e.g., sand and gravels) have sufficient intergranular strength and do not undergo inelastic deformation within the range of pore pressure changes encountered from groundwater pumping. The volume of compaction is equal to the volume of groundwaterthat is expelled from the pore space, resulting in a loss of storage capacity. This loss of storage capacity is permanent but may not be substantial because clay layers do not typically store significant amounts of usable groundwater. Inelastic compaction, however, may decrease the vertical permeability of the clay resulting in minor changes in vertical flow. 2 Although extraction of groundwater by pumping wells causes a more complex deformation of the aquifer system than discussed herein, the simplistic concept of vertical compaction is often used to illustrate the land subsidence process (LSCE et al. 2014).

Bedford-Coldwater GSP 4-5

TODD GROUNDWATER,
H&H Water Resources,
and Stantec
The following potential impacts can be associated with land subsidence due to groundwater withdrawals (modified from LSCE et al. 2014):
• Damage to infrastructure including foundations, roads, bridges, or pipelines, • Loss of conveyance in canals, streams, or channels,
• Diminished effectiveness of levees,
• Collapsed or damaged well casings, and
• Land fissures.

4.3.1. Interferometric Synthetic Aperture Radar (InSAR) InSAR data are provided by DWR on its SGMA Data Viewer (DWR 2020) and document vertical displacement of the land surface across a broad area of California from June 13, 2015 to September 19, 2019. The accuracy of the InSAR ground surface elevation change estimates is reported to be ±16 millimeters (mm), or ±0.052 feet (ft) (Towill 2020). The TRE Altamira InSAR Dataset, shown on Figure 4-10 shows mapping within the Basin for land surface deformation between 2015 and 2019.

The TRE Altamira InSAR data on Figure 4-10 uses a range of 0.05 to -0.05 ft to display the estimated ground surface elevation change in the Basin. The maximum estimated ground surface elevation rise in the Basin between 2015 and 2019 is 0.02 ft and the maximum decline is -0.05 ft. These estimated changes are lessthan the reported accuracy forInSAR. Thus, based on the InSAR estimates there has effectively been no change in ground surface elevation within the Basin in the 2015 to 2019 period. Given these data and the understanding of the hydrogeological conceptual model, there is no evidence of subsidence at this time.

4.4. GROUNDWATER QUALITY
The natural quality (chemistry) of groundwater is generally controlled by the interaction between rainwater and rocks/soil of the vadose zone and aquifers (Drever 1988). As rainfall infiltrates through the soil column, changes in water chemistry occur as anions and cations are dissolved into the water. These changes are influenced by soil and rock types, weathering, organic matter, and geochemical processes occurring in the subsurface. Once in the groundwater system, changing geochemical environments continue to alter groundwater quality. A long contact time between the water and sediments may allow for more dissolution and more concentrated groundwater (Drever 1988). The natural groundwater quality in a basin is the net result of these complex subsurface processes that have occurred over time.

General mineral quality of groundwater is naturally poor, especially in the Bedford area, as indicated by relatively high concentrations of total dissolved solids and sulfate. This reflects in part the occurrence in the northern Bedford area of Tertiary sedimentary units, in contrast to the alluvial fans of the Coldwater area. The Corona Groundwater Management Plan evaluated the geochemistry of the Basin, and compared the Coldwater area to the Bedford area (Todd and AKM 2008). This evaluation showed the Coldwater area had a relatively high calcium-to-sodium ratio compared to groundwater in the Bedford area and downgradient

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Temescal Basin. This relationship showed a difference in the source material in the aquifer in these two locations. The aquifer material in the Coldwater area is sourced from the granitic units in the Santa Ana Mountains, while the material in the Bedford area is sourced from the Tertiary sedimentary units that outcrop within that area and east of the Basin.

Groundwater quality can vary in the Basin; some areas have good water quality while other areas have high mineral concentrations, generally presenting as elevated total dissolved solids (TDS). High TDS concentration in groundwater can be naturally occurring and also the result of anthropogenic sources such as urban runoff, historical agricultural activities, and treated wastewater discharge. Nitrate was historically elevated in parts of the Basin, but recent concentrations have been relatively low. Natural nitrate levels in groundwater are generally very low, and elevated concentrations are associated with agricultural activities, septic systems, landscape fertilization, and wastewater treatment facility discharges.

Groundwater in the Basin has been impacted by human activities including agricultural, urban, and industrial land uses. State agencies with regulatory oversight for water quality in the Basin include the Santa Ana Regional Water Quality Control Board (RWQCB) and the State Water Resources Control Board (SWRCB) – Division of Drinking Water (DDW).

4.4.1. Monitoring Networks
State Water Board GAMA Program
The State Water Board Groundwater Ambient Monitoring and Assessment (GAMA) Program (SWRCB 2019) is the primary source of groundwater quality data in the Basin. The GAMA program has water quality data from 27 wells. Only six of these wells have recent water quality data (data collected since January 2015).

Division of Drinking Water (DDW)
There are four drinking water systems (Corona, EVMWD, Temescal Valley Water District [TVWD], and Glen Ivy Golf Club), with a total of eight well locationsin the Basin. These stations report water quality data to the DDW. Each system monitors and reports water quality parameters to DDW and is required to participate in the Drinking Water Source Water Assessment Program (DWSAP) to ensure wells are not subject to local contamination.

Other Agencies
The RWQCB regulates one site in the Basin, Villa Park Trucking. Groundwater quality data were collected from one well on site from 1997 to 2007. In addition, DWR monitored 17 wells in the Basin from 1955 to 1988 and the USGS monitored two wells from 2006 to 2011.

Wells with water quality data from all available sources are shown on Figure 4-11.

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4.5. OTHER STUDIES

4.5.1. Salt and Nutrient Management Plan 2017
The RWQCB manages salinity in the Santa Ana River Basin, in part by regulating the discharge and reuse of recycled water. TDS and nitrate concentration limitations for recycled water discharge and reuse are set by the RWQCB based on the Wasteload Allocation for surface watersin the Santa Ana River Watershed and the antidegradation objectives and ambient TDS and nitrate concentrations of the receiving groundwater management zone (GMZs), as defined in the Water Quality Control Plan for the Santa Ana River Basin (Basin Plan). While there were two GMZs in the Basin (Bedford and Coldwater), Bedford was combined into the Upper Temescal Valley GMZ.

Consistent with the 2013 SWRCB Recycled Water Policy, a Salt and Nutrient Management Plan (SNMP) was developed for the Upper Temescal Valley, including the Bedford area, in 2017 (WEI 2017a). The purpose of the SNMP was to identify sources of salts and nutrients (current and future) as context for assessing potential impacts of recycled water projects and to plan for management of salt and nutrient sources to ensure that groundwater is safe for drinking and all other beneficial uses. Beneficial uses of water and respective water quality objectives are defined by the RWQCB in the Basin Plan. The report found that TDS concentrations were highly variable across space and time, ranging from a low of 240 milligrams per liter (mg/L) to a high of 1,500 mg/L, and there was no significant long-term trend of water quality degradation or improvement. Similar to TDS, nitrate concentrations are also highly variable; however, there does appear to be a decrease in concentrations over time, which is probably due to the reduction in irrigated agriculture land uses and hence a reduction in added nitrogen in the form of fertilizers.

The SNMP recommended TDS and nitrate antidegradation objectives for the Upper Temescal Valley GMZ consistent with the 2004 Basin Plan. These proposed objectives for TDS and Nitrate as N are 820 mg/L and 7.9 mg/L, respectively (WEI 2017a). These objectives (pertinent to Bedford area) are lower (stricter) than drinking water standards.

4.6. THREATS TO WATER QUALITY

4.6.1. Regulated Facilities
The RWQCB regulates one site in the Basin, Villa Park Trucking. Groundwater quality data were collected from one well on site from 1997 to 2007, and the site has since been closed.

4.6.2. Septic Systems
Some limited areas of the Basin are not served by municipal sewer and rely on on-site wastewater treatment (OWTS orseptic systems). These representsources ofsalt and nutrient loading to groundwater, as well as potential sources of other contaminants. Riverside County Department of Environmental Health is the permitting agency for septic systems and wells in

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the County. The Riverside County Department of Environmental Health maintains an inventory of septic system installations but does not track which remain active. While it is known how many of these septic systems exist, the number is assumed minimal; most of the BCGSA area is sewered.

4.6.3. Non-point Sources
Nonpoint source (NPS) pollution is defined by the SWRCB as contamination that does not originate from regulated point sources and comesfrom many diffuse sources. NPS could occur when rainfall carries contaminants to surface water ways or percolates contaminants to groundwater. One example relevant to the Basin is loading to groundwater of nitrate from agricultural or landscaping land applications.

4.7. KEY CONSTITUENTS OF CONCERN
TDS and nitrate are the primary indicators for salt and nutrient loading and thus are key constituents of concern (COCs) for Basin management.

TDS data are available for both inflows and outflows from the Basin. There are elevated natural background TDS concentrations in groundwater. In addition, TDS can be an indicator of anthropogenic impacts (e.g., infiltration of urban runoff, agricultural return flows, and wastewater disposal).

Nitrate is the primary form of nitrogen detected in groundwater and natural nitrate levels in groundwater are generally very low. Elevated concentrations of nitrate in groundwater are associated with agricultural activities, septic systems, landscape fertilization, and wastewater treatment facility discharges. The maximum contaminant level (MCL) for nitrate (as nitrogen) is 10 mg/L. Nitrate data are available for Basin inflows and outflows, and as documented in the SNMP (WEI 2017a), elevated nitrate concentrations have been recognized. The SNMP analysis of nitrate loading found that most areas had predicted small increasing trends in nitrate in groundwater. However, no wells exceed the MCL for nitrate.

4.7.1. Key Constituents in Groundwater
TDS and nitrate are the constituents of concern in the Basin. Current average conditions(2010 through 2019)show average recent concentrations of TDS of 674 mg/L and nitrate as nitrogen concentrations of 2.75 mg/L. The values represent the average concentrations of these constituents in all drinking water and ambient groundwater monitoring events between 2010 and 2019; water quality samples from regulated facilities were not included in the analysis.

These average conditions serve as a snapshot and allow a comparison of water quality conditions across the Basin.

4.7.2. Total Dissolved Solids (TDS)
As indicated above, average recent TDS concentrations in the Basin are just below the secondary MCL for drinking water (500 mg/L). Recent maximum TDS concentrations from all

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wells are shown on Figure 4-12. While recent concentrations are generally lower than 500 mg/L several historical water quality analyses from wells had higher concentrations of TDS (e.g., exceeding 500 mg/L). Based on data collected by the BCGSA agencies and Glen Ivy (a small water system) from 2010 through 2019, TDS ranges from 210 milligrams per liter (mg/L) to 1,110 mg/L. The recommended TDS secondary maximum contaminant level (SMCL) for aesthetics is 500 mg/L.

4.7.3. Nitrate as Nitrogen (NO3 as N)
The average recent nitrate as nitrogen concentration (2.75 mg/L) is low relative to the MCL of 10 mg/L. Figure 4-13 shows the maximum nitrate as nitrogen concentrations at each well in the Basin. Several wellsin the northern portion of the Basin show elevated historical nitrate concentration of up to 24.8 mg/L. However, no current nitrate detections exceed the MCL of 10 mg/L for nitrate as nitrogen. Nitrate has multiple and widespread sources including fertilizer application (agricultural and landscaping) and wastewater disposal (both municipal and domestic). Given that these sources are on or near the ground surface, shallow groundwater typically is characterized by higher concentrations than deep groundwater.

4.7.4. Other Constituents
In 2021, the BCGSA performed a round of baseline water quality sampling for the GSP. This sampling was designed to serve as a snapshot of ambient water quality for 48 constituents, including perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). Eight wells were sampled, three in Bedford and two in Coldwater; the results of this sampling event are included in Appendix H. PFOS and PFOA were detectable with maximum concentration of 14 nanograms per liter (ng/L) and 25 ng/L respectively. The PFOS concentration is slightly above the response limit of 10 ng/L parts per trillion (ppt) but the PFOA concentration is below the 40 ng/L for PFOS (SWRCB 2020). The response limit for both PFOS and PFOA are based on a running four quarter average, so are not triggered by one sample.

Available water quality data indicate slightly elevated sulfate concentrations in the Basin.

While historical sulfate concentrations ranged from 4 to 339 mg/L, recent samples collected in 2021 show sulfate concentrations from 110 to 270 mg/L. Concentrations in two Bedford wells were above the SMCL for sulfate of 250 mg/L but all wells were below the primary (health related) MCL of 500 mg/L. Sulfate will continue to be monitored as part of the BCGSA’s monitoring program, it was not selected as a constituent of concern. The causes of elevated sulfate may be anthropogenic or naturally occurring. The anthropogenic sources of sulfate are likely from historical agricultural practices that are similar to nitrate and the natural occurrence due to geologic environment are similar to TDS. Therefore, TDS and nitrate are sufficient proxies for sulfate.

Other constituents that could impact beneficial uses or users, including arsenic, were not detected. While recent water quality data are limited, there is no indication of other constituents of concern. The BCGSA will continue to monitor water supply wells for Title 22 constituents to ensure adequate water quality in the Basin.

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4.7.5. Vertical Variations in Water Quality
Water quality monitoring programs in the Basin do not show a distinct difference of water quality in depth, in part because most of the ambient monitoring wells have long screened intervals or are collected from wells with unknown construction.

4.8. SEAWATER INTRUSION CONDITIONS
The Basin is located approximately 25 miles inland from the Pacific Ocean. Lowest elevations (at the northern boundary of the Basin) are above about 1,000 feet. No risk of seawater intrusion exists in the Basin given its location.

4.9. INTERCONNECTION OF SURFACE WATER AND GROUNDWATER
Interconnection of groundwater and surface water occurs wherever the water table intersectsthe land surface and groundwater dischargesinto a stream channel orspring. These stream reaches gain flow from groundwater and are classified as gaining reaches. Conversely, connection can occur along stream reaches where water percolates from the stream into the groundwater system (losing reaches), provided that the regional water table is close enough to the stream bed elevation that the subsurface materials are fully saturated along the flow path.

Groundwater pumping near interconnected surface waterways or springs can decrease surface flow by increasing the rate of percolation from the stream or intercepting groundwater that would have discharged to the stream or spring. If a gaining stream is the natural discharge point for a groundwater basin, pumping anywhere in the basin can potentially decrease the outflow, particularly over long time periods such as multi-year droughts.

Because of the long dry season that characterizes the Mediterranean climate in Riverside County, vegetation exploits any near-surface water sources, including the water table along perennialstream channels,the wetsoil areas around springs, and areas where the watertable is within the rooting depth of the plants. Plants that draw water directly from the water table are called phreatophytes. They are able to continue growing vigorously during the dry season and typically stand out in summer and fall aerial photographs as patches of vegetation that are denser, taller, and brighter green than the adjacent vegetation.

4.9.1. Stream Flow Measurements
Three USGS streamflow gaging stations provide a general characterization of the stream flow regime in Temescal Wash and its tributaries. Their locations are shown in Figure 4-14, and daily flows during water years 2013 through 2020 are shown in Figure 4-15. Temescal Creek at Corona Lake (USGS 11071900) is located at the outlet of Lee Lake at the upstream end of the Basin. Flow at that location is primarily ephemeral, occurring only during and immediately following rainstorm events. No flow was recorded for three consecutive years during the

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recent drought. However, the gage also records recycled water discharges from Eastern Municipal Water District (EMWD), which historically have often been large enough to flow down Temescal Wash as far as Lee Lake. Those discharges were more common prior to the period of gaged flows but still occur in wet years when EMWD is unable to use or store all of its recycled water.

The gauge on Coldwater Canyon Creek has only been in operation for one year, and it is the only record of flow in any drainage on the eastern slopes of the Santa Ana Mountains. The flow regime includes high peaks during storm events and small but persistent base flow supported by drainage of groundwater from fractured bedrock in the watershed. These small flows rapidly percolate where the creek enters the Basin and do not reach Temescal Wash.

All of the tributary watersheds on the west side of the Basin likely have similar flow regimes.

The gauge above Main Street in Corona experiences many more peak flow events. Most of these additional flow events probably derive from imperviousrunoff in the surrounding urban area. A steady base flow of about 2 cubic feet per second (cfs) is not groundwater discharge, but so-called nuisance water (for example,sprinkler overspray onto paving, or pipe leaks) plus discharge from the wastewater treatment plant upstream of the gauge.

A review of 27 high-resolution aerial photographs (Google Earth 2021) between 1994 and 2020 did not reveal any reaches of Temescal wash that appeared to have groundwater discharge; that is, flowing or ponded reaches in an otherwise dry channel during the dry season. Thus, the reach of Temescal Wash that passes through the Bedford-Coldwater Basin does not appear to gain flow from groundwater seepage into the channel, at least during the dry season. Water levels in wells near the creek further suggest that the water table is usually below the creek bed elevation. Data showing depth to the water table are discussed in the next section.

4.9.2. Depth to Groundwater
Depth to groundwater provides a general indication of locations where gaining streams and riparian vegetation are likely to be present. However, available data are of limited use for this purpose due to insufficient geographic and vertical coverage. Available data are almost entirely from water supply wells, which are typically screened deep in the aquifer. The groundwater elevation (potentiometric head) at the depth of the well screen can be different from the true water table, which is the first zone of saturation reached when drilling down from the ground surface. Because recharge occurs at the land surface and pumping occurs at depth, deep alluvial basins such as this one typically have large downward head gradients within the aquifer system. Thus, water level information from wells can potentially underestimate the locations where the water table is shallow enough to support phreatophytic riparian vegetation.

Creeks and rivers that lose water commonly form a mound in the water table near the creek or river. The height and width of the mound depends on the transmissivity of the shallowest aquifer. As an example, in other basins where this condition is observed, groundwater elevations in a shallow well adjacent to the Arroyo Seco in the Salinas Valley California rose 5 to 10 feet more than groundwater elevations in wells 1,000 feet away when the river started

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flowing (Feeney 1994). A groundwater ridge up to 12 feet high develops beneath Putah Creek in Yolo County California during the flow season, but the width of this ridge was estimated to be only a few hundred feet (Thomasson et al. 1960). These examples suggest that shallow wells within 100 to 200 feet of a stream channel would be needed to confirm the presence of hydraulic connection between surface water and groundwater in the Bedford-Coldwater Basin.

Groundwater does not discharge into streams unlessthe watertable is equal to or higherthan the elevation of the stream bed. In addition, the water table does not provide water to phreatophytic vegetation unless it is at least as high as the base of the root zone. The depth of the root zone is uncertain, partly because the relatively few studies of rooting depth have produced inconsistent results and partly because rooting depth for some riparian species is facultative. Thismeansthatthe plants will grow deeperrootsif the watertable declines. Many species (including cottonwood and willow) germinate on moist soils along the edge of a creek in spring. As the stream surface recedes during the first summer, the seedlings survive if the roots grow at the same rate as the water-level decline. Over a period of years, roots grow deeper as the land surface accretes from sediment deposition and/or the creek channel meanders away from the young tree or shrub.

Available water level data from wells were reviewed to identify parts of the Basin where the water table elevation might possibly be high enough to be reached by phreatophyte roots.

For screening purposes, a depth to water of less than 30 feet in wells was selected as a threshold for identifying possible phreatophyte areas. This depth allows for 10 to 15 feet of root depth, 5 feet of elevation difference between the water level in the well and the overlying true water table, and 15 feet of elevation difference between well heads and the bottoms of nearby creek channels.

A second limitation of available groundwater elevation data is the sparse geographic distribution of wells with measurements. Fortunately, many wells in the Basin with waterlevel data are located along Temescal Wash. Figure 4-16 shows a map of the eleven wells with relatively long-term water-level records. They are clustered into five areas. The only location where the typical spring depth to water was less than 30 feet was at the north end of the Basin, near the Flagler and Corona Non-Potable wells. Hydrographs of water levels in those wells are shown in Figure 4-17. Typical spring depths to water in the five wells in that area ranged from 15 to 27 feet. Slightly farther upstream—at the TVWD wells—typical depths to water were slightly greater than 30 feet. Depth to water increases rapidly to the west of Temescal Wash. At the Corona and Station 71 wells, the typical depth to water was 80 to 200 feet.

In summary, groundwater levels in the Basin appear to be too low to normally maintain a hydraulic connection with the Temescal Wash channel. Therefore, groundwater pumping does not deplete flow in Temescal Wash. Groundwater levels might be high enough to support phreatophytic riparian vegetation with roots extending 10-15 feet below the elevation of the creek bed.

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4.9.3. Riparian Vegetation
Vegetation data provide mixed evidence that the water table near some reaches of Temescal Wash is shallow enough to supply water to phreatophytes. Where tree and shrub roots are able to reach the water table, riparian vegetation is typically denser and greener than along reaches where vegetation is supplied only by residual soil moisture from the preceding wet season. Patches of dense riparian vegetation visible in multiple Google Earth (2021) aerial photographs from 1994-2014 are indicated by a crosshatch pattern in Figure 4-16. However, older and more recent aerial photographs indicate that the vegetation has not been a permanent feature of the landscape. The figure also shows the distribution of vegetation classified as Natural Communities Commonly Associated with Groundwater (NCCAG) by The Nature Conservancy in cooperation with DWR. Based on multiple historical vegetation surveys from the early 2000s, the Nature Conservancy prepared detailed statewide mapping of NCCAG vegetation that is accessible on-line (DWR et al. 2020). The extent of NCCAG vegetation is much greater than the extent of dense riparian vegetation and includes vegetation where the water table is certainly deeper than the root zone (such as near the Corona wells). Thus, some of the vegetation in the NCCAG polygons is probably not relying on groundwater. Furthermore, some of the plant species included in the NCCAG mapping are facultative phreatophytes, which means they will exploit a water table if it is within a reachable depth but otherwise survive on soil moisture (typically with smaller stature and greater spacing between plants). These species include red willow (Salix laevigata), which is the most common species mapped along Temescal Wash.

An additional test for groundwater dependence of riparian vegetation was to compare changes in groundwater elevation with changes in vegetation health during the 2012 to 2015 drought. Vegetation health can be detected by changes in the way the plant canopy absorbs and reflects light. The spectral characteristics of satellite imagery can be processed to obtain two metrics commonly used to characterize vegetation health: the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Moisture Index (NDMI). Both are calculated asratios ofselected visible and infrared light wavelengths. The Nature Conservancy developed a second on-line mapping tool called GDE Pulse that provides annual dry-season averages of NDVI and NDMI for each mapped NCCAG polygon for 1985-2018 to assist with the identification of groundwater dependent ecosystems (GDEs) (TNC 2020). In Figure 4-16, the polygons are color-coded by the change in NDMI from 2012 to 2015, with positive values in increasingly dark shades of green and negative values in increasingly dark shades of red.

Negative values indicate stress due to desiccation. The NDVI patterns were similar to the NDMI patterns.

Inconsistencies are immediately apparent. One would expect all of the polygons to have experienced moisture stress during the drought, but about one-third of them experienced little stress. In some cases, an unstressed polygon adjoins a highly stressed polygon, which would be unlikely if declining groundwaterlevels were the cause of the stress. In spite ofthese inconsistencies, the dominant pattern was a decrease in NDMI. This was notably the case for the red willow patch that occupies roughly the northern third of the Temescal Wash reach in the Basin.

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Further evidence of drought stress can be seen directly in aerial photographs. Figure 4-18 shows Google Earth (2021) photos of a reach adjacent to the golf course located about 1,000 feet upstream of the Corona Non-Potable wells. Photographs of the same location in 2012, 2014 and 2016 are shown. There was little apparent change from 2012 to 2014, but by 2016 many of the trees along the central channel appeared to be dead.

Water levelsin wells with relatively shallow depth to water declined 15 to 25 feet during 2012 to 2015, albeit unevenly in some wells. Thus, the declining NDMI values and substantial vegetation mortality both occurred during the same period that groundwater levels declined.

Notably, most of the water-level decline was between 2014 and 2016, which was the period when most of the vegetation mortality occurred. The correlation between groundwaterlevels and vegetation health does not necessarily prove causality, because other sources of water also became more scarce, including rainfall, irrigation return flow and wastewater discharges to Temescal Wash upstream of the site in the photograph. Rainfall at Elsinore during water years 2013 through 2016 averaged 5.96 inches, or 56 percent of the long-term average. The greater abundance of brown areas on the golf course fairways in 2016 relative to 2014 and 2012 suggest that irrigation had been curtailed due to the drought. The TVWD wastewater treatment plant located two miles upstream of the photo site, at the upstream end of the patch of dense riparian vegetation, normally discharges about 15 acre-feet per month (equivalent to 0.25 cfs) of treated wastewater to Temescal Wash, as shown in Figure 4-19.

Those discharges were discontinued from November 2012 through at least November 2018 except for one three-month period in winter 2015. The normal discharge could supply roughly one-third of the summer evapotranspiration (ET) demand of the entire reach of vegetation between the discharge point and the end of the Basin.

Older historical aerial photographs show that dense riparian vegetation was not always present prior to the 1990s (that is, prior to the Google Earth imagery). Figure 4-20 shows aerial photographs taken in 1967 of a 2-mile reach of Temescal Wash in the northern part of the Bedford-Coldwater Basin. It includes the area shown in Figure 4-18 (green rectangle).

There was almost no dense riparian vegetation anywhere along the Wash in 1967. Two factors probably contributed to the lack of vegetation. First, precipitation had been consistently below average since 1947 (see additional discussion in Chapter 5). Second, groundwater pumping was higher in those days to support irrigation of citrus groves (some of which are visible in the photograph). Pumping from the Bedford area averaged 3,000 acre-feet per year (AFY) during 1947 to 1967 (WEI 2015b) versus 1,800 AFY during 2015 to 2019. Both of these factors probably contributed to low surface flow and low groundwater levels, which together killed any prior dense riparian vegetation or prevented such vegetation from becoming established.

In summary, the extent, density and health of riparian vegetation has been variable historically. Vegetation appears to become denser and lusher when surface flow is more abundant and groundwater levels are consistently shallow, and it dies back during droughts and when groundwater levels are low. At any given time, the extent to which riparian vegetation along some reaches of Temescal Wash is phreatophytic and therefore affected by groundwater levels is unclear. The presence of groundwater elevations that are probably

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within reach of phreatophyte roots, the presence of patches of dense riparian tree canopy, and the co-occurrence of groundwater declines and vegetation stress and mortality within the past decade all suggest that some vegetation is dependent on groundwater. However, other drought-related decreases in water availability could have contributed to the observed impacts on vegetation. Additional information regarding the true water table depth in the riparian zone and a more comprehensive evaluation of rainfall, irrigation, and wastewater discharge time series is needed to confirm the degree of vegetation dependence on groundwater levels.

4.9.4. Wetlands
The NCCAG vegetation mapping tool also includes a wetlands map, which is reproduced here with simplified mapping categories in Figure 4-21. In the Bedford-Coldwater Basin, almost all of the wetland polygons are within the Temescal Wash channel and accounted for in the preceding discussion of riparian vegetation. The wetland categories for those polygons are mostly marsh (palustrine) or riverine and characterized as seasonally flooded. Vegetation along the low-flow channel is classified as permanently or semi-permanently flooded, which a brief inspection of aerial photographs shows is clearly incorrect. A handful of small wetland polygons were mapped in upland areas west of Temescal Wash. Most are high up in the stream canyons where perennial stream flow or shallow groundwater is sustained by small amounts of groundwater inflow from the bedrock tributary areas and not affected by pumping in the main part of the Basin. Several patchestotaling 1.4 acres are midway between the wash and western Basin boundary, where regional groundwater levels are many tens of feet below the ground surface. The seasonal flooding orsaturation thatsupportsthe wetlandtype vegetation almost certainly derives from pooled rainfall runoff or interflow rather than discharge of regional groundwater.

The Western Riverside County Multiple Species Habitat Conservation Plan (MSHCP) was reviewed for additional information regarding plant species that might be affected by groundwater (Western Riverside County Regional Conservation Authority 2020). Two large regions mapped as narrow endemic plants and criteria area species partially overlap the Basin.

However, those categories together contain 16 upland plant species that are unaffected by groundwater.

Therefore, the few small areas mapped as wetlands outside the Temescal Wash channel would not be affected by pumping and groundwater levels.

4.9.4.1. Animals Dependent on Groundwater
Animals that depend on groundwater include fish and other aquatic organisms that rely on groundwater-supported stream flow and amphibious or terrestrial animals that lay their eggs in water. Management of habitat for animals typically focuses on species that are listed as threatened or endangered under the state or federal Endangered Species Acts. That convention is followed here. Flow in Temescal Wash is too ephemeral to support migration of anadromous fish (such as steelhead trout), and the watershed upstream of the Basin does not have stream reaches with perennial cool water suitable for spawning and rearing.

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The MSHCP includes mapped areas that are potential habitat for several animal species. The western edge of a very large habitat area for burrowing owl overlaps the eastern edge of the Basin. However, the owl is an upland species that is not dependent on riparian or wetland vegetation.

The coastal California gnatcatcher is a bird species federally listed as threatened. Critical habitat areas delineated by the U.S. Fish and Wildlife Service that are in or near the Basin are shown in Figure 4-22. The habitat polygons are all in upland areas, but a few of them overlap tributary streams underlain by narrow, shallow alluvial bodies that extend outward from the main Basin area. Groundwater in those tributary creek valleys is sustained by gradual discharge from fractured bedrock in the watershed areas, and there is little or no local groundwater pumping. To the extent that vegetation along the tributary stream valleys provides gnatcatcher habitat, it would be unaffected by pumping in the main Basin area.

In summary, there do not appear to be any listed animal species that would potentially be impacted by groundwater pumping or water levels. More common species that use riparian shrubs and trees along Temescal Wash could potentially be impacted during droughts if lowered groundwater levels cause vegetation die-back or mortality.

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Path: T:\Projects\Bedford Coldwater GSP 80802\GRAPHICS\Figure 4-4 TVWD Well 4 Hydrograph.gpj Figure 4-4
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Path: T:\Projects\Bedford Coldwater GSP 80802\GRAPHICS\Figure 4-5 New Sump Hydrograph.gpj Figure 4-5
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Path: T:\Projects\Bedford Coldwater GSP 80802\GRAPHICS\Figure 4-6 Corona Well 3 Hydrograph.gpj Figure 4-6
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Path: T:\Projects\Bedford Coldwater GSP 80802\GIS\Maps\Figures\GSP Figures\Chapter 4 - GW Conditions\Figure 4-7 Groundwater Elevation Contours April 2015.mxd !(
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Figure 4-7
Groundwater
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Path: T:\Projects\Bedford Coldwater GSP 80802\GIS\Maps\Figures\GSP Figures\Chapter 4 - GW Conditions\Figure 4-8 Groundwater Elevation Contours April 2018.mxd !(
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Groundwater
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Figure 4-9
Concepts of
Land Subsidence
Source: Galloway et al., 1999.

After LSCE et al., 2014.

Area of
Largest Subsidence
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clay interbeds
4-25

Path: T:\Projects\Bedford Coldwater GSP 80802\GIS\Maps\Figures\GSP Figures\Chapter 4 - GW Conditions\Figure 4-10 Basin-Wide Subsidence Estimates from Satellite Measurements.mxd !"a$
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Bedford-Coldwater Basin
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Data Source:

Subsidence estimates from satellite measurements provided by the TRE ALTAMIRA InSAR provided by the California Department of Water Resources.
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4-26

Path: T:\Projects\Bedford Coldwater GSP 80802\GIS\Maps\Figures\GSP Figures\Chapter 4 - GW Conditions\Figure 4-11 Wells with Water Quality Data.mxd !(
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!( Well with Water Quality Data from State Water
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!( Well with Water Quality Data from California
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4-27

Path: T:\Projects\Bedford Coldwater GSP 80802\GIS\Maps\Figures\GSP Figures\Chapter 4 - GW Conditions\Figure 4-12 TDS Concentrations.mxd !(
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Total Dissolved Solids
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4-28

Path: T:\Projects\Bedford Coldwater GSP 80802\GIS\Maps\Figures\GSP Figures\Chapter 4 - GW Conditions\Figure 4-13 NO3 Concentrations.mxd !(
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Figure 4-13
Nitrate as Nitrogen
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4-29

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11072100
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Temescal Creek About Main Street, Corona CA
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Coldwater Canyon Creek near Corona CA
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11071900
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Temescal Creek at Corona Lake near Corona CA
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Path: T:\Projects\Bedford Coldwater GSP 80802\GRAPHICS\Figure 4-15 Local Streamflow 2013 through 2020.gpj Figure 4-15
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4-31

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Path: T:\Projects\Bedford Coldwater GSP 80802\GRAPHICS\Figure 4-17 Hydrographs for Wells with Shallow Depth to Groundwater.gpj Figure 4-17
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4-33

June 2012
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Figure 4-18
Recent Riparian
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Imagery
4-34

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Path: T:\Projects\Bedford Coldwater GSP 80802\GRAPHICS\Figure 4-19 TVWD WW Discharge.gpj Figure 4-19
TVWD Wastewater
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4-35

Path: T:\Projects\Bedford Coldwater GSP 80802\GIS\Maps\Figures\GSP Figures\Chapter 4 - GW Conditions\Figure 4-20 1967 Aerial Photo.mxd Approximate Extent
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Path: T:\Projects\Bedford Coldwater GSP 80802\GIS\Maps\Figures\GSP Figures\Chapter 4 - GW Conditions\Figure 4-21 Wetlands in Basin.mxd !"a$
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Figure 4-22
Coastal California
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4-38

Bedford-Coldwater GSP 5-1

TODD GROUNDWATER,
H&H Water Resources,
and Stantec

5. WATER BUDGET
A water balance (or water budget) is a quantitative tabulation of all inflows, outflows, and storage change of a hydrologic system. The Sustainable Groundwater Management Act (SGMA) requires that water balances be prepared for the groundwater system and surface water system of a basin. If a basin contains multiple management areas, separate balances must be developed for each of them. Furthermore, water budgets must be developed fortime periods representing historical, current, future no project (baseline), and future growth plus climate change (growth plus climate change) conditions.

This chapter presents the basis for selecting the water budget analysis periods, describes the boundaries and general characteristics of three management areas within the BedfordColdwater Subbasin (Basin), describes modeling tools used to estimate some water budget items, and presents the surface water and groundwater budgets.

5.1. WATER BUDGET METHODOLOGY
Annual balances were developed for water years 1990 through 2018, the period simulated by the numerical groundwater model. This interval was selected because it is a long hydrologic period for which important water budget data were available. The model is described in Appendix G and provides estimates for several components of the water balance for which direct measurements are not available: flows between groundwater and surface water bodies, flows to and from adjacent basins, evapotranspiration of riparian vegetation, and storage change. The numerical model allows a dynamic and comprehensive quantification of the water balance wherein all estimated water balance elements are reconciled and are calibrated to groundwater level changes over time. Accordingly, the numerical model is the best tool to quantify those water balance components. It will be updated regularly through the Groundwater Sustainability Plan (GSP) implementation process, providing a better understanding of the surface water-groundwater system and a tool to evaluate future conditions and management actions.

5.2. DRY AND WET PERIODS
Dry and wet periods in historical hydrology can be identified on the basis of individual years or sequences of dry and wet years. GSP Regulations require that each year during the water budget analysis period be assigned a water year type, which is a classification based on the amount of annual precipitation. Figure 5-1 shows annual precipitation at Elsinore (National Oceanic and Atmospheric Administration (NOAA) Station GHCND:USC00042805) for water years 1899 through 2020. Water year types are also indicated and are assigned to five categories corresponding to quintiles of annual precipitation. The categories used here (dry, below normal, normal, above normal and wet) accurately describe the quintiles. These categories differ from the nomenclature commonly used in the Central Valley (critical, dry, below normal, above normal and wet) and elsewhere but do not accurately describe local categories and are based on the Sacramento River Index, which has little relevance to

Bedford-Coldwater GSP 5-2

TODD GROUNDWATER,
H&H Water Resources,
and Stantec
conditionsin the Basin. The quintile divisionsfor precipitation during 1899 to 2020 at the Lake Elsinore station are shown in Table 5-1.

Table 5-1. Water Year Type Classification (Lake Elsinore station) Water Year Type Range as Percent of Mean
Precipitation Range
(inches)
Wet W >139 > 16.5
Above Normal AN 101 to 139 12.0 to 16.5
Normal N 75 to 101 8.9 to 12.0
Below Normal BN 56 to 75 6.6 to 8.9
Dry D <56 < 6.6
Average precipitation for 1899 to 2020 was 11.88 inches per year Individual wet and dry years are not particularly useful for groundwater management in basins where groundwater storage greatly exceeds annual pumping and recharge, which is the case in the Basin. In those basins, multi-year droughts and sequences of wet years are more relevant, because they relate to the amount of operable groundwater storage needed to support sustainable groundwater management. Multi-year wet and dry periods can be identified from a plot of cumulative departure of annual precipitation, which is also shown on Figure 5-1. Wet periods appear as upward-trending segments of the cumulative departure curve, and droughts appear as declining segments. By far the largest climatic deviationsin this record were the sustained wet conditions from 1937 to 1944 and dry conditions from 1946 to 1965. These events pre-dated the most recent 30 years, which is the period that the California Department of Water Resources (DWR) states should be used for determining year types (DWR 2016c). They also pre-date the period simulated by the groundwater model.

However, large wet and dry events like those could recur in the future, and it is prudent to consider climate uncertainty in planning for groundwater sustainability.

5.3. WATER BALANCE ANALYSIS PERIODS
GSP regulations require evaluation of the water balances over historical, current, and future periods. The historical period must include at least 10 years, and the future period must include exactly 50 years. The duration of the current period is not specified, but to be consistent with SGMA concepts it needs to include several years around 2015, which was the implementation date of SGMA. Historical and current analysis periods for the Basin were selected from within the 1990 through 2018 modeling period. Ideally, each period is characterized by average precipitation and relatively constant land and water use.

Urbanization in the Basin has been gradual throughout the 1990 to 2018 period. The historical period is represented by water years 1993 through 2007, and the current period by water

Bedford-Coldwater GSP 5-3

TODD GROUNDWATER,
H&H Water Resources,
and Stantec
years 2010 to 2013. Those periods had 101 percent and 102 percent of the 1899 to 2020 average annual rainfall, respectively.

The future period is intended to represent conditions expected to occur over the next 50 years. The modelsimulation period is only 29 years(1990 to 2018). To obtain a 50-year period, simulations of future conditions used the 1993 through 2017 sequence of rainfall and natural stream flow repeated twice. Average annual precipitation during 1993 to 2017 was 94 percent of the long-term average. For the baseline scenario, no adjustments were made to the hydrologic sequence. Adjustments made to simulate future climate change are described in following sections.

5.4. MANAGEMENT AREAS
As defined in the GSP regulations, a Management Area (MA) is an area within a basin for which the GSP may identify different minimum thresholds, measurable objectives, monitoring, or projects and management actions based on differences in water use sector, water source type, geology, aquifer characteristics, or other factors. The Basin has been divided into two MAs. They are described below and in more detail in Appendix I, and their boundaries are shown in Figure 5-2.

5.4.1. Bedford Management Area
The Bedford MA occupiesroughly the eastern two-thirds of the Basin. It isseparated from the Coldwater MA by the Glen Ivy Fault, which is a partial barrier to groundwater flow. The Bedford MA connects to the Elsinore Subbasin in the south and the Temescal Basin at the north end of the Basin. Some subsurface inflow from the Elsinore Subbasin to the south, and subsurface outflow to the Temescal Basin is also possible. Temescal Wash flows along the length of the Bedford MA. It also exits the north end of the Basin but traverses a bedrock reach before entering the Temescal Basin.

5.4.2. Coldwater Management Area
The Coldwater MA is the part of the Basin west of the Glen Ivy Fault. Because of downward movement on that side of the fault, Basin thickness is much greater than in the Bedford MA.

A large open-pit aggregate mine is located in the southern part of this MA. Several streams enter the Coldwater MA from watersheds on the eastern slopes of the Santa Ana Mountains.

5.5. METHODS OF ANALYSIS
Complete, itemized surface water and groundwater balances were estimated by combining raw data (rainfall, stream flow, municipal pumping, and wastewater percolation from septic tanks and wastewater treatment plant discharge) with values simulated using models3 .
3 Water balance values are shown to nearest acre-foot to retain small items, but entries are probably accurate to only two significant digits.

Bedford-Coldwater GSP 5-4

TODD GROUNDWATER,
H&H Water Resources,
and Stantec
Collectively, the models simulate the entire hydrologic system, but each model or model module focuses on part of the system, as described below. In general, the models were used to estimate flows in the surface water and groundwater balancesthat are difficult to measure directly or that relate to time-dependent groundwater levels. These include surface and subsurface inflows from tributary areas, percolation from stream reaches within the Basin, groundwater discharge to streams, potential subsurface flow from the neighboring subbasin and between MAs, the locations and discharges of pumping wells, consumptive use of groundwater by riparian vegetation, and changes in groundwaterstorage. Descriptions of the inflows and outflows to the surface water and groundwater models are included below in Sections 5.6 and 5.7.

5.5.1. Rainfall-Runoff-Recharge Model
This Fortran-based model developed over a number of years by Todd Groundwater staff simulates hydrologic processes that occur over the entire land surface, including precipitation, interception4
, infiltration, runoff, evapotranspiration, irrigation, effects of impervious surfaces, pipe leaks in urban areas, deep percolation below the root zone, and shallow groundwater flow to streams and deep recharge. The model simulates these processes on a daily time step for 242 “recharge zones” delineated to reflect differences in physical characteristics as well as basin and jurisdictional boundaries. Simulation of watershed areas outside the Basin is included to provide estimates of stream flow and subsurface flow entering the Basin. Daily simulation results were subtotaled to monthly valuesfor input to the groundwater model. Additional details regarding the rainfall-runoff-recharge model can be found in Appendix G and the model code is available on request.

5.5.2. Groundwater Model
The groundwater flow model uses the MODFLOW 2005 code developed by the United States Geological Survey (USGS) that is a public domain open-source software as required by GSP regulation §352.4(f)(3). The model produces linked simulation of surface water and groundwater, as described below. Additional documentation of the model and calibration is provided in Appendix G.

5.5.2.1. Surface Water Module
Stream flow in MODFLOW is simulated using the Streamflow Routing Package (SFR) where a network of stream segments represents the small streams entering the Basin from Temescal Wash and tributary watersheds.

Surface water inflows to Temescal Wash were obtained from a similar groundwater flow model of the Elsinore Subbasin. Smallstream inflows were estimated using the rainfall-runoffrecharge model. Each stream segment is divided into reaches, one per model grid cell traversed by the segment. Flow isrouted down each segment from reach to reach. Along each 4 Interception refers to precipitation that does not reach the soil, but instead falls on (and is intercepted by) plant leaves, branches, and plant litter, and is subject to evaporation loss.

Bedford-Coldwater GSP 5-5

TODD GROUNDWATER,
H&H Water Resources,
and Stantec
reach mass balance is conserved in the stream, including inflow from the upstream reach and tributaries, inflow from local runoff, head-dependent flow across the stream bed to or from groundwater, evapotranspiration losses and outflow to the next downstream reach. Flow across the stream bed is a function of the wetted channel length and width, the bed permeability and the difference in elevation between the stream surface and groundwater at the reach cell. Wetted width and depth of the stream are functions of stream flow.

5.5.2.2. Groundwater Module
The MODFLOW groundwater model is constructed to cover the entire Basin. The model grid size is oriented at 40 degrees west of north (N40W) so that it is oriented consistent with the key hydrologic features including streams and faults. The model grid size uses a uniform 100 feet (ft) horizontal grid spacing to provide sufficient resolution to resolve hydraulic gradients, well drawdown cones, and groundwater-surface water interactions in the Basin.

The Basin extends up a number of narrow tributary stream canyons. These narrow canyons can be problematic to simulate using MODFLOW because they can cause difficult numerical stability issues. To limit these effects, the model grid extends up these canyons until the canyon islessthan 3 grid cells wide, orto the extent where the alluvialsediments are regularly saturated. Areas upstream of these locations have been simulated using boundary conditions to estimate inflows based on groundwater conditions and surface water model results.

The numerical model has been constructed to reflect the hydrogeological conceptual model developed for the GSP. The vertical extent of the Basin is based on the mapped depth to consolidated rock. The elevation of surface features and streambed elevations have been derived from geographic information system (GIS) files developed from the local topography and stream information.

Citrus orchards irrigated with groundwater were common in the Basin in the early 1990s, but except for one small grove in the Coldwater MA those have all been replaced by urban development. The citrus orchards present in the early 1990s were almost all replaced by urban development by 2018. Agricultural irrigation pumping of these orchards was estimated by the rainfall-runoff-recharge model, with pumping assigned to a hypothetical irrigation well at the center of each irrigated recharge zone. This pumping was phased out overtime as urban development occurred. Urban irrigation is supplied by the municipal water system, which uses imported water and local wells. Municipal well extractions are known and are entered directly into the model. All major pumpers in the Basin report their annual production to WMWD, which was the source of data for several non-municipal pumping wells. Pumping at private domestic wells is not reported and is not included in the model. The number of those wells is thought to be small, and their total production is almost certainly negligible in the context of the overall Basin water budget.

Bedford-Coldwater GSP 5-6

TODD GROUNDWATER,
H&H Water Resources,
and Stantec

5.5.3. Simulation of Future Conditions
GSP regulations §354.18(c)(3) require simulation of three future scenarios to determine their effects on water balances, yield, and sustainability indicators. For this scenario, the growth and climate change scenarios were combined, resulting in the following two scenarios:

Baseline. This represents a continuation of existing land and water use patterns, imported water availability, and climate.

Growth Plus Climate Change. This scenario implements anticipated changes in land use and associated water use, such as urban expansion, and anticipated effects of future climate change on local hydrology (rainfall recharge and stream percolation) and on the availability of imported water supplies.

Both the future simulations assume a constant level of development and related water demand in the Basin. Development in the growth plus climate change simulation is not phased in over time. This is the best way to demonstrate whether 2068 land use is sustainable because it allows for assessment of the effects of variations in climactic conditions (wet and dry cycles) on groundwater conditions, avoids subjective decisions about the concurrent timing of droughts and development, and providestime for the full effect of future conditions on groundwater to become apparent.

5.5.3.1. Baseline Scenario
The baseline simulation is a 50-year period, as required by SGMA regulations, with water budget components developed using the criteria and assumptions described below. Initial water levels are simulated water levels for September 2018 from the historical calibration simulation. That year represents relatively recent, non-drought conditions. These simulated water levels are internally consistent throughout the model flow domain and reasonably matched measured water levels at wells with available data (see Appendix G for discussion of model calibration).

Surface water and other inflows came from multiple sources. Monthly inflows in Temescal Wash were obtained from the baseline and growth plus climate change simulations produced by the Elsinore Subbasin groundwater model (Carollo and Todd 2021), which is concurrently being used to develop the GSP for that Subbasin. Small stream and bedrock inflows simulated for 1993 to 2017 of the calibration model period were repeated twice to obtain 50 years of data.

In the baseline scenario, land use remains the same as the current conditions. In the model, land use is represented by 2014 land use mapped by remote sensing methods and obtained from DWR, adjusted for subsequent urbanization identified in Google Earth imagery.

Municipal, commercial, and industrial (M&I) and private pumping were assumed to remain at existing levels. Initial estimates were obtained by calculating average pumping for each calendar month during 2010 through 2018 and applying those averages in every year of the

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future simulation. This approach omits additions to and withdrawals from Coldwater MA storage accounts by the three municipal agencies with wells in that MA. Municipal use of imported water was also assumed to remain at existing levels. From the standpoint of the groundwater budget, total municipal water use was used only to estimate pipe leaks. Use of imported water by the Temescal Valley Water District (TVWD) was obtained from that agency’s 2015 Urban Water Management Plan (RMC and Woodard & Curran 2017), and imported water use in the parts of the City of Corona (Corona) and Elsinore Valley Municipal Water District (EVMWD) service areas within the Basin were assumed to be the same on a per-acre basis for developed areas.

The Baseline scenario also assumes wastewater percolation and recycling continue as they have in recent years. Discharges from the TVWD Water Reclamation Facility (WRF) to Temescal Wash were discontinued in 2013. All of the plant outflow is recycled for irrigation during spring, summer, and fall (assumed April through November), and most or all of it is percolated in ponds at the WRF when irrigation demand is low (December through March).

5.5.3.2. Growth Plus Climate Change Scenario
The growth plus climate change scenario incorporated anticipated effects of climate change, urban development, and associated changes in water and wastewater management. In this scenario, rainfall and reference evapotranspiration (ET0) were adjusted to 2070 conditions using monthly multipliers developed by DWR based on climate modeling studies. The multipliers were applied to historical monthly data for the 1993 to 2017 hydrologic period used in the model. DWR prepared a unique set of multipliers for each foursquare kilometer (km2
) cell of a grid covering the entire state. Nine climate grid cells overlie the Basin and its tributary watershed areas. For each recharge analysis polygon in the rainfall-runoff-recharge model, multipliers from the nearest climate grid cell were used. The climate in 2070 is expected to be drier and warmer than at present.

Figure 5-3 compares average monthly precipitation and ET0 before and after applying the climate change multipliers. Simulations of irrigated turf in the rainfall-runoff-recharge model indicated that the combined effect of the warmer and drier climate will be to increase annual irrigation demand by about 10 percent.

In the growth plus climate change scenario, bedrock inflow and surface inflow from tributary streams along the perimeter of the Basin were re-simulated using the rainfall-runoff-recharge model to reflect the effects of urban development in some of the tributary watersheds and of climate change. Urbanization also increased surface runoff within the Basin, which was routed to small streams and Temescal Wash.

Projected land use in 2068, shown in Figure 5-4, was developed on the basis of population projections, land use designations in the Temescal Canyon Area Plan (Riverside County 2018), assumed urban infill, and topography. A comparison of land use acreage by land use category and management area for 1990, 2018, and 2068 is shown in Table 5-2. Conversion of grassland to residential land use was the dominant change in both management areas and also occurred in tributary watershed areas.

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Total municipal water use in 2068 was estimated to be double the amount in 2018. This estimate is an approximate average of several factors. The Temescal Canyon Area Plan (Riverside County 2018) assigns developed land uses to almost the entire Basin area, and the area of undeveloped lands is presently about equal to the area of developed lands. Thus, the amount of developed land could plausibly double. However, the Area Plan also included estimates of future population that would extrapolate to a 2068 population only 58 percent greater than the current population. Finally, TVWD’s 2015 Urban Water Management Plan (RMC and Woodard & Curran 2017) included projections of future water use out to 2040.

Extrapolating those trends to 2068 indicates water use 1.55 times greater than in 2015.

For the growth plus climate change scenario, average annual groundwater pumping in the Coldwater MA was assumed to equal average historical pumping during 2010 through 2017, with an increase proportional to the estimated amount of irrigation return flow from future increased use of imported water. In the Bedford MA, average annual groundwater pumping was assumed to be equal to 2020 production volumes. Municipal pumping in Coldwater was distributed among wells in proportion to their averages during 2010 to 2017 and in Bedford it was distributed as recorded in 2020. All remaining municipal water use was assumed to be obtained from imported water.

Water pipe leak rates in the EVMWD and City of Corona service areas were assumed to decrease to 5 percent of delivered water from the rates reported in the 2015 Urban Water Management Plans (7.0 percent and 6.6 percent, respectively). The leak rate in the TVWD service area was assumed to continue at the low rate reported in 2015 (2 percent).

Wastewater generation was assumed to double by 2068, in proportion to the increase in total urban water use. Wastewater disposal was assumed to change, however. In recent years more of the outflow from the TVWD WRF has been percolated in ponds than has been recycled for irrigation. This proportion was assumed to reverse, such that all outflow would be recycled for irrigation during April through November and all would be percolated in ponds during November through March. The small discharge from Corona WRF-3 to Temescal Wash at the northern end of the Basin was assumed to be eliminated, consistent with the City of Corona’s plans to decommission that WRF.

In the growth plus climate change scenario, mining operations were assumed to have ended and the mine areasto have been converted to stormwater control facilities with groundwater recharge capacity during high runoff periods.

Table 5-2. Bedford-Coldwater Basin Land Use in 1990, 2018 and 2068 (acres) Bedford MA Coldwater MA Tributary Watersheds
1990 2018 2068 1990 2018 2068 1990 2018 2068
Citrus 1,261 0 0 719 32 32 0 0 0
Grassland 2,403 1,603 413 187 103 33 16,703 16,429 16,174 Shrubs/Trees 368 144 64 173 138 82 13,777 13,693 13,693 Dense riparian 256 159 159 8 27 27 0 0 0
Sparse riparian 303 303 303 0 0 0 0 0 0
Open water 0 0 0 0 0 0 0 0 0
Low-density residential 199 529 485 66 88 88 0 0 0
Residential 179 1,379 2,725 76 405 606 0 94 327
Turf 7 263 326 0 170 226 0 85 107
Commercial 0 30 671 24 33 50 0 0 0
Industrial 232 469 469 0 0 0 0 0 0
Quarry 434 252 252 441 588 588 365 555 555
Vacant 785 1,232 561 38 148 0 0 0 0
Land Use
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5.6. SURFACE WATER BALANCE
This section describes and quantifies the water balance of creeks and rivers that cross the Basin. All significant inflows to and outflows from these surface water bodies are included in the water balance. The surface water balance shares two flows in common with the groundwater balance: 1) percolation from surface water to groundwater and 2) seepage of groundwater into surface water. Each of these is an outflow from one system and an inflow to the other.

Annual surface water balances during 1990 to 2018 were compiled from monthly data for each MA, and average annual water balances were calculated for each of the three analysis periods (1993 to 2007 and 2010 to 2013 for the historical simulation, and 2019 to 2068 for the future simulations). Key features of the surface water balancesfor each management area and analysis period are described below, followed by additional information about the methods used to quantify items in the water balances.

Historical annual surface water balances for the Bedford MA during 1990 to 2018 are shown in Figure 5-5 (upper graph). Average annual surface water budgets for the model, historical, current, and future budget analysis periods are listed in Table 5-3 and detailed surface water budget tables are included in Appendix J. Inflow occurs predominantly in wet years and derives from Temescal Wash, east side tributaries and runoff, and streams entering from the Coldwater MA, in descending order of magnitude. Outflow is almost entirely surface outflow in Temescal Wash to Temescal Basin.

In the baseline simulation, discharges of reclaimed water to Temescal Wash consisted only of the small flowsfrom Corona WRF-3; TVWD WRF discharges had already ceased in 2013. Other inflows to the Bedford MA were close to the magnitudes of those flows during the historical and current periods. In the growth plus climate change scenario, Temescal Wash inflows from the Elsinore Subbasin were slightly larger due urbanization and wastewater discharges in that area. Local tributary inflows were slightly reduced due to the warmer, drier climate. There was little change in net stream percolation and outflow to the Temescal Basin.

Annual surface water balances for the Coldwater MA are also shown in Figure 5-5 (middle graph) and Table 5-3. The only inflow of significance is from tributary streams draining the eastern slopes of the Santa Ana Mountains. Those inflows decreased somewhat under the growth plus climate change scenario because of warmer, drier climatic conditions. Less inflow led to less stream percolation (33 percent lower than historical) and less outflow to the Bedford MA (14 percent lower than historical).

A substantial amount of water is imported into the Basin. It is delivered directly to users and does not flow into streams or lakes. Imports began in 1992, and annual amounts since then are shown in Figure 5-5 (bottom graph). Imported water consists of State Water Project (SWP) water purchased from the Metropolitan Water District of Southern California (Metropolitan) and delivered to TVWD through the Temescal Valley Pipeline.

Table 5‐3. Average Annual Surface Water Budgets
Bedford Management Area Coldwater Management Area
Historical
1993 to 2007
Current
2010 to 2013
Baseline1
2019 to 2068
Growth Plus
Climate Change1
2019 to 2068
Historical
1993 to 2007
Current
2010 to 2013
Baseline1
2019 to 2068
Growth Plus
Climate Change1
2019 to 2068
Inflows
Temescal Wash 13,560 10,761 10,892 12,857 0 0 0 0Tributary inflow  8,201 8,522 7,412 6,477 6,280 6,164 5,278 4,611 Wastewater discharges 712 1,227 60 0 0 0 0 0Groundwater flow into streams 791 1,137 990 1,380 16 2 2 1 Total Inflows 23,264 21,646 19,354 20,714 6,296 6,166 5,279 4,612 Outflows
Stream percolation ‐1,564 ‐2,015 ‐1,661 ‐1,714 4,160 3,216 2,780 2,779 Surface outflows  ‐21,700 ‐19,631 ‐17,693 ‐19,000 2,136 2,950 2,499 1,834 Total Outflows ‐23,264 ‐21,646 ‐19,354 ‐20,714 6,296 6,166 5,279 4,612 1 The 50‐year future baseline simulation uses historical hydrology for 1993 to 2017 two times in succession.

Inflow or Outflow
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5.6.1. Inflows to Surface Water

5.6.1.1. Precipitation and Evaporation
Precipitation and evapotranspiration on the land surface are accounted for in the rainfallrunoff-recharge model. Those processes are not included in the surface water balances, which address only water in stream channels, lakes, and imported water. Precipitation and evaporation on the surface of creeks and rivers are invariably miniscule percentages of total stream flow and are not included in the water budget.

5.6.1.2. Tributary Inflows
Tributary inflows to the Basin are from Temescal Wash and tributary watersheds along the east and west sides of the Basin. Temescal Wash inflows were obtained from the Elsinore Subbasin groundwater model. Surface inflowsfrom nine Santa Ana Mountain watershedsthat discharge to the Coldwater MA were estimated using the rainfall-runoff-recharge model, with daily flows subtotaled to monthly flows for input to the groundwater model. Inflows from six eastside tributary watersheds that discharge to the Bedford MA were similarly simulated.

5.6.1.3. Valley Floor Runoff
The rainfall-runoff-recharge model simulates runoff from valley floor areas, which include impervious surfaces in urban areas. Runoff from valley floor areas was added to flows in tributary streams or Temescal Wash at several locations.

5.6.1.4. Wastewater Discharges
Reclaimed water was discharged from TVWD WRF to Temescal Wash beginning around 1991 and gradually increasing to about 2 cubic feet persecond (cfs) during 2008 to 2012. Discharges ceased after that as TVWD increased its capacity to percolate the water in winter and recycle it for irrigation in summer. The City of Corona’s WRF-3 discharges small amounts of reclaimed water to Temescal Wash near the downstream end of the Basin, averaging about 0.2 cfs but increasing to as much as 0.6 cfs in some winters. The City plans to decommission this plant and route its inflow to WRF-1 in the Temescal Basin in Corona.

5.6.1.5. Groundwater Discharge to Streams
Groundwater discharges into streams when the adjacent water table is higher than the stream bed or the water level in the stream. This occurs sometimes along Temescal Wash in the Bedford MA. Because groundwater levels fluctuate over time, estimates of these discharges were obtained from the groundwater model.

5.6.2. Outflows of Surface Water

5.6.2.1. Net Evaporation
Evaporation from streams is almost always a negligible fraction of total flow and is not explicitly itemized in the water budgets or simulated in the model.

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5.6.2.2. Surface Water Percolation to Groundwater
In wet years, percolation from streams along the reaches between the Basin boundary and Temescal Wash is a significant outflow of surface water. Along Temescal Wash in the Bedford MA, the Wash gains flow from groundwater in some reaches and loses it to groundwater in others, depending on the relationship between the stream surface and adjacent groundwater table. These exchanges vary in time as well as location, but over the long run they are of generally similar magnitudes. Because of this dynamic interaction between surface water and groundwater, estimates of flows across the bed of Temescal Wash were obtained from the groundwater model.

5.6.2.3. Surface Outflow from Management Areas and the Basin Surface outflow from the Coldwater MA to the Bedford MA was calculated by subtracting net percolation losses along the tributary streams from their inflows at the Basin boundary. The net losses were simulated by the groundwater model. Surface outflow in Temescal Wash to the Temescal Basin was calculated asthe residual in the surface water balance forthe Bedford MA.

5.7. GROUNDWATER BALANCE
Annual groundwater inflows and outflows for each management area for the 1990 to 2018 model simulation period are shown as stacked bars in Figure 5-6. Inflows are stacked in the positive (upward) direction and outflows are stacked in the negative (downward) direction. A similarstacked-bar chart for the baseline simulation isshown in Figure 5-7 and for the growth plus climate change simulation in Figure 5-8. Average annual groundwater budgets for each MA and budget analysis period are listed in Table 5-4 and detailed groundwater budget tables are included in Appendix J. Highlights of the water budgets are described below, followed by additional information on methods used to quantify each budget item.

In the Bedford MA, the major inflow is percolation from streams especially during wet years.

In recent years (2012 to 2018), reclaimed water percolation has become another major inflow. The major outflows include M&I pumping and groundwater discharge to streams.

Historically, agricultural pumping also has contributed to outflow from the basin but decreased to a negligible amount by 2007.

Percolation from streams—principally Temescal Wash—was similar across all analysis periods. This was because Temescal Wash inflows increased under the growth plus climate change scenario, offsetting decreased inflow from local tributary streams. Meanwhile, total pumping increased by 71 percent from the historical to the growth plus climate change scenario, which resulted in a slight increase in induced percolation from the Wash. The small increase in bedrock inflow under the growth plus climate change scenario was because urbanization of parts of the tributary watersheds produced enough additional recharge to more than offset the effects of climate change. Subsurface inflow progressively decreased and subsurface outflow increased from the historical period to the growth plus climate change scenario. This was caused by declining water levels in the Coldwater MA, which

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reversed the direction of flow across the boundary between the MAs around the end of the historical period. Recharge from pipe leaksroughly doubled due to urbanization but remained a small fraction of total inflows (five percent) because of TVWD’s low reported pipe leak rate.

Overall in the Bedford MA, both future scenarios show increases in reclaimed water percolation.

Outflows in both scenarios also increased. The net result is a slightly decreased change in storage over the historical period, but the basin is still expected to have a positive change in storage (more inflow than outflow) under future conditions, even under growth and climate change projections.

In the Coldwater MA, percolation from streams occurs as infrequent, episodic events. As shown in Figure 5-6, percolation can range from 15,000 acre-feet (AF) in wet years to no stream percolation in dry years. M&I pumping has dominated basin outflows although it has decreased from its peak in the late 1990s. Similar to the Bedford MA, agricultural pumping was an outflow historically but decreased to negligible by 2001.

The differences between the historical, current, and future scenarios stem mostly from the years selected for inclusion in the averaging. Bedrock inflow decreased slightly in the growth plus climate change scenario because of the warmer, drier climatic conditions. The increase in dispersed recharge on both irrigated and non-irrigated lands under the growth plus climate change resulted from urbanization. A fraction of runoff from impervious surfaces is assumed to flow to adjacent pervious soils, creating localized concentrated recharge. This was included in the recharge for non-irrigated lands. As in the Coldwater MA, pipe leaks increased due to urbanization but remained only four percent of total inflows.

Overall in the Coldwater MA, in both future scenarios inflows significantly increase from dispersed rechange over non-irrigated land. Outflows are expected to decline as M&I pumping is projected to be limited in the future based on agreements between the GSA agencies. The combined increased inflow and decreased outflow results in significantly increased storage in future conditions, which reverses the historical water level declines in the Coldwater MA.

Table 5-4. Average Annual Groundwater Budgets
Bedford Management Area Coldwater Management Area
Historical
1993 to 2007
Current
2010 to 2013
Historical
1993 to 2017
Baseline1
2019 to 2068
Growth Plus
Climate
Change1
2019 to 2068
Historical
1993 to 2007
Current
2010 to 2013
Historical
1993 to 2017
Baseline1
2019 to 2068
Growth Plus
Climate
Change1
2019 to 2068
Groundwater Inflow
Subsurface inflow 480 103 353 102 93 10 90 41 34 48
Percolation from streams 1,564 2,015 1,516 1,661 1,714 4,160 3,216 3,327 2,780 2,779 Bedrock inflow 867 816 819 776 828 583 526 536 467 435
Dispersed recharge: non-irrigated land 776 1,040 740 929 1,031 327 487 330 1,164 1,575 Dispersed recharge: irrigated land 792 578 674 559 940 468 336 396 289 396 Pipe leaks 126 156 143 33 92 30 39 35 17 32
Reclaimed water percolation 391 587 638 1,868 2,161 0 0 0 0 0 Quarry recharge 85 21 92 162 471 0 0 0 0 0
Total Inflow 5,080 5,315 4,974 6,090 7,331 5,579 4,694 4,665 4,751 5,264 Groundwater Outflow
Subsurface outflow -179 -370 -205 -498 -423 -92 0 -55 -15 -7 Wells - M&I and domestic -1,235 -577 -1,110 -1,315 -1,895 -5,802 -2,969 -4,787 -3,002 -3,072 Wells - agricultural -728 -65 -460 0 0 -929 -186 -623 -40 -88 Groundwater discharge to streams -791 -1,137 -786 -990 -1,380 -16 -2 -10 -2 -1 Riparian evapotranspiration -482 -732 -512 -760 -1,015 -285 -234 -281 -154 -168 Quarry Operations / Losses -1,447 -1,845 -1,663 -2,422 -2,466 -606 -595 -653 0 0 Total Outflow -4,863 -4,726 -4,737 -5,986 -7,179 -7,730 -3,986 -6,410 -3,212 -3,337 Net Change in Storage
Inflows minus outflows 217 589 237 104 152 -2,152 708 -1,744 1,539 1,927 1 : The 50-year future simulation uses historical hydrology for 1993 to 2017 two times in succession.

Water Balance Items
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5.7.1. Inflows to Groundwater
Inflows to the groundwater flow system in both MAs are dominated by rainfall recharge and stream percolation, which vary widely from year to year depending on hydrologic conditions.

Variations in bedrock inflow from tributary watersheds is steadier because flow through fractured bedrock in those watersheds attenuatesthe recharge pulsesthat occurin wet years.

Urban sources ofrecharge including irrigation return flow and pipe leaks are less variable from year to year but gradually increased during the simulation period in parallel with urban growth.

5.7.1.1. Dispersed Recharge from Rainfall and Irrigation Dispersed recharge from rainfall and applied irrigation water is estimated by the rainfallrunoff-recharge model. The model simulates soil moisture storage in the root zone, with inflows from rainfall infiltration and irrigation, and outflows to evapotranspiration and deep percolation. Simulation is on a daily basis. In recharge zones with irrigated crops—which includes urban landscaping and agricultural irrigation (citrus)—irrigation is assumed to be applied when soil moisture falls below a certain threshold. When soil moisture exceeds the rootzone storage capacity,the excess becomes deep percolation. Rainfall and irrigation water comingle in the root zone and in deep percolation. For the purposes of displaying an itemized water balance, the amount of deep percolation derived from irrigation is estimated as a percentage of the simulated irrigation quantity, and the remainder of the dispersed recharge is attributed to rainfall. Deep percolation of applied irrigation water (irrigation return flow) is generally similar from year to year, whereas rainfall percolation varies significantly on an annual basis. Because urban landscape irrigation increased while agricultural irrigation decreased during the simulation period, total recharge on irrigated lands decreased only slightly. Water pipe leaks were estimated as the percentage of unaccounted for water listed in the 2015 Urban Water Management Plan (eight percent of delivered water, RMC and Woodard & Curran), distributed uniformly over areas of urban land use. Sewer pipes convey only water used indoors, and their leak rate was assumed to be half of the leak rate for water pipes. The one-dimensional dispersed recharge rates are multiplied by the surface area of each recharge zone to obtain volumetric flow rates, and those are subtotaled by management area.

Figure 5-9 shows a map of average annual dispersed recharge during 1993 to 2007. Although this period does not reflect the most current land use, it is a relatively long averaging period that includes a wide range of year types. Most dispersed recharge occurs during relatively wet years. Average annual recharge rates ranged from less than 0.4 to slightly over 13 inches per year (in/yr). Within the Basin, land use had the largest effect on recharge, with residential land uses having relatively high rates because of landscape irrigation, pipe leaks and percolation of a fraction of the runoff from impervious areas. In tributary watershed areas, partitioning of deep percolation beneath the root zone into stream base flow versus groundwater recharge had a strong influence on simulated recharge. In watersheds on the eastside of the Basin, a higher percentage of deep percolation was assigned to base flow than in watersheds on the west side of the Basin in order to better match observed stream flows.

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5.7.1.2. Percolation from Streams
Inflowsto the stream network in the surface water module of the groundwater model include a combination of gauged flows, and simulated runoff from tributary watersheds and valley floor areas obtained from the rainfall-runoff-recharge model.

The surface water module of the groundwater model simulates percolation reach by reach along each stream that crosses the basin, including Temescal Wash and small streams emanating from 15 watersheds around the periphery of the Basin. Percolation is affected by groundwater levels where the water table is equal to or higher than the elevation of the stream bed. This is sometimes the case along Temescal Wash, but the small tributary streams are mostly high above the water table elevation except up in the canyons where they first enter the Basin.

5.7.1.3. Reclaimed Water Percolation
Reclaimed wastewateris percolated in ponds at the TVWD WRF and the City of Corona’s WRF3. However, most of the reclaimed water is recycled for irrigation. Annual or monthly data describing the partitioning of reclaimed water into irrigation, pond percolation and discharge to Temescal Wash were obtained from TVWD and the City of Corona.

5.7.1.4. Subsurface Groundwater Inflow
Subsurface inflow from an adjacent MA or a neighboring basin is simulated by the groundwater model based on water level gradients and subsurface permeability along the boundary segments. In the Coldwater MA, the only such boundary is the Glen Ivy Fault, and flow across that boundary is almost entirely outward to the Bedford MA. In addition to the Glen Ivy Fault, the Bedford MA receives a small among of subsurface inflow from the Elsinore Subbasin and generates a small amount of outflow to the Temescal Basin. Small amounts of subsurface inflow to both MAs also occurs where they abut upland tributary watersheds.

Recharge in those watersheds flows toward the Basin through fractures in bedrock. This process is simulated by the rainfall-runoff-recharge model.

5.7.1.5.Quarry Recharge
Quarry recharge represents inflows of surface water into existing quarries where it is allowed to recharge into the groundwater. In the Coldwater MA, streamflow from Mayhew Creek and some other smaller streams is directed into existing quarry areas where the water is contained and allowed to percolate. Coldwater Creek has been redirected around an existing quarry. Although Coldwater Creek is not currently directed into a quarry, there have been historic instances where flood flows have gone into the quarries, especially prior to 2005. A portion of the estimated streamflow from the rainfall-runoff-recharge model for each stream is recharged to groundwater at the quarry location.

Similarly, in the Bedford MA, streamflow from Brown and McBride Creeks flows into the Mobile Sand quarry located just north of the TVWD WRF. In addition, streamflow from Temescal Wash can flow into the quarry location especially during high and flood flows. The quarry pit at this location is below the water table and is consistently flooded. To estimate

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the recharge, the MODFLOW model applies a boundary condition based on the observed water level in the pit to estimate the volume of quarry recharge.

5.7.2. Outflows from Groundwater
Major outflows from the Basin are groundwater pumping (municipal, industrial, agricultural, and domestic), groundwater discharge into streams, and evapotranspiration by riparian vegetation.

5.7.2.1. Pumping by Wells
Pumping from M&I wells has been measured and recorded for many years by TVWD and Western. Those data are used in the groundwater model. Total pumping for both MAs was about 11,000 (acre feet per year) AFY in the 1990s and decreased to around 3,000 AFY by 2018. This trend was caused by the replacement of groundwater-supplied citrus orchards to urban land usessupplied almost entirely by imported water. In the Bedford MA, TVWD pumps groundwater to supplement recycled water used for irrigation. In the Coldwater MA, groundwater is pumped and exported for municipal use in the Elsinore Subbasin and Temescal Basin by EVMWD and the City of Corona. Pumping is expected to remain around current volumes in the Coldwater MA, consistent with the existing agreement between Corona and EVMWD. However, pumping in the Bedford MA is expected to increase to accommodate future TVWD non-potable water demands.

5.7.2.2. Subsurface Outflow
Subsurface outflows to other MAs or external basins were calculated with the groundwater model by the same methods used to simulate subsurface inflows. The two outflow boundaries are from the Coldwater MA to the Bedford MA and from the Bedford MA to the Temescal Basin. Both of those flows are minor components of the water budget (one to four percent of total outflows).

5.7.2.3. Groundwater Discharge to Streams
Discharges from the Basin to surface water bodies are simulated by the groundwater model based on streambed wetted area, permeability, and on the amount by which the simulated groundwater elevation in a model stream cell is higher than the simulated surface water elevation. This probably occurs at times along Temescal Wash, although dry-season Google Earth aerial photographs rarely show open water in the channel. The groundwater model simulated groundwater discharge to Temescal Wash that averaged 16 percent of total outflow from the Bedford MA during 1993 to 2007.

5.7.2.4. Riparian Evapotranspiration
Evapotranspiration of groundwater by phreatophytic riparian vegetation is influenced by available soil moisture and by depth to the water table. Like other types of vegetation, phreatophytes use soil moisture supplied by rainfall when it is available. Any remaining evapotranspiration demand is met by drawing water from the water table. Phreatophyte use of groundwater is assumed to decrease from the maximum rate when the water table is at

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the land surface to zero when the water table is 20 feet or more below the ground surface.

These calculations are applied at all model cells, but non-zero amounts only occur where the depth to water is commonly less than 20 feet. Aerial photographs indicate a correlation between those areas and the presence of dense, lush riparian vegetation.

Riparian evapotranspiration (ET) was a relatively minor component of groundwater outflow in both MAs—averaging four percent of total outflowsfrom the Coldwater MA and 10 percent of total outflows from the Bedford MA.

5.7.2.5.Quarry Operations and Losses
Quarry outflows represents outflows associated with active or passive quarry operations to account for observed water conditions within the deeper quarry pits. In the Coldwater MA, excavations continued within the large quarry pits following periods of high groundwater levels for the period from 1990 to 2010. During model calibration, it was necessary to assume that additional pumping or other groundwater removal occurred during these operational periods to maintain the observed groundwater levels. Since 2010, it is our understanding that no additional pumping to maintain quarry water levels at the elevations necessary for deepening pits has occurred, which is supported by the historical model calibration.

In the Bedford MA, the rim of the Mobile Sand quarry located just north of the TVWD WRF is low enough to allow surface flow between the pit and Temescal Wash when water levels in the pit or Wash are high. To estimate these flows, the groundwater model applies a boundary condition based on the observed water levels in the pit and Wash to estimate the volume of into or out of the pit. This is a head-dependent boundary condition that is able to calculate either quarry recharge or outflow based on groundwater conditions.

5.8. CHANGE IN GROUNDWATER STORAGE
Figure 5-10 showsthe cumulative change in storage from the model for the two Management Areas during 1990 through 2068. The baseline and growth plus climate change scenario results for 2019 to 2068 are displayed as continuations of the historical storage changes from 1990 to 2018.

As shown, groundwater storage in the Bedford MA increased slightly during 1990 to 2018, presumably as a result of the decrease in total groundwater pumping. Consistent with total simulated inflows and outflows, the storage trend during 2019 to 2068 was level to slightly increasing for both future scenarios. Storage was slightly higher during droughts under the growth plus climate change scenario relative to the future baseline scenario. This is because urban recharge continues during droughts. High recharge in wet yearstended to resetstorage for both scenarios to a similar elevation that is partly limited by interaction with Temescal Wash.

Simulated historical storage in the Coldwater MA declined by a cumulative total of 60,000 AF from 1990 to 2004. EVMWD and Corona entered into an agreement to limit pumping in the MA to safe or sustainable yield in 2008 (Corona and EVMWD 2008). As a result, there was

Bedford-Coldwater GSP 5-20

TODD GROUNDWATER,
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little additional cumulative decline from 2005 to 2018. As a result of decreased pumping, storage under both future scenarios increased steadily from 2019 to 2068. Inflows exceeded outflows in the water budget because of increased urban recharge and continued limitation of pumping. The rate of storage increase was slightly higher under the growth plus climate change scenario relative to the baseline scenario, which can be attributed to increased urban return flow recharge.

5.9. ESTIMATE OF SUSTAINABLE YIELD
The sustainable yield is defined as the volume of pumping that the Basin can sustain without causing undesirable effects. It is not a fixed orinherent natural characteristic of a groundwater basin. Rather, it is influenced by land use activities, importation of water, wastewater and stormwater management methods, potential recharge with recycled water, and the locations of wells with respect to interconnected streams. The estimates ofsustainable yield presented in this section reflect the current status of those variables under the historical and future scenarios and evaluates whether there would be a long-term increase or decrease in basin storage if those conditions continued over a 50-year future period.

A long analysis period is needed to evaluate yield because of the episodic nature of natural recharge. Whereas pumping, irrigation return flow, and pipe leaks are fairly constant from year to year, recharge from precipitation and streams varies widely. Because of evolving land use during 1990 to 2018, no subset of years is ideal for estimating sustainable yield. For the purposes of this GSP historical sustainable yield was calculated based on 1993 to 2017, which is representative of long-term average conditions in terms of precipitation and stream flow.

Sustainable yield was estimated for each management area forthe historicalsimulation (using 1993 to 2017) and the two future simulations (both using all 50 years of the simulation). A simple estimate of sustainable yield can be obtained by adding average annual pumping to average annual change in storage, as shown in Table 5-5.

Table 5-5. Estimated Sustainable Yield
Management Area
Sustainable Yield (acre-feet per year)
Historical
1993 to 20171
Baseline
2019 to 20682
Growth Plus
Climate Change
2019 to 20682
Bedford 1,808 1,419 2,047
Coldwater 4,319 4,581 5,088
Total 6,127 6,000 7,134
1 For the historical sustainable yield estimate, average annual water budgets during 1993 to 2017 were used. 2 The 50-year future simulation uses historical hydrology for 1993 to 2017 two times in succession.

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TODD GROUNDWATER,
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The baseline simulation generally produces a better estimate ofsustainable yield for planning purposes because it incorporates existing land and water use patterns and a long averaging period that more completely captures climatic and conjunctive use cycles. The sustainable yield under baseline conditions was estimated by the same method used for the historical budget analysis period:simulated average annualstorage change over the 50-year simulation was added to average annual pumping for each MA.

This method of estimating sustainable yield ignores head-dependent responses to pumping in the water budget. In other words, storage change is not the only variable that responds to an increase in pumping. In reality, the response is spread out among storage change, subsurface inflow, subsurface outflow, percolation from streams and groundwater seepage into streams. If those head-dependent boundaries are major parts of the flow system, then an increase in pumping will result in an increase in the estimate of sustainable yield. This boundary interaction effect was not revealed in the Coldwater MA because head-dependent boundary flows there are relatively minor. However, the simulations in the Bedford MA show some variability in sustainable yield as a result of variable pumping in the simulations. The sustainable yield estimates for the Bedford MA understate sustainable yield because of the high degree of interconnection between groundwater and surface water in Temescal Wash.

Additional pumping increases net percolation from the Wash at times when the Wash is flowing. This increase in recharge approximately balances increased pumping, thereby preventing a long-term decrease in storage. This situation results in higher estimates of sustainable yield, as shown in the Bedford MA growth plus climate change sustainable yield in Table 5-5.

The estimates of sustainable yield presented here for the two management areas differ from previous estimates that had different objectives. A previous study of groundwater development potential for the Bedford MA quantified many aspects of the water budget but did not explicitly state an estimated sustainable yield (WEI 2015b). It was asserted that a yield estimate based on historical data would not be representative of future conditions and that future pumping and recharge could strongly affect net percolation from Temescal Wash and therefore also the calculated sustainable yield. The study also did not discuss recharge and pumping related to mining activities, which current modeling shows are important components of the water budget. However, the study recommended that total pumping of no more than 2,000 AFY be implemented in conjunction with water-level monitoring to track the associated long-term changes in storage.

For the Coldwater MA, an estimated yield of 3,300 AFY was the basis of a 2008 agreement between City of Corona and EVMWD regarding sharing of yield (Corona and EVMWD 2008).

This is roughly consistent with pumping and storage change in the current period water budget (Table 5-4), but it is smaller than the yield estimates calculated here for the baseline and growth plus climate change scenarios.

The sustainable yield estimates presented here are the result of a comprehensive review of the historical and future water budget components throughout the Basin. The higher future yield values are the result of increased urban recharge as development progresses in the Basin, as required for SGMA.

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TODD GROUNDWATER,
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Sustainable yields calculated from the future scenarios are based on projections far into the future. Slight imbalances in estimated water budgets can result in large cumulative changes in storage, and hence in the calculated yields. By the same token, the long planning horizon provides ample time to adjust water management (recharge and pumping) to maintain basin operation within the sustainable yield if long-term rising or falling trends in cumulative storage in fact occur. In the context of this GSP, sustainable yield estimated from the water budget is contingent on the absence of undesirable results related to water levels, storage, subsidence, water quality, or depletion of interconnected surface water. Quantitative sustainability criteria are presented in Section 6 that define thresholds at which groundwater conditions become undesirable for each of those sustainability indicators. For example, if pumping at the above estimates ofsustainable yield caused subsidence or significant impacts on riparian or aquatic habitats, the yield may need to be reduced to avoid those impacts.

Accordingly, this sustainable yield value is a broad indicator. It indicates no overdraft based on the water budget, but it must be interpreted through evaluation of undesirable results.

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Bedford-Coldwater GSP 6-1

TODD GROUNDWATER,
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6. SUSTAINABLE MANAGEMENT CRITERIA
The Sustainable Groundwater Management Act (SGMA) defines sustainable management as the use and management of groundwaterin a mannerthat can be maintained without causing undesirable results, which are defined as significant and unreasonable effects caused by groundwater conditions occurring throughout the Bedford-Coldwater Subbasin (Basin), which include:
• Chronic lowering of groundwater levels indicating a significant and unreasonable depletion of supply.
• Significant and unreasonable reduction of groundwater storage. • Significant and unreasonable seawater intrusion.
• Significant and unreasonable land subsidence that substantially interferes with surface land uses.
• Significant and unreasonable degraded water quality, including the migration of contaminant plumes that impair water supplies.
• Depletions of interconnected surface water that have significant and unreasonable adverse impacts on beneficial uses of the surface water.

For these sustainability indicators5
, a Groundwater Sustainability Plan (GSP) must develop
quantitative sustainability criteria that allow the Groundwater Sustainability Agency (GSA) to define, measure, and track sustainable management. These criteria include the following:
• Undesirable Result – significant and unreasonable conditions for any of the six sustainability indicators.
• Minimum Threshold (MT6
) – numeric value used to define undesirable results for each sustainability indicator.
• Measurable Objective (MO) – specific, quantifiable goal to track the performance of sustainable management.

Together, these sustainability criteria provide a framework to define sustainable management and delineate between favorable and unfavorable groundwater conditions. This framework also supports quantitative tracking that identifies problems promptly, allows assessment of management actions, and demonstrates progress in achieving the goal of sustainability.
5 If one or more undesirable results can be demonstrated as not present and not likely to occur, a GSA is not required to establish the respective sustainability criteria per GSP Regulations §354.26(d); in the inland Bedford-Coldwater Basin (Basin) seawater intrusion is not present and not likely to occur. 6 The abbreviations for Minimum Threshold (MT) and Measurable Objective (MO) are provided because these terms are used often; however, the full unabbreviated term is used when helpful for clarity or when included in a quotation.

Bedford-Coldwater GSP 6-2

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6.1. SUSTAINABILITY GOAL
The sustainability goal can be described as the mission statement of the GSA for managing the Basin; it embodies the purpose of sustainably managing groundwater resources and reflects the local community’s values—economic, social, and environmental. The sustainability goal for the Basin, stated below, was developed through discussion at several GSA meetings.

6.1.1. Description of Sustainability Goal
The goal of the GSA in preparing this GSP is to sustain groundwater resources for the current and future beneficial uses of the Bedford-Coldwater Basin in a manner that is adaptive and responsive to the following objectives:
• Provide a long-term, reliable and efficient groundwater supply for municipal, industrial, and other uses;
• Provide reliable storage for water supply resilience during droughts and shortages; • Protect groundwater quality;
• Support beneficial uses of interconnected surface waters; and • Support integrated and cooperative water resource management.

This goal is consistent with SGMA and is based on information from the Plan Area, Hydrogeologic Conceptual Model, Groundwater Conditions, and Water Budget sections that:
• Identify beneficial uses of Basin groundwater and document the roles of local water and land use agencies;
• Describe the local hydrogeologic setting, groundwater quality conditions, groundwater levels and storage, and inflows and outflows of the Basin; and • Document the ongoing water resource monitoring and conjunctive management of groundwater, local surface water, recycled water and especially imported water sources that help protect groundwater quality and maintain water supply.

6.1.2. Approach to Sustainability Indicators
The approach to assessing the sustainability indicators and setting the sustainability criteria has been based on:
• Review of available information from the Plan Area, Hydrogeologic Conceptual Model, Groundwater Conditions, and Water Budget sections of the GSP. • Discussions with Bedford-Coldwater stakeholders and local agency representatives, GSA manager meetings, and workshops.

This approach has developed throughout the process and generally began with definition of what an undesirable result is; this initially has been exploratory and qualitative and based on plain-language understanding of what undesirable means. Potential minimum thresholds

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have been explored in terms of when, where, how long, why, under what circumstances, and what beneficial use is adversely affected. This step identified seawater intrusion as not present and not likely to occur.

Beyond a qualitative identification of what is undesirable, the approach to defining sustainability indicators varies among the undesirable results. Several of the undesirable results are directly or indirectly related to groundwater levels, including conditions related to groundwater storage, subsidence, and interconnected surface water. The definition began in terms of groundwater levels in individual wells but has recognized that storage depletion, subsidence, and impacts on connected surface water occur as waterlevels decline. As a result, the sustainability criteria for those indicators are interrelated across space and time, and are coordinated, consistent, and reasonable based on the available data.

The consideration of the causes and circumstances of undesirable results is an important one in Bedford-Coldwater as multiple agencies rely on this small Basin. Water is produced and used in the Basin by Temescal Valley Water District (TVWD) and produced for use in the Basin and in the neighboring Temescal and Elsinore Basins by the City of Corona (Corona) and Elsinore Valley Municipal Water District (EVMWD), respectively. Cooperative groundwater management between these three major agencies is essential to ensure sustainability.

The intent is to quantify and qualify sustainability criteria such that they guide good management without setting off false alarms or triggering costly, ineffective, or harmful management actions.

6.1.3. Summary of Sustainable Management Criteria
This section documents the six sustainability criteria as relevant to Bedford-Coldwater Basin and as guided by the Sustainability Goal. As documented in this section, the Basin has been and is being managed sustainably relative to all criteria (except seawater intrusion, which does not apply because the Basin is over 20 miles from the ocean). Accordingly, sustainability does not need to be achieved, but it does need to be maintained through the planning and implementation horizon. This will involve continuation and improvement of existing management actions. It also will include improvement and expansion of management actions and monitoring. These improvements are addressed for each sustainability criterion specific subsections.

While the Bedford-Coldwater Basin has been managed sustainably, the following sustainability criteria are defined in this section because potential exists for future undesirable results.
• The Minimum Threshold for defining undesirable results relative to chronic lowering of groundwater levels is defined at each Key Well by operational considerations to maintain water levels at or above current pump intakes or screen bottoms (whichever is higher) in municipal water supply wells. Undesirable results are indicated when two consecutive exceedances occur in each of two consecutive

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years, in two-thirds or more of the currently monitored wells in each Management Area.
• The Minimum Threshold for reduction of groundwater storage for all Management Areas is fulfilled by the minimum threshold for groundwater levels as proxy. • The Minimum Threshold for land subsidence is defined as a cumulative decline equal to or greater than one foot of decline since 2015, which represents current conditions and the SGMA start date. This is equivalent to a rate of decline equal to or greater than 0.2 feet in any five-year period. The extent of cumulative subsidence across the Basin will be monitored and evaluated using Interferometric Synthetic Aperture Radar (InSAR) data available through the SGMA Data Viewer during the 5- year GSP updates. Subsidence as a result of groundwater elevation decline is closely linked to groundwater levels and it is unlikely that significant inelastic subsidence would occur if groundwater levels remain above their minimum thresholds. • The Minimum Thresholds for degradation of water quality address nitrate and total dissolved solids (TDS) for the entire Basin.
o The Nitrate Minimum Threshold (in both Management Areas) is defined as 5-year average concentrations of all monitored wells not exceeding the 10 milligrams per liter (mg/L) drinking water maximum contaminant level (MCL) for Nitrate as Nitrogen.
o The TDS Minimum Threshold (in both Management Areas) is defined as the 5-year average concentrations not exceeding the 1,000 mg/L secondary MCL for TDS.
• The Minimum Threshold for depletion of interconnected surface water is the amount of depletion associated with the lowest water levels recorded during the 2010 to 2015 drought. Specifically, undesirable results would occur if more than half of monitored wells near Temescal Wash had static water levels lower than 35 feet below the adjacent riparian vegetation ground surface elevation for a period of more than one year.

6.2. CHRONIC LOWERING OF GROUNDWATER LEVELS
Chronic lowering of groundwater levels can indicate significant and unreasonable depletion of supply, causing undesirable results to domestic, agricultural, or municipal groundwater users if continued over the planning and implementation horizon. As a clarification, droughtrelated groundwater level declines are not considered chronic if groundwater recharge and discharge are managed such that groundwater levels recover fully during non-drought periods.

Declining groundwater levels directly relate to other potential undesirable effects (for example regarding groundwaterstorage, land subsidence and interconnected surface water); these are described in subsequent criterion specific sections.

Groundwater elevation trends in the Basin are represented by hydrographs documented in Groundwater Conditions Section 4.1. Over time, groundwater elevations have varied in response to precipitation, groundwater pumping, and groundwater use trends; however, the

Bedford-Coldwater GSP 6-5

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Basin does not display widespread chronic groundwater level declines and is not characterized by overdraft.

6.2.1. Description of Undesirable Results
As groundwater levels decline in a well, a sequence of increasingly severe undesirable results will occur. These include an increase in pumping costs and a decrease in pump output. With further declines, the pump may break suction, which means that the water level in the well has dropped to the level of the pump intake. This can be remedied by lowering the pump inside the well, which can cost thousands of dollars. Chronically declining water levels will eventually drop below the top of the well screen. This exposes the screen to air, which can produce two adverse effects. Water entering the well at the top of the screen will cascade down the inside of the well, and entraining air may result in cavitation damage to the pump.

The other potential adverse effect of exposure to air is accelerated corrosion of the well screen. Over time, corrosion creates a risk of well screen collapse, which often renders the well unusable. If water levels decline by more than about half of the total thickness of the aquifer (or total length of well screen), water might not be able to flow into the well at the desired rate regardless of the capacity or depth setting of the pump. This might occur where the thickness of basin fill materials is relatively thin. While describing a progression of potential adverse effects, at some point the well no longer fulfills its water supply purpose and is deemed to have “gone dry.” For the purposes of this discussion, a well going dry means that the entire screen length (to the bottom of the deepest screen) is unsaturated.

For purposes of setting a Minimum Threshold, undesirable results are defined as a well going dry. This appears to be a low standard and not protective of private wells but there are very few private wells in the Basin. The rationale is summarized as follows with more explanation in the following sections:
• There are very few active private wells in the Basin, as residential users are connected to municipal water supplies. The BCGSA is aware of a small number of private wells used for non-potable supply in the Basin. A systematic well inventory identifying all active private wells will be conducted to locate active wells and identify their uses, as described in Section 8.7. This project was designed to locate and characterize the construction and use of existing private wells so that they can be included in sustainable management of the Basin.
• Known private wells are for non-potable uses and are of similar depths and construction to the monitored municipal supply wells. No private wells have been reported to have water shortages in the California Department of Water Resources (DWR) led Household Water Supply Shortage Reporting System (DWR 2021). • Responsibility for potential undesirable results to shallow wells is shared between a GSA and a well owner; there is a reasonable expectation that a well owner would construct, maintain, and operate the well to provide its expected yield over the well’s life span, including droughts.

Bedford-Coldwater GSP 6-6

TODD GROUNDWATER,
H&H Water Resources,
and Stantec

6.2.2. Potential Causes of Undesirable Results
For Bedford-Coldwater Basin, the primary potential cause of declining groundwater levels and associated undesirable results would be increased groundwater production and/or reduced inflows (recharge). Given that the Bedford-Coldwater Basin is not characterized by basin-wide chronic groundwater level declines, then the undesirable results of a well losing yield, having damage, or “going dry” represent a more complex interplay of causes and shared responsibility.

Some of the potential causes are within the Bedford-Coldwater Groundwater Sustainability Agency (BCGSA) responsibility; most notably, a GSA is responsible for groundwater basin management without causing undesirable results such as chronic groundwater level declines.

SGMA also requires that a GSA address significant and unreasonable effects caused by groundwater conditions throughout the basin. This indicates that a GSA is not solely responsible for local or well-specific problems and furthermore that responsibility is shared with a well owner. A reasonable expectation exists that a well owner would construct, maintain, and operate the well to provide its expected yield over the well’slife span, including droughts, and with some anticipation that neighbors also might construct wells (consistent with land use and well permitting policies).

6.2.3. Definition of Undesirable Results
As context, the Bedford-Coldwater Sustainability Goal has the objective to provide a longterm, reliable, and efficient groundwater supply for municipal, industrial, and other uses.

In that light, the definition of undesirable results would be the chronic lowering of groundwater levels indicating a significant and unreasonable depletion of supply if continued over the planning and implementation horizon. This is defined by groundwater conditions occurring throughout the Basin, with a focus on operation of wells. This definition also recognizes that chronic lowering of groundwater levels could affect groundwater flow to or from the hydraulically connected Temescal and Elsinore Basins, and thereby potentially affect their ability to maintain sustainability.

As documented in Groundwater Conditions Section 4.1, analysis of hydrographs reveals that Bedford-Coldwater is not characterized by basin-wide chronic groundwater level declines.

While affected at times by drought, groundwater levels in broad areas of the Basin have been maintained at relatively stable levels. Moreover, the Bedford-Coldwater area has not been marked by reports of significant impacts to shallow supply wells as a result of water level declines. In the absence of reported well problems associated with declining groundwater levels, it can be concluded that undesirable results for the chronic lowering of water levels are not occurring in the Bedford-Coldwater and that the Basin is managed sustainably relative to groundwater levels.

Bedford-Coldwater GSP 6-7

TODD GROUNDWATER,
H&H Water Resources,
and Stantec

6.2.4. Potential Effects on Beneficial Uses and Users
Groundwater is a source of supply in the Basin and supplies water for municipal, industrial, and other beneficial uses. Groundwater has been and is being used for the range of beneficial uses, even during drought, and with reasonable operation and maintenance by well owners.

6.2.5. Sustainable Management Criteria for Groundwater Levels The general approach to defining sustainability criteria (minimum thresholds and measurable objectives) for groundwater levels has involved selection of representative monitoring wells, review of groundwater level data, and review of supply well location/construction information to gage potential undesirable effects on wells. Specifically, this has included evaluating historical water levels and well operations in monitored wells. This approach is founded on the idea that undesirable results are the reduction of available supply in these monitored wells.

6.2.5.1. Selection of MT by Well
The approach includes selection of existing wells currently monitored in the Basin.

Sustainability criteria would be defined for each of these wells, and each would be monitored for groundwater levels with respect to MTs and MOs. These wells are primarily production wells, which is not optimal for monitoring because pumping lowers water levels resulting in monitoring that is sometimes not representative of aquifer conditions. On the other hand, they are generally representative of production wells throughout the Basin.

Groundwater level data and hydrographs of each monitored well have been reviewed along with well construction and pumping equipment details in each monitored well. These data were used to review wellsthat the BCGSA currently monitorsto confirm that they are suitable for use as Key Wells for defining MTs and MOs. This process showed that all the wells that the BCGSA agencies currently monitor are appropriate for use as Key Wells and monitoring of these wells will continue in the future. Table 6-1 shows information on the Key Wells in the Basin. The table also shows well construction and pump intake information along with maximum historical depth to water and well-specific MT. The locations of the Key Wells are shown on Figure 6-1.

Table 6-1. Minimum Thresholds for Groundwater Levels
Local Well Name Agency Management Area Monitoring Frequency Total Well Depth
(feet)
Screen Interval
Depths (feet)
Pump Intake
Depth (feet)
Historical Maximum
Depth to Water (feet)
Date of Maximum
Depth to Water
Threshold
Description
Threshold Depth to
Water (feet)
Corona Well 20 Corona Coldwater Static - Monthly 660 200 to 580 460 375.10 1/17/2017 Pump intake 460 Corona Well 21 Corona Coldwater Static - Monthly 660 200 to 580 460 398.00 12/1/2001 Pump intake 460 Corona Well 3 Corona Coldwater Static - Monthly 543 100 to 530 479 392.00 12/16/2016 Pump intake 479 Corona Non-Potable Well 1 Corona Bedford Continuous (SCADA) Unkown Unkown Unkown 55.60 11/13/2016 Nearby pump intake 80 Corona Non-Potable Well 2 Corona Bedford Continuous (SCADA) Unkown Unkown Unkown 55.40 11/13/2016 Nearby pump intake 80 EVMWD Flagler 2A Well EVMWD Bedford Continuous (SCADA) 105 51 to 92 80 48.00 10/18/2019 Pump intake 80 EVMWD Flagler 3A Well EVMWD Bedford Continuous (SCADA) 100 51 to 90 80 57.00 10/18/2019 Pump intake 80 Corona & EVMWD Trilogy EVMWD Coldwater Quarterly 579
250 to 360 and 390 to
450 No pump 359.30 10/12/2016
Ten feet above bottom
of screen 440
EVMWD Station 71 EVMWD Bedford Quarterly 600 239 to 588 507 499.92 7/21/2017 Pump intake 507 EVMWD Mayhew Well 2 EVMWD Coldwater Quarterly 740 300 to 730 507 440.99 11/28/2017 Pump intake 507 TVWD Well 1 (Old well) TVWD Bedford Continuous (SCADA) 100 40 to 80 No pump 42.50 11/1/2016 Ten feet above bottom
of screen 70
TVWD Well 1A TVWD Bedford Continuous (SCADA) 100 40 to 80 85 53.40 11/15/2016 Ten feet above bottom
of screen 70
TVWD Well 4 TVWD Bedford Continuous (SCADA) 100 40 to 80 85 46.80 10/7/2015 Ten feet above bottom
of screen 70
TVWD TP-1 TVWD Bedford Continuous (SCADA) 103 39 to 99 85 Unknown Unknown Pump intake 85 TVWD TP-2 TVWD Bedford Continuous (SCADA) 90 30 to 85 85 Unknown Unknown Ten feet above bottom
of screen 75
TVWD Foster TVWD Bedford Continuous (SCADA) 93 38 to 88 84 Unknown Unknown Ten feet above bottom
of screen 78
TVWD New Sump TVWD Bedford Continuous (SCADA) 74 Unkown 66 101.67 8/1/1994 Pump intake 66 T:\Projects\Bedford Coldwater GSP 80802\Deliverables\GSP\6 Sustainability Criteria\Sustainability Tables v2.xlsx - WL Summary Todd Groundwater Des by: MR
Ckd by: CT
6-8

Bedford-Coldwater GSP 6-9

TODD GROUNDWATER,
H&H Water Resources,
and Stantec

6.2.6. Minimum Thresholds
According to GSP Regulations Section 354.28(c)(1), the minimum threshold for chronic lowering of groundwater levels must be the groundwater elevation indicating a depletion of supply at a given location that may lead to undesirable results. MTs for chronic lowering of groundwater levels are to be supported by information on the rate of groundwater elevation decline based on historical trends, water year type, and projected water use in the Basin.

However, as documented in the Groundwater Conditions Section 4.1.3, groundwater levels are not chronically declining in Bedford-Coldwater. While groundwater levels decline in dry and critically-dry years, they have recovered in normal, above normal, and wet years.

Groundwater levels in some wells were at historical lows after the recent drought ending in 2016 but are recovering.

Currently, none of the wells have groundwater levels below their respective MTs and no undesirable results are known to have occurred in the past. Nonetheless, MTs have been developed because the potential exists for chronic lowering of groundwater levels in the future.

Using available recent and reliable information on the construction of existing supply wells, the MT levelsshown in Table 6-1 are protective of mostsupply wells. Based on historical lows, the MTs account for historical groundwater level variations, and consideration has been given to supporting Basin management flexibility, for example to avoid setting off false alarms or triggering costly, ineffective, or harmful management actions.

The MTs shown in Table 6-1 were developed making use of available data. However, uncertainties exist as summarized below:
• The geographic distribution of wells in the groundwater level monitoring program is uneven.
• Information on vertical groundwater gradients is lacking and groundwater levels in shallow wells may not be represented adequately by relatively deep wells. • The specific location, status, and construction of most existing private wells is not known, or the information is not readily available (in databases).

These uncertainties have been recognized and are being addressed in this GSP as follows:
• Mapping and prioritization of geographic gaps in the monitoring program. • Installation of two new dedicated monitoring wells sited and designed to support the groundwater level monitoring program (among other objectives) and to become Key Wells.
• Identification and mapping of existing active private production wells within the Basin, as described in Section 8 Projects and Management Actions.

The benefits of these efforts will accrue over the next few years and will support review and update of the MTs in the 5-Year GSP Update in 2027.

Bedford-Coldwater GSP 6-10

TODD GROUNDWATER,
H&H Water Resources,
and Stantec

6.2.6.1. Minimum Thresholds and Criteria for Undesirable Results Undesirable results are based on exceedances of MT levels and must be defined not only in terms of how they occur (as described in Section 6.2.2 Potential Causes of Undesirable Results), but also when and where. By definition, undesirable results are not just droughtrelated but chronic and are not just local but basin-wide.

The distinction between drought and chronic declines may not be clear when declines are occurring, particularly during drought when it is not known whether subsequent years will bring recovery. Moreover, effects of declining levels on individual well owners may be real problems, whether or not they represent basin-wide sustainability issues.

The BCGSA will perform quarterly or more frequent groundwater level monitoring.

Accordingly, groundwater level monitoring and annual reporting provides an early warning system that allows response by the BCGSA and local groundwater users. From this perspective, two consecutive exceedances in each of two consecutive years is regarded as indicating when an undesirable result is occurring. The exceedances would be measured at a Key Well as part of the regular quarterly monitoring program. It should be noted that GSA responses do not have to wait for two years and may involve a staged response as in urban water shortage contingency plans.

While undesirable results relate to groundwater conditions throughout the Basin, the Basin has been organized into two management areas (MAs). As discussed in Section 5.4, this reflects the fact that the Basin is separated by a fault zone, limiting (but not eliminating) flow between the two MAs. Groundwater level MTs will be evaluated separately for each MA, because the groundwater histories are distinct, albeit linked. As a result, undesirable results could occur in one MA and not the other. Accordingly, undesirable results are indicated to be occurring when two-thirds or more of the currently monitored wells in the MA have had two consecutive exceedances in each of two consecutive years.

To summarize for the Bedford-Coldwater Basin:

The Minimum Threshold for defining undesirable results relative to chronic lowering of groundwater levels is defined at each Key Well by operational considerations to maintain waterlevels at or above current pump intakes orscreen bottoms(whichever is higher) in municipal watersupply wells. Undesirable results are indicated when two consecutive exceedances occur in each of two consecutive years, in two-thirds or more of the currently monitored wells in each Management Area.

6.2.6.2. Relationship of Minimum Threshold to Other Sustainability Indicators The establishment of MTs also needs to consider potential effects on other sustainability indicators. These indicators are discussed later in this section; the following are brief discussions.
• Groundwater Storage. The MTs for groundwater levels are protective of groundwater storage. These MTs are defined in terms of operational considerations

Bedford-Coldwater GSP 6-11

TODD GROUNDWATER,
H&H Water Resources,
and Stantec
for wells used to support beneficial uses in the Basin. The major concern expressed in the Sustainability Goal is to have reliable storage for drought conditions. As the water level MTs support maintenance of production capacity in wells, they also support maintenance of reliable storage.
• Seawater Intrusion. There is no possibility of seawater intrusion in the BedfordColdwater Basin as it is more than 20 miles from the ocean. Accordingly, there is no seawater intrusion minimum threshold and no relationship with other minimum thresholds.
• Subsidence. Subsidence is linked to groundwater levels. It is unlikely that significant inelastic subsidence would occur if groundwater levels remain within the operational range of water levels, which have been used to define groundwater level MTs. Accordingly, the minimum threshold for groundwater levels is consistent with and supportive of the objective to prevent subsidence undesirable results. • Water Quality. General relationships are recognized, for example that contaminants may be mobilized by changing groundwater levels or flow patterns. Maintenance of groundwater levels within historical operational ranges would minimize any effects on maintenance of water quality at or above minimum thresholds. The groundwater quality issues in Bedford-Coldwater Basin are associated primarily with salt and nutrient loading and not likely to be affected by groundwater levels or flow within operational ranges.
• Interconnected Surface Water. The set of monitoring wells used to evaluate interconnected surface water overlaps with the set of wells used for the groundwater levels minimum threshold. In general, the MTs for interconnected surface water are similar to or higher than those for groundwater levels; the higher MTs would be controlling.

6.2.6.3. Effect of Minimum Threshold on Sustainability in Adjacent Areas The Bedford-Coldwater Basin is adjacent to the Temescal Basin and the Elsinore Basin.

Groundwater flow directions are from the Elsinore Basin through Bedford MA to the Temescal Basin with some drainage into the Temescal Wash. The Bedford-Coldwater groundwater level MTs would support maintenance of groundwaterlevels above theirrespective MTsin Bedford MA. This in turn will support maintenance of groundwater levels in the Temescal Basin.

6.2.6.4. Effect of Minimum Threshold on Beneficial Uses and Users Groundwater is the major source of supply in the GSP Area and supplies wells for municipal, industrial, and other beneficial uses and users. The MTs are based generally on well operations, which recognizes that groundwater has been and is being used reasonably for the range of beneficial uses even during drought, and with reasonable operation and maintenance by well owners. The MTs quantify undesirable results as involving two-thirds of wells in a MA with two consecutive exceedances in each of two consecutive years, which provides early warning of declining groundwater levels.

While there are a small number of private wells in the Basin, there are no DACs or SDACs in the Basin and the only private domestic well in the Basin belongs to the Glenn Ivy Hot Springs.

Bedford-Coldwater GSP 6-12

TODD GROUNDWATER,
H&H Water Resources,
and Stantec
The BCGSA believes that all other private wells in the Basin are used for non-potable supply.

Project 2 (described in Section 8.7) is designed to locate and characterize the construction and use of all existing active private wells to ensure that the minimum threshold for groundwater levels is protective of all users in the Basin, recognizing the human right to water.

6.2.6.5. Relationship of Minimum Threshold to Regulatory Standards No federal, state or local standards exist for groundwater levels.

6.2.6.6. How Management Areas Can Operate without Causing Undesirable Results The establishment of MTs has been consistently conceived and applied across both Management Areas. MTs are based on well operations, which vary from well to well representing local conditions that do not necessarily occur at the same time across the MAs.

Maintenance of water levels within the operational range in wells is not anticipated to cause undesirable results between the two MAs.

6.2.6.7. How the Minimum Threshold will be Monitored
Monitoring for the groundwater levels MT will be conducted as part of the BCGSA groundwater level monitoring program, data and analytical results will be presented in the Annual GSP Reports. The BCGSA monitoring program includes wells monitored by Corona, EVMWD, and TVWD.

6.2.7. Measurable Objectives
Measurable Objectives are defined herein as an operating range of groundwater levels, allowing reasonable fluctuations with changing hydrologic and surface water supply conditions and with conjunctive management of imported water and groundwater. The groundwater level MTs represent the bottom of the operating range and are protective of groundwater users. The top of the operating range is generally where the water table approaches the soil zone and ground surface, except where groundwater and surface water are interconnected or groundwater dependent ecosystems exist. Section 6.7 addresses these areas and potential undesirable results with Depletions of Interconnected Surface Water.

With these important exceptions, the top of the operating range is below the soil zone, thereby minimizing potential agricultural drainage problems.

The Measurable Objective is to maintain groundwater levels above the historical maximum depth to groundwater, and to maintain groundwater levels within the operating range as defined in this section.

Groundwater conditions with respect to chronic groundwater level declines are already sustainable. Therefore, no interim milestones are needed to achieve sustainability by 2042.