Corona City Council
June 3, 2026

Water Audit Report for:

Audit Year:

All volumes to be entered as: ACRE-FEET PER YEAR
WATER SUPPLIED choose entry option:

VOS Volume from Own Sources: n g 9 26,986.484 Acre-ft/Yr n g 10 0.00% percent acre-ft/yr under-registration VOSEA WI Water Imported: n g 9 700.020 Acre-ft/Yr n g 9 0.00% percent acre-ft/yr under-registration WIEA WE Water Exported: n g 9 349.439 Acre-ft/Yr n g 7 0.00% percent acre-ft/yr under-registration WEEA 27,337.065 Acre-ft/Yr
.

AUTHORIZED CONSUMPTION
BMAC Billed Metered: n g 8 26,049.000 Acre-ft/Yr
BUAC Billed Unmetered: n g n/a 0.000 Acre-ft/Yr
UMAC Unbilled Metered: n g 10 82.096 Acre-ft/Yr choose entry option:

UUAC Unbilled Unmetered: n g 3 65.123 Acre-ft/Yr 0.25% default acre-ft/yr 24061 Default option selected for Unbilled Unmetered, with automatic data grading of 3 26,196.219 Acre-ft/Yr
WATER LOSSES 1,140.847 Acre-ft/Yr
Apparent Losses
Default option selected for Systematic Data Handling Errors, with automatic data grading of 3 choose entry option:

SDHE Systematic Data Handling Errors: n g 3 65.123 Acre-ft/Yr 0.25% default acre-ft/yr CMI Customer Metering Inaccuracies: n g 3 533.288 Acre-ft/Yr 2.00% percent acre-ft/yr under-registration UC Unauthorized Consumption: n g 3 65.123 Acre-ft/Yr 0.25% default acre-ft/yr Default option selected for Unauthorized Consumption, with automatic data grading of 3 663.533 Acre-ft/Yr
Real Losses
477.314 Acre-ft/Yr
1,140.847 Acre-ft/Yr

NON-REVENUE WATER
1,288.065 Acre-ft/Yr

SYSTEM DATA
Lm Length of mains: n g 10 712.6 miles (including fire hydrant lead lengths) Nc Number of service connections: n g 8 46,693 (active and inactive) Service connection density: 66 conn./mile main
Yes
Lp Average length of (private) customer service line: n g 10 ft (average distance between property line and meter) AOP Average Operating Pressure: n g 9 96.8 psi

COST DATA
CRUC Customer Retail Unit Charge: n g 10 $2.78
VPC Variable Production Cost: n g 8 $901.89 $/acre-ft $/yr (optional input) WATER AUDIT DATA VALIDITY TIER:
go to
dashboard
PRIORITY AREAS FOR ATTENTION TO IMPROVE DATA VALIDITY: KEY PERFORMANCE INDICATOR TARGETS:

Based on the information provided, audit reliability can be most improved by addressing the following components: OPTIONAL: If targets exist for the operational performance indicators, they can be input below:
1: Customer Metering Inaccuracies (CMI) Unit Total Losses: gal/conn/day 2: Billed Metered (BMAC) Unit Apparent Losses: gal/conn/day 3: Volume from Own Sources (VOS) Unit Real LossesA
: gal/conn/day
Unit Real LossesB: gal/mile/day
If entered above by user, targets will display on KPI gauges (see Dashboard) go to start page
NON-REVENUE WATER:

If entering an
Error Adjustment,
select under- or overregistration
WATER SUPPLIED:

AUTHORIZED CONSUMPTION:

Apparent Losses:

Average length of customer service line has been set to zero and a data grading of 10 has been applied A weighted scale for the components of supply, consumption and water loss is included in the calculation of the Water Audit Data Validity Score *** The Water Audit Data Validity Score is in Tier IV (71-90). See Dashboard tab for additional outputs. *** $/100 cubic feet (ccf)
$51,772,725
Total Annual Operating Cost
Are customer meters typically located at the curbstop/property line? AWWA Free Water Audit Software:

Worksheet
City of Corona
Jul 01 2023 - Jun 30 2024
Water Supplied Error Adjustments
Fiscal2024
Real Losses:

WATER LOSSES:

Click 'g' to determine data validity grade
Click 'n' to add notes
FWAS v6.0
American Water Works Association.

To access definitions, click the input name
To edit water system info:

AWWA Free Water Audit Software v6.0 Worksheet 1

Water Balance Water Audit Report for:

Audit Year: 2024 Jul 01 2023 - Jun 30 2024
Data Validity Tier: Tier IV (71-90)
Water Exported
(WE)
(corrected for known
errors)
Revenue Water
(Exported)
349.439 349.439
Billed Metered Consumption (BMAC)
(water exported is removed) Revenue Water
26,049.000
26,049.000 Billed Unmetered Consumption (BUAC) 26,049.000

0.000
26,196.219 Unbilled Metered Consumption (UMAC)

82.096
26,986.484 147.219 Unbilled Unmetered Consumption (UUAC)

65.123
Water Supplied Systematic Data Handling Errors (SDHE) 1,288.065 27,686.504 Apparent Losses 65.123
27,337.065 663.533 Customer Metering Inaccuracies (CMI) 533.288
Unauthorized Consumption (UC)
Water Losses 65.123
1,140.847 Leakage on Transmission and/or Distribution Mains Real Losses Not broken down
700.020 477.314 Leakage and Overflows at Utility's Storage Tanks Not broken down
Leakage on Service Connections
Not broken down
Water Imported (WI)
(corrected for known
errors)
AWWA Free Water Audit Software
Non-Revenue Water
(NRW)
Billed Authorized Consumption
Unbilled Authorized Consumption
(corrected for known
errors)
City of Corona
Billed Water Exported
Volume from Own
Sources (VOS)
System Input
Volume
Authorized
Consumption
FWAS v6.0
American Water Works Association.

Copyright © 2020, All Rights Reserved.

AWWA Free Water Audit Software v6.0 Water Balance Page 574 of 3451 1 0 AWWA Free Water Audit Software: Dashboard
Water Audit Report for: City of Corona Audit Year: Fiscal Jul 01 2023 - Jun 30 2024 Actual KPI result Target (see Worksheet)
1 US$ = Local
Data Validity Score: Data Validity Tier: enter current conversion rate for local currency Tier II (26-50) Tier III (51-70)
Tier IV (71-90)
Tier I (≤25)
Tier V (91-100)
Total Loss Cost Rate Apparent Loss Cost Rate Real Loss Cost Rate $/conn/year $/conn/year $/conn/year
NRW Components Summary
Unit Total Losses Unit Apparent Losses Unit Real LossesA gal/conn/day gal/conn/day gal/conn/day
Average Operating Pressure
psi
Infrastructure Leakage Index (ILI) Unit Real LossesB
dimensionless gal/mile/day
See UARL definition for additional guidance on the ILI
Real Losses Unauthorized Consumption Acre-ft/Yr gal/conn/daySystematic Data Handling Errors Unbilled Unmetered Auth ConsCustomer Metering Inaccuracies Unbilled Metered Authorized Cons Apparent Losses
Real Losses
Unbilled Authorized Cons
Non-Revenue Water
0 Blended
147.2
1,288.1
$802,999$430,485$132,775
$1,366,258
663.5477.3 VPC
Volume Value
Acre-ft/Yr $/Yr
(UARL) Unavoidable Annual Real Losses 1,177.5 22.5
VPC

0.4 598
result is below
10th %ile
result is below
10th %ile

9.1 96.8
CRUC
Basis of Valuation

26.42 21.8

17.20 12.7
result is below
10th %ile

9.22 go to referencesgo to worksheet go to grading
2024
78 Tier IV (71-90)
Data Validity
gauge %iles per validated industry ranges2

0.737
Loss Control Planning for Tier DetailsSee
Key Performance Indicators
0 200400600800
1,0001,2001,400
Volume (Acre-ft/Yr)
Total Volume of NRW = 1,286
Acre-ft/Yr
$0$200,000$400,000$600,000$800,000$1,000,000$1,200,000$1,400,000$1,600,000 Total Cost of NRW =
$1,366,258/Yr
10th %ile
25th %ile
Median
75th %ile
90th %ile
2 3 4
2 3 4
2 3 4
2 3 4
2 3 4
American Water Works Association.

Copyright © 2020, All Rights Reserved.

FWAS v6.0
2 3
4 2
3 4
Median
90th %ile90th %ile90th %ile
Median Median
Median
Median Median
Median Median
25th
%ile
25th
%ile
25th
%ile
25th
%ile 25th
%ile
25th
%ile
25th
%ile
25th
%ile
75 75 th %ile 75th %ile th %ile
75th %ile 75th %ile 75th %ile
75 75 th %ile th %ile
10th %ile10th %ile10th %ile
90 10th %ile 90 th %ile th %ile10th %ile
90th %ile90th %ile90th %ile 10th %ile10th %ile10th %ile Guidance Information for Key Performance Indicators
AWWA Free Water Audit Software v6.0 Dashboard 1 Page 575 of 3451 Table 1 Source: AWWA Water Loss Control Committee Report (2020)1, with naming conventions updated 2020 AWWA Water Audit Method – Water Audit Outputs and Key Performance Indicators: Uses and Limitations Type Indicator Description
Suitable Purposes
Uses and Limitations Principal Users Assessment Bench- Marking Target- Setting Planning Tracking Attribute Apparent Loss Volume Calculated by Free Water Audit Software   Assess loss level Utility, Regulators Apparent Loss Cost Calculated by Free Water Audit Software   Assess cost loss level Utility, Regulators Real Loss Volume Calculated by Free Water Audit Software   Assess loss level Utility, Regulators Real Loss Cost Calculated by Free Water Audit Software   Assess loss cost level Utility, Regulators Unavoidable Annual
Real Loss (UARL)
Calculated by Free Water Audit Software   Reveal theoretical technical low level of leakage
Utility, Regulators
Volume Unit Apparent Losses
(vol/conn/day)
Strong and understandable indicator for multiple users.      Used for performance
tracking and target-setting
Utility, Regulators
Unit Real LossesA(vol/conn/day)
Strong and understandable indicator for multiple users.      Used for performance
tracking and target-setting
Utility, Regulators, Policy Makers
Unit Real LossesB(vol/pipeline length/ day)
Strong and understandable indicator for use by utilities with low connection density.      Data collection and
assessment of systems with “low” connection density
Utility, Regulators, Policy Makers
Unit Total Losses (vol/conn/day) New KPI
Strong and understandable indicator, suitable for high-level performance measurement.   High level indicator for
trending analysis. Not appropriate for target-setting or benchmarking Utilities, Customers
Infrastructure Leakage Index (ILI)
Robust, specialized ratio KPI; can be influenced by pressure and connection density.    Benchmarking after pressure
management is implemented
Utilities
Value Apparent Loss Cost
Rate (value/conn/year) New KPI
Indicators with sufficient technical rigor. Provide the unit financial value of each type of loss, which is useful for planning and assessment of cost efficiency of water loss reduction and control interventions and programs.    Data collection and
assessment on AWWA indicators or contextual parameters to use in conjunction with Loss Cost Rates Utilities, Regulators, Customers
Real Loss Cost Rate (value/conn/year) New KPI
   Utilities,
Regulators, Customers
Validity Data Validity Tier
(DVT)
Strong indicator of water loss audit data quality, if data has been validated. Tier provides guidance on priority areas of activity.     Assess caliber of data inputs
of the water audit
Regulators, Utilities
AWWA Free Water Audit Software v6.0 Dashboard 2 Page 576 of 3451

6.0_2021_02_11
Name of Utility: VOS Volume from Own Sources
Name of Contact Person: VOSEA VOS Error Adjustment
Email: WI Water Imported
Telephone | Ext.: WIEA WI Error Adjustment
City/Town/Municipality: WE Water Exported
State / Province: WEEA WE Error Adjustment
Other State/Province: BMAC Billed Metered Authorized Consumption Country: BUAC Billed Unmetered Authorized Consumption
Audit Preparation Date: UMAC Unbilled Metered Authorized Consumption Audit Year: UUAC Unbilled Unmetered Authorized Consumption Audit Year Label: (Fiscal, Calendar, etc) SDHE Systematic Data Handling Errors Audit Period Start Date: CMI Customer Metering Inaccuracies Audit Period End Date: UC Unauthorized Consumption
Volume Reporting Units: Lm Length of mains
Water System Structure: Nc Number of service connections Water Type: Lp Average length of (private) customer service line System ID Number: AOP Average Operating Pressure
Validator Name/ID: CRUC Customer Retail Unit Charge
Validator Email: VPC Variable Production Cost
Estimated Total Population Served by Water Utility:

Color Key User input Calculated Optional default
Guidance for the Guidance for the
or
AWWA Web Resources for Water Loss Control
https://www.awwa.org/Resources-Tools/Resource-Topics/Water-Loss-Control or Items referenced in the Free Water Audit Software v6.0 on the web:

Data Grading Matrix v6.0Example Water Audit v6.0Water Audit Compiler v6.0 AWWA Reports on Performance Indicators
M36 Manual
If you have questions or comments regarding this software please contact us at: [email protected] Answer questions about operational practices for each
audit input, and the data validity grades will automatically populate.Review NRW components, performance indicators and graphical outputs to evaluate the results of the audit. Enter notes to explain how values were calculated, document data sources, and related information about data management practices.

Interactive Data
Grading
951-736-2265CoronaUnited States
Acre-feet
Nov 04 2025California (CA)Jun 30 2025Jul 01 2024Fiscal2025 Enter the required data on this worksheet to calculate the water balance and data grading.

Water Balance
Loss Control
Planning
AWWA Free Water Audit Software v6.0
Enter Basic Information
Stacy [email protected]
Table of Contents (TOC)
The current sheet. Enter contact information and basic audit details.

Key of Input Acronyms In order of appearance in the Worksheet City of Corona
This spreadsheet-based water audit tool is designed to help quantify and track water losses associated with water distribution systems and identify areas for improved efficiency and cost recovery. It provides a "top-down" summary water audit format and is not meant to take the place of a full-scale, comprehensive water audit format. Auditors are strongly encouraged to refer to the most current edition of AWWA M36 Manual for Water Audits for detailed guidance on the water auditing process and targeting loss reduction levels. This tool contains several separate worksheets. Sheets can be accessed using the tabs at the bottom of the screen, or by clicking the TOC links below.

Start Page
Blank Sheet
Worksheet
Interactive Data Grading
After clicking an acronym button, answer all visible questions in the order they're presented, choosing best-fit answer
Dashboard
Notes
Acknowledgements for development of the AWWA Free
Water Audit Software v6.0.

Acknowledgements
By popular demand! A blank sheet. The world is your canvas.The values entered in the Worksheet automatically populate the Water Balance.Use this sheet to interpret the results of the audit validity score and performance indicators.Use this sheet to understand the terms used in the audit process.Diagrams depicting possible customer service connection line configurations.

Definitions
Service
Connection
Diagram
Choosing to enter unit of percent or volume
(applies to VOSEA, WIEA, WEEA, CMI)
Limiting
Choosing to enter default or custom input
(applies to UUAC, SDHE, UC)
choose entry option:

1.00% percent
7 Grade will populate when all visible questions are complete for an input The limiting criteria will be labeled along the right. If only 1 limiting criterion is shown, improving on that criterion will achieve a higher data grade. If multiple limiting criteria are shown, improving on each limiting criterion is necessary to achieve a higher data grade. A complete inventory of data grading criteria is available in the Data Grading Matrix v6.0 (see web resources)

0.25%
RetailPotable Water
custom 75.000volume 25.000
default
CA3310037Damian Martinez
Use acronym buttons in IDG header to navigate among inputs. Acronym Key above.

White = needs answers, orange = complete, clear = not required. Example below. 169,245
[email protected]
choose entry option:

Worksheet
American Water Works Association Copyright © 2020, All Rights Reserved.

FWAS v6.0
AWWA Free Water Audit Software v6.0 Start Page 1

Water Audit Report for:

Audit Year:

All volumes to be entered as: ACRE-FEET PER YEAR
WATER SUPPLIED choose entry option:

VOS Volume from Own Sources: n g 9 30,179.128 Acre-ft/Yr n g 10 0.00% percent acre-ft/yr under-registration VOSEA WI Water Imported: n g 9 565.543 Acre-ft/Yr n g 9 0.00% percent acre-ft/yr under-registration WIEA WE Water Exported: n g 9 365.045 Acre-ft/Yr n g 7 0.00% percent acre-ft/yr under-registration WEEA 30,379.626 Acre-ft/Yr
.

AUTHORIZED CONSUMPTION
BMAC Billed Metered: n g 8 28,598.000 Acre-ft/Yr
BUAC Billed Unmetered: n g n/a 0.000 Acre-ft/Yr
UMAC Unbilled Metered: n g 10 87.141 Acre-ft/Yr choose entry option:

UUAC Unbilled Unmetered: n g 3 71.495 Acre-ft/Yr 0.25% default acre-ft/yr 24061 Default option selected for Unbilled Unmetered, with automatic data grading of 3 28,756.636 Acre-ft/Yr
WATER LOSSES 1,622.990 Acre-ft/Yr
Apparent Losses
Default option selected for Systematic Data Handling Errors, with automatic data grading of 3 choose entry option:

SDHE Systematic Data Handling Errors: n g 3 71.495 Acre-ft/Yr 0.25% default acre-ft/yr CMI Customer Metering Inaccuracies: n g 3 585.411 Acre-ft/Yr 2.00% percent acre-ft/yr under-registration UC Unauthorized Consumption: n g 3 71.495 Acre-ft/Yr 0.25% default acre-ft/yr Default option selected for Unauthorized Consumption, with automatic data grading of 3 728.401 Acre-ft/Yr
Real Losses
894.589 Acre-ft/Yr
1,622.990 Acre-ft/Yr

NON-REVENUE WATER
1,781.626 Acre-ft/Yr

SYSTEM DATA
Lm Length of mains: n g 10 715.0 miles (including fire hydrant lead lengths) Nc Number of service connections: n g 8 46,569 (active and inactive) Service connection density: 65 conn./mile main
Yes
Lp Average length of (private) customer service line: n g 10 ft (average distance between property line and meter) AOP Average Operating Pressure: n g 9 97.0 psi

COST DATA
CRUC Customer Retail Unit Charge: n g 10 $3.00
VPC Variable Production Cost: n g 8 $904.54 $/acre-ft $/yr (optional input) WATER AUDIT DATA VALIDITY TIER:
go to
dashboard
PRIORITY AREAS FOR ATTENTION TO IMPROVE DATA VALIDITY: KEY PERFORMANCE INDICATOR TARGETS:

Based on the information provided, audit reliability can be most improved by addressing the following components: OPTIONAL: If targets exist for the operational performance indicators, they can be input below:
1: Customer Metering Inaccuracies (CMI) Unit Total Losses: gal/conn/day 2: Billed Metered (BMAC) Unit Apparent Losses: gal/conn/day 3: Volume from Own Sources (VOS) Unit Real LossesA
: gal/conn/day
Unit Real LossesB: gal/mile/day
If entered above by user, targets will display on KPI gauges (see Dashboard) Are customer meters typically located at the curbstop/property line? AWWA Free Water Audit Software:

Worksheet
City of Corona
Jul 01 2024 - Jun 30 2025
Water Supplied Error Adjustments
Fiscal2025
Real Losses:

WATER LOSSES:

Average length of customer service line has been set to zero and a data grading of 10 has been applied A weighted scale for the components of supply, consumption and water loss is included in the calculation of the Water Audit Data Validity Score *** The Water Audit Data Validity Score is in Tier IV (71-90). See Dashboard tab for additional outputs. *** $/100 cubic feet (ccf)
$56,242,713
Total Annual Operating Cost
go to start page
NON-REVENUE WATER:

If entering an
Error Adjustment,
select under- or overregistration
WATER SUPPLIED:

AUTHORIZED CONSUMPTION:

Apparent Losses:

Click 'g' to determine data validity grade
Click 'n' to add notes
FWAS v6.0
American Water Works Association.

To access definitions, click the input name
To edit water system info:

AWWA Free Water Audit Software v6.0 Worksheet 1

Water Balance Water Audit Report for:

Audit Year: 2025 Jul 01 2024 - Jun 30 2025
Data Validity Tier: Tier IV (71-90)
Water Exported
(WE)
(corrected for known
errors)
Revenue Water
(Exported)
365.045 365.045
Billed Metered Consumption (BMAC)
(water exported is removed) Revenue Water
28,598.000
28,598.000 Billed Unmetered Consumption (BUAC) 28,598.000

0.000
28,756.636 Unbilled Metered Consumption (UMAC)

87.141
30,179.128 158.636 Unbilled Unmetered Consumption (UUAC)

71.495
Water Supplied Systematic Data Handling Errors (SDHE) 1,781.626 30,744.671 Apparent Losses 71.495
30,379.626 728.401 Customer Metering Inaccuracies (CMI) 585.411
Unauthorized Consumption (UC)
Water Losses 71.495
1,622.990 Leakage on Transmission and/or Distribution Mains Real Losses Not broken down
565.543 894.589 Leakage and Overflows at Utility's Storage Tanks Not broken down
Leakage on Service Connections
Not broken down
Water Imported (WI)
(corrected for known
errors)
AWWA Free Water Audit Software
Non-Revenue Water
(NRW)
Billed Authorized Consumption
Unbilled Authorized Consumption
(corrected for known
errors)
City of Corona
Billed Water Exported
Volume from Own
Sources (VOS)
System Input
Volume
Authorized
Consumption
FWAS v6.0
American Water Works Association.

Copyright © 2020, All Rights Reserved.

AWWA Free Water Audit Software v6.0 Water Balance Page 579 of 3451 1 0 AWWA Free Water Audit Software: Dashboard
Water Audit Report for: City of Corona Audit Year: Fiscal Jul 01 2024 - Jun 30 2025 Actual KPI result Target (see Worksheet)
1 US$ = Local
Data Validity Score: Data Validity Tier: enter current conversion rate for local currency Tier II (26-50) Tier III (51-70)
Tier IV (71-90)
Tier I (≤25)
Tier V (91-100)
Total Loss Cost Rate Apparent Loss Cost Rate Real Loss Cost Rate $/conn/year $/conn/year $/conn/year
NRW Components Summary
Unit Total Losses Unit Apparent Losses Unit Real LossesA gal/conn/day gal/conn/day gal/conn/day
Average Operating Pressure
psi
Infrastructure Leakage Index (ILI) Unit Real LossesB
dimensionless gal/mile/day
See UARL definition for additional guidance on the ILI
Real Losses Unauthorized Consumption Acre-ft/Yr gal/conn/daySystematic Data Handling Errors Unbilled Unmetered Auth ConsCustomer Metering Inaccuracies Unbilled Metered Authorized Cons Apparent Losses
Real Losses
Unbilled Authorized Cons
Non-Revenue Water
0 2025
78 Tier IV (71-90)
Data Validity
gauge %iles per validated industry ranges2

0.737
Loss Control Planning for Tier DetailsSee
Key Performance Indicators

17.38 go to referencesgo to worksheet go to grading

37.80 31.1

20.42 14.0
(UARL) Unavoidable Annual Real Losses 1,179.3 22.6
VPC

0.8 1,117
result is below
10th %ile

17.1 97
CRUC
Basis of Valuation
Blended
158.6
1,781.6
$951,159$809,191$143,493
$1,903,843
728.4894.6 VPC
Volume Value
Acre-ft/Yr $/Yr
0 200400600800
1,0001,2001,4001,6001,8002,000
Volume (Acre-ft/Yr)
Total Volume of NRW = 1,780
Acre-ft/Yr
$0$200,000$400,000$600,000$800,000$1,000,000$1,200,000$1,400,000$1,600,000$1,800,000$2,000,000 Total Cost of NRW =
$1,903,843/Yr
10th %ile
25th %ile
Median
75th %ile
90th %ile
2 3 4
2 3 4
2 3 4
2 3 4
2 3 4
American Water Works Association.

Copyright © 2020, All Rights Reserved.

FWAS v6.0
2 3
4 2
3 4
Median
90th %ile90th %ile90th %ile
Median Median
Median
Median Median
Median Median
25th
%ile
25th
%ile
25th
%ile
25th
%ile 25th
%ile
25th
%ile
25th
%ile
25th
%ile
75 75 th %ile 75th %ile th %ile
75th %ile 75th %ile 75th %ile
75 75 th %ile th %ile
10th %ile10th %ile10th %ile
90 10th %ile 90 th %ile th %ile10th %ile
90th %ile90th %ile90th %ile 10th %ile10th %ile10th %ile Guidance Information for Key Performance Indicators
AWWA Free Water Audit Software v6.0 Dashboard 1 Page 580 of 3451 Table 1 Source: AWWA Water Loss Control Committee Report (2020)1, with naming conventions updated 2020 AWWA Water Audit Method – Water Audit Outputs and Key Performance Indicators: Uses and Limitations Type Indicator Description
Suitable Purposes
Uses and Limitations Principal Users Assessment Bench- Marking Target- Setting Planning Tracking Attribute Apparent Loss Volume Calculated by Free Water Audit Software   Assess loss level Utility, Regulators Apparent Loss Cost Calculated by Free Water Audit Software   Assess cost loss level Utility, Regulators Real Loss Volume Calculated by Free Water Audit Software   Assess loss level Utility, Regulators Real Loss Cost Calculated by Free Water Audit Software   Assess loss cost level Utility, Regulators Unavoidable Annual
Real Loss (UARL)
Calculated by Free Water Audit Software   Reveal theoretical technical low level of leakage
Utility, Regulators
Volume Unit Apparent Losses
(vol/conn/day)
Strong and understandable indicator for multiple users.      Used for performance
tracking and target-setting
Utility, Regulators
Unit Real LossesA(vol/conn/day)
Strong and understandable indicator for multiple users.      Used for performance
tracking and target-setting
Utility, Regulators, Policy Makers
Unit Real LossesB(vol/pipeline length/ day)
Strong and understandable indicator for use by utilities with low connection density.      Data collection and
assessment of systems with “low” connection density
Utility, Regulators, Policy Makers
Unit Total Losses (vol/conn/day) New KPI
Strong and understandable indicator, suitable for high-level performance measurement.   High level indicator for
trending analysis. Not appropriate for target-setting or benchmarking Utilities, Customers
Infrastructure Leakage Index (ILI)
Robust, specialized ratio KPI; can be influenced by pressure and connection density.    Benchmarking after pressure
management is implemented
Utilities
Value Apparent Loss Cost
Rate (value/conn/year) New KPI
Indicators with sufficient technical rigor. Provide the unit financial value of each type of loss, which is useful for planning and assessment of cost efficiency of water loss reduction and control interventions and programs.    Data collection and
assessment on AWWA indicators or contextual parameters to use in conjunction with Loss Cost Rates Utilities, Regulators, Customers
Real Loss Cost Rate (value/conn/year) New KPI
   Utilities,
Regulators, Customers
Validity Data Validity Tier
(DVT)
Strong indicator of water loss audit data quality, if data has been validated. Tier provides guidance on priority areas of activity.     Assess caliber of data inputs
of the water audit
Regulators, Utilities
AWWA Free Water Audit Software v6.0 Dashboard 2 Page 581 of 3451 Appendices
City of Corona
2025 Urban Water Management Plan
Appendix G – SB X7 Standardized Tables

SB X7-7 Table 0: Units of Measure Used in 2020 UWMP*
(select one from the drop down list)
Acre Feet
*The unit of measure must be consistent throughout the UWMP, as reported in Submittal Table 2-3.

NOTES:

NOTES:

SB X7-7 Table 2: Method for 2020 Population Estimate
Method Used to Determine 2020 Population
(may check more than one)

1. Department of Finance (DOF) or
American Community Survey (ACS)

3. DWR Population Tool

4. Other
DWR recommends pre-review

2. Persons-per-Connection Method

2020 170,100
SB X7-7 Table 3: 2020 Service Area Population
2020 Compliance Year Population
NOTES:

Exported
Water *
Change in
Dist. System
Storage*
(+/-)
Indirect
Recycled
Water
This column will
remain blank
until SB X7-7
Table 4-B is
completed.

Water
Delivered for
Agricultural
Use*
Process Water
This column will
remain blank
until SB X7-7
Table 4-D is
completed.
34,244 429 - - 33,815
SB X7-7 Table 4: 2020 Gross Water Use
NOTES:
2020 Volume
Into
Distribution
System
This column will
remain blank until
SB X7-7 Table 4-A
is completed.
2020 Gross Water
Use
2020 Deductions
* Units of measure (AF, MG , or CCF) must remain consistent throughout the UWMP, as reported in SB X7-7 Table 0 and Submittal Table 2-3.

Compliance
Year 2020

Volume Entering
Distribution System 1
Meter Error
Adjustment 2
Optional
(+/-)
Corrected Volume
Entering
Distribution System
18,005 18,005 -
Volume Entering
Distribution System 1
Meter Error
Adjustment 2
Optional
(+/-)
Corrected Volume
Entering
Distribution System
16,239 16,239
This water source is (check one) :

The supplier's own water source
NOTES:

SB X7-7 Table 4-A: 2020 Volume Entering the Distribution System(s), Meter Error Adjustment
Complete one table for each source.

Name of Source Groundwater
Name of Source
SB X7-7 Table 4-A: 2020 Volume Entering the Distribution System(s) Meter Error Adjustment
Complete one table for each source.
1 Units of measure (AF, MG , or CCF) must remain consistent throughout the UWMP, as reported in SB X7-7 Table 0 and Submittal Table 2-3.
2 Meter
Error Adjustment - See guidance in Methodology 1, Step 3 of Methodologies Document NOTES
This water source is (check one) :

The supplier's own water source
A purchased or imported source
WMWD
Compliance Year
2020
A purchased or imported source
1 Units of measure (AF, MG , or CCF) must remain consistent throughout the UWMP, as reported in SB X7-7 Table 0 and Submittal Table 2-3.
2 Meter Error
Adjustment - See guidance in Methodology 1, Step 3 of Methodologies Document Compliance Year
2020

Volume
Discharged
from Reservoir
for
Distribution
System
Delivery
1 Percent
Recycled
Water
Recycled
Water
Delivered to
Treatment
Plant
Transmission/
Treatment
Loss
1 Recycled
Volume
Entering
Distribution
System from
Surface
Reservoir
Augmentation
Recycled
Water
Pumped by
Utility
1,2
Transmission/
Treatment
Losses
1 Recycled
Volume
Entering
Distribution
System from
Groundwater
Recharge
- - - -
1 NOTES: N/A
Units of measure (AF, MG , or CCF) must remain consistent throughout the UWMP, as reported in SB X7-7 Table 0 and Submittal Table 2-3. 2 SB X7-7 Table 4-B: 2020 Indirect Recycled Water Use Deduction Suppliers will provide supplemental sheets to document the calculation for their input into "Recycled Water Pumped by Utility". The volume reported in this cell must be less than total groundwater pumped - See Methodology 1, Step 8, section 2.c. (For use only by agencies that are deducting indirect recycled water) 2020 Surface Reservoir Augmentation
Total Deductible
Volume of Indirect
Recycled Water Entering
the Distribution System
2020 Groundwater Recharge
2020 Compliance
Year

Criteria 1- Industrial water use is equal to or greater than 12% of gross water use.

Complete SB X7-7 Table 4-C.1
Criteria 2 - Industrial water use is equal to or greater than 15 GPCD.

Complete SB X7-7 Table 4-C.2
Criteria 3 - Non-industrial use is equal to or less than 120 GPCD.

Complete SB X7-7 Table 4-C.3
Criteria 4 - Disadvantaged Community.

Complete SB x7-7 Table 4-C.4
SB X7-7 Table 4-C: 2020 Process Water Deduction Eligibility (For use only by agencies that are deducting process water) Choose Only One NOTES: N/A
Data from this table will not be entered into WUEdata.

Instead, the entire table will be uploaded to WUEdata as a separate upload in Excel format.

2020 Gross
Water Use
Without
Process
Water
Deduction
2020 Industrial
Water Use
Percent
Industrial
Water
Eligible
for
Exclusion
Y/N
33,815 0% NO
Data from this table will not be entered into WUEdata.

Instead, the entire table will be uploaded to WUEdata as a separate upload in Excel format.

NOTES: N/A
SB X7-7 Table 4-C.1: 2020 Process Water Deduction Eligibility (For use only by agencies that are deducting process water using Criteria 1) Criteria 1
Industrial water use is equal to or greater than 12% of gross water use 2020 Compliance Year

2020 Industrial
Water Use
2020 Population
2020
Industrial
GPCD
Eligible for
Exclusion Y/N
170,100 - NO
Data from this table will not be entered into WUEdata.

Instead, the entire table will be uploaded to WUEdata as a separate upload in Excel format.

NOTES: N/A
SB X7-7 Table 4-C.2: 2020 Process Water Deduction Eligibility (For use only by agencies that are deducting process water using Criteria 2) Criteria 2
Industrial water use is equal to or greater than 15 GPCD 2020 Compliance
Year

2020 Gross
Water Use
Without
Process Water
Deduction
Fm SB X7-7
Table 4
2020
Industrial
Water Use
2020 Nonindustrial
Water Use
2020
Population
Fm SB X7-7
Table 3
Non-Industrial
GPCD
Eligible for
Exclusion
Y/N
33,815 33,815 170,100 177 NO
NOTES:

Data from this table will not be entered into WUEdata.

Instead, the entire table will be uploaded to WUEdata as a separate upload in Excel format.

Criteria 3
Non-industrial use is equal to or less than 120 GPCD
SB X7-7 Table 4-C.3: 2020 Process Water Deduction Eligibility (For use only by agencies that are deducting process water using Criteria 3) 2020 Compliance
Year

Service Area
Median Household
Income
Percentage of
Statewide
Average
Eligible for
Exclusion? Y/N
2020 $75,235 $86,790 115% NO
NOTES
California Median
Household Income*
*California median household income 2015 -2019 as reported in US Census Bureau QuickFacts.

Data from this table will not be entered into WUEdata.

Instead, the entire table will be uploaded to WUEdata as a separate upload in Excel format.

SB X7-7 Table 4-C.4: 2020 Process Water Deduction Eligibility (For use only by agencies that are deducting process water using Criteria 4) Criteria 4
Disadvantaged Community. A “Disadvantaged Community” (DAC) is a community with a median household income less than 80 percent of the statewide average.

SELECT ONE
"Disadvantaged Community" status was determined using one of the methods listed below:

If using the IRWM DAC Mapping Tool, include a screen shot from the tool showing that the service area is considered a DAC.

1. IRWM DAC Mapping tool https://gis.water.ca.gov/app/dacs/

2. 2020 Median Income

Industrial
Customer's Total
Water Use *
Total Volume
Provided by
Supplier*
% of Water
Provided by
Supplier
Customer's Total
Process Water
Use*
Volume of Process
Water Eligible for
Exclusion for this
Customer
-
Compliance Year
2020
NOTES: N/A
* Units of measure (AF, MG , or CCF) must remain consistent throughout the UWMP, as reported in SB X7-7 Table 0 and Submittal Table 2-3.

Data from these tables will not be entered into WUEdata. Instead, the entire tables will be uploaded to WUEdata as a separate upload in Excel format.

Name of Industrial Customer Enter Name of Industrial Customer 1 SB X7-7 Table 4-D: 2020 Process Water Deduction - Volume Complete a separate table for each industrial customer with a process water exclusion This table(s) is only for Suppliers that deduct process water from their 2020 gross water use.

2020 Gross Water
Fm SB X7-7 Table 4
2020 Population Fm
SB X7-7 Table 3
2020 GPCD
170,100 33,815 177
SB X7-7 Table 5: 2020 Gallons Per Capita Per Day
(GPCD)
NOTES:

Extraordinary
Events
1 Weather
Normalization
1 Economic
Adjustment
1 177 - - - - 177 213 YES
1 NOTES:

All values are reported in GPCD
2 2020 Confirmed Target GPCD is taken from the Supplier's SB X7-7 Verification Form Table SB X7-7, 7-F.

SB X7-7 Table 9: 2020 Compliance
Optional Adjustments to 2020 GPCD
Did Supplier
Achieve
Targeted
Reduction for
2020?
Actual 2020
GPCD
1 2020 Confirmed
Target GPCD
1, 2 TOTAL
Adjustments
1 Adjusted 2020
GPCD
1 (Adjusted if
applicable)
Enter "0" if Adjustment Not Used

Appendices
City of Corona
2025 Urban Water Management Plan
Appendix H – Energy Intensity Tables

Retail Potable
Deliveries
1/1/2025
12/31/2025
No
Units for
Water
Volume
Extract and
Divert
Place
into
Storage
Conveyance Treatment Distribution Total Utility
See DWR NOTES Hydropower Net Utility
AF 16,254 5,475 29,589 29,589 29,589
N/A 12,427,020 6,735,400 23,185,661 42,348,081 42,348,081 N/A - 3,775 - 2,346 2,405 4,392 - 4,392
Quantity of Self-Generated Renewable Energy
0 kWh
Data Quality (Estimate, Metered Data, Combination of Estimates and Metered Data) Metered Data
Data Quality Narrative:

Narrative:

Optional Submittal Table O-1A: Recommended Energy Reporting - SINGLE DELIVERY PRODUCT - WATER SUPPLY PROCESS APPROACH Water Delivery Product
drop down list
(If delivering more than one type of product recommend using Table O1C) Only for Water Delivery Products Under the Urban Water Supplier's Operational Control Start Date of Reporting Period
Water Management Process Non-Consequential Hydropower
(if applicable) End Date of Reporting Period
Is upstream embedded energy included in the values reported? Volume of Water Entering Process
Energy Consumed (kWh)
Energy Intensity (kWh/vol. converted to MG)
DWR NOTES: Total Utility:The volume of water entered in the “Total Utility” column should equal the volume of water entering the distribution system (excluding recycled water); in most cases, this is the total volume calculated in UWMP Table 4-1: 2025 Actual Total Uses for Potable and Non-Potable Water. Note if recycled water is included in your Submittal Table 4-1, you must exclude it from your volume in this table.

All energy and water volume data are metered. Often, a single energy meter records all energy consumption at a site or facility, making it impossible to distinguish the energy consumed by individual processes when multiple processes are present at one site.

The following sources of potable supply have similar operational control: imported untreated surface water, imported treated surface water, groundwater, and groundwater with high TDS.

Delivery of imported untreated surface water from WMWD undergoes conveyance (source water pumped from wholesaler's transmission pipeline to the City's surface water treatment facilities), treatment (conventional surface water treatment, as well as energy consumed at the facilities for security, lighting, SCADA, and domestic uses at onsite buildings), and distribution (gravity flow to storage facilities where it is pumped as necessary to the various distribution system pressure zones).

Delivery of imported treated surface water from WMWD undergoes conveyance (pressure reduction) and distribution (pumped as necessary to various distribution system pressure zones).

Delivery of low TDS groundwater from the Temescal Basin undergoes extraction (pumped to nearby storage facilities or diverted to blending facilities) and distribution (pumped as necessary to various distribution system pressure zones).

Delivery of groundwater with high TDS from the Temescal Basin undergoes extraction (pumped to Temescal Desalter), treatment (reverse osmosis and blending), and distribution (pumped as necessary to various distribution system pressure zones).

NOTES:

Start Date of Reporting Period 1/1/2025
End Date of Reporting Period 12/31/2025
Is upstream embedded energy in the values reported?
Units of Measure for Water AF Collection /
Conveyance
Treatment Discharge /
Distribution Total
7,621 1,198 7,367 16186
628,743 13,804,533 0 14433276
253.2 35362.9 0.0 2736.6
4,554 0 3,910 8464
3,512,937 0 0 3512937
2367.3 0.0 0.0 1273.7
Quantity of Self-Generated Renewable Energy related to recycled water and wastewater operations
kWh
Data Quality (drop down)
Data Quality Narrative:

Narrative:

NOTES:

Volume of Wastewater Entering Process (volume units selected above) Wastewater Energy Consumed (kWh)
Volume of Recycled Water Entering Process (volume units selected above) Recycled Water Energy Consumed (kWh)
Wastewater Energy Intensity (kWh/volume converted to MG) Recycled Water Energy Intensity (kWh/volume converted to MG) Optional Submittal Table O-2: Recommended Energy Reporting - WASTEWATER AND RECYCLED WATER Only for Water Delivery Products Under the Urban Water
Supplier's Operational Control
Water Management Process
All energy and water volume data are metered. Natural gas is used at several facilities.

Energy use for reclaimed water consists of conveyance and distribution. For purposes of this table, these processes have been aggregated. Energy use for wastewater consists of collection, primary/secondary/tertiary treatment, dewatering/drying of biomass, and diversion/disposal of effluent. For purposes of this table, these processes have also been aggregated.

Appendices
City of Corona
2025 Urban Water Management Plan
Appendix I – DWR Bulletin 118

Hydrologic Region South Coast
Upper Santa Ana Valley Groundwater Basin
California’s Groundwater
Bulletin 118
Upper Santa Ana Valley Groundwater Basin,
Temescal Subbasin
• Groundwater Basin Number: 8-2.09
• County: Riverside
• Surface Area: 23,500 acres (37 square miles)
Basin Boundaries and Hydrology
The Temescal Subbasin underlies the southwest part of upper Santa Ana Valley. On the north, the subbasin is bounded by the Chino Subbasin, marked by the Santa Ana River and a set of low hills of crystalline rock near Norco. The eastern part of the subbasin is bounded by nonwater-bearing crystalline rocks of the El Sobrante de San Jacinto and La Sierra Hills. The subbasin is bounded on the west by the Santa Ana Mountains and the south by the Elsinore Groundwater Basin at a constriction in the alluvium of Temescal Wash. Average annual precipitation ranges from 14 to 16 inches per year.

Hydrogeologic Information
Water Bearing Formations
The water-bearing materials are dominantly composed of Holocene age alluvium deposited by streams draining the northeast slopes of the Santa Ana Mountains. The Santa Ana River has from time to time contributed deposits through the Arlington Gap along the northern margin of the subbasin (DWR 1934).

The specific yield varies from about 6 percent along the southwestern and southern margins of the subbasin to about 13 percent beneath the Santa Ana River and more than 14 percent beneath Temescal Wash near Corona (DWR 1934).

Restrictive Structures
The Elsinore fault zone lies along the western boundary of the subbasin, and the Chino fault zone crosses the northwestern tip of the subbasin. These fault zones are possible groundwater barriers (SBVWCD 2000).

Recharge Areas
Dominant recharge to the groundwater reservoir is from percolation of precipitation on the valley floor and infiltration of stream flow within tributaries exiting the surrounding mountains and hills.

Groundwater Level Trends
Groundwater flows toward the center of the subbasin and then northeast toward the Santa Ana River (SBVWCD 2000).

Groundwater Storage
Groundwater Storage Capacity. Unknown.

Groundwater in Storage. Unknown.

Last update 1/20/06 Page 601 of 3451
Groundwater Budget (Type C)
No information is available.

Groundwater Quality
Characterization. Water within the subbasin is predominantly calciumsodium bicarbonate and has an average TDS content of 790 mg/L (SBVWCD 2000). Water from 20 public supply wells in the subbasin has an average TDS content of 753 mg/L and a range or 373 to 950 mg/L.

Impairments.

Water Quality in Public Supply Wells
Constituent Group1 Number of
wells sampled2 Number of wells with a concentration above an MCL3 Inorganics – Primary 20 2
Radiological 17 1
Nitrates 20 13
Pesticides 17 0
VOCs and SVOCs 17 0
Inorganics – Secondary 20 2
1 A description of each member in the constituent groups and a generalized discussion of the relevance of these groups are included in California’s Groundwater – Bulletin 118 by DWR (2003). 2
Represents distinct number of wells sampled as required under DHS Title 22 program from 1994 through 2000.
3 Each well reported with a concentration above an MCL was confirmed with a second detection above an MCL. This information is intended as an indicator of the types of activities that cause contamination in a given basin. It represents the water quality at the sample location. It does not indicate the water quality delivered to the consumer. More detailed drinking water quality information can be obtained from the local water purveyor and its annual Consumer Confidence Report.

Well Characteristics
Well yields (gal/min)
Municipal/Irrigation Range: Average:

Total depths (ft)
Domestic Range: Average:

Municipal/Irrigation Range: Average:

Active Monitoring Data
Agency Parameter Number of wells
/measurement frequency
USGS Groundwater levels 2
USGS Miscellaneous
water quality
2 Department of
Health Services and
cooperators
Title 22 water
quality
20 California’s Groundwater
Bulletin 118
Last update 1/20/06

Hydrologic Region South Coast
Upper Santa Ana Valley Groundwater Basin

Basin Management
Groundwater management: The City of Corona is developing a groundwater management plan for the
Temescal Basin.

Water agencies
Public
Private
References Cited
California Department of Water Resources (DWR). 1934. South Coastal Basin Investigation.

San Bernardino Valley Water Conservation District (SBVWCD). 2000. Engineering Investigation of the Bunker Hill Basin 1999-2000.

Additional References
Wildermuth Environmental, Inc. (Wildermuth). 2000. TIN/TDS Study - Phase 2A of the Santa Ana Watershed; Final Technical Memorandum. San Clemente, California, July 2000.

Errata
Updated groundwater management information and added hotlinks to applicable websites. (1/20/06)
Last update 1/20/06
Hydrologic Region South Coast California’s Groundwater
Upper Santa Ana Valley Groundwater Basin Bulletin 118

8-004.02 ELSINORE - BEDFORD-COLDWATER
Basin Boundaries
Summary
The Bedford-Coldwater groundwater subbasin is located in western Riverside County. The basin is separated from the Temescal subbasin to the northwest by a groundwater divide near Bedford Wash. The Bedford-Coldwater subbasin is bound on the east and west by consolidated rocks of Estelle Mountain and the Santa Ana Mountains, respectively. The southern boundary adjoins the Elsinore Valley subbasin and follows a jurisdictional boundary separating the two subbasins. The boundary is defined by 19 segments detailed in the descriptions below.

Segment Descriptions
Segment
Label
Segment
Type
Description Ref
1-2 E
Alluvial Begins from point (1) and follows the contact of Quaternary alluvium with Cretaceous metamorphic rocks of the Santa Ana Mountains to point (2). {a}
2-3 I
Groundwater
Divide
Continues from point (2) and follows a groundwater divide to point (3). {b} 3-4 E
Alluvial Continues from point (3) and generally follows the contact of Quaternary alluvium with early Pleistocene alluvial fan deposits, Paleocene Silverado Formation, Cretaceous volcanic rocks, various Cretaceous plutonic rocks, and Triassic metasedimentary and metavolcanic rocks to point (4). {c}
4-5 I
Management
Area
Continues from point (4) and follows the jurisdictional boundary separating the Temescal Valley Water District from the Elsinore Valley Municipal Water District to point (5).
{d}
5-6 E
Alluvial Continues from point (5) and follows the contact of Quaternary alluvium with Cretaceous Estelle Mountain volcanics to point (6). {c}
6-7 I
Management
Area
Continues from point (6) and follows the jurisdictional boundary separating the Temescal Valley Water District from the Elsinore Valley Municipal Water District to point (7).
{d}
7-1 E
Alluvial Continues from point (7) and follows the contact of Quaternary alluvium with Jurassic Bedford Canyon Formation and various Cretaceous plutonic rocks of the Santa Ana Mountains and ends at point (1). {c}
8-8 E
Alluvial Island within the basin boundary: begins from point (8) and follows the contact of Quaternary alluvium or artificial fill with Paleocene Silverado Formation, Cretaceous plutonic rocks, and Triassic metasedimentary and metavolcanic rocks to point (8).
{c}
9-9 E
Alluvial Island within the basin boundary: begins from point (9) and follows the contact of Quaternary alluvium with Tertiary Topanga group of marine sediments and Tertiary Vaqueros, Sespe, and Silverado Formations to point (9).
{c}
10-10 E
Alluvial Island within the basin boundary: begins from point (10) and follows the {c}

contact of Pleistocene alluvium with Paleocene Silverado Formation to point (10).
11-11 E
Alluvial Island within the basin boundary: begins from point (11) and follows the contact of Quaternary alluvium or artificial fill with Paleocene Silverado Formation to point (11).
{c}
12-12 E
Alluvial Island within the basin boundary: begins from point (12) and follows the contact of Quaternary alluvium with Paleocene Silverado Formation to point (12).
{c}
13-13 E
Alluvial Island within the basin boundary: begins from point (13) and follows the contact of Quaternary alluvium with Paleocene Silverado Formation and Triassic metasedimentary and metavolcanic rocks to point (13). {a}
14-14 E
Alluvial Island within the basin boundary: begins from point (14) and follows the contact of Quaternary alluvium with Cretaceous Estelle Mountain volcanic rocks and Triassic metasedimentary and metavolcanic rocks to point (14). {c}
15-15 E
Alluvial Island within the basin boundary: begins from point (15) and follows the contact of Quaternary alluvium with Cretaceous Estelle Mountain volcanic rocks and Triassic metasedimentary and metavolcanic rocks to point (15). {c}
16-16 E
Alluvial Island within the basin boundary: begins from point (16) and follows the contact of Quaternary alluvium with Tertiary Topanga group of marine sediments and Tertiary Vaqueros and Sespe Formations to point (16). {c}
17-17 E
Alluvial Island within the basin boundary: begins from point (17) and follows the contact of Quaternary alluvium with Paleocene Silverado Formation to point (17).
{c}
18-18 E
Alluvial Island within the basin boundary: begins from point (18) and follows the contact of Quaternary alluvium with Paleocene Silverado Formation to point (18).
{c}
19-19 E
Alluvial Island within the basin boundary: begins from point (19) and follows the contact of Quaternary alluvium or landslide deposits with Tertiary Vaqueros and Sespe Formations to point (19).
{c}

Significant Coordinates
Point Latitude Longitude
1 33.779617348 -117.56234861
2 33.800555285 -117.542432974
3 33.828576167 -117.512654588
4 33.758400757 -117.450700384
5 33.757619077 -117.450701841
6 33.749834798 -117.450456486
7 33.742171922 -117.45081152
8 33.813657348 -117.503401425
9 33.80298986 -117.527206161
10 33.817083315 -117.502061053
11 33.818382037 -117.510322081
12 33.776853859 -117.483852061
13 33.780899405 -117.479699934
14 33.773035679 -117.471238502
15 33.771565887 -117.464605454
16 33.754488258 -117.457271385
17 33.806376258 -117.522498483
18 33.805755342 -117.511387199
19 33.798413174 -117.523900357

Map
8-004.02 ELSINORE - BEDFORD-COLDWATER
https://sgma.water.ca.gov/webgis/?appid=160718113212&subbasinid=8-004.02 References
Ref Citation Pub
Date
Global
ID
{a} United States Geological Survey (USGS), Geologic map of the San Bernardino and Santa Ana 30' x 60' quadrangles, California, 1:100,000, D.M. Morton and F.K.

Miller.URL: http://pubs.usgs.gov/of/2006/1217/
2006 69
{b} BBMRS varies 45
{c} California Geological Survey (CGS), Geologic Compilation of Quaternary Surficial Deposits in Southern California, T.L. Bedrossian, P. Roffers, C.A. Hayhurst, J.T.

Lancaster, and W.R. Short.URL:
2012 50
http://www.conservation.ca.gov/cgs/fwgp/Pages/sr217.aspx {d} California Department of Water Resources (DWR), Water Agencies Dataset.URL: 2016 48 https://gis.water.ca.gov/app/bbat/
Footnotes
I: Internal
E: External

Appendices
City of Corona
2025 Urban Water Management Plan
Appendix J – Corona 2008 Groundwater Management Plan

 


  



















Final
AB3030 Groundwater Management Plan
Prepared for:

City of Corona
Department of Water and Power
755 Corporation Yard Way
Corona, CA 92880
Prepared by:

Todd Engineers
2490 Mariner Square Loop, Suite 215
Alameda, CA 94501-1080
AKM Consulting Engineers
553 Wald
Irvine, CA 92618
June 2008

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

1.1. GWMP Plan Goals and Objectives ............................................................ 1

1.2. Scope of Work ............................................................................................ 1

1.3. GWMP Organization and Preparation ........................................................ 2

1.4. Public Outreach .......................................................................................... 3

1.4.1. Notice of Intent to Prepare an AB3030 GWMP ......................................... 3

1.4.2. Neighboring Agencies and Service Areas .................................................. 3

1.4.3. Public Meetings .......................................................................................... 4

1.4.4. Meetings with Neighboring Agencies ........................................................ 4

1.5. Environmental Review ............................................................................... 4

2. Data Compilation and Management .......................................................... 5

2.1. Study Area .................................................................................................. 5

2.1.1. Subbasin Boundaries .................................................................................. 6

2.1.2. Contributing Watersheds ............................................................................ 7

2.2. Study Period ............................................................................................... 7

2.3. Data Types and Sources ............................................................................. 8

2.4. Hydrologic Data ......................................................................................... 9

2.4.1. Climate Data ............................................................................................... 9

2.4.2. Streamflow ............................................................................................... 10

2.4.3. Reservoir Storage ..................................................................................... 10

2.5. Water System Data ................................................................................... 10

2.5.1. Pumping Data ........................................................................................... 10

2.5.2. Imported Water Data ................................................................................ 11

2.5.3. Water Demand .......................................................................................... 11

2.5.4. Wastewater Treatment Plant (WWTP) Data ............................................ 11

2.6. Groundwater Data .................................................................................... 12

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2.6.1. Basin and Watershed Boundaries ............................................................. 12

2.6.2. Well Data .................................................................................................. 13

2.6.3. Water Level Data ...................................................................................... 14

2.6.4. Water Quality Data ................................................................................... 14

2.6.5. Regulated Facilities .................................................................................. 14

2.6.6. Land Use Data .......................................................................................... 15

2.7. Geologic Data ........................................................................................... 16

2.7.1. Geology Maps .......................................................................................... 16

2.7.2. Lithologic Data ......................................................................................... 16

2.7.3. Soils Data ................................................................................................. 16

2.8. GIS Files and Layers ................................................................................ 16

2.9. Data Management System (DMS) ............................................................ 16

3. State of the Groundwater Basins ............................................................. 19

3.1. Land Use ................................................................................................... 19

3.2. Physical Setting ........................................................................................ 20

3.2.1. Topography .............................................................................................. 20

3.2.2. Precipitation and Evapotranspiration (ET) ............................................... 21

3.2.3. Streamflow ............................................................................................... 21

3.2.4. Geology .................................................................................................... 23

3.3. Aquifers and Hydrostratigraphy ............................................................... 24

3.3.1. Channel Aquifer ....................................................................................... 25

3.3.2. Alluvial Fan Aquifers ............................................................................... 26

3.3.3. Sandstone Aquifer .................................................................................... 27

3.4. Water Supply ............................................................................................ 27

3.4.1. Pumping .................................................................................................... 27

3.4.2. Imported Water ......................................................................................... 30

3.4.3. Wastewater ............................................................................................... 31

3.5. Groundwater ............................................................................................. 32

3.5.1. Water Levels ............................................................................................. 32

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3.5.2. Groundwater Flow Directions .................................................................. 34

3.5.3. Groundwater Quality ................................................................................ 36

3.6. Water Balance .......................................................................................... 40

3.6.1. Approach .................................................................................................. 41

3.6.2. Temescal Subbasin Water Balance........................................................... 42

3.6.3. Coldwater Subbasin Water Balance ......................................................... 54

3.6.4. Water Balance Discussion ........................................................................ 59

4. City of Corona Water Demand and Supply ............................................. 61

4.1. Current and Future Demand ..................................................................... 61

4.2. Water Conservation and Demand Management ....................................... 63

4.3. Supply ....................................................................................................... 64

4.3.1. Groundwater Basins ................................................................................. 66

4.3.2. Imported Water ......................................................................................... 67

4.3.3. Recycled Water ........................................................................................ 69

5. Basin Management Objectives ................................................................ 70

5.1. Manage Groundwater Basin in a Sustainable Manner ............................. 70

5.2. Prevent Substantial Water Level Declines in Channel Aquifer ................ 70

5.3. Protect Groundwater Quality in Unconfined Aquifers ............................. 71

5.4. Maintain Required Outflow at Prado Dam ............................................... 71

5.5. Monitor Groundwater Levels, Quality, and Storage ................................ 71

6. Basin Management Strategies ................................................................. 72

6.1. Identification of Management Strategies .................................................. 72

6.1.1. New and Replacement Water Supply Wells and Wellhead Treatment .................................................................................................. 73

6.1.2. Groundwater Treatment Process Improvements ...................................... 75

6.1.3. Groundwater Monitoring Program ........................................................... 75

6.1.4. Enhanced Groundwater Recharge ............................................................ 76

6.1.5. Expanded Use of Recycled Water ............................................................ 78

6.1.6. Use of Imported Water ............................................................................. 80

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6.1.7. Wastewater Pond Maintenance ................................................................ 81

6.1.8. Coordination with Regulatory Agencies .................................................. 81

6.1.9. Water Conservation and Demand Management ....................................... 82

6.2. Evaluation of Management Strategies using AB3030 Checklist .............. 83

6.2.1. Control of Saline Water Intrusion ............................................................ 83

6.2.2. Identification and Management of Wellhead Protection and Recharge Areas ......................................................................................................... 83

6.2.3. Regulation of the Migration of Contaminated Groundwater .................... 84

6.2.4. Administration of a Well Abandonment and Well Destruction Program . 84

6.2.5. Mitigation of Overdraft Conditions .......................................................... 84

6.2.6. Replenishment of Groundwater Extracted by Water Producers ............... 85

6.2.7. Monitoring of Groundwater Levels and Storage ...................................... 85

6.2.8. Facilitating Conjunctive Use Operations .................................................. 85

6.2.9. Identification of Well Construction Policies ............................................ 85

6.2.10. Construction and Operation of Groundwater Contamination Cleanup, Recharge, Storage, Conservation, Water Recycling, and Extraction Projects ..................................................................................................... 86

6.2.11. Development of Relationships with State and Federal Regulatory Agencies ................................................................................................... 86

6.2.12. Review of Land Use Plans and Coordination with Land Use Planning Agencies to Assess Activities which Create a Reasonable Risk of Groundwater Contamination .................................................................... 86

6.3. Evaluation of Management Strategies ...................................................... 86

6.3.1. Baseline Evaluation .................................................................................. 87

6.3.2. Scenario 1 - Pumping Redistribution ....................................................... 88

6.3.3. Scenarios 2 and 3 - Enhanced Recharge at Detention Basins .................. 89

6.3.4. Scenarios 4a and 4b - Upgradient Injection Wells in Channel Aquifer .... 92

6.3.5. Recycled Water Recharge ........................................................................ 94

6.4. Recommended Management Strategies .................................................... 95

7. Implementation Plan ................................................................................. 96

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7.1. Prioritization of Strategies ........................................................................ 96

7.2. Implementation Plan and Schedule .......................................................... 96

7.3. Annual Re-evaluation of Management Performance ............................... 98

8. References ................................................................................................. 99

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1. Introduction
The City of Corona relies on three groundwater subbasins within their water service area for a portion of their water supply. In order to more actively manage this limited resource, the City and its technical consultants have prepared this Groundwater Management Plan (GWMP).

The plan follows guidelines set forth in Assembly Bill (AB) 3030, which was promulgated in 1992 and allows local agencies to prepare and adopt GWMPs (California Water Code Sections 10750 through 10756). The bill was amended in 2002 by Senate Bill (SB) 1938, providing additional GWMP requirements. Such a plan allows the City to address issues of groundwater recharge and storage, critical components for effective management of the local subbasins and the City’s water supply. This GWMP will be considered by the City for adoption on June 18, 2008 in accordance with AB3030 timelines (the press release for the public hearing is included in Appendix A).

1.1. GWMP Plan Goals and Objectives
The Goals of the GWMP include:
• Operate the groundwater basin in a sustainable manner for beneficial uses • Increase the reliability of water supply for basin users To support these goals, the City has determined the need to better understand the hydrogeology and groundwater conditions of the underlying basins and, based on this understanding, develop appropriate management objectives and strategies to achieve these goals.

The Plan area covers three groundwater subbasins within the City’s water service area and sphere of influence. The City has conducted groundwater production and management activities in these subbasins for more than 40 years. These three subbasins, Temescal, Coldwater, and Bedford, are located in western Riverside County in the Santa Ana River Watershed as shown on Figures 1 and 2 (all figures are at the end of the text in this document).

1.2. Scope of Work
The City, along with input from Todd Engineers and AKM Consulting Engineers, developed a scope of work for the preparation of the GWMP including a series of nine tasks as listed below:
• Provide Public Outreach
• Identify Study Area and Compile Data
• Develop Data Management System

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• Construct a Groundwater Model
• Develop Groundwater Basin Management Objectives (BMOs) • Develop Groundwater Management Strategies
• Evaluate Management Alternatives
• Prepare a GWMP
The City took the lead on the public outreach process, described in more detail in the following section. The Study Area is defined as the groundwater subbasins underlying the City’s water service area and covers approximately 30,000 acres (47 square miles) (Figure 3). To support the development of an AB3030 GWMP, relevant hydrologic and hydrogeologic data for the Study Area, as well as the contributing watersheds, were compiled and analyzed. The analysis provides for an historical assessment of available data as well as more detailed analysis over a 15- year Study Period.

Collectively, these analyses are used to describe the “state of the basins” with respect to groundwater use, water levels, quality, and storage. Based on this assessment, basin management objectives and management strategies to achieve those objectives were developed. The management strategies were further evaluated by the development, calibration, and application of a numerical groundwater flow model. The GWMP also includes a schedule for implementation of the management strategies.

1.3. GWMP Organization and Preparation
The organization of this GWMP generally follows the tasks described above. Tables are incorporated into the text and numbered within each chapter of the document. All figures are provided at the end of the text in a separate section to allow referencing throughout the text and to prevent duplication of figures. This introductory chapter provides the background and context for the GWMP. Chapter 2 describes the data compilation process for the analyses conducted. Chapter 3 describes the hydrogeologic assessment of the state of the groundwater basins. A brief description of the City’s current and projected water demand, along with water sources, is included in Chapter 4 to provide context for the City’s future reliance on groundwater as one of the sources of water supply. Basin Management Objectives and strategies to meet those objectives are provided in Chapters 5 and 6, respectively. Chapter 7 provides an implementation schedule for the GWMP. References are summarized in Chapter 8. Appendix A contains documentation of the stakeholder process. Appendix B summarizes the City’s current monitoring program and makes recommendations for future improvement. Appendix C describes the development of a numerical groundwater model to assist with the evaluation of key management strategies. Appendix D contains a feasibility study for recycled water recharge in the Bedford

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The development of the GWMP was a collective effort by the City and its technical consultants. The City provided key data and led the public outreach program. Todd Engineers led the data compilation and hydrogeologic assessment of the groundwater subbasins. Todd Engineers also constructed, calibrated, and applied a numerical groundwater model of the Temescal Subbasin for the analysis of selected groundwater management strategies. AKM assisted with details on the City’s water supply and wastewater systems, future water demand, and the identification of key management strategies.

1.4. Public Outreach
In order to encourage public participation and keep local agencies informed, the City conducted a public outreach program associated with the GWMP. The City developed a stakeholder list to specifically invite interested parties to public meetings and inform them on plan preparation. Public notices, a Stakeholder List, and an adopted resolution to prepare the GWMP are provided in Appendix A. Public outreach activities are summarized in the following sections.

1.4.1. Notice of Intent to Prepare an AB3030 GWMP
On June 6, 2006, the City notified the public that a public meeting was scheduled to consider whether the City should prepare a GWMP. In the public notice, provided in Appendix A, the City invited all landowners and interested parties to attend the hearing and express their interest in the GWMP process. The City also made available advance copies of the resolution that was being considered. The notice described how interested parties could participate in the GWMP development by either attending the hearing or submitting a written request to the City.

At the public hearing on June 21, 2006, the City invited the public to comment on the GWMP process and pending resolution. No comments were made, and the Resolution of Intent to Prepare a Groundwater Management Plan was adopted. A copy of the signed resolution is provided in Appendix A.

1.4.2. Neighboring Agencies and Service Areas
Figure 4 shows the service areas of agencies in the region that provide water supply to the area. The City shares the three groundwater subbasins with the City of Norco, Home Gardens County Water District, Lee Lake Water District (LLWD), and Elsinore Valley Municipal Water District (EVMWD). LLWD is participating in the GWMP and is proposing a groundwater recharge project with recycled water in the Bedford Subbasin. This project is included as a groundwater management strategy in this GWMP and is evaluated separately in Appendix D.

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1.4.3. Public Meetings
In addition to the public hearings held in accordance with the GWMP process, two public workshops were conducted on December 11, 2007 and May 20, 2008. At the December workshop, the assessment of the groundwater basin was presented along with preliminary basin management objectives (BMOs) and potential management strategies to achieve those objectives.

Representatives from LLWD, Western Municipal Water District (WMWD), Orange County Water District (OCWD), EVMWD, Chandler’s Sand and Gravel, Riverside County Waste Management Department (RCWMD), and other parties attended the workshop. GWMP information and a copy of the technical presentation were posted on the City’s website prior to the meeting.

In the May workshop, the Draft GWMP was reviewed including the final BMOs, evaluation of the management strategies, and the implementation schedule. Representatives of WMWD, EVMWD, Santa Ana Watershed Protection Agency (SAWPA), Chandler’s Sand and Gravel, Riverside County Flood Control and Water Conservation District (RFCWCD) and Inland Empire Waterkeeper attended the workshop. The Draft GWMP was posted on the City’s website prior to the meeting. Written comments on the Draft GWMP were provided by WMWD, RFCWCD, RCWMD, and Inland Empire Waterkeeper. Those comments have been incorporated into this GWMP, or in some cases, marked for further review during the EIR process.

1.4.4. Meetings with Neighboring Agencies
Two informal meetings were also held with neighboring agencies on the GWMP process.

On January 22, 2008, City consultants provided an update of the GWMP development to the Lee Lake Water District (LLWD) Board of Directors at their request. The City and consultants also met with consultants of the Chino Basin Watermaster at their request on March 18, 2008 to discuss the GWMP progress and mutual interests with respect to data sharing and groundwater modeling.

1.5. Environmental Review
In compliance with the California Environmental Quality Act, the City has embarked on an environmental review of the GWMP. The process will evaluate the strategies included in the adopted GWMP in a Programmatic Environmental Impact Report (PEIR). The City has already retained the services of Environmental Science Associates (ESA) to prepare the PEIR, which will commence after the GWMP has been adopted. Preparation of the PEIR will involve public notification and hearings on potential environmental impacts of the GWMP. The City may decide to update or modify components of the GWMP in the future based on the environmental review process.

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2. Data Compilation and Management
To support the development of an AB3030 GWMP for the City, relevant hydrologic and hydrogeologic data for the groundwater basins and contributing watersheds have been compiled.

A Study Area and Study Period were defined early in the process to guide the data collection effort. The data collection process occurred mainly in 2006 and resulted in relatively complete data sets through 2004. In addition, data collected since 2006 are incorporated as noted throughout the GWMP. The City’s water production and purchases are updated through the end of Calendar Year 2007 in Chapter 4. Other historical data were collected when available, but a focused effort was made to compile data covering an approximate 20-year period dating back to the mid-1980s.

A Data Management System (DMS) was designed to organize available data, support technical analyses, and identify data gaps. This system includes a relational database in Access format with individual tables for each data type. A project Geographical Information System (GIS) has also been maintained as a repository for regionally-available GIS files and for viewing and analyzing spatial data. The database and GIS were also used to facilitate the construction of a numerical model to assist in the evaluation of management strategies. Collectively, the GIS and project database provide a framework that will allow additional data to be incorporated and analyzed in the future. The Study Area, Study Period, and data collection efforts are described in the following sections.

2.1. Study Area
A Study Area for the Groundwater Management Plan was defined by the groundwater subbasins of interest, the contributing watersheds, and portions of the adjoining groundwater basins (Figure 3). The Study Area is larger than the groundwater subbasins to be managed in order to incorporate inflows from other groundwater basins and evaluate the subbasins of interest in a regional context.

Subbasin nomenclature and boundaries follow those included in the California Department of Water Resources (DWR) document, California’s Groundwater, commonly referred to as DWR Bulletin 118 (DWR, 2003). Portions of Bulletin 118, including descriptions of individual groundwater basins, are updated periodically by DWR. The Study Area subbasins were updated on February 27, 2004 and those descriptions are used in this document (DWR February 27, 2004a; 2004b; 2004c). Subbasins and contributing watershed areas, as determined through GIS, are summarized in the table below.

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Groundwater Basins and Watersheds
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The Temescal Subbasin is a recognized subbasin in Bulletin 118. The Elsinore Groundwater Basin, the adjoining basin to the southeast, is not formally divided into subbasins in Bulletin 118. However, two areas within the northern portion of the Elsinore Basin, Coldwater and Bedford, have been designated as subbasins in past investigations (DWR, 1959). Because these subbasins can be readily defined as distinct from the remaining subbasins to the south, they are included as separate subbasins in the Study Area for the purposes of this GWMP.

2.1.1. Subbasin Boundaries
The Temescal Subbasin as defined by DWR is bounded on the west by the Santa Ana Mountains and the east by low-lying El Sobrante de San Jacinto and La Sierra hills. The subbasin is connected to three adjacent groundwater basins. The boundary with the Chino Subbasin (DWR Basin No. 8-2.01) to the north is generally marked by the Santa Ana River and a series of lowlying hills in the Norco area (Figure 3). Groundwater flows into the subbasin from the RiversideArlington Subbasin (DWR Basin No. 8-2.03) through the Arlington Gap, a restriction in the southwestern arm of the Riverside-Arlington Subbasin (Figure 3). The southern boundary of Temescal Subbasin is located at a constriction of the alluvium along Temescal Wash at Bedford Canyon where it connects with the Bedford Subbasin of the Elsinore Groundwater Basin (DWR Basin No. 8-4).

The subbasin also includes a small subarea west of the La Sierra Hills and east of the Santa Ana River (DWR, February 2004a). This northeastern arm of the Temescal Subbasin, referred to as the Norco area, consists of relatively low permeability alluvium and bedrock residuum flanked on the east and west by bedrock outcrops. Investigators in the Chino Subbasin include a portion of this area within the boundary of the Chino Basin (WE, July 2005). This division may be technically supported by a groundwater divide indicated by water level data in

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The Bedford Subbasin connects to the Temescal Subbasin near the base of Bedford Canyon. The connection occurs where the alluvium along Temescal Wash thins as the wash leaves the subbasin and traverses northward through bedrock (a reach referred to as Temescal Canyon) before entering Temescal Subbasin.

The Coldwater Subbasin connects to the Bedford Subbasin along a trace of the Glen Ivy Fault zone, a locally named fault related to the larger basin-bounding Chino-Elsinore Fault zone.

Since the delineation between the two subbasins has historically been the surface trace of a groundwater-impeding fault, the fault trace mapped by the U. S. Geological Survey (USGS) was used as the subbasin boundary (USGS, 2004).

2.1.2. Contributing Watersheds
The Temescal Subbasin receives runoff and recharge from almost 14,000 acres of uplands in the adjacent Santa Ana Mountains. Watersheds contributing runoff from the east are almost as large, but contribute less runoff because of lower elevations and corresponding precipitation. Watersheds contributing runoff to Coldwater and Bedford subbasins cover 9,525 acres and 11,858 acres, respectively, more than three times the area of the subbasins. Although the watershed contributing runoff to Bedford Subbasin is more than 2,000 acres larger than the Coldwater watershed, the Coldwater Subbasin receives more runoff due to the higher watershed elevations.

2.2. Study Period
An initial review of documents and data was used to define a Study Period to guide ongoing data collection and the water balance. Study Period selection considered significant changes that may have an effect on the groundwater basin such as land use, population growth, imported water, and groundwater production. The availability and quality of historical data were also considered. Selecting a relatively recent period makes good use of available data and represents the current state of the basin, including changing land use and management.

Rainfall patterns and hydrologic cycles were also reviewed to select a representative Study Period. Average annual rainfall within the Temescal Subbasin, along with a cumulative departure curve is provided on Figure 5. Based on the data review and rainfall patterns, a Study Period from water year 1990 through water year 2004 (15-year period) was selected for focused data collection. This period contains a range of wet and dry cycles and approximates long-term average precipitation. The average annual rainfall for the Study Period is about 15 inches per year, in good agreement with the average of 15.7 inches per year at the Chase precipitation station (Figure 5). The Study Period begins in drought conditions when water levels in the basin are

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The Study Period also allows for evaluation of changes in water demand and supply.

Although the City has grown steadily in population since its inception in 1896, significant population increases occurred between 1960 and 1970 and between 1985 and 1995. During each of these two decades, population doubled (AKM, April 2005). From 1985 to 2004, the population more than tripled, increasing from 45,750 to 144,274. Current population is approximately 149,400 (2008). Accompanying this growth was a change from predominantly agriculture to more urban land uses and a large increase in urban water demand. Much of the demand increase through the 1990s was met with an increase in imported surface water supplies. However, over the last five years, groundwater production increased from about one-third of the City’s supply to about one-half, an increase contained within the Study Period.

Although the more quantitative assessments including the groundwater basin water balance and numerical modeling were conducted for the Study Period, additional historical data were also compiled. These documents and data provide useful information on the conceptual model of the three subbasins and changes in groundwater conditions over a relatively long time period.

2.3. Data Types and Sources
Data collected for the GWMP are summarized below by data type and are described in more detail in following sections.
• Hydrologic – Climatic data (e.g., precipitation and evapotranspiration), reservoir storage, and streamflow.
• Land Use – Land use maps over time indicating areas of agriculture, urban growth, and open space corresponding to changing water use, irrigation, and pumping patterns. • Geology – Maps of geologic units and faults, lithologic information from wells, and soil types.
• Groundwater – Subbasin boundaries, well locations and construction, pumping tests, water levels, and ambient groundwater quality.
• Water Quality – Data included water quality analyses from municipal wells compiled from the City and the California Department of Public Health (DPH) (formerly the Department of Health Services). Data were also collected for Regulated Facilities in the Study Area. These data include water quality analyses conducted and compiled by the City as required by state regulations. Data were obtained from the Regional Water

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Quality Control Board (RWQCB) and other local agencies relating to basin water quality from monitoring at commercial or industrial activities. • Water Supply – Drinking water and other water uses from groundwater pumping (by the City and others), imported water, and recycled water.
• GIS Base Maps and Layers – Supporting physical and cultural information were compiled for use in the project GIS such as roads, freeways, city limits, parcels, sphere of influence, building footprints, digital elevation models, streams, rivers and lakes, and other data.

Primary sources of data for this GWMP were local and state public agencies including the City, County of Riverside, RWQCB, USGS, DWR, and the Santa Ana Watershed Protection Agency (SAWPA). SAWPA, in particular, was a helpful resource for filling key data gaps and acquiring physical and cultural data for the GIS base maps. SAWPA was first formed in 1968 as a planning agency, and reformed in 1972 with a mission to plan and build facilities to protect the water quality of the Santa Ana River Watershed (SAWPA, 2006). Within SAWPA, the Information Systems and Data Management team develops and maintains water-related data that are used by SAWPA staff for data analysis and dissemination. These data are available online through the Santa Ana Watershed Data Management System (SAW DMS, 2006).

2.4. Hydrologic Data
The main sources for hydrologic data in the Study Area included the California Irrigation Management Information System (CIMIS), County of Riverside, National Weather Service, and USGS as described in more detail below.

2.4.1. Climate Data
Precipitation data were available for four stations in the Santa Ana River Watershed as shown on Figure 2. Location data for each station are also included in the DMS. Data for the University of California Riverside Station # 44 were downloaded from the California Irrigation Management Information System (CIMIS) website. Data for the Chase, Norco, and Elsinore stations were obtained from the County of Riverside. Data are available monthly from June 1965 to the present for the three county stations (Chase, Norco, and Elsinore) and from June 1985 to the present for the CIMIS station.

The spatial distribution of average rainfall (isohyetal maps) in the Study Area was available from several sources. SAWPA files contained an isohyetal over the entire Santa Ana River Watershed (Figure 2). A long-term average isohyetal map was also obtained from the Oregon Climate Service (OCS) and Oregon State University using PRISM (parameter-elevation regressions on independent slopes model), a climate modeling and mapping system (OCS, January 8, 2007). The PRISM Group, supported by numerous agencies and used by DWR,

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV models complex precipitation patterns over large areas to develop a more accurate predictive precipitation tool. This PRISM isohyetal map was used in the basin water balance and is shown on Figure 6.

Monthly evapotranspiration (ET) data were available from June 1985 to May 2006 for the CIMIS station. Long term pan evaporation data from 1948 to 2005 were compiled from an additional station in Riverside County (Riverside Citrus Exp. St. Station). These data, along with other information such as annual ET coefficients for various crops were downloaded from the DWR Division of Planning and Local Assistance (DPLA) website. The DWR DPLA divides the state into Detailed Analysis Units (DAU) for purposes of data reporting. The City is located in the North Riverside DAU. Both reference ET data and crop coefficients were added to the DMS.

2.4.2. Streamflow
Surface water gage data for Temescal Wash were available from the USGS National Water Information System (NWIS) as shown on Figure 7. Data from one active and several inactive gages were compiled. For the gage located along Temescal Wash between Bedford and Temescal subbasins (USGS Station no. 11072000), daily data were available from October 1928 to June 1980. For the active gage in the City near Main Street (11072100), daily flows from October 1980 to April 2007 were downloaded and added to the DMS as a separate table.

2.4.3. Reservoir Storage
Lake Mathews is used to store much of the imported water that supplies the City (Figure 3). Monthly reservoir storage data from October 1961 to May 2006 were downloaded from the California Data Exchange Center (CDEC) and included in the DMS.

2.5. Water System Data

2.5.1. Pumping Data
The City provided numerous pumping summary tables in pdf format on a compact diskette (CD). This CD contained annual pumping data by well from 1964 to 1999 for City wells, with some data gaps (e.g., data for years 1994 to 1999 appear to only include Wells 1- 4, 20, and 21). In addition to the annual data, monthly data were available for calendar year 1988 and from January 1990 through December 2004 (except for July 1996 through December 1996).

Monthly data were summed to yield annual pumping by well and combined with the available annual data.

City production data were also available from a consulting firm, Water Master Support Services (WMSS), which compiles production data with the WMWD service area (including the City of Corona). These data were provided by the WMSS on a CD. Data included both tabulated reports in pdf format as well as an electronic table of production data in MS Access format. Data include pumping by the City and 56 other users in the Study Area from 1947 to 2004.

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV Production totals from the City tables were compared to production amounts contained in the WMSS data in acre-feet per year (AFY). Pumping totals were almost identical from 1995 to present, but varied somewhat in the earlier years (1964-1995). The total production error between these two data sets was judged to be relatively small when using known City wells (amounting to a discrepancy of a few percent of AFY produced), and the City’s monthly pumping data were used when available.

The largest discrepancy in the WMSS data was the large number of production wells that were allocated to the water supply system, but are not necessarily City wells. This discrepancy was more prevalent during the early portion of the Study Period than later years. Research conducted on several of these wells indicated that they were irrigation wells at parks throughout the City and/or older wells previously owned by others that were subsequently obtained by the City and abandoned. For example, two older wells thought to be previously owned by Orange Heights Water System (and designated MAIN 3 and MAIN 4) were on the property obtained by the City for the construction of City Hall. While there were no records to independently verify historical production totals from these wells, locations and pumping totals were reviewed for reasonableness and generally left unmodified in the production database.

2.5.2. Imported Water Data
The City imports water through WMWD from the Colorado River and the State Water Project. Data on imported water volumes at the main treatment plants and system interties were provided by the City for this project. Annual data were provided from 1964 through 1999 and monthly data were available from 1990 through 2004. These data are included in the DMS with the pumping data.

2.5.3. Water Demand
The City’s 2005 update of its Urban Water Management Plan (UWMP) contains statistics on water demand (including population, number of housing units, and population per household) in 5-year increments from 1970 to 2003 (AKM, December 2005). Population data for various time periods from 1900 to 1960 are also available in the UWMP.

2.5.4. Wastewater Treatment Plant (WWTP) Data
Information from the City of Corona’s three WWTPs and the volume of discharge to ponds and Temescal Creek were provided by the City from 1997 to present. Earlier data were apparently destroyed accidentally and were estimated for this GWMP using verified methods and City information on discharge locations. Additional operation and location information was available in the National Pollutant Discharge Elimination System (NPDES) permits issues by the RWQCB.

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2.6. Groundwater Data
Groundwater data were compiled from multiple sources including DWR, SAWPA, Riverside County, and the City. Groundwater data available from SAWPA includes groundwater elevations, general analytical chemistry, and well construction information compiled from 37 local agencies (water districts, cities, counties). However, complete data, including well construction and water levels or quality, were available for only a few wells in the Study Area.

2.6.1. Basin and Watershed Boundaries
DWR publishes maps and descriptions of California groundwater basins in DWR Bulletin 118. This document and the accompanying basin descriptions are updated periodically.

Basin descriptions for the Study Area were updated in February 2004. The last update for the basin map was in 2003. Groundwater basin boundaries are available in GIS-compatible data files and were obtained from DWR for groundwater basins in the Study Area. Since Temescal is a DWR-defined subbasin, the delineation of this subbasin was available in the files and has been used unmodified in this study.

Because Coldwater and Bedford subbasins are not delineated in the DWR files, GIS shape files were created for these subbasins. Subbasin boundaries were based on previouslydefined boundaries and the location of geologic faults (DWR, 1959; MWH, 2004; USGS, 2004).

The Coldwater Subbasin was delineated from the larger Elsinore Groundwater Basin boundaries on the west, north and south, and the location of the North Glen Ivy fault on the east as mapped by USGS (2004). The Bedford Subbasin boundaries are coincident with the Elsinore Groundwater Basin boundaries on the north and east and the North Glen Ivy fault on the west.

The southern boundary was based on the narrowing of Temescal Wash through surface bedrock outcrops, and checked for similarity to boundaries previously published (DWR, 1959). These modified subbasin boundaries are shown on Figures 1 and 3 and used in calculating subbasin areas in this GWMP.

The contributing watershed areas for the subbasins in the Study Area were delineated digitally by Todd Engineers, using GIS software to create shape files of the defined watersheds. Watershed delineation relied on electronic USGS Digital Elevation Models (DEM) (10-meter resolution) and topographic elevation contours of the Santa Ana quadrangle provided by USGS (2004). DEM files were processed in ArcView to provide shaded relief maps, slope percentage maps, slope aspect maps, and elevation contour maps at varying contour intervals. These maps were combined with the USGS elevation contours, hydrologic features, and DWR groundwater basin boundaries to manually delineate watershed boundaries.

Watersheds were defined to include those areas that could potentially contribute surface runoff to the three main Study Area subbasins and are shown on Figure 3.

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2.6.2. Well Data
Well locations and construction information tie key data (e.g., pumping, water levels, and water quality) to spatial and vertical locations within the groundwater basin. Sources of well locations and construction include SAWPA, DWR, the City, and Riverside County.

SAWPA provided a list of 312 wells in the Study Area, 174 of which contained detailed location data (latitude/longitude) and 60 of which contained some well completion information (e.g., depth, screen intervals, and casing). SAWPA well data were included in the DMS as a separate table maintaining the format from the original data source.

A database was created by Todd Engineers of selected DWR Driller’s Log data for approximately 325 wells. These data are included as a separate table in the DMS. Completion dates for these wells range from 1905 to 2004, but approximately half of these wells were drilled after 2000. Locations of 131 of the wells with Driller’s Logs were estimated using the state well number and added to the DMS. The Master Well table within the DMS contains a field for each record indicating the method used to locate the well. The method of the DWR wells location is noted as “manual” to indicate the approximate nature of the placement. An older DWR document (1959) lists 112 wells in the Temescal, Coldwater, and Bedford subbasins that were drilled before 1959, most of which are listed as irrigation or domestic wells. The earliest completion date is 1912, but completion dates are unavailable for most wells in the document. Because key hydrologic and hydrogeologic data cannot be tied to these individual wells, these well data have not been included in the electronic DMS.

Construction information for the City’s 31 wells (including inactive and abandoned wells) were compiled from several documents including the Water Master Plan (AKM, April 2005), the Drinking Water Source Assessment and Protection Plan (DSWAP) (Kennedy/Jenks, 2002), and a focused hydrogeologic assessment document prepared for the City’s desalter facility (Fox/Roberts, 2004). Data were entered into Excel spreadsheets and re-formatted into a separate table in the DMS.

The U.S. Geological Survey compiles and publishes well information such as well location, construction, and available water level data through a web based portal, the National Water Information System (NWIS). The system was queried for wells in the Study Area, and 18 wells with location data were identified and added to the DMS.

Well construction data were also available from a limited database that Riverside County initiated in 1990. Any well drilled after 1990 in the County is included in the database and earlier wells are being added as resources become available. The County database contains 683 wells in the Corona area, most of which are relatively shallow monitoring wells (551 wells or 81 percent).

The remaining 132 wells are listed as municipal (2 percent), domestic (5 percent), irrigation (3 percent), or unknown (9 percent) wells. The County well database was also included as a table in the DMS.

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV Well location and construction data from all sources were compiled into one table in the DMS. Some wells may be duplicated in this table as it difficult to match wells between sources.

Data from each source were also retained as a separate table in the DMS for updating and archiving purposes.

2.6.3. Water Level Data
Water level data in the Study Area were available from SAWPA and the City.

Approximately 100 wells contain at least one water level measurement ranging from June 1919 to September 2004. The number of groundwater elevation measurements per well varies from 1 to 1,083 distinct monitoring events. Each well with water level data has been assigned a unique ID that links the water level data to other well information, such as location and construction, if available. Water level data were also available for City wells from 1998 to 2005. Water level data from both SAWPA and the City were re-formatted and entered into the DMS.

No historical water level contour maps could be found in previously published documents that covered the Study Area. A few water level contour maps were available for relatively small portions of the Study Area for a few time periods. The earliest available water level contour map is a DWR map for March 1957 water levels (DWR, 1959). The map covers the northern portion of the Study Area and small sections of the Elsinore Groundwater Basin to the south. Wells used to construct the map are provided in a summary table, but actual water level measurements in each well were not included in the report and therefore are not included in the DMS.

2.6.4. Water Quality Data
Ambient groundwater quality data were available from the City, SAWPA, and DPH.

SAWPA water quality data were available from 101 wells. The number of monitoring events per well varied from 1 to 180. The average number of constituents analyzed per event per well ranged from 2 to 50.

DPH requires water quality sampling of drinking water systems larger than six connections. The Division of Drinking Water and Environmental Management (DDWEM) compiles these data into a statewide database. The database was obtained from DPH and queried for all wells, surface water, and intermediate system connections in the Corona area. Water quality data were available for 69 stations, 39 of which were operated by City of Corona. Other owners include the City of Norco, Glen Eden, Home Gardens, and California Rehabilitation Center. The number of monitoring events per well ranged from 1 to 567. Most monitoring events included the full suite of Title 22 drinking water constituents.

2.6.5. Regulated Facilities
Potential threats to groundwater quality are regulated by RWQCB, Department of Toxic Substance Control (DTSC), and the Riverside County Department of Environmental Health. A

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV review of the RWQCB database identified 30 major sites that are regulated for possible environmental releases in the Corona area and approximately 75 Underground Storage Tank (UST) investigations. Of non-UST sites, 18 are regulated by the Spills, Leaks, Investigations, and Cleanup (SLIC) Program at the Santa Ana RWQCB and two are landfills. The remaining 10 sites are regulated by DTSC.

Data collection has focused on facilities whose discharge is regulated by the RWQCB, sites that are being investigated for impacting groundwater, and leaking underground storage tank sites. Data include location, site characterization, water quality, and other information.

A file review was conducted at the Santa Ana RWQCB in July 2006. Groundwater quality and other environmental data were copied from 11 sites. Electronic databases were unavailable and data were evaluated from paper copies and not hand entered into the DMS. Water quality data for four UST investigations are available from the State Water Resources Control Board (SWRCB) online through their data management system, Geotracker. These data were included as a table in the DMS.

2.6.6. Land Use Data
Land use maps in the form of GIS shape files were available from the DWR DPLA and the Department of Conservation Division of Land Resource Protection (DC DLRP). DWR DPLA conducts complete land use surveys approximately once every ten years for the Upper Santa Ana River Drainage Area. The most recent survey, 1993, was available from the DWR website as a GIS shape file. A summary table of this map, which includes the total area by land use type within the basin and watershed area, was added to the DMS. Additional surveys (years 1957, 1964, 1975, 1984) were available on paper from DWR, but were not converted to electronic format and are not included in the DMS.

In addition to land use data, DWR DPLA also publishes data on applied irrigation rates for specific crop types in each DAU. Data were available on the DWR website for 1998 through 2001. A table of the water use (AFY per acre) for each crop type for the North Riverside DAU was included in the DMS.

The Farmland Mapping and Monitoring Program (FMMP) of the DC DLRP determines the area of farmland in the state on a biennial basis. In Riverside County, maps showing farmland and urban areas are available for the even years 1984 to 2004 in GIS (shape file) format.

Summary tables with the total amount of agricultural land by year for DWR and FMMP are included in the DMS.

The City provided a detailed parcel map for the project GIS with information regarding the zoning of each parcel. These parcels, differentiated by zoning type, were compared with the other sources of land use to confirm areas of urban and agricultural land.

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2.7. Geologic Data
USGS data provided the primary source of geologic units and faulting in the Study Area.

Additional documents and data were used as described below.

2.7.1. Geology Maps
A digital geologic map of the Santa Ana 30’ x 60’ quadrangle was obtained from USGS (2004) and imported into GIS. A summary table, including the total area of each geologic unit, was added to the DMS.

2.7.2. Lithologic Data
Subsurface lithologic data were available from DWR Driller’s Logs (400 paper logs compiled), available City well-completion reports, and geophysical logs for six City wells.

Lithologic information was also available for 10 wells in the SAWPA database.

2.7.3. Soils Data
Soil type and the respective soil moisture holding capacity governs the amount of recharge and runoff that occurs in an area. Digital soil maps and a database of physical properties for soils in Riverside and Orange counties were downloaded from the Natural Resources Conservation Service’s (NRCS, formally the Soil Conservation Service) website. In addition, the NRCS also provides a methodology for estimating the amount of runoff that occurs based on land use type. A summary table of the acreage associated with each soil type was added to the DMS.

2.8. GIS Files and Layers
The City maintains a GIS and provided numerous shape files in support of this project including parcels, city limits and sphere of influence, roads, storm detention basin locations, production well locations, and a high resolution aerial photograph. In addition, numerous GIS files were obtained from the Santa Ana Watershed Project Authority (SAWPA) from an online user system. These files included physical and cultural features as well as limited groundwater data sets such as water levels and water quality. Additional GIS files were downloaded from various sources as previously mentioned.

2.9. Data Management System (DMS)
The DMS includes one main relational database in Access format with individual tables for data types summarized above. A summary of the tables included in the DMS relational database is provided on Table 2-2 below. This database provides a flexible framework, allowing additional data to be incorporated as available. The project GIS was populated with shape files generated from selected data sets as well as selected publicly- or commercially-available GIS layers as described above.

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Data Tables in the Data Management System (DMS)
DMS Table Name Description Source(s)
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Numerous inconsistencies and duplicative data types were noted as data were compiled from various sources. Data sets were evaluated for quality control as needed, but only minimal deletions or modification have been made to preserve data that may be potentially important in the future.

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3. State of the Groundwater Basins
The groundwater subbasins of the Study Area have undergone significant changes since groundwater development began in the early 1900s (DWR, 1959). Since that time, the groundwater subbasins have supported a variety of uses including extensive agricultural irrigation (especially citrus), industrial demand from mining and citrus packaging, and increasing urban use.

Early agricultural activities in the subbasins were supplemented by diversions of surface water imported into the basin. Agricultural reliance on groundwater increased through the 1940s and 1950s, apparently peaking in the early 1960s but continuing into the 1970s. Increasing urban use has replaced most of that early agricultural demand.

The Study Area subbasins occupy a small portion of the upland Santa Ana River watershed, which covers more than 1.5 million acres in San Bernardino and Riverside counties (Figure 2).The Study Area subbasins cover about 47 square miles (about 30,000 acres) in western Riverside County (Figures 2 and 3) and include portions of townships/ranges 3S/6W, 3S/7W, 4S/6W, 4S/7W, and 5S/6W. The subbasins and the local watersheds that contribute runoff are contained within an approximate 400-square mile area outlined in Figure 3.

3.1. Land Use
Current and historical land use in the Study Area is shown on the land use maps on Figure 8. Two maps, one from 1984 and one from 2004 illustrate changes in land use over the last 20 years. As shown on Figure 8, land use on the Study Area subbasins, especially Temescal Subbasin, is predominantly urban (shown by the pink color). The urbanization has progressed mainly over the last 35 years as population in the subbasin has risen and agriculture has moved out. A comparison of the two maps on Figure 8 illustrates the change from agriculture (green) to urban (pink) land use for large portions of Temescal, Coldwater, and Bedford subbasins.

In the 1950s and 1960s, the subbasins consisted mainly of irrigated agricultural lands with a variety of crops, especially citrus. In 1957, approximately 7,000 acres of Temescal Subbasin were under cultivation, 1,100 of which were devoted to citrus and avocado production near Corona (DWR, 1959). During that year, approximately 17,000 acre-feet per year (AFY) of groundwater were pumped from the basin, primarily for irrigation and citrus processing facilities with some municipal use (DWR, 1959). At that time, less than 10,000 people lived in the subbasin.

Agriculture and native vegetation were the predominant historical land uses in both Coldwater and Bedford subbasins. In 1957, about 1,700 acres were irrigated in the two subbasins.

Although some urbanization has occurred in both subbasins, much of the land remains

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV undeveloped. Sand and gravel mining has been the predominant industrial land use in Coldwater Subbasin, an activity that continues today.

Groundwater production data suggest that the peak of agricultural pumping in Temescal Subbasin was from about 1959 through about 1966, but irrigation continued through most of the 1970s. By about 1980, most of the growers and citrus processors had left the basin. The 1984 land use map on Figure 8 suggests that large portions of southern Temescal Subbasin continue to be used for agriculture, but most of this land was likely fallow or non-irrigated pasture by 1984.

Groundwater production totals for the 1980s indicate that irrigation had decreased significantly in the subbasin.

The contributing watersheds that surround the subbasins consist mostly of native vegetation or grasslands used for grazing. With the exception of urbanization of the small watershed on the northeastern side of Temescal Subbasin, land use on the contributing watersheds has not changed significantly over the last 20 years.

The northern edge of the Study Area contains a portion of the Prado Dam Management Area, shown as native on the land use maps (see also Figure 7). The management zone, operated by the U.S. Bureau of Reclamation, is a 6,800-acre area generally defined by a ground surface elevation of 560 feet above mean sea level (msl) and serves as flood control for the Santa Ana River at Prado Dam.

3.2. Physical Setting
The groundwater basins are in a high desert setting in the rain shadow of the Santa Ana Mountains in western Riverside County. The basins are at the downstream portion of the Santa Ana River watershed.

3.2.1. Topography
The elevation of the ground surface in the Study Area ranges from below 500 feet msl at Prado Dam to more than 5,600 feet msl at the highest peak in the Santa Ana Mountain watersheds west of Coldwater Subbasin. The floor of Temescal Subbasin slopes from about 1,500 feet msl along the base of the Santa Ana Mountains in the southwest to about 500 feet msl in the northwest. The ground surface elevation in the city center is about 650 feet msl. In Coldwater Subbasin, elevations along the western mountain front are about 1,500 feet msl, similar to the Temescal Subbasin mountain front. The Coldwater Subbasin floor slopes to an approximate elevation of 1,000 feet msl near the eastern subbasin boundary along the Elsinore-Glen Ivy Fault zone. Bedford Subbasin slopes from about 1,100 feet msl on the south and west to about 850 feet msl on the northeast where Temescal Wash exits the subbasin (Figure 3).

Surface elevations increase significantly from the mountain front at the groundwater basin boundaries (about 1,500 feet msl) to the higher elevations in the contributing watersheds.

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV For the contributing watersheds in the Santa Ana Mountains to the west, elevations range from about 2,500 feet msl in the north to more than 5,600 feet msl in the south. The watershed west of Coldwater Subbasin rises above 5,600 feet msl. Watersheds east of the subbasins are significantly lower in elevation and rise only to about 1,800 feet in the highest areas east of Bedford and Temescal subbasins.

3.2.2. Precipitation and Evapotranspiration (ET)
Annual precipitation varies from below 12 inches to more than 26 inches over the Study Area. As shown on the isohyetal map on Figure 6, 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.

The variability of rainfall on an annual basis is illustrated by the rainfall records from the Chase precipitation station, located in the southwestern portion of Temescal Subbasin (Figure 6).

Over the last 40 years, annual rainfall at the Chase Station has ranged between about 4 inches per year to 34 inches per year with an average of 15.7 inches per year (Figure 5). Although the average rainfall of 15.7 inches per year since 1965 is slightly higher than predicted by the longterm isohyets on the figure, the Chase Station data illustrate the variability of rainfall in the Study Area. Annual rainfall totals range from less than 5 inches per year to more than 30 inches per year.

Rainfall patterns indicate several wet and dry cycles persisting from about 4 to 8 years.

Data from the Chase Station are plotted as a cumulative departure curve on the lower portion of Figure 5. The graph relates annual rainfall to average rainfall as a percentage and indicates dry cycles with downward slopes and wet cycles with upward slopes. This plot more clearly demonstrates the wet and dry cycles that have occurred since 1965 and shows that only a few time periods can be characterized as average rainfall conditions.

Long term pan evaporation data from 1948 to 2005 were compiled from a station in Riverside (Riverside Citrus Exp. St. Station). These data indicate an annual potential evaporation of 75.66 inches per year ranging from 3.03 inches per month in December to 10.88 inches per month in July.

3.2.3. Streamflow
Temescal Wash (also referred to as Temescal Creek) is the primary surface water drainageway traversing from south to north across the Study Area draining the Temescal Valley (Figure 7). Originating south of the Study Area, the wash flows north through Bedford Subbasin, cuts through bedrock outcrops in Temescal Canyon, flows through Temescal Subbasin, and discharges to the Santa Ana River near Prado Dam. Streamflow in Temescal Wash is fed by storm water runoff and discharges from wastewater treatment plants within and upstream (south) of the Study Area. For example, Lee Lake Water District is currently allowed to discharge up to

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV about 1,000 AFY of tertiary treated wastewater (although some is recycled for reuse) (RWQCB, September 6, 2001).

Temescal Wash is lined through most of the Corona city limits. The concrete lining begins around Magnolia Avenue, about 1.5 miles after Temescal Wash enters the Temescal Subbasin (from Temescal Canyon to the south, see Figure 7). The lined portion of the channel is indicated on Figure 7 and continues from Magnolia Avenue to the City’s wastewater treatment ponds near the Prado Management Area. The only unlined portion in Temescal Subbasin is the

1.5-mile area where the wash emerges from Temescal Canyon. This area is characterized by high groundwater, likely the result of infiltration of streamflow and relatively fine-grained surficial deposits. Other than limited infiltration in this narrow section of the subbasin, Temescal Wash does not contribute significant recharge to the Temescal Subbasin.

The Study Area is also crossed by numerous drainageways originating in the surrounding watersheds to the east and west of the groundwater subbasins and draining toward the basin center. Drainageways originating in the Santa Ana Mountains west of the Study Area carry relatively large amounts of runoff into the subbasins.

Runoff from the Santa Ana Mountains into Temescal Subbasin has only limited opportunity for percolation into the groundwater basin. Drainageways are lined across the subbasin floor and funnel runoff into the lined portion of Temescal Wash. From there, runoff generally leaves the basin and provides surface discharge at Prado Dam. Some infiltration occurs in two large detention basins used for flood control near the western Temescal Subbasin boundary (Figure 7). These two basins, operated by the Riverside County Flood Control and Water Conservation District (RCFCWCD) and referred to as the Oak Avenue and Main Street detention basins, detain peak runoff from large storm events and allow for some infiltration to groundwater.

Runoff into Coldwater Subbasin has the opportunity to percolate into the relatively permeable surface sediments. In addition, berms along washes, diversions of surface water, and the presence of large gravel pits enhance groundwater recharge of runoff in Coldwater Subbasin.

Stream gage data exist along Temescal Wash but are insufficient to document inflows and outflows at each of the subbasin boundaries. Streamflow data were available at only three locations along Temescal Wash within the Study Area as shown on Figure 7. The southernmost gage is an inactive USGS gage that measures flow in Temescal Wash in the bedrock outcrop between Bedford Subbasin and Temescal Subbasin. The northernmost stream gages are located in northern Corona before Temescal Wash enters the Prado Management Area.

Although currently inactive, the stream gage in the bedrock south of Temescal Subbasin (Site No. 11072000, Figure 7) provides data on the amount of runoff available for infiltration into the groundwater basin north of the gage. Daily measurements from October 1928 through June 1980 indicate an average annual discharge of 4,062 AFY. Annual averages vary significantly from less than 80 AFY during dry periods to more than 8,000 AFY. Discharge during several

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV more recent wet and dry cycles (water years 1966 through 1979) averaged 4,488 AFY, in general agreement with the long-term average.

An active stream gage in the City of Corona (Site No. 11072100, Figure 7) measures runoff in the lined portion of Temescal Wash after additional stormwater discharge has entered the culvert. As such, flows at this gage are significantly higher than streamflow recorded to the south. Average discharge for the entire gaged period (1980-2006) is 19,575 AFY. This runoff leaves the subbasin and contributes to surface water outflow at Prado Dam.

3.2.4. Geology
The Study Area is located within one of the structural blocks of the Peninsular Ranges of Southern California. The groundwater basins occur 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 and Chino fault zones bound the subbasins on the west and trend along the mountain front.

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 between the Elsinore and Chino faults. 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 subbasins.

The geologic map on Figure 9 shows the distribution of these units in the Study Area.

The original map was constructed by the USGS (2004), but several similar geologic units have been combined on Figure 9 to simplify the display. The main surficial deposits on the floor of Temescal Subbasin include younger and older alluvial fans deposited from the erosion of volcanic rocks and Bedford Canyon Formation to the west. These units prograde across the basin to the northeast and are truncated by channel deposits along Temescal Wash.

The Coldwater Subbasin is also composed of alluvial fan deposits, mainly from the Bedford Canyon Formation and adjacent granitic rocks. Volcanic rocks are essentially absent from the uplands adjacent to Coldwater Subbasin so the character of the deposits and groundwater chemistry differ from the alluvial fans to the north. The alluvial fan deposits in Coldwater Subbasin continue into Bedford Subbasin and appear to have been disrupted by faulting. Channel deposits along Temescal Wash define the eastern boundary of Bedford

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV Subbasin. In northern Bedford Subbasin, a variety of Tertiary sedimentary units crop out including the Silverado (Paleocene), Vaqueros (Miocene), Topanga (Miocene), and Puente (Miocene) formations.

3.3. Aquifers and Hydrostratigraphy
The basin-fill alluvial deposits and, to some extent, the underlying sedimentary units make up the aquifers in the basin. The thicknesses of these units vary significantly across the Study Area.

To further evaluate aquifer thickness and basin geometry, the base of the unconsolidated sediments was mapped as part of this GWMP. Lithologic descriptions from driller’s logs were reviewed for evidence of consolidated sedimentary or igneous units (generally referred to in this document as bedrock) throughout the Study Area. These data were plotted in GIS and evaluated with surface topography and geologic outcrops to estimate a depth to bedrock beneath the subbasins. This surface was produced as a GIS raster file and color coded according to depth. The resulting map is shown on Figure 10.

As shown on the figure, the thickest portion of the alluvial basin (the deepest depth to bedrock) occurs in the central-west portions of the subbasins. The formation of a trough along the Elsinore-Chino Fault zone is indicated by the asymmetric basin geometry. The deepest depths occur along this zone as indicated by the orange and red colors. Unconsolidated sediments are estimated to be more than 1,000 feet thick in this area. Bedrock is much shallower in the eastern portion of the basin as indicated by the blue color on Figure 10. A slight deepening of the basin is indicated in the Arlington Gap by the lighter blue to green color. Here, unconsolidated sediments are approximately 250 feet thick. This area is interpreted to have been eroded by a branch of the ancestral Santa Ana River, accounting for the deeper base. Sediments throughout most of the Bedford Subbasin and in the Norco area are about 100 feet thick. Outcropping bedrock in the northern and eastern portions of the Bedford Subbasin is further evidence of the thin alluvial sediments.

Aquifer packages composed of various geologic units have been defined for this study based on depositional environment, degree of consolidation, groundwater production, and location throughout the Study Area. Three aquifer packages provide water supply to wells in Temescal Subbasin: the Channel Aquifer, the Alluvial Fan aquifers, and, to a lesser extent, consolidated sandstone aquifers. The thickness and geometry of these units were evaluated through the construction of hydrostratigraphic cross sections through the Study Area. The locations of five of the sections are shown on Figure 11. Three cross sections in Temescal Subbasin are provided on Figures 12 through 14 (A-A’ through C-C’) and two cross sections covering portions of Coldwater and Bedford subbasins (D-D’ and E-E’) are provided on Figure

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15. Each of the aquifer units and the cross sections on which they are illustrated are described in more detail below.

3.3.1. Channel Aquifer
A package of relatively homogeneous and highly permeable sands approximately 200 feet thick have been encountered in many of the City wells in the northern half of Temescal Subbasin. This sand package is interpreted as channel deposits of an ancestral arm of the Santa Ana River and, as such, is referred to as the Channel Aquifer in this document. The alignment of the aquifer suggests that an ancestral river channel had entered the Temescal Subbasin at Arlington Gap, eroding the sedimentary units and possibly older alluvial fan deposits in the area.

Permeable channel sands were deposited in the eroded channel over time. From the gap, the Channel Aquifer meanders northwest toward Prado Dam. The Channel Aquifer is limited in extent and is not present in the Coldwater or Bedford subbasins. The general extent of Channel Aquifer is shown by the dashed line on Figure 16, which also shows the distribution of hydraulic conductivity in various aquifer units.

The Channel Aquifer is illustrated on cross sections A-A’, B-B’, and C-C’ on Figures 12, 13, and 14, respectively. Cross Section A-A’ extends from the Santa Ana Mountains to the northeast across Temescal Wash to the bedrock high in the northeast. As shown on the section, the Channel Aquifer occurs in the northeastern portion of the subbasin and has a saturated thickness that ranges from 125 to 150 feet along this section. As illustrated on the section, Channel Aquifer sediments lie directly above granitic bedrock beneath Temescal Wash and above the Sandstone Aquifer in other areas (Figure 12).

Cross-section B-B’ is located north of A-A’ and extends from the Santa Ana Mountains through the Norco area (Figure 13). The Channel Aquifer is shown on the western side of the section southeast of the Prado Management Area. Similar to Cross Section A-A’, the saturated thickness of the Channel Aquifer is about 100 to 150 feet thick. The cross section also shows the absence of the Channel Aquifer in the Norco area and illustrates the shallow depth to bedrock there (generally less than 100 feet). The saturated thickness of alluvial sediments in Norco is generally less than 50 feet. Also indicated on the section is a groundwater divide in the Norco area (near well 53-499) indicating possible groundwater outflow from the Norco area to the Santa Ana River (Figure 13).

The Channel Aquifer at Arlington Gap is shown on Cross Section C-C’ (Figure 14). Here the saturated thickness is approximately 200 feet and well data indicate a thick and permeable sand package. The Channel Aquifer is underlain by the Sandstone Aquifer throughout most of this area.

Figure 16 shows estimated values of hydraulic conductivity (K) derived from test data on driller’s logs and/or City well aquifer testing data. The K value is an indicator of the aquifer’s

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV permeability and is expressed in gallons per day per square foot (gpd/ft2 ) or feet per day (ft/day).

As shown in the figure, the wells within the limits of the Channel Aquifer have the highest hydraulic conductivity values in the Study Area (Figure 16). The lower K values shown within the extent of the Channel Aquifer area on Figure 16 are generally from deeper wells tapping the underlying Sandstone Aquifer. The average K value of City of Corona production wells screened solely in the Channel Aquifer (Wells 7A, 8A, 9A, 17, 25, and 28) is 2,062 gpd/ft2 (276 ft/day).

3.3.2. Alluvial Fan Aquifers
Both older and recent alluvial fans have been deposited through time along the mountain front on the western edge of the subbasins. These fans have prograded across both Temescal and Coldwater subbasins from west to east (Figure 9). Although these deposits are relatively thick, the entire unit is heterogeneous and cannot be considered one single aquifer. Rather, sand lenses within the deposits collectively form the Alluvial Fan Aquifers. Lithologic data from wells are insufficient to map out the extent of the aquifers or characterize the deposits. Limited data indicate relatively fine-grained textures throughout much of the area, especially with depth.

The geometry of these units in the subsurface, including the contact with the Channel Aquifer, is illustrated on Cross Section A-A’ on Figure 12. The section illustrates the alluvial fan deposits that have infilled the basin. The fans have prograded across the basin and a thin veneer of these deposits likely overlies the Channel Aquifer at the surface (not shown on the section).

Wells that penetrate the entire thickness of the Channel Aquifer in the east do not appear to encounter alluvial fan deposits on top of the Sandstone Aquifer. The total thickness of the deposits is unknown, but appears to exceed 1,400 feet in the central subbasin.

Only limited data exist for estimating K values in the alluvial fan deposits of Temescal Subbasin. Sparse data from a few wells indicate a K value of generally less than 50 gpd/ft2 in the
Alluvial Fan aquifers and in the Norco area (Figure 16). Specific capacity data from a City of Corona production well (Well 27), drilled in the Alluvial Fan, indicated a lower K value of about 7 ft/day (PBS&J, 2004).

Alluvial fan deposits in the Coldwater and Bedford subbasins are shown on Figure 15.

The cross section on the left side of the figure shows the subbasin geometry and separation at the North Glen Ivy fault. The section on the right side is a north-south profile through the main portion of the Coldwater Subbasin where much of the subbasin production is located (Figure 11).

As shown on Figure 15, alluvial fan deposits in the Coldwater Subbasin range up to approximately 800 feet in thickness (consistent with the depth to bedrock map on Figure 10).

Although the alluvial fan deposits here originate from the same mountain range as those in Temescal Subbasin, sediments have been eroded from different source rocks and have different textures and water quality. These alluvial fan aquifers are interpreted to be more permeable overall than the fan deposits in Temescal Subbasin and contain less mineralized groundwater.

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV However, aquifers are not as permeable as the Channel Aquifer in Temescal Subbasin. Hydraulic conductivity values for the Coldwater Alluvial Fan aquifers are generally less than 100 gpd/ft2 (Figure 16).

3.3.3. Sandstone Aquifer
Some of the sedimentary units underlying the alluvial basin provide sufficient well yields to categorize them as aquifers. Although generally grouped with other bedrock units, the subsurface sedimentary rocks of Tertiary age in northeast Temescal Subbasin contain sandstone layers that are screened in several City wells (see Corona 24 on Figure 12). The estimated K value is 22 gpd/ft2 (3 ft/day) for one City of Corona production well (Well 24) screened solely in the Sandstone Aquifer (below the Channel Aquifer). Due to the limited production, small areal extent, increasing depths, and relatively low permeability in most areas, the Sandstone Aquifer is not considered a primary source of water supply.

3.4. Water Supply
For more than 100 years, Study Area subbasins have been an important component of water supply. More than 650 wells have been drilled in the Study Area dating back to the early 1900s according to various DWR and Riverside County documents. Well uses include irrigation and domestic pumping, municipal wells, and shallow monitoring wells associated with commercial and industrial environmental investigations. A DWR study conducted in 1959 lists 112 wells in the Temescal, Coldwater, and Bedford subbasins, almost all of which were used as irrigation or domestic wells. Only limited data are available from the older wells and it is unknown if historical wells still exist. Riverside County files indicate that a large percentage of existing wells have been drilled as shallow monitoring wells in the Study Area, but files do not contain location or construction data for most of these wells, limiting their use for this study.

The City has operated as many as 31 municipal wells in the Study Area over time. Some of the older wells were purchased from the Temescal Water Company, a former irrigation water provider in the basin. Over the last few years, the City has obtained its groundwater supply from about 18 active wells. Most of the Temescal Subbasin wells are screened in the Channel Aquifer (generally shallower than 300 feet deep), but three wells also produce groundwater from the deeper Sandstone Aquifer. Three wells are located in the Coldwater Subbasin and produce groundwater from the local Alluvial Fan aquifers.

3.4.1. Pumping
A groundwater production database was developed from City records and data from a private firm, Water Master Support Services (WMSS). The WMSS data included production records from WMWD (including the City of Corona) and 56 other producers in the three subbasins from 1947 to 2004. Data are provided as annual totals, but monthly pumping totals

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV were available for City wells from 1990 (with missing data in 1996). Total groundwater production by subbasin from 1947 to 2004 is shown on Figure 17. The location of pumping wells is shown on Figure 18.

As shown on the graph on Figure 17, groundwater pumping has varied over time and by subbasin. In the late 1940s, the total amount of groundwater pumping in the Study Area was about 20,000 AFY. That amount increased to between 25,000 AFY and 32,000 AFY from the late 1950s to the mid-1970s. Total groundwater pumping decreased to below 20,000 AFY in the 1980s and early 1990s due to a decrease in agricultural irrigation, but has increased to about 25,000 AFY in recent years due to municipal pumping. Most of the pumping occurred in Temescal Subbasin. Production in Coldwater Subbasin increased and accounted for more than one-half of Study Area production during a few years in the 1970s and 1980s, but has been less than 25 percent in recent years. Bedford Subbasin production is relatively minor and has decreased somewhat over time.

Most of the historical groundwater production (extending into the 1970s) was used for irrigation. During that time, groundwater supply was also supplemented with surface water and groundwater from adjacent basins conveyed by irrigation water companies. Data on sources and amounts of imports were generally unavailable, but some summary data were documented in an older DWR study (1947). After about 1980, agriculture lands had decreased significantly and almost all of the Study Area pumping was used for municipal supply.

Since 1980, the City has been the largest producer and currently pumps about 80 percent of all groundwater extracted from Study Area subbasins. The City also imports surface water from various sources to supplement the groundwater supply. The City has increased both groundwater production and imported supply over time, especially over the last 20 years, to meet increasing demands. The City’s increase in groundwater and imported water supply is illustrated on Figure 19. As shown on the graph, the total water supply from 1964 to 1984 remained relatively consistent at an average of 10,138 AFY, with about 72 percent from groundwater (average 7,296 AFY) and 28 percent from imported water (2,842 AFY). From 1984 to 2004, groundwater pumping has averaged about 12,000 AFY, but has generally increased along with total supply. Since 2002, total water demand has been over 40,000 AFY, with groundwater production at about 20,000 AFY.

In addition to City pumping, approximately 56 other well owners have produced groundwater in the Study Area since 1947. The largest producers are listed on the following table.

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Table 3-1
Major Groundwater Users
Data Review Period 1947-2004
Well Owner
Number
of Wells
Last Year of
Production
2004*
Production
(AFY)
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3.4.1.1. Pumping in Temescal Subbasin
The graph on Figure 20 re-plots the pumping totals from Temescal and Coldwater Subbasins (from Figure 17) separately to examine pumping in each subbasin more closely. As shown on the graph, production exceeded 15,000 AFY in Temescal Subbasin from 1951 to 1978 in support of agriculture irrigation with peak production occurring from 1959 through 1964.

Production declined generally to below 10,000 AFY by 1979 and averaged about 9,419 AFY over the next 17 years (1979-1996). During this time period, agriculture pumping had significantly declined, but municipal pumping had not yet increased. Since 2002, pumping has exceeded 20,000 AFY for the first time since the 1960s peak irrigation totals.

Almost all of this recent pumping is for municipal use. Industrial groundwater pumping is conducted by three companies in Temescal Subbasin (Minnesota Mining, Dart Container, and All American Asphalt) and accounts for about 700 AFY. There has been almost no agriculture pumping in Temescal Subbasin over the last few years.

3.4.1.2. Pumping in Coldwater Subbasin
As shown on Figure 20, groundwater production in Coldwater Subbasin has generally ranged from less than 3,000 AFY to more than 10,000 AFY. Since 1980, production has averaged 7,018 AFY.

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV There have been relatively few pumpers in Coldwater Subbasin over time. Most of the production has been by the City and EVMWD, the only municipal pumpers in the subbasin.

Historically, City and EVMWD production has averaged 61 percent (3,538 AFY) and 31 percent (1,932 AFY), respectively, of the total subbasin production. Most of the production in the basin is exported for out-of-basin use.

Coldwater Aggregates extracts water to support sand and gravel mining and is the only industrial pumper in the subbasin. Their pumping amounts have ranged from about 100 AFY to 300 AFY, except for a period of increased production from 1975 through 1980 when production averaged about 450 AFY.

A few well owners have also produced small amounts of groundwater to support agriculture and domestic use. Until the last few years, agriculture pumping was relatively consistent, averaging about 200 AFY since 1947. However, there has been no agriculture pumping recorded in Coldwater Subbasin since 2001. Agriculture pumping occurred mainly in the foothills along the western edge of the subbasin. Municipal and industrial pumping is clustered along the basin-bounding fault on the eastern side of the subbasin (Figure 18).

3.4.1.3. Pumping in Bedford Subbasin
As shown on Figure 17, production from Bedford Subbasin has been less than in Temescal or Coldwater subbasins. Since 1947, Bedford production has ranged from 373 AFY to 4,658 AFY and has declined slightly over time with decreasing agriculture land use. Several pumping wells exist at the mouth of Bedford Canyon, just north of the subbasin boundary (Figure 18). These wells are just outside of the Temescal subbasin boundary and are included in Bedford Subbasin pumping for convenience.

Most of the early production in Bedford Subbasin supplied irrigation on local ranches. In the late 1940s, agricultural pumping represented more than 70 percent of the total subbasin pumping. Since 1984, irrigation pumping has accounted for less than 20 percent (average 421 AFY) of total production. EVMWD has been the largest single pumper over the last 20 years, producing about two-thirds of the water extracted from the subbasin (or just outside the subbasin boundary, at Bedford Canyon on Figure 18). The City has also produced small quantities of groundwater in that area (abandoned City Well 4 east of Bedford Canyon). Historically, production associated with Bedford Subbasin by the City and EVMWD has averaged 194 AFY and 1,200 AFY, respectively. Almost all of the municipal production occurs just outside of the northern edge of the subbasin at Bedford Canyon (Figure 18).

3.4.2. Imported Water
The City imports water through WMWD, a member agency of the Metropolitan Water District of Southern California (Metropolitan). Water is supplied from both the Colorado River and the State Water Project (SWP). Figure 19 shows the annual amount of water imported over

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV time. From 1964 to 2004, water demand has increased by a factor of four and imported water has been an increasingly important component of the City’s water supply. Since 2000, an average of 23,126 AFY has been imported, accounting for more than one-half of the City’s total water supply. Additional information on the City’s water supply is provided in Chapter 4.

LLWD also imports water from WMWD for potable supply in Bedford and Coldwater subbasins. In 2004, LLWD provided 1,174 AFY of imported supply to local residential customers.

3.4.3. Wastewater
For more than 40 years, industrial and municipal wastewater discharge has occurred in the northern portion of the Temescal Subbasin. Prior to 1963, Sunkist Growers was discharging about 790 AFY of wastewater to land along Temescal Wash in the northern portion of the subbasin (DWR, 1965), a discharge that apparently continued into the 1970s. Since the 1950s, the City has been discharging municipal wastewater effluent into ponds along the wash or directly into Temescal Wash in compliance with their wastewater discharge permits (RWQCB December 19, 2001; September 26, 2001; April 17, 1998a). From 1955 to 1963, discharges averaged about 1,000 AFY (DWR, 1965).

The City operates three wastewater treatment plants (WWTPs), two of which provide recharge to groundwater in the Temescal Subbasin. WWTP No.1 and No. 2 are located in the northern portion of the subbasin. Prior to 1997, all of the wastewater effluent was discharged to one or more of 13 percolation ponds, 10 of which were at the western end of Rincon Street in the vicinity of the Corona Airport and three of which are located along Temescal Creek between Lincoln Avenue and Cota Street. Discharge to the ponds near the Airport have been discontinued and only the three ponds referred to as the Lincoln, Cota North, and Cota South ponds are currently in use for discharge percolation (Figure 7). After 1997, WWTP No. 1 also discharged a portion of the wastewater into Temescal Wash. Beginning in 2002, the City began recycling a portion of the tertiary treated wastewater from WWTP No. 1 for landscape irrigation, reducing the overall discharge. WWTP No. 3 is located at the southeastern corner of Temescal Subbasin and provides recycled water for irrigation. The plant also discharges a small amount of tertiary treated effluent into Temescal Wash when effluent exceeds the irrigation demand.

Detailed data on wastewater volumes discharged to Temescal Wash and Lincoln and Cota ponds were available only dating back to 1997. According to City personnel, earlier records are no longer available. Files at RWQCB only date back to 1993, and efforts to recover historical RWQCB file archives were unsuccessful. As such, historical amounts of discharge to the groundwater basin were estimated using a factor of wastewater generation per household as described below.

Population data, provided in five-year increments in the City’s Water Master Plan (AKM, April 2005), were evaluated on an annual basis from 1984 using a linear extrapolation. An

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV average household was assumed to be 3.3 persons. Based on current wastewater generation, a factor of 270 gallons per day (gpd) per household was used (AKM, September 2005). This method was applied to years where actual data existed to evaluate the accuracy of the methodology. The difference between estimated and actual total wastewater generation during those years was less than three percent, verifying the method for predicting total wastewater from 1984 through 1996. Operational information provided by the City indicated that all wastewater generated before 1997 was discharge to percolation ponds only. The decline from 1996 to 1997 reflects the beginning of discharge to Temescal Wash.

Using this methodology for historical estimates and recent City data, the amount of wastewater discharged to the ponds was graphed from 1984 to 2004 as shown on Figure 21. Over this time period, wastewater discharge to the ponds averaged 6,574 AFY.

3.5. Groundwater
Groundwater occurs under unconfined conditions in the unconsolidated sediments of the subbasins including the Channel Aquifer and Alluvial Fan Aquifers. Water level data from the underlying consolidated sedimentary units are limited, but groundwater is likely more confined in the deeper units. Water levels and groundwater flow in the subbasins are described in the following sections.

3.5.1. Water Levels
Groundwater data dating back to 1916 were compiled into a water level database from multiple sources, including DWR, SAWPA, USGS, Riverside County, and the City. At least five water level measurements in the Study Area were available for each year since 1924 with one or two measurements in 1916, 1919, and 1922. Hydrographs were generated for most of the wells containing five or more measurements to examine water level trends and fluctuations throughout the basin. Three key hydrographs were selected to represent long term water levels in each subbasin. Locations of the three wells used to construct the key hydrographs are shown on Figure 22 and hydrographs are presented on Figures 23, 24, and 25. A discussion of water level trends and fluctuations in each subbasin is provided below.

3.5.1.1. Water Levels in Temescal Subbasin
Water level changes in the Temescal Subbasin from 1953 to 2004 are shown on the longterm hydrograph on Figure 23. The graph shows the time period 1947 through 2004 for easy comparison to the pumping graph on Figure 20. The hydrograph combines water level data recorded during both pumping and static conditions in City Well No. 8, resulting in the somewhat spiking nature of the data, especially since 1987. Recent data from the City identified levels recorded during or immediately after pumping, but most of the data were not so designated.

Filtering out designated pumping water levels removed data that appeared consistent with static

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV conditions and left many data points remaining that appeared to be lower than static water levels.

As such, all levels are shown on Figure 23 to preserve the overall trend.

Since 1953, water levels have fluctuated a total of about 45 feet, from an elevation of 580 feet msl to about 535 feet msl (assuming the spikes below that level are influenced by local drawdown in the pumping well). In general, water levels correlate to wet and dry hydrologic cycles as shown by annual precipitation on Figure 5. The highest water levels were measured in the early 1980s in response to a wet hydrologic cycle that began in 1978. These higher levels also correlate to a period of relatively low pumping in the subbasin (Figure 20). During a later wet cycle from 1992 to 1998, water levels did not recover to 1980s levels, likely due in part to an increase in subbasin pumping (Figure 20).

Current levels appear to be near record lows with levels falling below 540 feet msl over the last few years. With precipitation data indicating near-average conditions in the basin, the declining water levels may be indicative of over-pumping conditions in the subbasin.

3.5.1.2. Water Levels in Coldwater Subbasin
Water levels in the Coldwater Subbasin are illustrated by the hydrograph from City Well No. 3 on Figure 24. As shown on the graph, water levels have fluctuated dramatically over the last 40 years in response to wet and dry cycles in the basin. In contrast to the 45-foot water level fluctuations noted in Temescal Subbasin, water levels in Coldwater Subbasin have varied more than 300 feet over approximately the same time period. The highest water level was recorded during 1983 at an elevation of 1,112 feet msl within 20 feet of the ground surface. During 2004, water levels fell below 800 feet msl for the first time in at least 40 years, possibly representing an all-time low water level for the subbasin.

The wide water level fluctuations over time in Coldwater Subbasin reflect the relatively small footprint and compartmentalization of the subbasin (Figure 21). The basin covers only about 2,000 acres and is surrounded on the west, north, and south by bedrock. In addition, communication with the adjacent Bedford Subbasin is impeded by the North Glen Ivy fault (associated with the Elsinore-Chino fault zone). Although the subbasin is capable of receiving large amounts of recharge from mountain runoff, it has a relatively limited storage capacity.

However, it is unknown whether the recent steep decline in City Well No. 3 is reflective of water level conditions on a subbasin basis. Water level data are mainly available only in or near active pumping wells in the subbasin.

3.5.1.3. Water Levels in Bedford Subbasin
An analysis of groundwater conditions in Bedford Subbasin was conducted in support of a recycled water feasibility study conducted for LLWD and provided in Appendix D. This analysis incorporates and builds on data presented in the main portion of the GWMP. The recharge project is a groundwater management strategy for potentially increasing subbasin yield.

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV As described in detail in Appendix D, very few wells in the Bedford Subbasin contain a sufficient water level record to analyze long term trends. However several wells near the northeast outflow of the subbasin allow for an analysis of water levels at that location (Figure 22).

One well, City No. 4, is located about 950 feet north of the northeast corner of Bedford Subbasin at the mouth of Bedford Canyon. Wells pumping in this area receive recharge from runoff in adjacent Bedford Canyon (Temescal Subbasin) as well as surface and subsurface outflow from Bedford Subbasin. The location is also downgradient from any subsurface outflow that occurs from Coldwater Subbasin (Figure 22). As such, water levels in this area are indicative of the total groundwater and surface water discharge where Temescal Wash temporarily leaves the subbasins.

A hydrograph from this Bedford Canyon well is shown on Figure 25.

As shown on the hydrograph, water levels have fluctuated only about 60 feet over the last 40 years. The hydrograph is plotted at the same scale as the Coldwater Subbasin hydrograph (Figure 23) for comparison to the 300 feet of change seen just south of this well. In the Bedford Canyon well, water levels have been recorded as high as 782 feet, but have remained above about 770 feet for most of the period of record. Water levels dropped to around 720 feet during the relatively dry cycle from 1987 to 1995.

The ground surface elevation at this well is reported to be about 791 feet msl (Figure 24) indicating that water levels are within 10 feet of the ground surface during times of high water levels. Downstream ground surface elevations are around 780 feet, similar to water levels in the well. These surface elevations indicate the level at which the groundwater basin is likely discharging to Temescal Wash as the Wash leaves the subbasins and traverses north across consolidated sediments in Temescal Canyon. Production wells in this area are expected to reduce surface flows in Temescal Wash, but do not appear to have significantly impacted groundwater in any of the subbasins.

3.5.2. Groundwater Flow Directions
Groundwater flow in the Study Area is generally from the surrounding uplands toward Temescal Wash and then north and northwestward toward the groundwater and surface water discharge location at Prado Dam.

Only a few water level contour maps exist in available documents and none of them covers the entire area of the subbasins. As such, water level data were plotted for various time periods to analyze groundwater flow directions over time. Water level contour maps are presented on Figures 26 and 27 for representative periods of low water levels and high water levels in the basin, respectively. These maps are discussed in more detail below.

3.5.2.1. Groundwater Flow – Spring 1964
Figure 26 shows a water level contour map based on water levels from Spring 1964 and represents a time period when water levels were at relatively low levels in each of the subbasins

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV as indicated on the key hydrographs (Figures 23, 24, and 25). Very few data points were available in Bedford or Coldwater subbasins during this time period, and water levels there are highly interpretive. In addition, almost no water level data are available in the alluvial fan deposits in southwestern Temescal Subbasin, so contours have been interpreted to mirror topography.

In the Bedford Subbasin, groundwater flows northward in the thin alluvial sediments.

Given the narrow alluvial constriction at the southern corner of the subbasin, there is unlikely to be significant subsurface inflow of groundwater into the Study Area from the south. Almost no water level data are available from the central portion of the subbasin and contours were interpreted using geology and ground surface elevations.

Groundwater in Coldwater Subbasin flows from recharge areas in the west toward the North Glen Ivy fault that separates Coldwater and Bedford subbasins. Outflow does not likely occur during times of low water levels when significant differences in water levels are noted across the fault. When groundwater outflow does occur from Coldwater Subbasin, flow likely follows subsurface channels beneath the surface water drainageways at the central portion of the subbasin boundary. Dissected outcrops of older, semi-consolidated deposits indicate a few pathways of incised surface water drainages emanating from Coldwater Subbasin and crossing Bedford Subbasin in this area. Once in Bedford Subbasin, both groundwater and surface water flow continue northward to the subbasin boundary where flow converges with groundwater flow out of Bedford Canyon. Here water levels rise and partially discharge to Temescal Wash as it enters Temescal Canyon.

An area of uncertainty is in southeastern Temescal Subbasin north of Bedford Canyon where a groundwater divide may be present. Highly dissected alluvial fan deposits and bedrock outcrops of various Miocene-age formations indicate complex geology and thin alluvial deposits north of Bedford Canyon (Figures 9 and 10). A groundwater divide is interpreted in this area, defined by northerly flow north of the divide and northeasterly flow in Bedford Canyon south of the divide.

In the southwestern portions of the Temescal Subbasin, groundwater flows northeast in alluvial fan deposits toward the area of the Channel Aquifer. Groundwater then flows northwesterly toward the subbasin outflow at the Prado Management Area. Groundwater rises and leaves the basin as surface water discharge at Prado Dam.

3.5.2.2. Groundwater Flow - Spring 1984
Groundwater elevation contours estimated for conditions in Spring 1984 are shown on Figure 27. Spring 1984 represents the end of an extended wet hydrologic cycle and water levels are at relatively high water levels throughout the Study Area. In general water levels in northern Temescal Subbasin are about 25 to 40 feet higher than in 1964. In Coldwater Subbasin, water levels are almost 200 feet higher than in 1964. In Bedford Subbasin, water levels appear to be

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV similar to 1964, constrained somewhat by the ground surface elevations. Groundwater discharge to Temescal Wash is likely occurring in northern Bedford Subbasin during times of high water levels. Groundwater flow directions are generally similar to those in 1964. However, outflow from Coldwater Subbasin is likely occurring in 1984, adding recharge to the Bedford Subbasin.

3.5.3. Groundwater Quality
Groundwater quality data for this study were sourced from SAWPA, the California DPH Drinking Water Program (DHS DDWEM, July 2006), and the City of Corona. Data were combined into a comprehensive database and used to identify the chemical signature of groundwater and concentrations of constituents of concern within the Study Area.

3.5.3.1. Inorganic Groundwater Chemistry
Inorganic water quality data from 102 wells in the Temescal, Bedford, and Coldwater subbasins were used to evaluate the general groundwater chemistry across the Study Area. Well locations are shown on Figure 28 and are color-coded by general areas of similar water quality.

The water quality in these areas may be impacted by inflows from different source areas based on the hydrogeologic analysis of the Study Area. These areas are summarized on the following table.

Table 3-2
Groundwater Areas for Water Quality Assessment
Subbasin Groundwater Areas Number of
Wells
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To characterize groundwater quality in these various areas, water quality data were evaluated using a geochemical plotting technique known as a Trilinear Diagram (Piper, 1944).

This technique plots the major anions and cations in percent milliequivalents per liter (% meq/L) to characterize inorganic water chemistry and differentiate samples of varying water quality.

Cations in % meq/L are plotted on the lower left triangle and anions in % meq/L are plotted in the lower right triangle. Data are projected onto the central diamond to evaluate overall water type.

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV Water samples of similar quality plot together in a cluster. Water samples that are a mix of two different source waters plot between the two source type end members.

Figures 28 and 29 show trilinear diagrams of the groundwater chemical signatures in Coldwater and Temescal subbasins, respectively. Only the most recent reported groundwater quality data for each well are plotted. This methodology combines data from 1953 to 2005, but a comparison of historical and recent data indicates no significant changes in inorganic water chemistry over time.

Overall, most of the water quality data indicate similar inorganic chemistry. As shown on the figures, data points for most of the wells generally cluster in the central portion of the diamond (shaded areas on the plots on Figures 28 and 29), indicating primarily a sodium/calciumbicarbonate water type. However, variability of water types can be correlated to specific areas and indicate the following relationships:
• Groundwater in the Coldwater Basin (Figure 28) has a relatively high calcium-to-sodium ratio compared to groundwater in Temescal Subbasin (with the exception of groundwater in the western alluvial fan). This relationship is likely caused by the chemical interaction of rainfall and outcropping granitic bedrock (and the lack of outcropping volcanic bedrock) in the Coldwater Basin watershed.
• Groundwater in wells located in the Bedford Canyon portion of Temescal Wash or Temescal Canyon (Figure 28) has a higher ratio of calcium-to-sodium and sulfate-tochloride than wells located in Arlington Gap. Relative cation concentrations indicate that groundwater in the Temescal Wash area upgradient of the Norco area is a mixture of waters from both the Temescal Canyon area and Arlington Gap, but are most similar to the water in Arlington Gap.
• Groundwater in wells located in the Norco area has a lower ratio of calcium-to-sodium and sulfate/bicarbonate-to-chloride than most other areas. • Groundwater in wells located in the southwestern alluvial fan has the highest ratio of calcium-to-sodium and sulfate-to-chloride/bicarbonate compared to groundwater in other areas. The water type in the alluvial fan may result from geochemical interaction between rainfall runoff and the outcropping Santiago Peak volcanics in the western catchment area of Temescal Subbasin prior to aquifer recharge along the base of the mountains. • Cation concentrations indicate that groundwater in wells located in Temescal Wash downgradient of the Norco area appear to be mixtures of groundwater from three sources:

Temescal Wash upgradient of the Norco area, Arlington Gap, and the western alluvial fan.

This water quality source assessment indicates the major sources of water by analyzing the blending of different water quality from different areas. Identifying major areas of inflow and outflow is critical in developing a strong conceptual model of the aquifer. Based on water

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV quality type, the groundwater in the Channel Aquifer appears to be derived mainly from Arlington Gap and to lesser extent Temescal Wash. In addition to these sources, the western Channel Aquifer also receives inflow from the Alluvial Fan.

3.5.3.2. Total Dissolved Solids (TDS) Concentrations in Groundwater Groundwater in the Study Area tends to be highly mineralized. Figure 30 shows the range of total dissolved solids (TDS) concentrations across the Study Area. Data represent the most recent concentration of TDS from 89 wells. The map indicates that groundwater in the Temescal Subbasin generally exceeds the secondary maximum contaminant level (MCL) of 500 mg/L for drinking water. TDS concentrations greater than 1,000 mg/L are observed beneath Temescal Wash and in the Norco area. Groundwater in the Norco area is also characterized by elevated hardness.

TDS concentrations in the Coldwater and Bedford subbasins are generally lower in TDS and range from 300 to 650 mg/L. Average TDS concentrations for each subbasin are summarized below.

Table 3-3
Total Dissolved Solids in Groundwater
Subbasin
Number
of Wells
TDS (mg/L)
Range Geometric
Mean
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3.5.3.3. Nitrate Concentrations in Groundwater
Elevated nitrate concentrations have been documented in the Temescal Subbasin since at least the 1950s. The latest reported nitrate concentrations (as NO3) for 78 wells in the Study Area are shown on Figure 31. Water quality data indicate nitrate concentrations ranging from 0.3 to 124 mg/L. Although the average nitrate concentration in the subbasin is 41 mg/L, nitrate concentrations in 28 of the 72 subbasin wells do not meet the primary MCL standard of 45 mg/L for drinking water. The highest nitrate concentrations are those associated with wells at the Arlington Gap where concentrations of groundwater entering Temescal Subbasin exceed 100 mg/L. Elevated nitrate concentrations are also generally located along Temescal Wash and on the western alluvial fan.

Groundwater quality in City wells typically does not meet federal or state drinking water standards for nitrate (45 mg/L). Nitrate concentrations (as NO3) measured in the City production

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wells typically range from 4.0 to 110 mg/L. Most wells require treatment and/or blending to meet regulatory requirements.

In the Coldwater Subbasin, groundwater nitrate concentrations (as NO3) for six water supply wells range from 0.4 to 6.5 mg/L, significantly below the MCL. Although data were generally unavailable for the Bedford Subbasin, DWR reports historical elevated nitrate and sulfate concentrations in the area (DWR, 1959). However, one recent sample (2007) from a Bedford Subbasin well indicated a relatively low nitrate (as N) concentration of 1.2 mg/L (LLWD, 2007).

3.5.3.4. Additional Water Quality Concerns
As urbanization has increased in the Study Area, the potential for groundwater quality impacts from anthropogenic (human-influenced) sources has also increased. Numerous underground storage tanks (USTs), dry cleaners, and industrial facilities are located across the subbasins and in adjacent basins. Potential impacts from historical anthropogenic sources are also a concern. For example, years of wastewater discharge by citrus processing facilities occurred in areas where locally elevated chloride concentrations have been detected. In addition, the U.S.

Navy operated an ordnance laboratory in the Norco area in 1957 (DWR, 1959). Data were compiled from regulatory agencies in the Study Area to identify areas of concern.

Regulated Facilities
Potential threats to groundwater quality are regulated by RWQCB, Department of Toxic Substance Control (DTSC), and the Riverside County Department of Environmental Health (DEH). A review of the RWQCB database identified 30 major sites that are regulated for possible environmental releases in the Corona area and approximately 75 Underground Storage Tank (UST) investigations. These sites are shown on Figure 32. Regulated facilities and USTs that overlie the areal extent of the Channel Aquifer are of highest concern, given the permeable nature, shallow depth, and the reliance on the aquifer for water supply.

Corona Sanitary Landfill
One regulated facility, the Corona Sanitary Landfill, has impacted local groundwater quality and remains a potential threat to existing city wells and the Channel Aquifer. Riverside County Waste Management Department (RCWMD) operates the closed sanitary landfill on an 80-acre site identified on Figure 32. Groundwater impacted by trichloroethene (TCE) has been mapped offsite and downgradient of the landfill. The TCE plume, as interpreted in a 1999 study, indicates that elevated TCE concentrations are migrating toward City wells (RCWMD, 1999).

The study also concludes that more than one source of TCE exists in the area.

Three City wells downgradient of the landfill plume have already detected low concentrations of TCE in micrograms per liter (ug/L) as summarized in the following table. One

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Table 3-4
TCE Detections in City Well Samples
Data Review Period 1999-2002
City Well
Number of
Detections
Highest TCE
Concentration
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Although none of the detections have exceeded the MCL of 5 ug/L, the occurrence of TCE at the wells indicates a continuing threat to water quality. Strategies developed for this GWMP consider options to address specific water quality concerns.

3.6. Water Balance
Preliminary water balances have been prepared for the two subbasins that provide City water supply, Temescal and Coldwater, to evaluate current conditions and future sustainability of the groundwater resource. Data are generally inadequate for a rigorous assessment, and many simplifying assumptions have been made; nonetheless, the water balances presented here provide useful information for basin management and address the sustainability of the groundwater resource.

Data gaps and uncertainties associated with the Bedford Subbasin limit the ability to quantify inflows and outflows. In addition, Bedford Subbasin is relatively shallow, characterized by thin alluvial sediments and relatively high water levels with very little water use. Only one groundwater management strategy was identified with the Bedford Subbasin (groundwater recharge by LLWD) and that strategy was analyzed based on water level data and did not require a detailed water balance. Further analysis of the Bedford Subbasin in a feasibility study of the LLWD management strategy is provided in this document as Appendix D.

The water balances for Temescal and Coldwater subbasins are useful beyond application to GWMP management strategies. The evaluation provides a tool to improve the understanding of the groundwater system and to refine the conceptual model. It also supports improved monitoring in the basin, identifying where additional data would be most useful. The water balance will continue to be refined and updated in the future as additional data become available. In addition, the water balance provided a foundation of the development of the numerical model used to assess some management scenarios.

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV The water balance relies on data presented in the previous sections of the GWMP.

Groundwater subbasin conditions and analyses are not repeated in this section, but previous figures are referenced where applicable. A more complete explanation of each figure is contained in the section where each was first introduced.

3.6.1. Approach
The water balance for Study Area subbasins examines inflow into the subbasins, outflow from the basins, and change in groundwater storage in the basin, recognizing the following relationship:

Inflows – Outflows = Change in Storage
To examine how these components change through time with varying amounts of recharge and pumping, the balance was conducted over a 15-year period, 1990 through 2004, covering a full hydrologic cycle of wet and dry conditions as well as significant changes in groundwater pumping. Change in groundwater storage over that time period was estimated independently using water level data, and compared to the net difference between estimated inflows and outflows to check for inconsistencies and to identify simplifying assumptions or data gaps of concern. For the Temescal Subbasin, the balance was further evaluated with the construction and calibration of a numerical groundwater model. These steps allow for a reasonable range of values to be determined for each element of the water balance and highlight the sensitivity of the water balance to specific elements.

To evaluate water balance components, the contributing watersheds and subbasins were subdivided and designated as water balance units to assist in the analysis. These units are shown on Figure 33 and allow for grouping areas together of similar land use, soil type, and/or other water balance factors within each unit. The delineation of similar areas within the water balance units are referred to in this document as water balance elements. These elements are shown on Figure 34 and represent areas of similar land use, soil type and precipitation zones.

Throughout this report, areas are shown to the nearest acre, and water budget items are shown to the nearest AF. As a result, large numbers may appear to be accurate to four or five significant digits, which is not the case. Values for data that are measured directly, such as water levels, streamflow, and groundwater pumping, are probably accurate to two or possibly three significant digits. Values for data that are estimated, such groundwater storage changes and groundwater inflows and outflows, are probably accurate to only one or two significant digits. All digits are retained in the text and tables to preserve correct column totals in tables and to maintain as much accuracy as possible when converting units or conducting subsequent calculations.

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3.6.2. Temescal Subbasin Water Balance
The water balance for the Temescal Subbasin was initially conducted through an independent evaluation of the different components of inflow and outflow from the subbasin. The resultant change in storage was checked for reasonableness by estimating the change in storage indicated by water level fluctuations over the Study Period. These inflows and outflows were then incorporated into a numerical groundwater model based on the hydrogeologic conceptual model of the basin. Inflows and outflows were adjusted during calibration to provide a better fit to measured water levels in key areas of the basin. The methodology for each of these steps is summarized in the following sections. Table 3-5 summarizes the water balance results as modified through groundwater model calibration. Documentation of the development of the groundwater model is provided in Appendix C.

Water Year 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Ave.

INFLOWS
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TOTAL INFLOWS (AFY) 14,956 15,844 15,549 26,605 14,871 18,035 16,264 12,696 19,057 11,940 14,030 14,788 15,728 13,618 16,338 16,021OUTFLOWS *URXQGZDWHU3XPSLQJ  

  
  
 
  
 

 
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TOTAL OUTFLOWS (AFY) 14,352 11,238 13,351 14,321 12,494 13,273 14,520 15,553 16,963 17,920 16,347 18,082 24,109 23,194 24,227 16,663 Table 3-5
Water Balance Summary for Temescal Subbasin
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Cumulative Change in Storage (AF) 604 5,210 7,408 19,692 22,069 26,831 28,575 25,718 27,812 21,832 19,514 16,220 7,839 -1,737 -9,627 -10,000
0 50,00040,00030,00020,00010,000
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Inflows / Outflows (AFY)
Change in Storage (AF)
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3.6.2.1. Inflows to Temescal Subbasin
Inflows to the Temescal Subbasins include the following:
• deep percolation from rainfall on the basin floor
• return flows from urban and agriculture irrigation
• infiltration of runoff from surrounding uplands
• stormwater infiltration at flood control basins
• discharge at wastewater recharge ponds
• subsurface inflow from adjacent subbasins.

Each inflow component is estimated on an annual basis over the Study Period from 1990 through 2004. Methodology, assumptions, and results are discussed below.

Deep Percolation from Precipitation
Deep percolation from precipitation is the amount of precipitation (rainfall) that falls on the floor of the groundwater basin and infiltrates through the soil to the underlying water table.

The volume of deep percolation is influenced by factors including the amount and timing of precipitation, soil type, geology, topography, vegetation cover, and extent of impervious areas (e.g., pavement and buildings). In the Study Area, deep percolation is limited due to the large impervious area of urban development that covers the basin floor, especially over the productive Channel Aquifer. In this area, a large portion of rainfall is funneled to lined storm drains and prevented from recharging groundwater. Nonetheless, deep percolation represents a significant portion of the subbasin inflow in wet years. It contributes almost no inflow in dry years.

Deep percolation was calculated over the Study Area using two steps: a runoff analysis and a soil moisture balance. The runoff analysis used the SCS Curve Number method to estimate the amount of precipitation resulting in runoff based on land use type, soil type, and precipitation amount. The soil moisture balance examines the precipitation that does not result in runoff and determines the amount available for groundwater recharge.

To account for the factors that vary spatially, the Study Area was divided into unique elements. This was accomplished by overlaying spatial maps to create elements each with a single soil hydrologic classification, soil moisture capacity value, precipitation multiplier, and land use category. Because the land use changes over time, a set of elements was created for each year that a land use map was available (i.e., even years from 1984 - 2004). For each year without a land use map (odd years), it was assumed that the land use remained the same as the previous year. The elements created for 2004 are shown on Figure 34.

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV For each element, the runoff analysis and soil moisture balance were applied to estimate deep percolation. Elements within the groundwater basin are applicable to deep percolation, while elements in the contributing watershed were analyzed as part of the evaluations of infiltration of runoff and subsurface inflow, respectively, which are addressed in subsequent sections.

Runoff Analysis
The Curve Number runoff analysis was developed by the SCS (Soil Conservation Service, now the U. S. Natural Resources Conservation Service, NRCS). The method is described in the document Technical Release 55 from the U.S. Department of Agriculture (USDA, 1986). Direct runoff is calculated as a relationship between rainfall, the potential maximum initial abstractions and the retention after runoff begins.

Rainfall was estimated for each element and each month using historical rainfall data from the Elsinore station and the PRISM isohyetal map (see Figure 6). For watershed areas with substantially higher rainfall than Elsinore, monthly rainfall amounts were estimated by applying a rainfall-elevation factor based primarily on the PRISM map. Land use also was considered.

Information on land use types and the portion of impervious area by housing type (provided in the Riverside County Flood Control and Water Conservation District Hydrology Manual) were used to derive a weighted average percent impervious area, 56 percent, which was used for all urban types. All precipitation falling on these impervious areas was assumed to become runoff that was captured by storm water collection systems (and removed from the water balance).

Initial abstractions include water that is captured before runoff. This initial abstraction includes plant interception, initial infiltration, and surface storage associated with ground cover and can be expressed as a percentage of the maximum retention. For the purposes of this study, initial abstractions were assumed to be 20 percent of the maximum retention, the recommended default value from the NRCS.

The potential maximum retention is estimated using a coefficient, or curve number. The curve number is based on information on land use and soil hydrologic classification, obtained primarily from the Hydrology Manual. The manual provides maps showing soil hydrologic groups (e.g., Group A – high infiltration through Group D – very slow infiltration) and provides the curve numbers for specific land use types and soil hydrologic groups. For this analysis, curves representing moderate runoff potential were used to calculate direct runoff on a monthly basis.

These runoff values then were subtracted from actual precipitation to derive the effective precipitation. The effective precipitation is assumed available to meet ET demands, to contribute to soil water capacity, and to provide deep percolation to groundwater.

Soil Moisture Balance
Once the effective precipitation was calculated in the Curve Number analysis, it was input to the soil moisture balance. The soil moisture balance accounts for soil moisture storage

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Soil moisture holding capacity values were derived using the Riverside County and Orange County soil surveys performed by the NRCS (2006). Soil moisture capacity for each soil type was derived from the weighted average of the moisture capacity over the entire rooting depth.

The soil types then were divided into four categories based on soil moisture holding capacity: low, medium, high, and very high capacity. These categories were overlain with the soil hydrologic groups (A through D). Figure 35 shows the distribution of the resulting soil types; soils without soil moisture holding capacity data (unknown-UNK or not available-NA) are indicated.

The soil moisture balance was applied to each element to evaluate deep percolation. In brief, the soil moisture balance computes deep percolation on a monthly time step as the residual of the equation:

Effective precipitation - ET - soil moisture storage = deep percolation.

The rate of percolation was then applied to each area to calculate the total volume of recharge from deep percolation. This analysis resulted in a range of recharge estimates from less than one AFY of recharge in years of very low precipitation such as 1999 and 2002 to almost 10,000 AFY in 1993, the wettest year of the Study Period. These numbers were adjusted upward slightly (about 2 percent) in the groundwater model during model calibration as documented in Appendix C. Final recharge values for the purposes of the water balance are provided in the first row of inflows in Table 3-5.

As shown in the table, deep percolation of precipitation averages 1,753 AFY for the Temescal Subbasin, accounting for about 11 percent of the total average subbasin inflow and about 7 percent of average precipitation over the Study Period. During that time period, recharge from deep percolation ranged from 0 AFY to 12,694 AFY.

Return Flows
When land is irrigated, either for agricultural or urban landscape uses, most of the water is consumed through ET, but some water typically percolates to the underlying water table (depending on irrigation efficiency). Urban return flows may also include leakage from septic systems, municipal pipelines, or other urban uses. Figure 8 shows general land uses in the Study Area for 1984 and 2004. For the purposes of this analysis, any area that currently receives water from a municipality is considered part of the urban area.

Urban Return Flows
The analysis of urban return flows involved evaluation of 1) the amount of municipal water used outdoors and 2) the portion of outdoor water that percolates to groundwater. Urban outdoor water use generally involves landscape irrigation, with different customer types (e.g.,

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV single family homes, multiple family homes, commercial/industrial, and landscape irrigation) using a different portion of water outdoors. The distribution of customer types in Corona was obtained from the City’s Urban Water Management Plan (AKM, December 2005) and the amount of water served to each customer type was totaled. Estimation of the portion of water used outdoors for different customer types was derived from online DWR data on indoor/outdoor use for the North Riverside Detailed Analysis Unit from 1998-2004. While the relative portions of indoor and outdoor water use varied significantly from year to year, representative apportionments of 40 percent water use indoors and 60 percent water use outdoors was selected for multiple family homes. The apportionments for commercial customers and single family homes were similar. Applying these apportionments to the customer types and total water use, the portion of the total water supply used outdoors was estimated at 62.7 percent.

The urban return flow is the portion of applied irrigation water that exceeds the ET demands of the landscaping. For the purposes of this analysis, it was assumed that landscape irrigation water is not typically allowed to run off. Assuming that the average irrigation system is 90 percent efficient, then 10 percent of the applied water results in return flows to groundwater.

Thus for each year, 10 percent of the water used outdoors returns to the aquifer as percolation.

A similar calculation addresses additional urban areas served by the City of Norco and Home Gardens County Water District. Assuming that water use has a similar indoor/outdoor apportionment as in Corona, the same portion (62.7 percent) of total water supply used outdoors was assumed. Similarly, it was assumed that 10 percent of the outdoor use would contribute to return flows.

Using this methodology, urban return flows average 1,960 AFY related to the City water supply and an additional 86 AFY associated with other urban water suppliers.

Agricultural Return Flow
Estimation of agricultural return flows was based on the total amount of applied water and the consumed fraction, which represents the portion of applied irrigation that is consumed by the crop through ET. According to the DWR website, the average consumed fraction for citrus crops in the North Riverside DAU from 1998 to 2002 was approximately 74 percent. The remaining 26 percent, assuming no runoff, represents agricultural return flow.

Although agricultural areas are now mostly urbanized, some agricultural areas were persistent in early portion of the Study Period. However, these agricultural return flows are small and average about 61 AFY, or less than one percent of total inflows to the groundwater subbasin.

Total return flows for both urban and agriculture for Temescal Subbasin average about 2,108 AFY, about 13 percent of total inflows (Table 3-5).

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV Infiltration of Runoff
Although large amounts of natural runoff are generated in the Santa Ana Mountains west of the subbasin, most of this runoff is captured by the City’s stormwater management system and is unavailable for infiltration into the groundwater basin. Two large flood control (detention) basins, the Oak Avenue Basin and the Main Street Basin, have been constructed on two main drainageways along the mountain front. These basins are owned and operated by the Riverside County Flood Control and Water Conservation District (RCFCWCD). The locations of these basins are shown on Figure 7. The Oak Avenue and Main Street detention basins together cover 28 acres and hold 240 AF of water at full capacity (about 120 AFY each) (PBS&J, 2004). The basins are operated to only detain peak flows and only a small amount of runoff is estimated to infiltrate the basin floor. Almost all of the flow is diverted into lined canals that drain to a lined portion of Temescal Wash, which ultimately conveys the runoff out of the subbasin. The only other large drainageway that provides significant runoff to the subbasin is Bedford Wash in the south. Runoff on this drainage is also lost from the Temescal Subbasin as it flows into Temescal Wash.

A variety of methodologies were examined to estimate the potential annual recharge through the Oak Avenue and Main Street detention basins, resulting in a wide range of possible values from several hundred AF to several thousand AF. The evaluation considered the potential wetted area, potential infiltration rates, variations in annual runoff, and anecdotal information on the number of days that water is observed in the basins. It was determined from this review that reasonable ranges of potential infiltration varied considerably. However, since the basins are operated only to detain peak flows for a very short duration, it was determined that a conservative average of infiltration would be appropriate for the water balance. As such, an estimated infiltration volume of 480 AFY is used. This is equivalent to about 240 AFY for each basin and assumes that an amount equal to twice the total basin capacities infiltrates to groundwater each year. This is considered a conservative amount and represents only about five percent of the runoff that could potentially reach the detention basins. The 480 AFY is maintained for every year in the Study Period. (The slightly different amount of 478 to 482 shown on Table 3-5 reflects rounded values extracted from detailed groundwater model budget outputs).

Another area for potential infiltration of runoff exists on the eastern side of Temescal Subbasin where Temescal Wash enters the subbasin from Temescal Canyon (Figure 7). Here, surface water is allowed to infiltrate along a short segment of the subbasin before entering a lined culvert near Magnolia Avenue (lined portion shown on Figure 7). The area available for recharge has historically been characterized by high groundwater, apparently from surface water infiltration and fine-grained soils at the surface. As such, infiltration from the wash is thought to be small and has been calculated by applying Darcy’s Law to the subsurface area of Temescal Wash. This method results in an estimate of about 113 AFY of recharge, on average. In the absence of data that would be needed to allow this number to vary within a reasonable range of

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values, the average amount is applied to the water balance for each year of the Study Period as shown on Table 3-5.

Wastewater Recharge
Since the 1950s, the City has discharged treated wastewater into unlined ponds in northern Temescal Subbasin. The current locations of the percolation ponds are indicated on Figure 33 and a graph of wastewater discharge to the ponds is provided on Figure 21. The three ponds, referred to as Lincoln, Cota North, and Cota South, range in size from 2.95 acres to 6.81 acres, and together total 16.51 acres. Since 1984, effluent volumes have ranged between 3,649 AFY and 9,476 AFY (Figure 21).

A 2006 wastewater pond investigation documented high historical percolation rates, ranging up to 25 feet per day (AKM, 2006). During the time of the investigation, percolation had decreased to less than 1 foot per day due to the buildup of clogging particles and organic material on the bottom of the ponds. As recommended in the investigation report, removal of fines and other pond rehabilitation methods were implemented and the higher percolation rates were restored. The amount of evaporation from the ponds is estimated to be small, given the high percolation rates and observations by City staff (perhaps about 30 inches or 40 AFY) and was not incorporated into the recharge amounts. As such, recharge to Temescal Subbasin from the wastewater discharge ponds is estimated to range from about 3,650 AFY to 9,474 AFY and averages 7,112 AFY as shown in Table 3-5.

A portion of the wastewater from WWTP No. 1 is now treated to tertiary levels and used for park irrigation. This change in operation occurred late in the Study Period (2002) and adds only a small amount of additional return flows for 2003 and 2004. As such, it is considered to have a negligible effect on the water balance.

The City operates a third WWTP, located at the southeast corner of Temescal Subbasin.

Wastewater is used for local irrigation, with a small percentage discharged to Temescal Wash.

Any addition of wastewater does not affect the water balance as the recharge from Temescal Wash is limited by lined channels and has been estimated at 113 AFY as described above.

Subsurface Inflow
Subsurface inflow contributes to the Temescal Subbasin from adjoining basins. In addition, some inflow likely occurs along the entire circumference of the Study Area from adjacent bedrock. General areas where subsurface inflows and outflows occur are indicated conceptually by arrows on Figure 33 and described in more detail below.

Subsurface Inflow at Arlington Gap into Temescal Subbasin Water level contour maps indicate that groundwater enters the Temescal Subbasin from the Riverside-Arlington Basin through a narrow arm of the alluvial basin referred to as the

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV Arlington Gap (Figure 33). To estimate the volume of subsurface inflow across Arlington Gap, a calculation applying Darcy’s Law was conducted using the cross-sectional area of water-bearing sediments, estimated hydraulic conductivity values, and a measured hydraulic gradient of 0.0028 ft/ft across the subbasin boundary. This amount was used as a preliminary target for inflow at this boundary in the groundwater model. Inflow amounts estimated by the model are provided on Table 3-5 and average 3,620 AFY. The methodology of the initial Darcy’s Law calculation is described below.

As shown on cross-section C-C’ (Figure 14), the saturated aquifer thickness at Arlington Gap (as defined by DWR Well 193583) is about 400 feet and includes both the Channel Aquifer and underlying Tertiary-age sandstones. Applying a K value of 1,500 gpd/ft2 (200 ft/day) to the
Channel Aquifer and 100 gpd/ft2
(13 ft/day) to the Sandstone Aquifer results in an estimated average annual subsurface inflow through Arlington Gap of 4,869 AFY, of which 95 percent is represented by groundwater flow through the Channel Aquifer. This volume is in close agreement with a previous estimate by DWR of 3,000 AFY (DWR, 1947).

This value was tested in the groundwater flow model. As described in Appendix C, the boundary condition at the Arlington Gap was simulated with a specified head tied to water level data in a production well operated by Home Gardens Water District and located near the gap. As shown on Table 3-5, groundwater modeling indicated that inflow at the gap averaged 3,620 AFY over the Study Period and ranged from about 4,880 AFY to 2,225 AFY. Inflow decreased over the last few years in the Study Period in response to declining water levels in the well.

Subsurface Inflow from Surrounding Bedrock
Although limited by permeability, the bedrock surrounding the groundwater subbasin is recharged by small amounts of local precipitation. This bedrock groundwater system is in direct hydraulic communication with the groundwater in the alluvial basin over a relatively large area in the subsurface. Assuming that bedrock recharge and subsurface inflow will vary with precipitation, a soil moisture balance was calculated on the watershed area and the resulting groundwater recharge was used to approximate subsurface inflow. This amount was adjusted upward during model calibration.

Using these methods, about 783 AFY on average is estimated to provide subsurface inflow to the Temescal Subbasin from adjacent bedrock areas (Table 3-5). Although the amount was assumed to vary somewhat with precipitation, the lag time for inflow is unknown. Therefore a simplifying assumption was made using the average amount of inflow for each year in the Study Period as shown on Table 3-5. This inflow is relatively small and represents less than one percent of total precipitation in the watershed.

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Although most of the Norco area is included within the Temescal Subbasin boundaries as provided by DWR, there are significant unknowns associated with the area. Alluvial sediments appear to be thin and interrupted by bedrock highs. In addition, a groundwater divide is indicated by the data, with some groundwater flow indicated to the north toward the Santa Ana River and exiting the subbasin. The area that contributes groundwater flow to the Temescal Subbasin is uncertain. As such, the area was simulated in the groundwater model as providing a specified flow into the subbasin, derived from a simple calculation of subsurface inflow using Darcy’s Law.

That calculation indicated an inflow of approximately 52 AFY, an amount that was held constant as an annual subsurface inflow for Temescal Subbasin water balance (Table 3-5).

3.6.2.2. Outflows from Temescal Subbasin
Two outflows from the subbasin have been accounted for in the water balance. The largest of these is groundwater pumping, mostly from the City’s production wells. The other outflow component is the amount of groundwater that rises to surface water and contributes to the Santa Ana River outflow at Prado Dam. The incorporation of these components in the water balance is described below.

Pumping
Water pumped from the subbasin supplies water for urban, agricultural, and industrial uses. During the Study Period (1990 -2004), municipal uses account for 94 percent of the production. Pumping totals from the DMS were input into the water balance and the groundwater model. The monthly distribution of pumping used in the groundwater model was determined from the time period when monthly data were available and average monthly percentages were applied to annual totals.

As shown on Table 3-5, pumping represents the primary outflow in the water balance.

During the Study Period, production in Temescal Subbasin averaged 12,601 AFY and ranged from 7,294 AFY to more than 20,000 AFY. In general pumping has increased during the Study Period with a significant increase beginning in 2002 when pumping exceeded 19,000 AFY. From 1990 to 2002, pumping averaged 10,821 AFY. From 2002 through 2004, average pumping increased more than 80 percent to 19,724 AFY. Section 3.4 provides a more complete discussion of pumping in the Study Area.

Subsurface Outflow
Subsurface outflows from the Temescal Subbasin are interpreted to occur at two main locations: contribution to baseflow at the Santa Ana River and contribution to Temescal Creek baseflow near Bedford Canyon. Methodology was similar to the calculations for subsurface inflow previously described.

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV Subsurface Outflow from Temescal Subbasin at Santa Ana River Groundwater level contours in the Study Area (Figures 26 and 27) indicate that groundwater flows out of the Temescal Subbasin in the Prado Management Area (flood control basin) of the Santa Ana River (northern portion of the Study Area). Groundwater rises and discharges from the valley via surface water flow at Prado Dam. However, to incorporate subsurface data and provide a more reliable estimate of this amount, the outflow calculation was initially estimated at a location judged to be just upgradient of groundwater discharge to surface water.

To estimate the annual volume of subsurface outflow from Temescal Subbasin, the same methodology and K values were applied as those used for the Channel Aquifer and Tertiary deposits in the Arlington Gap inflow calculation. A hydraulic gradient of 0.0009 ft/ft was measured across the northwestern boundary of Temescal Subbasin, and an average saturated thickness of 600 feet was assumed for the Tertiary deposits. Results of the calculation using Darcy’s Law indicate that the estimated annual subsurface outflow from Temescal Subbasin is 4,352 AFY, of which 90 percent is represented by groundwater outflow through the Channel Aquifer. This volume is within the previously estimated range of 3,000 to 9,000 AFY made by USGS in a study of groundwater outflow to Prado Management Area (French, 1972).

In order to analyze the variability of this outflow, output from the calibrated groundwater model was reviewed. This boundary was simulated as a general head boundary based on elevation of the pool at Prado Dam. Details of this boundary condition are provided in Appendix C. The model output agrees closely with the estimates from the calculations described above.

These amounts are provided as outflow from the basin and are listed in Table 3-5. As shown in the table, average outflow to surface water is estimated at 4,062 AFY and varies within a relatively narrow range from 3,944 AFY to 4,123 AFY.

Subsurface Outflow from Temescal Subbasin along Bedford Canyon Subsurface outflow from Temescal Subbasin at the subbasin southeast corner is interpreted to occur in the alluvial sediments of Bedford Canyon. According to hydrographs in this area (e.g., Figure 25 with location on Figure 22), groundwater discharge to surface water occurs in this area as Temescal Wash enters Temescal Canyon. Runoff contributing to infiltration along Bedford Wash is not accounted for in the water balance and is assumed to exit the subbasin as either groundwater or surface water. Because this area does not impact the remaining portions of the water balance, inflows and outflows are not included for this area.

Total Outflows
As shown on Table 3-5, total outflows from Temescal Subbasin, including pumping and subsurface outflow, average 16,663 AFY, about 642 AFY larger than average inflows. Outflows were generally less than inflows on an annual basis for most of the early years of the Study Period.

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV In recent years, outflows have exceeded inflows, especially in 2002-2004 when pumping amounts increased to about 20,000 AFY.

3.6.2.3. Change in Groundwater Storage in Temescal Subbasin Groundwater in storage refers to the volume of groundwater in the saturated aquifers from the water table down to a level where groundwater extraction is limited by factors such as deteriorating water quality, insufficient permeability, or excessive lift costs. The amount of groundwater in storage changes from year to year with climatic variation and basin operation (i.e. pumping). The water balance provides a regional assessment of the change in storage by estimating how much water is entering and leaving the groundwater basin on an average basis and serve as an initial guide to the average amount of groundwater that can be extracted without significant depletion of groundwater. The balance is only an initial indication; changes in groundwater storage from pumping are controlled by pumping locations, boundary conditions, and the ability of pumping to capture inflows and outflows in the basin.

The change in groundwater storage predicted by the water balance is the subtraction of outflows from inflows. Although this calculation can be made annually, the change in storage over the Study Period is more representative of groundwater basin response to variable hydrologic conditions over time. The cumulative change in storage over the Study Period is also tabulated on Table 3-5 and represented by the graph at the bottom of the table.

For the Temescal Subbasin, the change in groundwater storage over the Study Period is estimated at -9,627 AF, an average deficit of about -642 AFY. The graph on Table 3-5 tracks the cumulative change in groundwater storage for each year of the Study Period (blue line on the graph on Table 3-5). The change in storage became negative only in the last two years of the Study Period, a time when average inflows were a little less than average (especially in 2003), but outflows increased more than 40 percent from average outflows due to increased pumping.

The deficit in cumulative change in storage is judged reasonable given that water levels have generally declined from 1990 to 2004. However, given that the pumping is primarily in the Channel Aquifer in the northern portion of the subbasin (Figures 16 and 18), the decline in water levels has not likely occurred on a basin-wide basis. Hydrographs in the Channel Aquifer indicate a water level decline of about 10 feet over the Study Period (e.g., Figure 23). The Channel Aquifer extends over about 3,000 acres and has an estimated specific yield of about 20 percent.

Using these data and assuming an aquifer-wide water level decline, the change in storage is estimated at about -6,000 AFY. This amount is reasonably close to the average estimated change in storage in the water balance of -9,627 AFY (Table 3-5).

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3.6.3. Coldwater Subbasin Water Balance
The water balance for the Coldwater Subbasin was initially conducted through an independent evaluation of the different components of inflow and outflow from the subbasin. The resultant change in storage was checked for reasonableness by estimating the change in storage indicated by water level fluctuations over the Study Period. The methodology for each of these steps is summarized below. Table 3-6 summarizes the water balance.

Water Year 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Ave.

INFLOWS
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TOTAL INFLOWS (AFY) 2,102 6,283 6,273 11,525 2,733 6,876 2,376 2,751 8,843 1,099 2,709 5,270 1,645 5,571 7,023 4,872OUTFLOWS 3XPSLQJ           
   
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TOTAL OUTFLOWS (AFY) 4,600 5,630 6,758 8,380 6,176 7,906 7,123 6,646 9,551 9,231 6,082 4,377 3,984 3,877 4,635 6,330 Table 3-6
Water Balance Summary for Coldwater Subbasin
Cumulative Change in Storage (AF) -2,498 -1,845 -2,329 816 -2,627 -3,657 -8,404 -12,299 -13,007 -21,140 -24,513 -23,619 -25,958 -24,264 -21,876 -10,000-15,000-20,000-25,000-30,000
-5,000
0 5,000
15,00010,000
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Inflows / Outflows (AFY)
Change in Storage (AF)
Water Year
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3.6.3.1. Inflows to Coldwater Subbasin
Deep Percolation from Rainfall
Deep percolation was calculated over the Study Area using two steps: a runoff analysis and a soil moisture balance, using the same methodology described for the Temescal Subbasin water balance. As shown in Table 3-6, deep percolation of precipitation is estimated to average 388 AFY for the Coldwater Subbasin, or about 8 percent of the total inflows. The amount is variable from year to year and is most significant during wet years (e.g., 1,424 AFY in 1993). The amounts are slightly higher than would be anticipated for average rainfall due to the open pits, permeable surface soils, and relatively un-vegetated industrial area of gravel mining in the southern portion of the subbasin.

Infiltration of Runoff
For Coldwater Subbasin, large amounts of runoff are generated in the Santa Ana Mountains adjacent to the basin and, unlike Temescal Subbasin, are not funneled into concrete lined culverts. The amount of water available for recharge varies annually with changes in rainfall and runoff amounts. Runoff was estimated from the contributing watershed using the same Curve Number methodology described in the Temescal Subbasin water balance.

Runoff into the Coldwater Subbasin is subject to ET, infiltration, or continued surface flow to the local drainageway of Temescal Wash. The contributing watershed to Coldwater Subbasin is comprised of about six individual watersheds. From south to north these are Mayhew Canyon, Coldwater Canyon, Anderson Canyon, Bixby Canyon, Brown Canyon, and smaller drainages south of Bedford Canyon. The northern subbasin is more developed and contains a stormwater control system. Therefore, it was assumed that runoff from the northern watersheds (i.e., Anderson, Bixby, Brown, and smaller drainages) do not significantly contribute to groundwater recharge. Runoff from Coldwater and Mayhew canyons, however, are diverted and managed for recharge and, as such, contribute significant amounts of inflow into the subbasin.

Runoff from these two individual watersheds was based on the percentage of the entire contributing watershed area represented by Coldwater and Mayhew watersheds.

Runoff from Coldwater and Mayhew canyons is captured and diverted to gravel pits or spreading areas for groundwater recharge in the subbasin (MWH, 2004). The City has constructed berms and in-stream diversion structures along Coldwater Wash (assisted by Chandler Inc., the operator of the adjacent sand and gravel mining operation). Numerous berms capture streamflow and allow for infiltration into the permeable gravels of the streambed.

EVMWD diverts varying amounts of surface water runoff along Mayhew Wash to gravel pits for enhanced groundwater recharge. Some portion of the diverted water may also provide irrigation to agriculture users in the subbasin, but the amount dedicated to such use is not documented (MWH, 2004).

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV Although most of the Coldwater and Mayhew runoff is conserved, wet years generate large amounts of water that bypass the recharge structures and flow to Temescal Wash (in some years causing flooding of local roads). For purposes of the water balance, in years with a total of more than 6,000 AFY of runoff it was assumed 85 percent of the runoff from Coldwater and Mayhew basins infiltrate to the groundwater system leaving about 5,000 AF over the study period that could not be captured. In years generating less than 6,000 AFY, 100 percent of the runoff was assumed to infiltrate, although some large storms may not be fully captured. In addition, the ET demands of the land cover were already taken into account in the runoff calculations. The total runoff resulting in groundwater recharge is estimated to average 4,009 AFY (Table 3-6).

Runoff and recharge vary significantly from year to year with changes in precipitation.

Subsurface Inflow from Surrounding Bedrock
Subsurface inflows from bedrock were estimated for the Coldwater Subbasin using a similar methodology as the Temescal Subbasin water balance. Inflow is estimated to average only about 50 AFY (Table 3-6). This component represents the only subsurface inflow component applicable to Coldwater Subbasin.

Wastewater Recharge
Glen Ivy Springs operates a spa facility in the Coldwater Subbasin. The facility discharges approximately 90 AFY (per their NPDES permit) to a diversion channel that funnels discharge into Coldwater Wash (RWQCB, 2004). This flow is retained by the City’s in-stream berms and is assumed to infiltrate to the groundwater. No other discharge of wastewater is known to exist in the Coldwater Subbasin.

Return Flows
Water supply available for return flows in the Coldwater Subbasin originates from several water sources. Total water supply includes groundwater pumping within the subbasin, imported water from LLWD (purchased from WMWD through Metropolitan), imported nonpotable water by EVMWD from Corona Lake, and imported water from deep pumping by Glen Ivy Hot Springs (below the potable groundwater subbasin). A portion of the subbasin pumping is exported and not available for return flows within the subbasin. Groundwater pumping by the City of Corona is exported to the Temescal Subbasin. In addition, a portion of the EVMWD pumping provides water supply to the Butterfield Estates trailer park, just outside of the subbasin.

The amount of exported pumping was not included in the return flow estimates for the subbasin.

Urban Return Flow
Urban return flows were estimated for the Coldwater Subbasin using the same methodology as used in the Temescal Subbasin. Land use data from DWR were used to identify changing urban areas during the Study Period. Urban water use was derived from total pumping plus imported water less basin exports. These exports include pumping by the City of Corona and

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV EVMWD, who provides water supply to Butterfield Estates located just outside of the subbasin boundary. Assuming that water use has a similar distribution as in the City of Corona, the same portion (62.7 percent) of total water supply used outdoors was assumed. Similarly, it was assumed that 10 percent of the outdoor use would contribute to return flows. As shown in Table 3-6, this methodology indicates that urban return flows in the Coldwater Subbasin average about 150 AFY.

Agriculture Return Flow
As documented in Table 3-6, agricultural return flows contribute only minor amounts of inflow to groundwater due to decreases in agriculture land use. Agriculture return flows in Coldwater Subbasin averages 30 AFY, but is thought to be higher prior to the beginning of the Study Period (before 2000).

Industrial Return Flow
Some industrial return flows are anticipated from sand and gravel mining use of groundwater. Groundwater is used to wash fines from the excavated sediments, and a portion of this water is returned to the gravel pits. Gravel mining operations are active in Coldwater Subbasin during the entire Study Period; however, pumping totals are small relative to pumping amounts by the City and EVMWD. Evaporation from the gravel pits and other losses associated with the mining operation are estimated to be small compared to the amount of water allowed to infiltrate back to the groundwater system. It was assumed 90 percent of industrial pumping becomes return flows.

Total Inflows
Total inflows for the Coldwater Subbasin are much lower than inflows into the Temescal Subbasin due to the smaller areal extent and relatively closed nature of the subbasin. Accounting for all of the inflows discussed above, total inflows are estimated to range from 1,099 AFY to 11,525 AFY and average 4,872 AFY over the 2,176 acres in the subbasin (Table 3-6).

3.6.3.2. Outflows from Coldwater Subbasin
Outflows from the subbasin include groundwater pumping and subsurface outflow to the Bedford Subbasin under certain conditions. Pumping represents the primary outflow in the water balance (Table 3-6). During the Study Period, production in Coldwater Subbasin averaged 6,284 AFY (Table 3-6). Section 3.4 provides a more complete discussion of pumping in the Study Area.

Assumptions regarding the outflow to Bedford Subbasin are described below.

Subsurface Outflow from Coldwater Subbasin to Bedford Subbasin The North Glen Ivy fault forms the subbasin boundary between Coldwater and Bedford subbasins. Details of where and under what conditions groundwater moves across the fault are not well understood. However, it is likely that when groundwater outflow occurs, it does so in the

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central portion of the subbasin, based on natural surface water drainageways, topography, and the incised nature of shallow sediments and bedrock in the area. Estimates of subsurface outflow across the fault have been made by MWH (2004), which were interpreted to occur only in times of relatively high water levels. Those estimates were determined to be reasonable for this water balance and are incorporated for years in which outflow is estimated to occur (Table 3-6). These outflows are estimated to range between 50 AFY and 280 AFY and average only 46 AFY over the Study Period (Table 3-6). Declining water levels have resulted in a relatively closed basin over the last few years and it is assumed that during this time, subsurface outflow does not occur.

As shown on Table 3-6, total outflows from the Coldwater Subbasin are estimated to average 6,330 AFY over the Study Period. This amount exceeds inflows by an average of 1,458 AFY.

3.6.3.3. Change in Groundwater Storage in Coldwater Subbasin The change in storage in the Coldwater Subbasin indicates a larger deficit in storage (Table 3.6) than occurred in Temescal Subbasin over the Study Period. The water balance indicates a cumulative loss of groundwater storage of about -21,876 AFY, an average deficit of about -1,629 AFY. To compare this deficit with declining water levels, a groundwater storage change was computed using water levels and subbasin hydrographs (e.g., Figure 24). These graphs indicate a decline in water levels of about 100 feet from 1990 to 2004, likely concentrated in the western subbasin where pumping occurs. Using a specific yield of 20 percent in the sediments where the decline has occurred and applying the deficit over approximately one-half of the subbasin, the change in storage over the Study Period is estimated at -21,760 AF. This estimate is consistent with the deficit predicted from the water balance. In addition, the graph on Table 3.6 showing the cumulative change in storage mimics the shape of the water level hydrograph on Figure 24 for the Study Period. This agreement provides additional confirmation of the average water balance estimates.

3.6.4. Water Balance Discussion
The results of the water balances indicate a negative change in storage at average pumping conditions in both Temescal and Coldwater subbasins over the Study Period. This indicates that more water is being withdrawn from the subbasins than will be naturally replenished over time, a condition referred to as overdraft. The water balances also provide a preliminary assessment for the operational range of the subbasins. Assuming no other significant changes in the water balance, average pumping totals of about 12,000 AFY in Temescal Subbasin indicate no significant loss of groundwater storage. For Coldwater Subbasin, average pumping totals around 4,500 AFY also indicate no significant loss of groundwater storage. These estimates are simplistic and do not take into account other changes in the water balance resulting from pumping decreases (such as potential increases in subsurface outflow or reduced return flows).

Nonetheless, they provide a preliminary estimate for guiding management scenarios.

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An evaluation of current and future water demand as well as additional sources of water supply are provided in the following section.

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4. City of Corona Water Demand and Supply
In order to manage the groundwater resource and provide for planned growth associated with build out, the City has examined current and future demand as well as water supply from other sources. Demand increases are categorized by water use type through 2030. The City is also taking measures for water conservation and demand management. Collectively, these data are summarized in previous City evaluations presented in their Water Master Plan (AKM, April 2005) and their Urban Water Management Plan (AKM, December 2005) and have been updated for this GWMP.

4.1. Current and Future Demand
The City has a wide array of water users, classified by sectors: residential single-family, residential multi-family, commercial, industrial, institutional/governmental, landscape, and agricultural. Total current water demand is 45,600 AFY (not including water transfers wheeled to the City of Norco and Western Municipal Water District in Calendar Year 2007). This represents a 15 percent increase from 2000 usage of 39,634 AFY.

Ultimately the City anticipates a total demand of 51,631 AFY by the year 2020 (projected City build out). In addition to use demand, the City must also account for spent filter backwash (from the Lester and Sierra del Oro water treatment plants) and brine reject (from the Temescal Desalter), which is currently 2,300 AFY. This amount is expected to increase to 2,954 AFY by 2020. A brief summary of the categories of water users and expected changes in the future are described below and summarized on Table 4-1.

Residential – Single-Family
In the City of Corona, a single family residential customer averages 3.5 persons per connection. Corona is a suburban community with approximately 30 percent of its acreage comprised of residential use. Total system consumption for this sector was 22,863 AF in 2000.

Current consumption levels are at 28,000 AFY and are expected to ultimately increase 16 percent by year 2020 to 32,471 AFY. At build out, the single family residential water use will represent 63 percent of the total demand.

Residential – Multi-Family
Multi-family residential customers average 3.35 persons per household. Like the singlefamily residential sector, the multi-family sector is expected to experience significant growth over the next 15 years, but total demand is significantly less than for the single family sector.

Currently the multi-family residential sector is using 4,000 AFY from 1,600 connections and is expected to increase to a total sector usage of 9,048 AFY with 3,601 connections by 2020.

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The City has a large mix of commercial customers that are categorized as general commercial, office professional, and downtown commercial. General commercial accommodates many commercial uses that service the community such as department stores, banks, supermarkets, and retail stores. Office professional includes general business, finance, insurance, real estate, and medical offices. Downtown commercial is intended to create a pedestrianoriented street environment with such uses as retail shops, offices, services, cultural facilities, entertainment, and civic and public uses. Current commercial water use has grown about 18 percent to 1,700 AFY since the year 2000 and will ultimately grow to 1,980 AFY by 2020.

Industrial Sector
Corona has a large industrial base that is centered on high-tech and manufacturing. The industrial sector has increased water usage by 19 percent from 2000 to present and accounts for 3,200 AFY. This usage is expected to grow to 3,679 AFY by 2020.

Institutional/Governmental
The City has a stable institutional and government sector, primarily local government, schools, visitor services, and a public hospital. This sector will keep pace with the growth of the city.

Landscape
Landscape water use would be expected to increase with the growth of the city, fueled mainly by residential development. But increased efficiency and landscape conversions occurring at existing parks, golf courses, and cemeteries should help offset new demand and result in decreased water use in the future. Additional information on the City’s water conservation and demand management efforts are described in Section 6.1.9 (management strategy 25).

Agriculture
Agricultural water demand has declined over the past 20 years, but is projected to remain fairly constant over the next 20 years. The City’s General Plan reflects local citizen interest in space, quality of life, environmental values, and the long-term maintenance of a diverse economic base. It is projected that these objectives will be met with urban uses and open space rather than with agricultural land.

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City Current and Future Demand (AFY)
Year
Water Use
Sectors
Single
Family
MultiFamily
Comm. Ind. Special
Acct.

Instit./
Gov.

Landscape
Ag. Total
2000
No. of
accounts     
   

Deliveries
AFY    
     


2005
No. of
accounts          Deliveries
AFY 
    
   

2010
No. of
accounts 
  
      
Deliveries
AFY 
     
   
2015
No. of
accounts  
       

Deliveries
AFY          2020
No. of
accounts          Deliveries
AFY 
 
 
  
   
2025
No. of
accounts          Deliveries
AFY 
 
 
  
   
2030
No. of
accounts          Deliveries
AFY 
 
 
  
   

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4.2. Water Conservation and Demand Management
The City recognizes the importance of continuing current efforts for conserving water and decreasing demand. As such, they became a signatory to the California Urban Water Conservation Council (CUWCC) MOU in 1996 and are committed to implementing the 14 Best Management Practices (BMPs) in the MOU. The City has retained a Water Conservation Coordinator to lead these efforts.

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV The City and the Water Conservation Coordinator have developed and implemented an extensive water conservation education system, including a dedicated education center at the City’s treatment plant. Materials and information on water conservation have been prepared and presented in schools (K-12) across the City. Last month alone, the Coordinator interacted with about 500 children in connection with numerous education programs, a total representative of a typical month. These programs not only provide basic information to younger children (typical of many programs), but also specifically develop material to target grades 6 through 12. It is more difficult and time-consuming to prepare materials for the older grade levels because much more detail is required. However, targeting the older children provides a higher level of education and potentially more benefits in promoting good stewardship of their water resource.

The City also sponsors numerous events that are focused on water. In May, the City held their third annual Water Festival, an event that attracts about 1,500 attendees. The City has also developed a Water Wise landscape award that is publicized to encourage residential responsibility.

In addition to their own events and programs, the City participates in water conservation programs developed by Metropolitan and WMWD.

Since the single-family and multi-family residential sectors represent the largest growth in demand over the next 15 years, the City of Corona has implemented a water use efficiency program to offset increasing water demands. The program strives to increase water use efficiency by supporting water use surveys for residential and public facilities, ultra low flush toilet replacement, and educational/informational programs. Increased efficiency and landscape conversions occurring at existing parks, and golf courses should help offset new demand and result in decreased future water use for landscape irrigation.

4.3. Supply
The City water system contains potable water from two sources: local groundwater and imported water. The groundwater source includes the three groundwater subbasins described in this GWMP. The source of the imported water is the Colorado River and State Water Project water supplied by Metropolitan and purchased through WMWD. The supply obtained from each groundwater well and imported water sources from 1990 through 2007 is summarized in Table 4- 2 and discussed in the following sections.

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Water Production and Purchases (AFY)
Source of Supply Well # 1990 1995 2000 2002 2004 2007
Coldwater Basin      
  
   
  
    
      
 B B 
 
  
Subtotal 2,086 4,267 3,999 2,579 2,780 3,517
Temescal Subbasin
(including Well 4 in
Bedford Subbasin)
      
      
      
$     

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$      
      


      
      
$ 
 



  

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Subtotal 6,111 6,663 9,123 17,217 19,235 18,800
Metropolitan Raw
Water
Metropolitan
Treated Water
:5±
   
   
:5±
      
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:5± B 
  
  

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Subtotal 17,496 15,294 26,512 23,901 22,040 24,557
Total 25,693 26,224 39,634 43,697 44,055 46,874

4.3.1. Groundwater Basins
The City relies on the underlying groundwater for an increasing percentage of its total water supply. The City currently maintains and operates 21 production wells for its municipal potable water supply: 18 wells in the Temescal Subbasin, 3 wells in the Coldwater Subbasin, and 1 former well in the Bedford Subbasin (recently abandoned).

As previously discussed, most of the City’s production is from the Channel Aquifer in the Temescal Subbasin. Typical depths for the City’s wells in the Temescal Subbasin range from about 200 to 500 feet deep with screens as shallow as about 100 feet below ground surface. The combined capacity of the 18 Temescal Subbasin wells is approximately 23,405 gpm (about 38,000 AFY). Seven of these wells have been installed in the past five years (Wells 22, 23, 24, 25, 26, 27, and 28) to replace older wells and provide additional supply to the Temescal Basin Desalter for the improvement of water quality in the region.

The City pumps about 3,500 AFY from the Coldwater Subbasin from three active wells.

The City also acquired the rights to the surface flows of Coldwater Canyon in 1964 when it purchased the assets of the Corona City Water Company (CCWC). To meet regulatory

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV requirements, runoff from the canyon is recharged through in-stream percolation ponds along Coldwater Wash. The City of Corona and EVMWD pump most of the groundwater extracted from the Coldwater Basin.

The City does not currently produce groundwater from the Bedford Subbasin, but has done so in the past at Well 4 located near WWTP 3. Although this well has been recently abandoned, the City has plans to re-drill in the Bedford Subbasin for future water supply.

The three subbasins from which the City extracts groundwater are not adjudicated.

However, under a stipulated judgment entitled Orange County Water District vs. City of Chino, et al. (1968), the City, with other purveyors upstream of Prado Dam, have the right to use all surface and groundwater supplies originating above Prado Dam without interference from water purveyors downstream of Prado Dam, provided that the average adjusted base flow at Prado Dam is at least 42,000 AFY. WMWD is one member of a watermaster panel that administers provisions of this judgment. To ensure provisions of the judgment, the City is required to provide a base flow of 1,625 AFY (adjusted for water quality) from the City’s WWTP.

The City of Corona has increased the production of local water relative to imported water.

In 2000 the groundwater production accounted for 33 percent of the total supply. Last year in 2007 groundwater accounted for 50 percent of total water supply (not including water supplied to the City of Norco or WMWD), which is a 51 percent increase in local production since 2000.

Looking forward, Corona would like to maintain an approximate 50 percent groundwater allocation for their water supply by year 2020. Based on the water balance provided in Section

3.6, current groundwater basin conditions in Temescal and Coldwater subbasins cannot support this level of production without significant enhanced recharge.

4.3.2. Imported Water
The City's imported water is supplied by Metropolitan and purchased through WMWD, a member agency of Metropolitan. The imported supply is delivered to the City through two separate pipelines. The Lower Feeder Pipeline supplies raw imported water to the City's Lester and Sierra del Oro water treatment plants (WTPs) through metered turnouts (WR-19 and WR-33 respectively). The Mills Pipeline delivers treated imported water directly to the City through a metered turnout (WR -24).

Turnout WR-19 is located in Chase Drive, east of Lester Avenue. The flow from this turnout is typically delivered by gravity to the City's Lester WTP located on Rimpau Avenue.

The Lester Raw Water Booster Pump Station provides additional pumping head when the pressure in the Lower Feeder is not sufficient to deliver flow to the plant by gravity. This treatment plant has a firm treatment capacity of 25 million gallons per day (MGD) with a peak capacity of 30 MGD. In addition, current delivery constraints limit the treatment plant’s capacity to 30 MGD. The hydraulic grade line at the turnout depends on the operation and flow through

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Turnout WR-33 is connected to the Lower Feeder near Montana Ranch Road. WR-33 delivers raw water to Sierra del Oro (SDO) WTP located on Wilderness Circle via the SDO Raw Booster Station located on Montana Ranch Road. The SDO WTP has a firm treatment capacity of 6 MGD (9.1 MGD Peak). The estimated operating hydraulic grade elevation at this turnout is 1,070 feet msl, based upon the observed inlet pressure of 56 pounds per square inch (psi) and turnout elevation of 940 feet msl.

Turnout WR-24 is connected to the Mill’s Pipeline at Temescal Canyon Road and La Gloria Road. The turnout is at elevation 890 feet msl and provides water to the City at a minimum hydraulic grade elevation of 1,380 feet msl. Corona’s maximum allotment for this turnout is approximately 6.5 MGD (10 cfs). WR-24 delivers potable water to Zones 3, 4 and 5.

Turnout locations and capabilities are summarized in Table 4-3.

Table 4-3
Imported Water Service Connections
Service Connection Location
Elevation
(Ft, msl)
Approx. Hyd.

Grade Elev.
(Ft, msl)
Max.

Capacity
(MGD)
Service
Zone(s)
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The total combined supply capability of imported water is approximately 45.6 MGD (about 31, 666 gpm), which exceeds the estimated ultimate peak hour demand of 33.8 MGD (23,440 gpm). Assuming total capacity and available water, imported water supply could be as high as about 47,000 AFY.

Recent developments have added some uncertainty regarding the reliability of imported water from the State Water Project (SWP). A U.S. District Court decision in May 2007 ruled that the existing 2005 biological opinion for Delta smelt, issued by the U.S. Fish and Wildlife Service (USFWS), did not comply with the federal Endangered Species Act. The biological opinion

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guides pumping operations for the SWP to ensure no long-term jeopardy to the health and habitat of Delta smelt. The Court ordered certain interim “remedies” or actions to protect endangered fish species until a revised biological opinion is prepared by the USFWS. These remedies collectively amount to cuts in statewide water supply for about one year (Calendar Year 2008). The long-term effect of the court decision is not known, but with these cuts, the availability of SWP water may be impacted, especially during drought cycles. Even though the City relies less on SWP for its imported water supply, these changes may result in increased competition for other imported water supplies.

4.3.3. Recycled Water
The City’s recycled water system will ultimately consist of four service zones, four reservoirs, four booster pump stations, four pressure reducing valves and one surge anticipator valve, a portion of which is currently under construction. The existing recycled water distribution system consists of approximately 180,183 feet of pipe ranging from 4-inches to 24-inches in size.

Approximately 31,531 feet of pipe is expected to be added to the system in the future.

The City expects recycled water demand to increase in the future and can currently supply up to 4,200 gpm (about 6,780 AFY). In addition, the source is seen as a reliable supply for recharging the groundwater subbasins to increase yield. Future expansions at the City WWTPs will increase recycled water supply by an additional 7,630 gpm (about 12,310 AFY), bringing the total future capacity to 11,830 gpm (about 19,090 AFY). These expansions will allow for increased recycled water for both irrigation and enhanced groundwater recharge (through basins and/or wells).

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5. Basin Management Objectives
The City recognizes the need for more active groundwater management to maintain and protect the resource for reliable water supply. Establishing basin management objectives (BMOs) can provide a clear direction for the implementation of management activities such as pumping distribution and enhanced groundwater recharge. BMOs outline the water level and water quality conditions that are acceptable in the basin, address conditions that need to be remedied, and identify changes in the groundwater basin that need to be avoided. In consideration of the state of the groundwater basin and the water supply goals of the City, the following BMOs are proposed.

5.1. Manage Groundwater Basin in a Sustainable Manner
The City wishes to use groundwater as a long-term reliable supply and recognizes the importance of sustainability. As such, the City supports the operation of the basin such that natural or enhanced recharge can replenish the groundwater extracted on an average basis over time. This management objective recognizes the current overdraft conditions in the subbasins and proposes to adopt management strategies to move toward more sustainable use.

The perennial yield of a groundwater basin is defined as the amount of water that can be extracted on an average basis over time without adverse impacts (Todd and Mays, 2004). Because the term adverse impacts is defined on a site-specific basis and may change over time, the perennial yield of a groundwater basin may also change over time. The term sustainable yield suggests that a net decline in groundwater storage over some period of time such as an average hydrologic cycle would be an adverse impact and the goal of sustainability is to eliminate such declines. The sustainable yield of a groundwater basin is difficult to define in the absence of reliable, long-term data on all aspects of the water budget. In addition, the sustainable yield is not a fixed amount and can be altered by changes in inflows or outflows to the basin. This GWMP provides preliminary estimates on sustainable yield, but the actual yield will be better defined in the future as changes in operation and improved monitoring concurrently occur.

5.2. Prevent Substantial Water Level Declines in Channel Aquifer Given the unconfined nature, shallow occurrence, and relatively limited thickness of the Channel Aquifer, water level declines are especially problematic. As water levels drop, the aquifer is de-watered and well yields are adversely affected. Some water level declines can be tolerated during drought conditions if groundwater is sufficiently replenished when recharge is available. As a preliminary operational guideline, the aquifer should be operated to prevent water level declines below about 50 percent of the total aquifer thickness. Assuming an average thickness of about 200 feet, then water levels should be maintained at least 100 feet above the bottom of the aquifer. The bottom of the aquifer is estimated to occur between about 400 to 450

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV feet msl, so water levels should be maintained above 500 to 550 feet msl across the aquifer. This lower limit is consistent with the range of historical water levels in the area.

5.3. Protect Groundwater Quality in Unconfined Aquifers The unconfined aquifers on which the City relies are subject to impact from the quality of water infiltrating from the surface. Given the urbanized setting over the Channel Aquifer, this area is especially sensitive to future impact. Once water quality has been compromised, the resource may be subject to loss of use or expensive water treatment processes.

5.4. Maintain Required Outflow at Prado Dam
The stipulated judgment in Orange County Water District vs. City of Chino, et al. (1968) requires the City to contribute a baseflow of 1,625 AFY (adjusted for water quality) to the Santa Ana River. Depending on water quality the amount may be as high as 2,240 AFY (Boyle, 2001).

Current subbasin outflow is significantly more than required, but basin management activities may reduce the total amount. The City wants to ensure that the required outflow continues to be provided in compliance with the judgment.

5.5. Monitor Groundwater Levels, Quality, and Storage
In order to continue to analyze current groundwater conditions and track changes in the groundwater basin resulting from active management activities, the City would like to expand and improve their monitoring program. The monitoring program would improve the understanding of groundwater level fluctuations, potential impacts to groundwater quality, and changes in groundwater storage across the three subbasins of interest.

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6. Basin Management Strategies

6.1. Identification of Management Strategies
The following groundwater management strategies have been identified as having potential for improving the management of the groundwater basins. The 24 strategies have been grouped into seven categories involving similar facilities or locations, and are numbered for easy reference. The eight categories of management strategies are listed below:
• New and Replacement Water Supply Wells and Wellhead Treatment • Groundwater Treatment Process Improvements
• Groundwater Monitoring Program
• Enhanced Groundwater Recharge
• Expanded Use of Recycled Water
• Use of Imported Water
• Wastewater Pond Maintenance
• Coordination with Regulatory Agencies
Specific strategies are listed in Table 6-1 and described in the following text. The strategies are not listed in order of priority. In addition, some strategies overlap those in other categories. For example, injection wells for groundwater recharge are listed as both a strategy for enhanced recharge and a strategy for expanded use of recycled water.

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Management Strategies
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6.1.1. New and Replacement Water Supply Wells and Wellhead Treatment
Strategies under this category provide for re-distribution of pumping within the Temescal Subbasin aquifers, use of poorer-quality groundwater, capturing a larger percentage of groundwater discharge from the subbasin, and replacing older less-efficient wells. Facilities

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1. New Water Wells
In order to more effectively distribute pumping throughout the aquifer, the City is currently planning for the construction of one new water production well every two to three years.

These new wells will enhance the City’s production of groundwater during drought periods when imported water is limited. Additional wells will also allow for more flexibility in the maintenance of water levels in the Channel Aquifer. Wells will be located to pump within permeable aquifer zones while minimizing well interference. Wells will also be located to capture a portion of groundwater discharge that is currently exiting the groundwater basin, thereby increasing the basin yield.

2. Replacement Water Wells
The State Controller’s Office lists the service life of water wells at 30 years. The City has eight water wells that have exceeded the 30-year service life. The City plans for one replacement water well about every three years.

3. Rincon Groundwater Treatment Project (wells plus treatment) The Rincon project is in an area of historically high nitrate concentrations and the addition of wellhead treatment facilities will allow for expanded use of this poorer quality water.

This project is scheduled for fiscal year of 2015-2016 at a projected cost of $15,000,000, reflecting the added costs of groundwater treatment. The proposed location is in the vicinity of Rincon Street and Alcoa. The project will yield 5,000 AFY to the current potable water system.

The specific components of the project are three new wells, a raw water pipeline, a treatment process involving selective resins or best available technology (BAT) to reduce nitrate concentrations, a 6,500 sq. ft. building to house the process, a product pipeline, property acquisition, and brine disposal to the Santa Ana Regional Interceptor (SARI) pipeline.

4. Wellhead Treatment for Wells Impacted with Volatile Organic Compounds (VOCs)
Water quality in City Wells 7 and 17 appears to be threatened by groundwater plume(s) containing trichloroethene (TCE) and other VOCs migrating from an industrial area in eastern Temescal Subbasin. The City is evaluating the need to install a granular activated carbon (GAC) system or other groundwater treatment system to mitigate contamination at these production wells.

Production here would also provide some containment of the continued migration, but additional data are necessary for a complete evaluation. More complete containment could be accomplished with new, properly-placed production wells in the area. This strategy is proposed as the El Sobrante Groundwater Treatment Project, described below.

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5. El Sobrante Groundwater Treatment Project (wells plus treatment) The El Sobrante project would target an area of impacted groundwater quality and, through proven treatment technologies, improve the quality for beneficial use. The project is currently scheduled for fiscal year of 2020-2021 at a projected cost of $20,000,000, reflecting the high cost of groundwater treatment. The proposed location is in the vicinity of Sixth Street and El Sobrante. The project will yield 5,000 AFY to the current potable water system. The specific components of the project are three new wells, a raw water pipeline, a GAC pre-treatment system to reduce TCE in the extracted groundwater, followed by a treatment process which will be selective resins or BAT to reduce nitrates in the groundwater pumped, a 6,500 sq. ft. building to house the process, a product pipeline, property acquisition, and brine disposal to the SARI pipeline.

6.1.2. Groundwater Treatment Process Improvements
Strategies for this category provide for increased treatment capacity to improve the quality of the water supply and the groundwater basin by reducing nitrates and salts in the ambient groundwater. Improving the quality of the water supply reduces the subsequent loading of these constituents in groundwater from wastewater return flows, thereby benefiting the groundwater basin.

6. Groundwater Treatment Program
The City currently operates the Temescal Desalter to reduce salts in the City’s water supply. Expansion of the groundwater treatment program is needed to maintain long term water quality and usable supply. The amount of treated groundwater can be increased without additional facility expansion at this time.

7. Groundwater Blending Program
The City has an on-going nitrate blending program that is closely coordinated with the RWQCB and requirements of the City’s salt management plan. Groundwater with elevated nitrate is blended with imported water or groundwater with lower nitrate levels. This allows groundwater extraction to occur in areas of high nitrate levels resulting from historical activities including agriculture.

6.1.3. Groundwater Monitoring Program
The goal of the monitoring program is to support the long-term sustainability and protection of the groundwater resource. The objectives of the monitoring program are to better understand groundwater conditions, monitor the impacts of groundwater use, identify changes to

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8. Improvement of Groundwater Quantity/Quality Monitoring Program The City desires to improve the current groundwater monitoring program to track water levels, groundwater quality, and groundwater storage throughout the subbasins and over time.

Improvements involve the addition of dedicated monitoring wells that are not used for groundwater extraction. These wells provide a better representation of basin water levels and are not as influenced by near-well pumping depressions. The program involves the development of specific monitoring protocols including monitoring locations, frequency, measurements, sampling procedures, data management, and quality assurance/quality control measures. Current monitoring program and protocols are summarized in Appendix B with recommendations for future improvements.

6.1.4. Enhanced Groundwater Recharge
In order to increase basin yield and replenish extracted water, an increase in groundwater recharge is needed in all of the subbasins in this GWMP. Strategies for enhancing groundwater recharge involve the use of surface recharge basins, recharge wells, and in-lieu pumping when imported water is available. Sources of recharge water include stormwater, imported water and recycled water. Strategies that are more closely related to recycled water are repeated and expanded in the next section on recycled water.

9. Coldwater Subbasin Enhanced Recharge Project
The City may wish to implement an enhanced recharge project to enhance the quantity and quality of groundwater in the Coldwater Subbasin. Currently the City manages recharge in Coldwater Wash along a reach south of Glen Ivy Road. This enhanced recharge is accomplished through a series of in-stream berms that retain streamflow, allowing for increased percolation.

Only high flows during wet years are not captured; these flows have been observed to contribute to local flooding of roads and may represent an opportunity for additional recharge water. The City may wish to work with Riverside County Flood Control District to investigate methods of capturing these additional flows.

In addition to Coldwater Wash, there may be additional drainages where natural recharge could be increased. It is our understanding that runoff from Mayhew Canyon to the south is being diverted and recharged by EVMWD, and additional opportunities for increasing recharge along that drainage may be limited. Some runoff along drainages in the northern subbasin (Anderson, Bixby, and Brown Canyons) may be available for enhanced recharge in the future, but additional analysis is required. These drainages are located in a relatively dense residential area and have

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10. Recharge Basins within the Oak Avenue Detention Basin The Oak Avenue Detention Basin is a large stormwater basin located at the mountain front near Oak Avenue and Chase Drive. The basin is operated for flood control by RCFCWCD.

According to a pilot study conducted by the City (PBSJ, 2004), a recharge basin constructed within the larger detention basin is capable of receiving and percolating about 2,500 AFY. If another similar recharge basin were constructed in the detention basin, recharge could be potentially increased to as much as 4,000 or 5,000 AFY. In addition to optimizing the recharge of stormwater, recycled water or imported water could be conveyed to the detention basin for recharge. The City has had discussions with RCFCWCD in the past about cooperating in a groundwater recharge project. This strategy would require stormwater monitoring and continued coordination with RCFCWCD to ensure compatibility in operation of the facility for both flood control and recharge. Facilities to convey recycled water are described in the recycled water strategies below.

11. Recharge Basins within the Main Street Detention Basin Another flood control basin, the Main Street Detention Basin, could also be configured for additional groundwater recharge. The detention basin is located near Main Street and Upper Drive and functions to reduce peak flows into the lined channels of the City’s stormwater management system. According to a pilot study conducted by the City (PBSJ, 2004), a recharge basin constructed within the larger detention basin is capable of receiving and percolating about 500 AFY. If two additional basins were constructed at the site, the quantity recharged could be tripled to about 1,500 AFY. Implementation of this strategy will require stormwater monitoring and may also involve potential cleanup work within the basin. Similar to the Oak Avenue basin, any evaluation for implementing a recharge strategy at the Main Street basin will require ongoing coordination with RCFCWCD.

12. Upgradient Injection Wells
Enhanced recharge through wells is an option for increasing yield to the groundwater basin. Although exact locations have not yet been determined, recharge would most likely be effective at the upgradient portion of the Channel Aquifer, near the Arlington Gap. Recharge wells would need to be located to minimize interference with inflow from the adjacent RiversideArlington Subbasin. Although the inflow has been observed to contain elevated nitrate concentrations, the area represents a major source of recharge water to the Channel Aquifer.

Potable water, recycled water, or blended water could be injected into these wells. Specific components at each site would include a well, well head, down-comer pipes, flow metering, supply piping, flow control and pressure reducing valve, and air relief system.

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6.1.5. Expanded Use of Recycled Water
The management strategies in this GWMP provide for the expanded treatment and use of recycled water. Given the potential restrictions on imported water and highly variable rainfall patterns in the valley, recycled water may be the most reliable source of water available for management strategies. Strategies within this category involve the expansion of recycled water use in the basin. Currently, recycled water is used for urban irrigation, but the demand is relatively small. These strategies would develop the infrastructure to expand recycled water use for irrigation, which would decrease reliance on the groundwater basin. The infrastructure would also allow the movement of recycled water to areas within the Temescal Subbasin for enhanced groundwater recharge, currently planned through injection wells.

In 2001, the City conducted a Recycled Water Master Plan (Boyle, 2001) to evaluate the potential to expand the direct use of recycled water for non-potable applications such as park irrigation. The study concluded that additional opportunities for recycled water use exist, primarily during the summer months. Current irrigation demand of recycled water is about 5,600 AFY. As this supply is expanded, additional recycled water could provide in-lieu pumping in the summer months and groundwater basin recharge in the winter months. The recycled water strategies that follow are built around this concept.

13. Recycled Water Injection Wells
Recycled water injection wells could be constructed in several areas of the City that meet regulatory requirements for residence time underground prior to extraction. The Title 22, California Code of Regulations (Division 4, Chapter 3, Section 60320.010, California Department of Public Health) states: “for a subsurface injection project, all the recycled water shall be retained underground for a minimum of twelve (12) months prior to extraction for use as a drinking water supply, and shall not be extracted within 2,000 feet of a recycled water injection well.” The required distance from extraction wells is currently under review and may be revised.

This strategy would also need to meet other regulatory requirements including water quality objectives as provided in the DPH draft regulations (California DPH, 2007).

Specific components at each site include a well, well head, down-comer pipes, flow metering, piping and valves that are connected to the adjacent recycled water piping, and a flow control and pressure reducing valve.

14. Recycled Water Zone 3 to Zone 2 Interconnect
A pipeline that connects Zone 3 to Zone 2 would allow conveyance of recycled water to different water storage facilities in the City. Currently, Zone 3 is fed by WWTP3 and is not connected to any potential recharge sites such as the Oak Avenue and Main Street detention basins. Therefore, during wet periods the effluent from WWTP3 is currently unavailable for enhanced recharge to the groundwater basin.

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15. Recycled Water Zone 4 to Zone 3 Interconnect
A pipeline that connects Zone 4 to Zone 3 would allow conveyance of recycled water to customers in Zone 4. This would provide more flexibility in using Zone 3 recycled water in Zone 4 rather than conveying Zone 1 or Zone 2 water to Zone 4.

16. WWTP2 Upgrade to Tertiary
The secondary effluent from Wastewater Treatment Plant 2 (WWTP2) is currently conveyed to the Lincoln and Cota percolation ponds. Upgrades could be constructed at WWTP2 that would provide tertiary treatment and disinfection of the secondary effluent and produce Title 22 recycled water. The recycled water from WWTP2 could be connected to the recycled water system distribution at Harrison Street—which is immediately north of WWTP2—or sent to the percolation ponds for recharge.

17. WWTP1A Upgrade to Tertiary
The secondary effluent from Wastewater Treatment Plant 1A (WWTP1A) is currently conveyed to the Lincoln and Cota percolation ponds. Upgrades could be constructed at WWTP1A that would route the flows through the WWTP1 tertiary filters and chlorine contact tank to produce Title 22 recycled water. The recycled water could then be stored in the on-site recycled water reservoir or sent to the percolation ponds for recharge.

18. Lee Lake Water District’s (LLWD) Recharge to Bedford Subbasin This recharge project includes discharging recycled water (tertiary treated and disinfected) produced by LLWD into surface recharge basins or injection wells (exact locations to be determined) in the Bedford Subbasin. This recycled water is currently being discharged to Temescal Wash and is not contributing to groundwater basin storage. Since the groundwater basin ultimately discharges to the wash, surface water flow on an average basis is not expected to be substantially decreased. The source of the recycled water is wastewater from local residential communities that are supplied with imported water of generally higher quality than ambient groundwater. The resulting recycled water typically has lower TDS values than the ambient groundwater. Therefore, the recharge of recycled water will likely have a beneficial water quality impact on the ambient TDS in the subbasin. In addition, both the City and LLWD may need to rely on local groundwater to increase water supply. Enhancing recharge is expected to increase the subbasin yield. A feasibility study of this project including impacts to water levels and water quality is included as Appendix D.

19. Use of Recycled Water as In-Lieu Pumping
The expanded use of recycled water as a substitute for groundwater under certain nonpotable applications (such as park irrigation) would have major benefits for groundwater management. This use of recycled water would decrease pumping from the groundwater basin.

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*URXQGZDWHU0DQDJHPHQW3ODQ 3DJH $.0&RQVXOWLQJ(QJLQHHUV Currently, the City provides approximately 5,600 AFY of recycled water for irrigation. In 2001, the City conducted a survey to examine the potential for expanded recycled water use (Boyle, 2001). In that analysis, the engineers concluded that approximately 1,300 acres of parks, golf courses, and other landscape areas could be irrigated with recycled water. The City has a current capacity of about 6,780 AFY, with a current demand of about 5,600 AFY. As system improvements are made and additional recycled water is available, using recycled water to replace groundwater pumping is a viable management strategy. In addition, the sale of recycled water to customers for additional non-potable applications could provide revenue for continued investment in groundwater management strategies.

6.1.6. Use of Imported Water
Imported water has been and continues to be an important source of supply for the City.

Water from the Colorado River and State Project Water is available from the Metropolitan Mills filtration plant and delivered to the City through three existing turnouts. These strategies involve the purchase of additional imported water when available for direct use to decrease groundwater basin pumping (in-lieu pumping). Alternatively, imported water may be used for enhanced recharge to the groundwater basin.

20. Purchase of Metropolitan Water District In-Lieu Water In-lieu purchase water is excess raw water provided to Metropolitan customers at reduced rates. Use of this water will reduce the amount of groundwater pumped from the basin. When Metropolitan offers in-lieu water, the City should purchase it while concurrently reducing groundwater pumping as practicable. The in-lieu purchase water could be: 1) stored in the City’s recycled water reservoir(s) for use; 2) stored in the City’s recycled water reservoirs(s) and conveyed to spreading basins or injection wells for storage in the groundwater basin; or 3) treated at the City’s water treatment plants and used as Title 22 drinking water.

21. Pipeline to Convey Metropolitan Water District (Metropolitan) In-Lieu Water to Border Avenue Recycled Water Reservoir
To convey the in-lieu purchase water to the City’s recycled water facilities, a pipeline would need to be constructed from the City’s WR-19 turnout (Metropolitan Lower Feeder connection) to the City’s Border Avenue recycled water reservoir. In this area, available imported water could also be conveyed to recharge basins at the Oak Avenue Detention Basin.

Recharge of imported water would require coordination with regulatory agencies such as the RWQCB and RCFCWCD.

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6.1.7. Wastewater Pond Maintenance
This strategy provides for improved percolation of permitted amounts of wastewater into the groundwater basin. It is anticipated that amounts may decrease over time as treatment and use of recycled water is expanded.

22. Lincoln and Cota Street Percolation Ponds Maintenance Program Regularly scheduled maintenance on the percolation ponds is critically important to optimize pond percolation and minimize losses to evaporation. This percolation provides groundwater recharge and contributes positively to the subbasin water balance. Even if most of this water ultimately leaves the subbasin as rising groundwater, it maintains head in the discharge area, decreasing gradients and the potential outflow of additional groundwater. Based on past monitoring of percolation rates in the ponds, they require maintenance approximately every 3 to 5 years. This consists of removing the fine soil particulates (filter cake) from the pond bottom and sides and hauling the filter cake offsite for approved disposal.

6.1.8. Coordination with Regulatory Agencies
The City maintains positive working relationships with local agencies, but currently has no centralized effort to coordinate with agencies on water quality issues for the protection and enhancement of the groundwater subbasins. The strategies offered below are a starting point for increased communication and action on specific groundwater issues.

23. Coordinate with Riverside County on Water Quality and Well Construction The County of Riverside Department of Environmental Health (RDEH) conducts programs and services that are beneficial to the local groundwater subbasins (RDEH, 2008).

Through the Water Engineering Program, the County handles well permitting for any well constructed in the County including, but not limited to, driven wells, monitoring wells, cathodic wells, extraction wells, agricultural wells, and community water supply wells. They are also responsible for the permitting, inspection, compliance, monitoring, and enforcement of state standards for small water systems in the County. These programs are consistent with and ensure well construction/destruction standards are implemented as developed by DWR. The City wishes to maintain a positive working relationship with the Water Engineering Program to track wells drilled within the subbasins and ensure proper well construction and destruction for the protection of the groundwater resource. Methods of coordination to access the well information at the County will be further explored through communication with Riverside DEH.

The Riverside DEH also conducts programs related to groundwater contamination. Their ongoing Local Oversight Program provides for oversight of the investigation and cleanup of soil and groundwater contamination from unauthorized releases from leaking underground storage tanks (LUSTs). This program is conducted under contract from the State Water Resources Control Board (SWRCB) and compiles regional information on assessment and cleanup efforts.

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24. Coordinate with the Regional Water Quality Control Board (RWQCB), Santa Ana Region on Water Quality Issues in the Basin
The City will work with the RWQCB to obtain information on groundwater contamination areas that may adversely impact water quality in the City’s drinking water wells.

This coordination will involve communication with the RWQCB on sites or areas of known or suspected groundwater impacts. This communication can also involve the periodic access of site cleanup lists on the RWQCB websites.

The City will also continue coordination with the RWQCB on monitoring industrial waste discharges to the sanitary sewer through the City’s ongoing Industrial Waste Pre-treatment and Source Control Program. As a requirement of this program, quarterly and annual reports are provided to the RWQCB.

6.1.9. Water Conservation and Demand Management
As previously discussed, the City has committed to aggressive steps on water conservation and demand management. A full-time Water Conservation Coordinator has developed and implemented numerous educational programs (including an education center), water wise events and awards, rebate programs, data-based field tests to demonstrate actual water savings, installation of landscape irrigation controllers, and coordinated programs with Metropolitan and WMWD. Although these measures will continue on their established schedules, the City wishes to acknowledge and incorporate these activities into an overall GWMP strategy.

25. Continue and Expand Water Conservation and Demand Management Activities
Numerous programs have been implemented by the City’s aggressive water conservation efforts. A rebate program for low-flow toilets and washing machines has been in place for several years. In addition to an extensive education program previously described (Section 4.2), the City is taking aggressive steps to reduce irrigation demand. The City has initiated a program of working directly with homeowners’ associations and others on the installation of weather-based irrigation controls (WBIC) on landscape irrigation systems. Two test programs are planned to determine specific water savings for such devices and include a condominium neighborhood in the older part of Corona and a single-family residential neighborhood in an area of newer development. These two tests will provide monitoring data and information on potential water savings and demand reduction for application to other areas.

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6.2. Evaluation of Management Strategies using AB3030 Checklist Water Code Section 10753 provides a list of 12 examples of groundwater basin issues that may be considered in an AB3030 GWMP. These examples serve as a checklist to ensure that major groundwater basin issues are addressed. The issues are listed below, followed by an explanation of the relationship between each issue and the management strategies proposed in this GWMP.

6.2.1. Control of Saline Water Intrusion
The subbasins of interest are located in upland basins away from the coast and are not subject to the typical threat of coastal seawater intrusion. This issue can also include the potential influx of highly mineralized or brackish water from either natural or anthropogenic (humaninfluenced) sources. However, no highly mineralized influx has been identified to date. Although water entering the Temescal Subbasin through the Arlington Gap has been observed to have elevated nitrate and other minerals, the inflow contains similar water quality to ambient groundwater in the subbasin and is not a significant threat to water quality. In fact, this area has served as the main source of aquifer recharge to the basin.

6.2.2. Identification and Management of Wellhead Protection and Recharge Areas
Wellhead protection and recharge areas have been evaluated in the past and have been further assessed in this GWMP. In 2002, the City conducted an assessment of the vulnerability of their drinking water wells under the California Drinking Water Source Assessment Program (DWSAP). This program, developed by the California Department of Public Health (DPH) (formerly Department of Health Services), delineates the area around drinking water sources, such as wells, through which contaminants might reach the water supply. This assessment identified surface recharge areas in the vicinity of City wells. In addition, the analysis in this GWMP identifies the main areas of subbasin recharge for the aquifers tapped by City wells.

These areas include the entire footprint of the unconfined Channel Aquifer, recharge areas along washes and alluvial fans, and areas of subsurface inflow such as Temescal Canyon and Arlington Gap.

Strategies to manage and protect the recharge zones involve coordination with regulatory agencies such as Riverside County DEH and the RWQCB. These agencies are responsible for evaluating impacts to water quality from industrial or commercial activities and leaking underground storage tanks (LUSTs). Strategies 23 and 24 provide for the coordinated management required for protection of water supply. Also, the City’s expanded monitoring program (Strategy 8) will allow for better tracking of groundwater conditions in recharge areas.