final report 2017 water supply reliability plan update · final report – clwa water supply...

Nancy Clemm and Kennedy/Jenks Consultants

2775 North Ventura Road, Suite 100 Oxnard, California 93036

805-973-5700 FAX: 805-973-1440

Final Report

2017 Water Supply

Reliability Plan Update

November 1, 2017

Prepared for

Castaic Lake Water Agency 27234 Bouquet Canyon Road

Santa Clarita, California 91350-2173

K/J Project No. 1744209*00

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Final Report – CLWA Water Supply Reliability Plan Update 2017 i

Table of Contents

List of Tables .............................................................................................................................. iii

List of Figures............................................................................................................................. iii

List of Appendices ...................................................................................................................... iv

Acronym List .............................................................................................................................. iv

Executive Summary ..................................................................................................................... i

Section 1: Introduction .............................................................................. 1-1

1.1 Background ....................................................................................... 1-1 1.1.1 CLWA Water Supply Reliability Plans .................................... 1-2 1.1.2 Summary of 2011 Plan and Recommendations for

Implementation ...................................................................... 1-2 1.2 Authorization ..................................................................................... 1-3

1.2.1 Scope of Services .................................................................. 1-3 1.2.2 Conduct of Study .................................................................... 1-4 1.2.3 Comparison with 2011 Plan.................................................... 1-4

Section 2: Water Supplies and Demands ................................................... 2-1

2.1 Existing and Planned Water Supplies ................................................ 2-1 2.1.1 Imported Water Supplies – SWP ............................................ 2-4

2.1.1.1 SWP Facilities ...................................................... 2-4 2.1.1.2 SWP Contract Water Supply Provisions ............... 2-4 2.1.1.3 Factors Affecting SWP Table A Supplies .............. 2-6 2.1.1.4 SWP Table A Supply Assessment ........................ 2-7

2.1.2 Other Imported Supplies ........................................................ 2-9 2.1.2.1 Buena Vista-Rosedale Rio Bravo ......................... 2-9 2.1.2.2 Nickel Water - Newhall Land ................................ 2-9 2.1.2.3 Yuba Accord Water .............................................. 2-9

2.1.3 Groundwater ........................................................................ 2-10 2.1.3.1 Santa Clara River Groundwater Basin – East

Subbasin ............................................................ 2-10 2.1.3.2 Adopted Groundwater Management Plan ........... 2-10 2.1.3.3 Groundwater Operating Plan .............................. 2-11 2.1.3.4 Alluvium ............................................................. 2-15 2.1.3.5 Saugus Formation .............................................. 2-15 2.1.3.6 Groundwater Supply Assessment ...................... 2-16

2.1.4 Recycled Water .................................................................... 2-18 2.1.4.1 Existing and Future Wastewater Treatment

Facilities ............................................................. 2-19

Table of Contents (cont’d)

Final Report – CLWA Water Supply Reliability Plan Update 2017 ii

2.1.4.2 Additional Considerations Relating to the Use of Recycled Water .............................................. 2-20

2.1.5 Groundwater Banking and Exchange Programs ................... 2-21 2.1.5.1 Semitropic Banking Program .............................. 2-22 2.1.5.2 Rosedale-Rio Bravo Banking Program ............... 2-22 2.1.5.3 Semitropic Banking Program – Newhall Land ..... 2-23 2.1.5.4 Other (Planned) Banking .................................... 2-23 2.1.5.5 RRWBWD and West Kern Water Exchanges ..... 2-23

2.2 Existing and Projected Water Demands .......................................... 2-24

Section 3: Water Supply Reliability Analysis ............................................. 3-1

3.1 Water Operations Model ................................................................... 3-1 3.1.1 General Methodology ............................................................. 3-1 3.1.2 Hydrologic Variability .............................................................. 3-2 3.1.3 Reliability Determination ......................................................... 3-4 3.1.4 Interpretation of Water Operations Model Results .................. 3-4

3.2 Scenarios Analyzed .......................................................................... 3-7 3.2.1 Scenario Descriptions ............................................................ 3-7 3.2.2 Scenario Assumptions ............................................................ 3-8

3.3 Analysis Results .............................................................................. 3-13 3.3.1 Initial Reliability Results ........................................................ 3-13 3.3.2 Additional Supply Needs ...................................................... 3-18

3.3.2.1 Amount and Timing of Needs ............................. 3-18 3.3.2.2 Additional Supplies Considered .......................... 3-19 3.3.2.3 Assessment of Initial Supply Use ....................... 3-20 3.3.2.4 Supplies Selected for Evaluation ........................ 3-25

3.3.3 Reliability with Additional Supplies ....................................... 3-26

Section 4: Physical Reliability Considerations .......................................... 4-1

4.1 Physical Reliability ............................................................................ 4-1 4.2 Physical Constraints .......................................................................... 4-1

4.2.1 Local Infrastructure Constraints .............................................. 4-1 4.2.1.1 Identified Vulnerabilities........................................ 4-1

4.2.2 SWP Conveyance Constraints ............................................... 4-2 4.3 Catastrophic Interruption – Potential Outage Scenarios .................... 4-3

4.3.1 SWP Emergency Outage Scenarios ....................................... 4-4 4.3.1.1 Scenario 1: Emergency Freshwater Pathway ....... 4-6 4.3.1.2 Scenario 2: Complete Disruption of the

California Aqueduct in the San Joaquin Valley ................................................................... 4-7

4.3.1.3 Scenario 3: Complete Disruption of the West Branch of the California Aqueduct ........................ 4-7

4.3.1.4 Assessment of Worst-Case Scenario ................... 4-8

Table of Contents (cont’d)

Final Report – CLWA Water Supply Reliability Plan Update 2017 iii

4.4 Recommendations for Extended Outage Emergency Storage ......... 4-12 4.5 Recommendations for Short-Term Emergency and Operational

Storage ........................................................................................... 4-13

Section 5: Reliability Recommendations ................................................... 5-1

5.1 Summary of Supply Reliability Analysis ............................................. 5-1 5.2 Summary of Physical Reliability Considerations ................................ 5-3 5.3 Recommendations ............................................................................ 5-4

References ................................................................................................................................... i

List of Tables

2-1 CLWA’s Current and Planned Water Supplies and Banking Programs

2-2 Groundwater Operating Plan for the Santa Clarita Valley

2-3 Average/Normal Year Existing and Planned Groundwater Usage

2-4 Average/Normal Year Existing and Planned Recycled Water Usage

2-5 Normal Year SBX7-7 Demands

3-1 Scenario Assumption Summary

4-1 Projected Supplies and Demands During Six Month Disruption of Imported Supply

4-2 Emergency and Operational Storage Study Results

5-1 Summary of Supply Reliability Results

List of Figures

2-1 SWP Table A Supply Reliability

2-2 Alluvial Aquifer Supply Reliability

2-3 Saugus Formation Supply Reliability

3-1 Interpretation of Model Results

3-2 Form of Model Results Presented

3-3 SWP Table A Supply Reliability

3-4 Summary of Initial Reliability

3-5 Base Scenario Reliability

3-6 Scenario A Reliability

3-7 Scenario B Reliability

3-8 Scenario C Initial Reliability

Table of Contents (cont'd)

Final Report – CLWA Water Supply Reliability Plan Update 2017 iv

3-9 Scenario C Initial Reliability: Detail of Supply Shortfall

3-10 Scenario C Initial Reliability: Average Annual Supply Surplus and Shortfall

3-11 Scenario C Initial Reliability: Total Banking and Exchange Program Storage

3-12 Scenario C Initial Reliability: SWP Flexible Storage

3-13 Scenario C Initial Reliability: Semitropic Bank Storage

3-14 Scenario C Initial Reliability: Rosedale-Rio Bravo Bank Storage

3-15 Scenario C Reliability with Additional Supplies

3-16 Scenario C Reliability with Additional Supplies: Detail of Supply Shortfall

3-17 Scenario C: Total Banking Program Storage Comparison

3-18 Summary of Reliability with Additional Supplies

4-1 Primary SWP Facilities

4-2 Emergency Storage Areas

List of Appendices

A CLWA Water Operations Model Description

B Climate Change Groundwater Assessment Memorandum

Acronym List

The following abbreviations and acronyms are used in this report.

AB Assembly Bill

AF acre-feet

AFY acre-feet per year

Agency Castaic Lake Water Agency

AVEK Antelope Valley-East Kern Water Agency

Basin Santa Clara River Valley Groundwater Basin, East Subbasin

BDCP Bay Delta Conservation Plan

BO Biological Opinion

BVWSD Buena Vista Water Storage District


Final Report – CLWA Water Supply Reliability Plan Update 2017 v

CASGEM California Statewide Groundwater Elevation Monitoring

CEQA California Environmental Quality Act

CLWA Castaic Lake Water Agency

CVP Central Valley Project

DCR Delivery Capability Report

DDW California Division of Drinking Water

Delta Sacramento-San Joaquin Delta

DPH Department of Public Health

DWR California Department of Water Resources

ECHO Existing Conveyance High Outflow

ECLO Existing Conveyance Low Outflow

EIR Environmental Impact Report

EIS Environmental Impact Statement

ELT Early Long Term

gpm gallons per minute

GSI GSI Water Solutions

GSP groundwater sustainability plan

GWMP Groundwater Management Plan

KCWA Kern County Water Agency

LACWWD 36 Los Angeles County Waterworks District No. 36

LADWP Los Angeles Department of Water and Power

LARWQCB Los Angeles Regional Water Quality Control Board

Metropolitan Metropolitan Water District of Southern California

MAF million acre-feet

MGD million gallons per day

MG million gallon

MOU Memorandum of Understanding

MWM Maddaus Water Management Inc.

NCWD Newhall County Water District

Purveyor Supplier of drinking water at the retail level (also retail purveyor)

PWD Palmdale Water District

RRBWSD Rosedale-Rio Bravo Water Storage District

RWMP Recycled Water Master Plan

RWQCB Regional Water Quality Control Board


Final Report – CLWA Water Supply Reliability Plan Update 2017 vi

SBX7-7 California Senate Bill 7 of Extended Session 7 (Water Conservation Act of 2009)

SCVSD Santa Clarita Valley Sanitation District

SCV Santa Clarita Valley

SCV-GSA Santa Clarita Valley Groundwater Sustainability Agency

SCWD Santa Clarita Water Division

SGMA Sustainable Groundwater Management Act

Semitropic Semitropic Water Storage District

SRWS Self-regenerating water softeners

SWP State Water Project

Suppliers CLWA and purveyors collectively

SWRCB State Water Resources Control Board

SWRU Stored Water Recovery Unit

TMDL Total Maximum Daily Load

UWCD United Water Conservation District

UWMP Urban Water Management Plan

Valley Santa Clarita Valley

VWC Valencia Water Company

WKWD West Kern Water District

WRP Water Reclamation Plant

WQOs Water Quality Objectives

WUESP Water Use Efficiency Strategic Plan

Final Report – CLWA Water Supply Reliability Plan Update 2017 Executive Summary - i

Executive Summary

The Castaic Lake Water Agency (CLWA) periodically updates its Water Supply Reliability Plan (Plan) to identify current and future storage capacity and emergency storage needs and options for managing its water supplies. This Plan evaluates four supply scenarios (supplies per the 2015 Urban Water Management Plan [UWMP], and supplies with varying assumptions regarding projected State Water Project [SWP] and local supply availability and reliability), with each supply scenario evaluated against one demand scenario (projected demands with conservation per the 2015 UWMP).

Overview of the Plan Methodology

This Plan uses an analytic spreadsheet model developed for CLWA by MBK Engineers to assess the reliability of CLWA’s water supplies. The model performs annual water operations for the CLWA service area over a specified study period, using demands as they are projected to increase over the study period and, to reflect the uncertainty in the hydrology over the study period, using supplies that would be available under multiple hydrologic sequences. For each hydrologic sequence, the model steps through each year of the study period, comparing annual supplies to demands and operating CLWA storage programs as needed, adding to storage in years when supplies exceed demand and withdrawing from storage when demand exceeds supplies. Results from the multiple hydrologic sequences are then compiled and summarized to provide a statistical assessment of the reliability of CLWA’s supplies and storage programs to meet its projected demands over the study period.

In addition to the hydrologic reliability of the Santa Clarita Valley’s overall water supply, this Plan also discusses the physical reliability of the water delivery system in place to delivery its groundwater, imported water, and recycled water supplies. Deliveries of these supplies are dependent on an extensive network of SWP facilities used to pump, store, and convey SWP and other imported supplies, and CLWA and purveyor facilities to treat, pump, and distribute supplies. Supply delivery can be interrupted or constrained in a number of ways, and the Plan includes an assessment of the ability to meet demands during an extended twelve-month outage.

Supply and Demand Scenarios Evaluated

For this Plan update, the study period analyzed is 2017 through 2050 (the year of development buildout in the CLWA service area assumed in the 2015 UWMP). The analysis starts with a Base Scenario and evaluates three additional scenarios, described generally as follows:

Base Scenario: Based on 2015 UWMP demand, supply, and storage program assumptions. This includes planned increases in recycled water, conversion of Alluvium groundwater use from agricultural to municipal use, and dry-year increases in Saugus groundwater pumping.

Scenario A: Similar to the Base Scenario, but includes SWP supplies anticipated to be available with proposed California WaterFix facilities.

Final Report – CLWA Water Supply Reliability Plan Update 2017 Executive Summary - ii

Scenario B: Moderate supply reductions relative to the Base Scenario, with a reduction in SWP supply reliability, and less increase in Saugus pumping capacity and recycled water use.

Scenario C: Larger supply reductions relative to the Base Scenario, with a larger reduction in SWP supply reliability, and additional limits on groundwater supplies and recycled water use.

These scenarios represent four different views of what the future supply situation might look like. Each supply scenario is evaluated in the Plan to determine the reliability of that scenario in meeting projected demands in CLWA’s service area. For any scenario in which reliability is less than a 95 percent reliability goal, additional supply programs are included as needed to achieve that reliability goal.

Recommendations

The analysis shows that for all four scenarios, there is a supply surplus that greatly exceeds any projected shortfall throughout the study period. This is true even for Scenario C, the most conservative scenario. Given this, storage of surplus amounts of existing and planned supplies through expanded use of existing storage programs or new storage programs, rather than acquiring additional base or dry-year supply, appears to be the more effective use of resources.

Further, the analysis shows that a range of additional supply actions may be required to achieve a 95 percent reliability goal, depending on how the future supply situation evolves. As in any planning analysis, a number of assumptions have been made regarding projected demands and the availability of various supplies. The future may very well evolve somewhat differently than assumed, but will hopefully lie somewhere within the bounds of the scenarios analyzed. However, conditions should continue to be monitored, and water supply reliability should be reassessed as changing conditions, such as updated SWP reliability analyses that incorporate differing climate change assumptions or different Delta regulatory constraints, warrant.

Based on the water supply reliability analysis and a 95 percent reliability goal, and on physical reliability considerations, the following recommendations are made:

Near Term (through 2035)

Supply Reliability

Supplies: No additional supply actions are needed, beyond the 2015 UWMP planned increases in local supplies.

Physical Reliability

Emergency storage for extended outage:

o Reserve use of SWP flexible storage for emergency storage (rather than for dry-year supply).

o Pursue a further of analysis of emergency storage to establish criteria for and better quantify near and long-term storage needs.

Final Report – CLWA Water Supply Reliability Plan Update 2017 Executive Summary - iii

Longer Term (2035 through 2050)

Supply reliability

If future evolves like Base Scenario or Scenario A (i.e., local supply increases as planned, and SWP supplies like existing or with California WaterFix): No additional supply actions are needed.

If future evolves like Scenario B (i.e., local supply increases less than planned, and moderate reduction in SWP supplies): May need additional dry-year supply by 2046 to replace Semitropic Banking Program (ends in 2045). (If reserving SWP flexible storage for emergency use, this additional dry-year supply becomes a need rather than a “may” need).

If future evolves like Scenario C (i.e., even smaller local supply increases, and larger reduction in SWP supplies): Need additional dry-year supply of 10,000 AFY by 2035, and another 10,000 AFY increment of dry-year supply by 2046. (If reserving SWP flexible storage for emergency use, the first increment of dry-year supply is needed by 2030.)

Type of additional dry-year supply: Look first to dry-year supply from expanded use of existing storage programs or from new storage programs (rather than acquiring additional base or dry-year supply).

Physical reliability

Location of new dry-year supply program(s): For any new storage programs pursued, look first to programs located within CLWA’s service area, or at least south of the Tehachapi Mountains.

Emergency storage for extended outage: Reserve use of SWP flexible storage for emergency storage (rather than for dry-year supply). Consider up-sizing any new local or near-local storage programs to include storage reserved for emergency storage.

Final Report – CLWA Water Supply Reliability Plan Update 2017 Page 1-1

Section 1: Introduction

This section presents a brief background of the water supply reliability issues of the Castaic Lake Water Agency (CLWA), as well as the need for an update to CLWA’s Water Supply Reliability Plan. The objectives, scope of services, and conduct of study are also summarized.

1.1 Background

CLWA, a water wholesaler, contracts with the State of California, through the Department of Water Resources (DWR), to acquire and distribute imported State Water Project (SWP) water to the four local retail water purveyors in the Santa Clarita Valley (Valley, SCV). The purveyors, CLWA Santa Clarita Water Division (SCWD), Los Angeles County Waterworks District No. 36 (LACWWD 36), Newhall County Water District (NCWD), and Valencia Water Company (VWC), deliver these supplies to primarily municipal and industrial (M&I) users within the Valley. Together, the purveyors provide water to approximately 73,000 service connections as documented in the 2015 Urban Water Management Plan (UWMP).

Adequate planning for, and the procurement of, a reliable water supply for both current and future users is a fundamental function of CLWA. CLWA obtains its water supply for wholesale purposes principally from the SWP and currently has a long-term SWP water supply contract (SWP Contract) with DWR for 95,200 acre-feet per year (AFY) of SWP Table A Amount1. However, the availability of SWP supply is variable. It fluctuates from year to year depending on hydrology, regulatory restrictions, and operational conditions and is subject to substantial curtailment during dry years.

Due to this variability, CLWA and the retail purveyors have developed additional water supplies, as well as storage in groundwater banks. The primary additional supply is a 11,000 AFY surface water supply CLWA imports from the Buena Vista Water Storage District (Buena Vista or BVWSD) and the Rosedale-Rio Bravo Water Storage District (Rosedale-Rio Bravo or RRBWSD) in Kern County. This supply, which is developed from Buena Vista’s high flow Kern River entitlements, was first delivered to CLWA in 2007 and is available as a firm annual supply delivered to CLWA through SWP facilities. In addition, CLWA is able to manage some of the variability in its SWP supplies under certain provisions of its SWP Contract, including the use of flexible storage at Castaic Lake, as well as through its participation in several groundwater banking/exchange programs in Kern County.

All imported water is delivered to Castaic Lake through SWP facilities. From Castaic Lake, which serves as the terminal reservoir of the SWP’s West Branch, the water is treated at either CLWA’s Earl Schmidt Filtration Plant or Rio Vista Water Treatment Plant and delivered to the retail water purveyors through transmission lines owned and operated by CLWA.

CLWA meets approximately half of the Valley’s urban demand with imported water. CLWA and the retail purveyors meet the balance of their demands primarily with local groundwater and a

1 Table A is a schedule of annual water amounts as set forth in long-term SWP delivery contracts. Table A defines

the annual volume of water that can be requested by an SWP contractor in a given year under regular contract provisions without consideration of surplus SWP water deliveries or other supplies available to an SWP contractor.


small amount of recycled water. In the 2015 UWMP, CLWA and the retail purveyors evaluated the long-term water needs (water demand) within their service areas based on applicable population projections and the build-out of the county and city land use plans and compared these needs against existing and potential water supplies. Results indicate that the total projected water supplies available to CLWA and the retail purveyors over the next 20-year projection period and beyond during normal, single-dry, and multiple-dry year periods are sufficient to meet the total projected water demands throughout the Valley provided that CLWA and the retail purveyors plan to utilize increased proportions of SWP Table A Amounts, and continue to incorporate conjunctive use, water conservation, water transfers, recycled water, and water banking as part of the total water supply portfolio and management approach to long-term water supply planning.

1.1.1 CLWA Water Supply Reliability Plans

In 2003, CLWA developed a Water Supply Reliability Plan (2003 Plan). The primary objectives of that plan were to identify and evaluate supply opportunities and recommend a water supply reliability strategy. The plan was based on then-current DWR estimates of SWP delivery reliability and water demands provided by the retail purveyors. Since the preparation of the 2003 Plan, DWR has prepared biennial updates of its SWP delivery reliability report, and CLWA and the purveyors have updated their local supply plans and demand projections and prepared three UWMP updates. Based on recommendations in previous reliability plan updates, CLWA has developed additional water supplies as well as capacity in groundwater banks and exchange programs. Together with its Table A Amounts and flexible storage allowed under the Monterey Amendment to the SWP Contract, these additional water management options have created a portfolio of water supplies and programs, which require periodic reassessment to maximize water supplies and minimize water supply costs.

To incorporate updated information and additional supplies and programs, CLWA has periodically authorized Kennedy/Jenks to update its Water Supply Reliability Plan. The most recent of these periodic reliability plan updates is the 2011 Water Supply Reliability Plan (2011 Plan), which identified current and future storage capacity and emergency storage needs and options.

1.1.2 Summary of 2011 Plan and Recommendations for

Implementation

The 2011 Plan recommended the following action plan. For the near term, CLWA was to maintain sufficient water reliability programs (banking and exchange programs) that would meet water demands assuming vulnerability to a Delta levee failure and compliance with California Senate Bill 7 of Special Extended Session 7 (SBX7-7) of 2009 (which called for a 20 percent reduction in per capita water use by 2020). CLWA was advised to reassess its water storage requirements after a determination was made through the Bay Delta Conservation Program (BDCP) (now referred to as the California WaterFix) whether or not to construct an isolated facility. CLWA was advised to utilize criteria for providing supplies based on a 95 percent confidence interval. The action plan included the following elements:

At 2020 demand levels, CLWA was to maintain a minimum pumpback capacity of 16,000 AFY. No additional six-year storage capacity was required.


At 2030 demand levels, CLWA was to maintain a minimum pumpback capacity of 22,000 AFY. No additional six-year storage capacity was required.

In developing water reliability programs, CLWA was advised to consider potential buildout demands for storage at a minimum of 89,000 acre-feet (AF) with a pumpback capacity of 45,000 AFY.

Additionally, actual water demand in CLWA’s service area was to be monitored to determine the validity of the SBX7-7 (20 percent per capita reduction) assumption.

The 2011 Plan also identified several issues that would affect both the schedule, as well as the process, of implementation. These issues included near-term banking storage capacity requirements. The available storage capacity of 167,420 AF was found sufficient to meet an estimated six-year storage requirement of 89,000 AF. Therefore, the 2011 Plan concluded that CLWA did not have to seek additional storage capacity under the circumstances at that time. The assumed pumpback capacity of 37,370 AFY was found to be lower than the estimated build-out requirement of 45,000 AFY, but was estimated to be sufficient until about the year 2040.

1.2 Authorization

Since preparation of the 2011 Plan, a number of things have changed. Updated information has become available, including more recent demand projections, SWP reliability estimates, and recycled water use estimates, all as documented in the 2015 UWMP. New storage programs have been implemented, including the Semitropic Water Storage District (Semitropic) Banking Program and several water exchanges. A new analytic tool was also developed to evaluate water supply operations and reliability for the service area.

In recognition of the need to re-evaluate and update the issues associated with potential water supply reliability projects and current reliability conditions, CLWA has authorized Kennedy/Jenks Consultants in cooperation with Nancy Clemm to update its Water Supply Reliability Plan (Plan).

1.2.1 Scope of Services

To accomplish the objectives of this Plan update, the following scope of services was developed:

1. Meet with CLWA staff to discuss objectives of the plan.

2. Based on recent demand projections developed by CLWA and purveyors in the 2015 UWMP, summarize CLWA’s water demand requirements over the planning period (i.e., 2050, which is build-out).

3. Summarize CLWA’s current and projected water supplies as provided for in the 2015 UWMP.

4. Identify the physical and hydrological reliability requirements of CLWA’s water supply.

5. Utilize the spreadsheet model prepared by MBK to provide a quantitative assessment of the water supply reliability and risk of four pre-determined water supply scenario portfolios.


6. Using the results of the model, identify and recommend the types of actions CLWA should take (for each scenario) in order to achieve the desired reliability (95%).

7. Assess the water banking requirements and/or other supplies needed to support the expected water supply variability and reliability of CLWA’s supplies.

8. Prepare a draft report and submit to CLWA for review. After incorporating CLWA staff comments, a final draft report will be prepared.

1.2.2 Conduct of Study

The information developed for this study is based on a review of existing sources of information, contact with CLWA staff, training on a new water supply operations model prepared by MBK Associates for CLWA, and office analysis. Initial phases of the study involved the research and documentation of information regarding existing and planned water supplies, demands, and water management opportunities. Subsequent phases of the study evaluated the supply reliability situation facing CLWA and utilized the water supply operations model to help identify future management actions and make recommendations for a plan of implementation.

1.2.3 Comparison with 2011 Plan

Differences between the 2011 Plan and this Plan include differing demand and supply assumptions used in the analyses, analysis of different scenarios, and use of a different analytic tool and methodology to conduct the analysis. Each is discussed further below.

The 2011 Plan relied on demand and supply information from the 2010 UWMP, while this Plan uses updated information from the 2015 UWMP. The more significant changes between the 2010 and 2015 UWMPs are the result of updated projections of service area demands and recycled water use, and storage program additions and revisions. The largest difference between the two UWMPs is in projected demands, with a reduction from 2010 UWMP demand projections of about 28,000 AFY by 2050. Among supplies, the largest difference is a reduction from 2010 UWMP projections of recycled water use of about 11,000 AFY by 2050. New storage programs and exchanges implemented since the 2010 UWMP are incorporated into the 2015 UWMP, including the long-term Semitropic Banking Program and several water exchanges. The 2015 UWMP also reflects a more realistic estimate of firm withdrawal capacity from the Rosedale-Rio Bravo Banking Program, based on experience during the recent drought, and the capacity expansions needed to achieve the 20,000 AFY withdrawal capacity assumed in the 2010 UWMP.

While the 2011 Plan and this Plan each evaluate four scenarios, the scenarios evaluated are different. The 2011 Plan evaluated two supply scenarios (supplies per the 2010 UWMP, and supplies with a Delta levee failure [i.e., an interruption in SWP supply]), with each supply scenario evaluated against two demand scenarios (demands with and without the conservation required under SBX7-7). This Plan evaluates four supply scenarios (supplies per the 2015 UWMP, and supplies with varying assumptions regarding projected SWP and local supply availability and reliability), with each supply scenario evaluated against one demand scenario (projected demands with active conservation programs per the 2015 UWMP).


The analysis methodology in the 2011 Plan included use of a Monte Carlo analysis. This entailed performing a regression analysis of SWP delivery data from a DWR computer model study of SWP operations, using that statistical relationship to generate 1,000 SWP delivery forecasts, and evaluating the ability to meet demands using those 1,000 forecasts. Since the 2011 Plan was prepared, a new analytic tool has become available. It is a spreadsheet model of CLWA water supply operations developed by MBK Associates for CLWA. This model uses multiple historical sequences of hydrology and SWP supplies directly from DWR computer model studies (without need for regression analysis or Monte Carlo simulations).


Section 2: Water Supplies and Demands

This Plan evaluates the reliability of existing and planned water supplies in meeting projected demands in CLWA’s service area during the study period from 2017 through 2050 (the year of development buildout in the service area assumed in the 2015 UWMP). The evaluation starts with a Base Scenario, which is based on the water supplies, storage programs, and demand projections presented in detail in the 2015 UWMP. The 2015 UWMP water supply and demand projections are summarized in this Section 2.

The Base Scenario and its supply and demand projections serve as the starting point or basis for three additional water supply scenarios evaluated in this Plan: Scenarios A through C. These three scenarios include varying assumptions regarding the availability of SWP, groundwater, and recycled water supplies, and are described in Section 3.

The focus in an UWMP is on supplies under normal conditions, in a single-dry year, and in a multiple-dry year period. In this Plan, supply reliability is assessed under a full range of hydrologic conditions. Some supplies available to meet CLWA service area demands vary depending on hydrologic conditions – in particular, SWP and groundwater supplies. For these two supply sources, the data presented below represents a full range of hydrology, rather than the normal and dry-year focus of an UWMP. While the data looks different from the 2015 UWMP, it is taken from the same reports and studies used as sources for the 2015 UWMP. For the remaining supply sources, the descriptions and supply data presented in this section are directly from the 2015 UWMP (with a few minor exceptions noted below).

2.1 Existing and Planned Water Supplies

CLWA’s existing water supplies include imported supplies, local groundwater, recycled water, and water from existing exchange and groundwater banking programs. Planned supplies include local restored, replaced, and new groundwater production, increased use of recycled water, and expanded existing and planned banking programs. Local and imported water resources in the Santa Clarita Valley are managed cooperatively between CLWA and the purveyors. These existing (2015) and planned supplies are provided in Table 2-1 and are described in more detail in the follow sections.


TABLE 2-1 CLWA’S CURRENT AND PLANNED WATER SUPPLIES AND BANKING PROGRAMS (AFY)(a)

2015 2020 2025 2030 2035 2040 2045 2050

Existing Supplies

Existing Groundwater(b)

Alluvial Aquifer 24,100 24,100 24,100 24,100 24,100 24,100 24,100 24,100

Saugus Formation 7,445 7,445 7,445 7,445 7,445 7,445 7,445 7,445

Total Groundwater 31,545 31,545 31,545 31,545 31,545 31,545 31,545 31,545

Recycled Water(c)

Total Recycled 450 450 450 450 450 450 450 450

Imported Water

State Water Project(d)

59,000 58,800 58,500 58,300 58,100 58,100 58,100 58,100

Flexible Storage Accounts(e)

6,060 6,060 6,060 4,680 4,680 4,680 4,680 4,680

Buena Vista-Rosedale 11,000 11,000 11,000 11,000 11,000 11,000 11,000 11,000

Nickel Water - Newhall Land(f)

1,607 1,607 1,607 1,607 1,607 1,607 1,607 1,607

Yuba Accord Water(g)

1,000 1,000 1,000 - - - - -

Total Imported 78,667 78,467 78,167 75,587 75,387 75,387 75,387 75,387

Existing Banking and Exchange Programs

Rosedale Rio-Bravo Bank(h)

3,000 3,000 3,000 3,000 3,000 3,000 3,000 3,000

Semitropic Bank(h)

5,000 5,000 5,000 5,000 5,000 5,000 5,000 -

Semitropic – Newhall Land Bank

(h)(i)

4,950 4,950 4,950 4,950 4,950 4,950 4,950 4,950

Rosedale Rio-Bravo Exchange(j)

9,500 9,500 - - - - - -

West Kern Exchange(j)

500 500 - - - - - -

Total Bank/Exchange 22,950 22,950 12,950 12,950 12,950 12,950 12,950 7,950

Total Existing Supplies 134,412 133,412 123,112 120,532 120,332 120,332 120,332 115,332

Planned Supplies

Future Groundwater(k)

Alluvial Aquifer(l)

- 2,000 4,000 5,000 7,000 7,000 7,000 7,000

Saugus Formation (Restored)(m)

- 3,230 3,230 3,230 3,230 3,230 3,230 3,230

Saugus Formation (New)(n)

- - - - - - - -

Total Groundwater - 5,230 7,230 8,230 10,230 10,230 10,230 10,230

Recycled Water(o)

Total Recycled - 565 5,156 7,627 9,604 9,604 9,604 9,604

Planned Banking Programs

Rosedale Rio-Bravo Bank(p)

- 7,000 7,000 17,000 17,000 17,000 17,000 17,000


Additional Bank(q)

- - - - - - - 5,000

Total Banking - 7,000 7,000 17,000 17,000 17,000 17,000 22,000

Total Planned Supplies - 12,795 19,386 32,857 36,834 36,834 36,834 41,834

Notes:

(a) The values shown under "Existing Supplies" and "Planned Supplies" are projected to be available in average/normal years to CLWA and the retail water purveyors. The values shown under "Existing Banking and Exchange Programs" and "Planned Banking Programs" are the maximum capacity of program withdrawals, and would typically be used only during dry years.

(b) Existing groundwater supplies represent the quantity of groundwater anticipated to be pumped with existing wells. As indicated in the 2009 Groundwater Basin Yield Analysis, individual purveyors may have well capacity in excess of quantities shown in this table.

(c) Existing recycled water is actual use in 2015. CLWA currently has 1,600 AFY under contract.

(d) SWP supplies are based on average deliveries from DWR’s 2015 Delivery Capability Report (DCR).

(e) Includes both CLWA and Ventura County entities flexible storage accounts. Extended term of agreement with Ventura County entities expires after 2025. (f) Existing Newhall Land supply committed under approved Newhall Ranch Specific Plan. Assumed to be transferred to CLWA or VWC during Newhall Ranch development,

and available for annual purchase prior to that.

(g) Supply shown is amount available in dry periods, after delivery losses. This supply would typically be used only during dry years and is available through 2025.

(h) Supplies shown are annual amounts that can be withdrawn using existing firm withdrawal capacity and would typically be used only during dry years. (i) Existing Newhall Land supply. Assumed to be transferred to CLWA or VWC during Newhall Ranch development, with firm withdrawal capacity made available to CLWA

prior to that.

(j) Supplies shown are totals recoverable under the exchange and would typically be recovered only during dry years. (k) Planned groundwater supplies represent new groundwater well capacity that may be required by an individual purveyor’s production objectives in the Alluvial Aquifer and

the Saugus Formation. When combined with existing purveyor and non-purveyor groundwater supplies, total groundwater production remains within the sustainable ranges identified in the 2009 Groundwater Basin Yield Analysis. Existing and planned groundwater pumping remain within the basin operating plan.

(l) Represents a shift in current agricultural pumping by Newhall Land and Farming to VWC due to the development of Newhall Ranch.

(m) VWC Well 201 is planned to be returned to service by 2017 with treatment under a permit from the DDW.

(n) Up to four new and replacement wells are planned to provide additional dry-year supply and would typically be used only during dry years. (o) Recycled water demand projection is based on implementation of complete build-out system described in the RWMP Update and reflects demands that can cost-

effectively be served. (p) Firm withdrawal capacity under existing Rosedale Rio-Bravo Banking Program to be expanded by 7,000 AFY by 2017 (for a combined total of 10,000 AFY) and an

additional 10,000 AFY by 2030.

(q) Additional banking program with firm withdrawal capacity of 5,000 AFY by 2050.


2.1.1 Imported Water Supplies – SWP

2.1.1.1 SWP Facilities

The SWP is the largest state-built, multi-purpose water project in the country. Construction of most initial SWP facilities was completed by 1973, and today includes 28 dams and reservoirs, 26 pumping and generating plants and approximately 660 miles of aqueducts. The primary water source for the SWP is the Feather River, a tributary of the Sacramento River. Storage released from Oroville Dam on the Feather River flows down natural river channels to the Sacramento-San Joaquin River Delta (Delta). While some SWP supplies are pumped from the northern Delta, the vast majority of SWP supplies are pumped from the southern Delta into the 444-mile-long California Aqueduct. Water pumped from the southern Delta may be temporarily stored in San Luis Reservoir for delivery later in the year, or conveyed further south in the California Aqueduct. The California Aqueduct conveys water along the west side of the San Joaquin Valley to Edmonston Pumping Plant, where water is pumped over the Tehachapi Mountains and the aqueduct then divides into the East and West Branches. CLWA takes delivery of its SWP water at Castaic Lake, a terminal reservoir of the West Branch. From Castaic Lake, CLWA delivers its SWP supplies to the local retail water purveyors through CLWA’s transmission pipeline system.

2.1.1.2 SWP Contract Water Supply Provisions

CLWA’s primary imported water supply is from the SWP. The SWP is operated by DWR, which provides SWP water supplies to CLWA and 28 other urban and agricultural public water supply agencies in California. In the early 1960s, DWR entered into substantially uniform long-term SWP water supply contracts (SWP Contracts) with each of these water agencies (referred to as “contractors”) that spelled out the terms for water service and payment.

SWP Water Supplies

Each SWP contractor’s SWP Contract contains a “Table A,” which lists the maximum amount of contract water supply, or “Table A water,” an agency may request each year throughout the life of the contract. Table A Amounts are used in determining each contractor’s proportionate share, or “allocation,” of the total SWP water supply DWR determines to be available each year. Currently, CLWA’s annual Table A Amount is 95,200 AF.

The primary supply of SWP water made available under the SWP Contracts is allocated Table A supply. While Table A identifies the maximum annual amount of Table A water a SWP contractor may request, the amount of SWP water actually available and allocated to SWP contractors each year is dependent on a number of factors and can vary significantly from year to year. The primary factors affecting SWP supply availability include hydrology, the amount of water in SWP storage at the beginning of the year, and regulatory and operational constraints, as is discussed further in Section 2.1.1.3.

In addition to Table A supplies, the SWP Contracts provide for additional types of water that may periodically be available, including “Article 21” water and Turnback Pool water2. The

2 Article 21 water is water that may be made available by DWR when excess flows are available in the Delta. It is

made available on an unscheduled and interruptible basis and is typically available only in average to wet years,


availability of Article 21 water and Turnback Pool water is uncertain, and as a result, supplies of these types of SWP water are not included in this Plan.

While not specifically provided for in the SWP Contracts, DWR has in critically dry years created Dry Year Water Purchase Programs, where water is purchased by DWR from willing sellers with available supplies and is then sold by DWR to interested contractors. The availability of these supplies is uncertain, and is therefore not included in this Plan.

Flexible Storage Account

As part of its SWP Contract with DWR, CLWA has access to a portion of the storage capacity of Castaic Lake. CLWA has used this storage for dry-year use, but it is not strictly limited as such. The Flexible Storage Account allows CLWA to utilize up to 4,684 AF of the storage in Castaic Lake. Any of this amount that CLWA borrows must be replaced by CLWA within five years of its withdrawal. CLWA manages this storage by keeping the account full in normal and wet years, delivering all or a portion of the stored amount during dry periods, and refilling it during the next year CLWA has surplus supplies. CLWA currently has an agreement with Ventura County SWP contractor agencies to obtain the use of their Flexible Storage Account, which allows CLWA access to another 1,376 AF of storage in Castaic Lake. CLWA access to this additional storage is available through 2025. While it is expected that CLWA and Ventura County will extend the existing flexible storage agreement beyond the 2025 term, for planning purposes here, it is not assumed to be available beyond 2025.

Water Management Provisions

The SWP Contract includes a number of provisions that give each contractor flexibility in managing the supplies that are available to it in a given year. For example, a contractor may take delivery of its allocated SWP supplies for direct use or storage within its service area, store that water outside its service area for later withdrawal and use within its service area, carry over a portion of that supply for storage on an as-available-basis in SWP reservoirs for delivery in following years (commonly referred to as “carryover”), or exchange a portion of that supply with others for return in a future year. The SWP Contract also provides for DWR to deliver non-SWP water supplies for contractors through SWP conveyance facilities.

CLWA takes advantage of each of these water management provisions. It participates in several groundwater banking programs in Kern County, has entered into several water exchanges, and has non-SWP supplies delivered to it through SWP conveyance facilities. These programs are described in more detail in Section 2.1.5. At current demand levels, CLWA also regularly stores a portion of any surplus SWP supply as carryover in San Luis Reservoir. Carryover is an easily and quickly accessible supply, and is a valuable resource if the next year is dry. However, carryover water may be lost when SWP reservoirs fill, which can occur in wetter years. Because of uncertainty in projecting the amount and frequency of San Luis Reservoir space available to store contractor carryover, carryover is not included in the supply projections in this Plan.

generally only for a limited time in the late winter. The Turnback Pool is a program through which contractors with allocated Table A supplies in excess of their needs in a given year may “turn back” that excess supply for purchase by other contractors who need additional supplies that year.


2.1.1.3 Factors Affecting SWP Table A Supplies

As noted above, while Table A identifies the maximum annual amount of Table A water a SWP contractor may request, the amount of SWP water actually available and allocated to SWP contractors each year is dependent on a number of factors and can vary significantly from year to year. The primary factors affecting SWP supply availability include: the availability of water at the source of supply in northern California, and the ability to transport that water from the source to the primary SWP diversion point in the southern Delta.

Availability of SWP Source Water

SWP supplies originate in northern California, primarily from the Feather River watershed. The availability of these supplies is dependent on the amount of precipitation in the watershed, water use by others in the watershed, and the amount of water in storage in Lake Oroville at the beginning of the year. Variability in the location, timing, amount and form (rain or snow) of precipitation, as well as how wet or dry the previous year was, produces variability from year to year in the amount of water that flows into Lake Oroville. Lake Oroville acts to regulate some of that variability, storing high inflows in wetter years that can be used to supplement supplies in dry years with lower inflows.

Climate change adds another layer of uncertainty in estimating the future availability of SWP source water. While different climate change models show differing effects, potential changes could include more precipitation falling in the form of rain rather than snow and earlier snowmelt, which would result in more runoff occurring in the winter rather than spread out over the winter and spring.

Ability to Convey SWP Source Water

Water released from Lake Oroville flows down natural river channels into the Delta, which is a network of channels and reclaimed islands at the confluence of the Sacramento and San Joaquin rivers. The SWP and the federal Central Valley Project (CVP) use Delta channels to convey water to the southern Delta for diversion, making the Delta a focal point for water distribution throughout the state.

A number of issues affecting the Delta can impact the ability to divert water supplies from the Delta, including water quality, fishery protection and levee system integrity. Water quality in the Delta can be adversely affected by both SWP and CVP diversions, which primarily affect salinity, as well as by urban discharge and agricultural runoff. The Delta also provides a unique estuarine habitat for many resident and migratory fish species, some of which are listed as threatened or endangered. Delta islands are protected from flooding by an extensive levee system. Levee failure and subsequent island flooding can lead to increased salinity requiring the temporary shutdown of SWP pumps.

SWP and CVP operations in the Delta are limited by a number of regulatory and operational constraints. These constraints are primarily incorporated into the State Water Resources Control Board (SWRCB) Water Rights Decision 1641 (D-1641), which establishes Delta water quality standards and outflow requirements that the SWP and CVP must comply with. In addition, SWP and CVP operations are further constrained by requirements included in


Biological Opinions (BOs) mandated by the federal Endangered Species Act for the protection of threatened and endangered fish species in the Delta. The requirements in the BOs are based on real-time physical and biological phenomena, which results in additional uncertainty in estimating SWP supplies.

2.1.1.4 SWP Table A Supply Assessment

DWR prepares a biennial report to assist SWP contractors and local planners in assessing the near and long-term availability of supplies from the SWP. DWR issued its most recent update, the 2015 DWR State Water Project Delivery Capability Report (2015 DCR), in July 2015. The 2015 DCR includes DWR’s estimates of SWP water supply availability under both current (2015) and future (2035) conditions.

Analysis Assumptions

DWR’s estimates of SWP deliveries are based on modeling studies using CalSim, a computer model that simulates monthly operations of the SWP and CVP systems. Key assumptions and inputs to the model include the facilities included in the system, hydrologic inflows to the system, and regulatory and operational constraints on system operations.

In the 2015 DCR, DWR uses the following assumptions to model current conditions: existing facilities; hydrologic inflows to the model based on 82 years of historical inflows (1922 through 2003), adjusted to reflect current levels of development in the supply source areas; current regulatory and operational constraints, including D-1641 and the BOs; and contractor demands for SWP water at maximum Table A Amounts.

To evaluate SWP supply availability under future conditions, the 2015 DCR included four model studies. The first of the future-conditions studies, the Early Long Term (ELT) scenario, used all of the same model assumptions for current conditions, but reflected changes to hydrology expected to occur from climate change, specifically, a 2025 emission level and a 15 cm sea level rise. The other three future-conditions studies also include varying model assumptions related to the BDCP/California WaterFix, such as changes to facilities and/or regulatory and operational constraints.

The 2015 UWMP used modeling results from both the current conditions study and, to estimate future SWP supply availability, the ELT scenario study. As discussed in more detail in Section 3, the analytic model used to evaluate CLWA supply reliability in this Plan is designed to use results from only one SWP model run, with those results used over the entire study period. In this Plan, results from the ELT scenario study are used to evaluate this Plan’s Base Scenario. The ELT scenario study is based on existing SWP facilities and regulatory constraints, with hydrology adjusted for the effects of climate change estimated to occur by 2025.

Analysis Results

In the 2015 DCR, DWR estimates that for all contractors combined, the SWP can deliver on a long-term average basis a total Table A supply of 61 percent of total maximum Table A Amounts under ELT scenario conditions. In the worst-case single critically dry year, DWR estimates the SWP can deliver a total Table A supply of 8 percent of total maximum Table A


Amounts under ELT scenario conditions. In multiple-dry year periods under the ELT scenario, DWR estimates the SWP can deliver a total Table A supply averaging 33 percent of total maximum Table A Amounts during a four-year dry period, and averaging 20 percent during a three-year dry period.

In this Plan, reliability analyses are conducted using the entire 82-year hydrologic period used in DWR’s model studies. DWR model study results for the ELT scenario are included in Figure 2-1, which shows SWP Table A supply allocations projected to be available to SWP contractors. The graph can be interpreted as the probability of SWP Table A allocations exceeding a given percentage. For example, for this scenario there is about a 40 percent probability that SWP allocations would be 70 percent or higher. CLWA’s Table A Amount of 95,200 AFY is multiplied by these allocation percentages to determine the amount of Table A supplies projected to be available to CLWA.

FIGURE 2-1 SWP TABLE A SUPPLY RELIABILITY


2.1.2 Other Imported Supplies

In addition to its SWP supplies, CLWA has an imported surface supply from BVWSD and RRBWSD in Kern County. CLWA has also entered into the Yuba Accord Agreement, under which it may access a north-of-Delta surface supply in dry years. CLWA provides these imported supplies to each of the retail purveyors on a wholesale basis. Additionally, Newhall Land has acquired a water transfer supply from a source in Kern County. This supply, referred to as Nickel Water, is assumed to be available to VWC through CLWA. These supplies are part of the imported supplies available to the service area.

2.1.2.1 Buena Vista-Rosedale Rio Bravo

CLWA has executed a long-term transfer agreement for 11,000 AFY with BVWSD and RRBWSD. These two districts, both located in Kern County, developed a program that provides both a firm water supply and a water banking component. Both districts are member agencies of the Kern County Water Agency (KCWA), a SWP contractor, and both districts have contracts with KCWA for SWP Table A Amounts. The supply is based on existing long-standing Kern River water rights held by BVWSD, and is delivered by exchange of the two districts’ SWP Table A supplies or directly to the California Aqueduct via the Cross Valley Canal. This water supply is firm; that is, the total amount of 11,000 AFY is available in all water year types based on the Kern River water right. CLWA began taking delivery of this supply in 2007.

2.1.2.2 Nickel Water - Newhall Land

Newhall Land acquired a water transfer in 2002 from Kern County sources known as Nickel water. This supply totals 1,607 AFY, and comes from a firm source of supply. This supply was acquired in anticipation of the development of Newhall Ranch, and is a supply that is contractually committed by Newhall Land under the Newhall Ranch Specific Plan approved by the Los Angeles County Board of Supervisors. Under its acquisition agreement, Newhall Land may assign its rights to this supply to VWC or CLWA, and in the meantime, may sell on an annual basis any or all of this supply. In the 2015 UWMP it was assumed for planning purposes that Newhall Ranch would be developed, that this water supply would be transferred to VWC or CLWA at the time of development, that it would then be available as an annual supply to the VWC, and that prior to any transfer CLWA could purchase this supply from Newhall Land in a year in which additional supply was needed. In this Plan, Nickel water is assumed to be transferred to VWC or CLWA and available each year beginning in year 2022.

2.1.2.3 Yuba Accord Water

In 2008, CLWA entered into the Yuba Accord Agreement, which allows for the purchase of water from the Yuba County Water Agency through DWR to 21 SWP contractors (including CLWA) and the San Luis and Delta-Mendota Water Authority. Yuba Accord water comes from north of the Delta, and the water purchased under this agreement is subject to losses associated with transporting it through the Delta. These losses can vary from year to year, depending on Delta conditions at the time the water is transported. Under the agreement, an estimated average of up to 1,000 AFY of non-SWP supply (after losses) is available to CLWA in dry years, through 2025. Under certain hydrologic conditions, additional water may be available to CLWA from this program. This supply is planned for use only in dry years, and is assumed to be available only through 2025.


2.1.3 Groundwater

This section presents information about the purveyors’ groundwater supplies, including a summary of the adopted groundwater management plan (GWMP). The passage of the Sustainable Groundwater Management Act (SGMA) in 2014 in effect requires replacement of the GWMP with a Groundwater Sustainability Plan (GSP) to be prepared by 2022.

2.1.3.1 Santa Clara River Groundwater Basin – East Subbasin

The sole source of local groundwater for urban water supply in the Valley is the groundwater Basin identified in the DWR Bulletin 118, 2003 Update as the Santa Clara River Valley Groundwater Basin, East Subbasin (Basin) (Basin No. 4-4.07). The Basin is comprised of two aquifer systems, the Alluvium and the Saugus Formation. The Alluvium generally underlies the Santa Clara River and its several tributaries, to maximum depths of about 200 feet; and the Saugus Formation underlies practically the entire Upper Santa Clara River area, to depths of at least 2,000 feet. There are also some scattered outcrops of Terrace deposits in the Basin that likely contain limited amounts of groundwater. However, since these deposits are located in limited areas situated at elevations above the regional water table and are also of limited thickness, they are of no practical significance as aquifers for municipal water supply; consequently, they have not been developed for any significant water supply in the Basin and are not included as part of the existing or planned groundwater supplies described in the 2015 UWMP. The Basin is defined in Bulletin 118 as being bordered on the north by the Piru Mountains, on the west by impervious rocks of the Modelo and Saugus Formations and a constriction in the alluvium, on the south by the Santa Susana Mountains, and on the south and east by the Gabriel Mountains (DWR, 2003). The extent of the basin generally coincides with the outer extent of the Alluvium and Saugus Formation.

2.1.3.2 Adopted Groundwater Management Plan

As part of legislation authorizing CLWA to provide retail water service to individual municipal customers, Assembly Bill (AB) 134 (2001) included a requirement that CLWA prepare a GWMP. This legislation has since been superseded by the passage of SGMA in 2014, however, the existing GWMP will be in effect until a GSP or alternative plan is submitted to DWR by 2022. The implementation and compliance with the SGMA is currently being discussed among CLWA, the retail purveyors and other entities in the basin. The recently formed Santa Clarita Valley Groundwater Sustainability Agency (SCV-GSA) will be responsible for preparation of the GSP. A detailed GWMP plan was adopted in 2003 to satisfy the requirements of AB 134. The plan both complements and formalizes a number of existing water supply and water resource planning and management activities in CLWA’s service area, which effectively encompasses the East Subbasin of the Santa Clara River Valley Groundwater Basin. Notably, the GWMP also includes a basin-wide monitoring program, the results of which provide input to annual reporting on water supplies and water resources in the Basin, as well as input to assessment of Basin yield for water supply. Groundwater level data from the existing groundwater monitoring program is reported to DWR as part of SBX7-6 implementation (California Statewide Groundwater Elevation Monitoring [CASGEM]) submitted twice a year.

The GWMP contains four management objectives, or goals, for the Basin including: (1) development of an integrated surface water, groundwater and recycled water supply to meet existing and projected demands for municipal, agricultural and other water uses; (2) assessment


of groundwater basin conditions to determine a range of operational yield values that use local groundwater conjunctively with supplemental SWP supplies and recycled water to avoid groundwater overdraft; (3) preservation of groundwater quality, including active characterization and resolution of any groundwater contamination problems; and (4) preservation of interrelated surface water resources, which includes managing groundwater to not adversely impact surface and groundwater discharges or quality to downstream basin(s).

Prior to preparation and adoption of the GWMP, a local Memorandum of Understanding (MOU) process among CLWA, the retail water purveyors and United Water Conservation District (UWCD) in neighboring Ventura County, downstream of the East Subbasin of the Santa Clara River Valley, had produced the beginning of local groundwater management, now embodied in the GWMP. As a result of the MOU, the cooperating agencies integrated their respective database management efforts and continued to monitor and report on the status of Basin conditions. Following adoption of the GWMP, the water suppliers developed and utilized a numerical groundwater flow model for analysis of groundwater basin yield and for analysis of extraction and containment of groundwater contamination. The results of those basin yield and contamination analyses, updated in 2009 by Luhdorff and Scalmanini Consulting Engineers and GSI Water Solutions, Inc. (LSCE & GSI, 2009), are the bases for the amounts and allocations of groundwater supplies in the 2015 UWMP. Subsequent analysis performed by GSI relating to perchlorate containment has not changed conclusions reached in the 2009 analyses.

The adopted GWMP includes 14 elements intended to accomplish the Basin management objectives listed above. Notable in the implementation of the GWMP has been the annual preparation of a Santa Clarita Valley Water Report that summarizes: (1) water requirements, (2) all three sources of water supply (groundwater, imported surface water and recycled water, all as part of the GWMP’s overall management objectives) and (3) projected water supply availability to meet the following year’s projected water requirements.

2.1.3.3 Groundwater Operating Plan

The groundwater component of overall water supply in the Valley derives from a groundwater operating plan developed and analyzed to meet water requirements (municipal, agricultural, small domestic) while maintaining the Basin in a sustainable condition, specifically no long-term depletion of groundwater or interrelated surface water. The operating plan also addresses groundwater contamination issues in the Basin, all consistent with the GWMP described above. The groundwater operating plan is based on the concept that pumping can vary from year to year to allow increased groundwater use in dry periods and increased recharge during wet periods to collectively assure that the groundwater Basin is adequately replenished through various wet/dry cycles. As ultimately formalized in the GWMP, the operating yield concept has been quantified as ranges of annual pumping volumes to capture year-to-year pumping fluctuations in response to both hydrologic conditions and customer demand.

Ongoing work through implementation of the GWMP has produced three detailed technical reports in addition to the annual Water Reports (the most recent of which, for 2016, was the nineteenth annual report). The first detailed technical report (CH2M Hill, April 2004) documents the construction and calibration of the groundwater flow model for the Valley. The second report (CH2M Hill and LSCE, August 2005) presents the initial modeling analysis of the purveyors’ original groundwater operating plan. The most recent report, an updated analysis of the basin (LSCE & GSI, 2009) presents the modeling analysis of the current groundwater


operating plan, including restoration of two Saugus Formation wells for municipal supply after treatment and also presents a range of potential impacts deriving from climate change considerations. The primary conclusion of the technical analysis is that the groundwater operating plan will not cause detrimental short or long-term effects to the groundwater and surface water resources in the Valley and is therefore sustainable. The analysis of sustainability for groundwater and interrelated surface water is described in detail in “Analysis of Groundwater Supplies and Groundwater Basin Yield, Upper Santa Clara River Groundwater Basin, East Subbasin” (Basin Yield Analysis) prepared August 2009 (LSCE & GSI, 2009).

The updated groundwater operating plan, summarized in Table 2-2, is as follows:

Alluvium: Pumping from the Alluvial Aquifer in a given year is governed by local hydrologic conditions in the eastern Santa Clara River watershed. Pumping for municipal, agricultural, and private purposes ranges between 30,000 and 40,000 AFY during normal and above-normal rainfall years. However, due to hydrogeologic constraints in the eastern part of the Basin, pumping is reduced to between 30,000 and 35,000 AFY during locally dry years.

Saugus Formation: Pumping from the Saugus Formation in a given year is tied directly to the availability of other water supplies, particularly from the SWP. During average-year conditions within the SWP system, Saugus pumping ranges between 7,500 and 15,000 AFY. Planned dry-year pumping from the Saugus Formation ranges between 15,000 and 25,000 AFY during a drought year and can increase to between 21,000 and 25,000 AFY if SWP deliveries are reduced for two consecutive years and between 21,000 and 35,000 AFY if SWP deliveries are reduced for three consecutive years. Such high pumping would be followed by periods of reduced (average-year) pumping, at rates between 7,500 and 15,000 AFY, to further enhance the effectiveness of natural recharge processes that would recover water levels and groundwater storage volumes after the higher pumping during dry years.

TABLE 2-2 GROUNDWATER OPERATING PLAN FOR THE SANTA CLARITA VALLEY

Aquifer

Groundwater Production (AF)

Normal Years Dry Year 1 Dry Year 2 Dry Year 3

Alluvium 30,000 to 40,000 30,000 to 35,000 30,000 to 35,000 30,000 to 35,000

Saugus Formation 7,500 to 15,000 15,000 to 25,000 21,000 to 25,000 21,000 to 35,000

Total 37,500 to 55,000 45,000 to 60,000 51,000 to 60,000 51,000 to 70,000

Within the groundwater operating plan, three factors affect the availability of groundwater supplies: sufficient source capacity (wells and pumps), sustainability of the groundwater resource to meet pumping demand on a renewable basis and protection of groundwater sources (wells) from known contamination, or provisions for treatment in the event of contamination. The first two factors are briefly discussed below, and more completely addressed in the 2016 Annual Water Report and the aforenoted Basin Yield Analysis (LSCE & GSI, 2009).


The groundwater operating plan recognizes ongoing pumping for the two major uses of groundwater in the Basin: municipal and agricultural (including private pumpers) water supply. This is shown in Table 2-3, which shows planned future groundwater pumping in normal years, by the purveyors as well as by other groundwater users. Consistent with the groundwater operating plan, projected groundwater pumping includes an ongoing conversion of pumping, coincident with planned land-use changes, from agricultural to municipal water supply. Projected pumping by agricultural and other users is projected to decrease as purveyor pumping increases by a similar amount, resulting in total pumping remaining essentially constant through 2050. The reduction in pumping for agricultural supply is primarily due to the development of Newhall Ranch (expected buildout date of 2034) and is expected to shift to an increase in pumping by VWC. The groundwater operating plan and projected pumping also includes other small private domestic and related pumping. Total projected groundwater pumping by all users within each aquifer is within the ranges for normal year pumping identified in the groundwater operating plan (Table 2-2). CLWA and the retail water purveyors recognize that these estimates of projected groundwater use are subject to adjustment based on various factors and conditions occurring from time to time. These estimates do not constitute an allocation of groundwater from the local groundwater basins.


TABLE 2-3 AVERAGE/NORMAL YEAR EXISTING AND PLANNED GROUNDWATER USAGE (AF)(a)

Alluvium Supplies 2020 2025 2030 2035 2040 2045 2050

Purveyors Existing 24,100 24,100 24,100 24,100 24,100 24,100 24,100

Purveyors Planned(b)

2,000 4,000 5,000 7,000 7,000 7,000 7,000

Purveyors Total 26,100 28,100 29,100 31,100 31,100 31,100 31,100

Non purveyors 12,500 10,500 9,500 7,500 7,500 7,500 7,500

Total Alluvium Production 38,600 38,600 38,600 38,600 38,600 38,600 38,600

Alluvium Yield 38,600 38,600 38,600 38,600 38,600 38,600 38,600

Saugus Formation Supplies 2020 2025 2030 2035 2040 2045 2050

Purveyors Existing 7,445 7,445 7,445 7,445 7,445 7,445 7,445

Purveyors Restored(c)

3,230 3,230 3,230 3,230 3,230 3,230 3,230

Purveyors Replacement and Planned(d)

0 0 0 0 0 0 0

Purveyors Total 10,675 10,675 10,675 10,675 10,675 10,675 10,675

Non purveyors(e)

1,800 1,800 1,800 1,800 1,800 1,800 1,800

Total Saugus 12,475 12,475 12,475 12,475 12,475 12,475 12,475

Saugus Yield 12,475 12,475 12,475 12,475 12,475 12,475 12,475

Notes: (a) The mix of Purveyor pumping between existing and planned wells may vary depending on year-specific operating conditions and Purveyor demands. However,

overall pumping remains within the groundwater basin yields. (b) These values account for the Newhall Ranch buildout schedule to 2034 and the shift in about 7,000 AFY of agricultural pumping from NLF to VWC between 2015

and 2035. Non-purveyor values are reduced by the same amount.

(c) VWC Well 201 values are assumed constant and are based on 2014 LSCE and GSI VWC Well 201 perchlorate work and 2008 Operating Plan.

(d) Up to four new and replacement wells are planned to provide additional dry-year supply and would not typically be operated during average/normal years.

(e) This includes private pumping from the 2008 Operating Plan, as well as projected Whittaker-Bermite pumping for perchlorate treatment, and is assumed constant.


2.1.3.4 Alluvium

Based on a combination of historical operating experience and groundwater modeling analyses (2005 and 2009), the Alluvial Aquifer can provide a total supply of groundwater on a long-term sustainable basis in the overall range of 30,000 to 40,000 AFY, with a probable reduction in dry years to a range of 30,000 to 35,000 AFY. Both of those ranges include almost 15,000 AFY of Alluvial pumping for current agricultural and other non-municipal water uses. The dry year reduction is a result of practical constraints in the eastern part of the Basin, where lowered groundwater levels in dry periods have the effect of reducing pumping capacities in that shallower portion of the aquifer. Over time, directly related to the rate of suburban development and corresponding decrease in agricultural land use the amount of Alluvial pumping for agricultural water supply is expected to decrease, with an equivalent increase in the amount of Alluvial pumping for municipal water supply. On an overall basis, Alluvial pumping is intended to remain within the sustainable ranges in the groundwater operating plan.

Adequacy of Supply

For municipal water supply, with existing wells and pumps, the three retail water purveyors with Alluvial wells (NCWD, SCWD and VWC) have a combined pumping capacity from active wells of nearly 42,000 gallons per minute (gpm), which translates into a current full-time Alluvial source capacity of approximately 67,000 AFY.

In terms of adequacy and availability, the combined active Alluvial groundwater source capacity of municipal wells of approximately 67,000 AFY is more than sufficient to meet the current and potential future municipal component of groundwater supply from the Alluvium, which in the near term is about 26,000 AFY (as shown in Table 2-3 for 2020). The higher individual and cumulative pumping capacities are primarily for operational reasons (i.e., to meet daily and other fluctuations from average day to maximum day and peak hour system demands). As noted above, the balance of the total planned Alluvial pumping of 38,600 AFY, which is within the 30,000 to 40,000 AFY in the operating plan, is for agricultural and other non-municipal, including small private, pumping.

2.1.3.5 Saugus Formation

Based on historical operating experience and recent (2005 and 2009) groundwater modeling analysis, the Saugus Formation can supply water on a long-term sustainable basis in a normal range of 7,500 to 15,000 AFY. Intermittent increases to 25,000 to 35,000 AF in dry years has not been historically experienced operationally, however, investigations of the Saugus Formation, historical groundwater level monitoring data, and numerical modeling indicate that the Saugus Formation can be pumped sustainably at these higher rates, followed by reductions in pumping in wet to normal years. The dry-year increases, based on modeled projections, demonstrate that the 25,000 to 35,000 AFY is a small amount of the large groundwater storage in the Saugus Formation and these amounts can be pumped over a relatively short (dry) period. This would be followed by recharge (replenishment) of that storage during a subsequent normal-to-wet period when the Saugus pumping would be reduced to 7,500 to 15,000 AFY.

Adequacy of Supply

For municipal water supply with existing wells, the three retail water purveyors (NCWD, SCWD and VWC) have a combined pumping capacity from active Saugus wells of nearly 17,000 gpm, which translates into a full-time Saugus source capacity of about 27,000 AFY. Additionally,


LACWWD 36 completed a Saugus Well with a pumping capacity estimated at 2,000 gpm and an annual capacity of 3,220 AFY. The active wells include two Saugus wells contaminated by perchlorate (Saugus 1 and 2), which were returned to service in 2010 with treatment facilities for use of the treated water for municipal supply under permit from the California Department of Public Health (DPH), now California Division of Drinking Water (DDW). The active wells also include the most recent replacement well, VWC’s Well 207, in a non-impacted part of the basin. Also included is VWC Well 201, which was impacted by the detection of perchlorate and removed from service in 2010. The well is expected to be restored to service by early 2018 with treatment facilities for use of the treated water for municipal supply under a permit from DDW (previously DPH), similar to the Saugus 1 and Saugus 2 wells. VWC Well 201 provides a total of 2,400 gpm of pumping capacity (for a dry-year production capacity of 3,775 AFY). Following the shutdown of VWC Well 201, VWC reduced pumping from a nearby well (VWC Well 205) to minimize influences on perchlorate migration. VWC Well 205 was voluntarily removed from service in 2012 when perchlorate was detected at concentrations below the detection level for reporting. VWC Well 205 will be returned to service with VWC Well 201. Because VWC Well 205 was voluntarily removed from service, it is considered an active existing well.

In terms of adequacy and availability, the combined active (existing) Saugus groundwater source capacity of municipal wells of about 30,700 AFY is more than sufficient to meet the planned use of Saugus groundwater in normal years of 7,500 to 15,000 AFY. This existing active capacity is also more than sufficient to meet near term dry year water demands, in combination with other sources. In order to supplement long term dry-year supplies, additional Saugus Formation wells are planned to be operational within the next three years.

With the restored capacity of the VWC Well 201 and the additional planned replacement and new Saugus wells, the total dry year combined capacity will increase from about 30,700 AFY to about 48,570 AFY. This combined capacity is more than sufficient to meet a dry year municipal production target of about 33,200 AFY.

2.1.3.6 Groundwater Supply Assessment

As noted above, total groundwater pumping from the Alluvial Aquifer and Saugus Formation that is projected to occur in normal years during the study period is summarized in Table 2-3. This table shows projected pumping by the purveyors from their existing and planned wells, as well as pumping by all other pumpers in these basins.

In addition to these normal-year pumping projections, this Plan also considers groundwater supply variations related to hydrology. As part of the Basin Yield Analysis (LSCE & GSI, 2009), a groundwater model was used to analyze the groundwater operating plan over an extended hydrologic period. While local hydrology affects the availability of Alluvial Aquifer groundwater, the year-to-year variability in Saugus Formation pumping is affected by the availability of SWP supplies, which is dependent on hydrology in northern California. Because SWP supplies affect the need to pump Saugus supplies, the basin yield analysis used a DWR SWP model study of SWP supply availability to assess Saugus pumping needs. As noted previously in Section 2.1.1.4, DWR SWP model studies use 82 years of historical inflows based on hydrology from 1922 through 2003. The Basin Yield Analysis used this same 82-year period, evaluating Alluvial pumping based on local hydrology during that period, and Saugus pumping based on hydrology in northern California.


The total pumping amounts simulated in the Basin Yield Analysis that are used in this Plan are shown in Figures 2-2 and 2-3, shown as “Total Basin” pumping. The portion of the total pumping that is projected to be pumped by the Purveyors – both existing and planned – is also shown, as well as pumping by other users.

FIGURE 2-2 ALLUVIAL AQUIFER SUPPLY RELIABILITY(1)


FIGURE 2-3 SAUGUS FORMATION SUPPLY RELIABILITY(1)

2.1.4 Recycled Water

CLWA and the purveyors recognize that recycled water is an important and reliable source of additional water that should be pursued as an integral part of the Valley’s water supply portfolio. Recycled water enhances reliability in that it provides an additional source of supply and allows for more efficient utilization of groundwater and imported water supplies. Draft Recycled Water Master Plans (RWMP) for the CLWA service area were completed in 1993 and 2002. These master plans considered various factors affecting recycled water sources, supplies, users and demands so that CLWA could develop a cost-effective recycled water system within its service area. In 2015 CLWA updated the RWMP (RWMP Update, Kennedy/Jenks 2016) based on recent developments affecting recycled water sources, supplies, uses and demands. A new Programmatic Environmental Impact Report (EIR) for the RWMP Update was completed in December 2016 and is waiting certification by the CLWA Board of Directors.

CLWA has constructed Phase I of the 2002 RWMP (Kennedy/Jenks 2002), which is designed to deliver up to 1,600 AFY of water to the VWC service area (Phase 1 as constructed currently delivers about 450-500 AFY). Deliveries of recycled water began in 2003 for irrigation water supply at a golf course and in roadway median strips. In 2015, recycled water deliveries were


450 AF. Phase 2 is planned to expand recycled water use within the Santa Clarita Valley and consists of four projects currently in various stages of design.

The RWMP Update includes projects that will provide up to 10,054 AF of treated (tertiary) recycled water suitable for reuse on golf courses, landscaping and other non-potable uses in the Santa Clarita Valley to the extent those supplies are available. All of the available recycled water in the peak summer months would be used to meet demands that include existing Phase 1 projects, Phase 2 expansions currently in design, planned developments (including Newhall Ranch and Vista Canyon) and future nearby customers served by extensions from the Phase 2 system.

The projected future increases in recycled water use beyond 1,600 AFY would require a new contract with the Santa Clarita Valley Sanitation District (SCVSD), and would depend on the amount of effluent available after required discharge to the Santa Clara River, with that discharge based on meeting anticipated instream flow requirements to protect biological resources in the river and potential water rights issues related to downstream legal users of water.

In the 2015 UWMP, as well as in this Plan, existing recycled water use and projections of planned increases are as shown in Table 2-4.

2.1.4.1 Existing and Future Wastewater Treatment Facilities

The SCVSD of Los Angeles County owns and operates two Water Reclamation Plants (WRPs), the Saugus WRP and the Valencia WRP, within the CLWA service area. The Valencia WRP has a current treatment capacity of 21.6 million gallons per day (MGD), equivalent to 24,190 AFY, developed over time in stages. In 2015, the Valencia WRP produced an average of 13.3 MGD (14,900 AFY) of tertiary recycled water. The Saugus WRP has a current treatment capacity of 6.5 MGD (7,280 AFY). In 2015, the Saugus WRP produced an average of 5.1 MGD (5,700 AFY) of tertiary recycled water. The water is treated to tertiary levels and, with the exception of water used in Phase I of the RWMP, is discharged to the Santa Clara River. The Newhall Ranch and Vista Canyon developments are also planning to construct WRPs, and non-potable recycled water from these sources when available may be incorporated directly into the recycled water system. The Newhall Ranch WRP would serve the Newhall Ranch Specific Plan and a new County Sanitation District would be created to operate and maintain the Newhall Ranch WRP. The Newhall Ranch WRP is anticipated to produce 3.7 MGD (4,140 AFY) of recycled water, which would be available to meet a portion of the 7,200 AFY of non-potable demands anticipated for the development at buildout (GSI, 2016). The Vista Canyon Water Factory is proposed as a part of the Vista Canyon Project, and the plant is anticipated to come online in 2017 and would have an ultimate capacity of 0.40 MGD (450 AFY).


TABLE 2-4 AVERAGE/NORMAL YEAR EXISTING AND PLANNED RECYCLED WATER USAGE (AF)

Recycled Water 2020 2025 2030 2035 2040 2045 2050

Existing(a)

450 450 450 450 450 450 450

Planned 565 5,156 7,627 9,604 9,604 9,604 9,604

Total(b)

1,015 5,606 8,077 10,054 10,054 10,054 10,054

Notes: (a) Existing use is actual use in 2015. (b) Recycled water demand projection is based on implementation of complete build-out system described in the

RWMP Update and reflects demands that can cost-effectively be served.

2.1.4.2 Additional Considerations Relating to the Use of Recycled Water

SCVSD Chloride Compliance Plan

Salinity and nutrient management concerns in the Upper Santa Clara River Watershed are primarily driven by salt sensitive crops located downstream. High chloride levels are of particular concern since high value, chloride sensitive crops like strawberries and avocados grown in the lower watershed utilize surface waters or ground water influenced by surface water for irrigation. Findings from previous reports cite the sources of chloride as source waters and residential self-regenerating water-softeners (SRWS). In 2003, SCVSD passed an ordinance banning the installation of all new SRWSs, and by passage of Senate Bill 475, the District has authority to remove all SRWSs remaining in the Santa Clarita Valley that were installed prior to 2003.

A Total Maximum Daily Load (TMDL) for chloride in the Upper Santa Clara River (Reaches 5 and 6) was adopted by the Los Angeles Regional Water Quality Control Board (LARWQCB) and became effective on May 5, 2005. The Basin Plan Amendment for the chloride TMDL in the Upper Santa Clara River was adopted by the LARWQCB on December 11, 2008. The TMDL established waste load allocations of 100 milligrams per liter for the Saugus and Valencia WRPs. The TMDL implementation schedule allows for several special studies to determine whether existing Water Quality Objectives (WQOs) and waste-load allocations for chloride can be revised, and provides for an 11-year schedule to attain compliance with the final water quality objectives and waste-load allocations for chloride.

The SCVSD operates the Saugus WRP and Valencia WRP, which discharge highly treated recycled water to the Santa Clara River. The SCVSD spent more than ten years attempting to achieve the most reasonable chloride limit possible and develop the most cost-effective and environmentally responsible solution. The Draft EIR for their compliance project, released for public review in late 2015 is currently being held up due to a June 2016 court ruling. As a result, the SCVSD has prepared a revised Draft EIR which separates out the recycled water components from their Facilities Plan and solely evaluates the impacts of the proposed chloride compliance plan. This was released for public review in May 2017. In August 2017, the Board of the SCVSD voted to certify this EIR.

The SCVSD anticipates releasing a Notice of Preparation for a supplemental EIR addressing increased diversion of water from the Valencia WRP in the fall of 2017.


Salt and Nutrient Management Plan

The SWRCB adopted a statewide Recycled Water Policy (Policy) on February 3, 2009 to establish uniform requirements for the use of recycled water. The purpose of this Policy is to increase the use of recycled water from municipal wastewater sources that meet the definition in Water Code Section 13050, subdivision (n), in a manner that implements state and federal water quality laws. As part of this Policy, the preparation of a salt and nutrient management plan for each basin/subbasin in California, including compliance with the California Environmental Quality Act (CEQA) and participation by LARWQCB staff is required. The Policy states that salts and nutrients from all sources should be managed on a basin-wide or watershed-wide basis in a manner that ensures attainment of water quality objectives and protection of beneficial uses.

The SWRCB has found that the appropriate way to address salt and nutrient issues is through the development of regional or sub-regional salt and nutrient management plans rather than through imposing requirements solely on individual recycled water projects. These plans must be consistent with the California Water Plan (DWR’s Bulletin 160) as appropriate and must be locally developed. The salt and nutrient plan will include a basin/sub basin-wide monitoring plan that specifies an appropriate network of monitoring locations. The monitoring plan will also be site specific and adequate to provide a reasonable, cost-effective means of determining whether the concentrations of salt, nutrients and other constituents of concern as identified in the salt and nutrient plans are consistent with applicable water quality objectives. CLWA, along with other Upper Santa Clara River Integrated Regional Water Management Plan participants, have prepared a salt and nutrient management plan. The salt and nutrient management plan is intended to fulfill the requirements of the statewide Recycled Water Policy and provide the framework for the environmentally safe disposal of salts and nutrients that occur in the Upper Santa Clara River groundwater basins in compliance with the Basin Plan. The plan will be achieved through the implementation of management measures in areas of the groundwater basin where the salt and nutrient loads would exceed the water quality objectives for the sub-basin if recycled water projects were to be implemented. The plan was completed in 2016 and was approved by the RWQCB; the Basin Plan Amendment was approved by the SWRCB in May 2017.

2.1.5 Groundwater Banking and Exchange Programs

CLWA has improved the overall reliability of its water supplies through the coordinated operation of its multiple water supply sources. These coordinated operations include participation in groundwater banking programs, where surface supplies are stored in groundwater basins in times of surplus for withdrawal in years when other supplies are limited, as well as in water exchanges, where water is provided to an exchange partner in years of surplus for return of supply in a future year.

CLWA is a partner in two existing groundwater banking programs, the Semitropic Banking Program and RRBWSD Banking Program, discussed below in Sections 2.1.5.1 and 2.1.5.2, respectively. Newhall Land is also a partner in the Semitropic Banking Program, as discussed in Section 2.1.5.3, with its supplies assumed to be available to VWC. In addition, CLWA has preliminarily identified the need for an additional, planned banking program, as discussed in Section 2.1.5.4. CLWA is a partner in several water exchanges, discussed in Section 2.1.5.5.


2.1.5.1 Semitropic Banking Program

Semitropic Water Storage District (Semitropic) is a member agency of KCWA and has a contract with KCWA for SWP water, which it provides to farmers for irrigation. Semitropic is located in the San Joaquin Valley in the northern part of Kern County immediately east of the California Aqueduct. Using its available groundwater storage capacity (approximately 1.65 million acre-feet [MAF]), Semitropic has developed a groundwater banking program, in which it takes available SWP supplies from banking partners in wet years and returns that water to them in dry years. For its dry-year returns, Semitropic can either leave its SWP water in the Aqueduct for delivery to a banking partner and increase its groundwater production for its farmers, or Semitropic can pump groundwater that can be pumped into a Semitropic canal and, through reverse pumping plants, be delivered to the California Aqueduct. The total amount of storage capacity under contract in the original banking program is 1 MAF, with approximately 700,000 AF currently in storage. Under its original program, Semitropic can pump back a maximum of 90,000 AFY of water into the California Aqueduct.

Semitropic has recently expanded its groundwater banking program to incorporate its Stored Water Recovery Unit (SWRU). This supplemental program includes an additional storage capacity of 650,000 AF and an expansion of pumpback recovery capacity by 200,000 AFY. That pumpback capacity includes well connections and conveyance facility improvements to increase the existing Semitropic pumpback capacity to the California Aqueduct by an additional 50,000 AFY, and the future development of a new well field with approximately 65 wells along with new collection and transmission facilities to convey an additional 150,000 AFY to the California Aqueduct. CLWA entered into two temporary storage agreements with Semitropic, in 2002 and 2004, storing a portion of its surplus Table A supplies. After consideration for program storage losses, and with CLWA storage withdrawals in 2009, 2010, and 2014, the storage balance available to CLWA was 35,970 AF. In 2015 CLWA entered into an agreement with Semitropic to participate in the SWRU. Under this agreement, the two temporary storage accounts containing 35,970 AF were transferred into this new program. Under the SWRU agreement, CLWA can store and recover additional water within a 15,000 AF storage account. The term of the Semitropic Banking Program extends through 2035 with the option of a 10-year renewal. CLWA may withdraw up to 5,000 AFY from its account.

In the 2015 UWMP and in this Plan, it is assumed that the term of the Semitropic Banking Program will be extended to 2045, and that the water stored in Semitropic will be used for dry-year supply.

2.1.5.2 Rosedale-Rio Bravo Banking Program

Also located in Kern County, immediately adjacent to the Kern Water Bank, RRBWSD has developed a Water Banking and Exchange Program. CLWA has entered into a long-term agreement with RRBWSD with a maximum storage at any point in time of 100,000 AF. Over the life of this project, CLWA may store a total of 200,000 AF in the program. CLWA began storing water in this program in 2005 and reached the maximum storage capacity of 100,000 AF in 2012. Withdrawals from the water bank occurred in 2014 and 2015, but that storage was replaced in 2016, with storage once again at the maximum capacity of 100,000 AF.


Based on CLWA’s experience during the historic dry years of 2014 and 2015, CLWA considers the existing firm withdrawal capacity in this program to be 3,000 AFY. To enhance dry-year recovery capacity, in 2015 CLWA in cooperation with RRBWSD and Irvine Ranch Water District initiated construction of additional facilities that are anticipated to be available in 2018. With these facilities, the firm extraction capacity is estimated to increase to 10,000 AFY even in exceptionally dry conditions such as those experienced in 2014 and 2015. In addition, CLWA has the right under the contract to develop four additional wells which would bring the firm recovery capacity to 20,000 AFY. This additional capacity is anticipated to be available by 2030. In addition to this firm recovery capacity, in moderately dry years Rosedale is required to use up to 20,000 AFY of other available recovery capacity to meet its recovery obligations under the banking agreement.

This project is a water management program to improve the reliability of CLWA’s existing dry-year supplies. In the 2015 UWMP, it was assumed that the extraction capacity of this program would increase from the existing 3,000 AFY capacity to 10,000 AFY in 2017, and to 20,000 AFY in 2030. In this Plan, it is assumed that the capacity increase to 10,000 AFY occurs in 2018.

2.1.5.3 Semitropic Banking Program – Newhall Land

One of Semitropic’s long-term groundwater banking partners is Newhall Land. In its agreement with Semitropic, Newhall Land has available to it a pumpback capacity of 4,950 AFY and a storage capacity of 55,000 AF. At the end of 2015, Newhall Land had a storage balance of 32,507 AF. Newhall Land entered into this banking program in anticipation of the development of Newhall Ranch. Under its agreement with Semitropic, Newhall Land may assign its rights to this program to CLWA. It is assumed for planning purposes that Newhall Ranch will be developed at some time in the future and that Newhall Land’s rights in this banking program will be transferred to CLWA at the time of development. In the meantime, it is assumed that Newhall Land will make its withdrawal capacity in this program available to CLWA for withdrawal of CLWA’s own stored water supplies, as occurred in 2009 and 2014. This supply is assumed to be available to VWC and is planned to be used only in dry years.

2.1.5.4 Other (Planned) Banking

Based on analysis of water demands and supplies, it was determined that an additional banking program may be needed after 2045 to replace the Semitropic Banking Program. A specific banking program was not identified. In the 2015 UWMP, CLWA assumed development of additional groundwater banking programs with a pumpback capacity of at least an additional 5,000 AFY for use in a single-dry year and multiple-dry year period, with supplies available after 2045.

2.1.5.5 RRWBWD and West Kern Water Exchanges

In addition to groundwater banking programs, short-term water exchanges may also serve as a means to enhance water reliability. In 2011 CLWA entered into two unbalanced exchange agreements, each with a ten-year term. CLWA executed a Two-for-One Water Exchange Program with RRBWSD where CLWA can recover one acre-foot of water for each two acre-feet CLWA delivered to RRBWSD (less losses). CLWA delivered a total of 19,571 AF under this program in 2011 and 2012, and after program losses, there is 9,441 AF of recoverable water. Up to this entire amount may be recovered in a single year when requested by CLWA and when SWP exchange water is available from RRBWSD.


CLWA also entered into a Two-for-One Water Exchange Program with the West Kern Water District (WKWD) in Kern County. CLWA delivered 5,000 AF in 2011, resulting in a recoverable total of 2,500 AF. After CLWA withdrew 2,000 AF in 2014, this exchange program has a remaining balance of 500 AF. Up to this entire amount may be recovered in a single year when requested by CLWA and when SWP exchange water is available from WKWD.

Supply available under these programs is planned for dry-year use, and is assumed to be available through 2021.

2.2 Existing and Projected Water Demands

In 2015 the Santa Clarita Valley Family of Water Suppliers updated the Santa Clarita Valley Water Use Efficiency Strategic Plan (WUESP) to assess existing and planned water conservation in the Valley necessary to meet SBX7-7 demand reductions that call for a 20 percent reduction in per capita demand by 2020.

As part of that effort, data on existing land uses and planned land use development were compiled from each of the retail water purveyors and the City of Santa Clarita and County of Los Angeles land use plans in order to estimate demand projections out to 2050 (assumed year of designated land use-buildout). In addition, weather and water conservation effects on water usage were considered in the evaluation.

An analysis was performed that combined growth projections with water use data to forecast total water demand in future years. The demand projections include econometric modeling and plumbing code changes, and the demand projections assume that water conservation programs identified in the 2015 WUESP will be implemented.

A land use based approach was used (that incorporates information from a population-based approach) because such an approach can further reflect assumptions regarding how future development is planned. It can also demonstrate how water usage patterns have evolved from what they were in the past as the Santa Clarita Valley approaches build-out. The projections take results from updated econometric models developed for the purveyors in the 2015 WUESP to project demand to 2020, transitioning to a land use-based approach for 2020 through 2050 (assumed buildout) based on data provided by the purveyors and as contained in local land use plans supplied by the county and city. The land use-based demand forecast was conducted for three of the four retail purveyors; NCWD, SCWD, and VWC. Sufficient data was not available to conduct the land use-based analysis for LACWWD 36; that assessment relies on a population based demand forecast.

The demand forecast provides an assessment of demands that include quantification of savings from passive conservation (e.g., plumbing codes, standards, and ordinances) and active conservation. This was done so that each retailer can evaluate what its future demand would likely be if the retailer did not undertake any active conservation programs between now and 2050. In addition, SBX7-7 requires urban water agencies to reduce statewide per capita water consumption 20 percent by 2020, which may be achieved through both passive conservation savings and active conservation programs.

The results of this analysis, presented in more detail in the 2015 UWMP, are summarized below. Table 2-5 provides a summary of projected total water demands, including projected


savings from passive conservation, through 2050. Active conservation programs identified and evaluated in the 2015 WUESP to meet the SBX7-7 conservation requirements are also reflected in the demands shown. In this Plan, it is the demands with plumbing code savings and active conservation that are used to evaluate supply reliability.

TABLE 2-5 NORMAL YEAR SBX7-7 DEMANDS (AF)

2020 2025 2030 2035 2040 2045 2050

Regional Water Demands (a)

Demand w/out Plumbing Code Savings 79,400 90,100 100,400 109,500 113,900 118,300 122,700

Demand w/ Plumbing Code Savings 76,700 84,800 92,700 100,000 103,400 106,800 110,400

Demand w/ Plumbing Code Savings and Active Conservation 68,900 74,600 80,800 86,100 88,500 90,900 93,900

Notes: (a) From MWM 2015.


Section 3: Water Supply Reliability Analysis

For this Plan, an analytic spreadsheet model was used to evaluate the reliability of existing and planned water supplies in meeting projected demands in the CLWA service area during the study period of 2017 through 2050. The model is described generally in Section 3.1, and in more detail in Appendix A.

Four supply scenarios are evaluated in this Plan, including a Base Scenario, based on the water supplies, storage programs, and demand projections described in the 2015 UWMP, and three additional scenarios with differing supply assumptions. These scenarios are discussed in more detail in Section 3.2.

Analysis results include an initial assessment of supply reliability for each of the four scenarios evaluated. For any scenario in which reliability was less than the 95 percent reliability goal, additional supply programs were included as needed to achieve that reliability goal. The results of initial scenario supply reliability, the discussion of any additional supply programs needed, and the resulting improvement in reliability are discussed in Section 3.3.

3.1 Water Operations Model

3.1.1 General Methodology

The Water Operations Model (or “Model”) is an analytic spreadsheet model developed for CLWA by MBK Engineers that was used to analyze water supply reliability for this Plan. The Model performs annual water operations for the CLWA service area over a specified study period, which for this Plan is the 34-year period from 2017 through 2050 (the year assumed in the 2015 UWMP for development buildout in the service area as shown in adopted local land use plans).

Inputs to the Model include:

Annual service area demands, as they are projected to increase over the study period,

Annual base supplies (existing and planned) anticipated to be available to meet those demands, including any planned changes in supply during the study period, and

Storage programs available to CLWA, including maximum storage and extraction capacities and beginning (2017) storages.

The Model steps through each year of the study period, compares annual base supplies to demands, and operates CLWA storage programs as needed, adding to storage in years when base supplies exceed demand and withdrawing from storage when demand exceeds base supplies.

To reflect the uncertainty in what hydrology might occur over the study period, the Model looks at multiple hydrologic sequences. In this Plan, the sequences are based on historical hydrology from 1922 through 2003, and the Model uses 82 hydrologic sequences, as is discussed further in Subsection 3.1.2. The hydrologic sequences affect certain supplies (i.e., SWP and


groundwater), as well as demands during the study period. The Model steps through annual operations over the study period for each of the 82 hydrologic sequences. Results from the 82 sequences are then compiled by year during the study period, and are summarized to provide a statistical assessment of various parameters.

For example, the reliability of CLWA’s supplies and storage programs to meet its projected demands for a particular year, such as year 2030, would be assessed by compiling the overall supply surplus or shortfall that occurred in Model results for 2030 from each of the 82 hydrologic sequences. Those 82 supply results for 2030 would then be sorted from large to small to provide a probability of exceedance distribution for overall supplies for that year.

3.1.2 Hydrologic Variability

Of the many factors affecting this reliability analysis, the factor with the greatest degree of variability and with the largest impact on supplies (and to a lesser degree, demands) is hydrology. Hydrology in northern California significantly affects the availability of SWP supplies; local hydrology affects the availability of Alluvial groundwater supplies, as well as demands; and dry-year reductions in SWP supplies affect the need for additional Saugus groundwater pumping.

The SWP supply data used in this analysis is based on the results of SWP modeling studies conducted by DWR using CalSim, a computer model that simulates monthly operations of the SWP and CVP systems. Among other model inputs, CalSim uses hydrologic inflows to the SWP and CVP systems based on 82 years of historical monthly inflows from 1922 through 2003, adjusted to reflect current levels of development in the water supply source areas.

To reflect the potential variability in hydrology over the study period, for this analysis a number of hydrologic sequences are used, based on the same historical hydrologic period used in the CalSim studies. Based upon the 82 years of hydrologic record used in CalSim, a series of 82 hydrologic “traces” is used. Each trace consists of 34 years of sequential hydrology, with the beginning year of each trace lagging the beginning year of the previous trace by one year. For example, the first trace begins with 1922 hydrology assumed for the first year of the study period of 2017, 1923 hydrology for 2018, etc., through 1955 hydrology for the last year of the study period of 2050. The hydrology is shifted by one year for the second trace, beginning with 1923 hydrology for 2017, 1924 hydrology for 2018, etc., through 1956 hydrology for 2050. This one-year shift continues until the end of the hydrologic period (2003) is reached, where the data begins “wrapping” back to 1922 hydrology. The end result of this process is 82 traces of hydrology.

Each hydrologic trace is used to analyze CLWA supply and demand performance over the study period – in other words, if that sequence of hydrology were to occur again, how adequate would the supplies associated with that hydrology and the storage programs in place be in meeting demands over the study period? Annual results during the study period from each of the 82 hydrologic traces are compiled and summarized, and are used to provide a statistical assessment of CLWA supply reliability.


SWP Supplies

As mentioned above, the SWP supply data used in this analysis is taken from SWP modeling studies conducted by DWR using their CalSim computer model, which simulates monthly operations of the SWP and CVP systems. In addition to the 82 years of historical monthly inflows discussed above, input to the CalSim model includes the facilities in the system, and regulatory and operational constraints on system operations. CalSim studies use a fixed set of facilities, operating requirements/constraints, and water demands, operated over a number of years using historical hydrology. The resulting supply deliveries from a CalSim study provide an indication of the potential supply reliability of the SWP system, based on the particular set of facilities and operating constraints assumed in that study.

Hydrology is the factor with the largest impact on SWP supplies. A given CalSim study captures the hydrologic variability in SWP supplies, but not the effect of changes in SWP facilities or operating constraints. For changes in SWP facilities or operations, separate CalSim studies are conducted.

For this Plan, what is desired are potential supplies over a study period (i.e., the 34-year period from 2017 through 2050) with conditions such as CLWA demands, supplies, and storage programs changing over the study period. The use of the 82 hydrologic sequences is employed in this Plan to capture the hydrologic variability in SWP supplies. The effect of differing assumptions regarding SWP facilities and operating constraints is assessed by using a different CalSim model study as input to the Model for each of the four scenarios evaluated in this Plan, as is discussed in more detail in Section 3.2.

All of the CalSim studies used in this Plan also reflect changes to hydrology expected to result from climate change, specifically, a 2025 emission level and a 15 cm sea level rise. However, note that, consistent with the way CalSim studies are conducted, this is the expected effect of climate change through 2025 with that effect applied to all 82 years of historical monthly inflow (and not the increasing effects of climate change projected to occur through 2050).

Groundwater Supplies

Local hydrology affects the availability of Alluvial Aquifer groundwater supplies, as a result of lowered groundwater levels in the eastern part of the Basin during dry periods. The groundwater operating plan for the Saugus Formation includes increased pumping in response to the availability of other supplies, particularly dry-year reductions of SWP supplies. As discussed above, SWP supplies, and therefore Saugus pumping needs, are dependent on hydrology in northern California.

As part of the Basin Yield Analysis (LSCE & GSI, 2009), a groundwater model was used to analyze the groundwater operating plan over an extended hydrologic period. The Basin Yield Analysis used a DWR model study of SWP supply availability to assess Saugus pumping needs, and so used the same 82-year historical hydrologic period of 1922 through 2003 as used in CalSim. The groundwater modeling conducted in the Basin Yield Analysis used this same 82-year period to simulate both the Alluvium and the Saugus Formation, evaluating Alluvial pumping based on local hydrology during that period, and Saugus pumping based on hydrology in northern California.


Demands

Demands are also affected by local weather, with lower or higher than normal demands occurring when local conditions are either wet or dry, respectively. As with supplies, the hydrologic effects on demands are incorporated into the Model through use of the 82 hydrologic traces. When a dry year occurs in a particular hydrologic trace, demand is increased from normal-year amounts, and in a wet year is reduced.

3.1.3 Reliability Determination

For this Plan, CLWA specified a reliability goal of 95 percent. The manner in which a reliability goal is applied to the Water Operations Model is as follows:

The Model steps through each year of the study period, compares annual base supplies to demands, and operates CLWA storage programs as needed, adding to storage in years when base supplies exceed demand and withdrawing from storage when demand exceeds base supplies.

The resulting annual supply surplus or shortfall is determined for each year during the study period.

This is done for each of the 82 hydrologic sequences.

The supply surplus/shortfall from all 82 sequences is compiled for each year during the study period. For example, annual supply surplus/shortfall results for study period year 2040 are pulled from each of the 82 hydrologic sequences, and that data is then used to determine the reliability for year 2040.

As the 95 percent reliability goal is applied to the Water Operations Model, this is defined as the ability to meet demand in a given year in 95 percent of the hydrologic sequences analyzed. Based on the number of hydrologic sequences analyzed, this means that to meet the 95 percent reliability goal for a given year, demands for that year must be met in at least 78 of the 82 sequences (95 percent of 82 sequences).

3.1.4 Interpretation of Water Operations Model Results

The Model produces graphs for a number of parameters calculated within the Model, generally presented in the form of probability of exceedance graphs. The parameters of primary interest for this Plan include: (1) Base supply minus demand (i.e., the supply surplus or shortfall for a given year after summing all base supplies and subtracting weather-adjusted demand), and (2) Supply after storage program puts and takes (i.e., the remaining supply surplus or shortfall for a given year after any additions to (puts) or withdrawals from (takes) storage programs). Base supplies are considered to be supplies that are available every year, such as supplies from the SWP, groundwater, recycled water, Buena Vista/Rosedale-Rio Bravo, and Nickel water. Storage programs, as used here, include SWP flexible storage, groundwater banking programs, and any other dry-year supplies, such as water under the Yuba Accord.


An example of these two parameters for a given year in the study period is shown in Figure 3-1, with ‘Base supply minus demand’ represented by the black dashed line, and ‘Supply after storage puts and takes’ represented by the solid black line. The area between these two lines that is above zero on the supply (vertical) axis represents the amount of water put into storage programs, whereas the area between the two lines that is below zero represents the amount of takes from storage programs. The darker blue area (below the ‘Supply after storage puts and takes’ line that is above zero on the supply axis) indicates the amount of surplus water that remains after all possible puts to storage programs, where puts may be constrained by vacant storage space available or by put capacity. This remaining supply would be available for water sales, exchanges, or storage in new programs, or would otherwise remain unused. The darker rust-colored area (above the ‘Supply after storage puts and takes’ line that is below zero on the supply axis) indicates the amount of supply shortfall that remains after all possible takes from storage programs, where takes may be constrained by the amount of water stored or by take capacity. The reliability for this scenario is the probability of exceedance at the point where the left side of the darker rust-colored area crosses zero on the supply axis (shown as the dotted vertical line in this graph). For this particular example, that occurs at about 92 percent, and is interpreted as a 92 percent probability that remaining supplies after puts and takes would be zero or greater for this example’s supply and demand scenario and study period year; or in other words, has a reliability of 92 percent. The reliability in this example does not meet the 95 percent reliability goal (shown as the dashed vertical line in this graph), and so would require additional programs or supplies to achieve that goal.


FIGURE 3-1 INTERPRETATION OF MODEL RESULTS

In this Plan, it is the supply that remains after operation of the storage programs that is of primary interest. Therefore, the figures throughout the remainder of this section showing supplies show only the ‘Supply after storage puts and takes’ line, and so are of the form shown in Figure 3-2. The supply figures in the rest of this section do not include the shading of surplus and shortfall as shown in Figure 3-2, but are interpreted as shown here.


FIGURE 3-2 FORM OF MODEL RESULTS PRESENTED

3.2 Scenarios Analyzed

3.2.1 Scenario Descriptions

This Plan includes evaluation of four scenarios, described generally as follows:






3.2.2 Scenario Assumptions

The Base Scenario and its demand and supply projections serve as the starting point for Scenarios A through C. Base Scenario demand and supply assumptions are described in detail in Section 2. Scenarios A through C include varying assumptions regarding the availability of SWP, groundwater, and recycled water supplies, and are discussed further below. The demand and supply assumptions for all four scenarios are summarized in Table 3-1. A more detailed listing of assumptions is included in Appendix A.

One of the primary differences between scenarios is with regard to assumed SWP supply availability. Each scenario uses data from a separate DWR model study, with each model study based on differing assumptions regarding SWP facilities (existing, or proposed California WaterFix) and regulatory constraints (existing, or with varying additional requirements). As was mentioned above, all of the DWR model studies used in this Plan use hydrology adjusted for the effects of climate change estimated to occur by 2025. DWR model study results for each of the four scenarios are included in Figure 3-3, which shows SWP Table A supply allocations projected to be available to SWP contractors. As described in Section 2.1.1.4, the graph can be interpreted as the probability of SWP Table A allocations exceeding a given percentage. CLWA’s Table A Amount of 95,200 AFY is multiplied by these allocation percentages to determine the amount of Table A supplies projected to be available to CLWA.

Note that the 2015 UWMP, and therefore the Base Scenario, includes several planned additions to groundwater banking programs that are not included in Scenarios A through C. These include the planned increase in take capacity at Rosedale-Rio Bravo Banking Program from 10,000 AFY to 20,000 AFY, the planned transfer to CLWA of Newhall Land’s Semitropic Banking Program, and a planned new groundwater banking program with 5,000 AFY of take capacity. These planned additions from the 2015 UWMP are excluded from Scenarios A through C so that they can be evaluated as part of this Plan, including whether such additions are needed, and if so, the timing of needed additions. Further, Scenarios A through C also exclude dry-year supplies available under the Yuba Accord.

3.2.2.1 Base Scenario

The Base Scenario is based on the same demand, supply, and storage program assumptions included in the 2015 UWMP. Base Scenario assumptions are discussed in detail in Section 2, and are summarized in Table 3-1.

As discussed in Section 2.1.1.4, the Base Scenario includes SWP supply availability based on existing SWP facilities and regulatory constraints. SWP supplies are taken from DWR’s Early Long-Term (ELT) scenario model study, from DWR’s 2015 DCR. The reliability of SWP Table A supplies for the Base Scenario is shown in Figure 3-3.


3.2.2.2 Scenario A

Scenario A is similar to the Base Scenario, with differences primarily in SWP supplies. Assumptions for Scenario A are summarized in Table 3-1, and differ from the Base Scenario as follows:

SWP supplies: Scenario A includes SWP supply availability based on the proposed California WaterFix conveyance facilities, along with the regulatory constraints anticipated for those facilities. SWP supplies for Scenario A are taken from the DWR model study for the Preferred Alternative in the BDCP/California WaterFix Final EIR/EIS (DWR and USBR, December 2016). The reliability of SWP Table A supplies for Scenario A is shown in Figure 3-3.

Dry-year supply programs: As noted above, Scenarios A through C exclude those planned additions to groundwater banking programs that were included in the 2015 UWMP and the Base Scenario, as well as dry year supplies under the Yuba Accord.

3.2.2.3 Scenario B

Scenario B includes moderate supply reductions relative to the Base Scenario. Assumptions for Scenario B are summarized in Table 3-1, and differ from the Base Scenario as follows:

SWP supplies: SWP supply availability for Scenario B is based on existing SWP facilities, with a moderate increase in Delta outflow requirements. SWP supplies for Scenario B are taken from DWR’s Existing Conveyance Low Outflow (ECLO) scenario model study, from DWR’s 2015 DCR. The reliability of SWP Table A supplies for Scenario B is shown in Figure 3-3.

Saugus supplies: Scenario B includes a smaller planned increase in Saugus dry-year pumping capability. The Base Scenario includes a planned increase in Saugus dry-year pumping capability due to the restoration of VWC Well 201, as well as the construction of replacement and new wells, for a total Saugus dry-year pumping capability of 33,200 AFY. In Scenario B, VWC Well 201 is assumed to be restored, but no replacement or new wells constructed, resulting in Saugus dry-year pumping limited to 23,640 AFY.

Recycled water: Scenario B includes a smaller planned increase in the use of recycled water. The Base Scenario includes a planned increase in recycled water use to 10,054 AFY by 2035. Scenario B assumes a smaller increase – to 7,315 AFY by 2030. This lower amount includes demand for recycled water based on CLWA’s current contract with the SCVSD, and projected demand for Newhall Ranch West Side Communities.


3.2.2.4 Scenario C

Scenario C includes larger supply reductions relative to the Base Scenario. Assumptions for Scenario C are summarized in Table 3-1, and differ from the Base Scenario as follows:


SWP supplies: SWP supply availability for Scenario C is based on existing SWP facilities, with a larger increase in Delta outflow requirements. SWP supplies for Scenario C are taken from DWR’s Existing Conveyance High Outflow (ECHO) scenario model study, from DWR’s 2015 DCR. The reliability of SWP Table A supplies for Scenario C is shown in Figure 3-3.

Alluvial supplies: Scenario C assumes reductions in Alluvial groundwater supplies based on the potential effects of climate change. The Alluvial supplies in Scenario C were developed by GSI Water Solutions, Inc. (GSI), based on a climate change scenario with more below-average rainfall years, droughts of longer duration, and less frequent above-normal rainfall years, and the anticipated reduction in Alluvial supplies that would result from such changes. This climate change scenario and the effect on Alluvial supplies is described in a Technical Memorandum (GSI, 2017) included in Appendix B.

Saugus supplies: Scenario C assumes no dry-year increase in pumping from the Saugus. The Base Scenario includes normal-year pumping amounts of 10,685 AFY, with periodic dry-year increases in pumping. In Scenario C, pumping from the Saugus is assumed to be limited to normal-year pumping amounts of 10,685 AFY in all years.

Recycled water: Scenario C includes a smaller planned increase in the use of recycled water. The Base Scenario includes a planned increase in recycled water use to 10,054 AFY by 2035. Scenario C assumes a smaller increase – to 6,585 AFY by 2030. This lower amount includes existing demand for recycled water plus projected demand for Phase 2D and Vista Canyon, as well as projected demand for Newhall Ranch West Side Communities.



TABLE 3-1 SCENARIO ASSUMPTION SUMMARY

BASE

SCENARIO SCENARIO A SCENARIO B SCENARIO C

DEMANDS

Demand w/ active conservation:

per UWMP X X X X

SUPPLIES

Groundwater

Alluvium:

per UWMP X X X

w/ climate change effects X

Saugus:

per UWMP (existing, restored, replacement, and new wells)

X X

existing and restored wells X

normal-year pumping only X

Recycled Water

Recycled water:

per UWMP (up to 10,054 AFY) X X

up to 7,315 AFY X

up to 6,585 AFY X

Imported Supply

SWP Table A:

per UWMP – existing facilities and operational requirements

X

w/ California WaterFix X

existing facilities w/ additional low outflow requirement

X

existing facilities w/ additional high outflow requirement

X

SWP flexible storage:

per UWMP X X X X

Buena Vista – Rosedale:

per UWMP X X X X

Nickel water:

available 2022-2050 X X X X

Yuba Accord:

per UWMP X

Banking/Exchange Programs

Semitropic Bank:

per UWMP X X X X

Semitropic – NL Bank:

per UWMP X

Rosedale Bank:

per UWMP (up to 20,000 AFY take capacity by 2030)

X

Take capacity up to 10,000 AFY X X X

New Bank:

per UWMP (5,000 AFY take capacity in 2046)

X

Rosedale & W Kern Exchanges:

per UWMP X X X X


FIGURE 3-3 SWP TABLE A SUPPLY RELIABILITY


3.3 Analysis Results

3.3.1 Initial Reliability Results

An initial analysis was conducted to determine the reliability of each of the four supply scenarios, based on the specific scenario assumptions identified in Section 3.2.

3.3.1.1 Summary Results

Based on the assumptions in each scenario, the 95 percent reliability goal is met over the entire study period for three of the four scenarios, namely the Base Scenario, Scenario A, and Scenario B. The reliability goal for Scenario C is met through 2035. However, after 2035, Scenario C reliability begins to fall, decreasing to about 86 percent by 2050. A summary of initial results for each scenario is presented in Figure 3-4.

FIGURE 3-4

SUMMARY OF INITIAL RELIABILITY

In the subsections that follow, more detailed results are presented for each scenario, including the full range of probability for available supplies, for years 2020, 2030, 2040, and 2050. Note that the supply results presented below are ‘Supply after storage puts and takes,’ as shown in


Figure 3-2. Positive supply values represent surplus water that remains after all possible puts to storage programs. This remaining supply would be available for water sales, exchanges, or storage in new programs, or would otherwise remain unused. Supply values of zero occur when all available supplies are stored, or when demand is just met. Negative supply values indicate a supply shortfall.

3.3.1.2 Base Scenario

Results for the Base Scenario indicate that for the demand and supply assumptions included in this scenario, there are no supply shortfalls for any of these four years during the study period. Therefore, reliability is 100 percent in all of these years, which exceeds the reliability goal of 95 percent. These results are shown in Figure 3-5.

FIGURE 3-5

BASE SCENARIO RELIABILITY


3.3.1.3 Scenario A

Results for Scenario A indicate that for the demand and supply assumptions included in this scenario, there are no supply shortfalls for 2020, 2030, and 2040. The reliability for these three years is 100 percent. The results for 2050 show a minor probability of a small shortfall of about 600 AF. The reliability for 2050 is 98 percent. The reliability for all four of these years exceeds the reliability goal of 95 percent. These results are shown in Figure 3-6.

FIGURE 3-6 SCENARIO A RELIABILITY


3.3.1.4 Scenario B

Results for Scenario B indicate that for the demand and supply assumptions included in this scenario, there are no supply shortfalls for 2020, 2030, and 2040. The reliability for these three years is 100 percent. The results for 2050 show a small probability of a shortfall as high as about 9,000 AF. The reliability for 2050 is 95 percent. The reliability for all four of these years exceeds or meets the reliability goal of 95 percent. These results are shown in Figure 3-7.

FIGURE 3-7

SCENARIO B RELIABILITY


3.3.1.5 Scenario C

Results for Scenario C indicate that for the demand and supply assumptions included in this scenario, there are supply shortfalls in each of the four years 2020, 2030, 2040, and 2050. The results for 2020 and 2030 show a small probability of a shortfall, with a shortfall as high as 2,300 AF in 2020, and as high as 4,000 AF in 2030. The reliability for 2020 and 2030 is 96 percent. The results for 2040 show a larger probability of shortfall, in amounts as high as nearly 9,700 AF. The reliability for 2040 is 92 percent. The results for 2050 show an even larger probability of shortfall, in amounts as high as about 24,300 AF. The reliability for 2050 is 86 percent. For Scenario C, the 95 percent reliability goal is met in 2020 and 2030, but is not met in 2040 and 2050. These results are shown in Figure 3-8.

FIGURE 3-8

SCENARIO C INITIAL RELIABILITY


3.3.2 Additional Supply Needs

3.3.2.1 Amount and Timing of Needs

As noted in Section 3.3.1, the 95 percent reliability goal is met over the entire study period for the Base Scenario, Scenario A, and Scenario B. Therefore, no additional storage programs or supplies are needed or considered for these three scenarios.

This is not the case, however, for Scenario C. The reliability goal for Scenario C is met through 2035. However, after 2035, Scenario C reliability begins to fall, dropping to about 86 percent by 2050. This is shown in Figure 3-8, and in more detail in Figure 3-9. Figure 3-9 shows a focused view of the shortfall in Scenario C (a view zoomed in on the lower right portion of Figure 3-8), and shows only the last 20 years of the study period, when shortfalls are largest. As shown in Figure 3-9, the shortfall at the 95 percent probability of exceedance is about 2,300 AF in 2040, 8,000 AF in 2045, and 14,500 AF in 2050. To meet the reliability goal, these shortfalls at 95 percent probability of exceedance need to be reduced to zero, and represent the amount of additional dry-year supply needed to achieve the reliability goal for Scenario C over the entire study period.

FIGURE 3-9 SCENARIO C INITIAL RELIABILITY: DETAIL OF SUPPLY SHORTFALL


3.3.2.2 Additional Supplies Considered

The additional storage programs and supplies that were considered for supply evaluation for additional Scenario C supplies include:

Groundwater Banking Programs

Rosedale-Rio Bravo Banking Program – increased take capacity: Under CLWA’s existing contract with RRBWSD for this program, CLWA has the right to develop four additional extraction wells, which would bring the firm recovery capacity under this program from 10,000 AFY to 20,000 AFY. This increase would provide additional dry-year access to the water CLWA stores in this existing program, which has a maximum storage capacity of 100,000 AF (and is currently full). This additional take capacity was included in the 2015 UWMP as a planned banking supply increase, assumed in that document to be available by 2030, but was not included in the initial analysis of Scenario C.

Semitropic Banking Program – Newhall Land: Newhall Land participates in a groundwater banking program with Semitropic in which it has a pumpback capacity of 4,950 AFY and a storage capacity of 55,000 AF. Newhall Land entered into this banking program in anticipation of the development of Newhall Ranch. Under its agreement with Semitropic, Newhall Land may assign its rights to this program to CLWA. However, the terms for such an assignment have yet to be determined. In the 2015 UWMP, it was assumed that Newhall Ranch would be developed and that Newhall Land’s rights in this banking program would be transferred to CLWA at the time of development, and that prior to that time the take capacity under this program would be available to CLWA. This program, including interim access to take capacity, was excluded from the initial assessment of Scenario C.

New groundwater bank: In the 2015 UWMP, additional groundwater banking programs with a take capacity of 5,000 AFY were assumed to be developed, with supplies assumed to be available after 2045. No specific programs were identified in the UWMP, although a number of groundwater banking programs in various stages of planning and development, or new programs yet to be defined, could provide this supply. This planned supply was not included in the initial assessment of Scenario C.

Willow Springs Water Bank, Antelope Valley: This project is located in eastern Kern County, in the northern portion of the Antelope Valley. It is adjacent to both the East Branch of the California Aqueduct and the Los Angeles Aqueduct. This program is active and is seeking participants.

Antelope Valley-East Kern Water Agency High Desert Water Bank: This is a project proposed by the Antelope Valley-East Kern Water Agency (AVEK), a SWP wholesaler located in the Antelope Valley area of southeastern Kern County and northern Los Angeles County. The proposed groundwater banking project would be developed and operated by AVEK, and would be located adjacent to the East Branch of the California Aqueduct. As proposed, the project would have a total storage capacity of 280,000 AF, with recharge and recovery capacities of 70,000 AFY. AVEK is currently conducting pilot testing, and the environmental analysis for the proposed project is in process. AVEK is actively seeking banking partners.


Palmdale Regional Groundwater Recharge and Recovery Project: The Palmdale Water District (PWD), a SWP wholesaler, is implementing a large-scale groundwater recharge and recovery project located adjacent to the East Branch of the California Aqueduct. The project will obtain water for recharge from the SWP and also from recycled water produced by the Los Angeles County Sanitation District Palmdale Water Reclamation Plant. CLWA could be a potential partner in the project by banking excess supply in wet years and recovering that supply in dry years.

Saugus Formation Aquifer Storage and Recovery (ASR) Program: The feasibility of implementing an ASR program in the Saugus Formation has been evaluated through field testing and groundwater modeling simulations. Reconnaissance-level analysis indicates that such a program is feasible. In addition to water reliability benefits, a Saugus ASR program could provide other operational benefits (e.g., higher groundwater levels) and local storage.

Groundwater Replenishment with Recycled Water: The feasibility of using recycled water for a groundwater recharge program in the eastern portion of the Alluvium has been evaluated in the Water Supply Measures Reconnaissance Study and further refined in the draft RWMP. A recycled water recharge project could provide operational benefits (e.g., higher groundwater levels in the Alluvium), increased recycled water usage and greater water recovery from the Alluvium in eastern parts of the groundwater basin. Conceptual design for the project is an extension of the proposed Phase 2A recycled water pipeline, with approximately 5,000 AFY of recycled water from the Valencia WRP discharged to a recharge basin adjacent to the Santa Clara River, and average recovery of 3,500 AFY from downstream Alluvial wells.

Additional Supplies

Sites Reservoir: Sites Reservoir is a planned surface water reservoir that would be located north of the Delta to the west of the Sacramento River. CLWA has contributed to planning studies for this reservoir. Use by CLWA for supplies from this reservoir would likely be limited to dry years, when SWP supplies are limited and capacity is more likely to be available at the SWP’s Delta pumping plant to pump this non-SWP water.

3.3.2.3 Assessment of Initial Supply Use

To help determine which of the additional supplies described above to select for further analysis, a preliminary assessment of use of CLWA’s initial supplies and storage programs for Scenario C was conducted. The intent was to look at the availability of surplus supplies during the study period – to assess the need for additional supplies versus increased use of dry-year storage – as well as the efficiency of existing storage programs usage.

As was shown in Figure 3-8, for Scenario C the amount of surplus supply exceeds the amount of shortfall throughout the study period. This is quantified in Figure 3-10, which shows the average annual supply surplus and average annual supply shortfall during the study period, at five-year increments. Even with the reduced supplies included in the assumptions for Scenario C, the average supply surplus greatly exceeds average shortfall throughout the study period. While the ratio of average surplus-to-shortfall decreases over time, that ratio is still more than four-to-one in 2050. Given this, it appears that rather than acquiring additional base or dry-year


supply, better management of existing supplies through expanded use of existing or new storage programs might be more advantageous.

FIGURE 3-10 SCENARIO C INITIAL RELIABILITY:

AVERAGE ANNUAL SUPPLY SURPLUS AND SHORTFALL

Model results of total storage in CLWA banking and exchange programs for Scenario C are shown in Figure 3-11. Even with the reduced supplies included in Scenario C, storage levels remain full or high throughout the entire study period. For example, results for 2050 show about a 35 percent probability of storage being full, with a minimum storage in that year of about 58,000 AF. The conclusion here is that there is adequate storage in existing programs to meet supply shortfalls, but existing take capacities are limiting the ability to withdraw that storage.


FIGURE 3-11 SCENARIO C INITIAL RELIABILITY:

TOTAL BANKING AND EXCHANGE PROGRAM STORAGE

This conclusion is supported by a closer look at individual storage programs, specifically at SWP flexible storage, the Semitropic Banking program, and the Rosedale-Rio Bravo Banking program, as shown in Figures 3-12, 3-13, and 3-14, respectively. Priority for use of these storage programs in the Model in the case of a supply shortfall, and as they have generally been used in actual operations, is withdrawals are first made from SWP flexible storage, then Semitropic, and then Rosedale.

SWP flexible storage is the smallest of these storage programs, with CLWA access to 4,684 AF of SWP water stored in Castaic Lake. CLWA can withdraw any or all of this amount in a given year, and has five years to replace any withdrawal. Through an agreement with Ventura County SWP contractor agencies, CLWA has access to an additional 1,376 AF through 2025. As is shown in Figure 3-12, when water from this storage is needed, the entire storage is typically completely withdrawn. Withdrawals are generally completely replaced a year or two later.


Usage of the program is shown to increase over the study period, with about an 83 percent probability of full storage in 2020, decreasing to about 58 percent by 2050.

FIGURE 3-12 SCENARIO C INITIAL RELIABILITY: SWP FLEXIBLE STORAGE

The Semitropic groundwater bank includes two components: a recent program with a storage capacity of 15,000 AF and 5,000 AFY of both put and take capacity, and nearly 36,000 AF of recoverable water stored under two previous temporary programs. Both components of this program use the same firm 5,000 AFY take capacity. The term for this program extends through 2035 with the option of a 10-year renewal. In this analysis, the program was assumed to be available through 2045. As the program was modeled, no supplies were added to storage until the existing 36,000 AF of previous storage was completely withdrawn. The results of this modeling for the Semitropic Bank are shown in Figure 3-13. As modeled, there is about a 65 percent probability of the existing storage remaining unused by 2020, and nearly a 40 percent probability by 2030. By 2040, that probability decreases to about 10 percent, but there is still a 50 percent probability of storage greater than about 27,000 AF. By 2045, the last year of the program, there is only about a 10 percent probability that all of the existing storage is used. Without another extension of the term of this program, or further action to withdraw and make use of this existing storage, any remaining storage would likely become a stranded asset.


FIGURE 3-13 SCENARIO C INITIAL RELIABILITY: SEMITROPIC BANK STORAGE

The Rosedale-Rio Bravo groundwater bank is CLWA’s largest storage program, with a storage capacity and current storage of 100,000 AF. As shown in figure 3-14, there is nearly a 90 percent probability that storage in the Rosedale-Rio Bravo Bank is full in 2020 and 2030, and about a 70 percent probability in 2040. Even in 2050, five years after the Semitropic Banking program is assumed to end, there is nearly a 40 percent probability that Rosedale-Rio Bravo Bank storage is full. In spite of this storage, supply shortfalls still occur in Scenario C, which indicates that when a shortage occurs, storage cannot be withdrawn in large enough quantities. As noted in Section 3.2.2, the planned increase in Rosedale take capacity from 10,000 AFY to 20,000 AFY that was included in the 2015 UWMP was not included in assumptions for Scenarios A, B, and C. Increasing the take capacity for Scenario C would allow the existing investment in the Rosedale-Rio Bravo Banking program to be more effectively used, and provide access to the supplies that are already in storage to reduce the supply shortfalls from the initial analysis.


FIGURE 3-14 SCENARIO C INITIAL RELIABILITY: ROSEDALE-RIO BRAVO BANK STORAGE

3.3.2.4 Supplies Selected for Evaluation

The reliability goal for Scenario C can be achieved with the addition of one or more of the programs and supplies discussed in Section 3.3.2.2, or a number of combinations of some of these programs. Based on the assessment of initial supply use just described, storage programs appear to make more sense than additional supplies. Among the storage programs listed, two were selected for evaluation of reliability:

Rosedale-Rio Bravo Banking Program – increased take capacity

Saugus Formation ASR

As noted previously, the Rosedale-Rio Bravo take capacity-increase provides additional dry-year supply from an existing program, while the Saugus Formation ASR program provides additional local storage.

While a number of other programs, or combinations of programs, could have been selected for evaluation, these two programs are a reasonable starting point. At a minimum, evaluation of these two programs provides an indication of the magnitude and timing of additional supplies


needed to achieve the 95 percent reliability goal for Scenario C. Which supplies might ultimately make sense to pursue depend on the eventual need for additional supplies, and a number of factors beyond the scope of this Plan, including program feasibility and costs, and environmental, regulatory, and political considerations.

3.3.3 Reliability with Additional Supplies

To analyze the magnitude and timing of additional supplies needed to achieve 95 percent reliability for Scenario C, the two supply programs selected for evaluation were added to the other supplies included in Scenario C, and included the following assumptions:

Rosedale-Rio Bravo Banking Program – increased take capacity: The take capacity of this existing program was increased from 10,000 AFY to 20,000 AFY. The timing of that increase was determined in the analysis, as was needed to achieve the reliability goal.

Saugus Formation ASR Program: An ASR program with a storage capacity of 30,000 AF, a put capacity of 5,000 AFY, and a take capacity of 10,000 AFY was added. Ninety percent of injected amounts were assumed to be recoverable. This program was modeled like the existing groundwater banking programs, but was assumed to start with a storage of 30,000 AF. The timing for this program was determined in the analysis, as was needed to achieve the reliability goal.

As these storage programs are modeled in the analysis, in the case of a supply shortfall water is first withdrawn from the Saugus Formation ASR, then SWP flexible storage, then Semitropic, and then Rosedale.

3.3.3.1 Scenario C

As discussed previously in Section 3.3.1.1 and shown in Figure 3-4, the 95 percent reliability goal is met in the initial analysis of Scenario C through 2035. However, that goal is just met in 2035, and then begins decreasing. Therefore, the first additional supply program considered here – the increase in Rosedale-Rio Bravo take capacity – is assumed to become available in 2035. With this additional supply, Scenario C reliability increases to 100 percent in 2035 and 2040, and to 96 percent in 2045, with a shortfall has high as 2,100 AF in 2045. With this first supply, the reliability in 2050 increases, but only to 92 percent, so an additional supply program is needed to achieve the reliability goal. In this analysis, the Saugus Formation ASR program is added and is assumed to be available in 2046. With this second additional supply, Scenario C reliability increases to 96 percent in 2050, with a shortfall as high as about 10,100 AF. The results of this analysis are shown in Figure 3-15 for 2020, 2030, 2040, and 2050. A more focused view of the shortfall is shown in Figure 3-16 for the last 20 years of the study period. A comparison of Figures 3-8 and 3-15 and of Figures 3-9 and 3-16 shows the reduction in frequency and magnitude of projected supply shortfall.


FIGURE 3-15 SCENARIO C RELIABILITY WITH ADDITIONAL SUPPLIES


FIGURE 3-16

SCENARIO C RELIABILITY WITH ADDITIONAL SUPPLIES: DETAIL OF SUPPLY SHORTFALL

With the expansion of Rosedale-Rio Bravo take capacity and addition of the Saugus Formation ASR program, the use of CLWA storage changed somewhat from usage in the initial analysis (shown in Figure 3-11). This is shown in Figure 3-17, which shows a comparison of total banking program storage between the initial analysis and the analysis with these supply program additions, for years 2040 and 2050. The results for 2040 show only the effect of the expanded Rosedale take capacity (since the Saugus ASR program is not included until 2046), with the lower dry-year storage reflecting the occasionally larger withdrawals possible with the expanded capacity. The results for 2050 show the higher total storage due to the Saugus ASR program, as well as the lower dry-year storage reflecting larger withdrawals.


FIGURE 3-17 SCENARIO C: TOTAL BANKING PROGAM STORAGE COMPARISON

3.3.3.2 Summary

As noted above, the initial analysis determined that the 95 percent reliability goal was met over the entire study period for the Base Scenario, Scenario A, and Scenario B. With the addition in Scenario C of an increase in Rosedale-Rio Bravo take capacity from 10,000 AFY to 20,000 AFY in 2035, and development of a 30,000 AF capacity Saugus Formation ASR program by 2046, the reliability goal for this Scenario C is also met over the entire study period. A summary of results for each scenario, with these additional supplies included in Scenario C, is presented in Figure 3-18.


FIGURE 3-18

SUMMARY OF RELIABILITY WITH ADDITIONAL SUPPLIES


Section 4: Physical Reliability Considerations

The reliability of the Santa Clarita Valley’s overall water supply is dependent upon the reliability of its groundwater, imported water, and recycled water supplies. Deliveries of these supplies are dependent on an extensive network of SWP and CLWA conveyance facilities; thus, there is a physical reliability constraint to consider in addition to the hydrologic reliability of the supplies.

4.1 Physical Reliability

Physical reliability refers to constraints associated with the water delivery system, including treatment, pumping, and pipeline capacity and structural stability. Imported water supplies may be interrupted or reduced significantly in a number of ways, such as a catastrophic failure in the Sacramento-San Joaquin Bay-Delta system that results in a complete disruption in Delta exports of SWP supplies, an earthquake which damages facilities for water delivery or storage between the Delta and CLWA’s Castaic Lake turnout, subsidence along the California Aqueduct which reduces conveyance capacity, or extended outages required to maintain aging infrastructure.

Reliability may also be impacted by locally-caused impacts to CLWA’s water treatment plants, disruption of the purveyors’ distribution systems, interruptions to wastewater treatment systems and to CLWA’s recycled water system. These types of disruptions could be caused by earthquake, regional power failure, or other factors. The 2015 UWMP details the contingency plans of the purveyors to cope with these sorts of scenarios, and includes staged imposition of demand reduction measures to meet basic health and safety needs during the outage.

4.2 Physical Constraints

4.2.1 Local Infrastructure Constraints

Local infrastructure that CLWA relies upon includes water treatment plants, CLWA’s and purveyors’ distribution systems, wastewater treatment systems and recycled water distribution systems that could be disrupted due to undesirable events. Events that could cause a disruption could include: loss of a facility; loss of control of a facility (offices, pump stations, wells, etc.); loss of supply (power failure, pipeline break, etc.); degradation of water quality; loss of staff (injury or accident, etc.); environmental spill (spill, earthquake, etc.); malevolent event (vandalism, terrorism, etc.); and loss of public confidence.

CLWA has been proactive in identifying and addressing vulnerabilities to local infrastructure from these types of disruptions which are described in the following sections.

4.2.1.1 Identified Vulnerabilities

A 2004 study regarding potential vulnerabilities was performed to provide a systematic evaluation of CLWA’s water systems to determine what issues would make the systems vulnerable to not fulfilling their objectives (i.e., water supply, water quality, etc.), and how these issues could be addressed to ensure the utilities are more likely to meet their objectives.


In the study, objectives and priorities were identified which included water supply (the quantity of water distributed), water quality, financial implications, and critical customers (service priorities at critical locations in the distribution system).

The 2004 study provided a number of recommendations to mitigate or lessen the potential impact of disruption from a vulnerability. Many of the recommendations are confidential in nature and not meant to be publicly reported to protect the security of the infrastructure and operations. However, general recommendations include, but are not limited to: site security; sufficient day/night lighting; advanced SCADA systems; separate chemical storage areas with their own precautions; gates; closed circuit television; signage; doors/windows/locks; and engagement with local law enforcement.

Since the 2004 study CLWA’s distribution system has grown. Consideration of vulnerability now includes this additional infrastructure.

It is noted that CLWA has also undertaken multiple seismic vulnerability assessments dating back to 1989 which evaluated specific portions of CLWA’s utilities and provided recommendations for continued safety and risk evaluation.

CLWA also prepares every two to three years a Facility Capacity Fee Study by which it prioritizes upgrades to existing infrastructure and determines revenue sources to, among other things, address potential vulnerabilities. This study eventually influences the implementation of CLWA’s Capital Improvement Program.

4.2.2 SWP Conveyance Constraints

Most SWP supplies are pumped from the southern Delta into the California Aqueduct. Water pumped from the southern Delta may be temporarily stored in San Luis Reservoir for delivery later in the year, or conveyed further south in the California Aqueduct. The California Aqueduct conveys water along the west side of the San Joaquin Valley to Edmonston Pumping Plant, where water is pumped over the Tehachapi Mountains and the aqueduct then divides into the East and West Branches. Water in the West Branch is conveyed through Pyramid Lake to Castaic Lake, a terminal reservoir of the West Branch from which CLWA takes delivery of its SWP water and other imported supplies.

SWP conveyance structures were sized to deliver full Table A supplies (i.e., 100 percent SWP allocation) to SWP contractors. Conveyance sizing included consideration for peak summer deliveries, either through the inclusion of additional conveyance capacity or, for certain Southern California contractors such as CLWA, additional storage (i.e., “regulatory” storage) in terminal reservoirs. Generally, there is adequate capacity for delivery of CLWA’s supplies, including the additional SWP Table A amount CLWA acquired, as well as its other imported supplies from the Central Valley. With SWP Table A allocations often less than 100 percent, there generally is capacity to transport CLWA’s supplies within its own capacity, or within the unused capacity of other SWP contractors. Further, DWR uses the regulatory storage at Castaic Lake to even out any differences in availability of conveyance capacity and deliveries to CLWA.

SWP facilities from the Delta to Castaic Lake include: 338 miles of canal, pipeline, tunnel, and channel; six pumping plants; two power plants; and numerous canal gate structures.


Construction of most of these facilities was completed by 1973, so these facilities are at or nearing 50 years in age. As this infrastructure continues to age, keeping these facilities maintained and running at full capacity will become more challenging, and costly. Repair or replacement of facilities, which may result in temporary conveyance constraints or complete but temporary outages, are likely to occur more frequently. However, even for unplanned or emergency conveyance constraints or outages, significant interruptions in deliveries to CLWA are not anticipated due primarily to regulatory storage at Castaic Lake.

An issue with potentially greater impact on long-term conveyance capacity is subsidence in the San Joaquin Valley, particularly in areas adjacent to the northern portion of the California Aqueduct. Subsidence in the San Joaquin Valley from groundwater pumping has been observed since the 1920s. A recent report involving NASA satellite technology (Farr et al. 2016) has shown that subsidence continues to occur in areas of the San Joaquin Valley putting both state (i.e., the SWP) and federal water infrastructure at risk. The report shows that subsidence due to groundwater pumping, which accelerated with heavy pumping during the recent drought, has caused the Aqueduct to drop more than two feet in some areas. As a result of the sinking, the Aqueduct in these reaches is showing a reduction in capacity of up to 20 percent (Farr et al. 2016). Actions to restore capacity would include raising canal lining and raising canal gate structures, which would be costly. DWR is assessing the situation and analyzing whether these impacts will affect deliveries to southern California water districts, like CLWA.

The California Aqueduct traverses the Tehachapi Mountains north of CLWA’s service area. Due to the numerous fault lines crossing the mountain range (including the San Andreas and White Wolf faults), water users located south of the mountains are at greater risk of supply disruption due to earthquake than users located north of the mountains. For this and other reasons, the terminal reservoirs located on the West and East Branches of the California Aqueduct include emergency storage.

If an earthquake or other disruption were to occur, pipelines, canals, or pump stations conveying water across the mountains might become inoperable, making SWP deliveries to CLWA and the other downstream contractors dependent on the supplies then available in the terminal reservoirs. This possible situation is a major concern, considering that nearly 50 percent of the Santa Clarita Valley’s current water supply is imported from the SWP. Although pipelines that traverse fault lines are reinforced, damage can still occur depending on the magnitude of the earthquake. Therefore, as identified in previous reliability plan updates, water banking opportunities south of the Tehachapi Mountains have a high value to CLWA.

4.3 Catastrophic Interruption – Potential Outage Scenarios

The Valley is located approximately 20 miles southwest of the San Andreas Fault, which traverses the length of the southern San Joaquin Valley. A major earthquake along this portion of the San Andreas Fault could affect water supplies available to the Santa Clarita Valley. The California Division of Mines and Geology has stated that two of the aqueduct systems that import water to southern California (including the California Aqueduct) could be ruptured by displacement on the San Andreas Fault. The situation could be further complicated by physical damage to pumping equipment and local loss of electrical power.


DWR has an Aqueduct Outage Plan for restoring the California Aqueduct to service should a major break occur, which it estimates could take approximately four months to repair. Limitations on supplies of groundwater and/or imported water for an extended period, due to power outages and/or equipment damage, could result in severe water shortages until the supplies could be restored. Combined water storage of CLWA and the purveyors within the CLWA service area totals approximately 190 MG of water in storage tanks, which can be gravity fed to Valley businesses and residences, even if there is a power outage. The public would be asked to reduce consumption to minimum health and safety levels, extending the supply to a minimum of seven days. This would provide sufficient time to restore a significant amount of groundwater production. After the groundwater supply is restored, the pumping capacity of the four retail purveyors could meet the reduced demand until such time that the imported water supply was reestablished. The Valley’s water sources are generally of good quality, and no insurmountable problems resulting from industrial or agricultural contamination are foreseen. If contamination did result from a toxic spill or similar accident, the contamination would be isolated and should not significantly impact the total water supply. In addition, such an event would be covered by the purveyors’ Emergency Response Plans.

4.3.1 SWP Emergency Outage Scenarios

In addition to earthquakes, the SWP could experience other emergency outage scenarios. Past examples include slippage of aqueduct side panels into the California Aqueduct near Patterson in the mid-1990s, the Arroyo Pasajero flood event in 1995 (which also destroyed part of Interstate 5 near Los Banos) and various subsidence repairs needed along the East Branch of the Aqueduct since the 1980s. All these outages were short-term in nature (on the order of weeks), and DWR’s Operations and Maintenance Division worked diligently to devise methods to keep the Aqueduct in operation while repairs were made. Thus, the SWP contractors experienced no interruption in deliveries.

One of the SWP’s important engineering design features is the ability to isolate parts of the system. The Aqueduct is divided into “pools.” Thus, if one reservoir or portion of the California Aqueduct is damaged in some way, other portions of the system can still remain in operation. The principal SWP facilities are shown on Figure 4-1.


FIGURE 4-1 PRIMARY SWP FACILITIES


Other events could result in significant outages and potential interruption of service. Examples of possible nature-caused events include a levee breach in the Delta near the Harvey O. Banks Pumping Plant, a flood or earthquake event that severely damages the Aqueduct along its San Joaquin Valley traverse, or an earthquake event along either the West or East Branches. Such events could impact some or all SWP contractors south of the Delta.

The response of DWR, CLWA and other SWP contractors to such events would be highly dependent on the type and location of any such events. In typical SWP operations, water flowing through the Delta is diverted at the SWP’s main pumping facility, located in the southern Delta, and is pumped into the California Aqueduct. During the relatively heavier runoff period in the winter and early spring, Delta diversions generally exceed SWP contractor demands and the excess is stored in San Luis Reservoir. Storage in SWP aqueduct terminal reservoirs, such as Pyramid and Castaic Lakes, is also refilled during this period. During the summer and fall, when diversions from the Delta are generally more limited and less than contractor demands, releases from San Luis Reservoir are used to make up the difference in deliveries to contractors. The SWP share of maximum storage capacity at San Luis Reservoir is 1,062,000 AF.

CLWA receives its SWP deliveries through the West Branch of the California Aqueduct at Castaic Lake. The only other contractors receiving deliveries from the West Branch are Metropolitan Water District of Southern California (Metropolitan) and Ventura County Watershed Protection District (formerly known as the Ventura County Flood Control District). The West Branch has two terminal reservoirs, Pyramid Lake and Castaic Lake, which were designed to provide emergency storage and regulatory storage (i.e., storage to help meet peak summer deliveries) for CLWA and the other two West Branch contractors. Maximum operating capacity at Pyramid and Castaic lakes is 171,200 and 323,700 AF, respectively.

In addition to SWP storage south of the Delta in San Luis and the terminal reservoirs, a number of contractors have stored water in groundwater banking programs in the San Joaquin Valley, and many also have surface and groundwater storage within their own service areas.

Three scenarios that could impact the delivery to CLWA of its SWP supply, previously banked supplies or other supplies delivered to it through the California Aqueduct are described below. CLWA’s ability to meet demands during the worst of these scenarios is presented following the scenario descriptions.

4.3.1.1 Scenario 1: Emergency Freshwater Pathway

DWR has estimated that in the event of a major earthquake in or near the Delta, regular water supply deliveries from the SWP could be interrupted for up to three years, posing a substantial risk to the California business economy. Accordingly, a post-event strategy has been developed which would provide necessary water supply protections. The plan has been coordinated through DWR, the Army Corps of Engineers, the United States Bureau of Reclamation, California Office of Emergency Services (Cal OES), Metropolitan, and the State Water Contractors. Full implementation of the plan would enable resumption of at least partial deliveries from the SWP in less than six months.

Assuming that the Banks Pumping Plant would be out of service for six months, DWR could continue making at least some SWP deliveries to all southern California contractors from water stored in San Luis Reservoir. The water available for such deliveries would be dependent on


the storage in San Luis Reservoir at the time the outage occurred and could be minimal if it occurred in the late summer or early fall when San Luis Reservoir storage is typically low. In addition to supplies from San Luis Reservoir, water from the West Branch terminal reservoirs would also be available to the three West Branch contractors, including CLWA. CLWA water stored in groundwater banking programs in the San Joaquin Valley may also be available for withdrawal and delivery to CLWA.

4.3.1.2 Scenario 2: Complete Disruption of the California Aqueduct in the San Joaquin Valley

The 1995 flood event at Arroyo Pasajero demonstrated vulnerabilities of the California Aqueduct (the portion that traverses the San Joaquin Valley from San Luis Reservoir to Edmonston Pumping Plant). Should a similar flood event or an earthquake damage this portion of the aqueduct, deliveries from San Luis Reservoir could be interrupted for a period of time. DWR has informed the SWP contractors that a four-month outage could be expected in such an event.

Arroyo Pasajero is located downstream of San Luis Reservoir and upstream of the primary groundwater banking programs in the San Joaquin Valley. Assuming an outage at a location near Arroyo Pasajero that takes the California Aqueduct out of service for six months, supplies from San Luis Reservoir would not be available to those SWP contractors located downstream of that point. However, CLWA water stored in groundwater banking programs in the San Joaquin Valley could be withdrawn and delivered to CLWA, and water from the West Branch terminal reservoirs would also be available to the three West Branch contractors, including CLWA. Assuming an outage at a location on the California Aqueduct south of the groundwater banking programs in the San Joaquin Valley, these supplies would not be available to CLWA, but water from the West Branch terminal reservoirs would be available to the three West Branch contractors, including CLWA.

4.3.1.3 Scenario 3: Complete Disruption of the West Branch of the California Aqueduct

The West Branch of the California Aqueduct begins at a bifurcation of the Aqueduct south of Edmonston Pumping Plant, which pumps SWP water through and across the Tehachapi Mountains. From the point of bifurcation, the West Branch is an open canal through Quail Lake, a small flow regulation reservoir, to the Peace Valley Pipeline, which conveys water into Pyramid Lake. From Pyramid Lake, water is released into the Angeles Tunnel, through Castaic Powerplant into Elderberry Forebay, and then into Castaic Lake.

If a major earthquake (an event similar to or greater than the 1994 Northridge earthquake) were to damage a portion of the West Branch, deliveries could be interrupted. The exact location of such damage along the West Branch would be key to determining emergency operations by DWR and the three West Branch SWP contractors. A recent report by a joint DWR, Metropolitan, and Los Angeles Department of Water and Power (LADWP) Seismic Resilience Water Supply Task Force estimated that it could take six to twelve months to restore partial deliveries from the West Branch after a major earthquake (DWR, Metropolitan, LADWP, 2017).

For this scenario, it was assumed that the West Branch would suffer a break and deliveries of water from north of the Tehachapi Mountains, including SWP water and CLWA water stored in groundwater banking programs in the San Joaquin Valley, would not be available. While at


least partial deliveries could be available sooner, it was assumed for purposes of this Plan that deliveries through the West Branch would be disrupted for twelve months. However, it was assumed that Pyramid and Castaic dams would not be damaged by the event and that water in Pyramid and Castaic Lakes would be available to the three West Branch SWP contractors, including CLWA.

In any of these three SWP emergency outage scenarios, DWR and the SWP contractors would coordinate operations to minimize supply disruptions. Depending on the particular outage scenario or outage location, some or all of the SWP contractors south of the Delta might be affected. But even among those contractors, potential impacts would differ given each contractor’s specific mix of other supplies and available storage. During past SWP outages, the SWP contractors have worked cooperatively to minimize supply impacts among all contractors. Past examples of such cooperation have included certain SWP contractors agreeing to rely more heavily on alternate supplies, allowing more of the outage-limited SWP supply to be delivered to other contractors, and exchanges among SWP contractors, allowing delivery of one contractor’s SWP or other water to another contractor, with that water being returned after the outage was over.

4.3.1.4 Assessment of Worst-Case Scenario

Of these three SWP outage scenarios, the West Branch outage scenario presents the worst-case scenario for the CLWA service area. In this scenario, CLWA and the purveyors would rely on local supplies and water available to CLWA from Pyramid and Castaic Lakes. An assessment of the supplies available to meet demands in CLWA’s service area during a twelve-month West Branch outage and the additional levels of conservation and/or emergency storage projected to be needed are presented in Table 4-1 for 2020 through 2050.

During an outage, the local supplies available would consist of groundwater from the Alluvial Aquifer and the Saugus Formation, as well as recycled water to the extent available. It was assumed that local well production would be unimpaired by the outage and that the outage would occur during a year when average/normal supplies would be available from the Alluvial Aquifer. Pumping from the Saugus was assumed to be equivalent to the higher pumping planned for a single-dry year. Note that adequate well and aquifer capacity exists to pump at levels higher than those assumed in this assessment, particularly during a temporary period such as an outage. However, to be conservative, groundwater production was assumed to be the planned annual supplies. Furthermore, based on the assumption that additional voluntary and/or mandatory conservation could reduce the amount of waste discharge, and therefore reduce the amount of recycled water produced by the WRPs, the amount of recycled water potentially available for non-potable use is assumed to be at least 25 percent less than during normal conditions.

The water available to CLWA from Pyramid and Castaic Lakes includes flexible storage available to CLWA at Castaic Lake and emergency and potentially regulatory storage available in both Pyramid and Castaic Lakes. Regulatory storage, which is used to help meet high peak summer deliveries, may or may not be available depending on what time of year an outage occurs. For this assessment, regulatory storage was assumed to be unavailable. The amount of emergency storage assumed to be available to CLWA was based on CLWA’s proportionate share of usable storage in each reservoir, where usable storage is maximum operating storage, less regulatory and dead pool storage. At Castaic Lake, this usable storage determination also


excludes the three West Branch contractors’ total Flexible Storage Accounts. CLWA’s proportionate share of usable storage was assumed to be slightly less than three percent, based on its share of capital cost repayment at each reservoir. On this cost repayment basis, the proportionate shares of Metropolitan and Ventura County Watershed Protection District are about 96 percent and one percent, respectively.

As shown in Table 4-1, for a twelve-month emergency outage, demands with plumbing code savings and active conservation would be met through about 2030, with additional conservation and/or emergency storage required past 2030. If a supply shortfall in such an emergency is met entirely with additional conservation (beyond the levels of conservation already planned for), this would require additional demand reductions ranging from two percent in 2035 to nine percent by 2050. As evidenced during the recent drought, these levels of additional conservation may be readily achievable, particularly during an emergency such as this.

Alternatively, if a supply shortfall during such an outage was met entirely with additional emergency storage it would require about 1,800 AF of additional emergency storage by 2035 and 9,600 AF by 2050. The acquisition of emergency storage, as discussed in Section 4.4, could reduce or eliminate the need for additional conservation.

In an emergency outage such as this, there is the potential that cooperation among SWP contractors and/or temporarily increased purveyor groundwater production could increase supplies and reduce any supply shortfalls. However, note that the local supplies included in Table 4-1 are based on the local supplies in this Plan’s Base Scenario and Scenario A. If future increases in local supplies are similar to the reduced amounts assumed in Scenarios B and C, there would be less local supply available to weather an extended outage and an increased need for additional conservation and/or emergency storage.


TABLE 4-1 PROJECTED SUPPLIES AND DEMANDS DURING TWELVE MONTH DISRUPTION OF IMPORTED SUPPLY

(AF)

(a)

2020 2025 2030 2035 2040 2045 2050

Existing Supplies

Existing Groundwater

Alluvial Aquifer(b)

24,100 24,100 24,100 24,100 24,100 24,100 24,100

Saugus Formation(c)

19,865 19,865 19,865 19,865 19,865 19,865 19,865

Recycled Water(d)(e)

338 338 338 338 338 338 338

Planned Supplies

Future Groundwater

Alluvial Aquifer(b)

2,000 4,000 5,000 7,000 7,000 7,000 7,000

Saugus Formation (Restored)(c)

3,775 3,775 3,775 3,775 3,775 3,775 3,775

Saugus Formation (New)(c)

9,560 9,560 9,560 9,560 9,560 9,560 9,560

Recycled Water(d)(e)

424 3,867 5,720 7,203 7,203 7,203 7,203

Total Existing and Planned Supplies 60,061 65,505 68,358 71,841 71,841 71,841 71,841

SWP West Branch Storage Available

Flexible Storage Accounts (f)

6,060 6,060 4,680 4,680 4,680 4,680 4,680

Emergency Storage

Pyramid Lake(g)

4,370 4,370 4,370 4,370 4,370 4,370 4,370

Castaic Lake(h)

3,370 3,370 3,370 3,370 3,370 3,370 3,370

Total West Branch Storage 13,800 13,800 12,420 12,420 12,420 12,420 12,420

Total Supplies and West Branch Storage 73,861 79,305 80,778 84,261 84,261 84,261 84,261

Demands(i)

Demand w/ Plumbing Code Savings 76,700 84,800 92,700 100,000 103,400 106,800 110,400

Demand w/ Plumbing Code Savings and Active Conservation

68,900 74,600 80,800 86,100 88,500 90,900 93,900

Additional Conservation Required(j)

0 0 22 1,840 4,240 6,640 9,640

Additional Conservation as Percent of Demand(k)

0% 0% 0% 2% 4% 6% 9%

Notes: (a) Assumes complete disruption in SWP supplies and in deliveries through the California Aqueduct for 12 months. (b) Pumping from the Alluvial Aquifer is assumed to be the average normal year supplies. (c) Pumping from the Saugus Formation is assumed to the single-dry year supplies. (d) Recycled water supply is based on existing and planned use. (e) Assumes 25% reduction in waste discharge, and therefore in recycled water availability, due to additional voluntary conservation. (f) Includes both CLWA and Ventura County entities flexible storage accounts. Extended term of agreement with the Ventura County entities expires after 2025. (g) CLWA's share of usable storage at Pyramid Lake, based on its 2.817% proportionate share of capital cost repayment of the reservoir, and assumed storage of

155,100 AF.


(h) CLWA's share of usable storage at Castaic Lake, based on its 2.927% proportionate share of capital cost repayment of the reservoir, and assumed usable storage of 115,100 AF.

(i) Demands are assumed to be average/normal year Regional Summary demands from Table 2-5. (j) Additional Conservation Required is the difference between Demand w/ Plumbing Code Savings and Active Conservation and Total Supplies and West Branch

Storage. A portion or all of this could be met with the acquisition of emergency storage (see Section 4.4). (k) Expressed as a percent of Demand w/ Plumbing Code Savings.


4.4 Recommendations for Extended Outage Emergency

Storage

The various outage scenarios highlight the benefit of CLWA having water stored in multiple banking programs south of the Delta. Banking programs located in Kern County, which have access to the California Aqueduct, are ideally suited to meet at least part of CLWA’s emergency needs. The worst-case scenario described above (a complete disruption on the West Branch of the aqueduct during an extended outage) demonstrates the desirability that CLWA also has water stored in at least one water banking program geographically located south of the Tehachapi Mountains.

Alternatives for storage located south of the Tehachapi Mountains could involve an exchange with another West Branch contractor so that the contractor could be served from CLWA’s banked water, and CLWA could be served by a portion of the contractor’s water in Pyramid or Castaic Lake (in addition to CLWA’s existing Flexible Storage Account in Castaic Lake and West Branch emergency storage).

The most likely and utilizable arrangement would be with Metropolitan, which pays for a significant portion of the storage capacity in Castaic Lake. CLWA could store varying amounts of its water in groundwater storage or banking programs within or adjacent to Metropolitan’s service area. In the event of an outage or other emergency, Metropolitan would serve its customers with CLWA’s stored water and CLWA would serve its customers with a like amount of Metropolitan’s water in Castaic Lake.

In addition to exchange arrangements with others, potential projects within the CLWA service area have been explored. CLWA in cooperation with the purveyors prepared the Water Resources Reconnaissance Study (Study) (Carollo, 2015). The Study evaluated a series of supply measures that could provide an additional 10,000 AFY of supply to the service area. The study identified two measures that might be able to go at least part way to that goal: (1) an imported water injection project during wet years to augment Saugus formation groundwater storage, and (2) a groundwater recharge project using recycled water. Both of the projects would be located south of the Tehachapi Mountains, and so would provide an added benefit of supply availability in an emergency. Both projects were evaluated at the conceptual level, but significantly more investigation would need to be completed before either would be implemented.

Potential banking programs, in which CLWA could be served by a portion of the contractor’s water in Pyramid or Castaic Lake for a potential exchange of emergency outage storage, or which could be located within CLWA’s service area include the following:

Willow Springs Water Bank, Antelope Valley: This project is located in eastern Kern County, in the northern portion of the Antelope Valley. It is adjacent to both the East Branch of the California Aqueduct and the Los Angeles Aqueduct. This program is active and is seeking participants.

Antelope Valley-East Kern Water Agency High Desert Water Bank: This is a project proposed by AVEK, a SWP wholesaler located in the Antelope Valley area of southeastern Kern County and northern Los Angeles County. The proposed groundwater banking project would be developed and operated by AVEK, and would be


located adjacent to the East Branch of the California Aqueduct. As proposed, the project would have a total storage capacity of 280,000 AF, with recharge and recovery capacities of 70,000 AFY. AVEK is currently conducting pilot testing, and the environmental analysis for the proposed project is in process. AVEK is actively seeking banking partners.

Palmdale Regional Groundwater Recharge and Recovery Project: PWD, a SWP wholesaler, is implementing a large-scale groundwater recharge and recovery project located adjacent to the East Branch of the California Aqueduct. The project will obtain water for recharge from the SWP and also from recycled water produced by the Los Angeles County Sanitation District Palmdale Water Reclamation Plant. CLWA could be a potential partner in the project by banking excess supply in wet years and recovering that supply in dry years.

Saugus Formation Aquifer Storage and Recovery (ASR) Program: The feasibility of implementing an ASR program in the Saugus Formation has been evaluated through field testing and groundwater modeling simulations. Reconnaissance-level analysis indicates that such a program is feasible. In addition to water reliability benefits, a Saugus ASR program could provide other operational benefits (e.g., higher groundwater levels) and local storage.

Groundwater Replenishment with Recycled Water: The feasibility of using recycled water for a groundwater recharge program in the eastern portion of the Alluvium has been evaluated in the Water Supply Measures Reconnaissance Study and further refined in the draft RWMP. A recycled water recharge project could provide operational benefits (e.g., higher groundwater levels in the Alluvium), increased recycled water usage and greater water recovery from the Alluvium in eastern parts of the groundwater basin. Conceptual design for the project is an extension of the proposed Phase 2A recycled water pipeline, with approximately 5,000 AFY of recycled water from the Valencia WRP discharged to a recharge basin adjacent to the Santa Clara River, and average recovery of 3,500 AFY from downstream Alluvial wells.

4.5 Recommendations for Short-Term Emergency and

Operational Storage

CLWA recently evaluated local short-term emergency and operational storage requirements to sustain deliveries for a seven-day period. In 2013, a hydraulic modeling and system evaluation study was completed to analyze CLWA’s distribution system and determine capital improvement projects necessary to mitigate existing and future system deficiencies and improve system operations. The 2013 report recommended further studies be conducted to evaluate both emergency and operational storage requirements and assist with siting and preliminary design of required storage reservoirs.

In 2017, an emergency and operational storage study was completed based on the 2013 hydraulic system report, and others, with input from the purveyors and local land owners. The goals of the study were to identify emergency storage requirements, identify sites for storage facilities, to develop conceptual facility layouts, and preliminary costs. The primary vulnerabilities that formed the basis of the evaluation included earthquakes (including


liquefaction and landslides) and streambed scour (from Santa Clara River and tributaries and flooding events).

The study identified five emergency storage zones within CLWA’s service area, shown in Figure 4-2.

FIGURE 4-2 EMERGENCY STORAGE AREAS


Within each storage zone an assessment of how much supply would be necessary to sustain a seven-day demand period was calculated; demands were based on the 2015 UWMP and assumed that irrigation and other non-essential water uses would be prohibited (i.e., non-interruptible demand). Demands that could not be met by local groundwater pumping by the purveyors’ would then be served by the identified emergency storage facilities located within each emergency zone. Table 4-2 shows the results of the study, which identifies the current CLWA storage capability within each zone, the additional near term storage needed, and the storage needed by 2050. Overall it shows that CLWA must make investments in storage projects (reservoirs and pump stations) to increase CLWA’s existing storage within the service area of 47 million gallons (MG) by 58.5 MG for a CLWA total of 105.5 MG of storage by 20503. The total cost for the additional facilities (in 2017 dollars) is projected to range from $38 million to $57 million.

TABLE 4-2 EMERGENCY AND OPERATIONAL STORAGE STUDY RESULTS

Storage Zone Existing Storage

(MG)

Additional Near-Term Storage

(MG)

Additional Storage Year

2050 (MG) Total Storage in Year 2050 (MG)

Earl Schmidt Filtration Plant (A)

10 0 2 12

Magic Mountain (B) 0 12.5 13 25.5

Rio Vista Water Treatment Plant (C)

30 0 4 34

Southern Service Area (D)

0 12 3 15

Sand Canyon (E) 7 7 5 19 Total 47 31.5 27 105.5

3 In addition to CLWA’s existing storage of 47 MG, the purveyors also maintain storage in the CLWA service area.

The existing service area storage of CLWA and the purveyors combined totals approximately 190 MG.

Final Report – CLWA Water Supply Reliability Plan Update 2017 5-1

Section 5: Reliability Recommendations

5.1 Summary of Supply Reliability Analysis

Four scenarios were evaluated in this Plan. Each scenario consists of a different projection of available supplies through 2050. These scenarios represent four different views of what the future supply situation might look like. Each supply scenario is evaluated to determine the reliability of that scenario in meeting projected demands in CLWA’s service area. As discussed in Section 3, the four scenarios are described as follows:





The demand and supply assumptions included in each scenario are summarized in Table 3-1. While the reasonableness or likelihood of specific assumptions can be argued, each scenario provides a proxy for differing levels of overall stress on the system. A summary of the results of the supply analysis, which is presented in more detail in Section 3, is shown in Table 5-1.

The variation in results for the four scenarios highlights the range in additional supply actions that may be required to achieve a 95 percent reliability goal. For example, based on the supply reliability analysis, if the future supply situation evolves similar to the Base Scenario or Scenario A, no additional actions are needed during the study period through 2050, beyond the currently planned increases in Alluvial, Saugus, and recycled water supplies described in the 2015 UWMP and in Section 2.

Similarly, for a future that is more like Scenario B, no additional actions beyond those currently planned are needed through at least 2045, and perhaps through 2050. In 2050, the 95 percent reliability goal is just met. An additional dry-year supply of about 5,000 AFY – to replace the dry-year supply from the Semitropic Banking Program that ends in 2045 – would provide a bit of buffer for the last five years of the study period and beyond.

If, however, the future evolves more like Scenario C, additional water management measures would be needed by about 2035. An additional dry-year supply of 10,000 AFY is needed by about 2035, and a second increment of dry-year supply of 10,000 AFY by about 2045.


TABLE 5-1 SUMMARY OF SUPPLY RELIABILITY RESULTS

2020 2025 2030 2035 2040 2045 2050

BASE SCENARIO

Reliability (%) 100% 100% 100% 100% 100% 100% 100%

Supply Shortfall (AF)

- @ 95% Reliability 0 0 0 0 0 0 0

- Maximum 0 0 0 0 0 0 0

SCENARIO A

Reliability (%) 100% 100% 100% 100% 100% 100% 98%


- @ 95% Reliability 0 0 0 0 0 0 0

- Maximum 0 0 0 0 0 0 600

SCENARIO B

Reliability (%) 100% 100% 100% 100% 100% 98% 95%


- @ 95% Reliability 0 0 0 0 0 0 0

- Maximum 0 0 0 0 0 700 9,000

SCENARIO C

Initial

Reliability (%) 96% 100% 96% 95% 92% 90% 86%


- @ 95% Reliability 0 0 0 0 2,300 8,000 14,500

- Maximum 2,300 0 4,000 7,300 9,700 12,100 24,300

w/ Additional Supplies(1)

Reliability (%) 96% 100% 96% 100% 100% 96% 96%


- @ 95% Reliability 0 0 0 0 0 0 0

- Maximum 2,300 0 4,000 0 0 2,100 10,100

Notes: (1) As analyzed, additional supplies included: (a) an increase in take capacity in the existing Rosedale-Rio Bravo

Banking Program from 10,000 AFY to 20,000 AFY in 2035, and (b) a new Saugus Formation ASR program in 2046 with a maximum storage capacity of 30,000 AF, a put capacity of 5,000 AFY, and a take capacity of 10,000 AFY.

For all four scenarios, the supply surplus greatly exceeds any shortfall throughout the study period. This is true even for Scenario C with its assumed supply reductions, as discussed in Section 3.3.2.3 and shown in Figure 3-15. Given this, storage of surplus amounts of existing and planned supplies through expanded use of existing storage programs or new storage programs, rather than acquiring additional base or dry-year supply, appears to be the more effective use of resources.


Dry-year supplies from storage programs could come from an expanded take capacity of the Rosedale-Rio Bravo Banking Program, and/or from new storage program(s). An expanded ability to withdraw storage from the Rosedale-Rio Bravo Banking Program would allow the existing investment in this program to be more effectively used. Any new storage programs could be located in or near the CLWA service area, providing not only water supply but potential benefits related to concerns regarding physical reliability of conveyance facilities.

5.2 Summary of Physical Reliability Considerations

As discussed in Section 4, the reliability of the overall water supply is dependent on the physical reliability of the water delivery system, including SWP facilities used to pump, store, and convey SWP and other imported supplies, and CLWA and purveyor facilities to treat, pump, and distribute supplies. Supply delivery can be interrupted or constrained in a number of ways, such as due to Delta levee failure or other disruption of Delta exports, earthquake-caused facility damage, subsidence-related capacity impacts, or extended or more frequent facility outages required to maintain aging infrastructure.

The assessment in Section 4.3 shows that in the event of a twelve-month outage of SWP facilities, including a complete disruption of the West Branch of the California Aqueduct, service area demands can be met with local supplies (groundwater and recycled water) and West Branch storage (SWP flexible storage in Castaic Lake and emergency storage in Pyramid and Castaic Lakes) through 2030. As shown in Table 4-1, a supply shortfall during a twelve-month outage is projected to reach about 1,800 AF by 2035 and 9,600 AF by 2050.

It is noted, however, that this twelve-month outage assessment assumes that SWP flexible storage is full (4,680 AF) at the beginning of such an outage. As discussed in Section 3.3.2.3, SWP flexible storage is currently operated to provide dry-year supply, is generally the first storage program accessed, and under current operations may be empty. Further, the local supplies used in this assessment are consistent with those assumed in the Base Scenario and Scenario A. If future increases in local supplies are similar to the reduced amounts assumed in Scenarios B and C, there would be less local supply available to weather an extended outage.

To help ensure that SWP flexible storage is indeed available for use in an emergency outage, it is recommended that all or a portion of SWP flexible storage be reserved for emergency use. Reserving all of this storage for emergency use may result in moving up in time by about five years any need for additional dry-year supply. However, this emergency storage would be located close to the service area and easily accessible. It could provide a benefit now, but could prove to be necessary later in the study period to meet demands during an extended outage.

To better quantify emergency storage needs during an extended outage, it is recommended that CLWA undertake a further analysis of such storage. While this Plan includes an assessment based on certain assumptions, it would be advisable to evaluate in more detail what the range of potential needs are, and establish goals and/or criteria to quantify emergency storage needs (e.g., duration of outage to plan for, acceptable level of additional conservation, etc.).

As shown in the supply reliability analysis, additional dry-year supplies may be needed depending on how the supply situation evolves. The potential for SWP facility disruptions is likely to increase as the SWP continues to age. Therefore, an important consideration in any


new programs pursued should be location, with preference given to programs located within the CLWA service area, or at least south of the Tehachapi Mountains.

5.3 Recommendations

As noted above, a range of additional supply actions may be required to achieve a 95 percent reliability goal, depending on how the future supply situation evolves. As in any planning analysis, a number of assumptions have been made regarding projected demands and the availability of various supplies. The future may very well evolve somewhat differently than assumed, but will hopefully lie somewhere within the bounds of the scenarios analyzed. However, conditions should continue to be monitored, and water supply reliability should be reassessed as changing conditions, such as updated SWP reliability analyses that incorporate differing climate change assumptions or different Delta regulatory constraints, warrant.

Based on the water supply reliability analysis and a 95 percent reliability goal, and on physical reliability considerations, the following recommendations are made:

Near Term (through 2035)

Supply Reliability

Supplies: No additional supply actions are needed, beyond the 2015 UWMP planned increases in local supplies.

Physical Reliability

Emergency storage for extended outage:

o Reserve use of SWP flexible storage for emergency storage (rather than for dry-year supply).

o Pursue a further of analysis of emergency storage to establish criteria for and better quantify near and long-term storage needs.

Longer Term (2035 through 2050)

Supply reliability

If future evolves like Base Scenario or Scenario A (i.e., local supply increases as planned, and SWP supplies like existing or with California WaterFix): No additional supply actions are needed.

If future evolves like Scenario B (i.e., local supply increases less than planned, and moderate reduction in SWP supplies): May need additional dry-year supply by 2046 to replace Semitropic Banking Program (ends in 2045). (If reserving SWP flexible storage for emergency use, this additional dry-year supply becomes a need rather than a “may” need).


If future evolves like Scenario C (i.e., even smaller local supply increases, and larger reduction in SWP supplies): Need additional dry-year supply of 10,000 AFY by 2035, and another 10,000 AFY increment of dry-year supply by 2046. (If reserving SWP flexible storage for emergency use, the first increment of dry-year supply is needed by 2030.)

Type of additional dry-year supply: Look first to dry-year supply from expanded use of existing storage programs or from new storage programs (rather than acquiring additional base or dry-year supply).

Physical reliability

Location of new dry-year supply program(s): For any new storage programs pursued, look first to programs located within CLWA’s service area, or at least south of the Tehachapi Mountains.

Emergency storage for extended outage: Reserve use of SWP flexible storage for emergency storage (rather than for dry-year supply). Consider up-sizing any new local or near-local storage programs to include storage reserved for emergency storage.

Final Report – CLWA Water Supply Reliability Plan Update 2017 Reference - i

References

Carollo Engineers, June 2015. Castaic Lake Water Agency Water Resources Reconnaissance Study.

CLWA et al., 2010. Santa Clarita Valley 2010 Urban Water Management Plan.

CLWA et al., 2015. Santa Clarita Valley 2015 Urban Water Management Plan.

CH2M Hill. 2004. Analysis of Perchlorate Containment in Groundwater Near the Whittaker-Bermite Property, Santa Clarita, California.

CH2M Hill. 2004a. Regional Groundwater Flow Model for the Santa Clarita Valley, Model Development and Calibration, Santa Clarita, California. April.

Castaic Lake Water Agency. 2003. Water Supply Reliability Plan Update, prepared by Kennedy/Jenks Consultants.

Castaic Lake Water Agency. 2003a. Groundwater Management Plan - Santa Clara River Valley Groundwater Basin, East Subbasin, Los Angeles County, California. Castaic Lake Water Agency. 2009. Water Supply Reliability Plan Update, prepared by Kennedy/Jenks Consultants.

Castaic Lake Water Agency. 2011. Water Supply Reliability Plan Update, prepared by Kennedy/Jenks Consultants.

DWR 2016. Conveyance -Regional/Local, A Resource Management Strategy of the California Water Plan. July 29, 2016 available at http://www.water.ca.gov/waterplan/docs/rms/2016/05_Conveyance_Regional-Local_July2016.pdf

Farr et al. 2016. Progress Report: Subsidence in California, March 2015 - September 2016.

Available at: http://www.water.ca.gov/waterconditions/docs/2017/JPL%20subsidence%20report%20final%20for%20public%20dec%202016.pdf

DWR, MWD, LADWP. 2017. Seismic Resilience Water Supply Task Force; Presentation to the OME Committee Meeting. September 2017.

DWR. The State Water Project Delivery Reliability Report. 2015. State of California. Department of Water Resources.

DWR. The State Water Project Delivery Reliability Report. 2009. State of California. Department of Water Resources.

http://www.water.ca.gov/waterplan/docs/rms/2016/05_Conveyance_Regional-Local_July2016.pdf

http://www.water.ca.gov/waterplan/docs/rms/2016/05_Conveyance_Regional-Local_July2016.pdf

http://www.water.ca.gov/waterconditions/docs/2017/JPL%20subsidence%20report%20final%20for%20public%20dec%202016.pdf

http://www.water.ca.gov/waterconditions/docs/2017/JPL%20subsidence%20report%20final%20for%20public%20dec%202016.pdf

Final Report – CLWA Water Supply Reliability Plan Update 2017 Reference - ii

DWR. 2002b. Santa Clara River Valley Groundwater Basin, Santa Clara River Valley East Subbasin. California’s Groundwater Bulletin 118. Last Update: January 2006.

GSI Water Solutions. 2017. Potential Climate Change Scenario for Alluvial Aquifer Pumping, Draft Technical Memorandum. September.

Kennedy/Jenks Consultants. 2014. Upper Santa Clara River Integrated Regional Water Management Plan. February.

Kennedy/Jenks Consultants. 2016a. Recycled Water Master Plan Update.

Layne Water Development and Storage, LLC. March 21, 2003. Proposal of Water Banking in New Unit of the Semitropic Groundwater Bank for Castaic Lake Water Agency. Presented to Kennedy/Jenks Consultants.

Luhdorff & Scalmanini and GSI Water Solutions. August 2009. Analysis of Groundwater Supplies and Groundwater Basin Yield, Upper Santa Clara River Groundwater Basin, East Subbasin

Maddaus Water Management (MWM), Inc. 2015. SCV Family of Water Supplies Water Use Efficiency Strategic Plan. June.

Santa Clarita Valley Municipal Water Purveyors, June 2009. Analysis of Groundwater Supplies and Groundwater Basin Yield. Upper Santa Clara River Groundwater Basin, East Basin.

Appendix A

CLWA Water Operations Model Description

1

APPENDIX A

CLWA Water Operations Model

General Methodology

An analytic spreadsheet model developed for CLWA by MBK Engineers was used in this analysis

to update CLWA’s Reliability Plan. The model performs annual water operations for the CLWA

service area over a specified study period, using demands as they are projected to increase over

the study period and, to reflect the uncertainty in the hydrology over the study period, using

supplies that would be available under multiple hydrologic sequences. For each hydrologic

sequence, the model steps through each year of the study period, comparing annual supplies to

demands and operating CLWA storage programs as needed, adding to storage in years when

supplies exceed demand and withdrawing from storage when demand exceeds supplies. Results

from the multiple hydrologic sequences are then compiled and summarized to provide a statistical

assessment of the reliability of CLWA’s supplies and storage programs to meet its projected

demands over the study period.

Hydrologic Variability

Of the many factors affecting this reliability assessment, the factor with the greatest degree of

variability and with the largest impact on supplies (and to a lesser degree, demands) is hydrology.

Hydrology in northern California significantly affects the availability of SWP supplies; local

hydrology affects the availability of Alluvial groundwater supplies (as well as demands); and dry-

year reductions in SWP supplies affect the need for additional Saugus groundwater pumping.

The SWP supply data used in this analysis is based on the results of SWP modeling studies

conducted by DWR using CalSim, a computer model that simulates monthly operations of the SWP

and CVP systems. Among other model inputs, CalSim uses hydrologic inflows to the model based

on 82 years of historical monthly inflows from 1922 through 2003, adjusted to reflect current levels

of development in the supply source areas. All of the CalSim studies used in this analysis also

reflect changes to hydrology expected to result from climate change, specifically, a 2025 emission

level and a 15 cm sea level rise.

CalSim studies are essentially a ‘snapshot-in-time’ type of analysis. That type of study uses a fixed

set of facilities, operating requirements/constraints, and water demands, operated over a number

of years using historical hydrology. The resulting supply deliveries from a CalSim study provide an

indication of the potential supply reliability of the SWP system, as that system is assumed to exist

and be operated at a given point in time. However, for this Reliability Plan analysis, what is

desired is potential supplies over a study period – (i.e., the 34-year period from 2017 through 2050

– with conditions such as demands, supplies, and storage programs changing over the study

period.

2

To reflect the potential variability in hydrology over the study period, for this analysis a number of

hydrologic sequences are used, based on the same historical hydrologic period used in the CalSim

studies. Based upon the 82 years of hydrologic record used in CalSim, a series of 82 hydrologic

“traces” is used. Each trace consists of 34 years of sequential hydrology, with the beginning year

of each trace lagging the beginning year of the previous trace by one year. For example, the first

trace begins with 1922 hydrology assumed for year 2017, 1923 hydrology for 2018, etc., through

1955 hydrology for 2050. The hydrology is shifted by one year for the second trace, beginning with

1923 hydrology for 2017, 1924 hydrology for 2018, etc., through 1956 hydrology for 2050. This

one-year shift continues until the end of the hydrologic period (2003) is reached, where the data

begins “wrapping” back to 1922 hydrology. The end result of this process is 82 traces of

hydrology.

Each hydrologic trace is used to analyze CLWA supply and demand performance over the study

period – in other words, if that sequence of hydrology were to occur again, how adequate would

the supplies associated with that hydrology and the storage programs in place be in meeting

demands over the study period? Study period results from each of the 82 hydrologic traces are

then compiled and summarized, and are used to provide a statistical assessment of the reliability

of CLWA’s supplies and storage programs to meet its projected demands over the study period.

CLWA Water Operations

Demand and Supplies

As mentioned above, the CLWA model performs annual water operations for the CLWA service

area over a specified study period, using demands as they are projected to increase over the study

period and using supplies that would be available under the multiple hydrologic traces described

above. For each hydrologic trace analyzed, the model steps through each year of the study

period, comparing annual supplies to demands. Input to the model allows demands and supplies

to change during the study period, so specific input data for these parameters is entered for each

year during the study period.

The annual supplies included in the model to meet demands in the CLWA service area are:

groundwater (both Alluvial and Saugus), recycled water, SWP water, Buena Vista-Rosedale water,

and Nickel water. The availability of some of these supplies is projected to increase over the study

period (i.e., recycled water and municipal groundwater use), while other supplies are either

constant each year (Buena Vista-Rosedale water and Nickel water) or are assumed to be

independent of year during the study period (i.e., SWP water). Data input to the model is for

normal-year conditions over the study period.

In addition to changes over time, some supplies are also affected by hydrology (i.e., groundwater

and SWP water). Hydrologic effects are incorporated into the model through use of the 82

hydrologic traces described above. In the case of groundwater, for example, when a dry year

occurs in the local watershed in a particular hydrologic trace, Alluvial pumping is assumed to

decrease from normal-year pumping amounts. In contrast, Saugus pumping does not necessarily

3

increase at the same time, because its pumping is tied to hydrology in northern California and the

availability of SWP supplies. SWP supplies are taken directly from CalSim model results for each

year in the hydrologic trace.

Similarly, demands in the CLWA service area are assumed to increase over the study period, and

projected normal-year demands are input to the model. Demands are also affected by local

weather, with lower or higher than normal demands occurring when local conditions are either wet

or dry, respectively. As with supplies, the hydrologic effects on demands are incorporated into the

model through use of the 82 hydrologic traces. When a dry year occurs in a particular hydrologic

trace, demand is increased from normal-year amounts, and in a wet year is reduced.

The demand and supply parameters included in the CLWA model and whether they are assumed

to change over time or be affected by hydrology are summarized in Table A-1.

Storage Programs

As mentioned previously, the annual water operations included in CLWA’s model also include

operation of its storage programs. For each hydrologic trace analyzed, the model steps through

each year of the study period, comparing annual supplies to demands and operating CLWA

storage programs as needed over the study period, adding to storage in years when supplies

exceed demand and withdrawing from that storage when demand exceeds supplies. The model

keeps track throughout the study period of the amount of water stored within each program,

beginning with a starting storage amount, and then adding to and subtracting from storage as it

operates the programs over the study period. Input to the CLWA model includes storage and

capacity data for each storage program, including: beginning (2017) storage, total storage

capacity, capacity for annual additions to storage (“put” capacity), and capacity of annual

withdrawals (“take” capacity). The capacities are entered for each year during the study period,

and so can easily reflect planned changes to programs, such as a planned increase in take

capacity, or a program that begins or ends at some point during the study period.

The storage programs included in the CLWA model include: SWP flexible storage, SWP carryover

in San Luis Reservoir, Rosedale-Rio Bravo Banking Program, Semitropic Banking Program, and

Semitropic – Newhall Land Banking Program. Exchanges, which are essentially a form of storage

program, include: Rosedale-Rio Bravo Exchange and West Kern Exchange. In addition to these

programs, the model also includes dry year supplies available for purchase under the Yuba

Accord. In addition to these existing programs, the model includes placeholders for new banking

programs and for new exchanges.

The priorities for use of these programs in any year when there is an surplus or shortfall in supplies

is identified in Table A-2. In a year when total annual supplies exceed demand, the model adds

the surplus supply to these storage programs, within the capacity constraints identified in model

input. The model starts with the first program listed in Table X-2 under Supply Surplus, and adds

the surplus (up to that program’s put capacity), to storage in that program (up to the program’s total

storage capacity). Any remaining surplus supply is added to the second program, and so on, until

4

all the supply is stored or there are no more programs in which to store it. Conversely, in a year

when total annual supplies are less than demand, the model withdraws the shortfall from available

storage programs. The model starts with the first program listed in Table A-2 under Supply

Shortfall, withdraws the shortfall (up to that program’s take capacity), from any available storage in

that program. Any remaining shortfall is withdrawn from the second program, and so on, until the

shortfall is eliminated or there are no more programs to draw from. Any remaining annual supply

surplus or shortfall is tracked in the model and totaled over the study period, and those totals are

then used to assess system performance and reliability.

Assumptions Used in this Reliability Plan

For this Reliability Plan update, the study period analyzed is 2017 through 2050 (the year of

development buildout in the service area assumed in the 2015 UWMP). The analysis starts with a

Base Scenario and evaluates three additional scenarios, described generally as follows:





See Table A-3 for more detail on specific assumptions included in each scenario.

Approach Used in this Reliability Plan versus in Previous Updates

The approach used in this Reliability Plan differs from previous updates to CLWA’s Reliability Plan.

Previously, a Monte Carlo analysis was used, where a regression analysis was performed on SWP

delivery data from a CalSim model run, and the statistical relationship was used to generate 1,000

delivery forecasts. While the use of this many delivery forecasts allows more potential futures to

be analyzed, the results are only as good as the statistical relationship upon which the forecasts

are based, and the ability of that statistical relationship to accurately reflect the actual occurrence

of wet and dry periods and, given SWP storage, the potential lag in the effect of those periods on

resulting SWP deliveries.

5

The approach used in this Reliability Plan update retains the exact same wet and dry periods that

occurred during the 82-year period of hydrologic record, with the effect of those periods on SWP

deliveries taken directly from CalSim model runs. It is not reliant on how well a regression analysis

reflects hydrologic wet or dry periods and their effects on SWP deliveries. In this Reliability Plan

update, four different scenarios are analyzed, each of which is based on a different CalSim model

run. Under the previous approach, this would have required a separate regression analysis for

each scenario.

Since the first CLWA Reliability Plan was prepared in 2003, the length of the hydrologic record

used in CalSim has increased from 73 years to 82 years of hydrologic record. Under the approach

used in this Reliability Plan update, the longer the hydrologic record used in CalSim, the more

sequences of hydrology can be developed and used for analysis of CLWA system operations. The

use of the 82 hydrologic sequences developed is considered to be adequate to assess system

performance and reliability for the purposes of this Reliability Plan update.

Further, the CLWA model actually operates CLWA’s storage programs over the study period. This

allows an assessment not only of whether there is adequate take capacity to meet demands in

supply-limited years, but whether there is adequate supply and put capacity in years of excess to

store those supplies for eventual dry-year withdrawals.

6

Table A-1 CLWA Water Operations Model: Variability in Demand and Supplies

Parameter

STUDY PERIOD VARIATIONS HYDROLOGIC VARIATIONS

Change over Study

Period? Reason for Change

Variation due to

Hydrology? Reason for Variation

DEMANDS

Demands Yes Increases due to population growth

Yes Higher outdoor use in locally dry years, and lower use in wet years

SUPPLIES

Alluvial pumping Yes Increases due to conversion of agricultural pumping to M&I use

Yes Reduced availability in locally dry years

Saugus pumping Yes Increased capacity due to restored, replacement, and planned wells

Yes Increased usage in years that are dry in northern California

Recycled water Yes Increases resulting from planned distribution system and use

No

SWP Table A No Yes

Northern California hydrology effects on supply availability and Delta requirements

Buena Vista-Rosedale

No No

Nickel water – Newhall Land

No No

7

Table A-2 CLWA Water Operations Model: Storage Program Use Priorities

SUPPLY SURPLUS SUPPLY SHORTFALL

Priorities for Additions to Storage In year when Supplies exceed Demand

Priorities for Withdrawals from Storage In year when Supplies less than Demand

1. SWP flexible storage

2. SWP carryover in San Luis Reservoir

3. Rosedale-Rio Bravo Banking Program

4. Semitropic Banking Program

5. Semitropic – Newhall Land Banking Program

6. New banking program(s)

7. New exchange(s)

1. Yuba Accord (dry-year water purchase)

2. SWP carryover in San Luis Reservoir

3. SWP flexible storage

4. Rosedale-Rio Bravo Exchange

5. West Kern Exchange

6. New exchange(s)

7. Semitropic Banking Program surcharge(1)

8. Semitropic Banking Program

9. Rosedale-Rio Bravo Banking Program

10. Semitropic – Newhall Land Banking Program

11. New banking program(s)

Note:

(1) Semitropic Banking Program surcharge is the remaining balance of water CLWA stored in 2002 and 2004 under a temporary storage agreement with Semitropic. In 2015, CLWA entered into a long-term banking program with Semitropic (labeled here as “Semitropic Banking Program”), with specified storage, put, and take capacities. The balance of the previously stored water was transferred into the Semitropic Banking Program, and is in addition to the water that may be stored under that new program (thus the label here as “surcharge”). This water is still available for withdrawal by CLWA but uses Semitropic Banking Program withdrawal capacity. Further, there can be no additions to the amount “surcharged” in the Semitropic Banking Program.

8

Table A-3 CLWA Water Operations Model: Reliability Plan Scenario Assumptions

BASE SCENARIO

(~2015 UWMP) SCENARIO A SCENARIO B SCENARIO C

Study Period 2017 - 2050 same as Base same as Base same as Base

HYDROLOGY

Hydrologic period included

1922 - 2003 same as Base same as Base same as Base

Climate change

SWP hydrology: Includes effects of 2025 emission level and 15 cm sea level rise

Local hydrology: None

same as Base same as Base

SWP hydrology: Same as base

Local hydrology: More extreme droughts and high-rainfall years

DEMANDS

Demand w/ plumbing code savings

Increases from 73,640 AFY in 2017 to 110,400 AFY by 2050 [UWMP Table 2-28]

(1)

Normal demands decreased by 10% in wet years, and increased by 10% in dry years

(2)

same as Base same as Base same as Base

Demand w/ active conservation

Increases from 69,020 AFY in 2017 to 93,900 AFY by 2050 [UWMP Table 2-28]

(1)

Normal demands decreased by 10% in wet years, and increased by 10% in dry years

(2)


9

BASE SCENARIO


SUPPLIES

Groundwater

Alluvium

Normal year municipal pumping increases from 24,100 AFY in 2017 to 31,100 AFY by 2035, based on existing wells and planned conversion of agricultural pumping [UWMP Table 3-10]

Compared with normal-year pumping, total aquifer pumping decreases by 2,100 AFY in a single dry year and by 3,750 AFY in multiple dry years, per the basin yield analysis

(3)

same as Base same as Base

same as Base, except:

(4)

Compared with normal-year pumping, total aquifer pumping decreases by 6,500 AFY by a fourth dry year and by 10,500 AFY by a seventh dry year

Year types reclassified to reflect wetter conditions needed to return to normal-year pumping

Saugus

Normal year municipal pumping increases in dry years, per the basin yield analysis, with reduction of 1,800 AFY to account for pumping by others

(5)

Max dry year municipal pumping: o 2017: 19,865 AFY

(existing wells max) o 2018-19: 23,640 AFY

(existing and restored wells max)

o 2020-50: 33,200 AFY (existing, restored, and replacement/planned wells max)

[UWMP Table 3-11]

same as Base


Max pumping: o 2017:

19,865 AFY (existing wells max)

o 2018-50: 23,640 AFY (existing and restored wells max)


Max pumping o 2017-50:

10,685 AFY (existing and restored wells normal year pumping)

[UWMP Table 3-10]

Recycled Water

Recycled water

Increases from 676 AFY in 2017to max of 10,054 AFY by 2035 [UWMP Table 4-3]

(6)

same as Base


Increase to max of 7,315 AFY by 2030

(7)


Increase to max of 6,585 AFY by 2030

(8)

10

BASE SCENARIO


Imported Supply

SWP Table A

From CalSim run ELT with: o existing SWP facilities o current regulatory and

operational constraints

Deliveries to CLWA average 58,300 AFY, ranging from 7,600 AFY to 95,200 AFY, depending on hydrologic year

[2015 DCR Appendix C](9)

From CalSim run Alt4A H3+ with: o proposed

California WaterFix facilities

o revised regulatory and operational constraints

Deliveries to CLWA average 60,300 AFY and range from 18,600 AFY to 95,200 AFY, depending on hydrologic year

[BDCP/Cal WaterFix Final EIR/EIS Alternative 4A]

(10)

From CalSim run ECLO with: o existing

SWP facilities

o additional South Delta operational constraints


[2015 DCR Appendix E]

(11)

From CalSim run ECHO with: o existing

SWP facilities

o additional South Delta operational constraints and Delta outflow requirements


[2015 DCR Appendix D]

(12)

SWP carryover none none none none

SWP flexible storage

Max capacity:

2017-25: 6,060 AF

2026-50: 4,684 AF [UWMP p. 3-7]

same as Base

same as Base

same as Base

Buena Vista - Rosedale

11,000 AFY every year [UWMP p. 3-14]


Nickel water 1,607 AFY every year

[UWMP p. 3-15]

Available 2022-50(13)


Yuba Accord

1,000 AFY available for purchase during dry periods

Available 2017-25 [UWMP p. 3-15]

none none none

11

BASE SCENARIO


Banking/Exchange Programs

Semitropic Bank surcharge

Max capacities: o Storage: 35,970 AF o Put: 0 AFY o Take: 5,000 AFY

(14)

Available through 2045 [UWMP pp. 3-47 to 3-48]


Semitropic Bank

Max capacities: o Storage: 15,000 AF o Put: 5,000 AFY o Take: 5,000 AFY

(14)

Available through 2045 [UWMP pp. 3-47 to 3-48]


Semitropic – Newhall Land Bank

Max capacities:

Storage: 55,000 AF

Put: 4,950 AFY

Take: 4,950 AFY [UWMP p. 3-49]

none none none

Rosedale Bank

Max capacities:

Storage: 100 TAF

Put: 20 TAFY

Take: o 2017: 3,000 AFY

(15)

o 2018-29: 10,000 AFY o 2030-50: 20,000 AFY

[UWMP pp. 3-48 to 3-49]


Take capacity: o 2017:

3,000 AFY

(15)

o 2018-50: 10,000 AFY

same as Scenario A

same as Scenario A

New Bank

Max capacities: o Storage: unspecified o Put: unspecified o Take: 5,000 AFY

Available beginning 2046 [UWMP p. 3-49]

none(16)

none(16) none

(16)

Rosedale Exchange

Max capacities: o Storage: 9,441 AF o Put: 0 AFY o Take: 9,441 AFY

Available through 2021 [UWMP p. 3-46]


West Kern Exchange

Max capacities: o Storage: 500 AF o Put: 0 AFY o Take: 500 AFY

Available through 2021 [UWMP p. 3-46]


12

BASE SCENARIO


Notes:

(1) Normal demands for 2020 through 2050 from UWMP Table 2-28. Demands for 2017 are based on 2015 demands from SCV Demand Study Update, Final Technical Memorandum #2 (Maddaus Water Management, March 2016), interpolated to 2017.

(2) “Wet” and “dry” years for demand impact determination are based on local precipitation for water years from 1922 through 2003, with the wettest 25% of those years labeled as “wet,” and the driest 25% labeled as “dry.”

(3) Total Alluvial pumping is assumed to be reduced from normal-year levels by 2,100 AFY in a first dry year, and by an additional 1,650 AFY (total reduction of 3,750 AFY) beginning in a second consecutive dry year. Based on “Total Alluvial Pumping” values reported in Table 3-4 of Analysis of Groundwater Supplies and Groundwater Basin Yield, Luhdorff & Scalmanini and GSI Water Solutions, August 2009 (2009 Basin Yield Analysis).

(4) Alluvial pumping in Scenario C includes potential effects of climate change, including increased pumping reductions from normal-year levels, and consideration of wetter conditions needed to return to normal-year pumping. Based on Potential Climate Change Scenario for Alluvial Aquifer Pumping, Technical Memorandum (GSI Water Solutions, September 2017).

(5) Saugus Formation pumping is assumed to be 10,685 AFY in normal years, increasing to17,325 AFY in a first dry year for the SWP, to 23,427 AFY in a second consecutive SWP dry year, and 33,177 AFY beginning in a third consecutive SWP dry year. Based on results from the 2009 Basin Yield Analysis Table 3-8, with those results reduced by 1,800 AFY to account for private pumping and projected Whittaker-Bermite pumping for perchlorate treatment.

(6) Recycled water supply for 2017 based on interpolation between actual recycled water use of 450 AF in 2015 and projected supply of 1,015 AFY in 2020 from UWMP Table 4-3.

(7) Recycled water supply for Scenario B is assumed to be 7,315 AFY. Includes demand for recycled water based on CLWA’s current contract with the Santa Clarita Valley Sanitation District, and projected demand for Newhall Ranch West Side Communities from Updated Water Demand Projections for West Side Communities, Technical Memorandum (GSI Water Solutions, March 2016).

(8) Recycled water supply for Scenario C is assumed to be 6,585 AFY. Includes existing demand for recycled water plus projected demand for Phase 2D and Vista Canyon, as well as projected demand for Newhall Ranch West Side Communities from Updated Water Demand Projections for West Side Communities, Technical Memorandum (GSI Water Solutions, March 2016).

(9) SWP deliveries for the Base Case are taken from a CalSim modeling run – the Early Long-Term (ELT) Scenario – included in Appendix C of the 2015 SWP Delivery Capability Report, DWR, July 2015 (2015 DCR). ELT

Scenario assumptions include: existing SWP facilities, current regulatory and operational constraints, 82 years of historical hydrology adjusted to reflect changes expected to result from climate change (based on 2025 emissions and 15 cm sea level rise), and contractor demands for SWP supplies at maximum Table A Amounts.

(10) SWP deliveries for Scenario A are taken from a CalSim modeling run for the Preferred Alternative – Alternative 4A (Alt4A H3+) – from the Bay Delta Conservation Plan/California WaterFix Final EIR/EIS, DWR and USBR, December 2016 (CA WaterFix Final EIR/EIS). Alt4A H3+ assumptions are similar to those for the Base Case but include: 9,000 cfs dual conveyance Delta facility, and revised operational constraints.

(11) SWP deliveries for Scenario B are taken from a CalSim modeling run – the Existing Conveyance Low Outflow (ECLO) Scenario – included in Appendix E of the 2015 DCR. ECLO Scenario assumptions are similar to those for the Base Case but include additional South Delta operational constraints.

(12) SWP deliveries for Scenario C are taken from a CalSim modeling run – the Existing Conveyance High Outflow (ECHO) Scenario – included in Appendix D of the 2015 DCR. ECHO Scenario assumptions are similar to those for Scenario B but include additional Delta outflow requirements for fall X2 and to enhance spring outflows.

(13) The availability of Nickel Water as an annual supply beginning in 2022 is based on the assumption that Newhall Ranch is developed and this supply transferred to VWC or CLWA by 2022.

(14) Banking programs labeled here as “Semitropic Bank surcharge” and “Semitropic Bank” share the same 5,000 AFY take capacity, so withdrawals from both programs combined cannot exceed 5,000 AF in a given year.

(15) The timing of the increase in Rosedale Bank take capacity from the existing 3,000 AFY to a planned 10,000 AFY is assumed here to be 2018, rather than 2017 as assumed in the UWMP.

(16) The capacity and timing of any new banking program(s) is not included in the initial assessment of the reliability of Scenarios A, B and C, but is evaluated as part of the Reliability Plan analysis of what is needed to achieve CLWA’s 95% reliability target for those scenarios.

Appendix B

Climate Change Groundwater Assessment Memorandum

Technical Memorandum

To: Lauren Everett – Kennedy/Jenks Consultants Jeff Ford – Kennedy/Jenks Consultants

From: John Porcello – GSI Water Solutions Jeff Barry – GSI Water Solutions

Date: September 20, 2017

Re: Potential Climate Change Scenario for Alluvial Aquifer Pumping (Santa Clarita Valley, Los Angeles County, California)

Introduction This technical memorandum presents a scenario for Alluvial Aquifer groundwater pumping that

might arise as a result of future changes in local climate and local hydrology. Compared with the

historical observed climate, climate change has the potential to alter the groundwater operating

plan for the local groundwater basin in two respects:

1. Changing the frequency and duration of droughts and high-rainfall events. Specific

changes could include longer and/or more frequent periods of sustained drought, shorter

time periods between the end of one drought and the beginning of the next drought, and

reduced groundwater recharge during years of normal and above-normal rainfall.

2. Changing the achievable pumping volume from certain wells during a future

drought. Prior studies and operating experience during the recent 2012-2015 drought

together indicate that Alluvial Aquifer wells at the eastern end of the valley are not

always able to meet target drought-year production volumes, particularly once a drought

has persisted for multiple years. This condition could be exacerbated if future droughts

are longer or are characterized by even lower rates of natural groundwater recharge

than has been observed during past droughts.

Each topic is addressed below.

Drought Frequency and Duration Projections of future rainfall for the Santa Clarita Valley have been studied in the past by the

local water purveyors, using publically-available downscaled precipitation data sets derived from

global climate models that simulate a variety of future scenarios for greenhouse gas emissions.

Potential Climate-Change Scenario for Alluvial Aquifer Pumping (Santa Clarita Valley, Los Angeles, County, California) September 20, 2017

2 | P A G E GSI WATER SOLUTIONS, INC.

The analysis of these local-scale precipitation forecasts was presented in a Basin Yield Analysis

report prepared by Luhdorff & Scalmanini Consulting Engineers and GSI Water Solutions

(LSCE and GSI, 2009). That study examined 112 published climate projections, and focused its

attention on nine rainfall projections that were identified to best replicate historical rainfall in the

Santa Clarita Valley, as recorded at the Newhall-Soledad rain gage, which is located in Newhall

and has daily rainfall records dating back to 1931.

For each of the nine models, the short-term and long-term rainfall trends that are projected

through the late 21st century were identified by calculating the cumulative departure of annual

rainfall after 2010, compared with the 1931-2007 long-term average rainfall. Figure 1 displays

the cumulative departure after 2010 for each of the nine projections. The nine projections exhibit

a broad range in cumulative departure over time, with increasing divergence in the cumulative

departure values after the year 2050, which is beyond the study period for CLWA’s Reliability

Plan. In comparing the 2010 through 2050 projections with historical conditions, four of the nine

models show prevailing wetter conditions (as indicated by generally increasing cumulative

departure values with time), while the other five models show fluctuations between prevailing

wetter and prevailing drier conditions (generally decreasing cumulative departure values) during

this near-term 40-year period. After 2050, five of the nine models project prevailing wetter

conditions, three models project prevailing drier conditions, and one model predicts conditions

similar to the historical long-term average rainfall.

Based on consideration of these nine rainfall projections and a review of the historical pattern of

normal/dry/wet years dating back to 1922, CLWA and GSI have constructed a scenario with

more extreme dry periods to use in the technical assessments and modeling work being

conducted for the Reliability Plan. Table 1 shows the historical normal/dry/wet year sequence

for the 82-year historical period of 1922 through 2003 (labeled as “Current Conditions” for the

Reliability Plan modeling work) and the revisions to that sequence (shown in the far right column

of Table 1) that represent one reasonable scenario for the potential effects of climate change on

drought duration. In each case, the year type for local pumping plan lags the year type for local

hydrologic conditions by one year, to reflect the fact that pumping during a given year is

governed both by (1) the rainfall during that same year and (2) the antecedent conditions during

the prior year.

The primary role of climate-change in the year-type sequence is to increase the amount of

rainfall that is required to end a period of dry-year pumping. Under current conditions, rainfall

values similar to the historical annual average (such as the 18.02-inch rainfall of 1986) can end

a drought, whereas under the climate-change scenario wetter conditions are required to end

dry-year pumping because of the longer, and therefore more extreme nature, of the drought

compared with historical conditions. Specifically, the climate-change scenario assumes that

pumping from the Alluvial Aquifer eventually (1) increases incrementally in any year when the

annual precipitation during the prior year is between about 23 and 35 inches, and (2) returns to

the normal-year production rate once this increased precipitation has occurred for 2 or more

consecutive years or there has been a single year of even greater precipitation (exceeding 35

inches). As shown by the statistics at the bottom of Table 1, over the 82-year simulation period,

the climate-change scenario increases the number of dry years from 53 to 69 years, for a



drought frequency of 65 percent under historical conditions and 84 percent under the climate-

change scenario. The effects of the climate-change scenario on pumping from the Alluvial

Aquifer are (1) deeper reductions in pumping arising from longer droughts and (2) more gradual

ramp-ups in pumping with fewer normal pumping years between droughts. These drought-year

pumping volumes are discussed below.

Alluvial Aquifer Drought-Year Pumping Volumes Southern California and the Santa Clarita Valley experienced four years of significantly below-

normal rainfall during calendar years 2012 through 2015. The rainfall volume during this 4-year

period was approximately 32 inches, which is a 40-inch deficit compared with the volume of

about 72 inches that would have occurred under four consecutive years of normal rainfall. As

shown in Figure 2, the slope of the rainfall cumulative departure curve during this period was

steeper than during prior observed droughts, indicating the substantial intensity (larger rainfall

deficit) of this drought. For purposes of the Reliability Plan, the 2012 through 2015 drought is

assumed to be indicative of pumping amounts during future droughts of similar duration.

During the last year of the drought (2015), the three retail municipal purveyors1 pumped

approximately 6,500 acre-feet per year (AFY) less from the Alluvial Aquifer than they had

pumped during the two years of normal rainfall conditions that preceded the drought; see Figure

3. This decrease was approximately 3,000 AFY greater than the 3,600 AFY dry-year decrease

in municipal purveyor pumping described in the groundwater operating plan for the Alluvial

Aquifer (LSCE and GSI, 2009; Kennedy/Jenks Consultants and others, 2015). The 6,500 AFY

decrease in municipal purveyor pumping in 2015 (compared with non-drought years) occurred

despite one municipal purveyor (Valencia Water Company [VWC]) pumping certain of its wells

at higher volumes than planned during 2014 and 2015, in order to provide make-up water

supplies to offset the unachievable pumping volumes that year from other wells at the east end

of the valley. VWC’s extra pumping amounted to approximately 6,300 AFY in 2014 and 1,000

AFY in 2015.

These recent operations can be used as a basis/surrogate for estimating the achievable Alluvial

Aquifer pumping volume under climate-change-driven droughts of similar intensity and either

similar or longer durations than the 2012-2015 drought. The dry-year pumping reductions

assumed for future droughts in this climate change scenario for the Reliability Plan modeling

assessments are presented in Tables 2 and 3 and are as follows:

1. Future Droughts of Similar Duration as Recent Conditions. This scenario assumes

that the 2015 pumping volumes by each retailer are achievable in the fourth year of a

future drought, including the 1,000 AFY of extra pumping by VWC. Accordingly, dry-year

production from the Alluvial Aquifer in year four of a drought (32,100 AFY) is 6,500 AFY

less than normal-year production (38,600 AFY), rather than the 3,600 AFY decrease in

municipal purveyor pumping described in the groundwater operating plan.

1 Newhall County Water District (NCWD), Santa Clarita Water Division (SCWD) of CLWA, and Valencia Water Company (VWC).



2. Extended Droughts Lasting Longer Than Recent Conditions. This scenario also

assumes that by the seventh year of more extended future droughts (a) VWC will not

pump beyond its planned dry-year production numbers, and (b) other wells at the east

end of the basin will be able to pump only half of the amounts they were pumping at the

end of the 2012-2015 drought. Under this scenario, dry-year production from the Alluvial

Aquifer in year seven or higher of a drought (28,100 AFY) is 10,500 AFY less than

normal-year pumping (38,600 AFY), rather than the 3,600 AFY drought-year decrease in

municipal purveyor pumping described in the groundwater operating plan. This is based

on the following:

a. VWC’s actual dry-year pumping is equal to its planned dry-year amounts (i.e.,

without the 1,000 AFY of extra pumping). In other words, the climate change

scenario assumes that VWC’s production is unchanged compared with the

drought-year conditions described in the groundwater operating plan.

b. The actual combined annual pumping volume by Newhall County Water District

(NCWD) and the Santa Clarita Water Division of CLWA (SCWD) decreased from

about 13,400 AFY in 2011 (the year before the recent drought began) to 5,603

AFY in 2014 and 5,728 AFY in 2015. These actual 2014 and 2015 pumping

volumes were approximately 7,700 to 7,800 AFY less than the actual combined

production by NCWD and SCWD during the non-drought year of 2011. For a

climate-change scenario, an assumed 50 percent reduction in the actual 2014-

2015 production volumes for these two municipal purveyors would result in

approximately 2,800 AFY of pumping by these two purveyors. The Reliability

Plan assumes that the 2,800 AFY combined production capacity for NCWD and

SCWD would occur by year seven of a drought under a climate change scenario.

This NCWD-SCWD combined production rate of 2,800 AFY is 10,500 AFY less

than the 13,400 AFY actual pumping that occurred in the non-drought year of

2011.

c. These additional pumping reductions, totaling 3,800 AFY, added to the 6,500

AFY pumping reductions by year four, result in a total decrease in pumping by

the seventh year of an extended drought of approximately 10,500 AFY (with

rounding) compared with normal years.

Summary of Climate-Change Scenario The climate-change scenario developed for the evaluation of the Alluvial Aquifer in the

Reliability Plan study is summarized in Table 4 and is characterized by (1) a time period where

84 percent of the years have rainfall below the historical annual average of inches, (2) droughts

are longer in duration (lasting up to 23 years in one case), (3) years of above-normal rainfall are

less common, and (4) Alluvial Aquifer groundwater production is reduced because of these

factors. This climate-change scenario estimates that groundwater production from the Alluvial

Aquifer during a prolonged drought period could decline to 28,100 AFY by year 7 of a sustained

drought, though a single year of average or modestly wet conditions could prolong the duration

of time required for the annual groundwater production volume to decline to this amount. In the



case of a multi-year drought, annual groundwater production from the Alluvial Aquifer eventually

(1) increases incrementally in any year when the annual precipitation during the prior year is

between about 23 and 35 inches, and (2) returns to the normal-year production rate once this

increased precipitation has occurred for 2 or more consecutive years or there has been a single

year of even greater precipitation (exceeding 35 inches).

References Kennedy/Jenks Consultants, Nancy Clemm, Luhdorff & Scalmanini Consulting Engineers, and Stacy Miller Public Affairs. 2016. Final 2015 Urban Water Management Plan for Santa Clarita Valley. Prepared for Castaic Lake Water Agency (CLWA), CLWA Santa Clarita Water Division, Newhall County Water District, Valencia Water Company, and Los Angeles County Waterworks District No. 36. June 2016.

LSCE and GSI. 2009. Analysis of Groundwater Supplies and Groundwater Basin Yield, Upper Santa Clara River Groundwater Basin, East Subbasin. Prepared for the Santa Clarita Valley Municipal Water Purveyors by Luhdorff and Scalmanini Consulting Engineers (LSCE) and GSI Water Solutions (GSI). August 2009.

TABLES

AlluvialPumping Tables 2017-09-20.xlsx, Sheet “Table 1” 1 of 1 Prepared by GSI Water Solutions, Inc.

Table 1

Pumping Year Types for

Historical/Current Conditions and the Climate Change Scenario

Potential Climate-Change Scenario for Alluvial Aquifer Pumping

Santa Clarita Valley, Los Angeles County, California

Calendar Year

Local

Precipitation(a)

(inches)

Pumping Year

Type(b)(c)

(Historical/Current

Conditions)

Pumping Year

Type(b)(d)(e)

(Climate-Change

Scenario)

1922 32 normal normal

1923 14 normal normal

1924 8 dry year 1 dry year 1



1927 24 normal dry year 2

1928 10 normal dry year 1



1931 24.41 dry year 3 dry year 3

1932 13.73 normal dry year 2










1942 7.10 normal normal






























































Number of dry years 53 69

Percent of years that are dry 65% 84%

Notes:

(a) From records at Newhall-Soledad rain gage (Station No. FC32CE). Records from 1922-

1930 are estimated from a Richard Slade and Associates source.

(b) Pumping year type lags local rainfall by one year.

(c) Under historical/current conditions, dry-year pumping occurs when rainfall in prior year

is 12.5 inches or less, and may continue until after a year with high rainfall (well above

normal) has occurred.

(e) For the climate-change scenario, the dry year "number" is not always sequential;

pumping rates scale up and down gradually according to year-to-year variations in rainfall.

(d) Under the climate-change scenario, dry-year pumping ends when rainfall is 35 inches or

higher, there are two consecutive years of above-normal rainfall, or the drought is only one

year long.


Table 2

Alluvial Aquifer Production in Normal and Dry Years



Pumping

Year Type

Total Alluvial

Pumping

(TAF)(b)(c)

Pumping

Reduction from

Previous Year

Type

(TAF)

Cumulative

Pumping

Reduction

(TAF)

Pumping

Year Type

Total Alluvial

Pumping

(TAF)(a)(b)

Pumping

Reduction from

Previous Year

Type

(TAF)

Cumulative

Pumping

Reduction

(TAF)

Climate-Change

Reduction in

Alluvial Pumping

(TAF)

normal 38.60 normal 38.60 0

dry year 1 36.50 -2.10 -2.10 dry year 1 36.50 -2.10 -2.10 0

dry year 2 34.85 -1.65 -3.75 dry year 2 34.85 -1.65 -3.75 0

dry year 3 34.85 0.00 -3.75 dry year 3 33.40 -1.45 -5.20 -1.45

dry year 4 34.85 0.00 -3.75 dry year 4 32.10 -1.30 -6.50 -2.75

dry year 5 34.85 0.00 -3.75 dry year 5 30.45 -1.65 -8.15 -4.40

dry year 6 34.85 0.00 -3.75 dry year 6 29.15 -1.30 -9.45 -5.70

dry year 7 34.85 0.00 -3.75 dry year 7 28.10 -1.05 -10.50 -6.75

dry year 8 34.85 0.00 -3.75 dry year 8 28.10 0.00 -10.50 -6.75

dry year 9 34.85 0.00 -3.75 dry year 9 28.10 0.00 -10.50 -6.75

dry year 10 34.85 0.00 -3.75 dry year 10 28.10 0.00 -10.50 -6.75

dry year 11 34.85 0.00 -3.75 dry year 11 28.10 0.00 -10.50 -6.75

dry year 12 34.85 0.00 -3.75 dry year 12 28.10 0.00 -10.50 -6.75

Notes: Notes:

(a) Total pumping = M&I, ag, and private pumping.

Under Current Conditions(a) With Potential Climate-Change Impacts

(b) Total pumping = M&I, ag, and private pumping. (b) TAF = thousands of acre-feet

(c) TAF = thousands of acre-feet

(a) Source: Table 3-4 of Basin Yield Analysis report (LSCE and GSI, 2009).


Table 3

Year Types and Production Volumes for the Alluvial Aquifer

Under Historical/Current Conditions and the Climate Change Scenario



Calendar Year

Local

Precipitation(a)

(inches)

Pumping Year

Type(b)(c)

(Historical/Current

Conditions)

Pumping Year

Type(b)(d)(e)

(Climate-Change

Scenario)

Total Alluvial

Production

(Historical/Current

Conditions)

(TAF)(f)

Total Alluvial

Production

(Climate-Change

Scenario)

(TAF)(f)

Reduced Alluvial

Production Arising

from the Climate-

Change Scenario

(TAF)(f)

1922 32 normal normal 38.60 38.60 0.00

1923 14 normal normal 38.60 38.60 0.00

1924 8 dry year 1 dry year 1 36.50 36.50 0.00

1925 7 dry year 2 dry year 2 34.85 34.85 0.00

1926 26 dry year 3 dry year 3 34.85 33.40 -1.45

1927 24 normal dry year 2 38.60 34.85 -3.75

1928 10 normal dry year 1 38.60 36.50 -2.10

1929 12 dry year 1 dry year 1 36.50 36.50 0.00

1930 12 dry year 2 dry year 2 34.85 34.85 0.00

1931 24.41 dry year 3 dry year 3 34.85 33.40 -1.45

1932 13.73 normal dry year 2 38.60 34.85 -3.75

1933 20.52 dry year 1 dry year 3 36.50 33.40 -3.10

1934 18.05 dry year 2 dry year 4 34.85 32.10 -2.75

1935 12.21 dry year 3 dry year 5 34.85 30.45 -4.40

1936 20.47 dry year 4 dry year 6 34.85 29.15 -5.70

1937 17.92 dry year 5 dry year 7 34.85 28.10 -6.75

1938 32.75 dry year 6 dry year 8 34.85 28.10 -6.75

1939 11.27 normal dry year 1 38.60 36.50 -2.10

1940 21.37 dry year 1 dry year 2 36.50 34.85 -1.65

1941 42.14 dry year 2 dry year 3 34.85 33.40 -1.45

1942 7.10 normal normal 38.60 38.60 0.00

1943 37.03 dry year 1 dry year 1 36.50 36.50 0.00

1944 24.63 normal normal 38.60 38.60 0.00

1945 14.56 normal normal 38.60 38.60 0.00

1946 21.71 normal dry year 1 38.60 36.50 -2.10

1947 4.16 normal normal 38.60 38.60 0.00

1948 9.13 dry year 1 dry year 1 36.50 36.50 0.00

1949 9.93 dry year 2 dry year 2 34.85 34.85 0.00

1950 6.84 dry year 3 dry year 3 34.85 33.40 -1.45

1951 12.42 dry year 4 dry year 4 34.85 32.10 -2.75

1952 34.19 dry year 5 dry year 5 34.85 30.45 -4.40

1953 4.88 normal dry year 1 38.60 36.50 -2.10

1954 15.82 dry year 1 dry year 2 36.50 34.85 -1.65

1955 13.91 dry year 2 dry year 3 34.85 33.40 -1.45

1956 14.21 dry year 3 dry year 4 34.85 32.10 -2.75

1957 22.85 dry year 4 dry year 5 34.85 30.45 -4.40

1958 23.14 dry year 5 dry year 6 34.85 29.15 -5.70

1959 9.81 normal dry year 5 38.60 30.45 -8.15

1960 11.64 dry year 1 dry year 6 36.50 29.15 -7.35

1961 8.82 dry year 2 dry year 7 34.85 28.10 -6.75

1962 21.22 dry year 3 dry year 8 34.85 28.10 -6.75

1963 12.79 dry year 4 dry year 9 34.85 28.10 -6.75

1964 10.09 dry year 5 dry year 10 34.85 28.10 -6.75

1965 32.28 dry year 6 dry year 11 34.85 28.10 -6.75

1966 14.57 normal dry year 1 38.60 36.50 -2.10

1967 23.23 dry year 1 dry year 2 36.50 34.85 -1.65

1968 6.90 dry year 2 dry year 3 34.85 33.40 -1.45

1969 32.42 dry year 3 dry year 4 34.85 32.10 -2.75

1970 23.19 normal dry year 1 38.60 36.50 -2.10

1971 13.75 normal normal 38.60 38.60 0.00

1972 4.15 dry year 1 dry year 1 36.50 36.50 0.00

1973 19.79 dry year 2 dry year 2 34.85 34.85 0.00

1974 18.04 dry year 3 dry year 3 34.85 33.40 -1.45

1975 10.92 dry year 4 dry year 4 34.85 32.10 -2.75

1976 14.02 dry year 5 dry year 5 34.85 30.45 -4.40

1977 20.87 dry year 6 dry year 6 34.85 29.15 -5.70

1978 42.17 dry year 7 dry year 7 34.85 28.10 -6.75

1979 21.47 normal normal 38.60 38.60 0.00

1980 27.00 normal normal 38.60 38.60 0.00

1981 13.42 normal normal 38.60 38.60 0.00

1982 20.20 dry year 1 dry year 1 36.50 36.50 0.00

1983 39.07 normal dry year 2 38.60 34.85 -3.75

1984 12.86 normal normal 38.60 38.60 0.00

1985 8.37 dry year 1 dry year 1 36.50 36.50 0.00

1986 18.02 dry year 2 dry year 2 34.85 34.85 0.00

1987 14.45 normal dry year 3 38.60 33.40 -5.20

1988 16.92 dry year 1 dry year 4 36.50 32.10 -4.40

1989 7.56 dry year 2 dry year 5 34.85 30.45 -4.40

1990 6.98 dry year 3 dry year 6 34.85 29.15 -5.70

1991 17.21 dry year 4 dry year 7 34.85 28.10 -6.75

1992 32.03 dry year 5 dry year 8 34.85 28.10 -6.75

1993 32.72 normal dry year 1 38.60 36.50 -2.10

1994 10.27 normal normal 38.60 38.60 0.00

1995 29.15 dry year 1 dry year 1 36.50 36.50 0.00

1996 15.88 normal normal 38.60 38.60 0.00

1997 13.35 normal dry year 1 38.60 36.50 -2.10

1998 30.73 normal dry year 2 38.60 34.85 -3.75

1999 8.96 normal dry year 1 38.60 36.50 -2.10

2000 14.04 normal dry year 2 38.60 34.85 -3.75

2001 22.24 dry year 1 dry year 3 36.50 33.40 -3.10

2002 7.90 dry year 2 dry year 4 34.85 32.10 -2.75

2003 15.70 dry year 3 dry year 5 34.85 30.45 -4.40

Number of dry years 53 69 36.48 33.83 -2.65

Percent of years that are dry 65% 84% Average Average Average

Notes:

(f) TAF = thousands of acre-feet

(a) From records at Newhall-Soledad rain gage (Station No. FC32CE). Records from 1922-

1930 are estimated from a Richard Slade and Associates source.

(b) Pumping year type lags local rainfall by one year.

(c) Under historical/current conditions, dry-year pumping occurs when rainfall in prior year

is 12.5 inches or less, and may continue until after a year with high rainfall (well above

normal) has occurred.

(d) Under the climate-change scenario, dry-year pumping ends when rainfall is 35 inches or

higher, there are two consecutive years of above-normal rainfall, or the drought is only one

year long.

(e) For the climate-change scenario, the dry year "number" is not always sequential;

pumping rates scale up and down gradually according to year-to-year variations in rainfall.


Table 4

Year Types and Production Volumes for the Alluvial Aquifer

Under the Climate Change Scenario



Calendar Year

Drought Year

Number

Pumping Year

Type

Total Alluvial

Production

(TAF)

Reduced Alluvial

Production Arising from

the Climate-Change

Scenario

(TAF)

1922 normal normal 38.60 0.00


1924 dry year 1 dry year 1 36.50 0.00

1925 dry year 2 dry year 2 34.85 0.00

1926 dry year 3 dry year 3 33.40 -1.45

1927 dry year 4 dry year 2 34.85 -3.75

1928 dry year 5 dry year 1 36.50 -2.10

1929 dry year 6 dry year 1 36.50 0.00

1930 dry year 7 dry year 2 34.85 0.00

1931 dry year 8 dry year 3 33.40 -1.45

1932 dry year 9 dry year 2 34.85 -3.75

1933 dry year 10 dry year 3 33.40 -3.10

1934 dry year 11 dry year 4 32.10 -2.75

1935 dry year 12 dry year 5 30.45 -4.40

1936 dry year 13 dry year 6 29.15 -5.70

1937 dry year 14 dry year 7 28.10 -6.75

1938 dry year 15 dry year 8 28.10 -6.75

1939 dry year 16 dry year 1 36.50 -2.10

1940 dry year 17 dry year 2 34.85 -1.65

1941 dry year 18 dry year 3 33.40 -1.45


1943 dry year 1 dry year 1 36.50 0.00



1946 dry year 1 dry year 1 36.50 -2.10


1948 dry year 1 dry year 1 36.50 0.00

1949 dry year 2 dry year 2 34.85 0.00

1950 dry year 3 dry year 3 33.40 -1.45

1951 dry year 4 dry year 4 32.10 -2.75

1952 dry year 5 dry year 5 30.45 -4.40

1953 dry year 6 dry year 1 36.50 -2.10

1954 dry year 7 dry year 2 34.85 -1.65

1955 dry year 8 dry year 3 33.40 -1.45

1956 dry year 9 dry year 4 32.10 -2.75

1957 dry year 10 dry year 5 30.45 -4.40

1958 dry year 11 dry year 6 29.15 -5.70

1959 dry year 12 dry year 5 30.45 -8.15

1960 dry year 13 dry year 6 29.15 -7.35

1961 dry year 14 dry year 7 28.10 -6.75

1962 dry year 15 dry year 8 28.10 -6.75

1963 dry year 16 dry year 9 28.10 -6.75

1964 dry year 17 dry year 10 28.10 -6.75

1965 dry year 18 dry year 11 28.10 -6.75

1966 dry year 19 dry year 1 36.50 -2.10

1967 dry year 20 dry year 2 34.85 -1.65

1968 dry year 21 dry year 3 33.40 -1.45

1969 dry year 22 dry year 4 32.10 -2.75

1970 dry year 23 dry year 1 36.50 -2.10


1972 dry year 1 dry year 1 36.50 0.00

1973 dry year 2 dry year 2 34.85 0.00

1974 dry year 3 dry year 3 33.40 -1.45

1975 dry year 4 dry year 4 32.10 -2.75

1976 dry year 5 dry year 5 30.45 -4.40

1977 dry year 6 dry year 6 29.15 -5.70

1978 dry year 7 dry year 7 28.10 -6.75




1982 dry year 1 dry year 1 36.50 0.00

1983 dry year 2 dry year 2 34.85 -3.75


1985 dry year 1 dry year 1 36.50 0.00

1986 dry year 2 dry year 2 34.85 0.00

1987 dry year 3 dry year 3 33.40 -5.20

1988 dry year 4 dry year 4 32.10 -4.40

1989 dry year 5 dry year 5 30.45 -4.40

1990 dry year 6 dry year 6 29.15 -5.70

1991 dry year 7 dry year 7 28.10 -6.75

1992 dry year 8 dry year 8 28.10 -6.75

1993 dry year 9 dry year 1 36.50 -2.10


1995 dry year 1 dry year 1 36.50 0.00


1997 dry year 1 dry year 1 36.50 -2.10

1998 dry year 2 dry year 2 34.85 -3.75

1999 dry year 3 dry year 1 36.50 -2.10

2000 dry year 4 dry year 2 34.85 -3.75

2001 dry year 5 dry year 3 33.40 -3.10

2002 dry year 6 dry year 4 32.10 -2.75

2003 dry year 7 dry year 5 30.45 -4.40

Number of dry years 69 69 33.83 -2.65

Percent of years that are dry 84% 84% Average Average

FIGURES

Figure1_NineClimateChangeProjections.xlsx Prepared by GSI Water Solutions, Inc.

Figure 1 Cumulative Departure from Average Annual Rainfall from Nine Climate-Change Projections, 2010 through 2098

Figure2_HistoricalRainfallCumDeparture.xlsx Prepared by GSI Water Solutions, Inc.

Figure3_AlluvialPumping-2010thru2015.xlsx Prepared by GSI Water Solutions, Inc.

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