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DRAFT 2025 Water Shortage Contingency Plan
Adopted June 22, 2026
Contents Overview ....................................................................................................................................................... 2 Section 1 – Analysis of Supply Reliability and Seismic Risk Assessment....................................................... 5 1.1 Supply Reliability Scenario Planning............................................................................................ 5 1. 2 Catastrophic Interruption ............................................................................................................ 6 1.3 Seismic Risk Assessment and Mitigation Plan ............................................................................. 8 1.4 Multiple Dry Year Analysis and Drought Risk Assessment ........................................................ 11 Section 2 – Annual Water Supply and Demand Assessment Procedures................................................... 14 2.1 Water Supply and Demand Assessment Requirements............................................................ 14 2.2 Annual Water Supply and Demand Assessment Procedures .................................................... 15 Section 3 – Six Standard Shortage Stages ................................................................................................... 25 3.1 Imported Water Shortage ......................................................................................................... 26 3.2 Emergency Supplies................................................................................................................... 27 3.3 Stages of Action by Level ........................................................................................................... 29 Section 4 – Additional Shortage Response Actions .................................................................................... 33 4.1 Standard IRWD Practices for Shortage Response ..................................................................... 33 4.2 Voluntary Reduction Measures ................................................................................................. 34 4.3 Use of Budget-Based Rates ....................................................................................................... 35 4.4 End-Use Prohibitions ................................................................................................................. 38 4.5 Critical Shortage Measures........................................................................................................ 38 4.6 Operational Drought Control Measures.................................................................................... 39 Section 5 – Communication Protocols ........................................................................................................ 40 Section 6 – Compliance and Enforcement .................................................................................................. 42 Section 7 – Legal Authorities ...................................................................................................................... 43 Section 8 – Financial Consequences ........................................................................................................... 44 8.1 Cost of Compliance.................................................................................................................... 45 Section 9 – Monitoring and Reporting........................................................................................................ 46 Section 10 – WSCP Refinement Procedures ............................................................................................... 47 Exhibit A – Draft Water Shortage Contingency Resolution ........................................................................ 49 Exhibit B – EPA Emergency Response Plan (ERP) Certification Receipt and Confirmation ........................ 51 Exhibit C – Orange County Water and Wastewater Multi-Jurisdictional Hazard Mitigation Plan.............. 52
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IRWD – 2025 Water Shortage Contingency Plan
Overview
The California Water Code (CWC) Section 10632 requires that every urban water supplier shall prepare and adopt a Water Shortage Contingency Plan (WSCP) as part of its Urban Water Management Plan (UWMP). The first Irvine Ranch Water District (IRWD) WSCP was adopted in 1987 to provide guidance on implementing actions to reduce water demands in the event of a water shortage. Since then, IRWD’s WSCP has been revised several times. The last significant revision to the WSCP occurred in 2021. Following the 2012-2016 drought in California, IRWD prepared and adopted an updated WSCP in May 2018. The 2018 WSCP incorporated the lessons learned during the 2012-2016 California drought, as well as new elements from the state’s long-term framework document, Making Water Conservation a California Way of Life, Implementing Executive Order B-37-16 , which was released in April 2017. IRWD’s 2018 WSCP provided procedures for responding to various levels of supply shortages including voluntary measures, non-rate response measures, and potential rate response measures for each level of shortage. The 2021 update to the WSCP incorporated new legislated requirements including supply reliability processes, annual water supply and demand assessment procedures, a seismic hazard assessment, and additional prescriptive elements. The 2025 WSCP incorporates all of the previous requirements and is updated with information from the most recent reports, data, and analyses. IRWD maintains the flexibility to amend the WSCP periodically and independently of the UWMP. WSCP Requirements & Sections This 2025 WSCP addresses and incorporates the required elements set forth by CWC Section 10632, including the following requirements:
• Key attributes of the urban water supplier’s water supply reliability analysis conducted pursuant to Water Code Section 10635. [Section 10632(a)(1)]
• Six standard water shortage levels corresponding to progressive ranges of up to 10, 20, 30, 40, and 50 percent shortages and greater than 50 percent shortage. [Section 10632(a)(3)(A)] • Locally appropriate “shortage response actions” for each shortage level, with a corresponding estimate of the extent the action will address the gap between supplies and demands. [Section 10632(a)(4)] • Procedures for conducting and approving an annual water supply and demand assessment with prescribed elements that is required by CWC Section 10632.1. [Section 10632(a)(2)]
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IRWD – 2025 Water Shortage Contingency Plan
• Monitoring and reporting requirements and procedures to ensure+ appropriate data is collected to monitor customer compliance and to respond to any state reporting requirements. [Section 10632(a)(9)] • A reevaluation and improvement process to assess the functionality of the urban water supplier’s WSCP and to make appropriate adjustments as may be warranted. [Section 10632(a)(10)] • A seismic risk assessment and mitigation plan to assess the vulnerability of each of the various facilities of a supplier’s water system and to mitigate those vulnerabilities. [Section 10632.5(a)]
This WSCP is organized into the following sections: Section 1 – Analysis of Supply Reliability and Seismic Risk Assessment Section 2 – Annual Water Supply and Demand Assessment Procedures Section 3 – Six Standard Shortage Stages Section 4 – Additional Shortage Response Actions Section 5 – Communication Protocols Section 6 – Compliance and Enforcement Section 7 – Legal Authorities
Section 8 – Financial Consequences Section 9 – Monitoring and Reporting Section 10 – WSCP Refinement Procedures Past Implementation of WSCP
On January 17, 2014, Governor Brown proclaimed a Drought State of Emergency, which called on Californians to voluntarily reduce water consumption by 20%. In September 2014, IRWD’s Board of Directors (Board) responded to the drought and the Governor’s Emergency Proclamation by declaring a Level 1 Shortage Warning. In response to worsening statewide drought conditions, on April 1, 2015, the Governor issued an Executive Order that mandated a 25% statewide reduction in urban potable water use compared to 2013 water use levels. For IRWD, the State Water Resources Control Board (SWRCB) mandated a water use reduction target of 16% compared to 2013 levels. In July 2015, IRWD’s Board declared a Level 2 Shortage Condition aimed at reducing demands by 10-25% in response to the SWRCB’s mandate. In April of 2017, Governor Brown lifted the drought emergency declaration while retaining a commitment to advance conservation and drought planning and response measures throughout the state. Response measures and other lessons learned from the drought and declaration of a Level 2 Shortage Condition in 2015 were incorporated into IRWD’s 2018 and 2020 WSCPs.
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IRWD – 2025 Water Shortage Contingency Plan
On July 8, 2021, in response to a worsening statewide drought, Governor Newsom issued Executive Order N-10-21 and called upon Californians to voluntarily reduce water use by 15% compared with 2020 in order to preserve available water supplies and reserves. Although IRWD was not experiencing a shortage, on September 27, 2021, IRWD’s Board declared a Level 2 Shortage, to assist in meeting the Governor’s call for a 15% reduction. IRWD successfully implemented all the basic measures identified in Level 1 and additional Level 2 response actions including expanded outreach and targeted conservation programs. Following a very wet winter and significant snowpack accumulation, on March 2023, Governor Newsom issued Executive Order N-5-23 easing the drought restrictions. On April 10, 2023, IRWD’s Board rescinded the Level 2 Shortage. Permanent restrictions to prohibit water waste remain in effect.
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IRWD – 2025 Water Shortage Contingency Plan
Section 1 – Analysis of Supply Reliability and Seismic Risk Assessment
IRWD’s approach to manage risk and to maintain a resilient water supply relies on diversifying water supplies, establishing groundwater banking programs, and maintaining a robust planning process that anticipates and prepares for a variety of risks such as extended drought, climate change, and infrastructure disruptions at both the regional and local level. In 2016, IRWD prepared a Water Supply Reliability Evaluation (Evaluation) which provided an understanding of how projected conditions, such as imported water supply shortages, climate change, and facility outages could impact water supply. The 2016 Evaluation included an analysis of IRWD’s ability to maintain a minimum level of service under reasonably foreseeable hydrologic and system outage conditions and emergency scenarios, or combination of such scenarios, based on a rigorous and transparent probability analysis. In 2025, IRWD prepared a Water Supply Reliability Study Update (2025 Study), a comprehensive update to the 2016 Evaluation. The 2025 Study evaluated IRWD’s ability to reliably manage supply shortages and enhance system resilience in response to emergencies and evolving water supply conditions over a 38-year planning horizon from 2022-2059. The 2025 Study incorporated updated potable water demand forecasts, revised supply assumptions, and a detailed analysis of system performance. 1.1 Supply Reliability Scenario Planning The 2025 Study assessed IRWD’s ability to mitigate supply shortages and enhance system resilience in response to emergency disruptions and local and regional water supply conditions. The impact on IRWD’s potable water supply was evaluated using the Integrated Resources Planning Distribution System Model (IRPDSM), which applies a probabilistic Monte Carlo modeling approach, over a 38-year planning horizon (2022–2059). The following planning disruption scenarios were simulated: • Delta Levee Failure. The Delta is located where the Sacramento and San Joaquin Rivers converge. Water must flow through the Delta’s complex network of levees and islands to convey water from Northern California to Southern California. It supplies water to over 25 million Californians and millions of acres of farmland throughout the SWP and Central Valley Project. A seismic event in the Delta region that causes levee failure can flood Delta islands with saline water, severely impair water quality, and interrupt SWP exports. The extent of disruption depends on the number and location of levee breaches, the season of occurrence, and the capacity to implement emergency repairs.
• Delta Levee and Colorado River Lower Feeder Failure: The Delta Levee Failure is paired with a seismic event in Southern California that damages the Metropolitan Water District
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IRWD – 2025 Water Shortage Contingency Plan
of Southern California (MWD) Lower Feeder or related conveyance facilities that result in disruptions to imported water deliveries from the Colorado River Aqueduct (CRA). The Lower Feeder is a critical component of MWD’s distribution system, conveying CRA supplies to several member agencies, including IRWD, across the region. The Southern San Andreas Fault intersects major water conveyance systems, including the CRA, at the San Gorgonio Pass. Given its proximity to active fault zones, damage to the Lower Feeder would limit CRA deliveries until repairs are completed. • Dyer Road Well Field Reduced Operations: The Dyer Road Well Field (DRWF) relies on blending water from multiple wells to meet regulatory standards at the blending compliance point; if a portion of these wells are contaminated by emerging contaminants, such as trichloroethylene and per- and polyfluoroalkyl substances, the overall supply may no longer comply at the blending compliance point. Regulatory changes, such as stricter maximum contaminant levels, could also cause the blended supply to fall out of compliance. For the purposes of the 2025 Study, IRWD assumed that emerging contaminants could result in a 50 percent reduction in DRWF contractual and physical pumping capacity. For each of these scenarios, water shortages at the 95 th percentile were estimated based on IRPDSM modelling results and mitigation strategies – additional conservation and additional groundwater storage - were evaluated. The DRWF Reduced Operations scenario did not lead to water shortages as imports are sufficient to meet demands under this relatively low-impact scenario. For the Delta Levee Failure and the combined Delta Levee and Lower Feeder scenarios, the 2025 Study recommends that IRWD plan to mitigate for shortages through continued investments in groundwater storage as well as additional schedulable supplies and water banking well recovery capacity. The 2025 Study concluded that IRWD’s proactive investment in a diversified water supply portfolio positions IRWD to reliably meet future demands across a wide range of disruption scenarios. In addition, the 2025 Study reaffirmed that IRWD can manage risks associated with the range of import disruptions and changing regional conditions, as well as risks to local groundwater supplies through implementation of its WSCP, use of its emergency water banking supplies and continued investments in its supply portfolio. 1. 2 Catastrophic Interruption Catastrophic supply interruptions could be the result of regional power outages, earthquakes, floods, water supply interruptions, structural damage from an explosive device, and threat of or possible contamination to the water system. IRWD’s response to a catastrophic interruption of water supply would depend on the cause, severity, and anticipated duration of the emergency. A potential shortage resulting in a reduction of available supplies can be addressed through a combination of alternative supplies and storage, combined with implementation of the WSCP. Since IRWD's major potable water sources include both imported water (including IRWD’s Water
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IRWD – 2025 Water Shortage Contingency Plan
Banking Program) and local groundwater, it is unlikely that an outage of both sources would occur simultaneously. A 2015 United States Geological Survey (USGS) study entitled UCERF3: A New Earthquake Forecast for California’s Complex Fault System (2015 UCERF3 Study) indicated that the likelihood of one or more earthquakes of magnitude 7.5 or greater over the next 30 years in Southern California was 36 percent. Local seismic events have the potential to temporarily disrupt service from either the regional facilities or local well fields. A seismic event could also cause damage to the well field that would permanently limit the production capability of one or more wells. A draft white paper evaluating Metropolitan’s emergency storage objective (released at their May 14, 2019 Board meeting) evaluated the expected outages from a large earthquake. Table 1-1 shows the shows the estimated maximum outage durations for two imported water sources for IRWD -- the Colorado River Aqueduct, California Aqueduct East Branch – resulting from a large earthquake. Table 1 ‑ 1: Estimated Maximum Outage for IRWD Imported Water Sources Due to Large Earthquake
Aqueducts
Earthquake (>M 7.8)
Colorado River Aqueduct
6 months 24 months
California Aqueduct East Branch
A major seismic event in the Delta with levee failures would have more significant and longer- term impacts to supplies. It would result in flooding of the Delta with saline waters and disruption of water exports to the SWP. The 2015 UCERF3 Study indicated that the likelihood of one or more earthquakes of magnitude 6.7 or greater over the next 30 years in the San Francisco region (which includes the Delta) was 72 percent. DWR’s 2009 Delta Risk Management Strategy (DMRS) estimated that such an earthquake would result in levee failures and simultaneous flooding of 20 islands with saline waters. For a 20-island breach event, the total cost of levee repair and dewatering was estimated to be $1.8 billion (in 2005 dollars) and require 30 months on average to repair breaches and dewater. In addition, a 20-island breach event was estimated to interrupt SWP freshwater flow from the Delta to Southern California and IRWD for 1.5 years.
Metropolitan’s 2025 Seismic Resilience Report discusses how specific planning, engineering, operations, and reporting efforts are needed to reach their three primary objectives:
• Provide a diversified water supply portfolio, system flexibility, and emergency storage. • Prevent damage to water delivery infrastructure in probable seismic events and limit damage in extreme events. • Minimize water delivery interruptions through a dedicated emergency response and recovery organization.
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IRWD – 2025 Water Shortage Contingency Plan
Depending on the cause and severity of the local plant outage or seismic event, potential damage to treatment and conveyance facilities may extend from short to long-term disruptions in imported and local water supply deliveries. Unlike drought conditions, which manifest over several years, the response measures available to respond to a catastrophic interruption are limited. During such an event, the IRWD Board, at its discretion, may choose to implement mandatory measures at earlier levels of shortages. See also Section 1.3 Seismic Risk Assessment and Mitigation Plan below for additional information. For additional information on response to severe drought events and consecutive multi-dry year analyses refer to the UWMP, Sections 6 and 7. 1.3 Seismic Risk Assessment and Mitigation Plan LAW 10632.5. (a) In addition to the requirements of paragraph (3) of subdivision (a) of Section 10632, beginning January 1, 2020, the plan shall include a seismic risk assessment and mitigation plan to assess the vulnerability of each of the various facilities of a water system and mitigate those vulnerabilities. (b) An urban water supplier shall update the seismic risk assessment and mitigation plan when updating its urban water management plan as required by Section 10621. (c) An urban water supplier may comply with this section by submitting, pursuant to Section 10644, a copy of the most recent adopted local hazard mitigation plan or multihazard mitigation plan under the federal Disaster Mitigation Act of 2000 (Public Law 106-390) if the local hazard mitigation plan or multihazard mitigation plan addresses seismic risk. As stated in the CWC Section 10632.5.(a), beginning January 1, 2020, the UWMP shall include a seismic risk assessment and mitigation plan to assess the vulnerability of each of the various facilities of a water system and mitigate those vulnerabilities. An urban water supplier may comply with this section by submitting, pursuant to Section 10644, a copy of the most recent adopted local hazard mitigation plan or multi-hazard mitigation plan under the federal Disaster Mitigation Act of 2000 (Public Law 106-390) if the local hazard mitigation plan or multi-hazard mitigation plan addresses seismic risk. In January 2025, IRWD completed and submitted the “Water System Risk and Resilience Assessment (RRA): A Comprehensive Analysis Consistent with America’s Water Infrastructure Act of 2018 (AWIA)” in coordination with the Municipal Water District of Orange County (MWDOC) and the Water Emergency Response Organization of Orange County (WEROC). This assessment updated the baseline risks created in 2020 to account for new assets and upgrades to the system and adheres to the updated ANSI/AWWA J100-21 Standard. The document was accepted and certified as complete by the Environmental Protection Agency, Exhibit B . In addition, IRWD has completed numerous seismic studies for individual projects and facilities including dam seismic hazard potentials, water system disruption potential in the case of major earthquake, and full system vulnerabilities similar to the AWIA RRA.
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IRWD – 2025 Water Shortage Contingency Plan
IRWD also has prepared an Emergency Operations Plan, updated in September 2025, that includes an extensive specific hazard response plan for earthquakes including mitigation action, response actions, responsible authorities, and phases of response. Furthermore, IRWD partnered with WEROC and its member agencies to prepare the Orange County Water and Wastewater Multi-Jurisdictional Hazard Mitigation Plan (MJHMP) which was approved by FEMA and adopted in 2025. This plan aims to improve local resilience to hazard events and to reduce water and wastewater infrastructure vulnerabilities and risks due to identified hazards of concern. IRWD’s section of the MJHMP is included as Exhibit C . As part of its Dam Safety Program, IRWD has evaluated the seismic performance of its five dams and reservoirs. IRWD continually monitors, inspects and maintains its dams and reservoirs. Its engineers and dam safety experts have implemented a state-of-the-art Dam Safety Program that meets or exceeds all current state standards and provides a roadmap for other agencies to follow. This new program combines the traditional tried and true safety standards with a modern Risk-Informed Decision-Making process, known as RIDM. RIDM is a rigorous, systematic and thorough approach to dam safety that identifies and reduces any risks. Incorporating RIDM results in one of the most robust dam safety and reservoir management programs in the nation. IRWD’s Dam Safety Program builds on industry best practices to ensure that our dams and reservoirs will be safe. A. Excerpts from IRWD Water System Risk and Resilience Assessment (RRA) Due to the sensitive nature of IRWD’s RRA report, certain sections are not appropriate to be released as part of the UWMP and WSCP. The following excerpts have been pulled from the existing RRA Seismic Risk Assessment and Mitigation plan to demonstrate the essential content in assessing seismic risk. I. Overview of Water Emergency Preparedness in Orange County Water distribution and treatment in Orange County involves dozens of agencies and utilities working together and relies on integrated regional systems and facilities. There are many retail water utilities in Orange County, each with its own distinct service area and sources of potable water. The retail water agencies include water districts and city water departments. MWDOC serves more than 2.3 million Orange County, California, residents through 28 cities, water districts, and investor-owned utilities or MAs. MWDOC’s service area covers all of Orange County except the cities of Anaheim, Fullerton, and Santa Ana. WEROC, administered by MWDOC, coordinates emergency response and mutual aid planning for all 35 Orange County water and wastewater agencies including Anaheim, Fullerton, and Santa Ana. WEROC provides its participating agencies and volunteer staff with planning support, emergency preparedness, and response training. In the event of a major emergency affecting Orange County, these volunteers would mobilize at the WEROC emergency operations centers to coordinate response. WEROC works closely with the
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IRWD – 2025 Water Shortage Contingency Plan
County of Orange, Orange County Fire Authority, California State Water Resource Control Board Division of Drinking Water, and other entities to ensure a holistic approach and a well- coordinated emergency response. II. Assessment Approach Following the J100-21 Standard, IRWD’s risk assessment followed a seven-step process that began with the identification and confirmation of critical assets within the potable water system. The previously selected critical assets were presented to the assessment team for review and update. Next, the assessment team identified and prioritized the set of threats, against which the assessment was to be conducted. All reference threats along with three additional threats (aging infrastructure, drought, and earthquake liquefaction) were considered, with 17 threats being used in the assessment. The final list of 117 threat-asset pairs were assessed for their consequences from the threat, vulnerability to the threat, and likelihood of threat occurrence. The final risk baseline values were presented to the assessment team for an evaluation of accuracy and completeness. III. Key System Elements IRWD’s potable water facilities include the Dyer Road Wellfield, the Baker Water Treatment Plant, the Irvine Desalter Project which treats drinking water in the Irvine sub-basin, the Deep Aquifer Treatment System that removes the tinted color from local groundwater, Wells 21 and 22 Desalter Project, that recovers and treats local impaired groundwater for potable use, and 36 drinking water reservoirs with a combined 150 MG storage capacity. Potable water is distributed through 1,767 miles of distribution pipelines. IV. Vulnerability Assessment After identifying critical assets and the threats of concern, each critical asset was paired to every identified threat. The assessment team then evaluated the plausibility of the identified threat having significant consequence to the critical asset and prioritized those threat-asset pairs of concern to their system. Out of a possible 810 pairs, a total of 117 threat-asset pairs were ultimately selected to be included in the assessment. These threat-asset pairs represent the most significant concern to the District. V. Earthquake Liquefaction Liquefaction takes place when loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking. Liquefaction occurring beneath buildings and other structures can cause major damage during earthquakes. For example, during the 1989 Loma Prieta, California, earthquake, liquefaction of the soils and debris used to fill in a lagoon caused major subsidence, fracturing, and horizontal sliding of the ground surface in the Marina district in San Francisco. The risk assessment team identified earthquake liquefaction to be a threat of concern to water assets located in liquefaction zones. Earthquake liquefaction is a concern for the Michelson Ops Complex (which includes the Michelson Operations Center, the Chemical Storage Facility
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IRWD – 2025 Water Shortage Contingency Plan
and the LAWRP Fuel Facility) and the Deep Aquifer Treatment System (DATS) facility (which includes two wells and DATS plant). VI. Seismic Mitigation Actions Due to the inherent seismic risk associated with infrastructure based in Southern California the following mitigation actions have already been implemented or are currently being considered to alleviate potential risks: • Implement low-cost, easy to implement, earthquake mitigation measures in facilities (e.g., bracing items to walls, anchoring equipment to the slab, installing earthquake-activated shut-off valves, providing flexible connections to piping or conduit). • Monitor changes and updates to building codes and seismic regulations to determine if IRWD-owned critical facilities may need seismic retrofits as they age and building codes are updated. • Implementing earthquake mitigation measures for critical operations. • Include assessment and mitigation of potential liquefaction conditions in the scope of any new building or infrastructure project. • Perform monthly checks on permanent and portable backup generators. • Maintain WEROC membership for communication and collaboration opportunities with regional water districts, including identification and implementation of mitigation actions with shared benefits. • Consider implementing backup communication systems such as satellite phones and amateur radio. • Consider moving backup servers to locations that are not on the same earthquake fault lines as the primary servers or to cloud-based services. • Consider developing and seeking funding for an evaluation program to determine the seismic vulnerability of critical assets. • Evaluate dam improvements to increase resiliency in coordination with the Dam Safety Program and Implementation Plan • Regularly conduct earthquake and evacuation drills with all staff. 1.4 Multiple Dry Year Analysis and Drought Risk Assessment IRWD’s 2025 UWMP includes an assessment of IRWD’s reliability during normal, dry, and multiple dry water years as well as a Drought Risk Assessment (DRA). The DRA and WSCP share a similar purpose and are developed to jointly assess IRWD’s current and future water reliability, especially during extended periods of drought. The water reliability analyses indicate that IRWD is reliable throughout all conditions including single dry year, multiple dry year, as well as during an extended drought. Table 1-2 shows the results of the potable multiple dry year water reliability analysis. See IRWD 2025 UWMP Section 7 for the full normal, single-dry, and multiple dry year analysis and tables.
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IRWD – 2025 Water Shortage Contingency Plan
Results of the DRA indicate that IRWD has sufficient supplies to meet its projected demands, even during multiple dry years ( Table 1-3 ). Supplies are expected to exceed IRWD’s projected water use for all future years evaluated ( Table 1-2 and Table 1-3 ). Recycled water is considered a drought resistant supply. Therefore, Table 1-2 and Table 1-3 show only potable supplies and demands. For additional tables and non-potable results refer to the 2025 UWMP Section 7 and Appendix D. The DRA indicates that even in five years of consecutive drought there is a water supply surplus without the use of WSCP response actions. When Metropolitan WSCP response actions trigger a Level 10 shortage condition (more than 50% reduction in imported supplies), IRWD would only be in a Level 1 shortage condition (less than 10%, see WSCP Section 3.1) due to its diversified portfolio and availability of local supplies For additional details on the Multiple Dry Year Analysis and DRA refer to 2025 UWMP Section 7. Table 1 ‑ 2: Multiple Dry Year Water Reliability Analysis – Potable Water DWR Submittal Table 7-4 Retail: Multiple Dry Years Supply and Use Comparison - Potable 2030 2035 2040 2045
Supply totals
101,863 101,863 101,863 101,863
First year
Use totals
55,772 46,091
56,394 45,469
56,911 44,952
56,999 44,864
Surplus/(shortfall)
Supply totals
101,863 101,863 101,863 101,863
Second year
Use totals
56,330 45,533
56,958 44,905
57,480 44,383
57,569 44,294
Surplus/(shortfall)
Supply totals
101,863 101,863 101,863 101,863
Third year
Use totals
56,893 44,970
57,528 44,335
58,055 43,808
58,144 43,719
Surplus/(shortfall)
Supply totals
101,863 101,863 101,863 101,863
Fourth year
Use totals
56,324 45,539
56,953 44,910
57,474 44,389
57,563 44,300
Surplus/(shortfall)
Supply totals
101,863 101,863 101,863 101,863
Fifth year
Use totals
53,508 48,355
54,105 47,758
54,600 47,263
54,685
Surplus/(shortfall) 47,178 NOTES: [1] Use totals are based on average year values provided by MWDOC with a: 5% increase in Year 1; 1% increase in Year 2 and Year 3; 1% decrease in Year 4; and a 5% decrease in Year 5. Source: IRWD 2025 UWMP, DWR Table 7 – 4
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IRWD – 2025 Water Shortage Contingency Plan
Table 1 ‑ 3: Five-Year Drought Risk Assessment Tables – Potable Water DWR Submittal Table 7-5 Retail: Five-Year Drought Risk Assessment - Potable 2026 Total Total Water Use 55,418 Total Supplies 99,623 Surplus/Shortfall w/o WSCP Action 44,205 2027 Total Total Water Use 55,972 Total Supplies 100,183 Surplus/Shortfall w/o WSCP Action 44,211 2028 Total Total Water Use 56,532 Total Supplies 100,743 Surplus/Shortfall w/o WSCP Action 44,211 2029 Total Total Water Use 55,967 Total Supplies 101,303 Surplus/Shortfall w/o WSCP Action 45,336 2030 Total Total Water Use 53,168 Total Supplies 101,863 Surplus/Shortfall w/o WSCP Action 48,695 NOTES: [1] Use totals are based on: 5% increase in Year 1; 1% increase in Year 2 and Year 3; 1%
decrease in Year 4; and a 5% decrease in Year 5. Source: IRWD 2025 UWMP, DWR Table 7 - 5
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IRWD – 2025 Water Shortage Contingency Plan
Section 2 – Annual Water Supply and Demand Assessment Procedures The IRWD Board, in accordance with the provisions of the CWC, will determine and declare the shortage level based on an assessment of the available supplies and demands. The evaluation process is conducted to determine if a shortage declaration is needed, and at what level. The shortage level is calculated by projecting total short-term water demands within IRWD’s service area and comparing those demands to the available water supplies. The supply analysis includes evaluation of hydrologic and regulatory conditions that could impact supplies such as imported water, groundwater, and surface water. Drought resilient, hydrologically independent supplies, such as recycled water, are considered fully reliable and can be excluded from the required estimated shortage reduction. Since 2022, each supplier is required by the CWC to submit an annual water supply and demand assessment to DWR by July 1 of each year. Procedures for determining IRWD’s annual water supply and demand assessment (AWSDA) are provided below. 2.1 Water Supply and Demand Assessment Requirements LAW 10632.1. An urban water supplier shall conduct an annual water supply and demand assessment pursuant to subdivision (a) of Section 10632 and, on or before July 1 of each year, submit an annual water shortage assessment report to the department with information for anticipated shortage, triggered shortage response actions, compliance and enforcement actions, and communication actions consistent with the supplier’s water shortage contingency plan. An urban water supplier that relies on imported water from the State Water Project or the Bureau of Reclamation shall submit its annual water supply and demand assessment within 14 days of receiving its final allocations, or by July 1 of each year, whichever is later.
10632. (a) Every urban water supplier shall prepare and adopt a water shortage contingency plan as part of its urban water management plan that consists of each of the following elements:
(1) The analysis of water supply reliability conducted pursuant to Section 10635. (2) The procedures used in conducting an annual water supply and demand assessment that include, at a minimum, both of the following: (A) The written decision-making process that an urban water supplier will use each year to determine its water supply reliability. (B) The key data inputs and assessment methodology used to evaluate the urban water supplier’s water supply reliability for the current year and one dry year, including all of the following:
(i) Current year unconstrained demand, considering weather, growth, and other influencing factors, such as policies to manage current supplies to meet demand objectives in future years, as applicable.
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IRWD – 2025 Water Shortage Contingency Plan
(ii) Current year available supply, considering hydrological and regulatory conditions in the current year and one dry year. The annual supply and demand assessment may consider more than one dry year solely at the discretion of the urban water supplier. (iii) Existing infrastructure capabilities and plausible constraints. (iv) A defined set of locally applicable evaluation criteria that are consistently relied upon for each annual water supply and demand assessment. (v) A description and quantification of each source of water supply. 2.2 Annual Water Supply and Demand Assessment Procedures CWC Section 10632(a)(2) requires that urban water suppliers prepare and submit an Annual Water Supply and Demand Assessment (AWSDA). IRWD’s AWSDA is a determination of the near-term outlook for supplies and demands and identification of any expected shortage that may prompt response actions in the current year. IRWD’s AWSDA supply and demand estimates may differ from IRWD’s projections used for long term planning and are not intended for that purpose. Available supplies are assessed through ongoing coordination with wholesalers, groundwater managers, and IRWD facility operators and staff. Due to the nature of IRWD’s water supply system, many supplies are tracked and managed directly by IRWD on an operational basis. IRWD’s diversified water portfolio allows for multiple sources to be available to meet projected customer demands in varying circumstances. To project water demands for the AWSDA reliability analysis, IRWD uses historical customer water usage data. This data is evaluated in conjunction with local weather conditions, estimated water use requirements, and is adjusted to account for population growth. IRWD has implemented successful water use efficiency and outreach programs since the early 1990’s. These efforts, combined with the long-term use of budget-based rates, have resulted in IRWD having relatively consistent levels of customer water use demands, and less discretionary water use over time. The AWSDA considers this customer use trend in the overall analysis. The following AWSDA methodology includes a written decision-making process to determine water supply reliability. Once completed, the AWSDA is reviewed by IRWD’s senior management. A. Key Data Inputs The following data components are important inputs to the preparation of IRWD’s AWSDA. 1) The first component of the AWSDA, is the estimated acre-feet (AF) of water sales derived from customer usage data. This is based on actual water sales from previous fiscal years (FY). The customer usage data is categorized by water type (treated, untreated, recycled) as well as customer type. Actual water sales are tracked and finalized at the end of each FY in a database managed by the IRWD Finance Department.
2) The second component of the AWSDA is the availability of water supplies by water type (treated, untreated, recycled) in AF. IRWD’s Operations Department provides estimates
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IRWD – 2025 Water Shortage Contingency Plan
for treated and untreated water supplies. IRWD Recycled Water Operations provides estimates for production of recycled water-based supplies. Certain supply sources may be limited by existing contractual agreements or wholesaler capacities. Any limitations in supply availability are incorporated into the annual supply assessment. 3) The third component of the AWSDA are adjustments for weather variability (based on dry year and wet year conditions), growth (based on population data from the Center for Demographic Research (CDR), as well as any changes to existing infrastructure capacities or plausible constraints. B. Assessment Methodology and Procedures The preparation of IRWD’s AWSDA uses the following methodology and procedures, which may be expanded and amended in the future. Any such changes will accomplish the same goal of assessing the IRWD’s water supply reliability and potential shortages. Should the assessment indicate a potential shortage, the triggered shortage response actions, compliance and enforcement actions, and communication actions will be consistent with the WSCP as required in CWC Sections 10632 and 10632.1. Step 1: Access Historic Customer Use Data The basis of the IRWD AWSDA is historic customer water use data, compiled in a local database and maintained by the IRWD Finance Department. At the end of each fiscal year, actual water uses, and sales are verified for accuracy. Customer demand projections for the purpose of the AWSDA are based on actual water deliveries tracked by the Finance Department. Customer usage is sorted by supply type and calculated for each FY (July - June) in AF. Units of AF are used throughout the entire AWSDA. In accordance with CWC 10632(a)(2)(B), IRWD considers the projected current year available supply and demand as Year 1 and one dry year as Year 2. Step 2: Determine Available Supplies Estimating available supplies is accomplished by determining the volume of each supply source reasonably anticipated to be available that year and the estimated percentage loss during treatment or delivery based on past operations data. These values are estimated by IRWD facility operators monitoring available supplies (Baker Water Treatment Plant, Irvine Desalter Project, Dyer Road Well Field, Deep Aquifer Treatment System, Wells 21 and 22, Howiler Treatment Plant, Michelson Water Recycling Plant, Los Alisos Water Recycling Plant, recycled water storage reservoirs), and through coordination with water supply partners including but not limited to groundwater managers (Orange County Water District (OCWD)), and wholesalers (Metropolitan and MWDOC) to confirm expected availability of supplies for each year. In addition to estimating available supplies to meet annual customer demands, estimates are also calculated for supplies held in emergency storage in IRWD’s Water Banking Program that can be made available. Through IRWD’s water banking operations in Kern County, IRWD maintains supplies in emergency storage that can be recovered and delivered into IRWD’s service area through a Coordinated Operating, Water Storage, Exchange and Delivery
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IRWD – 2025 Water Shortage Contingency Plan
Agreement with Metropolitan and MWDOC, (Coordinated Operating Agreement, see “Available Supply Coordination: Water Banking” section below). IRWD is involved in numerous programs to help reduce dependence upon imported water (the most expensive source). These programs may influence the timing of the various sources and supply availability. Please see “Description and Quantification Section” below for more detail on individual supply sources. Available Supply Coordination: OCWD & Groundwater For groundwater supplies, coordination efforts are implemented with OCWD, which manages the Orange County Groundwater Basin (Basin). Approximately 50 percent of IRWD’s overall supply comes from its groundwater wells in the Basin. Each year OCWD sets a target amount of pumping and establishes a Basin Pumping Percentage (BPP) for the groundwater producers. The BPP is the ratio of groundwater production to total water demands expressed as a percentage. To discourage pumping above the established BPP, any groundwater production above the BPP is charged a Basin Equity Assessment (BEA) which is set so that the cost of groundwater pumping is similar to the cost of imported water. Some of IRWD’s treated groundwater supplies are exempt from the BEA. The majority of the potable groundwater used by IRWD is produced from its Dyer Road Well Field (DRWF) located in the City of Santa Ana. The DRWF consists of 16 wells that pump from the clear water zone of the Basin and two wells (with colored-water treatment facilities) that pump from the deep, tinted-water zone of the Basin. The tinted-water portion of the DRWF is referred to as the Deep Aquifer Treatment System (DATS). Through an existing agreement, the DRWF production is limited to 28,000 AF per year (AFY) consisting of 20,000 AFY of clear groundwater and an additional 8,000 AFY of “matching” clear groundwater, provided a minimum of 8,000 AFY of colored groundwater is pumped from the deep aquifer zone. Available Supply Coordination: Metropolitan & MWDOC (Imported Water) IRWD receives imported water through MWDOC. MWDOC is a wholesale member agency Metropolitan. IRWD submits imported water supply requests to MWDOC, which then incorporates the request into a regional order of water for imported supplies to Metropolitan. Both Metropolitan and MWDOC provide wholesaler information indicating their ability to meet IRWD anticipated imported water demands. Metropolitan and MWDOC both state in their UWMP and WSCP that these imported supplies are reliable through multiple, consecutive years of drought. The wholesale agencies are also involved with coordination of deliveries from IRWD’s Water Banking Program to be used in the event of imported water shortages. Available Supply Coordination: Water Banking IRWD has diversified its water supply reliability by developing cost effective water banking projects, as emergency storage, in Kern County, California. IRWD has constructed a fully operational Water Banking Program that makes it possible for IRWD and its banking partners to store excess water during “wet” hydrologic periods. The stored water is then available for use
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IRWD – 2025 Water Shortage Contingency Plan
during “dry” periods to offset reduced water supplies under periods of severe drought or during periods of supply interruptions. Water banking, recharge, storage, and recovery programs provide a cost effective and reliable supplemental source of water that can be relied upon during major droughts and periods of supply interruptions. IRWD has secured water supplies for its water banking projects through unbalanced exchange partnerships with other agencies. These partnerships allow agencies with surplus water to store water in IRWD’s water banking projects in return for transferring half or more of the water to IRWD. In addition, as previously stated, wheeling and exchange agreements including a long-term Coordinated Operating Agreement with MWDOC and Metropolitan allows the delivery of SWP supplies from IRWD’s Water Banking Program to the IRWD service area (see “Emergency Supplies – Water Banking” below for quantification of supplies made available). Step 3: Calculate Projected Customer Demands for Year 1 Once the historic customer demand data is obtained, IRWD updates existing customer type information and monthly water use by customer and water type. To calculate the unconstrained demand for IRWD customers, an average is taken across the past three fiscal years, by all customer and water types to determine the upcoming customer demand projections. This is the projected unconstrained customer demands for Year 1. The unconstrained demand includes all customer types (i.e. residential, landscape, CII, data centers etc.) and water types (potable and non-potable). Step 4: Apply Adjustments for Expected Weather, Growth, and Capacity Changes Once the base customer unconstrained demands are projected, then adjustments are made for local weather conditions, population growth and any expected capacity changes for that year. These projections are used as a comparison to validate the three-year average, to track changing demands across all fiscal years and to identify wet, normal, and dry year trends in customer demands. Water supply and demand conditions are prone to fluctuation each year. IRWD’s historic planning methods and diverse portfolio of water supplies allow for accommodating these annual fluctuations relatively easily, with additional built-in measures for significant changes when necessary. The AWSDA specifically takes into account population growth when comparing customer demand changes from year to year. Population Growth In addition to the fiscal year average, calculations are performed comparing customer demand changes, by customer type, across all fiscal years, normalized for population growth each year. Population growth data, as calculated by the CDR at California State Fullerton, is supplied each January by MWDOC for the IRWD service area. The ongoing customer water use calculations are based on fiscal year use data for total water sources, total potable sources, and total recycled sources. Using the data obtained from CDR, these total values are then normalized across fiscal years by taking the ratios of AF per customer. The percentage change calculated
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between each individual water supply source is then comparable across years with respect to population growth. Weather When conditions are indicative of a dry year or continuous dry years additional adjustments are made by comparing historical dry year customer demands. The customer demands analysis utilizes changes in demands pre- and post- water reduction drought declaration and water use reduction mandates with data going back to 2010 through present. Local California Irrigation Management Information System (CIMIS) data, obtained from station #75 Santa Ana, is also used to track changes in service area weather conditions. Values for evapotranspiration, rainfall, and air temperature are measured at the hourly, daily, and annual scale. CIMIS data is used to track historic trends and allow for additional adjustments and refinement to projected customer demands based on past trends for similar conditions. Capacity Changes Capacity changes related to large-scale supply availability are also considered. These include, but are not limited to, new facility operations, closed facility operations, state mandates, changes to the BPP, and water delivery schedules. For example, knowledge of a scheduled facility closure during the year for project improvements, repairs, replacements or upgrading infrastructure may alter the availability of the supply source for that upcoming year depending on the duration of the work involved. When applicable, the available supply is adjusted for the upcoming year. After the projected demands for the upcoming fiscal year are calculated, adjustments are made to the first-year projected demands based on projected changes to operations by source due to expected weather, growth, and facility capacities. Step 5: Calculate Projected Customer Demands for Year 2 (Single Dry Year) For the purpose of the AWSDA an additional single dry year of projected demands are also calculated for the subsequent year. This provides the projected customer demands for Year 2. The demands for a single dry year are described as follows: Single dry year customer demand projections are based on historic trend analysis under dry year conditions. The analysis uses data for Dry, Wet, and Normal water years is obtained from DWR and cross-checked with the federal drought monitor run by National Integrated Drought Information System (NIDIS) at the state and local level. This information for different year conditions is then applied to the existing percentage change in customer historic water use calculations. Step 6: Compare Total Supply and Demands – Assess Possible Shortage Once demand calculations for Year 1 and Year 2 have been completed, adjustments have been applied, and water supply availability has been confirmed, IRWD staff compares total demands to total supplies. Then, IRWD can ascertain if a supply shortage is anticipated.
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IRWD – 2025 Water Shortage Contingency Plan
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