South Coast

Los Angeles Basin Stormwater Conservation Study: Task 2 Water Supply & Water Demand Projections

U.S. Bureau of Reclamation (USBR) | December 1st, 2014

The Los Angeles County Flood Control District (LACFCD) partnered with the U.S. Department of the Interior, Bureau of Reclamation (Reclamation) to collaborate on t

The Los Angeles County Flood Control District (LACFCD) partnered with the U.S. Department of the Interior, Bureau of Reclamation (Reclamation) to collaborate on the Los Angeles Basin Stormwater Conservation Study (LA Basin Study). The purpose of the LA Basin Study is to study long-term water conservation and flood control impacts from projected climate conditions and population changes in the Los Angeles Basin. The LA Basin Study will recommend potential changes to the operation of stormwater capture systems, modifications to existing facilities, and development of new facilities that could help resolve future water supply and flood control issues. The recommendations will be developed through identifying alternatives and conducting trade-off analyses. For Task 2 of the LA Basin Study, Water Supply and Water Demand Projections, existing and projected water supplies and demands were characterized for the LA Basin Study Area (Study Area) out to 2095, with consideration of projected climate change effects. It is important to note that this Task 2 report inventories projected available supplies (i.e., potential supplies), and does not make assumptions for the volume of each supply source that will actually be used to meet projected demands, nor the facilities necessary to access and serve those supplies. This determination would require more in-depth integrated supply and demand planning to predict and analyze the multitude of factors that influence water supply and use decisions such as policy, cost, environmental factors, reliability, etc. This Task 2 report is intended to provide a supply and demand basis for understanding the potential need and benefit of additional stormwater capture systems that could be implemented across the region by the LACFCD and its partners. Given that stormwater is a local and relatively inexpensive source of supply, it must be a critical and substantial part of the LA Basin water supply portfolio that could help meet demands through 2095 and beyond.

Los Angeles Basin Stormwater Conservation Study: Task 3.1 Climate Change and Hydrologic Projections Appendices

U.S. Bureau of Reclamation (USBR) | October 1st, 2013

Reclamation’s Technical Service Center (TSC) performed Task 3.1 of the LA Basin Study—to develop and evaluate projected future climate conditions related to precipita

Reclamation’s Technical Service Center (TSC) performed Task 3.1 of the LA Basin Study—to develop and evaluate projected future climate conditions related to precipitation frequency over the Los Angeles Basin. The subtasks were to: Consider existing projections of climate change in the LA Basin Study area Determine appropriate climate scenarios for use in developing precipitation and potential evaporation input datasets to support subsequent hydrologic modeling Prepare data (hourly precipitation and potential evaporation) for input into the LACFCD’s Watershed Management Modeling System (WMMS) Determine storm event frequency for planning purposes The data, methods, and results from Task 3.1 are documented in this report. Results from these four subtasks were then transmitted to LACFCD, who used these results as input in their WWMMS as part of Task 3.2 of the LA Basin Study. LACFCD is preparing a companion report with the results from the hydrologic modeling.

Los Angeles Basin Stormwater Conservation Study: Task 3.2 Hydrologic Modeling Report

U.S. Bureau of Reclamation (USBR) | December 3rd, 2013

The Los Angeles County Flood Control District (LACFCD) partnered with the U.S. Department of the Interior, Bureau of Reclamation (Reclamation) to collaborate on t

The Los Angeles County Flood Control District (LACFCD) partnered with the U.S. Department of the Interior, Bureau of Reclamation (Reclamation) to collaborate on the Los Angeles Basin Stormwater Conservation Study (LA Basin Study). The purpose of the LA Basin Study is to investigate long-range water conservation and flood control impacts caused by projected changes in climate conditions and population in the Los Angeles region. The LA Basin Study will recommend potential modifications or changes in the operation of the existing stormwater capture systems, and the development of new facilities that could help resolve future water supply and flood control issues. These recommendations will be developed by identifying alternatives and conducting trade-off analyses. For Task 3, Downscaled Climate Change and Hydrologic Modeling of the LA Basin Study, Reclamation developed downscaled climate change projections, while LACFCD applied these projections to generate the future hydrology. LACFCD utilized the Watershed Management Modeling System (WMMS) to perform the hydrologic modeling for the LA Basin Study. This report summarizes the data, methods, and results of the historic and future hydrologic modeling. The purpose of Task 3.2, Hydrologic Modeling is to simulate hydrology with respect to climate change for the Los Angeles River, San Gabriel River, Ballona Creek, South Santa Monica Bay, North Santa Monica Bay, Malibu Creek, and Dominguez Channel/Los Angeles Harbor watersheds (Basin Study Watersheds). This study incorporates the entire watershed boundaries, including where they extend outside of Los Angeles County. The following sub-tasks were identified to achieve this objective: Historic Hydrologic Modeling (Water Year 1987 through 2000) Determine baseline scenario modeling assumptions Prepare WMMS to simulate baseline scenario Perform WMMS baseline simulations Analyze and summarize WMMS results Projected Hydrologic Modeling (Water Year 2012 through 2095) Determine future scenario modeling assumptions Prepare WMMS to simulate future scenarios Perform WMMS simulations Analyze and summarize WMMS results

Los Angeles Basin Stormwater Conservation Study: Task 4 Existing Infrastructure Response & Operations Guidelines Analysis

U.S. Bureau of Reclamation (USBR) | September 1st, 2014

The Los Angeles County Flood Control District (LACFCD) partnered with the U.S. Department of the Interior, Bureau of Reclamation (Reclamation) to collaborate on the Los A

The Los Angeles County Flood Control District (LACFCD) partnered with the U.S. Department of the Interior, Bureau of Reclamation (Reclamation) to collaborate on the Los Angeles Basin Stormwater Conservation Study (LA Basin Study). The purpose of the LA Basin Study is to investigate long-range water conservation and flood risk impacts caused by projected changes in climate conditions and population in the Los Angeles region. The LA Basin Study will recommend potential modifications or changes in the operation of the existing stormwater capture systems as well as the development of new facilities that could help resolve future water supply and flood risk issues. These recommendations will be developed by identifying alternatives and conducting trade-off analyses.  For Task 4, Existing Infrastructure Response and Operations Guidelines Analysis of the LA Basin Study, Reclamation, the U.S. Army Corps of Engineers (USACE), and the LACFCD jointly analyzed the major components of the water conservation and flood risk mitigation system. For the analysis, Reclamation assessed the 14 major LACFCD dams and reservoirs, USACE analyzed their 4 major flood control dams in the region, and LACFCD assessed the 26 major spreading grounds interconnected to the water conservation system. The LACFCD also evaluated 5 major channel outlets. This report summarizes the data, methods, and results of the existing infrastructure response to the historic climate and future projections.  The purpose of Task 4 is to assess the response of existing infrastructure and analyze the operation guidelines under both the current and future climate conditions. It is important to recognize that this effort relies upon the existing configuration of the water conservation and flood risk mitigation network as the baseline condition.  This evaluation includes a ranking assessment of the current and future stormwater volumes conserved or discharged, and other impacts to the water conservation and flood risk mitigation system. The following sub-tasks were identified to conduct this assessment:  Response to Current Climate (Water Year 1987 through 2000)  Analyze stormwater volumes conserved or discharged Analyze infrastructure response and operations guidelines  Response to Future Climate (Water Year 2012 through 2095) Analyze stormwater volumes conserved or discharged Analyze infrastructure response and operations guidelines The response to the current climate provided a representation of the existing situation and revealed how the existing infrastructure could reasonably be expected to perform under a historical climate to which the region has become accustomed. However, this may not be the case in the future. The response to future climate assessed the existing infrastructure under varying climate conditions to understand if it would function satisfactorily. This analysis of the existing infrastructure served as a status quo assessment of historical conditions as well as a “no action” evaluation of the future.  After the analysis of the historic and future climate conditions, an assessment was conducted for the system of dams and spreading ground facilities. A water conservation ranking—or performance level—was developed to assess the overall efficiency and resilience of the facilities to both the historic and projected future climate. Although results are assigned to the individual 18 dams/reservoirs and 26 spreading grounds, each facility was analyzed within the entire system. The dams and spreading grounds were ranked according to their performance with respect to one another; these rankings were used to develop the Task 4 performance levels.  Generally, facilities that were the least efficient resulted in being the least resilient to climate change and were assigned Performance Level III which has a high potential for enhancements. Facilities that were generally more efficient were more resilient to climate change and were assigned Performance Level II. Finally, facilities that were the most efficient tended to be the most resilient to climate change and were assigned to Performance Level I.  For the channel outlet analysis, assessment levels were developed to determine which of the five major channel outlets have the highest potential for increasing stormwater capture and reducing runoff to the Pacific Ocean. The ability to reduce the stormwater runoff that is lost to the ocean and capture it would greatly boost the potential stormwater supply in this region. The Task 4 analysis assigned assessment levels to the 5 major channel outlets and their respective watersheds.  The Los Angeles River ranked into Assessment Level III indicating that this watershed has the greatest potential for increasing stormwater supplies and should be targeted for future enhancements. For the remaining outlets, although these locations were found to have lower discharge volumes, additional capture efforts should still be targeted within these watersheds to further increase stormwater capture and improve local water supplies. 

Los Angeles Basin Stormwater Conservation Study: Task 5 Infrastructure & Operations Concepts Report

U.S. Bureau of Reclamation (USBR) | December 1st, 2015

The Los Angeles Basin Stormwater Conservation Study (LA Basin Study) is a collaborative partnership between the Los Angeles County Flood Control District (LACFCD) and the

The Los Angeles Basin Stormwater Conservation Study (LA Basin Study) is a collaborative partnership between the Los Angeles County Flood Control District (LACFCD) and the U.S. Department of the Interior, Bureau of Reclamation (Reclamation). The purpose of the LA Basin Study is to investigate long-range water conservation and flood risk management impacts caused by projected changes in the climate and population in the Los Angeles region. The LA Basin Study provides recommendations for potential modifications and changes to the existing regional stormwater capture system, as well as for the development of new facilities and practices, which could help to resolve future water supply and flood risk management issues. The stormwater capture concepts and alternatives developed within this report will inform the Task 6 – Trade-Off Analysis & Opportunities report of the LA Basin Study.  The objective of Task 5, Infrastructure and Operations Concepts, is to identify and develop both structural and nonstructural (i.e., plans and policies) concepts to manage stormwater under projected climate conditions for the Los Angeles Basin watersheds, which include: Los Angeles River, San Gabriel River, South Santa Monica Bay, North Santa Monica Bay, Ballona Creek, Malibu Creek, and Dominguez Channel/Los Angeles Harbor watersheds (Basin Study Watersheds). The efforts and results previously completed for Task 2 – Water Supply & Water Demand Projections, Task 3 – Downscaled Climate Change & Hydrologic Modeling, and Task 4 – Existing Infrastructure Response & Operations Guidelines Analysis serve as the foundation for Task 5. The major tasks and subtasks of Task 5 include:  Concept Development  - Identify a range of opportunities and options using stakeholder input  - Determine preliminary concepts for further evaluation  Technical Analysis of Concepts  - Assess structural and nonstructural concepts pertaining to dams, spreading grounds, flood control channels, decentralized storage, infiltration, reuse facilities, debris basins, and other concepts  - Develop and apply concept selection criteria  Appraisal-Level Analysis  - Evaluate selected concepts for future system reliability, efficiency, and effectiveness  In addition to any new stormwater conservation concepts that are developed, the existing facilities from the Task 4 analysis were considered for enhancement. The Watershed Management Modeling System (WMMS), which has served as the primary hydrologic model throughout the LA Basin Study, continued to be the preferred tool and was also used for Task 5. Hydrologic simulations were conducted to analyze the potential water conservation and flood risk mitigation benefit for the various project concepts. For the future period, water years 2012 through 2095, four climate projections (Low 1, Low 2, Mid 2, and High 1) from Task 4 were used in the simulations.  Click here for USBR's Task 5 Appendices index: Appendix A - Infrastructure and Operations Concepts (Excel) Appendix B - Local Stormwater Capture (PDF)  Appendix C - Modeling Approach and Solutions (PDF) Appendix D - Local Management Cost (Excel) Appendix D - Regional 1 Cost (Excel) Appendix D - Regional 2 Cost (Excel) Appendix D - Regional 3 Cost (Excel) Appendix D - Storage 3 Cost (Excel) Appendix E - LACFCD Dam Hydrology and Cost Estimates (PDF)

Los Angeles Basin Study Summary Report

U.S. Bureau of Reclamation (USBR) | November 1st, 2016

Changing demographics, climate change, and competing interests for available water supplies all present long-term risks to the stability and reliability of the region’s

Changing demographics, climate change, and competing interests for available water supplies all present long-term risks to the stability and reliability of the region’s imported water.  The region recognizes that today’s challenges require an integrated water resources management approach. For decades, this region has operated and maintained one of the most effective flood control systems in the world that protects millions of people from the impacts of flooding in the region. This system sends much of the stormwater runoff into the ocean, water that historically recharged local groundwater basins, making this region even more dependent on imported water supplies. As regulatory pressure to clean up polluted stormwater runoff continues and imported water resources diminish, this local source of water supply is becoming more and more attractive (GLAC IRWMP 2014). Many of the region’s water management agencies have studied and planned for increasing use of local recycled and graywater supplies, ocean and brackish desalination, developing more groundwater, and implementing improved water conservation initiatives to extend existing supplies. Additionally, social trends and concerns also drive the emphasis on the use of local water supplies. However, the one major local resource that has not been studied in-depth is stormwater and its opportunities to optimize the reliability of local supplies. To enhance the capabilities of the existing stormwater conservation infrastructure within the Los Angeles Basin, the LACFCD began to investigate long-term projected needs and future climate conditions within the region. Given that local groundwater plays such a vital role in the region’s water supply portfolio, detailed scientific, engineering, and economic analyses were conducted to identify strategies for enhancing stormwater capture for groundwater recharge. The LA Basin Study examined the region’s water supplies and demand, and impacts from projected population growth and changing climate in the watersheds of the Los Angeles region. The objectives of the study were to: • Use state-of-the-art climate change analysis to develop projections of future water supply and demands in the Basin. • Analyze how the Basin’s existing water infrastructure and its operations will perform in the face of changing water realities. • Develop and highlight opportunities to adapt to current and future water demands. • Conduct a trade-off analysis of identified opportunities. Concepts ranged from enhancing the existing stormwater capture system and modifying existing facilities (including those capturing runoff for groundwater recharge), to developing new structural and nonstructural concepts that could help resolve future water supply and flood risk issues. This Summary Report presents highlights of the critical tasks associated with this Basin Study and the results and findings produced throughout this collaborative study effort. Full study chapters and appendices: Plan of Study Fact Sheet Task 2: Water Supply and Demand Task 3: Climate Change Analysis Task 3.1: Development of Climate-Adjusted Hydrologic Model Inputs Task 3.1:  Climate Change and Hydrologic Projections Appendices Task 3.2:  Hydrologic Modeling Report Task 3.2: Annual Hydrologic Results Workbook Task 4: Existing Infrastructure Response & Operations Guidelines Analysis Final Report Task 5: Task 5 - Infrastructure & Operations Concept Analysis Final Report Task 6: Trade-off Analysis Final Report Click here for Reclamation's full index  including public outreach and webinars

Los Angeles County Department of Public Works Hydrology Manual

Los Angeles County Department of Public Works (LACDPW) | January 30th, 2006

This manual establishes the Los Angeles County Department of Public Works' hydrologic design procedures and serves as a reference and training guide. This manual contains

This manual establishes the Los Angeles County Department of Public Works' hydrologic design procedures and serves as a reference and training guide. This manual contains charts, graphs, and tables necessary to conduct a hydrologic study within the County of Los Angeles. Examples provide guidance on using the hydrologic methods.

Los Angeles County Water Plan 2023

Los Angeles County Department of Public Works (LACDPW) | December 5th, 2023

Over 200 agencies in Los Angeles County manage a complex network of water systems to meet the needs of our communities and environment. To achieve sustainability, resilie

Over 200 agencies in Los Angeles County manage a complex network of water systems to meet the needs of our communities and environment. To achieve sustainability, resilience, and equity, cross-sector teamwork and a holistic approach to best leverage natural systems and infrastructure are essential. This plan is a living document. The targets, strategies, and actions are a starting point in this effort. The CWP is not intended to address every water-related issue in Los Angeles County. Instead, it builds upon and complements the many existing local and regional water planning efforts by focusing on four key focal areas where new or additional regional collaboration can add value. These four key focal areas were established through a gaps analysis, which included a review of local and regional planning documents, along with initial stakeholder discussions encompassing a variety of perspectives. For each of the four key focal areas, the CWP describes shared desired outcomes, identified by Public Works through discussions with numerous groups and individuals. During our gaps analysis, Public Works evaluated disparities in water resilience throughout the County and specifically selected a focal area to address a pressing need. The CWP provides an approach for achieving these desired outcomes through collaboration and a platform for measuring progress.

Los Angeles County’s Climate Cost Challenge

Center for Climate Integrity | April 2nd, 2024

Within the first two months of 2024, the City of Los Angeles had already exceeded its average annual rainfall, receiving nearly 15 inches of rain in back-to-back deluges.

Within the first two months of 2024, the City of Los Angeles had already exceeded its average annual rainfall, receiving nearly 15 inches of rain in back-to-back deluges.1 The storms flooded roads, brought massive wind gusts, ripped down trees, and killed nine people.2 The year prior was the hottest year ever recorded, including unseasonably hot weather into the fall months in Southern California. In October 2023, a wildfire ripped through rural lands southeast of the City of Los Angeles, destroying multiple buildings and forcing approximately 4,000 people to evacuate. With climate-driven disasters in Southern California growing more intense every year, it’s more important than ever for communities to invest in a growing range of climate adaptation and resilience projects. This study is the first-ever attempt to calculate the costs of preparing for and adapting to 14 different climate impacts on municipal, county, state, and federal governments in Los Angeles County.

Los Angeles Department of Water & Power response to Mono Lake Committee Request for a Drought Emergency Regulation

California State Water Resources Control Board (SWRCB) | January 11th, 2023