South Coast

Water Available for Replenishment 2018

California Department of Water Resources (DWR) | April 12th, 2018

Water conservation benefits of urban heat mitigation

Nature Portfolio (Springer Nature) | October 20th, 2017

Many cities globally are seeking strategies to counter the consequences of both a hotter and drier climate. While urban heat mitigation strategies have been sho

Many cities globally are seeking strategies to counter the consequences of both a hotter and drier climate. While urban heat mitigation strategies have been shown to have beneficial effects on health, energy consumption, and greenhouse gas emissions, their implications for water conservation have not been widely examined. Here we use a suite of satellite- supported regional climate simulations in California to show that broad implementation of cool roofs, a heat mitigation strategy, not only results in significant cooling, but can also meaningfully decrease outdoor water consumption by reducing evaporative and irrigation water demands. Irrigation water consumption across the major metropolitan areas is reduced by up to 9% and irrigation water savings per capita range from 1.8 to 15.4 gallons per day across 18 counties examined. Total water savings are found to be the highest in Los Angeles county, reaching about 83 million gallons per day. Cool roofs are a valuable solution for addressing the adaptation and mitigation challenges faced by multiple sectors in California.

Water Demand Projection Accuracy and Demand Management Trends in California Cities

American Geophysical Union (AGU) | November 21st, 2025

This study investigates the accuracy of long-term water demand projections and tracks the evolution of water demand management incentives across 61 California water suppl

This study investigates the accuracy of long-term water demand projections and tracks the evolution of water demand management incentives across 61 California water suppliers from 2000 to 2020. Through a systematic analysis of Urban Water Management Plans, we find that water suppliers consistently overestimated future demand by an average of 25% for 5-year projections and 74% for 20-year projections. This overestimation stems primarily from assumptions about per capita water demand rather than population growth estimates. While suppliers generally projected stable or increasing per capita demand, actual water demand per capita declined by 1.9% annually between 2000 and 2020, leading to a decoupling of water demand from population growth. Concurrently, we document a substantial increase in water demand management incentives, with non-voluntary regulations emerging as the dominant demand management approach by 2020, largely driven by state policies like the Model Water Efficient Landscape Ordinance and California Green Building Standards. Demand management efforts have evolved from primarily indoor and educational initiatives toward outdoor-focused non-voluntary regulations and rebates. This shift appears closely linked to the reduction in per capita demand that suppliers failed to fully capture in their water demand projections. Our findings underscore the importance of incorporating dynamic conservation trends into demand projections and suggest that suppliers should develop more sophisticated forecasting methods that account for the continuing evolution of water efficiency incentives. This research provides valuable insights for water resource planners seeking to improve the accuracy of water demand projections in an era of increasing conservation and climate uncertainty.

Water Distribution System Efficiency: An Essential or Neglected Part of the Water Conservation Strategy for Los Angeles County Water Retailers?

University of California, Los Angeles (UCLA) | November 2nd, 2015

The water governance system in Los Angeles County is complex and fragmented. Potable water supply in metropolitan Los Angeles County relies on over 100 water retailers, b

The water governance system in Los Angeles County is complex and fragmented. Potable water supply in metropolitan Los Angeles County relies on over 100 water retailers, both public and private. It is unclear how the current system with many small water retailers will succeed in promoting integrated water resource management. Among other changes, there will need to be a shifting of water supply sources from predominantly imported to more local resources through conservation, recycled water usage, stormwater capture and groundwater management. The institutional capacity of water retailers to instigate this transition will depend heavily on their capacity to maintain reliable water deliveries without significant losses from leakage and failing infrastructure. Additionally, with drought conditions prevalent in eleven of the last fourteen years in California, and increasing evidence of climate change impacts on all water resources in California, it is crucial that water retailers minimize water losses through their distribution systems to match the increasingly stringent conservation efforts required of their customers, and to efficiently utilize scarce supplies.  Until this year, existing regulations for water agencies in California only requested information about system losses for potable water systems with more than 3000 connections. These numbers were reported through Urban Water Management Plans every five years. However, loss estimates through breaks and leaks have not been separated out from other non-revenue uses of water. To date, the most effective efforts to monitor water losses in California are voluntary and limited to members of the California Urban Water Conservation Council. To understand water distribution efficiency in urban Los Angeles County, we developed a questionnaire regarding leakage monitoring, system-wide water losses, and the implementation of pre-emptive best management practices. We surveyed 10 of the approximate total of 100 water retailers. The sample was representative of retailers of many types, sizes, and geographical locations in metropolitan Los Angeles and divided into tiers of size (small, mid-sized and large) based on the number of connections served. The survey questionnaire also addressed other metrics including per capita water consumption, leakage volumes, water loss estimation methodology, water loss estimates and infrastructure monitoring and replacement. The survey indicated several findings. First, the percentage of water loss due to breaks and leaks, though possibly misrepresentative, is still a widely used metric to measure water losses. Sixty percent of the agencies sampled still monitor only ‘unaccounted for water’ and not ‘real losses’. Retailers that do measure real losses reported them to be between 3-4% of total water supplied, which is an improbably low compared to international estimates as elaborated in the literature review section. Different water retailers were divided on the efficacy of leak detection technologies, which demands more education on available leak detection technology and their usage.  Larger retailers reported greater use of most of the best management practices addressed by our survey to maintain storage and distribution systems. Most small retailers did not report prioritizing adoption and implementation of best management practices to minimize water loss. Also, small Mutual Water Companies that we contacted did not have information on distribution water losses available publicly. To improve water efficiency, small retailers could pool resources and expertise to better detect, monitor and reduce distribution water losses. Investor-owned utilities and special water districts serve a large customer base, but as a group, they were least responsive of all the sample water retailers we contacted. In summary, California water regulations should aim at recommending crucial best management practices, ensuring accurate and verifiable water loss monitoring and prescribing an effective water loss metric and maximum acceptable standard as a roadmap for water retailers 

Water from the Colorado River

Metropolitan Water District of Southern California (MWD) | July 1st, 1931

It is the purpose of this booklet to outline the Boulder Canyon Dam project on the Colorado River and the Metropolitan Aqueduct. Furthermore, it seems pertinent to indica

It is the purpose of this booklet to outline the Boulder Canyon Dam project on the Colorado River and the Metropolitan Aqueduct. Furthermore, it seems pertinent to indicate the extent of the population, industrial and agricultural resources of the Metropolitan area, which stand behind and urgently require Colorado River development.

Water Partnerships between Cities and Farms in Southern California and the San Joaquin Valley

Public Policy Institute of California (PPIC) | October 29th, 2020

The San Joaquin Valley and urban Southern California are worlds apart in many ways. Yet each face growing water challenges and a shared interest in ensuring reliable, aff

The San Joaquin Valley and urban Southern California are worlds apart in many ways. Yet each face growing water challenges and a shared interest in ensuring reliable, affordable water supplies to safeguard their people and economies. Both regions’ water futures could be more secure if they take advantage of shared water infrastructure to jointly develop and manage some water supplies.  Increasing climate volatility is heightening concerns about droughts of the future. And two major shifts in California’s water landscape have generated new opportunities for collaboration between urban and agricultural interests. For urban areas, significant declines in water demand have reduced pressure on supplies during normal and wet years for many agencies, making reliability for future droughts the primary concern. For the overdrafted San Joaquin Valley, the requirement to manage groundwater sustainably has heightened interest in expanding water supplies and underground storage.  Partnerships between Southern California cities and San Joaquin Valley farms could help alleviate groundwater overdraft in the valley while building drought resilience in Southern California. More flexible supplies can help agencies adapt to changing conditions. By coordinating the location of infrastructure investments, agencies can use partnerships to bring the water where and when it is most needed, at least cost.  This report explores a variety of solutions that could benefit both regions. For the San Joaquin Valley, we look for ways to augment water supplies to ease the transition to groundwater sustainability, while for Southern California we explore options that would increase cities’ ability to deal effectively with extended droughts. By diversifying water supplies, building connections to share water more flexibly, and preparing for the extreme events to come, such partnerships would support Governor Newsom’s Water Resilience Portfolio, and pave the way for a shared effort to make the state’s water system more resilient to a changing climate. 

Water Quality Control Plan for the Coastal Watersheds of Los Angeles and Ventura Counties

Los Angeles Regional Water Quality Control Board (LARWQCB) | September 11th, 2014

The Los Angeles Regional Board's Basin Plan is designed to preserve and enhance water quality and protect the beneficial uses of all regional waters. Specifically, the Ba

The Los Angeles Regional Board's Basin Plan is designed to preserve and enhance water quality and protect the beneficial uses of all regional waters. Specifically, the Basin Plan (i) designates beneficial uses for surface and ground waters, (ii) sets narrative and numerical objectives that must be attained or maintained to protect the designated beneficial uses and conform to the state's antidegradation policy, and (iii) describes implementation programs to protect all waters in the Region. In addition, the Basin Plan incorporates (by reference) all applicable State and Regional Board plans and policies and other pertinent water quality policies and regulations. Those of other agencies are referenced in appropriate sections throughout the Basin Plan. The Basin Plan is a resource for the Regional Board and others who use water and/or discharge wastewater in the Los Angeles Region. Other agencies and organizations involved in environmental permitting and resource management activities also use the Basin Plan. Finally the Basin Plan provides valuable information to the public about local water quality issues. The Basin Plan is reviewed and updated as necessary. Following adoption by the Regional Board, the Basin Plan and subsequent amendments are subject to approval by the State Board, the State Office of Administrative Law (OAL), and the United States Environmental Protection Agency (USEPA).

Water Quality Control Plan for the San Diego region

San Diego Regional Water Quality Control Board (SDRWQCB) | July 26th, 2012

The San Diego Regional Board's Basin Plan is designed to preserve and enhance water quality and protect the beneficial uses of all regional waters. Specifically, the Basi

The San Diego Regional Board's Basin Plan is designed to preserve and enhance water quality and protect the beneficial uses of all regional waters. Specifically, the Basin Plan: (1) designates beneficial uses for surface and ground waters; (2) sets narrative and numerical objectives that must be attained or maintained to protect the designated beneficial uses and conform to the state's antidegradation policy; (3) describes implementation programs to protect the beneficial uses of all waters in the Region; and (4) describes surveillance and monitoring activities to evaluate the effectiveness of the Basin Plan [California Water Code sections 13240 thru 13244, and section 13050(j)]. Additionally, the Basin Plan incorporates by reference all applicable State and Regional Board plans and policies. The goal of the Regional Board is to achieve a balance between the competing needs of mankind for water of varying quality. Often times the constituents and quality of water needed to protect various beneficial uses will be different. The Basin Plan is the Regional Board's plan for achieving the balance between competing uses of surface and ground waters in the San Diego Region. Accordingly, this Basin Plan establishes or designates beneficial uses and water quality objectives for all the ground and surface waters of the Region. Beneficial uses are the uses of water necessary for the survival and well being of man, plants and wildlife. These uses of water serve to promote the tangible and intangible economic, social, and environmental goals of mankind. Water quality objectives are the levels of water quality constituents or characteristics which must be met to protect the beneficial uses. This Basin Plan also establishes an implementation program describing the actions by the Regional Board and others that are necessary to achieve and maintain the designated beneficial uses and water quality objectives of the Region's waters.

Water Quality Control Plan for the Santa Ana Region

Santa Ana Regional Water Quality Control Board (SARWQCB) | February 11th, 2016

This document is the Basin Plan for the Santa Ana Region. The Santa Ana Regions includes the upper and lower Santa Ana River watersheds, the San Jacinto River watershed,

This document is the Basin Plan for the Santa Ana Region. The Santa Ana Regions includes the upper and lower Santa Ana River watersheds, the San Jacinto River watershed, and several other small drainage areas. The Santa Ana Region covers parts of southwestern San Bernardino County, western Riverside County, and northwestern Orange County. The Basin Plan for the Santa Ana Region is more than just a collection of water quality goals and policies, descriptions of conditions, and discussions of solutions. It is also the basis for the Regional Board’s regulatory programs. The Basin Plan establishes water quality standards for the ground and surface waters of the region. The term “water quality standards,” as used in the federal Clean Water Act, includes both the beneficial uses of specific waterbodies and the levels of quality which must be met and maintained to protect those uses. The Basin Plan includes an implementation plan describing the actions by the Regional Board and others that are necessary to achieve and maintain the water quality standards. The Regional Board regulates waste discharges to minimize and control their effects on the quality of the region’s ground and surface water. Permits are issued under a number of programs and authorities. The terms and conditions of these discharge permits are enforced through a variety of technical, administrative, and legal means. Water quality problems in the region are listed in the Basin Plan, along with the causes, where they are known. For waterbodies with quality below the levels necessary to allow all the beneficial uses of the water to be met, plans for improving water quality are included. In some cases, it has been necessary for the Regional Board to completely prohibit the discharge of certain materials. Some types of discharges are prohibited in specific areas. Details on these prohibitions also appear in the Basin Plan.

Water quality for agriculture

Food and Agriculture Organization of the United Nations (FAO) | July 15th, 1985