South Coast

2022 Drinking Water Needs Assessment

California State Water Resources Control Board (SWRCB) | April 30th, 2022

The Needs Assessment is comprised of Risk, Affordability, and Cost Assessment components. Enhancement of the 2022 Needs Assessment consisted of internal workgroup recomme

The Needs Assessment is comprised of Risk, Affordability, and Cost Assessment components. Enhancement of the 2022 Needs Assessment consisted of internal workgroup recommendations and a public workshop in February 2022, all of which were detailed in a publicly available white paper. The public feedback was incorporated into the final methodology and results. Three different water system types: public water systems, state small water systems and domestic wells, are analyzed within the 2022 Needs Assessment. Different methodologies were developed for these system types based on data availability and reliability.

2022-2023 Engineer’s Report on the Groundwater Conditions, Water Supply and Basin Utilization in the Orange County Water District

Orange County Water District (OCWD) | February 21st, 2024

Total water demands within Orange County Water District (OCWD) were 351,719 acre feet (AF) for the 2022-23 water year (beginning on July 1, 2022 and ending on June 30, 20

Total water demands within Orange County Water District (OCWD) were 351,719 acre feet (AF) for the 2022-23 water year (beginning on July 1, 2022 and ending on June 30, 2023). Groundwater production for the water year totaled 245,210 AF including any available In-Lieu Program water. The use of supplemental water in OCWD’s service area during the 2022-23 water year totaled 107,723 AF of which 88,441 AF resulted from the direct use by water agencies and districts and 19,282 AF were used for the purpose of groundwater basin replenishment and maintenance of seawater intrusion control barriers. For the water year which ended on June 30, 2023, the “annual overdraft” (annual basin storage decrease without supplemental replenishment water) was 52,250 AF. The accumulated overdraft decreased from 258,000 AF on June 30, 2022 to 189,000 AF on June 30, 2023. Precipitation within the groundwater basin was one hundred fifty eight percent of the long-term average during this water year, totaling 21.12 inches. Based on the groundwater basin conditions for the water year ending on June 30, 2023, OCWD may purchase up to 123,000 AF of water for groundwater replenishment during the ensuing water year, beginning on July 1, 2024, pursuant to the District Act.

2023 Annual Water Supply and Demand Assessment Summary Report

California Department of Water Resources (DWR) | September 30th, 2023

This annual report summarizes the Department of Water Resources’ (DWR’s) review of Urban Water Suppliers’ Annual Water Shortage Assessment Reports (Annual Shortage

This annual report summarizes the Department of Water Resources’ (DWR’s) review of Urban Water Suppliers’ Annual Water Shortage Assessment Reports (Annual Shortage Reports) for the State Water Resources Control Board (State Water Board). As directed by the California Water Code (CWC) §10644(c)(1)(B), this summary report includes water shortage information at the supplier level, as well as regional and statewide analyses of water supply conditions.

2023 Drinking Water Needs Assessment

California State Water Resources Control Board (SWRCB) | April 30th, 2023

The Needs Assessment is comprised of four core components: the Failing Water System List (Failing list), the Risk Assessment, the Cost Assessment, and the Affordability A

The Needs Assessment is comprised of four core components: the Failing Water System List (Failing list), the Risk Assessment, the Cost Assessment, and the Affordability Assessment. Public input that the State Water Board received via workshops held in 2022 and February 2023 helped improve the 2023 Needs Assessment.

2023 Water Resilience Portfolio Progress Report

California Natural Resources Agency (CNRA) | October 31st, 2023

2024 Annual Water Supply and Demand Assessment Summary Report

California Department of Water Resources (DWR) | October 1st, 2024

This report summarizes the Department of Water Resources’ (DWR’s) review of Urban Water Suppliers’ Annual Water Shortage Assessment Reports (Annual Shortage Reports

This report summarizes the Department of Water Resources’ (DWR’s) review of Urban Water Suppliers’ Annual Water Shortage Assessment Reports (Annual Shortage Reports) for the State Water Resources Control Board (State Water Board). As directed by the California Water Code (CWC) §10644(c)(1)(B), this summary report includes water shortage information at the supplier level, as well as regional and statewide analyses of water supply conditions.

2025 Agricultural Water Management Plan Guidebook (Draft)

California Department of Water Resources (DWR) | July 23rd, 2025

The 2025 Agricultural Water Management Plan Guidebook (Guidebook) was prepared by DWR to assist agricultural water suppliers in understanding and complying with the requi

The 2025 Agricultural Water Management Plan Guidebook (Guidebook) was prepared by DWR to assist agricultural water suppliers in understanding and complying with the requirements of the Agricultural Water Management Planning Act (Division 6, Part 2.8 of the California Water Code), the Agricultural Water Measurement Regulation (Title 23, Division 2, Chapter 5.1, Article 2 of the California Code of Regulations), and AB 1668 Water Management Planning (Friedman, Statute of 2018). This Guidebook is intended to clearly identify information and elements required by the California Water Code (Water Code), provide guidance on how Agricultural Water Suppliers can address these requirements, and identify potential additional information Agricultural Water Suppliers can include in order to develop plans that are useful for their own operations and management and to improve long-term system reliability. This Guidebook also describes how Water Conservation Plans (WCPs) submitted to the United States Bureau of Reclamation (USBR), and Urban Water Management Plans (UWMPs) submitted to DWR, can be supplemented to satisfy the Water Code and Agricultural Water Measurement Regulation requirements.

21st century California drought risk linked to model fidelity of the El Niño teleconnection

Nature Portfolio (Springer Nature) | September 3rd, 2018

Greenhouse gas-induced climate change is expected to lead to negative hydrological impacts for southwestern North America, including California (CA). This includes a decr

Greenhouse gas-induced climate change is expected to lead to negative hydrological impacts for southwestern North America, including California (CA). This includes a decrease in the amount and frequency of precipitation, reductions in Sierra snow pack, and an increase in evapotranspiration, all of which imply a decline in surface water availability, and an increase in drought and stress on water resources. However, a recent study showed the importance of tropical Pacific sea surface temperature (SST) warming and an El Niño Southern Oscillation (ENSO)-like teleconnection in driving an increase in CA precipitation through the 21st century, particularly during winter (DJF). Here, we extend this prior work and show wetter (drier) CA conditions, based on several drought metrics, are associated with an El Niño (La Niña)-like SST pattern. Models that better simulate the observed ENSO-CA precipitation teleconnection also better simulate the ENSO-CA drought relationships, and yield negligible change in the risk of 21st century CA drought, primarily due to wetting during winter. Seasonally, however, CA drought risk is projected to increase during the non-winter months, particularly in the models that poorly simulate the observed teleconnection. Thus, future projections of CA drought are dependent on model fidelity of the El Niño teleconnection. As opposed to focusing on adapting to less water, models that better simulate the teleconnection imply adaptation measures focused on smoothing seasonal differences for affected agricultural, terrestrial, and aquatic systems, as well as effectively capturing enhanced winter runoff.

25th Annual Report on Achievements in Conservation, Recycling & Groundwater Recharge

Metropolitan Water District of Southern California (MWD) | January 29th, 2025

Southern Californians have reduced their per person potable water use by 45% since 1990, a decline driven by Metropolitan’s nearly $1 billion investment in conservation

Southern Californians have reduced their per person potable water use by 45% since 1990, a decline driven by Metropolitan’s nearly $1 billion investment in conservation rebates and programs, along with the region’s commitment to embracing a conservation ethic.

A Basin-Scale Approach to Estimating Recharge in the Desert: Anza-Cahuilla Groundwater Basin, CA

American Water Resources Association (AWRA) | November 2nd, 2021

The Anza-Cahuilla groundwater basin located mainly in the semi-arid headwaters of the Santa Margarita River watershed in southern California is the principle source of g

The Anza-Cahuilla groundwater basin located mainly in the semi-arid headwaters of the Santa Margarita River watershed in southern California is the principle source of groundwater for a rural disadvantaged community and two Native American Tribes, the Ramona Band of Cahuilla and the Cahuilla. Groundwater in the study area is derived entirely from precipitation and managing groundwater sustainably requires an accurate assessment of the water balance components, yet long-term estimates do not exist. Demand for groundwater in the region has increased and groundwater quality has decreased due to population growth and increased irrigated cropland. To characterize monthly long-term natural recharge and runoff estimates, a physically-based water balance model (Basin Characterization Model) was locally calibrated and validated using nearby streamgages and published estimates of climatic and hydrologic variables. The average modeled annual recharge and runoff from 1981 to 2010 was 5.4 × 106 and 1.2 × 107 m3, respectively, for the study area. Recharge and runoff do not reliably occur in large amounts every year and recharge rarely occurs in the groundwater basin footprint. These long-term estimates can be used by water managers, stakeholders, and Native American Tribes to develop plans for sustainable management of future water resources, and as inputs to a three-dimensional groundwater model.