Community water systems are the fundamental building blocks of California’s drinking water supply. However, who governs these systems — and how they are managed — has a direct impact on whether communities have access to safe, affordable, and reliable water, as well as their ability to adapt to drought and climate change. Developed in collaboration with UC Agriculture and Natural Resources, The 2025 Southern California Community Water Systems Atlas expands the scope of earlier UCLA Luskin Center for Innovation studies to cover not just Los Angeles County, but 663 systems across six counties: Los Angeles, Kern, Orange, Riverside, San Bernardino, and Ventura. Together, these utilities serve 40 percent of California’s population. The report and companion mapping tool provide the most comprehensive public resource on water systems, shedding light on disparities in water quality, affordability, governance, and climate resilience.