The WRD manages groundwater for nearly four million residents in 43 cities of southern Los Angeles County . The 420 square mile service area uses about 250,000 acre-feet of groundwater per year, which equates to nearly 40% of the total demand for water. The WRD ensures that a reliable supply of high quality groundwater is available through its clean water projects, water supply programs, and effective management principles. Visit the Projects and Programs section of this site to learn more about the WRD's individual water projects and programs.