The coastal area of San Diego, California, USA, has modest rainfall, runoff, and recharge. The Mediterranean climate provides an idyllic setting for residents and visitors, but water managers are challenged by the scant local water supplies and increasing population. Like other coastal areas throughout the world where the presence of saline groundwater reduces the supply of drinking water, future development of the local groundwater resources in the San Diego area of southern California is limited by the presence of saline-to-brackish groundwater in some parts of the coastal aquifer.