Center for Marine Biodiversity and Conservation

Urban runoff impacts both the quantity and quality of southern California watersheds. Within highly developed watersheds, the volume of urban runoff is magnified from increased surface area of impervious substrate. Chollas Creek, a small watershed located south of downtown San Diego, has been impacted by dense population and a history of development. Its current status as an impaired water body by the California Regional Water Quality Control Board reflects, in part, the impacts of urban runoff on water quality. Though the predominant condition of southern California watersheds is dry, management to improve water quality generally focuses on the loading that results from high volume flow from storm events. This report is intended to provide a summary of dry weather data within Chollas Creek, focusing on the amount of water discharged into San Diego Bay and the contaminants that are present in the dry weather discharge. This report also highlights the value and limitations in using micro-drainage basin maps to evaluate relationship between land use, human activities, and drainage area to the quantity and quality of urban runoff from the dry season.