Southern California Coastal water resource subregion

Southern California Coastal water resource subregion (HUC 1807) is one of 10 hydrologic subregions within the California water resource region and is one of 222 water resource subregions in the United States hydrologic unit system. The Southern California coastal subregion, sometimes called the South Coast Hydrologic Subregion, is a second-level subdivision^[1] covering is approximately 11,000 sq mi (28,000 km²; 7,000,000-acre) and extends from Rincon Creek on the north to the international border with Mexico on the south.^[2] The South Coast Hydrologic Subregion is composed of three third-level hydrological units. The federally-defined Southern California Coastal water resource subregion equates roughly with the state-designated South Coast hydrologic region. Per a USGS report of 1976, "Water deficiency is prevalent in the South Coastal subregion."^[3] By 1955 the region was found to be experiencing measurable levels of saltwater intrusion due to overdrawn aquifers and several wells were abandoned as a consequence.^[3] Part of the solution was injecting Colorado River water from the aqueduct into local wells to defend against the salted water, a practice called artificial recharge.^[3]