The Tijuana River rises in the Sierra de Juárez of northern Baja California, approximately 45 miles (70 km) east-northeast of Ensenada, and flows to the Pacific about 10 miles (15 km) south of downtown San Diego at the southern city limits of Imperial Beach, California. The lower 2 miles (3 km) of the river form the Tijuana River Estuary, a rich habitat for wildlife and the largest coastal wetland in Southern California. Imperial Beach is a residential community and the southernmost city in California.
The river is intermittent, flowing naturally only during rains. The river is impounded in Mexico southeast of Tijuana for drinking water and irrigation. Concrete barriers were constructed along the riverbank in Mexico to prevent flooding, and the United States was supposed to build a complementary system, but instead adopted a dissipator flood control plan that preserved the estuary which was then designated a wildlife sanctuary.
The Tijuana River National Estuarine Research Reserve protects the natural and cultural resources of the Tijuana River Estuary by focusing on research and education with compatible recreation and resource use. The Reserve encompasses beach, dune, mudflat, salt marsh, riparian, coastal sage scrub, and upland habitats, all surrounded by the growing cities of Tijuana, Imperial Beach, and San Diego. Critical issues confronted by the Reserve include habitat conservation and restoration, endangered species management, management of the wastewater from Mexico, sediment management, and the integration of recreation. The Tijuana River National Estuarine Research Reserve is a partnership between federal and state agencies including the National Oceanic and Atmospheric Administration, California State Parks, and the U.S. Fish & Wildlife Service. Read more here and here. Explore more of the Tijuana River estuary here: