The Tijuana River (Spanish: Río Tijuana) is an intermittent river, 120 mi (195 km) long, near the Pacific coast of northern Baja California state in northwestern Mexico and Southern California in the western United States. The lower reaches of the river are heavily polluted with raw sewage from the city of Tijuana, Mexico.
Location The Tijuana River drains an area along the U.S.–Mexico border, flowing through Mexico for most its course then crossing the border into Southern California for its lower 5 mi (8 km) to empty into the ocean at the Tijuana River Estuary on the southern edge of San Diego. The region straddles the Mediterranean climate and semi-arid climate zones, so the Tijuana River and its tributaries often go dry in times of drought. The Tijuana River has two main tributaries. One, the Arroyo de Alamar or Rio Alamar, runs in its upper reaches in the United States as Cottonwood Creek. It runs from its source in the Laguna Mountains southwestward where it is impounded by two dams, Barrett and Morena, to supply water to the city of San Diego. Cottonwood Creek is joined by the Tecate Creek before it enters Mexico where it is known as the Arroyo de Alamar from the point where it enters Mexico to its confluence with the larger tributary, the Arroyo de las Palmas, that forms the headwaters of the Tijuana River within the city. The Arroyo de las Palmas, the main tributary of the Tijuana River, flows out of the mountains to the east into the reservoir behind the Abelardo L. Rodríguez Dam. Downstream from the Rodríguez Dam, water flows through Tijuana in a concrete channel to the international border; there it continues west through the Tijuana River Valley for a distance of about nine miles to the estuary and then to the Pacific Ocean. Its lower reaches provide the last undeveloped coast wetlands in San Diego County amidst a highly urbanized environment at the southern city limits of Imperial Beach. The river has been the subject of great concern regarding pollution, flood control, and U.S. border protection.
Description
The Tijuana River rises in the Sierra de Juárez of northern Baja California, approximately 45 mi (70 km) ENE of Ensenada. It flows WNW through Tijuana, crossing the border approximately 5 mi (8 km) from the Pacific. It flows west, just skirting the international border south of the San Ysidro section of San Diego. The lower 2 mi (3 km) of the river form the broad mud flat estuary, and the Tijuana River Estuary is a rich habitat for wildlife, including over 370 species of birds; one of these species is the Ridgway's rail. It is Southern California's largest coastal wetland. It is naturally prone to flooding during heavy rains. The Tijuana River enters the Pacific 10 mi (15 km) south of downtown San Diego at the southern city limits of Imperial Beach. The river is an intermittent river, flowing naturally only during rains. The river is impounded in Mexico southeast of Tijuana by the Abelardo L. Rodríguez Dam for drinking water and irrigation. Former Baja California Governor Milton Castellanos Everardo constructed concrete barriers along the riverbank to prevent flooding during his tenure. The United States was supposed to build a complementary system of barriers to ensure flooding waters didn't flow back into Mexico, but instead adopted a dissipator flood control plan under the direction of the San Diego City Council, supported by ecologists, which preserved the estuary, which was then designated a wildlife sanctuary. The majority of its watershed is within Mexico, between Mesa de Otay to the east, and hills to the west.
Conservation
Flooding Flooding in the Tijuana River had been a concern for both the United States and Mexico because it would lead to sewage runoff and would ultimately cause property damage to the surrounding area. In 1944, the United States-Mexico Water Treaty was signed, this dealt with "utilization of waters in the Colorado and Tijuana rivers and of the Rio Grande." This treaty appointed the International Boundary and Water Commission to handle several issues such as border sanitation. The IBWC went on to create the Tijuana River Flood Control Project in 1966 in order to create a flood control channels along the river. Mexico had completely complied by 1976 while the U.S. implementation stalled due to opposition at the local level. Despite preventive measures, flooding in 1980 caused 11 deaths and property damage in bordering cities. Flooding due to high rainfall and sewage blockage continues to be a concern that endangers surrounding areas because of the wastewater pollution found in the river.
Nature reserves The Tijuana River National Estuarine Research Reserve protects 2,293 acres (928 ha) and studies the Tijuana River Estuary. It was established as part of the National Estuarine Research Reserve system in the United States. The reserve is managed in part as a Biological Field Station by the San Diego State University (SDSU) College of Sciences, which also protects part of the estuary near the ocean within the United States. The Tijuana Slough National Wildlife Refuge is part of the San Diego National Wildlife Refuge Complex, and is also within the Estuarine Research Reserve. The Tijuana Slough Refuge protects one of southern California's largest remaining salt marshes without a road or railroad trestle running through it. Designated as a Globally Important Bird Area by the American Bird Conservancy, over 370 species of birds have been sighted on the refuge. Salmon have been recorded in the past in the river during runs.
Wastewater
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