Rio Alamar or Arroyo de Alamar is a river mainly in northern

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

Mexico Mexico ( Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guate ...

with a small portion in

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the ...

, United States. The stream is formed by the confluence of Cottonwood Creek and

Tecate Creek Tecate Creek is a stream in northern Baja California, Mexico with its headwaters in southern San Diego County, California in the United States. It begins along the Tecate Divide in the In-Ko-Pah Mountains, near Live Oak Springs. The upper reaches ...

a short distance north of the

Mexico–United States border The Mexico–United States border ( es, frontera Estados Unidos–México) is an international border separating Mexico and the United States, extending from the Pacific Ocean in the west to the Gulf of Mexico in the east. The border trav ...

. It flows generally west for about through the

San Ysidro Mountains The San Ysidro Mountains are a mountain range in southern San Diego County, California and Baja California, Mexico. The mountains are a rugged coastal foothill range of the Peninsular Ranges system. Major peaks include the highest summit of the r ...

and the

Tijuana Tijuana ( ,"Tijuana"
(US) and < ...

urban area before joining with the

Arroyo de las Palmas Arroyo often refers to: * Arroyo (creek), an intermittently dry creek Arroyo may also refer to: People * Arroyo (surname) Places United States ;California * Arroyo Burro Beach, a public beach park in Santa Barbara County, California * Arroyo ...

in central Tijuana, to form the

Tijuana River , name_etymology = , image = Presa Tij 1.jpg , image_size = , image_caption = Dam on the Tijuana River in Mexico. , map = Tijuana River Basin.svg , map_size = 250 , map_caption ...

See also