Loa River

The Loa is a U-shaped river in Chile's northern Antofagasta region. It is the longest river of the country and the main river in the Atacama Desert.
Geography.
The Loa river has a length of , and a drainage basin with an area of approximately .
Course.
The Loa river starts on the Andean mountain slopes at the base of the Miño volcano near the Bolivian border, at an elevation of about , in the "comuna" of Ollagüe, Calama, Antofagasta.
The river flows south, for about , to the oasis of San Francisco de Chiu Chiu or simply "Chiu Chiu". Two left tributaries joints the Lao river in this part the riverː 
From Chiu Chiu, the Loa flows to the west, running through the city of Calama. The San Salvador river joints the Loa in this part of course as its only important right tributary.
Then the Loa flows north for about to Quillagua, an oasis in the "comuna" of María Elena, Tocopilla province in the Antofagasta region of northern Chile. The Loa is crossed by the Pan-American Highway in this area.
From Quillagua, the river turns westward again and marks the border between the regions of Tarapacá and Antofagasta. Finally, the Loa flows in the Pacific Ocean.
Main tributaries.
Because the Loa river flows throug a very arid region, a desert, there are very few permanent tributaries; they areː