Loa River
Encyclopedia
The Loa River is a U-shaped river in Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

's northern Antofagasta Region
Antofagasta Region
The II Antofagasta Region is one of Chile's fifteen first-order administrative divisions. It comprises three provinces, Antofagasta, El Loa and Tocopilla...

. At 440 km long it is the country's longest river and the main watercourse in the Atacama Desert
Atacama Desert
The Atacama Desert is a plateau in South America, covering a strip of land on the Pacific coast, west of the Andes mountains. It is, according to NASA, National Geographic and many other publications, the driest desert in the world...

.

Course

The Loa's sources are located on Andean
Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...

 mountain slopes at the foot of Miño Volcano
Miño Volcano
Miño Volcano is a symmetrical cone-shaped stratovolcano located in El Loa Province, Antofagasta Region, Chile. It lies a few kilometres northwest of Aucanquilcha volcano and at its foot originates Loa River. The major settlement in its vicinity is Ollagüe....

. The upper Loa basin is flanked on the west by a ridge with elevations that reach above 4,500 m, whereas to the east lies a volcanic chain, which separates it from endorrheic basins as that of Salar de Ascotán.

The river flows south on an elevated plateau, for about 150 km, to the oasis
Oasis
In geography, an oasis or cienega is an isolated area of vegetation in a desert, typically surrounding a spring or similar water source...

 of Chiu Chiu (CHEE-oo CHEE-oo). The upper courses of the river are at a considerable elevation above sea level and receive a large volume of water from the Andes, mainly of two major tributaries: San Pedro de Inacaliri River and Salado River. The former joins the Loa near Conchi reservoir
Reservoir
A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

 and the latter about 3 km south of Chiu Chiu. The water of its upper course and tributaries is fresh. However the lower course, as in all the rivers of this region becomes brackish.

From Chiu Chiu, the Loa flows west and north in a great curve to Quillagua
Quillagua
Quillagua is an oasis in the Tocopilla Province, in the Antofagasta Region of northern Chile. It is a part of the commune of María Elena. The Loa River is crossed by the Pan-American Highway in this area....

 (kee-YAH-gwah). After flowing for 115 km in this portion of its course and having run through the city of Calama
Calama, Chile
Calama is a city and commune in the Atacama Desert in northern Chile. It is the capital of El Loa Province, part of the Antofagasta Region. Calama is one of the driest cities in the world with average annual precipitation of just . The River Loa, Chile's longest, flows through the city...

, the Loa receives the waters of San Salvador River at the locality of Chacance. Thence the river flows north for about 80 km to Quillagua.

From Quillagua, its dry channel turns westward again and marks the border between the regions of Tarapacá
Tarapacá Region
The I Tarapacá Region is one of Chile's 15 first order administrative divisions. It borders the Chilean Arica and Parinacota Region to the north, Bolivia's Oruro Department on the east, the Antofagasta Region on the south and the Pacific Ocean on the west. The port city of Iquique The I Tarapacá...

 and Antofagasta
Antofagasta Region
The II Antofagasta Region is one of Chile's fifteen first-order administrative divisions. It comprises three provinces, Antofagasta, El Loa and Tocopilla...

. Along its lower course, the Loa flows through a 500-m-deep canyon, which crosses the Chilean Coastal Range. The river reaches the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

 in lat. 21° 26' S., a few miles south of the old port of Huanillos (Wan-EE-yōs).

The hydrologic regime of the river basin is rain-dominated. The increase of its water volume occurs mainly in January and February, as a consequence of the phenomenon known locally as Bolivian Winter.

History

Its banks have been inhabited from early times. Evidence of this is the notable number of geoglyph
Geoglyph
A geoglyph is a large design or motif produced on the ground and typically formed by clastic rocks or similarly durable elements of the geography, such as stones, stone fragments, gravel, or earth...

s, petroglyph
Petroglyph
Petroglyphs are pictogram and logogram images created by removing part of a rock surface by incising, picking, carving, and abrading. Outside North America, scholars often use terms such as "carving", "engraving", or other descriptions of the technique to refer to such images...

s and pictographs that are found along its course and in its upper basin.

Another indication of its rich past is the Pukará de Lasana.

Bridges

To the south of Conchi reservoir, the river is spanned by an old railroad bridge, which is no longer used by the Ferrocarril de Antofagasta a Bolivia
Ferrocarril de Antofagasta a Bolivia
The Ferrocarril de Antofagasta a Bolivia is a private railway operating in the northern provinces of Chile. It is notable in that it was one of the earliest railways built to the gauge of , with a route that climbed from sea level to over , while handling goods traffic totaling near 2 million tons...

, however it still holds the notability of being, at 104 m, one of the highest bridges in Chile.

Needs

This river supplies many towns with water used to raise shrimp. Lately mining companies have been polluting this river making the water unusable.
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