The Loa River (Spanish: Río Loa) is a U-shaped river in Chile's northern
Antofagasta Region
The Antofagasta Region (, ) is one of Chile's Administrative divisions of Chile, sixteen first-order administrative divisions. Being the second-largest region of Chile in area, it comprises three provinces, Antofagasta Province, Antofagasta, El ...
. At long, it is the country's longest river and the main watercourse in the
Atacama Desert
The Atacama Desert () is a desert plateau located on the Pacific Ocean, Pacific coast of South America, in the north of Chile. Stretching over a strip of land west of the Andes Mountains, it covers an area of , which increases to if the barre ...
.
Course
The Loa's sources are located on
Andean
The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long and wide (widest between 18°S ...
mountain slopes at the foot of
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 vicinit ...
. The upper Loa basin is flanked on the west by a ridge with elevations that reach above , whereas to the east lies a volcanic chain (including
Aucanquilcha
Aucanquilcha is a massive stratovolcano located in the Antofagasta Region of northern Chile, just west of the border with Bolivia and within the Alto Loa National Reserve. Part of the Central Volcanic Zone of the Andes, the stratovolcano has the ...
,
Palpana
Palpana (from , ram) is a volcano in the Andes of Chile. It has a summit elevation of .
It is part of the dividing range between Upper Loa River basin and Salar de Ascotán basin. Together with Inacaliri and Azufre, it forms a long volcanic ch ...
and San Pedro), which separates it from endorheic basins as that of
Salar de Ascotán
Salar de Ascotán, also known as Salar de Cebollar, is a salt flat in northern Chile. Its drainage basin is and is shared with Bolivia. The basin is bordered on the north by the Salar de Carcote basin, on the east by small endorheic basins, inc ...
.
The river flows south on an elevated plateau from to altitude, part of the
Alto Loa National Reserve
Alto Loa National Reserve is a protected area located in the Provinces of Chile, province of El Loa, Antofagasta Region, Antofagasta Regions of Chile, region, Chile. Announced in 2002 and created in 2005, it is Chile's largest natural reserve.
...
, for about , to the
oasis
In ecology, an oasis (; : oases ) is a fertile area of a desert or semi-desert environmentChiu Chiu. The upper courses of the river are at a considerable elevation above sea level and receive water from the Andes, mainly of two major tributaries:
San Pedro de Inacaliri River
San Pedro de Inacaliri River, or called simply San Pedro River, is a List of rivers in Chile, river of Chile located in El Loa Province, Antofagasta Region. It begins at the confluence of the rivers Silala River, Silala and ''Cajón'', at an elev ...
and Salado River. The former joins the Loa near Conchi dam and reservoir and the latter about 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 is an oasis at about altitude 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.
According to the ''Di ...
. After flowing west for in this portion of its course and having run through the city of Calama, the Loa receives the waters of San Salvador River at the locality of ''Chacance''. Thence the river flows north for about to Quillagua at about altitude. The Sloman dam is on this section.
From Quillagua, its partly dry channel turns westward again and marks the border between the regions of
Tarapacá
San Lorenzo de Tarapacá, also known simply as Tarapacá, is a town in the region of the same name in Chile.
History
The town has likely been inhabited since the 12th century, when it formed part of the Inca trail. When Spanish explorer Diego ...
and
Antofagasta
Antofagasta () is a port city in northern Chile, about north of Santiago. It is the capital of Antofagasta Province and Antofagasta Region. According to the 2015 census, the city has a population of 402,669.
Once claimed by Bolivia follo ...
. Along its lower course, the Loa flows through a canyon, which crosses the
Chilean Coastal Range
The Chilean Coastal Range () is a mountain range that runs from north to south along the Pacific coast of South America parallel to the Andean Mountains, extending from Morro de Arica in the north to Taitao Peninsula, where it ends at the Chi ...
. The river reaches the Pacific Ocean in lat. 21° 26' S., a few miles south of the old port of Huanillos.
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
Bolivian may refer to:
* Something of, or related to, Bolivia
** Bolivian people
** Demographics of Bolivia
** Culture of Bolivia
Bolivia is a country in South America, bordered by Brazil to the north and east, Paraguay and Argentina to the ...
.
History
Its banks have been inhabited from early times. Evidence of this is the notable number of
geoglyph
A geoglyph is a large design or motif – generally longer than – produced on the ground by durable elements of the landscape, such as stones, stone fragments, gravel, or earth. A positive geoglyph is formed by the arrangement and alignment ...
s,
petroglyph
A petroglyph is an image created by removing part of a rock surface by incising, picking, carving, or abrading, as a form of rock art. Outside North America, scholars often use terms such as "carving", "engraving", or other descriptions ...
s and
pictograph
A pictogram (also pictogramme, pictograph, or simply picto) is a graphical symbol that conveys meaning through its visual resemblance to a physical object. Pictograms are used in systems of writing and visual communication. A pictography is a wri ...
s that are found along its course and in its upper basin.
Another indication of its rich past is the
Pukará de Lasana
Lasana is a small village located northeast of the city of Calama in the Calama province of Chile's northern Antofagasta Region. It sits along the banks of the Loa River.
Pukará de Lasana, (Quechua ''pukara'' fortress), a pre-Columbian fortres ...
.
Bridges
To the south of Conchi reservoir, the river is spanned by the
Conchi Viaduct
The Conchi viaduct, or Loa viaduct, is located on the Loa River in Chile, from Calama. It was built to carry part of the Ferrocarril de Antofagasta a Bolivia
The Ferrocarril de Antofagasta a Bolivia (British company name: Antofagasta (Ch ...
, an old railroad bridge. It is no longer used by the
Ferrocarril de Antofagasta a Bolivia
The Ferrocarril de Antofagasta a Bolivia (British company name: Antofagasta (Chili) & Bolivia Railway or FCAB for short) is a private railway operating in the northern provinces of Chile. It is notable in that it was one of the earliest rail ...
, however it still holds the notability of being, at , one of the highest bridges in Chile.Conchi Bridge
Needs
This river supplies many towns with water used to raise shrimp. Lately, mining companies have been polluting this river, making the water unusable.