Lake Musters and Lake Colhue Huapi
Encyclopedia
Lake Musters and lake Colhué Huapi (45°25′S 69°11′W, 260 m) form the terminal stage of the Senguerr river
Senguerr River
The Senguerr River is a river of the Argentine province of Chubut. It begins its journey from the system of glacial lakes La Plata and Fontana in the Andes Mountains....

 endorheic basin, located in the patagonic
Patagonia
Patagonia is a region located in Argentina and Chile, integrating the southernmost section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the cordillera to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean...

 central region of Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

 in the south of Chubut
Chubut Province
Chubut a province in the southern part of Argentina situated between the 42nd parallel south and the 46th parallel south , the Andes range separating Argentina from Chile, and the Atlantic ocean...

 province. Closest populated area is Sarmiento
Sarmiento, Chubut
Sarmiento is a town in the province of Chubut, Argentina. It has about 8,000 inhabitants as per the , and is the head town of the department of the same name. It is located on the so-called Central Corridor of Patagonia, in a fertile valley amidst an otherwise arid region, 140 km west from...

, a 8,000 inhabitant former Welsh immigrants colony.

Inflow

The basin lakes are fed mainly by the eastward running Senguerr river which begins its journey in the glacial lakes La Plata and Fontana in the Andes Mountains The inflow ranges from 35 to 54m³/sec and varies seasonally and yearly greatly.

Outflow

Both lakes suffer naturally of a severe evaporation
Evaporation
Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....

 process in the dry patagonian environment by means of strong winds action and solar radiation. In shallow Colhué Huapi evaporation is much increased. In past decades, when excessive inflows did take place, water discharged to the birth branches of Chico river
Chico River
-References:*...

 and eventually reached Chubut river
Chubut River
The Chubut River is located in the Patagonia region of southern Argentina. Its name comes from the Tehuelche word chupat, which means "transparent". The Argentine Chubut Province, through which the river flows, is named after it...

. This occasional process last happened in 1939, since then Chico river is mostly a dry one.

Lake Musters

This lake, once called Otrón by the ancient tehuelches, received its current name in 1876 from naturalist and geographer Francisco Pascasio Moreno
Francisco Moreno
Francisco Pascacio Moreno was a prominent explorer and academic in Argentina, where he is usually referred to as Perito Moreno...

 who aimed to honour the patagonian adventurer George Chaworth Musters.

Musters occupies a cretacic
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 conformed depression in the central patagonic mesa. It receives the highly branched inflow of Senguerr river by its southern coast after a 350 km voyage from the Andes. Several of those branches reach lake Colhué Huapi by a sinuous course called Falso Senguerr; the only permanent one feeding such lake.

Te lake is of tectonic origin, with average depths of 20m, which gives a deep blue water hue. It is considered mesotrophic, considering its nutrient and algae mass (<5,2 g/m³). Musters presents an abundant aquatic fauna comprising patagonian perch (Percichthys trucha) and patagonian silversides (Odontesthes microlepidotus). Also, as it's the case with most patagonian lakes, foreign salmonidae
Salmonidae
Salmonidae is a family of ray-finned fish, the only living family currently placed in the order Salmoniformes. It includes salmon, trout, chars, freshwater whitefishes and graylings...

 have been implanted, like Salvelinus fontinalis, Oncorhynchus mykiss, and in lesser amounts, Salmo fario. These species have added environmental pressure over two native species nowadays endangered in the lake (Diplomystres viedmensis mesembrinus and Galaxias platei) .

Lake Colhué Huapi

The name of this large water mirror comes from the mapuche
Mapuche
The Mapuche are a group of indigenous inhabitants of south-central Chile and southwestern Argentina. They constitute a wide-ranging ethnicity composed of various groups who shared a common social, religious and economic structure, as well as a common linguistic heritage. Their influence extended...

 language. Colhué means "reddish or red place" and Huapi means "island". It is a reference to one of the many clay conformed islands of such lake.

Colhué Huapi fills a shallow depression
Blowout (geology)
Blowouts are sandy depressions in a sand dune ecosystem caused by the removal of sediments by wind.Blowouts occur in partially vegetated dunefields or sandhills. A blowout forms when a patch of protective vegetation is lost, allowing strong winds to "blow out" sand and form a depression...

 formed by strong eolic action over an area of fine clays. It is fed by Falso Senguerr river, a sinous branch of main Senguerr river. The lake coast is dominated by extensive wetlands mainly at its feeding zone. In contrast to its neighbour Musters (separated by a 12 km wide 695 m high isthmus) Colhué has an average 2 meters depth and high water turbidity due to suspended sediments deposited by constant wind.

It is considered an argilotrophic brackish water
Brackish water
Brackish water is water that has more salinity than fresh water, but not as much as seawater. It may result from mixing of seawater with fresh water, as in estuaries, or it may occur in brackish fossil aquifers. The word comes from the Middle Dutch root "brak," meaning "salty"...

 lake because of its high levels of inorganic sediments in suspension. As with lake Musters, and despite the high water opacity, patagonian perch and silversides have large populations. Of high interest is the native big mouth perch (Percichthys colhuehuapensis) currently endangered by pressure of human introduced foreign salmonidae.

Environmental concerns

Several water offtakes have been progressively placed at lake Musters for drinking water supply, as well as many diversions of Senguerr river to feed oil extraction facilities in the nearby region. This complicated the already resented hydro balance of the whole system to the extend of almost collapse at Colhué Huapi whose peripheral surface continuously retracts and dries.
The hydrological equilibrium of the whole basin has been negative in the past seventy years. Currently these lakes situation could be defined as compromised.

External links

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