Ounianga Lakes

Lakes of Ounianga Serir
Geographical location	Ennedi-Ouest Province; Ounianga Lakes; Sahara ; Chad
Tributaries	Groundwater
Drain	evaporation
	Data
Coordinates	18 ° 55 '45 " N , 20 ° 51' 1" E Coordinates: 18 ° 55 '45 " N , 20 ° 51' 1" E
particularities	Largest lake landscape in the Sahara

The lakes of Ounianga denote a lake landscape in the province of Ennedi-Ouest in northeastern Chad . The lakes are connected underground and are the remnants of a much larger lake system , which developed during the so-called green Sahara period , which ran from around 10,000 to 1,500 BC. Lasted over the Chad Basin . Today the currently 18 lakes are located in the hyperarid Ennedi region of the Sahara , with less than 2 millimeters of precipitation annually. The two lake groups Ounianga Kebir and Ounianga Serir are about 40 km apart. With a total surface of 15.15 km² and a maximum depth of 27 meters, they are the largest and deepest lake landscape in the Sahara. The lakes of Ounianga vary in size, depth, color, and their waters vary in chemical composition from fresh water to hypersaline . On July 1, 2012, the lakes of Ounianga were added to the list of UNESCO World Heritage Sites as the first world natural heritage site in Chad .

Ounianga Kebir

The 4 lakes of Ounianga Kebir (Arabic kebir = large) ( ⊙ ) are located in the village of the same name : 19.055 20.505555555556

Lake Yoa (French lac Yoa or lac Yoan )
Lake Uma (French lac Oma ), with the side arm Katam Lake (French lac Béver )
Mioji Lake (French lac Mioji )
Forodon Lake (French lac Forodone )

Ounianga Serir

At the village of Ounianga Serir (derived from the Arabic saker = small) further east ( ⊙ ) lies the group of 14 lakes grouped under the same name: 18.929166666667 20.850277777778

Ardiou lake (French lac Ardjou )
Abrome Lake (French lac Abromé )
Boul lake (French lac Boul )
Dirke lake (French lac Dierké )
Edem Lake (French: Lac Edem ): with a surface area of almost 2 km², the largest freshwater lake in the Sahara
Melekoui Lake (French lac Melekoui )
Tarem lake (French lac Tarem )
Tibichei Lake (French lac Tibitchei )
Lake Teli (French: Lac Teli ): the largest and most saline of the lakes with a surface area of 6.5 km ²
Agouta lake (French lac Agouta )
Lake Hogou (French lac Hogou )
Lake Diara (French lac Djara )
Bedrim Lake (French lac Bedrim )
Bokou lake (French lac Boukou )

These lakes stand out for their headlands running in a north-south-westerly direction, which are formed by sand dunes blown by the trade winds .

Hydrogeology

The lakes of Ounianga form a hydrological system that is unique in the deserts of the earth. Normally, waters and soils become too salty at a high evaporation rate, since no more water can drain away , so that the salt dissolved in the water remains behind during evaporation and thus continuously accumulates.

This is the case with the Ounianga Kebir lake group. The evaporation loss of Lake Yoa, for example, is up to 6000 mm per year due to the extreme environmental conditions, and the water is salinizing, as are the other lakes of the Kebir group.

Not so in Ounianga Serir. Most of the lakes in this group are covered with thick mats of reed, which reduce the exposure of the water surface by about 50%, which considerably reduces evaporation. These mats do not exist on the surface of the saline Lake Teli, and therefore the rate of evaporation is much higher here. Here the evaporation is 6 to 7.80 m per year, which is the world record. This results in a permanently lower water level than in the surrounding lakes, and a natural sinking funnel is formed . The water from the surrounding lakes seeps through the water-permeable dunes into Lake Teli, which means that the water bodies of the smaller lakes are constantly replenished with fresh groundwater and thus no salt can accumulate. The constant feed from the underground springs results in freshwater and slightly salty lakes, the water temperature of which remains constant at a cool 17-23 degrees Celsius.

fauna

There is an endemic species of cichlid, Astatotilapia tchadensis , that lives only here in Lake Bokou . In addition, there and in Lake Djara the cichlid live coptodon zillii , Hemichromis fasciatus , Hemichromis cf. letourneuxi and Sarotherodon galilaeus those Cyprinodontiformes Epiplatys bifasciatus and Poropanchax normani and polypterus senegalus ( Polypterus senegalus ). The lakes of Ounianga have the most species-rich fish fauna of all the Sahara lakes.

photos

Yoa lake
Yoa lake
Katam lake
Lake in the Ounianga Serir

Web links

Commons : Lakes of Ounianga - Collection of images, videos and audio files

Entry on the UNESCO World Heritage Center website ( English and French ).
Satellite photo of the lakes from the Earth Observatory (post-processed)
Photo tour in Chad

Individual evidence

↑ Country information Chad on Ramsar Wetlands, p. 14 ( Memento from September 24, 2012 in the Internet Archive ) (PDF; 177 kB)
↑ ^a ^b UNESCO World Heritage Center: Lakes of Ounianga. Retrieved May 15, 2020 .
↑ Olivier Sénégas, Tiffany Tchang, Marc-André Bünzli, François Zwahlen, Pascal Marguerat, Yves Haeberlin, Maëlle Aubert, Ivann Milenkovic: Syntèse hydrogéologique du nord et de l'est du Tchad . Ed .: Program ResEau 1, UNITAR-UNOSAT. December 2016, p. 235 , p. 121 .
↑ ^a ^b Bert Van Bocxlaer, Dirk Verschuren, Georg Schettler, Stefan Kröpelin: Modern and early Holocene mollusc fauna of the Ounianga lakes (northern Chad): implications for the palaeohydrology of the central Sahara . In: Journal of Quaternary Science . tape 26 , no. 4 , May 2011, p. 433-447 , doi : 10.1002 / jqs.1469 ( wiley.com [accessed May 15, 2020]).
^ WHC: Proposition d'inscription des Lacs d'Ounianga , S. XV
↑ Stefan Kröpelin : Lakes in the Sahara - a high-precision environmental archive. In: forschung - Magazin der Deutschen Forschungsgemeinschaft , Issue 3, 2008, pp. 4–9 (available online at Schattenblick.net, accessed on December 4, 2015)
↑ Mike Creutz, Bert Van Bocxlaer, Moussa Abderamane, Dirk Verschuren: Recent environmental history of the desert oasis lakes at Ounianga Serir, Chad . In: Journal of Paleolimnology . tape 55 , no. 2 , February 2016, ISSN 0921-2728 , p. 167-183 , doi : 10.1007 / s10933-015-9874-y ( springer.com [accessed May 15, 2020]).
↑ Sébastien Trape: Epiplatys bifasciatus (Steindachner, 1881) (Nothobranchiidae) and Hemichromis fasciatus Peters, 1852 (Cichlidae), two relict fish species in the Sahara desert. In: Bonn Zoological Bulletin. Vol. 67, No. 1, 2018, pp. 37-40.

[1] Country information Chad on Ramsar Wetlands, p. 14 ( Memento from September 24, 2012 in the Internet Archive ) (PDF; 177 kB)

[:0-2] UNESCO World Heritage Center: Lakes of Ounianga. Retrieved May 15, 2020 .

[3] Olivier Sénégas, Tiffany Tchang, Marc-André Bünzli, François Zwahlen, Pascal Marguerat, Yves Haeberlin, Maëlle Aubert, Ivann Milenkovic: Syntèse hydrogéologique du nord et de l'est du Tchad . Ed .: Program ResEau 1, UNITAR-UNOSAT. December 2016, p. 235 , p. 121 .

[:1-4] Bert Van Bocxlaer, Dirk Verschuren, Georg Schettler, Stefan Kröpelin: Modern and early Holocene mollusc fauna of the Ounianga lakes (northern Chad): implications for the palaeohydrology of the central Sahara . In: Journal of Quaternary Science . tape 26 , no. 4 , May 2011, p. 433-447 , doi : 10.1002 / jqs.1469 ( wiley.com [accessed May 15, 2020]).

[unesco_XV-5] WHC: Proposition d'inscription des Lacs d'Ounianga , S. XV

[6] Stefan Kröpelin : Lakes in the Sahara - a high-precision environmental archive. In: forschung - Magazin der Deutschen Forschungsgemeinschaft , Issue 3, 2008, pp. 4–9 (available online at Schattenblick.net, accessed on December 4, 2015)

[7] Mike Creutz, Bert Van Bocxlaer, Moussa Abderamane, Dirk Verschuren: Recent environmental history of the desert oasis lakes at Ounianga Serir, Chad . In: Journal of Paleolimnology . tape 55 , no. 2 , February 2016, ISSN 0921-2728 , p. 167-183 , doi : 10.1007 / s10933-015-9874-y ( springer.com [accessed May 15, 2020]).

[8] Sébastien Trape: Epiplatys bifasciatus (Steindachner, 1881) (Nothobranchiidae) and Hemichromis fasciatus Peters, 1852 (Cichlidae), two relict fish species in the Sahara desert. In: Bonn Zoological Bulletin. Vol. 67, No. 1, 2018, pp. 37-40.