The Lakes of Ounianga in the Sahara Desert, Chad

Lakes of Ounianga are series of 18 lakes in the Sahara Desert, in North-Eastern Chad. They are found in a basin between the mountains of Ennedi East and West Tibesti. Names of nearby villages are used to name the lakes. It was created as an addition to the original. The lakes were declared a UNESCO World Heritage Site in 2012.

Lake in the Ounianga Serir, northern Chad (© George SteinmetzCorbis).

Ounianga lakes

Lakes of Ounianga chad are located in a hyper-arid desert with a minimum of 2 millimeters of rainfall per year. The ancient water flows from a shallow basin beneath hills and sandstone cliffs. This unique hydro-logical system can sustain the largest permanent freshwater lake in an arid desert environment in the world. Ounianga lakes are remnants are of a single, large lake that once occupied the basin about 5,000 to 15,000 years ago. The climate changed over the millennia and the lake began to shrink. Large, wind-driven sand dune invasions of the depression caused it to be divided into smaller basins.

These 18 Lakes are divided into two groups, the Ounianga Sérir group and Ounianga Kébir each about 40 km apart of the Ounianga basin. They differ in their chemical composition. Some are so salty that they cannot support basic life forms, while others can sustain aquatic plants and fish. The Ounianga Sérir is about 45 to 60 kilometers southeast of Ounianga Kébir and Lake Teli is the largest lake and one of the most important for biological reasons. It has a total surface area of 4.4km2 with a maximum depth of 10 meters. The water level in the lakes is variable between 350 and 380 meters above sea level . Its freshwater supports a wide range of life. Lakes under the Sahara desert because the sandy substrate is porous, water can flow freely underground. Lake Teli and 13 smaller lakes are part of the eastern group.

The second group of four lakes in the Ounianga Kébir, which is located further west. It is dominated by Lake Yoa it is 3,6 km2 and 27m deep. This hypersaline lake supports algae and a few micro-organisms. The rocks surrounding the lake are covered in white salt deposits. A sprawling village with approximately 9,000 inhabitants is found amongst the hills and dunes nearby. Lake Motro, about 30 kilometers southeast of Unianga Kébir. This is the last place that is habitable on the trans-Sahara truck route to Libya.

The freshwater ancient lakes of Ounianga Chad in the Sahara desert

Lakes in the Ounianga Sérir, have freshwater, such as Obrom; Idem; Aujou; Boul; Hogo; Djiara; Aolta; Daleyda; Boulkou, and another in their immediate vicinity, Lake Eliné, has saltwater.

These Sahara desert lakes' Dark surfaces are almost entirely segregated by orange-colored sand dunes, which flow from the northeast into the depression. One of the lakes nearby measured an evaporation rate exceeding 6 meters per year due to the northeast winds that blow almost all year and cloudless skies. Only one of the ten lakes is saline, despite this.

The apparent paradox is caused by the freshwater lake in the sahara desert. The Ounianga Depression is where freshwater from an extremely large aquifer flows into the desert's heart. Despite the high evaporation rate, the aquifer is large enough that it can continue to supply water to small lakes. Evaporation is also reduced by floating reeds. These lakes create a unique hydrological system in the Sahara Desert.

V-shaped lakes — The northeast desert wind blew, carrying sand from the plateau up through the land. It deposited it right where farmers were planting crops. The lake dwellers realized that the sand would eventually choke their crops and orchards so they built barriers to stop it. These barriers can be clearly seen on aerial photos at various locations between Ounianga Kebir (and Serir). These barriers appear in the form of a series of "V"s like VVVVV It would have taken many people to build the layers of barriers visible today, which appears extraordinary.

First Image credit eMRaistlin Uth Majere