Lake Assal (Arabic: بحيرة عسل Buḥayrah ʿAsal, lit. “Honey Lake”) is a crater lake in central-western Djibouti. It is located at the western end of Gulf of Tadjoura between Arta Region, and Tadjoura Region, touching Dikhil Region, at the top of the Great Rift Valley, some 120 km (75 mi) west of Djibouti city. Lake Assal is a saline lake that lies 155 m (509 ft) below sea level in the Afar Triangle, making it the lowest point on land in Africa and the third-lowest point on Earth after the Sea of Galilee and the Dead Sea. No outflow occurs from the lake, and due to high evaporation, the salinity level of its waters is 10 times that of the sea, making it the fifth most saline body of water in the world, behind Garabogazköl, Lake Retba, Gaet'ale Pond and Lake Elton. The salt in the lake is exploited under four concessions awarded in 2002 at the southeast end of the lake; the major share of production (nearly 80%) is held by Société d’Exploitation du Lac and Société d’Exploitation du Salt Investment S.A de Djibouti. The lake is a protected zone under Djibouti's National Environmental Action Plan of 2000. However, the law does not define the boundary limits of the lake. Since the exploitation of the salt from the lake was uncontrolled, the Plan has emphasized the need for managing the exploitation to avoid negative impact on the lake environment. The Government of Djibouti has initiated a proposal with UNESCO to declare the Lake Assal zone and the Ardoukoba volcano as a World Heritage Site.
Geography
Lake Assal is located in the middle of Djibouti, in a closed depression at the northern end of the Great Rift Valley. Situated in the Danakil Desert, it is bounded by hills on the western region. The lake lies at an elevation of 155 m (509 ft) below sea level, making it the lowest point of Africa. The lake is characterized by two parts. The dry part of the lake, resulting from evaporation of the lake waters, is a white plain dry lake bed on the west/northwest side, which is a large expanse of salt. The second part is the highly saline water body. The watershed area of the lake is 900 km2 (350 sq mi).
Lake Assal, in an oval shape (length 19 km (12 mi) and width 6.5 km (4.0 mi)), consists of two distinct parts; one is "crystallised salt surface" zone of 68 km2 (26 sq mi) and the other is the high saline brine area of 54 km2 (21 sq mi). The crystallised salt zone extends to a depth of more than 60 m (200 ft) whose estimated resource is about 300 million tonnes. The lake measures 10 by 7 km (6.2 by 4.3 mi) and has an area of liquid brine 54 km2 (21 sq mi). The maximum depth is 40 m (130 ft), whereas the mean depth is 7.4 m (24 ft), which makes for a water volume of 400 million cubic metres (320,000 acre⋅ft). Salt extraction by the Afar nomad tribes of camel drivers and Issas from Lake Assal's salt bank established the ancient caravan routes. These linked the lake with the mountains of Ethiopia for barter trading such items as sorghum, coal, and other commodities. Salt was also bartered with South Abyssinia for items like coffee, ivory, musk, and also (historically) slaves. It was a source of wealth for the local tribes. Since 1990, industrial mining has been revived with development of roads linking with the Ghoubbet-el-Kharab bay by the Gulf of Tadjoura. The present road to Lake Assal is paved. The lake is 120 km (75 mi) from Djibouti city. It is also reported that the lake water level is receding as discerned from a 50-foot (15 m) mark on the banks of the lake from the present water level.
Climate Located in the hot desert, the lake experiences summer temperatures as high as 52 °C (126 °F) from May to September. Winter temperatures are not low at 34 °C (93 °F) from October to April, with the coastal area experiencing rains. Strong, dry, hot winds are part of the environment. The monthly temperature variation is reported to be 6 °C (11 °F). During the summer season, the dry hot winds blow in two directions; namely, the Sabo winds from the southwest and the Khamsin winds from the northwest. Winds during October and April blow from the east, resulting in sporadic rains. Incidence of rainfall varies widely with January, April, May, and October recording rains. June to August are dry months. The mean annual rainfall in 1993 and 1997 was reported as 773 mm (30.4 in) and 381 mm (15.0 in), respectively. The lowest rainfall of 23 mm (0.91 in) was recorded in 1996. Water temperature of the lake is reported to reach 33–34 °C (91–93 °F). However, when the wind velocity and evaporation are low, the temperature recorded was found to be 20 °C (68 °F) for surface water and above 25 °C (77 °F) at shallow depths of the lake. The lake water colour also changes over the duration of the day, at times appearing in fluorescent colours. In the middle of the day, the water looks unusual with its emerald color on the background of the snow-white shore.
Geology
History
The lake's geological history was studied by French geologists who compared it with the geology of Danakil lakes. According to this study, the lake originally contained freshwater overlying the 15 m (49 ft) mantle of tufas, marls and calcretes. At an elevation of 100 m (330 ft) "Melanoides tubeculatus (Melania tuberculata), Corbicula consobrina and Coelatura teretiuscula" were reported "resting on the basalts". At the present bed level, the formations of marls with Ervilius purpura and cerithium sp., are indicative of gradual transformation over the centuries to saline water lake; the reason could be on account of lagoon or marine intrusion. Diatomite with Navicula sp., kankar and nodules of gypsum are discerned above the saline band. These bands are converted into gypsiferous layers succeeded by rock salt layers; these layers are seen up to the lake level.
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