Lake Assal

Africa’s lowest point, and saltier than the Dead Sea

Lake Assal lies 155 metres below sea level in the middle of Djibouti, about 120 km west of Djibouti city, at the western end of the Gulf of Tadjoura where the Great Rift Valley begins. It is the lowest point on land in Africa and the third lowest on Earth, after the Sea of Galilee and the Dead Sea, and its Arabic name, Buḥayrah ʿAsal, means Honey Lake. Nothing about it is sweet. No river flows out, the sun and wind evaporate an estimated 460 million cubic metres a year, and the brine left behind is about ten times as salty as the sea, close to 300 grams of salt in every litre.

The lake is fed from underneath. Seawater from the bay of Ghoubbet El Kharab, 10 km to the southeast, seeps by gravity through some 5 km of fissured basalt and emerges as hot springs on the eastern shore, at roughly 5,000 to 8,000 litres a second and about as salty as the ocean, and then the desert concentrates it. Geologists see the Assal-Ghoubbet rift as a continent pulling apart, a rift that will one day become an arm of the Red Sea, and the Ardoukoba volcano stands about 3 km away.

The result looks unearthly. An oval of brine about 54 square kilometres lies beside a white plain of crystallised salt more than 60 metres deep, with gypsum and black basalt banding the shores, and at midday the water turns emerald against the snow-white rim. Summer temperatures climb past 50°C between May and September. Common bacteria thrive in the water, but no fish do; only near the hot springs have small minnows been reported. One lone palm tree stands by the road.

Salt has made the lake valuable for centuries. Afar camel caravans hauled slabs from its salt bank into the mountains of Ethiopia to barter for sorghum and coal, and traded with southern Abyssinia for coffee, ivory and musk. Industrial mining revived after 1990, and four concessions were awarded in 2002. Around 2,000 people now live near the shore, many of them Afar, and life is hard: when the BBC visited, homes were built of chicken wire and corrugated iron, the heat governed when people worked and slept, and the one man who had put up a shade roof charged visitors to sit under it. People there pin their hopes on tourism. Djibouti has proposed the lake and Ardoukoba together for World Heritage listing.