Chott Melrhir

Chott Melrhir
View from space. Note that most of the lake is already dried up in this picture.
Coordinates	Coordinates: 34°20′N 6°20′E / 34.333°N 6.333°E / 34.333; 6.333
Type	endorheic salt lake
Catchment area	68,750 km2 (26,540 sq mi)
Basin countries	Algeria
Surface area	6,700 km2 (2,600 sq mi)

Chott Melrhir (Arabic: شط ملغيغ‎‎) also known as Chott Melghir or Chott Melhir is an endorheic salt lake in northeastern Algeria. It the westernmost part of a series of depressions, which extend from the Gulf of Gabès into the Sahara. They were created between Miocene and as a result of compression accompanying the formation of the Atlas Mountains. With the maximum area of about 6,700 km² (2,600 sq mi), Chott Melrhir is the largest lake in Algeria. It lies almost entirely below the sea level and contains the lowest point in Algeria, −40 meters (−130 feet). Its size varies over the year and is usually larger than 130 km (81 mi) from east to west. The nearby cities are Biskra (60 km north-east), El Oued and Touggourt (85 km south).

During the rain season in winter, the lake is filled by numerous wadi (periodically drying rivers), mostly from north and north-west. The largest of them are the Djedi and Arab running from west to east down the slopes of Aurès Mountains. Others include Abiod, Beggour Mitta, Biskra, Bir Az Atrous, Cheria, Demmed, Dermoun, Derradj, Djedeida, Djemorah, Halail, Horchane, Ittel, Mechra, Melh, Mzi, Messad, Oum El Ksob, Soukies, Tadmit and Zeribet. In summer, the lake and most the rivers feeding it dry out, and Chott Melrhir turns into a salt pan. The annual water evaporation varies between 9.6 and 20 km³, and evaporation from soil nearby the lake can reach 14 km³.

Chott Melrhir is separated from the nearby Chott Meorouane, which lies south-west, by a stripe of permanently dry land which can be as narrow as 4 kilometers in some places. The bottom of the lake is mostly composed of gypsum and mud and is covered in salt in summer. The lake emits a garlic-like odor. Although the dry soil in and around the lake appears arable, it is nearly barren due to the high concentration of salt. For the same reason, the soil absorbs much condensation overnight that keeps it partly humid during much of the day.