The Qattara Depression () is a depression in northwestern Egypt, specifically in the Matruh Governorate. The depression is part of the Western Desert of Egypt. The Qattara Depression lies below sea level, and its bottom is covered with salt pans, sand dunes, and salt marshes. The depression extends between the latitudes of 28°35' and 30°25' north and the longitudes of 26°20' and 29°02' east.
The Qattara Depression was created by the interplay of salt weathering and wind erosion. Some west of the depression lie the oases of Siwa in Egypt and Jaghbub in Libya in smaller but similar depressions.
The Qattara Depression contains the second lowest point in Africa at an elevation of below sea level, the lowest point being Lake Assal in Djibouti. The depression covers about , a size comparable with Lake Ontario or twice as large as Lebanon. Due to its size and proximity to the shores of the Mediterranean Sea, studies have been made proposing to flood the area for various usages, such as the potential to generate hydroelectricity there.
Geography
The Qattara Depression has the shape of a teardrop, with its point facing east and the broad deep area facing southwest. The northern side of the depression is characterised by steep escarpments up to high, marking the edge of the adjacent El Diffa plateau. To the south the depression slopes gently up to the Great Sand Sea.
Within the Depression are salt marshes, under the northwestern and northern escarpment edges, and extensive dry lake beds that flood occasionally. The marshes occupy approximately , although wind-blown sands are encroaching in some areas. About a quarter of the region is occupied by dry lakes composed of hard crust and sticky mud, and occasionally filled with water.
The depression was initiated by either wind or fluvial erosion in the late Neogene, but during the Quaternary Period the dominant mechanism was a combination of salt weathering and wind erosion working together. First, the salts break up the depression floor, then the wind blows away the resulting sands. This process is less effective in the eastern part of the depression, due to lower salinity groundwater.
Ecology
Groves of umbrella thorn acacia (Vachellia tortilis), growing in shallow sandy depressions, and Phragmites swamps represent the only permanent vegetation. The acacia groves vary widely in biodiversity and rely on runoff from rainfall and groundwater to survive. The Moghra Oasis in the northeastern part of the Depression has a brackish lake and a Phragmites swamp.
The southwestern corner of the depression is part of the Siwa Protected Area which protects the wild oasis in and around the Siwa Oasis.
The Depression is an important habitat for the cheetah, with the largest number of recent sightings being in areas in the northern, western and northwestern part of the Qattara Depression, including the highly isolated, wild oases of Ain EI Qattara and Ein EI Ghazzalat and numerous acacia groves both inside and outside the depression.
Gazelles (Gazella dorcas and Gazella leptoceros) also inhabit the Qattara Depression, being an important food source for the cheetah. The largest gazelle population exists in the southwestern part of the Qattara Depression within a vast area of wetlands and soft sand. The area of , includes the wild oases of Hatiyat Tabaghbagh and Hatiyat Umm Kitabain, and is a mosaic of lakes, salt marshes, scrubland, wild palm groves and Desmostachya bipinnata grassland.
Other common fauna include the Cape hare (Lepus capensis), Egyptian jackal (Canis aureus hupstar), sand fox (Vulpes rueppelli) and more rarely the fennec fox (Vulpes zerda). Barbary sheep (Ammotragus lervia) were once common here but now they are few in number.
Extinct species from the area include the scimitar oryx (Oryx dammah), addax (Addax nasomaculatus) and bubal hartebeest (Alcelaphus buselaphus). Also the Droseridites baculatus, an extinct plant known only from fossils of its pollen, was found at the Ghazalat-1 Well.