Qattara Depression
The Qatttara Depression or Kattara Depression is a largely barren desert basin located in the northern and eastern part of the Sahara Desert (the Libyan Desert or "Western Desert" relative to the Nile River) in western Egypt.
Geography
Qattara is an irregularly shaped area between lattitudes of 28°35' and 30°25' North and longitudes of 26°20' and 29°02' East. It extends about 285 kilometers (km) SW-NE and 135 kilometrs N-S. About 19,605 km2 of the Qattara Depresssion is below sea level, with the lowest elevation being -133 meters. The eastern end of the depression is 210 km west of Cairo and 130 km southwest of Alexandria. Hughes and Hughes (1992) report the followin charateristics for this region of northern Africa:
It is bounded by a steep, and in places precipitous, escarpment, along the northwestern and northern sides, which rises to heights of over 200 meters upto the El Diffa Plateau that lies between the depression and the Mediterranean Sea. By contrast the southern and eastern sides of the depression rise more gradually to the plateau of the Western Desert.
Saline marshes/deserts, up to 30 km wide and over 150 km long, are situated under the escarpment along the northern side of the depression, and other marshes extend out into the southern central part of the basin, occupying a total of about 300,000 hectares. (3,000 km2 )
Wind blown sands have intruded into the depression along the southern margins and are encroaching upon the marshes in the central and extreme southern areas.
Elsewhere on the south side, the floor of the depression comprises black gravels or bare broken rock, or there are rock/salt plateaux, and in the far south there is a hard clay pan.
There are six semi-permanent saline lakes, one, Lake el Maghra (30°14'N 28°53'E), at the extreme northeastern end of the depression, and three along the most southerly margin, on a gravel plain at the edge of the sand sea. These are situated at 28°39'N and 26°41'E; 28°40'N and 26°27'E (Lake el Bahrein); and 28°43'N and 26°56'E (Lake Sitra). Each covers several hundred hectares. There are springs at Ain Tibaghbagh (29°05'N 26°23'E), el Araq (28°57'N 26°30'E) and el Watya (28°51'N 26°43'E) along the southern edge.
The landscape of the Qattara Depression is believed to be largely shaped by erosion and deposition by wind (eolian processes). When the force of wind is concentrated on a particular spot in the landscape, erosion can carve out a pit known as a deflation hollow. Deflation hollows range in size from a few meters to a hundred meters in diameter, and may develop over several days or a couple of seasons. Much larger depressions are also found in the arid regions throughout the world. These broad, shallow depressions, called pans, can cover thousands of square kilometers. The Qattara Depression is one of the largest pans in the world.
Ecology
Ecologically, Qattara is included with the Saharan halophytics ecoregion defined by the World Wildlife Fund. This ecoregion is restricted to some suitable semi-desert and desert locations in the northern portion of Africa, in Morocco, Algeria, Tunisia, Libya, Egypt, Western Sahara and Mauritania. The most extensive of the areas are Chott Melghir, Oued Rir Vally, Hodna, Sebkhat Tidikelet, Sebkha of Timimoun, Tefedest, Chott El Djerid and the Qattara and Siwa Depressions in Egypt.
There are saline marshes under the northwestern and northern escarpment edges, and extensive playas that flood occasionally. Moghra oasis, the one oasis in the depression, is uninhabited and has a 4 km2 brackish lake, including Phragmites swamp. Salt marshes also occur and occupy approximately 300 km2, although in some areas, wind blown sands are encroaching. About one-quarter (26 percent) of the entire Qattara is occupied by playas, which are comprised of hard crust and sticky mud, and which are occasionally filled with water.
Settlement
On the southwest edge of the Qattara Depression is the Qara Oasis. This oasis is inhabited by about 300 people. The Depression is also inhabited by the nomadic Bedouin people and their flocks. The Bedouin often spend time in the Moghra Oasis during times of water scarcity in the dry seasons.
Hughes and Hughes (1992) report that consideration is currently being given to a proposal to flood the depression with sea water, thus creating the world's largest human-made lake as of 2011. This would raise the water table in the surrounding desert and water evaporated from the lake might condense over the Western Desert with beneficial effects for projected agriculture.
The World Wildlife Fund notes that such a plan would destroy the natural habitats and replace them with a large salt lake. Further, an additional threat is the continued natural drying of the area (perhaps induced by global warming), which might result in the complete loss of wetland habitats and their replacement with salt flats and sand areas similar to those seen widely in the Sahara Desert.
History
Before modern times, the Sahara was traversed mainly by Arab traders, natives and pilgrims of which the best known is Ibn Battuta. Ibn Battuta is a Moroccan explorer who lived from 1304 to 1368 and wrote about his extensive travels to North Africa, West Africa, Southern Europe, Eastern Europe, the Middle East, South Asia, Central Asia, Southeast Asia and China.
Ralph Bagnold, a British military commander and explorer, greatly extended our knowledge about the Qattara Depression through numerous journeys in the 1920s and 1930s. Many of these trips used motor vehicles (Ford Model-Ts) which employed special techniques for driving in desert conditions. He also wrote the scientific book "The Physics of Blown Sand and Desert Dunes" first published in 1941.
Further reading
- Bagnold, R.A. 1931. Journeys in the Libyan Desert, 1929 and 1930. The Geographical Journal 78(1): 13-39; (6):524-533.
- Bagnold, R.A. 1933. A further journey through the Libyan Desert. The Geographical Journal 82(2): 103-129; (3): 211-213, 226-235.
- Bagnold, R.A. 1935. Libyan Sands: Travel in a Dead World. Travel Book Club, London. 351 p.
- Bagnold, R.A. 1939. A lost world refound. Scientific American 161(5, November): 261-263.
- Hassanein Bey, A.M. 1924. Crossing the untraversed Libyan Desert. The National Geographic Magazine 46(3):233-277.
- Hughes, R. H. and J. S. Hughes. 1992. A Directory of African Wetlands. IUCN, Gland, Switzerland. ISBN-10: 2880329493.
- Ramsar Sites Information Service (RSIS). Egypt. Accessed August 21, 2011.
- Rohlfs G. 1875. Drei Monate in der Libyschen Wüste (Three Months in the Libyan Desert). Verlag von Theodor Fischer, Cassel. 340 p.
- Saint-Exupéry, A. de. 1940. Wind, Sand and Stars. Harcourt, Brace & Co, New York.
- Scott, C. 2000. Sahara Overland: A Route and Planning Guide. Trailblazer Publications. 544 p. ISBN: 978-1-873756-76-8.
- Zittel, K.A. von. 1875. Briefe aus der libyschen Wüste (Letters from the Libyan Desert). München.
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