Sistan Basin

Sistan Basin

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[[File:Helmandrivermap.png|thumb|350 px|Map of the Sistan/Helmand River drainage basin]] [[Image:Afghanistan.A2003266.0625.500m.jpg|thumb|250px|Satellite image of southern Afghanistan and Iran in dust storm]] The '''Sistan Basin''' is an inland [[endorheic basin]] encompassing large parts of southwestern [[Afghanistan]] and southeastern [[Iran]], one of the driest regions in the world and an area subjected to prolonged [[drought]]s. Its [[Drainage basin|watershed]] is a system of rivers flowing from the highlands of Afghanistan into [[freshwater]] [[lake]]s and [[marsh]]es and then to its ultimate destination: Afghanistan's [[Saline water|saline]] [[Godzareh depression]], part of the extensive Sistan [[drainage basin|terminal basin]]. The [[Helmand River]] drains the basin's largest [[drainage basin|watershed]], fed mainly by [[snowmelt]] from the mountains of [[Hindu Kush]], but other rivers contribute also. A [[basalt]] hill, known as [[Mount Khajeh]], rises beside the lakes and marshes of the basin. == Lakes == The lowest part of the Sistan Basin contains a series of shallow lakes, known as ''[[hamuns]]''. It appears that in the past there was a single [[Hamun Lake]], but there are now three separate lakes. From north to south the lakes are: === Hamun-e Puzak === The Hamun-e Puzak lies mostly in Afghanistan. It receives water from the Shelah Charkh channel of the Helmand River, and also from the Khash River and other small rivers. === Hamun-e Sabari === The Hamun-e Sabari is spit between Iran and Afghanistan. It receives water from the Parian branch of Helmand River, the [[Farah River]] and the [[Harut River]]. === Hamun-e Helmand === {{main|Hamun-e Helmand}} The largest proportion of the Helmand River's waters flow into the Hamun-e Helmand, which is entirely in Iran, by a channel known as the Rud-e Sistan. === Hydrology === In times of flood the hamuns join into one large lake, and once every 20 years or so the floodwaters create an overflow from the Hamun-e Helmand by a normally dry river known as the Shela Rud, terminating in the Godzareh depression. In 1885 there was an exceptional flood, and the floodwaters filled the depression for three years. In recent years, particularly during a drought from 1998 to 2005, the hamuns have dried up completely. ==Ecological importance== Since the economy of the region is based on agriculture, subsistence depends on snowmelt and rainfall in the high mountains to sustain the health of the Sistan Basin and its [[wetland]]s. This source of water severely fluctuates over time and therefore has resulted in fundamental problems of survival for human settlements in the area. A severe [[drought]] began at the turn of twenty-first century and as of 2005 has lasted six years with extreme consequences for the populations. The region's economic survival is dependent on the wetland's products. For example, [[Reed bed|beds of reeds]] provide [[livestock]] food, cooking and heating fuel, and the raw materials for structures and [[handicraft]]s. Water availability affects the income derived from fishing and hunting, an important source of income. The result of the drought has been the collapse of the local economy as well as destruction of the wetland's [[ecology|ecological system]], causing damage to the [[agriculture]] in the [[River delta|delta]] based on the Helmand River's irrigation. ==Archeology== For more than 5,000 years the Sistan basin has been inhabited by sophisticated cultures and thus contains some key [[archaeology|archaeological]] sites. The [[Shahr-i Sokhta]], or "Burnt City", in Iran, built in 3100 B.C. near a currently dried-up branch of the Helmand River, was abandoned one thousand years later, most likely due climate changes that altered the river course. [[Kang (afghanistan)|Kang]] and [[Zaranj]] in Afghanistan were major [[medieval]] cultural hubs, now covered by sand. Here, signs of historical [[irrigation system]]s, including [[canal]]s, are still visible in the [[Dasht-e-Margo]] and [[Chakhansur]] areas while elsewhere canals are filled with [[silt]] and agricultural fields buried by shifting [[sand]]. Today the area is sparsely populated. Excavations have also revealed a citadel complex, and the remains of a [[Zoroastrianism|Zoroastrian]] fire temple, on [[Mount Khajeh]]. ==External links== *[http://visibleearth.nasa.gov/view_rec.php?id=16549 Dust storm over Afghanistan and Pakistan] *[http://earthobservatory.nasa.gov/Study/hamoun/ From Wetland to Wasteland: The Destruction of the Hamoun Oasis] *[http://www.briancoad.com/Introduction/sistanbasin.htm Freshwater Fishes of Iran: Introduction - Drainage Basins - Sistan] {{coord missing|Afghanistan}}