Helmand - Sistan
Brian Coad, Jennifer Hales
Major Habitat Type
Xeric freshwaters and endorheic (closed) basins
Drainages flowing into
The rivers flow into the endorheic lakes of the Sistan depression.
Main rivers to other water bodies
The main water bodies are the freshwater lakes (or hamuns) in Sistan and the rivers that feed the lakes, principally the Helmand. Other rivers flowing from Afghanistan are the Harut, Khospas, and Khash, but their flow is minor and intermittent compared to the Helmand.
The ecoregion comprises an endorheic drainage basin in eastern Iran and central-western Afghanistan, with rivers draining the Hindu Kush of Afghanistan. It is bounded to the south by the Baluchistan ecoregion , to the east by Yaghistan  and Indus Himalayan Foothills , to the north by the Upper Amu Darya , and to the west by the Kavir & Lut Deserts .
The area surrounding the lakes is arid desert plain. The Sistan depression lies at 427 m. The principal river is the Helmand (or Hirmand), which flows from the Paghman Mountains just west of Kabul to end in Sistan after a journey of 1400 km. Snow and rain in the Hindu Kush Mountains ultimately reaches Sistan from heights of 5300 m. The Helmand is the most important river between the Tigris and the Indus and drains an area of 386,000 km2.
The freshwater habitats comprise the vast hamun or swamp comprising open freshwater lakes, reed beds or neizar, and the rivers that feed the lakes. The swamps are a major oasis of fresh water surrounded by hundreds of kilometers of arid plains. The only other fresh water is found in a few isolated springs. The basin remains fresh, unlike other terminal sumps, because of overflow to the Gaud-e Zirreh, a salt flat, which gives a flushing effect and prevents build up of salts. The extent of the marshes and lakes is heavily dependent on the flood regime of the Helmand River, which varies naturally to the extent that the lakes dry out in some years, with fish recolonizing from the rivers. This natural cycle is exacerbated by dam construction in Afghanistan.
The lakes and the watercourses of the rivers are surrounded by rock and sand deserts with sparse or no vegetation. The upper reaches of the tributary rivers lie in xeric woodlands, conifer forests, and alpine meadows of the western end of the Hindu Kush Range.
Description of endemic fishes
Around 40% of the species in the ecoregion are endemic, of which four are in the genera Paracobitis (P. boutanensis, P. ghazniensis, P. rhadinaeus, P. vignai). There are no endemic genera, but the snow trout Schizothorax zarudnyi (Cyprinidae) is endemic to the Sistan lakes. Other endemics include Schizocypris altidorsalis in Sistan, Nemacheilus kullmanni in the Ab-e-Nawar spring, and Schistura alta and Triplophysa farwelli in the Helmand River drainage.
Other noteworthy fishes
Exotic species of fish are now common and include goldfish, grass carp, and silver carp.
Justification for delineation
The south end of Hamun-e Puzak and the contiguous Hamun-e Sabari (or Lake Hamun) are Ramsar sites. The Lake Hamun Ramsar site is on the threatened list of national parks. The Sistan basin contains endemic taxa of fish and is an important breeding, staging, and wintering area for waterfowl.
Level of taxonomic exploration
- Coad, B. W. (2002). "Freshwater Fishes of Iran" (www.briancoad.com).
- Mansoori, J. (1994). "The Hamoun Wildlife Refuge" Heidelberg: Max Kasparek Verlag.
- Scott, D. A. (1995) A Directory of Wetlands in the Middle East IUCN and International Waterfowl and Wetlands Research Bureau : Gland, Switzerland and Slimbridge, U.K
- Hijmans, R. J., S. Cameron and Parra., J. (2004) \WorldClim, Version 1.4 (release 3). A square kilometer resolution database of global terrestrial surface climate\ "<"[http://www.worldclim.org]">" (16 July 2009)
- Peel, M. C., Finlayson, B. L. and McMahon, T. A. (2007). "Updated world map of the Köppen-Geiger climate classification" Hydrology and Earth System Sciences 11 pp. 1633–1644.