Contact Us|Site Map


Ecoregion Description


View global map

Species Richness


# of Endemic Species


Threats

702: Helmand - Sistan

Major Habitat Type:

xeric freshwaters and endorheic (closed) basins

Author:

Brian Coad

Countries:

Afghanistan; Iran; Pakistan

Boundaries:

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 [701], to the east by Yaghistan [704] and Indus Himalayan Foothills [705], to the north by the Upper Amu Darya [631], and to the west by the Kavir & Lut Deserts [448].

Drainages flowing into:

The rivers flow into the endorheic lakes of the Sistan depression.

Main rivers or 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.

Topography:

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.

Climate:

The Sistan depression has a true desert climate, with maximum temperatures that exceed 43 ºC in summer and mean annual precipitation less than 100 mm. This is in contrast to the cold desert and cold semi-arid climate of the western Hindu Kush.

Freshwater habitats:

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.

Terrestrial Habitats:

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.

Fish Fauna:

The fauna comprises only two families, Cyprinidae and Balitoridae, with nine and thirteen species respectively. The area of the low-lying lakes is unusual in having species of schizothoracine cyprinids or snow trouts, a group of fishes normally found at high altitudes in the Himalayas.

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.

Other noteworthy aquatic biotic elements:

Other biotic elements have not been extensively surveyed, but presumably include endemic or unique aquatic invertebrate taxa in the midst of a desert environment.

Evolutionary phenomena:

The native ichthyofauna comprises a mixture of endemic species, species related to or conspecific with high-altitude species from Central Asia, and species from Baluchestan in the wider sense. There is little relationship to species from Iran to the west. The schizothoracine fauna are particularly characteristic; they originated either by descent from higher altitudes during the Pleistocene glaciations or are autochthonous as the forms at high altitudes in the Pamirs and Himalayas rose with mountain building.

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:

Good

References/sources:

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. (Ed.) (1995). "A Directory of Wetlands in the Middle East" Gland, Switzerland and Slimbridge, U.K: IUCN and International Waterfowl and Wetlands Research Bureau.

The Nature Conservancy World Wildlife Fund
©WWF/TNC 2008 | Copyright Notice | Sponsors |Last updated: May 15, 2014