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].

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.

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.

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

Good