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Ecoregion Description


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Species Richness


# of Endemic Species


Threats

445: Orumiyeh

Major Habitat Type:

xeric freshwaters and endorheic (closed) basins

Author:

Brian Coad

Countries:

Iran; Turkey

Boundaries:

The ecoregion comprises the drainage basin of Lake Orumiyeh (= Reza’iyeh, Urmia, Urmi, Urumiyeh, or Darya-e Shahi), which lies in northwest Iran. It is bounded by the Caspian Highlands ecoregion [446] to the east and the Upper Tigris-Euphrates basin [442] to the west.

Drainages flowing into:

The basin is endorheic and all rivers terminate in the salt Lake Orumiyeh.

Main rivers or other water bodies:

The basin comprises Lake Orumiyeh, brackish marshes, and tributary rivers. Prominent perennial streams include the Zarrineh River (230 km long), entering from the south with the Tata’u or Simineh River (145 km) as a major tributary; the saline Aji Chay or Talkheh (= bitter) River from the east, draining the flanks of Kuhha-ye Sabalan at 4810 m; Kuh-e Sahand at 3710 m; and smaller streams from the west. Lake Kobi (= Ghopi) is a Ramsar site lying at 1240 m altitude in this basin. The Shur Gol and the Yadergarlu and Dorgeh Sangi endorheic lakes are south of Lake Orumiyeh and northwest of Mahabad at 1290 m. Other small lakes and associated marshes are present in this basin. Gori Gol or Lake Gory at 37º5’N, 46º42’E is a fresh to brackish lake near Tabriz, occupying 120 ha at 1950 m asl. Qanats and dams are found throughout the basin.

Topography:

The area surrounding the lake includes some marshes and smaller lakes as noted above. The Sahand and Sabalan mountains reach 3710 and 4810 m, respectively, but much of the topography is rolling landscape.

Climate:

The ecoregion has a semi-arid climate, with a mean annual temperature of 9.6 ºC. The average minimum temperature during the coldest month is -8 ºC and average temperature during the hottest month is 30 ºC. Mean annual precipitation is around 400 mm.

Freshwater habitats:

Lake Orumiyeh lies at about 1297-1300 m, is about 128-149 km long and 40-60 km wide. The lake has a surface area of 4750-6100 km2, a volume of 29.4 km3, a mean depth of 4.9-6.0 m, a maximum depth of 16 m, and a temperature range of -1.3−27.5°C. The lake level can rise as much as 2 m in one season, as it did in the winter of 1968-1969. It is a sodium chloride-sulphate system with a salinity up to 310.79 gl-1 (but mostly 217-235gl-1), and consequently is fishless. Brackish marshes in the northeast, northwest, and southern shores probably support some fishes as do all of the tributary rivers. The rivers are fed by seasonal snowmelt and rainfall recharge of groundwater. Lakes and marshes are also fed from local springs.

Terrestrial Habitats:

Much of the semi-arid steppe forest has been converted to wheat fields, but there are some remnants of pistachio forests on an island in the lake. The more forested areas occur to the west of the lake, whereas steppe is dominant to the east.

Fish Fauna:

The fauna comprises only around ten known species, most of which are cyprinids. The fauna has been well-surveyed so new taxa are unlikely to be found except possibly in Balitoridae. Relationships lie with the neighboring Caspian Sea basin.

Description of endemic fishes:

Almost half of the taxa are endemic, although there are no endemic genera. These species include Acanthalburnus urmianus, Alburnus atropatenae, Petroleuciscus ulanus, and Kura gudgeon (Romanogobio persus).

Other noteworthy fishes:

The large Wels catfish (Silurus glanis) is found in this basin, as well as a distinct form (undescribed) of salmonid (the Liqvan Chai trout).

Other noteworthy aquatic biotic elements:

Lake Orumiyeh is the largest natural habitat for brine shrimp in the world, which since 2000 have been harvested, processed, and used to feed Caspian sturgeon in hatcheries. Lake Orumiyeh is also an important area for waterfowl including American flamingo (Phoenicopterus rubber) and great white pelican (Pelecanus onocrotalus) among others (Scott 1995).

Evolutionary phenomena:

The lake, located at 1275-1295 m asl, was formed during the late Pliocene-Pleistocene and may well have had a Pleistocene connection to the Caspian Sea basin, although this is in dispute. Pleistocene shorelines from 30 to 115 m above the present level have been confirmed, and the lake covered twice its present area, but this would not permit an external discharge. Benches at levels of about 1800 m, 1650-1550 m, and 1500-1360 m may represent shorelines, and a level of about 1570 m would have had an outlet to the Aras River basin through the Kara-tepe Pass in the northwest and across the plain near Khvoy. Saadati (1977) suggests two connections with the Caspian Sea: an early one in the Pliocene to early Pleistocene resulting in endemic species and a later one in the late Pleistocene resulting in species that are the same as the Caspian or only subspecifically distinct. Stream capture may have allowed the entry of some species in recent times as evidenced by a population of brown trout (Salmo trutta).

Justification for delineation:

Lakes Gori, Kobi, Orumiyeh, Shur Gol, Yadergarlu, and Dorgeh Sangi are Ramsar sites. The basin has a high degree of endemicity.

Level of taxonomic exploration:

Good

References/sources:

Coad, B. W. (2002). "Freshwater Fishes of Iran" (www.briancoad.com).

Saadati, M. A. G. (1977). "Taxonomy and distribution of the freshwater fishes of Iran" Unpublished Thesis. Colorado State University: Fort Collins

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.

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