Lake Orumiyeh (= Reza'iyeh, Urmia, Urmi, Urumiyeh or Darya-e Shahi) lies in north-west Iran and is the only Iranian lake large enough to appear on general maps of the world. This lake is a Ramsar Site and includes Orumiyeh National Park. Brackish marshes in the northeast, northwest and southern shores probably support some fishes but the lake itself is too salty.

Orumiyeh lies at about 1275-1300 m (accounts vary), is about 128-149 km long and 40-60 km wide. This thalassohaline lake has a surface area of 4750-6100 sq km, a volume of 29.4 cu km, 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. 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 340.0 gl^-1 (but mostly 217-235gl^-1) and consequently is fishless (Abich, 1856; von Seidlitz, 1858; Rodler, 1887; De Mecquenem, 1908; Plattner, 1955; Vladykov, 1964; Kelts and Shahrabi, 1986; Ghaheri et al., 1999; www.neda.net/inwm/no.6/english/geology/geology01.html, downloaded 10 July 2000; Van Stappen et al., 2001; Eimanifar and Mohebbi, 2007; Karbassi et al., 2010). Initially the lake was probably fresh (Admiralty Naval Staff, 1918). A causeway has divided the lake into two parts since 1989; a gap allows a limited exchange between the two parts. Its drainage basin approaches 57,000 sq km (or 51,786 sq km, authors differ) and the lake is the terminal basin for a number of streams and rivers. Annual inflow is 6900 x 10⁶ m³ (Ghaheri et al., 1999). During spring runoff a freshwater plume covers large areas over the saline lake near river mouths. Prominent perennial streams include the Zarrineh River (230 km long) entering from the south and draining part of the northern Zagros with a range in discharge of 10-510 cu m per second 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 (38°15'N, 47°49'E) and Kuh-e Sahand at 3710 m (37°44'N, 46°27'E), and the smaller streams from the west such as the Zowla (= "Zola") Chay (84 km), Nazlu Chay (85 km), Shahr (= "Shaher") Chay (70 km), Baranduz Chay (70 km) and Gadar (= "Qader") Chay (100 km) (Günther, 1899). Both the Zarrineh and the Talkheh exceed 200 km in length. The Talkheh River has a hardness of 820 mg/l according to Surber (1969), who also gives values of total alkalinity and calcium-magnesium hardness for a number of streams and lakes around Tabriz. The Talkheh floods extensively in the spring and forms large marshes. Most streams were relatively hard like the Talkheh although some were soft such as the Basmenj Chay draining Kuh-e Sahand at 70 mg/l.

Lake Kobi (= Ghopi) is a Ramsar Site lying at 36°57'N, 45°52'E and 1240 m altitude in this basin. It is south of Lake Orumiyeh and northeast of Mahabad. It comprises the fresh to brackish lake and associated but discontinuous marshes of about 1200 ha. The endorheic lake is shallow with a maximum depth of 1.5 m and a mud bottom. It is fed by precipitation and springs, and when full floods marshes to the north. It freezes over in winter. The lake is eutrophic and has reedbeds of Phragmites communis and abundant submerged vegetation. Livestock grazing and wildfowl hunting occur.

The Shur Gol and the "Yadegarlu" (= Yadergarlu) and "Dorgeh Sangi" endorheic lakes are at 37°00', 45°26-35'E south of Lake Orumiyeh and northwest of Mahabad at 1290 m are also a Ramsar Site comprising 2500 ha of lakes and associated marshes. They are fed by precipitation, springs and small streams. Shur Gol at 2000 ha is surrounded by the Hassanlu Marshes. Its water is brackish to saline. The eutrophic marshes flood in fall and winter and have abundant submerged vegetation. "Yadegarlu" is a shallow freshwater lake of 350 ha with abundant submerged vegetation and a surrounding of eutrophic sedge marshes. It may dry out in summer. It apparently suffered in the Iran-Iraq war (Jones, www.ramsar.org/lib_dir_2_3.htm, downloaded 4 April 2000) and may be deleted as a Ramsar Site. "Dorgeh Sangi" is 150 ha in extent and is a shallow freshwater and eutrophic lake. All three lakes may freeze over in winter. Reed cutting, grazing and waterfowl hunting occurs in this complex and some drainage of wetlands for agriculture may occur (Khan et al., 1992).

"Gerde Gheet" (Gordeh Git) and "Mamiyand" (= Meimand?) at 37°02'N, 45°40'E are freshwater marshes south of Lake Orumiyeh and north of Mahabad occupy 500 ha at 1300 m. The marshes are covered by Phragmites. Waterfowl hunting occurs here and some livestock grazing.

The "Ghara Gheshlaq" freshwater marshes at 37°10'N, 45°50'E occupy 400 ha at 1290 m south of Lake Orumiyeh and north of Mahabad. The water is about 1 m deep, eutrophic and freezes over in winter. Large parts of these marshes were drained by the "Mahabad Multipurpose Drainage and Irrigation Project" in the 1970s despite environmental concerns. Cornwallis (1976) notes both the draining of these marshes and the cessation of freshwater discharge from the Mahabad River. He also points out the likelihood of chemical contamination from agriculture, choking by vegetation and the probable use of herbicides. He recommends introduction of Ctenopharyngodon idella and Hypophthalmichthys molitrix. The marshes have been proposed as a Ramsar Site.

Lagoons in the Mahabad area dried in the year 2000 (www.irna.com/newshtm/eng/05142727.htm, IRNA, 26 July 2000).

Gori Gol or Lake Gory at 37°5'N, 46°42'E is a fresh to brackish lake near Tabriz occupying 120 ha at 1950 m. Depth is 2-3 m on average. It is a Ramsar Site (World Conservation Monitoring Centre, 1990; Scott, 1995). It is fed by precipitation, springs and small streams, with overflow through a small stream. The lake freezes over in winter. The submerged vegetation is abundant and there are extensive reedbeds of Phragmites communis, Juncus, Carex and Scirpus. It is under pressure from the population of the major city of Tabriz through sport fishing and wildfowl hunting as well as reed cutting and cattle grazing.

Qanats are found in this basin where surface water is saline. About 225 million cu m of water are produced annually by qanats and wells on the northern and eastern coast of the lake (Alamouti, 1966). Dams are found on the Zarrineh River and on the river which flows through Mahabad paralleling the Zarrineh. The Mahabad Dam has a fish catch of 130 tons (sic) annually and 300,000 fingerlings (species unspecified) were stocked to save the fish reserves from possible extinction (IRNA, 7 January 1999). The Mahabad reservoir has a leech fauna (Codonobdella trunata, Parcanthobdella livanowi, Baicalobdella torquata, Piscicola geometra) which may affect local fish farms and fish populations elsewhere if fish are transplanted (Abdi, 1999: www.mondialvet99.com, downloaded 31 May 2000). The Nowruzlu Dam on the Zarrineh is at 36°55'N, 46°10'E, occupying 1000 ha at 1260 m. It is water storage reservoir with heavy input from surrounding farming activities. The Alavian Dam near Maragheh is 80 m high, 935 m long and has a reservoir of 145 million cu m (http://netiran.com/news/IRNA/html/951214IRGG11.html). The Nahand Reservoir Dam northeast of Tabriz was inaugurated in 1995 with a capacity of 30 million cu m and a second dam, the Shahid Madani also near Tabriz, was under construction. Other dams include those at Ahar, Tabriz, Hashtrud, Hasanlu, Mianeh (= Onligh) and Heris which were scheduled to be completed in the period 1995-2000 (http://netiran.com/news/TehranTimes/95121601TTEC.html and www.irna.com/newshtm/eng/12003142.htm, IRNA, 2 July 2000). ? check basins for dams

The Hassanlou Reservoir Dam at Naqadeh was to open in 1998 with a height of 10 m, a crest of 5160 m (sic) and a capacity of 107 million cu m (http://netiran.com/news/IRNA/html/950915IRGG06.html).

A total of 6 reservoir dams and 10 dams for re-directing water flow will decrease water input to the lake by 1.04 billion cu m by 2014. The volume of surface water has fallen from 42 to 22 billion cu m since 1995. The lake salt has increased to more than 260g/l, up from about 185 g/l. The lake may well dry up by 2014 (IRNA, 10 September 2001).

Löffler (1993) details the eutrophication threat to this lake since a traffic embankment was built across the lake 35 km north of Orumiyeh in 1990. Untreated sewage from Orumiyeh will pollute the southern part of the lake.

Pollution occurs in various localities on a sporadic basis such as the Godar River in Naqadeh where a fish kill numbering in the thousands was reported (Tehran Times, 18 July 1999). Haji Hassani et al. (2004) found that levels of Ni, Pb and Cu in the Talkheh Rud were higher than acceptable limits for fish culture while Cr and Fe were lower. The river receives waste water from agricultural and industrial activities.

Water reservoirs behind the Mahabad, Miandoab and Shahid Kazemi dams were stocked with 3.6 million fish fry (species not specified) from the Pol-e Dasht Complex in 2000. This aquaculture site has the capacity to produce 4 million fry. West Azarbayjan produces over 600 tons of fish annually (Tehran Times, 2 January 2001).

Lake Orumiyeh is the largest natural habitat for brine shrimp in the world and, since 2000, is has been harvested, processed and used to feed sturgeon in hatcheries (www.worldfishingcompanies.com/html/us/world.report.html?id=1, downloaded 23 October 2001).

The lake was formed during the late Pliocene-Pleistocene and lies at 1275-1300 m and may well have had a Pleistocene connection to the Caspian Sea basin although this is in dispute (Scharlu, 1968; Schweizer, 1975). 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. Berg (1940) reports benches at levels of about 1800 m, 1650-1550 m and 1500-1360 m, which 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 which 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 Salmo trutta population.

Fish farming is extensive in West Azarbayjan. In the Iranian year ending 20 March 2002, 840 tonnes of coldwater fish were produced and 3000 t of warmwater fish (Tehran Times, 24 November 2002).

Günther (1899) details a method of catching fish used in the rivers of this basin. Flour and the pounded berries of Cocculus indicus are mixed with butter to form a stiff paste. Small pellets of the paste are thrown into slow flowing water and after 10-15 minutes, if the fish are feeding, they will begin to swim at the surface in small circles or lie helpless in the shallows and are then easily scooped up. Some fish can recover from the poison. There is no effect on humans if poisoned fish are eaten.

Berg (1940) considers that this basin falls within his assignment of the Iranian shore of the Caspian Sea. Species in common include Leuciscus (= Squalius) cephalus, Barbus lacerta, Gobio persus, Capoeta capoeta, Alburnoides bipunctatus, and Silurus glanis, and Acanthalburnus urmianus is related to A. microlepis. Groombridge (1992) notes that the ichthyofauna of this region is badly in need of re-examination.

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