TheHrazdan (Armenian:Հրազդան գետ,Hrazdan get) is a major river and the second largest inArmenia. It originates at the northwest extremity ofLake Sevan and flows south through theKotayk Province and Armenia's capital,Yerevan; the lake in turn is fed by several streams.[1][2] In theArarat plain it joins theAras river along the border withTurkey. It join as a left tributary theKura river, which then flows into the Caspian Sea.
A series ofhydro-electric projects have been constructed on the Hrazdan. Its waters are in demand toirrigate crops.[3][4]
The nameHrazdan derives from aMiddle Iranian form ofAvestanFrazdānu, which inZoroastrian mythology is the body of water by whichVishtaspa converted to Zoroastrianism.[8]Frazdānu is composed of the elementsfraz 'elevated, high' anddānu 'river'.Dānu derives from the sameIranian root as a number ofhydronyms in Europe, such asDon,Dnieper,Danube andDniester.[9] The change of word-initialfr- tohr- can be seen in a number of Iranian borrowings into Armenian.[10] The Hrazdan is mentioned inMovses Khorenatsi's history. In the history attributed toSebeos, the formHurazdan is used, while some later Armenian historians use the formHurastan.[11]
Lake Sevan (with 30 rivers contributing to its storage), the largest located in the central part of the country and the Hrazdan River which originates from it, together form the "Sevan-Hrazdan Management Area", which is one of the five sub-basins of the 14 sub-basins of Kura and Araks basins of Armenia. The river originates from the lake at an elevation of 1,900 metres (6,200 ft).[4] The river which flows from the lake in a southern direction passes through a deep gorge as it enters on the western side of the Yerevan city, and then debauchees into the Aras River on the southern side of the city.[19] The geological formations along the river course are made up of lava flows (existing as basalts) generated from three volcanoes in theGegham range. The lava surfaces represent environments that existed in the form of "lakes, river channels and floodplains". The chronology of landscape of the upper most layer of basalts indicates an age of 200,000 years.[20]
The river drains a total catchment area of 2,566 square kilometres (991 sq mi). Precipitation volume is 1572 million cubic metre[4] from an annual rainfall of 257 millimetres (10.1 in) with a maximum of 43 millimetres (1.7 in) in May and a minimum of 8 millimetres (0.31 in) during August. The average temperature recorded in the basin varies from −3 °C (27 °F) in January to 26 °C (79 °F) in July with diurnal variation with the lowest night temperature of −15 °C (5 °F) in January and highest day temperature of 44 °C (111 °F) in July.[19] The total flow in the river is 733 million cubic meter. The regulated outflow into the river, which forms the Ararat Valley, is utilized for irrigation and hydro-power benefits.[4]
A panorama of the Hrazdan River gorge andDavtashen fromArabkir, Yerevan
While the fish species contained in the lake consist of theSevan trout (Salmo ischchan) or “Prince Fish,” siga, crucian, carp, crayfish, bojak (Salmo ischchan danilewskii) and winter bakhtak (Salmo ischchan ischchan) and summer bakhtak (Salmo ischchan aestivalis), the river is reported to have species of crayfish as well as karas andcrayfish in abundance.[23]
The lake waters have been used for irrigation since the 19th century, and from early 20th century hydro-power development has also been implemented. The lake waters were planned to be used through the river for irrigating 100,000 hectares (250,000 acres) in the Ararat Valley out of which an irrigation of 80,000 hectares (200,000 acres) was created. The hydro-power development was planned on the river as theSevan–Hrazdan Cascade involving seven schemes in a 70 kilometres (43 mi) stretch of the river with a total installed capacity of 560 MW with mean annual energy generation of around 500 million kilowatt hours; it is the largest hydro-power generating scheme in Armenia.[3] This scheme was implemented between 1930 and 1962. These are small- and medium-size projects built as run-of-the river power plants. The seven power stations are: Sevan HEP with installed capacity of 34.2 MW with two units completed in 1949; the Hrazdan HEP of 81.6 MW with two units commissioned in 1959; the Argel HEP with installed capacity of 224 MW completed in 1953; the Arzni HEP with capacity of 70.6 MW with installation of 3 units commissioned in 1956; the Kanaker HEP with installed capacity of 100 MW with 6 units completed in 1936; the Yerevan-1 HEP commissioned in 1962 with installation of 44 MW with 2 units; and the Yerevan-3 with capacity of 5 MW with one unit commissioned in 1960. However, priority of release of water from the lake is for irrigation and accordingly the power stations are operated.[3]
The civil works involved construction of diversion works, open canals or tunnels and power house which over the years were in need of substantial rehabilitation as they were all built around the middle of the twentieth century.[3] In 2003, the International Energy Corporation", a Closed Joint Stock Company, acquired the projects from the Public Services Regulatory Commission of the country under a license No. 0108 for generation of electrical energy. Right from the time of acquisition they started rehabilitating the projects to maximize power generation. The works were completed during 2004.[24] The works were carried out under a US$25 million loan from theAsian Development Bank.[25]
The river water is polluted by effluent flows from agricultural, commercial, industrial, and residential development, but particularly by the untreated wastewater from Yerevan. This affects the water quality in the river with dissolved oxygen (DO) levels (less than 5% of the saturated dissolved oxygen level) remaining much lower than the permissible limits. A study carried out in 2008 indicates that a 16 km stretch of the river, from 2 km upstream of the Yerevan wastewater outfalls to 14 km below, is insufficiently aerated to provide a healthy environment for aquatic life.[2]
^abHewsen, Robert H. (1992).The Geography of Ananias of Širak: Ašxarhacʻoycʻ, the Long and the Short Recensions. Reichert. p. 192.ISBN9783882264852....the Turkish Zanga; (Urart: Ildaruni; Arm.: Hrazdan)...
^Maranci, Christina (2018).The Art of Armenia: An Introduction. Oxford University Press. p. 13.ISBN9780190269005.The stele bears a text of forty-seven lines in Urartian cuneiform identifying King Rusa II (r. c. 680–639 BCE), son of Argishti II, and his building and irrigation works, including the construction of a canal from the Ildaruni (Hrazdan) River.
^Lang, David Marshall (1970).Armenia: Cradle of Civilization. London:Allen & Unwin. p. 98.The canal from the Ildaruni (Razdan) river I built.'
^Chalabian, Antranig (1999).Armenia after the coming of Islam. p. 450.He also increased the water capacity of the Hrazdan (Zangu) River, which flows from Lake Sevan to the Araratian plain...
^Nansen, Fridtjof (1922).Reports and Papers on the Work for the Refugees.League of Nations. p. 19....surrounding Erivan, on both sides of the Zanga River, by the waters of that river...
^Kachvoryan, E. A. (February 2007). "The fauna of chironomids and blackflies (Diptera: Chironomidae, Simuliidae) and hydrochemical characteristics of the Hrazdan River (Armenia)".Entomological Review.87:73–81.doi:10.1134/S0013873807010071.S2CID34675406.
