Граздан өзені: тарихы, географиясы және су ресурстары

The Hrazdan (, Hrazdan get) is a major river and the second largest in Armenia. It originates at the northwest extremity of Lake Sevan and flows south through the Kotayk Province and Armenia's capital, Yerevan; the lake in turn is fed by several streams. In the Ararat plain it joins the Aras river along the border with Turkey. Its waters join the Kura river, before flowing into the Caspian Sea. A series of hydro electric projects have been constructed on the river. Its waters are in demand to irrigate crops.

The name Hrazdan derives from a Middle Iranian form of Avestan Frazdānu, which in Zoroastrian mythology is the body of water by which Vishtaspa converted to Zoroastrianism. Frazdānu is composed of the elements fraz 'elevated, high' and dānu 'river'. Dānu derives from the same Iranian root as a number of hydronyms in Europe, such as Don, Dnieper, Danube and Dniester. The change of word initial fr to hr can be seen in a number of Iranian borrowings into Armenian. The Hrazdan is mentioned in Movses Khorenatsi's history. In the history attributed to Sebeos, the form Hurazdan is used, while some later Armenian historians use the form Hurastan. The river was called Ildaruni in Urartian. Its name in Turkic languages is Zangu, Zanga, Zangi, or Zengy.

The Sevan Lakes (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
The river drains a total catchment area of Precipitation volume is 1572 million cubic metre 25 species of invertebrates comprising two species of rotifers, 13 species of cladocerans and 10 species of copepods have been recorded in the river. While the fish species contained in the lake consist of the Sevan 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 and crayfish in abundance.

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 in the Ararat Valley out of which an irrigation of was created. The hydro power development was planned on the river as the Sevan–Hrazdan Cascade involving seven schemes in a 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. 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. The works were carried out under a US$25 million loan from the Asian Development Bank.

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.