Zayanderud زاینده رود

Zāyandé-Rūd or Zāyanderūd (Persian: زاینده رود, from زاینده [zɑːjændɛ] “life giver” and رود [rʊːd] “river”), also spelled as Zayandeh-Rood or Zayanderood, is the largest river on the central plateau of Iran, Isfahan Province.

The Zayandeh starts in the Zagros Mountains and flows 400 kilometres (200 mi) eastward before ending in the Gavkhouni swamp, a seasonal salt lake, southeast of Esfahan city. The Zayandeh has significant flow all year long, unlike many of Iran's rivers which are seasonal. The Zayandeh is spanned by many historical Safavid era bridges, and flows through many parks.

The Zayandeh River basin has an area of 41,500 square kilometres (16,000 sq mi), altitude from 3,974 metres (13,038 ft) to 1,466 metres (4,810 ft), an average rain fall of 130 millimetres (5 in) and a monthly average temperature of 3 °C (37 °F) to 29 °C (84 °F). There are 2,700 square kilometres (1,000 sq mi) of irrigated land in the Zayandeh River basin, with water derived from the nine main hydraulic units of the Zayandeh River, wells, qanat and springs in lateral valleys. Zayandeh River water gives life to the people of central Iran mainly in Isfahan and Yazd provinces. Water diverted per person is 240 litres (63 US gallons/53 imp gallons) per day in urban and 150 litres (40 US gallons/33 imp gallons) per day in villages.^[1] The flow of the river has been estimated at 1.2 cubic kilometres (0.30 cu mi) per annum, or 38 cubic metres (1,340 cu ft) per second.

Water use and division

Until the 1960s in Isfahan Province the distribution of water followed the Tomar, a document claimed to date from the 16th Century. The Tomar divided the flow of the Zayandeh River into 33 parts which were then specifically allotted to the eight major districts within the region.^[4] At the district level the water flow was divided either on a time basis, or by the use of variable weirs, so that the proportion could be maintained regardless of the height of the flow.^[4]

For centuries Esfahan city had been an oasis settlement, noted for its surrounding fertile lands and prosperity. Until the 1960s industrial demand for water was minimal, which enabled the scarce water resources to be utilized primarily for agriculture. With a growing population within the basin, and rising standards of living particularly within the city, the pressure on water resources steadily increased until the division of water Tomar was no longer feasible. The creation of large steel works and other new industries demanded water.^[2]

The Chadegan Reservoir dam project in 1972 was a major hydroelectric project to help with stabilizing water flow and generate electricity. The dam was initially named Shah Abbas Dam after Shah Abbas I, the most influential king of the Safavid dynasty, but it was changed to Zayandeh Dam after the Islamic revolution in 1979. Since 1972, the Chadegan Reservoir has helped prevent seasonal flooding of the Zayandeh River.

80% of the Zayandeh's extracted water is used for agriculture, 10% for human consumption (drinking and domestic needs of a population of 4.5 million), 7% for industry (like the Zobahan-e-Esfahan and Foolad Mobarekeh steel companies and Isfahan's petrochemical, refinery and power plants) and 3% for other uses. There have been a number of tunnel projects (Koohrang) to redirect water from the Karun river (Iran's largest river that also starts in the Zagros Mountains), to the Zayandeh. These have helped provide water for the growing population and new industries in both Isfahan and Yazd provinces.

http://en.wikipedia.org/wiki/Zayandeh_rud