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Iran (Islamic Republic of)
Of the average rainfall volume of 376 km3/year an estimated 66 percent evaporates before reaching the rivers. The total long-term total renewable water resources are estimated at 137.5 km3 of which about 9 km3/year are external water resources (Table 2). Internal renewable water resources are estimated at 128.5 km3/year. Surface runoff represents a total of 97.3 km3/year, of which 5.4 km3/year come from drainage of the aquifers, and groundwater recharge is estimated at about 49.3 km3/year, of which 12.7 km3/year are obtained from infiltration in the river bed, giving an overlap of 18.1 km3/year. The Islamic Republic of Iran receives 6.7 km3/year of surface water from Afghanistan through the Helmand River. The flow of the Araks River, at the border with Azerbaijan, is estimated at 4.63 km3/year. The surface runoff to the sea and to other countries is estimated at 55.9 km3/year, of which 7.5 km3/year to Azerbaijan (Araks) and 10 km3/year from affluents of the Tigris to Iraq. About 24.7 km3/year flows from the Karun into Iraq, but since this is just before it discharges into the sea, it does not count as inflow into Iraq.
The Islamic Republic of Iran is divided into 6 main and 31 secondary catchment areas. The 6 major basins are: the Central Plateau in the centre (Markazi), the Lake Oroomieh basin in the northwest, the Persian Gulf and the Gulf of Oman basin in the west and south, the Lake Hamoon basin in the east (Mashkil Hirmand), the Kara-Kum basin in the northeast (Sarakhs) and the Caspian Sea basin in the north (Khazar) (Figure 1). All these basins, except the Persian Gulf and the Gulf of Oman basin, are interior basins. Almost half of the country’s renewable water resources are located in the Persian Gulf and the Gulf of Oman basin, which only covers one fourth of the country (Table 3). On the other hand the Markazi basin, covering over half of the country, has less than one third of the total renewable water resources. With an area of 424 240 km2, the Caspian Sea is the largest landlocked water body in the world and its surface lies about 22 metres below sea level.
There are several large rivers, but the only navigable one is the Karun, the others being too steep and irregular. The Karun River, with a total length of 890 km, flows in the southwest of the country to the Shatt al Arab, which is formed by the Euphrates and the Tigris in Iraq after their confluence. The few streams that empty into the Central Plateau dissipate into the saline marshes. All streams are seasonable and variable. Spring floods do enormous damage, while there is little water flow in summer when most streams disappear. Water is however stored naturally underground, finding its outlet in subterranean water canals (qanats) and in springs. It can also be tapped by wells.
Dams have always played an important role in harnessing precious Iranian water reserves and the long-term objective of the Islamic Republic of Iran’s water resources development plan is based on the control and regulation of water resources through dams. In 2006, 94 large storage dams with a total capacity of 31.6 km3 were operating and 85 large dams with a capacity of 10 km3 were under construction. Aside from hydropower, dams also play an important role in flood control through the routing of floods. Several reservoirs behind the dams would seem to offer good sailing and water-skiing facilities, but have not been used for recreation so far.
In 2001, there were 39 wastewater treatment plants with a total capacity of 712 000 m3/day, treating the wastewater produced by a population of 3.8 million. The wastewater actually treated was around 130 million m3/year (Mahmoodian, 2001). Some 79 treatment plants with a total capacity of 1.917 million m3/day were under construction and 112 treatment plants with a total capacity of 1.590 million m3/day were being studied for completion by the year 2010.
In 2002, the total installed gross desalination capacity (design capacity) in the Islamic Republic of Iran was 590 521 m3/day or almost 215.5 million m3/year (Wangnick Consulting, 2002). The desalinated water produced was around 200 million m3 in 2004.