Geography and Population
The Islamic Republic of Iran covers a total area of about 1.65 million square kilometers (km2) and is bordered by Azerbaijan, the Caspian Sea and Turkmenistan to the north, Afghanistan and Pakistan to the east, the Gulf of Oman and the Persian Gulf to the south, and Iraq and Turkey to the west. About 52% of the country consists of mountains and deserts and some 16% of the country has an elevation of more than 2,000 meters (m) above sea level. The largest mountain massif is that of the Zagros, which runs from north-western Iran first southwards to the shores of the Persian Gulf and then continues eastwards till the most south-eastern province. Other mountain ranges run from the north-west to the east along the southern edge of the Caspian Sea. Finally, along the eastern frontier of Iran several scattered mountain chains exist. The Central or Interior Plateau is located in between these mountain chains and covers over 50% of the country. It is partly covered by a remarkable salt swamp (kavir) and partly by areas of loose sand or stones with stretches of better land near the foothills of the surrounding mountains.
The cultivable area is estimated at about 51 million hectares (ha), which is 31% of the total area. In 1993 about 18.5 million ha, or 36% of the cultivable area, were considered usable for agriculture, while 14.4 million ha were actually cultivated. Of this area, 12.8 million ha consisted of annual crops and 1.6 million ha of permanent crops. About 70% of the landholders possess less than 5.5 ha (of which on average 2.13 ha irrigated and 3.25 ha rainfed).
The total population is about 67.3 million (1995), of which 41% is rural. The average population density is 41 inhabitants/km2, but it ranges from less than 10 in the eastern part of the country up to more than 150 in the Gilan province, located in the Caspian Plain in the north, which is by far the most densely populated region in the country. In the Tehran province, where the capital is located, the population density reaches 400 inhabitants/km2. The annual demographic growth rate was estimated at 3.4% over the period 1980-1990 and at 2.6% over the period 1990-1994. In 1991, agriculture employed around 29% of the total labor force and accounted for 21% of gross domestic product (GDP), while in 1992 it accounted for 23% of GDP. In 1989, agriculture accounted for 47% of non-oil exports.
Climate and Water Resources
The climate of Iran is one of great extremes due to its geographic location and varied topography. The summer is extremely hot with temperatures in the interior rising possibly higher than anywhere else in the world, certainly over 55°C has been recorded. In winter, however, the great altitude of much of the country and its continental situation result in far lower temperatures than one would expect to find in a country in such low latitudes. Minus 30°C can be recorded in the north-west and minus 20°C is common in many places.
Annual rainfall ranges from less than 50 millimeters (mm) in the deserts to more than 1,600 mm on the Caspian Plain. The average annual rainfall is 252 mm and approximately 90% of the country is arid or semiarid. Overall, about two-thirds of the country receives less than 250 mm of rainfall per year.
Iran can be divided into the following major river basins: the Central Plateau in the middle, the Lake Orumieh basin in the north-west, the Persian Gulf and the Gulf of Oman in the west and south, the Lake Hamoun basin in the east, the Kara-Kum basin in the north-east and the Caspian Sea basin in the north. 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 meters below sea level. The rainfall characteristics of the above basins are summarized in the table below.
|Rainfall in the major basins in Iran|
|Basin||Total area (km2)||As % of total area||Rainfall (mm/year)||Rainfall (km3/year)||As % of total rainfall|
|Persian Gulf and Gulf of Oman||431,000||26||366||158||38|
|Lake Hamoun and Kara-Kum||150,000||9||142||21||5|
All these basins, except the Persian Gulf and Gulf of Oman, are interior basins. There are several large rivers, the only navigable one of which is Karun, the others being too steep and irregular. The Karun river, with a total length of 890 kilometers (km), flows in the south-west of the country to the Shatt El-Arab, which is formed by the Euphrates and the Tigris 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 springs. It can also be tapped by wells.
Internal renewable water resources are estimated at 128.5 km3/year. Surface runoff represents a total of 97.3 km/year, of which 5.4 km3/year comes from drainage of the aquifers, and groundwater recharge is estimated at about 49.3 km3/year, of which 12.7 km3/year is obtained from infiltration in the river bed. Iran receives 6.7 km3/year of surface water from Pakistan and some water from Afghanistan through the Helmand river. The flow of the Arax 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. The total safe yield of groundwater (including non renewable water or unknown groundwater inflow from other countries) has been estimated at 49.3 km3/year.
Dams have always played an important role in harnessing Iran's precious water reserves and the long-term objective of Iran's water resources development plan is based on the control and regulation of water resources through dams. In 1994, 27 storage dams were in operation with a total regulation capacity of 39.2 km3. At the same time, 24 storage dams were under construction with a design regulation capacity of 11.5 km3. In 1993, the annual electricity production from dams was 25,116 gigawatt hours (GWH), which is 33% of the total energy production of the country. Dams also play an important role in flood control through routing of floods. Several reservoirs behind the dams seem to offer good sailing and water-skiing facilities, but have not been used for recreation so far.
The total agricultural, domestic, and industrial water withdrawal was estimated at about 70 km3 in 1993 (of which 91.6% is used for agricultural purposes, 6.3% for domestic use and 2.1% for industrial use). Although this is equal to 51% of the actual available renewable water resources, current annual abstraction from aquifers (from 49 km3 in 1990 up to 57 km3 in 1993) is already more than the estimated safe yield (46 km3). Further to these 70 km3, another 39 km3 of water is used annually, of which about 20 km3 for electricity production, 11 km3 for flood control, 2 km3 for environmental protection (control of downstream parts of rivers), while the remaining part is considered to be surplus water.
Irrigation and Drainage Development
The problem of water supply has been a constant preoccupation since the beginning of the country's history, thousands of years ago. Its inhabitants learned to design and implement efficient techniques for harnessing limited water resources and for irrigation. Apart from the qanat, which was a major source of irrigation and domestic water supply for centuries, Iranians have in the past built dams of various types and weirs. Some of these head control structures, built as long as 1000 years ago, are still in good condition.
Agricultural land availability is not a major constraint in the development of Iranian agriculture. The major constraint is the availability of water for the development of these lands. The irrigation potential, based on land and water resources, has been estimated at about 15 million hectares (ha), or 29% of the cultivable area. However, this would require optimum storage and water use.
In 1993 out of 14,382 million ha of cultivated land 7,264 million ha, or 51%, were equipped for full or partial control irrigation. Annual crops covered 5,699 million ha and permanent irrigated trees covered 1,565 million ha. In addition, flood recession cropping is practiced on an area of about 10,000 ha in the southwest.
Surface irrigation techniques are used on 98.75% of the area equipped for irrigation and 1.25% benefits from a pressurized irrigation system. About half the area is irrigated from groundwater, including spring water. According to the landholding and technologies which are used, the farming systems are grouped as: small farms (< 10 ha) 47%, medium size farms (10-50 ha) 43%, and large farms (>50 ha) 10%.
The cost of surface irrigation development varies from $US 2,300/ha for large to $US 2,500/ha for medium and $US 2,600/ha for small schemes. Average operation and maintenance costs are estimated at $US 130,175 and 60 per ha and per year respectively. The cost of micro-irrigation and sprinkler irrigation development is estimated at about $US 2,200 and 1,200/ha. The average price of water delivered to farmers by government is $US 0.2 to 0.8/1,000 m3, while the cost of withdrawal of groundwater by the farmer is $US 5 to 9/1,000 m3 and the cost for regulating surface water in existing projects is $US 3 to 5 per 1,000 m3. This means that the government heavily subsidizes delivered water, which is probably one of the main reasons for the low irrigation efficiency throughout the country.
On-farm application rates in the country are rather high and in general irrigation has a low efficiency on average at the national level. Major causes of inefficiency include: careless operation, poor maintenance, negligible water prices, fragmentation of responsibilities among different governmental agencies, and inadequate training of farmers. Low irrigation efficiency causes waterlogging and salinization in the irrigated areas, which are a major problem in Iran. No comprehensive study has been undertaken regarding the extent of irrigation-induced salinity, but according to an estimate for the year 1974 about 38% of the irrigated area had soils with considerable salinity and drainage problems. Over 2 million ha are estimated to be salt-affected or waterlogged at present.
By far the most important irrigated crop is wheat covering almost one-third of the total irrigated area, followed by irrigated fruit trees, covering one fifth of the total area. Other major irrigated crops are barley, rice, vegetables, and nurses wheat is also by far the most important rainfed crop covering 4.47 million ha, or almost two-thirds of the rainfed area. The yield for irrigated wheat was estimated at 2.78 tons/ha in 1993 against 0.95 tons/ha for rainfed wheat.
According to the water legislation, three ministries are in charge of water resources assessment and development:
- The Ministry of Energy (MOE) has two responsibilities: energy supplies and water resources. In the field of irrigation, it is in charge of the construction of large hydraulic works, including dams and primary and secondary irrigation and drainage canals for the distribution of water. Within MOE, the Water Affairs Department (WAD) is responsible for overseeing and coordinating planning, development, management, and conservation of water resources. Fourteen publicly owned Regional Water Authorities (RWA), reporting directly to MOE, are responsible for feasibility studies, project execution, and subsequent management. The operation and maintenance of primary and secondary irrigation and drainage canals are operated by operation and maintenance corporations affiliated to MOE.
- The Ministry of Agriculture (MOA) is responsible for supervising rainfed and irrigated crop development. It is in charge of subsurface drains, tertiary and quaternary canals as well as on-farm development and irrigation techniques, planned and operated by the Provincial Agricultural Organizations and the Deputy Ministry for Infrastructure Affairs of the Ministry of Agriculture.
- The Ministry of Jihad-e-Sazandagi (MOJ) deals with watershed management and rural development.
Trends in Water Resources Management
Agriculture is one of the main priorities in national development plans. The annual increase in irrigated land over 15 years (1978-1993) was 3.8% along with a 4.4% annual increase for agricultural water supply. An increase of 500,000 ha of irrigated land and an increase of 10 km3/year of agricultural water supply was planned in the second national five-year plan (1995-2000).
At present, a big gap exists between water delivery from the main canals and water application in the field. Compared to the large investments for water resources development, little has been done to improve irrigation water use at the farm level. Water is delivered to old traditional irrigation canals and on-farm conveyance and the use of irrigation water is generally rudimentary and wasteful. The use of earth bunds, unlined canals, and poor leveling combined with low water charges have resulted in very low levels of water conveyance and use efficiencies (30% as a national average) and caused the emergence of serious drainage problems.
A fundamental review of the organizational chart and institutional changes were made to improve this situation. Since 1992, the Deputy Ministry for Infrastructure Affairs of the Ministry of Agriculture created five departments: farm development, pressurized irrigation systems, water supply, hydraulic constructions, and operation and maintenance.
The government policy includes:
- an increase in irrigation efficiency by changing the surface irrigation techniques to pressurized irrigation (2 million ha were planned for the year 1995-2000);
- the establishment of a land Bank to provide loans for on-farm development projects;
- a change in water pricing and delivery methods;
- large-scale privatization.
- Water profile of Iran, Food and Agriculture Organization.
- World Factbook: Iran, Central Intelligence Agency.
- Bureau of Information and Statistics. 1994. Agricultural Statistics Yearbook 1993. Deputy Ministry of Plan and Project, Ministry of Agriculture.
- Bureau of Operation and Maintenance of Dams and Irrigation Networks. 1995. Water utilization in the year 1993. Deputy Ministry of Water Affairs, Ministry of Agriculture.
- Deputy Ministry for Infrastructure Affairs. 1991. Summary of the social and agricultural economy of Iran. Ministry of Agriculture.
- Keshavan, M.A. 1993. Improvement of farm level infrastructures. Deputy Ministry for Infrastructure Affairs. Ministry of Agriculture.
- Shakiebie. 1994. Seventh Iranian National Seminar on Irrigation and Drainage. IRNCID, Ministry of Energy.
- Statistical Centre. 1994. Yearly Statistical Book 1993. Plan and Budget Organization.
- Water and Sewage Engineering Co. Situation of water and wastewater in the country in 1992. Ministry of Energy.
- World Bank. 1993. Staff appraisal report: Irrigation improvement project. Report No. 11393-lRN.
- Yekom Consulting Engineers. 1995. Cost of Irrigation and Drainage Projects - Tender Documents.
Disclaimer: This article is taken wholly from, or contains information that was originally published by, the Food and Agriculture Organization. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the Food and Agriculture Organization should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.