= Status and New Developments on the Use of Brackish Water for Agricultural Production in the Near Eas

This study, commissioned by the Food and Agriculture Organization of the United Nations (FAO), aims at providing an assessment of brackish water resources and the experiences regarding their use for agricultural production in Iran. Islamic Republic of Iran covers an area of 1,648,195 square kilometers and is the 18th largest country of the world. Approximately, 90 percent of the country is arid and semi-arid. The average annual rainfall ranges from less than 50 mm in the Central Plateau to more than 1600 mm on the Caspian Coastal Plain, with an average of about 250 mm (one-third of the world s average precipitation), and this is under conditions in which 179 mm or 71 percent of rainfall is directly evaporated. Agriculture plays an important role in the national economy of the country. It accounts for almost 13 percent of Iran's GDP, 20 percent of the employed population, 23 percent of non-oil exports, 82 percent of domestically consumed foodstuffs and 90 percent of raw materials used in the food processing industry. Iran is generally a water-short country with abundant land. The cultivable area is estimated at about 51 million hectares (ha) of which 18.5 million ha (36% of the cultivable area) is devoted to horticulture and field crop production. Of these, 6.4 million hectares are under annual irrigated crops, 2 million hectares are under horticultural crops, and about 6.2 million hectares are under annual dryland crops, while the remaining 3.9 million hectares are fallow. Based on the latest estimates given in 2010 the area under annual field crop is 6.4 million hectares, 6.4 million hectares under dryland crops and 2.56 million hectares are under horticultural crops (permanent crops). The main source of water in Iran is precipitation which is predominantly in the form of rainfall (70 percent) except for snow in the high mountains and elevated areas (30 percent). Estimates based on long-term historical databases suggest that about 128.5 km3 of surface water is produced internally in Iran every year. Total precipitation is estimated to be about 397.6 Km3, of which 66 percent (262 Km3) evaporates before reaching rivers. By taking into account the dependency ratio of 6.6 percent, the total actual renewable water resources of the country are estimated to be 137.5 Km3. In 2004, the total water consumption was approximately 93.3 Km3, out of which about 92 percent was used in agriculture (86 Km3), 6.6 percent in municipality (6.18 Km3), and 1.2 percent in industry (1.12 Km3). Of the total water consumption 40.0 km3 comes from surface water, 53.1 km3 from groundwater (qanats and wells) and 0.2 km3 desalinated water. The country s water resources management is confronted with many challenges, such as water scarcity, deterioration of surface and groundwater quality, over exploitation of underground waters and the necessity for more efficient use of these valuable resources. This necessitate for immediate mitigating measures to be taken and long term strategies to be devised in order to prevent the situation from becoming even more disastrous. Volume of saline and brackish surface water resources whose total dissolved salts (TDS) in most of the year is greater than 1500 mg/l is equal to 12.88 Km3 which is about 12 percent of the potential of renewable surface water resources of the country. Of the total brackish and saline surface water resources 8.613 Km3 (about 67 percent) flows in the Persian Gulf and the Gulf of Oman basin, 2.842 Km3 (about 22.1 percent) in the Central Plateau basin, 0 .727 Km3 (about 5.7 percent) in the Caspian Sea basin, 0.514 Km3 (about 4 percent) in the Lake Orumieh basin, 0.0948 Km3 (about 0.7 percent) in the Kara-Kum basin and 0.0035 Km3 (about 0.3 percent) in the Lake Hamoun basin. Total area of brackish groundwater resources is 350,222 Km2 with yearly exploiting volume of 13.7 Km3. In other words, considering yearly withdrawal of 53.8 Km3 from alluvial aquifers (Qanats and wells), 25 percent of total withdrawal is from brackish and saline water zones. Central plateau with exploing volume of 9.9 km3 (72 percent of total exploiting volume) has the most and Lake of Oroomeih with exploiting volume of 71 million cubic meter has the least exploiting volume among the basins. Use of brackish water for crop production has a long history in Iran. Management practices employed by the farmers in using these waters are similar to those practiced with the use of non-saline waters. In general, crop production is based on using high inputs of seeds, fertilizer and water. Agronomic practices such as land preparation, irrigation method and crop rotation are suboptimal. Review of policies and institution related to the use of brackish water resources revealed that the main institutional gaps to combat salinity problem in Iran is the lack of a powerful governmental organization for implementation of technologies developed for sustainable use of brackish waters Past studies have been carried out in different