Threshing wheat outside a typical abode village in the Tabriz area. - - Irrigation, Erosion and Sand Fixation. The Government of Iran has built several dams for irrigation and potable water supplies, and one, the Karadj dam near Teheran (completed 1962, storage capacity of 200,000,000 cu. m.) not only supplies water for the capital but also generates hydro-electric power. Problems have arisen due to erosion in the catchment areas resulting in the silting up of waterways and dams. Over-grazing and the lack of contour cultivation are contributory causes of erosion in which wind and water finally carry the topsoil away. In order to protect irrigation and the cultivation of such crops as rice, sorghum, tea, grapes and vegetables, the Government, with FAO technical assistance, has instituted an experimental project of sand dune fixation using drought resistant grasses and plants. The United Nations Development Programme, with the UN Food and Agriculture Organization as executing agency, has assisted in the establishment of a Soil Institute and associated pilot development projects.