Irrigation has been defined as the artificial control of soil moisture for agricultural purposes (Rydzewski 1974). Therefore the soil is probably the first consideration in any proposed scheme for irrigation, and geological survey must be a starting point to provide a clear understanding of the origin and distribution of the soils and groundwater conditions underlying them. The study of soils and their suitability for irrigated agriculture is a specialized subject. Its basis is an appreciation of the geology and in particular the geomorphology of the region.
Problems in irrigation engineering associated with ground conditions usually arise as a result of changes in moisture content of the soils or of the ground water regime in the underlying material. This paper deals with problems that are universal in irrigated agriculture of arid or semi-arid lands, but the experience on which it is based and the examples quoted are derived from the Middle East. Irrigation drawing its supply from ground water is becoming increasingly important in the region, but this paper does not deal with strictly hydrogeological problems associated with supply.
At the present time in the truly arid areas of the Middle East there is only limited experience of large scale irrigation. In some peripheral areas however, soils exist which, if irrigated, would be potentially of agricultural value. Extensive irrigation projects for semi-deserts and dry grassland indicate some of the problems that undoubtedly would be encountered if large scale irrigation schemes were attempted in the truly arid areas of the