Irrigation and drainage systems in Basrah province, Iraq
This study of the irrigation and drainage systems in Basrah province analyses the factors affecting these systems, such as the water resources, soil conditions, management and crops and then shows the effects of these systems on crop yields and soil salinity. In such a study it is necessary to discuss the physical characteristics of the province and the hydraulic aspects of Iraq which have direct and indirect influences on the irrigation and drainage systems in the province. In accordance with the variations in the irrigation and drainage systems, the province has been divided into four regions, namely : the Western, Southern Tigris, marshes and the Shat Al-Arab. One of the findings of this study has been the spatial differences between the levels of salinity in the irrigation water which ranges from moderate in the southern Tigris, marshes and the upper section of the Shat Al-Arab to excessive in the western region and the lower section of the Shat Al-Arab. The salinity of the irrigated soils has also been shown to vary from region to region, from a very low level in the marshes to a strongly high level in the southern Tigris. Throughout the province it was found that the farmers continued to rely on their traditional skills and inherited experiences in carrying out cultivation and irrigation operations which have resulted in over-irrigation and low efficiency of use of irrigation water. This, together with the inadequate drainage and high evaporation rates has led to exacerbation of the soil salinity problem and the consequent abandonment of large areas of cultivable lands in the western, southern Tigris and the Shat Al-Arab regions. Additionally, in the marshes and the Shat Al-Arab regions the presence of aquatic vegetation forms an important obstacle to irrigation and drainage operations. Moreover, it is likely that in the future the province will face a serious shortfall in irrigation water availability. The province, however, still remains an important agricultural area, providing the Iraqi markets with tomatoes during winters and contributing 11.8% of the country's total date production. Improvements in irrigation and drainage and in soil-water management are therefore vital.