224-Gezira Scheme Irrigation System Performance after 80 years of Operation.

Abstract

Gezira Scheme (GS) is considered one of the oldest irrigation systems in Africa and the Arab region. Moreover, its the largest scheme (0.90 million ha) in the world under a single management. The length of the irrigation network is 11000 km, in addition to 29000 field channels. This paper is seeking to evaluate the irrigation GS system performance after more than 80 years of operation, especially if it is realized that serious deterioration was experienced in the last decade, where the system failed to meet the crop water requirement. This may be attributed among many other reasons mainly to: the huge amounts of sediment entering the scheme each year and the mismanagement of the irrigation system. The impact of this is water shortage in wide areas of the scheme and flooding in others, i.e. inequity in the water distribution and hence reduction in crops production and returns of the scheme. In this context a critical review of the irrigation system is discussed. The concept and procedure for designing and remodeling of the silted canals to restore the original section are highlighted, based on the rich experience and performance of this irrigation system. It is found that aquatic weeds aggravated the sedimentation rate and the deposited sediment enhances the aquatic weeds growth, which leads to canal capacity reduction. The impact of this on the socio-economic development of the scheme is explained. The paper finally examines the possibility of having canals with stable regime condition. It also reports on the future of the irrigation system management and the possibility of having an efficient and effective system for better crop production.