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University of Gezira (2013)

Evaluation of Sediment Management in Khashm El Girba Dam in Sudan (1961-2009)

Abdalla, Mohamed Abdalla Suleiman

Titre : Evaluation of Sediment Management in Khashm El Girba Dam in Sudan (1961-2009)

Auteur : Abdalla, Mohamed Abdalla Suleiman

Université de soutenance : University of Gezira

Grade : Master of Science (MS) in Water Management 2013

Résumé
Dams are constructed to store water from abundance time to release it during the low flow period to fulfill various demands. Khashm El Girba Dam KGD constructed in Atbara River, has been affected by the high amount of sediment carried by the river which reduces its capacity and negatively influences the agricultural scheme. The annual amount of sediment deposited during the first seven years was 40 Mm3 and reduced to less than 10 Mm3 after application of flushing. Hence, updating and calculating of the outflow suspended sediment, flushed sediment and the bed load is essential for managing of sediment and water. The objectives of the study are to evaluate the amount sedimentation in the reservoir ; to establish equation for assessing sediment load from volumetric measured data in the site beside the evaluation of the negative impact of sedimentation on Halfa agricultural scheme. The study used the hydrographic survey conducted in 1990 and 2009 to quantify the bed load and used the weight sediment concentration for assessing the suspended load. Due to the scarcity of weight concentrations data and the availability of the volumetric suspended sediment concentrations in the site the rating curve techniques were established between the two types of concentration to assess the sediment weight concentration for the period 1990 to 2009. Hence, outflow, bed, flushed and inflow sediment loads were determined. The results showed that the average annual inflow sediment load is 85 (Mt), which are in agreement with previous results, the efficiencies of sluicing suspended and flushing sediment were found to be 78% and 18% respectively. The study recommended during the flushing operation the reservoir level should be raised and lowered many times and its duration time should be in the range of 24 and 36 hours. However, the flushing method should be revised after establishing of Upper Atbara Complex Dams and TKZ5 in Ethiopia. Due to the negative impacts of sediment deposited in KGD and other factors on the NHAC such as mismanagement of water and lack of maintenance the cultivated areas of wheat and cotton were reduced by 72% and 42 % respectively

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