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Abstract
Irrigation system in Egypt depends on calibrated curves and tables to connect water levels by discharge of waterways based on old levels and cross sections. That leads to distribute irrigation water to sub-channels depending on water levels only, regardless of the discharge. As a result of implementation of uncontrolled maintenance programs and oppressive dredging the cross sections of canal became deeper and wider, which contributed to the decrease the water levels upstream intakes of the branch canals and water structures. This problem can be noted very clearly in Fayoum governorate, where permanent irrigation system and using weirs as intakes to sub-channels depending only on water levels. El-Gharaq canal, located in the south of Fayoum, was selected to be studied in this research as an example of canals suffering from morphological changes due to dredging processes and improper maintenance programs. Its length is 28.020 km and serves about 48000 feddans. Data required for completion of this research were collected and measured by a team from Hydraulic Research Institute, National water research center. A comparison between the measured cross sections and the designed ones were held to identify the morphological changes occurred. It was found that cross sections expanded irregularly, which means that there is no defined criterion in maintenance. Changes in cross sectional area reached up to 140% of the designed one