Hydrological Impact of Ilisu Dam on Al-Gharraf River in southern of Iraq using MIKE11 Hydrodynamic Model

A 1-dimensional unsteady flow hydraulic model the MIKE 11 model is employed for the flow simulation of the Algharraf River in this study. Algharraf River branches from Tigris River at Alkut barrage and represent the most water source to cities located in Alkut, Thi Qar, and Basra Province. A flow and stage hydrograph in time series format from the field observations is used by the MIKE 11 model. The outcome of this model leads to unsteady flow simulations along a stream of the river. The model was applied to all length of the river from Alkut barrage upstream to Bada’a Barrage downstream. The study aimed to construct a MIK 11 model based on surveyed, stream cross-section data. The results of this study explain that the model gives a good simulation of the flow according to a comparison between the estimated and observed stage hydrograph. The finding of the hydrodynamic model is employed to present the hydrological impact of the Ilisu Dam constructed upstream of the Tigris River (basically predicts changes in future inflow) on the flow of the river. Results discover that the constructed dam will have a strong and clear impact on the inflow regime of the flow to the river. Without taking into account the effects on downstream hydrology and the environment, the first stage of operation of the Ilisu and Cizre Dams results in a reduction of the inflow of up to more than 40%, and with full operation may result in a reduction of more than 70%.