Modeling the Impact of controlled flow and sediment releases for the restoration of the Nile River-Delta system, Egypt

The construction of the High Aswan Dam (HAD) and river barrages significantly modified the flow and the sediment transport regimes in the Egyptian portion of the Nile River. Field data of the Nile Research Institute reveal that flood flows are reduced more than 70% compared to pre-HAD conditions and more than 98% of the sediment load is trapped in Lake Nasser upstream of the HAD. Water diversions at the barrages further reduce the flow rate reaching the Nile delta. Consequences of the flow regulation are erosion of the channel bed and changes in channel morphology in the upstream part of the study reach, and in-channel sedimentation in the downstream part of the system. However, due to the flow reduction, the sediment load delivered to the Mediterranean Sea is negligible compared to pre-dam conditions with consequent delta wide wetland loss and shoreline retreat. Here we present the first part of a feasibility study for the restoration of the Nile River-delta system characterized by controlled flow releases and sediment augmentations downstream of the HAD. The controlled flow releases are obtained by combining the current releases form the High Aswan Dam with a 10 billion m3 annual hydrograph. Previous studies showed that this volume of water will be available if the irrigation canals are replaced by more water efficient irrigation methods. The objectives of this work are to quantify the effects of the restoration project in terms of 1) erosion in the upstream part of the study reach, 2) sedimentation in the downstream part of the study reach, and 3) flow rate and sediment load delivered to the delta apex during the restoration project. The impacts of the controlled flow and sediment releases on the Nile River delta will be quantified in the near future.