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An optimization model for High Dimension Dynamic Programming (HDDP) was developed to determine the optimal size of water resources projects within a planning period. The model uses Objective Space Dynamic Programming (OSDP) technique to determine the size of the projects and a Mixed Integer Programming (MIP) formulation to overcome the 'inner' and 'outer' problems of OSDP and to check for the global optimality of the solution. The model is applied to determine the optimal capacity of proposed desalination plants needed to satisfy a number of demand points from different cities, during a planning period of 20 years in Egypt. The model's speed towards the optimal solution depends on the objective space bounds and search method for these bounds. The integration of OSDP and MIP is shown to be an efficient approach for solving optimization problems. Results show that the model is well suited for solving large-scale water resources expansion problems.

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This study assesses the potential downstream impacts in the event of a flood due to failure, either structural or operational, of the Grand Ethiopian renaissance dam (GERD). The following two failure scenarios were modeled as part of this study: Dam Break (DB) and MisGuided Dam Operation (MGDO) as a result of a false flood signature. The DB scenario shows that 40% of the intensively cultivated Gezira Plain would be inundated with average water depths of more than 10 m, resulting in catastrophic loss of highly productive farmlands, livestock, inhabitants, and infrastructure. This scenario did not model damage further downstream since for this magnitude flood it will require another flood routing model given the more complex geometry downstream of the Gezira Plain. In the MGDO scenario flood flows are lower and would have no impact on the Gezira Plain but would reach the High Aswan Dam (HAD) and fill it to its maximum allowable capacity for two and a half months and it would require emergency releases for more than 5 months. The required emergency releases from the HAD are expected to create significant flooding downstream. To accommodate the potential of extra releases from the GERD during flood events the operational rules for the HAD should be modified. However, providing more flood buffer at the HAD will limit the live capacity that is currently used for securing downstream flow requirements during drought periods. One of the expected impacts of increasing the flood buffer would be a reduction of the HAD's contribution to Egypt's GDP. Based on the results of this study the operational rules for the GERD and the HAD should be evaluated and possibly modified.