Lake Bardawil is a hypersaline shallow micro-tidal double-inlet lagoon on the northern coast of the Sinai Peninsula in Egypt. The inlets, named Boughaz 1 and Boughaz 2, connect Lake Bardawil to the Mediterranean Sea. The local population relies on the fishing yields from the lagoon, however, in the current situation, the lagoon’s inlets are unstable, needing constant maintenance dredging to stay open. Additionally, due to the hypersaline situation (limiting fish attraction) and high fish catch demand, the current fishing situation is unsustainable. The Weather Makers propose a solution to the problem using dredging interventions. Enlarging the inlets of Lake Bardawil is expected to result in increased fish migration, decreased salinity in the lagoon and increased stability of the inlets. This research aims to investigate the short-term response of Lake Bardawil and specifically its inlets to the dredging interventions proposed. To investigate the response to the interventions, two numerical models are used; a hydrodynamic model in D-flow FM and a coupled morphological model using D-flow FM and D-waves. The model results are analysed in terms of the hydrodynamic tidal response, combined hydrodynamic response to tide and weather and finally the morphological response to tidal and weather effects. From the hydrodynamic model, it can be concluded that the interventions result in a larger tidal prism for the lagoon by a factor of 1.6. This is expected to result in increased fish migration and reduced salinity in the lagoon. As the tidal prism increases, so does the discharge through the inlets. The increased discharge through the inlets results in inlet velocity amplitudes that exceed the theoretical critical value for convergence to a dynamically stable inlet cross-section for both inlets. The interventions affect more than just tidal currents in Lake Bardawil. Weather effects in the lagoon are amplified by the interventions. This is demonstrated by increased interaction between the inlets in terms of net import and export of water. During winter storms, the wind-induced flow from Boughaz 1 to Boughaz 2 is greater in magnitude. The wind waves caused by these winter storms result in sediment resuspension. This results in larger sediment transport from the basin to Boughaz 2. Using the coupled model, the morphological response in both inlets can be predicted. In Boughaz 1, the present sediment-importing character is amplified. Whereas the similar summertime sediment-importing character of Boughaz 2 is reduced substantially. The sediment export of Boughaz 2 during winter is larger in the new situation. The interventions result in increased sedimentation in the dredged channel of Boughaz 1. This does not hinder the increased tidal discharge at Boughaz 1, which is the main intended function of the interventions. This means the increased sedimentation does not influence the intended functioning of the interventions in the short term. Due to the increased sedimentation in the inner dredged channel, there is no indication of increased stability in Boughaz 1. Boughaz 2 shows less morphological activity in the situation after interventions. As is the case with Boughaz 1, there is no hindrance to the functioning of the interventions during the short simulation period. There is reduced deposition of sediment in the inner flood delta region of the inlet and the updrift side of the inlet channel compared to the known unstable situation during both winter and summer simulations. This indicates improved stability for Boughaz 2. The short-term response to the interventions in the inlets of the Lake Bardawil system is as intended, the tidal prism is increased and while there is only an indication of increased stability in Boughaz 2, there are no short-term impediments to the intended primary functioning of the interventions in either of the inlets.

Lake Bardawil is a hypersaline, shallow coastal lagoon located along the coast of the northern Sinai Peninsula in Egypt. Coastal systems are understood to be hypersaline when the salinity exceeds values of 30 parts per thousand throughout the year.
Being located in the arid climate region of North Africa the lagoon is subject to year-round extreme weather conditions which are dominated by high air temperatures, extreme evaporation rates, and limited precipitation. All the above in combination with the lagoon’s shallow bathymetry and restricted freshwater input causes Lake Bardawil to inhibit hypersaline conditions throughout the whole year. For Lake Bardawil this means average salinity values in the order of 42 – 51 parts per thousand.
The here conducted study is the first in the line of five successive studies focusing on three-dimensional hydrodynamics. Making use of the three-dimensional hydrodynamics, the movement of the water and salt through the lagoon is considered. Here the response of the system to the extreme meteorological conditions around Lake Bardawil is investigated. The meteorological forcing causes subtidal flows in coastal waters which are responsible for the propagation of waterborne materials such as salt and pollutants.
The results show that during periods of extreme meteorological forcing the response of the lagoon and its inlets is in line with expectations one might have from literature. During periods and events of high evaporation, the lagoon shows an overall increase in top and bottom layer salinity. Furthermore, the largest compensation flow due to evaporative losses of approximately 34 m3/s from the Mediterranean Sea into the lagoon is observed. While the lagoon waters act rather inert as shown for the average conditions during the month of April, it is the wind that initiates the motion. Successively the phenomenon of gravitational circulation in the deeper areas around the inlets can be observed with more saline waters propagating towards the inlets, along the bottom layer. At times, these processes cause subtidal velocities up to 0.15 m/s, which were computed in the inlets.
Crucial for the overall response of Lake Bardawil to meteorological forcing is the complex lagoon geometry and shallowness. Here the tidal divide, on the verge of the western bottleneck to the eastern basin is found to be of great importance. At this location very calm flow conditions are present promoting stagnant waters. The eastern basin with its vast areal extent experiences wind-driven circulations, while the western bottleneck is bound by its narrowness and tide dominance. As a consequence, the western inlet Boughaz 1 can be described as continuously well-mixed, while its eastern counterpart, Boughaz 2, experiences periodic stratification.
The application of system adaptations as proposed by The Weather Makers (TWM) proves to increase the exchange flow with the Mediterranean Sea. Here the dredging of two new inlets as well as dedicated tidal gullies through the lagoon established a more dynamic system where the inner lagoon connectivity is significantly enhanced. This is evident by the widespread presence of Mediterranean waters and the decreased salinity in a broad stretch along the barrier island as well as on the full lagoon scale. However, the lagoon waters in remote locations along the fringes of the large eastern basin remain of high salinity and show still little interaction with the tidal flow.