Climate change (CC), as predicted by several global climate models, is very likely to have severe impacts in the future, on top of all other global changes. These impacts may have significant influence on natural resources especially surface and groundwater. This influence is particularly problematic for the Mediterranean coastal areas, and especially the northern Nile Delta Aquifer (NDA), where both natural and socio-economic resources of significant values are located. Moreover, population increase and development imperatives create additional pressure on the available water resources. These conditions may eventually lead to insufficient coverage of the needed water demands for agriculture, domestic usage as well as urban and industrial development,
unless adaptation and mitigation measures are developed ahead of time.

POLDERS are low-lying and artificially drained areas surrounded bywater storage canals. In low-lying delta areas such as theMississippi delta in Louisiana (USA), the Ganges-Brahmaputra delta (Bangladesh), or the Rhine-Meuse delta (The Netherlands), polders experience surface water salinization problem due to saline groundwater exfiltration, which is the upward flow of saline groundwater from the subsurface. A significant increase in surface water salinization is expected globally driven by rising sea levels, leading to a decreasing freshwater availability. Land subsidence, climate change induced decrease in precipitation and sea level rise are expected to accelerate salinization of groundwater and surface water systems. To counteract surface water salinization, freshwater diverted from rivers is used for flushing the canals and ditches in coastal areas.
Sustaining freshwater-dependent agriculture in such areas will entail an increased demand for flushing, while the demand of a better water quality will tend to increase. On the other hand, freshwater usage is not explicitly considered for polder operation and results in excessive use. Decreasing the amount of freshwater usage for polder flushing can create additional supply opportunities for industrial users, drinking water companies or other irrigation systems. To meet the increasing demand for flushing due to expected increase of salinization while the freshwater availability is decreasing, new operational designs are required for polders that will use the available freshwater resources
efficiently.