Concern has long been expressed that ancient Egyptian temples alongside the Nile deteriorate with time. Deteriorations were usually associated with annual inundations. When flood waters receded, salt deposits attacked the porous sandstone, reducing it to sand, and thus destroying the foundations. With the construction of the first dam, and of the High Dam near Aswan (in 1965), the annual inundations were eliminated. However, monitoring of the deterioration continued, especially in the Thebes–Karnak area1, where the temples are particularly numerous and important. The dam's construction was generally considered beneficial2 mostly because earlier causes of land salinization were eliminated. But this consensus was based on hydrological, climatological and chemical data1 and was only qualitative, and it has not been possible to answer this question even semi-quantitatively. However, visual observation indicates that some form of deterioration, due to salts appearing at the foundation of some monuments in Egypt, still takes place. Consequently, a deeper understanding of salinization processes is needed. We describe here a computer simulation of the flow of saline water in the area of the Great Temple of Karnak, to determine whether salinization in the post-dam, that is, present time, is a serious threat to the antiquities there.