Built between 1960 and 1972 by Russian engineers, the High Dam has meant the end of Egypt's dependence on the annual flooding of the Nile, and has increased the amount of productive land on the banks of the Nile through irrigation. However, it is a two-edged sword. The annual floods used to bring rich, fertile silt down the river, and there is now a danger of the Nile soil becoming unfertile. Also, the water table is rising in the Nile valley, causing major erosion of the foundations of the ancient temples and monuments. Some experts predict the temples and monuments could be destroyed by this threat unless action is taken.