1970: The Aswan High Dam is built in Egypt, controlling the Nile's annual flood but changing the river's ecosystem.
A second, or "High," Aswan Dam is built with Soviet assistance to replace the older, less effective Aswan "Low" Dam. The dam has stopped the river's annual floods by trapping its waters in a reservoir and slowly releasing it during the dry season. This allows farmers along the Nile to plant year round. Unfortunately, the dam also traps the river's fertile silt, forcing the use of artificial fertilizers by farmers and causing pollution. Other effects of the dam are riverbank erosion and high levels of soil salinity.