Peasant on his boat, Egypt

The Nile, the world’s longest river, runs from south to north through Sudan and Egypt for 4,140 miles (6,671 km). It is a communication route that carries both luxury floating hotels for tourists and modest crafts bearing mostly fodder and grain. Above all, the Nile is the main water resource of Egypt, providing 98 percent of the water consumed by the country. Whereas at one time the Nile’s annual flood assured available water for only three to four months, the construction of the Aswan Dam in the 1960s made it possible to regulate the river’s flow and thus provide the country with water throughout the year, retaining a volume of water that is double the average annual flow of the Nile. However, the dam has caused ecological problems by depriving the river of the silt that fertilized the soils and by offsetting the sedimentation that compensate for the erosion of the delta by the sea. Today the delta is receding at a rate of 100 to 650 feet (30 to 200 m) per year.