Aswan Dam links the reservoir to the Toshka Depression. The reservoir, named Lake Nasser, is long and at its widest, with a surface area of . It holds of water. Due to the absence of appreciable rainfall, Egypt's agriculture depends entirely on irrigation. With irrigation, two crops per year can be produced, except for sugar cane which has a growing period of almost one year. The high dam at Aswan releases, on average, water per year, of which some are diverted into the irrigation canals. In the Nile valley and delta, almost benefit from these waters producing on average 1.8 crops per
Aswan Low Dam in the lower Nile. The dam, originally limited in height by conservation concerns, worked as designed, but provided inadequate storage capacity for planned development and was raised twice, between 1907 and 1912 and again in 1929–1933. These heightenings still did not meet irrigation demands and in 1946 it was nearly over-topped in an effort to maximize pool elevation. This led to the investigation and construction of the Aswan High Dam upstream. The earliest recorded attempt to build a dam near Aswan was in the 11th century, when the Arab polymath and engineer Ibn al-Haytham (known as "Alhazen" in the West)