The Nile has been used as a water source for irrigation
for more than 6,000 years, with ancient Egyptians trapping
water and silt from the yearly floods in small basins, then
growing crops in the water-soaked soils. The ancient system
has been replaced with modern perennial irrigation systems,
in which a series of dams (barrages) keep the water at levels
to grow several crops per year, and some water is siphoned
off to irrigate areas such as the Faiyum depression. Canals
have been built to Alexandria and even across the Suez Canal
to the northern Sinai.
Ancient people of the Nile Valley did not know the
source of the Nile, or why it was prone to annual floods that
showed a seven-year cycle in intensity. The cyclicity has since
been understood to be a consequence of the El NiƱo Southern
Oscillation cycle, and explorers have entered the central
African regions that are the sources of the Nile. The ancient
Greek philosopher Ptolemy suggested that the source of the
Nile was the Mountains of the Moon, since identified as the
Ethiopian highlands around Lake Tana by Scottish explorer
James Bruce in 1770. John Speke, a British explorer, identified
Lake Victoria as the source of the White Nile in 1861.
See also RIVER SYSTEM.
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