The Nile and Geography of Egypt
The Nile is one of the planet’s few rivers to run from South to North. It is the earth’s longest river covering a distance of four thousand six hundred miles. It starts just south of the equator, as the White Nile, and is joined by the Blue Nile at Khartoum fed by melting snows in the mountains of Ethiopia. It is then joined by the Atbara between the 5th and 6th Nile cataracts bringing with it vast quantities of suspended silt. The Nile then flows another two thousand five hundred miles north through Egypt before spreading out into a broad delta named after the shape of the inverted Greek letter D. It then slowly enters the Mediterranean Sea by two principal mouths, the Rosetta in the west and the Damietta in the east.

Erosion has created limestone and sandstone cliffs on either side of the Nile river in Egypt. These cliffs typically rise to a height of a few hundred feet but reach nine hundred feet where the Nile swings sharply northeast at Qena near Luxor. Because the river typically flows to the east of the valley ninety percent of the cultivatable land lies on the west bank.

Annual inundation
In antiquity, the peak river flow occurred each year from mid June at Aswan in the south of Egypt, to early October at Memphis in the north. The Nile burst its banks by up to thirty feet and flooded a broad strip of farm land up to twelve miles in width. This annual event was called the inundation or ‘akhet’. It was seen by the Ancient Egyptians as the coming of the God Hapi bringing fertility to the land. When the Nile waters receded, they deposited a rich layer of fertile silt on the Egyptian land, ready for crop planting. This created a rich agricultural green ribbon stretching a thousand miles. This dark Egyptian ribbon (above) is a dramatic contrast to the stark endless Egyptian desert on either side. The Ancient Egyptian winter growth season or “peret” was followed by the spring/summer harvest season “shemu”. In some cases the rich soil could accommodate two crops a year.

Ancient Egyptian Nileometers measured water levels in the Nile; records were primarily used to set tax levels for the coming year. Every summer melting snow and rain in the mountains of Ethiopia caused the inundation (akhet); the Nile overflowed its banks and covered the flood plain.

When the waters receded, around September or October, they left behind a rich alluvial deposit of exceptionally fertile black silt over the fields. Egyptian Nileometer records were carefully recorded and kept in the royal libraries. A moderate inundation was a vital part of the agricultural cycle; however, a light inundation could cause famine, and too much flooding would destroy the riverbank farming villages. Ancient records show that on average, one out of five Nile inundations was either too low or too high.

The ability to predict the height of the coming inundation was important to determine the levels of tax to be paid, usually in the form of grain. The oldest form of Nileometer design comprised a flight of stairs leading down into the water, with depth markings along the walls. The finest surviving example is at Elephantine by Aswan, being in the extreme south it was the first to detect the rising Nile waters. A few Nileometers were located some distance from the river within a temple complex, the finest example is at the temple of Kom Ombo below Aswan.