Until the Aswan High Dam was built, Egypt received a yearly inundation - an annual flood - of the Nile. The ancient Egyptians did not realise this, but the flood came due to the heavy summer rains in the Ethiopian highlands, swelling the different tributaries and other rivers that joined and became the Nile. This happened yearly, between June and September, in a season the Egyptians called akhet - the inundation. This was seen by the Egyptians as a yearly coming of the god Hapi, bringing fertility to the land.

The first signs of the inundation were seen at Aswan by the end of June, reaching its swelling to its fullest at Cairo by September. The flood would then decrease in size around two weeks later, leaving behind a deposit of rich, black silt. The amount of silt left behind due to the height of the Nile determined the amount of crops that the Egyptians could grow - if the inundation was too low, it would be a year of famine.

The Egyptians learned a method of measuring the height of the Nile known as the Nilometre.

Although all Nilometres used by the Egyptians had a single obvious purpose, to mark the highest point of Inundation, they were constructed in one of three different formats -- a slab or pillar, a well or a series of steps. All three were calibrated using the same unit of measurement, the cubit; the Egyptians broke the cubit into smaller units, which allowed them to keep remarkably accurate records, perhaps more accurate than would have been warranted for the purposes of merely agriculture and taxation.



The Nilometre on Elephantine Island near the First Cataract deep in southern Egypt always held supreme importance. It was the first outpost where the floods exerted themselves and the first to know when they were over, but the religious significance of the might might have overshadowed its strategic location. It was the home-place of Khnum, the ram-headed god of Inundation. During the Eleventh Dynasty a sanctuary was built on the island specifically to celebrate Inundations. A new Nilometre replaced a much older one at the edge of Khnum's Temple during the Twenty-Sixth Dynasty; somewhat later, in Dynasty Thirty, a riverside terrace and another Nilometre was added to the nearby Temple of Satet, one of Khnum's celestial consorts. When Egypt fell to Rome, that did not mean an end to Nilometres on Elephantine Island, for Khnum's Nilometre received a new calibrated staircase and a granite roof from the Romans.

-- Ralph Vaughan, Nilometers: Measuring the Universe

The Nilometres were usually a series of steps by the Nile, where the water level against the steps would show how high the Nile would rise and records of the maximum height of the inundation could be taken. There are Nilometres at the temples at Elephantine, Philae, Edfu, Esna, Kom Ombo and Dendera. These were build through pharaonic times up until Roman times. There was even a Nilometre built during early Islamic times at el-Rhoda in Cairo, which was possibly the site of an ancient Nilometre, though it used a pillar rather than the usual steps.

The ancient Egyptians viewed Sirius as the bringer of new life. This was because Sirius was newly visible in the sky at the time of the flooding of the Nile River, the life-giving inundation which yearly fertilised their crops.

The inundation was also around the time that the Egyptians noticed the rising of the 'dog star' Sirius. The goddess Sopdet (Sothis) was the personification of this star, represented as a woman with a star as her headdress, or as a seated cow with a plant between her horns (just as Seshat's hieroglyph might have been a flower or a star.) Her star was the most important of the stars to the ancient Egyptians, and the rising of this star came at the time of inundation and the start of the Egyptian new year. She was linked closely with Isis, just as her husband Sah (the star Orion) and son Soped were linked with Osiris and Horus.

Isis' sister Nephthys is also somewhat linked to the inundation - in one particular tale, she represents the desert while Osiris represents the inundation itself. When the Nile flood is high enough to reach the desert, flowers bloom in the barren red land. In the story, Osiris and Nephthys have a drunken union, where Osiris leaves behind his garland of melilot flowers. As the inundation was a sign of fertility, Osiris and Nephthys were thought to have had a child - Anubis, god of mummification.

Now because the Ancient Egyptian calendar was slightly out of step with the solar and lunar year - the Egyptian calendar was out by 6 hours. As time went on, the inundation came occasionally during the season of akhet, so the Egyptians relied on the star, rather than the season, as the herald of both the new year and the yearly flood.

The other two seasons were peret (growing) and shemu (harvest). During the growing season (after the inundation had receded, if not exactly in the season according to the calendar) the Egyptians planted their crops - around October and November - and tended to the fields. The Egyptians watered their crops using an irrigation system of canals or by bringing water to the fields in basins or by using the shaduf, which is still in use in Egypt today, to raise water from the river to the bank of the Nile. By the time the Nile reached its lowest level, some time around March or April, the crops would be ready for the harvest.

During the inundation, though, there was nothing to do for the Egyptian farmer. Rather than doing nothing for a whole season, the Egyptians would do other tasks rather than paying tax. (Tax was usually taken out of the crops that the farmers grew, and during inundation, the farmland was covered by water!) During the Old Kingdom, this work took on the form of working on building pyramids.

This was not done, as originally and incorrectly thought, by slave labour. In fact, it was done by Egyptian citizens who had little else to do for one season a year. These men were also 'paid' for their work - workmen at the pyramids of the Giza Plateau were given beer, thrice daily - five kinds of beer and four kinds of wine!

If Egypt had a drought or a year of plenty, it was the will of the Nile god Hapi. The Egyptians gave him offerings and worship to hopefully bring a good flood that wasn't too high or too low. They celebrated the 'Arrival of Hapi', hoping that their houses wouldn't be washed away, or that the Nile would rise enough to provide both water and silt for the farmland. But the Egyptians, despite being able to measure the flood, couldn't change the situation if the Nile's waters weren't at the required level. To them, the inundation was truly in the hands' of the gods.