User:Tson21/Nilometer

Lead
A nilometer was a structure for measuring the Nile River's clarity and water level during the annual flood season. There were three main types of nilometers, calibrated in Egyptian cubits: (1) a vertical column, (2) a corridor stairway of steps leading down to the Nile, or (3) a deep well with culvert.

If the water level was low, the fertility of the floodplain would suffer. If it was too high, the flooding would be destructive. There was a specific mark that indicated how high the flood should be if the fields were to get good soil.

Nilometers originated in pharaonic times, were also built in Roman times, and were used until the Aswan Dam rendered them obsolete in the 1960s.

Description
Between July and November, the reaches of the Nile running through Egypt would burst their banks and cover the adjacent floodplain. When the waters receded, around September or October, they left behind a rich alluvial deposit of exceptionally fertile black silt over the croplands. The akhet, or Season of the Inundation, was one of the three seasons into which the ancient Egyptians divided their year.

Importance
The annual flood was of great importance to Egyptian civilization. A moderate inundation was a vital part of the agricultural cycle; however, a lighter inundation than normal would cause famine, and too much flood water would be equally disastrous, washing away much of the infrastructure built on the flood plain. Records from AD 622–999 indicate that, on average, 28% of the years saw an inundation that fell short of expectations.

All across Egypt various nilometers recorded readings of the Nile's annual levels could be found. An uncovered fragment of a recovered Egyptian stele "Royal Annals of the Old Kingdom" depicts a fragment of the stele known as the “Palermo stone” deemed to be from the times of the First Dynasty around 3000 B.C.E. The Palermo Stone reported systems of measurements utilizing units such as cubits, palms, and fingers. The ability to predict the volume of the coming inundation was part of the mystique of the Ancient Egyptian priesthood. The same skill also played a political and administrative role, since the quality of the year's flood was used to determine the levels of tax to be paid. Due to the importance and religious components related to the Nile and its interwind existence of the Egyptian's ideology or belief in Ma'at (a system of natural balance), Nilometers were accessible to only members of their cities respects priesthoods and nobles like that of Pharoses. The exclusion on who may access these structures ensured both accountability in proper readings, as well as maintaining political control to both the religious communities and ruling classes. This is where the nilometer came into play, with priests monitoring the day-to-day level of the river and announcing the awaited arrival of the summer flood.

Designs
The simplest nilometer design is a vertical column submerged in the waters of the river, with marked intervals indicating the depth of the water. One that follows this simple design, albeit housed in an elaborate and ornate stone structure, can still be seen on the island of Rhoda in central Cairo (30.0069°N 31.2250°E). This nilometer visible today dates as far back as AD 861, when the Abbasid caliph al-Mutawakkil ordered its construction, overseen by the astronomer Alfraganus. It was built on a site occupied by an earlier specimen which was seen by the Syrian Orthodox patriarch Dionysius of Tel Mahre in 830.[citation needed] This prior nilometer had been ordered in AD 715 by Usāma b. Zayd b. ʿAdī, who was in charge of collecting the land tax (kharaj) in Egypt for the Umayyad caliph Sulaymān ibn ʿAbd al-Malik.

The second nilometer design comprises a flight of stairs leading down into the water, with depth markings along the walls. The best known example of this kind can be seen on the island of Elephantine in Aswan. , where a stairway of 52 steps leads down to a doorway at the Nile. This location was also particularly important, since for much of Egyptian history, Elephantine marked Egypt's southern border and was therefore the first place where the onset of the annual flood was detected.

The most elaborate design involved a channel or culvert that led from the riverbank – often running for a considerable distance – and then fed a well, tank, or cistern. These nilometer wells were most frequently located within the confines of temples, where only the priests and rulers were allowed access. A particularly fine example, with a deep, cylindrical well and a culvert opening in the surrounding wall, can be seen at the Temple of Kom Ombo, to the north of Aswan.

Usage
While nilometers originated in Pharaonic times, they continued to be used by the later civilizations that held sway in Egypt. Some were constructed in Roman times.

Between 872/873 the first independent ruler of Egypt after the Ptolemaic pharaohs, Ahmad ibn Tulun would have the nilometer restored, having al-Mutawakkil's name removed from the Kufic inscription.

Consequently, the Nile's irrigation would be enhanced, and agricultural output increased.

In the 20th century, the Nile's annual inundation was first greatly reduced, and then eliminated entirely, with the construction of the Aswan dams. While the Aswan High Dam's impact on Egypt and its agriculture has been controversial for other, more complex reasons, it has also had the additional effect of rendering the nilometer obsolete.