The Nilometer was invented for recording the annual floods of the Nile. As the name suggests, the device originates from the region of the Nile, especially Egypt. Since the earliest of times, the Egyptians had to cope with the inundation caused by the river; thus they learned how to control and also to make a profit from it.
The earliest record of flood control comes from the annals of the 'Palermo Stone'. The levels of the floods reported on the stone prove that the earliest Nilometer dates to the Thinite period (1st and 2nd Dynasties, 3150-2690 BCE). Many ancient writers mentioned the Nile and its floods. Diodorus Siculus (early 1st century BCE) visited Egypt to gather information for his history. In Book I. 36. 7, he wrote that the Nile floods at the summer solstice (beginning on the 21st of June), while the water level of other rivers becomes lower during this period. The significance of the Nile's inundation is related to Memphis, which is situated at the root of the delta. Diodorus also wrote that the kings constructed a Niloscope (Nilometer) at Memphis, where administrators were appointed to take accurate measurments of the floods, how many cubits or fingers the river had risen, and when it commenced to fall (I. 36. 11). King Amenemhat III (12th Dynasty, 1842-1797 BCE) built such a Nilometer, at Memphis.
As they developed in antiquity, Nilometers may be classified into four types: (1) corridor with stairs (Fig. 109); (2) well (Fig. 107); (3) well with a column (Fig. 106); and (4) column (Figs. 104, 105).
The common depiction of a Nilometer in the art of the Roman-Byzantine periods is a column; however, it did not necessarily mean a typical Egyptian Nilometer.
Corridor types were found at Philae, and at Elephantine (Yev) they were associated with the temple of Satet. Originally a simple scale for measuring the flood were inscribed on the wall of the quay. Later, the scale became a covered stairway leading from the temple platform to the Nile. A large well or rectangular basin associated with the temple of Khnum was also found at Elephantine. On the wall of the structure there were marks for measuring the level of the inundation. These levels were directly related to the taxes to be paid on the floodwaters; higher levels meant an increase in taxes (Strabo, 17. I. 48).
One of the best illustrations of a well-type Nilometer is depicted in the famous 'Nile Mosaic' at Palestrina, Italy (late 2nd century BCE). This well probably represents the same type that was found at Syen (Aswan) and mentioned by Pliny (NH11. 183) and Strabo (17. I. 48). Both historians said that the midday sun in the summer solstice did not cast any shadow in the well and that the light reached the bottom, showing the water level, probably at the crest of the flood.
The well-type Nilometer was modified during the Ptolemaic period, with stairs in or around it; examples of such Nilometers are found in the temples at Kom-Ombo and Edfu. In the Roman period, the scale was moved from the wall of the well to a column that was placed in the center of the well or the basin, like the famous Nilometer on Rhoda island, opposite Cairo. A column with the statue of the god Nile rising from a well is depicted on a silver plate from Perm (Russia). A similar scene appears on a Coptic textile. In later depictions of Nilometer, the column is shown either standing on a rectangular structure or as a single object.
Different types of Nilometers existed side by side; changes in flood level were marked on any one of them. The measurement unit was the small cubit of 6 palms (ca. 45 cm.), and not the royal cubit of 7 palms (ca. 52.3- 52.6 cm.). The small cubit was more convenient for paying the required taxes. At Elephantine, a good flood meant a rise of 28 cubits, whereas at Edfu, 24 cubits and 3 palms were required. At Mendes and Xois, 6 cubits were considered sufficient. At Memphis in the Graeco-Roman period, 16 cubits were held to be the desirable height. This measurement is understood from the famous statue of the god Nile (Vatican Museum) reclining on his side and surrounded by 16 putti, each a cubit high. If the inundation did not reach 16 cubits, the situation was as disastrous as if the level had exceeded 18 cubits.
The beautiful 'Nile Festival House' mosaic floor at Sepphoris (5th-6th centuries CE; Fig. 105) is one of the best ILLUSTRATIONS of the marking of a new flood level. The Nilometer is depicted here as a round column placed on a rectangular structure with an arched opening. The device was placed in the river to measure the rising waters. Horizontal bands marked on the column have inscribed Greek numbers, referred to as cubit measuring units: IE = 15, IS = 16, IZ = 17. Beside the column, a man stands on the back of a woman and engraves the number IZ = 17 with a chisel and a hammer.
Aside from the Sepphoris Nilometer, two additional mosaic depictions were found in Israel. In the 'House of Leontis' in Beit Shean' (Fig. 108), a Nilometer appears as a vertical column placed to the left of a roofed structure, probably a temple (5th-6th centuries CE). Greek numbers are inscribed within the horizontal bands: I = 10, IA = 11, IB = 12, I G = 13, I D = 14, IE = 15, IS = 16, IZ = 17. Both Nilometers, from Sepphoris and Beit Shean, are associated with Alexandria, as indicated by the Greek inscription. A fragmentary rounded column with a conical top appears as an isolated object in the 'Nile Mosaic' in the Church of the Multiplying of the Loaves and Fish as at Tabgha, on the northwestern shore of the Sea of Galilee (4th-5th centuries CE; Fig. 104). The numbers inscribed on the column are: S = 6, Z = 7, H = 8, q = 9, I = 10.
Different types of Nilometers remained in use and were rebuilt through the centuries. The Pharaonic Nilometer at Elephantine was rebuilt in the Roman period; the marks still visible on it date to that period. Nilometers were also built in later periods. A relevant example is the one found at Geziret el-Rhoda Island (opposite Cairo). It is an Islamic Nilometer, dating back to the Umayyad period (705-715 CE); it was renovated in 861 and was still functioning at the beginning of the 20th century CE. Islamic Nilometers worked on the same principle as their ancient counterparts, except that the former used an octagonal shaft, placed in the center of a rectangular basin.
The Nilometers presented above emphasize the importance of the Nile's floodwaters, and their control and administration, for the vitality of the Egyptian people.
Jones, H. L. (1959) The Geography ofStrabo, Vol. VIII, Book 17, The Loeb Classical Library, Harvard University Press
Meyboom, P. G. P. (1995) The Nile Mosaic of Palestrina: Early Evidence of Egyptian Religion in Italy, Leiden
Moret, A. (1972 reissued) The Nile and the Egyptian Civilization, London
Netzer, E. and Weiss, Z. (1992) New Mosaic Art from Sepphoris, Biblical Archeology Review, Vol. 18, No. 6: 36-42, 76
Oldfather, C. H. (1959) Diodorus Siculus, Vol. I, Books I-II, 1-34, The Loeb Classical Library, Harvard University Press
Rackham, H. (1962) Pliny, Natural History, Vol. I, Books I-II; The Loeb Classical Library, Harvard University Press