Nilometer, Elephantine Island, Aswan, southern Egypt.
The ancient Egyptians relied on floodwater as the beginning of the agricultural season, and they knew that its water makes the land more fertile and suitable for agriculture, but sometimes when the flood comes severe and damages a large part of the agricultural crop, or the water level decreases at some times and famine prevails throughout Egypt. And when the ancient Egyptians understood this matter, he created what is now called a scale to know the level of the Nile water to predict the movement of water and its level. On this basis, the area of ​​land that will be cultivated is determined and, accordingly, the quantities of harvest and the amount of taxes that will be imposed on farmers—the most important administrative tools in Egypt.
The idea of ​​the scale began as specific signs on the Nile banks, and the idea developed into wells, then into a stairway with some signs, then a column was placed in the middle of the stairs with many signs.
The importance of the Elephantine scale is that it is the first scale to record the beginning of the flood, as it is located south of Aswan, meaning south of ancient Egypt, so it has the lead in knowing the quantity and strength of water.
It consists of a relatively long staircase with an end at the Nile River and on.
Its walls are water level markers.