Throughout the history of ancient Egypt, the annual inundation of the Nile River was relied upon to fertilize the land surrounding it. This was essential for agriculture and food production. There is evidence that the collapse of the previous Old Kingdom may have been due in part to low flood levels, resulting in famine.[71] This trend appears to have been reversed during the early years of the Middle Kingdom, with relatively high water levels recorded for much of this era, with an average inundation of 19 meters above its non-flood levels.[72] The years of repeated high inundation levels correspond to the most prosperous period of the Middle Kingdom, which occurred during the reign of Amenemhat III.[73] This seems to be confirmed in some of the literature of the period, such as in the Instructions of Amenemhat, where the king tells his son how agriculture prospered under his reign.[70]