The Berlin papyrus 10056, which was found at Illahun in the mortuary temple of Senuseret II, contains a series of 12 consecutive lunar observations over an 11-month period. The cycle starts on II Shemu 26, the dry season in the ancient Egyptian calendar. The cycle is dated to regnal years 30 & 31. A papyrus found nearby, ‘Papyrus Lahun IV, 1’ resolves in favour of a 12th Dynasty king – the reign of Amenemhat III in particular, son of Senuseret III and grandson of Senuseret II.
In Senuseret’s reign at the beginning of the 12th Dynasty a good Nile flood level was 12.5 metres (or 11.3 metres recorded at the Island of Elephantine). The average high flood level of Nile in this period was 12 metres above the low water mark. Record of high Nile flood levels remain in-situ with regnal years for the remaining 12th Dynasty reigns.