NILE FLOODS

The oldest year-by-year record of flood levels for the River Nile in Egypt. The earliest known records in Cairo date from the Early Dynastic Period recording the height of every flood back to about 3090 BC. The most reliable measurements date from AD 622 onwards. These are continuous up to AD 1470 and then, with a few gaps, run up to the present day. This record is the longest continuous annual climatic series monitoring the rainfall in a large drainage basin. It is particularly sensitive to precipitation in the Ethiopian Highlands, which are drained by the Blue Nile. Due to the river’s links to other climatic zones, the record holds key evidence of the global nature of climatic variability and the existence of teleconnections. Major, longterm variations can be identified with periods of low discharge from AD 630 to 1071 and AD 1180 to 1350. High discharge episodes occurred from AD 1070 to 1180 and AD 1350 to 1470. The annual flood is related to the summer monsoonal rains in Ethiopia, which are associated with a northward shift in the intertropical convergence zone (ITCZ).