The monsoonal climate of Ethiopia is responsible for the high degree of
seasonality of the run-off of the three Nile tributaries mentioned, and thus
also of the Nile: 63 per cent of this water, which is discharged into the High
Dam reservoir today, is concentrated in the three months from August to
October. This flood carries 130 million tons of silt of volcanic origin from
Ethiopian soils. It was responsible for the creation of the fertile black soils
of the Nile valley, which are the reason why the ancient Egyptians named