Eight countries feed into the Nile River upstream of Egypt. However, Ethiopia's Blue Nile accounts for more than 80% of the Nile's water that flows through Egypt. Since long before there were civilisations along the Nile, the Ethiopian Highlands would experience rain storms every year from June to mid-September. That rain washed the rich volcanic topsoil into the Blue Nile River, which was then carried thousands of kilometres along the Nile through Sudan and Egypt and deposited along its banks and in the über-fertile Nile Delta. For thousands of years the Nile River Valley civilisations relied on this silt to fertilise their crops and animal feed, and the Blue Nile floods to irrigate them.