The #Blue #Nile #Ethiopia, also known as #Abbay, is a significant tributary of the Nile, the #world's #longest #river. The Blue Nile River flows from Ethiopia's Lake Tana to Khartoum, #Sudan, where it joins the smaller tributary #White Nile to form the Nile River.

From the Stone Age, the Blue Nile has been gracious to its neighbouring countries, and it is also where Egyptian civilization began. In 3400 BC, towards the conclusion of the last ice age, the sea level rose, changing the route of the Nile flow from west to north, causing a huge change in climate that resulted in the formation of the Saharan desert.
https://www.ethiopiaimmigration.org/news/blue-nile-ethiopia-travel-ultimate-guide-to-the-smokey-waterfalls