stylistic:tone, information:extraction, structural:summarization, information:highlighting
Early European exploration

The first European known to have seen the Blue Nile in Ethiopia and the river's source was Pedro Páez, a Spanish Jesuit who reached the river's source on 21 April 1618. However, the Portuguese João Bermudes, the self-described "Patriarch of Ethiopia," provided the first description of the Tis Abay River Falls in his memoirs published in 1565, and any number of Europeans who lived in Ethiopia in the late 15th century such as Pêro da Covilhã could have seen the river long before Páez, but not reached its source. The source of the Nile proper was also reached in 1629 by the Portuguese Jesuit missionary Jerónimo Lobo and in 1770 by the Scottish explorer James Bruce.

Although European explorers contemplated tracing the course of the Nile from the Blue Nile's confluence with the White Nile to Lake Tana, the Blue Nile Canyon has discouraged all attempts since Frédéric Cailliaud 's attempt in 1821. The first serious attempt by a non-local to explore this reach of the river was undertaken by the American W.W. Macmillan in 1902, assisted by the Norwegian explorer B.H. Jenssen; Jenssen proceeded upriver from Khartoum while Macmillan sailed downstream from Lake Tana. However, Jenssen's boats were blocked by the rapids at Famaka short of the Sudan-Ethiopia border, and Macmillan's boats were wrecked shortly after they had been launched. Macmillan encouraged Jenssen to try to sail upstream from Khartoum again in 1905, but he was forced to stop 500 km (300 mi) short of Lake Tana. Robert Cheesman, who records his surprise on arriving in Ethiopia at finding that the upper waters of "one of the most famous of the rivers of the world, and one whose name was well known to the ancients" was in his lifetime "marked on the map by dotted lines", managed to map the upper course of the Blue Nile between 1925 and 1933. He did this not by following the river along its banks and through its impassable canyon but by following it from the highlands above, travelling some 8,000 km (5,000 mi) by mule in the adjacent country.