Ucayali
The Ucayali, which rises about 70 miles north of Lake Titicaca, is the most interesting branch of the Amazon river next to the Madeira. The Ucayali was first called the San Miguel, then the Ucayali, Ucayare, Poro, Apu-Poro, Cocama and Rio de Cuzco. Peru has fitted out many costly and ably-conducted expeditions to explore it. One of them (1867) claimed to have reached within 240 miles of Lima, and the little steamer "Napo" forced its way up the violent currents for 77 miles above the junction with the Pachitea river as far as the river Tambo, 770 miles from the confluence of the Ucayali with the Amazon. The "Napo" then succeeded in ascending the Urubamba branch of the Ucayali 35 miles above its union with the Tambo, to a point 200 miles north of Cuzco. The remainder of the Urubamba, as shown by Bosquet in 1806 and Castelnau in 1846, is interrupted by cascades, reefs and numberless other obstacles to navigation. Torres, who explored the Alto Ucayali for the Peruvian government, gives it a length of 186 miles, counting from the mouth of the Pachitea to the junction of the Tambo and Urubamba. Its width varies from 1300 to 4000 feet, due to the great number of islands. The current runs from 3 to 4 miles an hour, and a channel from 60 to 150 feet wide can always be found with a minimum depth of 5 feet. There are five bad passes, due to the accumulation of trees and rafts of timber. Sometimes enormous rocks have fallen from the mountains and spread over the river-bed causing huge whirlpools. "No greater difficulties present themselves to navigation by 10-knot steamers drawing 4 feet of water."The river gives name to a department of Peru.
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