Its name comes from the literal translation of the Mapuche term Curu Leuvu, although the water is more green than black.

It originates from the junction of the Limay River and Neuquén River at the border with the Neuquén Province, and flows southeast incised through steppes to the Atlantic Ocean at 41°01′20″S 62°47′25″W / 41.0223°S 62.7903°W / -41.0223; -62.7903, near El Cóndor beach resort some 30 km (19 mi) downstream from Viedma, Río Negro province's capital.

[2] In 1604 the inland area of the river was reached by Spanish explorers departing from Buenos Aires in search of the mythical City of the Caesars.

[4] The river served briefly as a natural demarcation between "civilization" and the indigenous territories in the late 1870s and early 1880s during the Conquest of the Desert.

The main cities in Alto Valle are: General Roca, Cipolletti, Cinco Saltos, followed by many others on the National Route #22.

Alfalfa and maize is cultivated both for human consumption and for feeding cattle, which is the most important activity.