The Manso River arises at elevation of 1,000 metres (3,300 ft) in the small lake fed by the Ventisquero Negro glacier.

A road (unpaved in 2015) runs along the eastern and south shore of Mascardi Lake and continues downstream for another 10 kilometres (6.2 mi), ending near Lago Hess.

[1] The Manso River is popular for whitewater rafting, especially in its course below Steffen Lake to the border with Chile.

The character of the river ranges from "peaceful"—the meaning of the word "manso" in Spanish—to Class IV rapids.

Sport fishing for the introduced species of brown, rainbow and brook trout in the river and its lakes is also popular.