The environment of this section is the typical transition between the Andean forest and the Patagonian steppe.
Its coasts are lined with vegetation. In the first 3 or 4 km the river runs smoothly and without much riparian vegetation which intensifies more and more downstream.
The third section of the lower Manso River, of about 50 kilometers in Argentine territory, is again of a gentle course with few rapids. It runs south until it receives the contribution of the Villegas and Foyel rivers; from that point it runs almost exactly west, traversing a wide and deep valley, with stretches of woods, others of open grasslands, and some swamps. It is clearly transparent in color, without cloudy or greenish tones.