- Cangas del Narcea, Pravia, Belmonte de Miranda, Salas, Tineo Central and Western Asturias
- Extension: 102 Km. km 2
It has a surface area of 1,135 km2 and a length of 123 km, and is the second largest river in Asturias. It rises in the Fuentes del Narcea and flows into the river Nalón at Forcinas (Pravia), part of its upper course being in the Fuentes del Narcea, Degaña and Ibias Natural Park.
It has several very fruitful fishing preserves in terms of salmon catches, making it one of the most "salmon-producing" in the Principality.
Plant life
There are abundant oak groves, which are distributed throughout the Natural Park.
The birch groves are very well represented, with important extensions, for example in the upper Naviego basin.
Alongside the extensive wooded formations are the no less extensive degraded and deforested areas, which are currently covered by different types of scrub.
Other plant formations of great interest and relatively abundant are the sphagnum bogs and the vegetation complexes of ponds and lagoons.
Wildlife
Undoubtedly, the most relevant faunal element within the area considered is the Cantabrian brown bear. The bear finds here the appropriate conditions for its development and survival: extensive forests, relatively inaccessible refuge areas, etc.
The wolf also maintains an important population in this sector, with stable breeding areas and the presence of relatively important family groups.
Another mammal with protectionist status is the otter, present in most of the rivers running through the area with varying degrees of abundance.
Artiodactyls are also represented here. Roe deer are very abundant in the large expanses of woodland and scrubland.
Among the birds of greatest interest is the capercaillie, with a notable presence for the region as a whole.
Reptiles and amphibians are also widely represented, especially those associated with wetlands.
The most important tributaries are the River Naviego-Cibea and the Pigüeña with its tributaries the River Somiedo, the River Saliencia and the River del Valle.
Other tributaries are: the river Nonaya, the river Arganza with its tributary the river Pomar, the river Coto, the river Muniellos, the river Onón with its tributary the river Junqueras and the river Genestaza.