|Valle del Nalón||Caso|
|Bajo Nalón||Muros de Nalón|
|Camín Real de la Mesa||Las Regueras|
|Valle del Nalón||Langreo|
|Camín Real de la Mesa||Grado|
|Montaña Central||Ribera de Arriba|
|Camín Real de la Mesa||Candamo|
|Valle del Nalón||San Martín del Rey Aurelio|
|Bajo Nalón||Soto del Barco|
|Valle del Nalón||Laviana|
|Valle del Nalón||Sobrescobio|
|Birth||La Nalona (Puerto de Tarna).|
Between San Esteban de Pravia and San Juan de la Arena.
|Length||River: 142 Km.
Tributaries: 100 Km. m
The Nalón River has its source at La Nalona (Puerto de Tarna) maintaining a general NW direction until it is joined by the Narcea in the town of Forcinas (Pravia).
The Nalón River, without including the Narcea, covers the largest fluvial basin (3,692 square kilometres) and is the longest and largest river (145 km) in Asturias. The flow registered at Peñaflor bridge (Grado) reveal an average annual flow of 56.40 cubic metres per second and maximum and minimum daily flows of 1,250 and 3.40 cubic metres respectively.
The extension of its basin corresponds, almost exclusively, to the tributaries that flow into the river on its west bank, many of which have their source in the Cantabrian mountains between the Tarna and Leitariegos Mountain Passes (about 100 km. long), including the Narcea.
It flows into the Cantabrian Sea between San Esteban de Pravia and San Juan de la Arena, forming the Pravia Tidal River.
We must mention the River Caudal, 61 km. long, which covers an ample surface including the waters from the rivers Aller and Lena .
The Aller River, 42 km. long, covers a hydrographical basin of about 280 square kilometres and has an average annual flow of 10.88 cubic metres per second.
The Lena River, 32 km. long, covers a basin of 232 square kilometres and its average annual flow is 6.48 cubic metres per second.
The Trubia River, 46 km. long, includes a basin of 483 square kilometres and its average annual flow is 18.08 cubic metres per second.
The Cubia River, 41 km. long, is part of a basin of 210 square kilometres and its average annual flow is 5.13 cubic metres per second.
The tributary of certain importance at a lower level of the Nalón, on its west bank, is the Aranguín, in the town of Pravia.
On the eastern bank, however, the tributaries are much smaller. We can mention the River Nora which has its sources at Loma de Sariego and, after flowing for 67 km., it drains its contaminated waters into the Nalón NW of the town of Nora. This tributary covers a surface of 377 square kilometres, with an average annual flow of 20.98 cubic metres and maximum and minimum daily flows of 7.15 and 0.78 cubic metres respectively.