and those emptying into the Cantabrian sea (a marginal sea of the Atlantic off the northern coast of the Iberian peninsula).

Tributaries are listed down the page in a downstream direction. The main stem river of a catchment is labelled as , left-bank tributaries are indicated by , right-bank tributaries by . Where a named river derives from the confluence of two differently named rivers these are labelled as and for the left and right forks (the rivers on the