Rivers. They flow into the Atlantic: the Adour, in the municipality of Anglet, whose most important tributaries are the Saison, Biduza, Aran, Ardanabia and Errobia (Nive). The small Uhabia, the Ugarana (Nivelle) and the Helbarren, the three Laburdine. The Bidasoa, with its Navarrese and Laburdino-Gipuzkoan character. The Oiartzun, the Urumea, the Oria, the Urola, the Larrondo and the Deva, carry all the waters of Gipuzkoa to the sea. Four small rivers: the Artibai, the Lea, the Mundaka and the Butrón, together with the great Nervión and the Somorrostro form the Biscayan river network. The Nervión has six main tributaries: Ibaizábal, Gobelas, Udondo, Asua, Kadagua and Galindo. All the other Basque rivers, descending through the lands of Alava and Navarre, carry their waters to the Ebro, which is for the Basque Country like a kind of inland coast. Four major rivers are tributaries of almost the entire southern river network: the Zadorra, the Arga, the Ega and the Aragon. But there are also other independent rivers that flow directly into the Ebro. These include the Omezillo, Bayas, Linares and Odrón, Alhama and Queilles.
Translated with www.DeepL.com/Translator (free version)