Nervión

Nervión
Basque: Nerbioi
River
River Nervion with Zubizuri footbridge.
Country	Spain
Region	Basque Country
Districts	Álava, Biscay
Tributaries
- left	Kadagua, Galindo
- right	Altube, Ibaizabal, Asua
City	Bilbao
Source	Delika canyon
- location	Sierra Salbada, Álava, Spain
- elevation	1,000 m (3,281 ft)
Mouth	Estuary of Bilbao
- location	Bay of Biscay between Portugalete and Getxo, Spain
- elevation	0 m (0 ft)
Length	72 km (45 mi)
Basin	1,900 km2 (734 sq mi)
Discharge	for Portugalete and Getxo
- average	9.6 m3/s (339 cu ft/s)
Website: Greater Bilbao Water Authority

The Nervión river (Basque: Nerbioi) runs through the city of Bilbao, Spain into the Cantabrian Sea (Bay of Biscay). Its lowermost course, downstream of its confluence with the Ibaizabal River, is known as the Estuary of Bilbao.

The river is 72 kilometres (45 mi) long from its source at the Burgos and Alava provincial limits to the sea and runs in South to North direction. Soon after its source, the river forms a spectacular 300-metre (980 ft) waterfall in the Delika canyon (Alava) and then enters the Biscay province through the town of Orduña. It goes into Alava again through the towns of Amurrio and Llodio. Then the river runs again into the Biscay province until the Cantabrian sea, entering the Bilbao metropolitan area at Ugao-Miraballes. The tidal influence reaches 15 kilometres (9 mi) inland from the sea, at Bilbao's old town.

The main tributaries are:

Ibaizabal is considered by some to be an equally important river, so the whole system is often called Nervión-Ibaizabal and the final tract just "Estuary of Bilbao". The basin area is 1,900 square kilometres (730 sq mi).

Despite its current success in Spanish use, the traditional name of the stretch between the estuary and Basauri, where both Ibaizabal and Nervión merge, is Ibaizabal (meaning 'wide river' in Basque), according to historical evidence tracing back to the 11th century and up to the 20th. The literature writer native of Bilbao Miguel de Unamuno (1864–1936) as well as mayor of Bilbao Javier Ybarra (1913–1977) refer to it as Ibaizabal. Geological and hydrological data also seem to support that assumption.