The Oria is a river in the Basque Country at the north of the

Iberian Peninsula The Iberian Peninsula ( ), also known as Iberia, is a peninsula in south-western Europe. Mostly separated from the rest of the European landmass by the Pyrenees, it includes the territories of peninsular Spain and Continental Portugal, comprisin ...

. It's one of a series of Basque rivers flowing into the

Bay of Biscay The Bay of Biscay ( ) is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Point Penmarc'h to the Spanish border, and along the northern coast of Spain, extending westward ...

(

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

basin) and the main river of the province

Gipuzkoa Gipuzkoa ( , ; ; ) is a province of Spain and a historical territory of the autonomous community of the Basque Country. Its capital city is Donostia-San Sebastián. Gipuzkoa shares borders with the French department of Pyrénées-Atlantiqu ...

in volume (25.6 m³/s), length (75 km) and basin (882.5 km²), the main feature of these rivers aligned south to north being their shortness. The maximum elevation at the source is 1,260 m, while at its lowest height the tidal influence extends inland up to

Usurbil Usurbil () is a town and region located in the province of Gipuzkoa in the Autonomous Community of the Basque Country, in the North of Spain. It lies in an area well known for its sagardotegiak (cider houses) and the area adjacent to the river ...

(estuary). On this final stretch, many marsh and wetland strips dotted the banks of the Oria, although some of them have been drained for agricultural and building purposes. The river rises at the south of the municipality of

Zegama Zegama, popularly known as "the shadow of Aizkorri", is a town and municipality in the Goierri region of the province of Gipuzkoa, in the autonomous community of the Basque Country (autonomous community), Basque Country, northern Spain. Nature an ...

near the hamlet of ''Otzaurte'' and the San Adrian tunnel, harvesting the waters of the north-eastern side of the mountain range

Aizkorri Aizkorri or Aitzgorri (, meaning in Basque 'bare stone', literally 'red stone') is a massif, the highest one of the Basque Country (autonomous community), Basque Autonomous Community (Spain) with 1,551 m Above mean sea level, AMSL at its hig ...

, so the river results from the merging of several streams. The first town it crosses is the very nucleus of

, with other major towns of

being located on the river, e.g.

Beasain Beasain is a town and municipality located in the Goierri region of the province of Gipuzkoa, in the Autonomous Community of the Basque Country, northern Spain. It has an important industry of railway vehicles and related equipment ( CAF) that ...

Ordizia Ordizia, formerly known as Villafranca de Ordizia, is a town and municipality located in the Goierri region of the province of Gipuzkoa, in the autonomous community of the Basque Country, northern Spain. The professional cycle road race Prueba Vi ...

, Tolosa,

Andoain Andoain is a town in the province of Gipuzkoa, in the autonomous community of Basque Country, in the North of Spain. Nowadays it has a population of 14,637 inhabitants (2019), which has been quite stable since the 90s. Andoain is located where t ...

Lasarte-Oria Lasarte-Oria is a town located in the province of Gipuzkoa, in the Autonomous Community of Basque Country (autonomous community), Basque Country, northern Spain. It was founded in 1986. It is estimated to have a population of around 19.000 people ...

and finally Orio at the mouth. From

to Orio, the sinuous and traffic laden coastal road N-634 winds along. The Oria is a central river and an important axis for the province of

. The major road A-1 (European route E-5 E-80) runs along the Oria most of the time, as well as the Spanish Northern Railway, right from its rise on the slopes of

. Its watershed holds a population of 128,000 inhabitants, most of the lowland being heavily inhabited, while the area of its southernmost stretch is sparsely populated.

Environmental condition and fauna

The banks of the river were intensely industrialized starting in the middle of the 19th century and later; the river grew conspicuously polluted up to the 1980s, with almost all its river fauna becoming extinct. At that point, its environmental situation began to revert, the river showing currently a healthy condition. There exists an unstable

trout Trout (: trout) is a generic common name for numerous species of carnivorous freshwater ray-finned fishes belonging to the genera '' Oncorhynchus'', ''Salmo'' and ''Salvelinus'', all of which are members of the subfamily Salmoninae in the ...

population downstream of Andoain, while other fish prevail and remain steady, i.e. ''

Cyprinidae Cyprinidae is a family of freshwater fish commonly called the carp or minnow family, including the carps, the true minnows, and their relatives the barbs and barbels, among others. Cyprinidae is the largest and most diverse fish family, and t ...

'' such as

barbel Barbel may refer to: *Barbel (anatomy), a whisker-like organ near the mouth found in some fish (notably catfish, loaches and cyprinids) and turtles *Barbel (fish), a common name for certain species of fish **''Barbus barbus'', a species of cyprini ...

(''Barbus graellsi''), ''ezkailu'' (''

Phoxinus ''Phoxinus'' is a genus of freshwater fish in the family Leuciscidae of order Cypriniformes, and the only members of the subfamily Phoxininae, or Eurasian minnows. The other species in this genus are also commonly known as minnows. The name "minn ...

phoxinus'') and ray-finned fish ('' Chondrostoma toxostoma arrigonis''). A stretch of the estuary by the village ''Aginaga'' is known for its baby eels, bred and harvested for human consumption before they grow up, providing for a much appreciated and dearly paid delicacy, while they were totally neglected just some decades ago.

Main tributaries

There are several streams and small rivers flowing into the Oria. The main tributaries are

Leitzaran The Leitzaran (, or Leizarán in Spanish) is a river and a valley in the Navarre and the Basque Country (Spain). It flows into the river Oria from its right. Its source is in the Leitza municipality in Navarre, and it is long. It enters int ...

and Araxes in Tolosa.

References

{{DEFAULTSORT:Oria (River) Rivers of the Basque Country (autonomous community) Landforms of Gipuzkoa Rivers of Spain