Rivers of the Iberian Peninsula: Atlantic Coast Drainage Basins

Atlantic Coast Rivers of the Iberian Peninsula

The Atlantic Coast river system consists of rivers that empty into the Atlantic Ocean. The water volume and surface area are greater than that of the Mediterranean rivers due to climate, westward tilt during the lithologic oro-alpina period, and more permeable materials. It comprises two sectors:

• Southern Sector: Located in the depression of the short rivers and Guadalquivir. These include rivers with a pluvial regime such as Guadalete and Tinto.
• Galician Rivers: These rivers form estuaries and are fast-flowing due to high humidity and short, impermeable river rocks. They originate at low altitudes, resulting in a pluvial regime. Examples include Miño, Tambre, and Ulla.

Miño River

The Miño's main tributary is the Sil. Both rivers originate in the mountains at higher altitudes, giving them a pluvio-nival regime.

Duero River

The Duero River originates in Pico Urbión and flows to Oporto. Its estuary basin is the largest on the Iberian Peninsula. Its flow increases from a pluvio-nival regime in the headwaters to a pluvial regime along the rest of its course. Right-bank tributaries provide most of its volume, such as the Pisuerga and Elsa. Left-bank tributaries, such as the Tormes, run parallel to the Douro.

Tajo River

The Tajo River originates in the Sierra de Albarracín and flows to Lisbon, forming an estuary. It is the longest river on the Iberian Peninsula. Its most important tributaries are the Jarama, Alberche, and Alagón, with right-bank tributaries being more significant than left-bank ones. It has a pluvio-nival regime at its headwaters and a pluvial regime in the rest of its course.

The Tajo's course is notable for its narrow gorges and is heavily altered by human interventions, such as reservoirs and the Tajo-Segura Water Transfer.

Guadiana River

The Guadiana River originates in the plains of La Mancha and empties into the ocean at Ayamonte, forming an estuary. It has a pluvial regime. Its flow is very poor because it originates at low altitude and passes through regions of low precipitation. Its few tributaries provide little water, including the Jabalón and Zújar.

The overexploitation of its headwaters has led to a drying up of its source. Its course is regulated by many reservoirs used to irrigate the plains (Plan Badajoz).

Guadalquivir River

The Guadalquivir River originates in the Sierra de Cazorla and flows calmly almost throughout its journey to sea level, reaching its mouth in a marshy area in Sanlúcar de Barrameda.

Like its tributaries (Guadalajara, Guadalimar, etc.), it originates at low altitude and has a pluvial regime. Only the Genil, one of its tributaries, originates at higher altitudes and has a nival regime in its headwaters.