Drainage basins

DRAINAGE BASINS 

A drainage basin is an area of land that drains all its water into the same sea, ocean or lake. Spain has three main drainage basins.

The Cantabrian Basin: 5% of all the water. The sources of most rivers in this basin are in the Cantabrian Range. The rivers are short and have the most stable regimes of all Spanish rivers.

The Atlantic Basin: 65% of all the water. Most rivers here flow through the Meseta and the Guadalquivir Depression. They have variable regimes. The Iberian Peninsula slopes to the west, so most of the water on the peninsula drains into the Atlantic Basin.

The Mediterranean Basin: 30% of all the water. All the rivers here, except for the Ebro, are short. They have variable regimes and, in some cases, they are dry in summer. There are no permanent rivers in the Balearic or Canary Islands or Ceuta and Melilla.

The Atlantic Basin

The rivers of the Atlantic Basin flow into the Atlantic Ocean. These rivers are divided into two groups.

Rivers in Galicia are short with a high discharge and stable regimes. The main ones are the Eume, the Tambre, the Ulla and the Miño, with its tributary, the Sil. The Miño creates a physical border with Portugal.

Miño 

Rivers in the Meseta and the Guadalquivir Depression are long with a high discharge and variable regimes. They begin in mountains inland, and cross areas that have rain in autumn and spring.

Tajo

Guadalquivir

Guadiana

Duero

                       

The Mediterranean Basin

The rivers of the Mediterranean Basin flow into the Mediterranean Sea. The rivers in the east vary in length. They have a low discharge and extremely variable regimes. The exceptions are the rivers Ter and Ebro.

The rivers in the south, like the Guadiaro, are short because they start in the Penibaetic Range near the coast. They have a low discharge and variable regimes.

The main reservoirs in the Mediterranean Basin are Mequinenza (Zaragoza), Alarcón and Contreras (Cuenca), and Almanzora (Almería).

Llobregat

Ebro

Turia

Júcar

Segura

The Cantabrian Basin

Rivers in the Cantabrian Basin flow into the Cantabrian Sea. They flow though Asturias, Cantabria and the Basque Country. These regions have heavy rainfall all year. The rivers have a high discharge and stable regimes.

They are short because their sources are close to the sea. The Cantabrian Basin is a good location for reservoirs  because there are many steep valleys.

Eo

Navia

Bidasoa

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