The Water Framework Directive defines a river basin as the area of ​​land whose surface runoff flows entirely through a series of watercourses. These watercourses can be rivers and, potentially, lakes flowing to the sea through a single outlet, estuary, or delta. The river basin, as a unit for water resource management, is considered indivisible. Therefore, all river basins in Spain have different characteristics.
In this article we are going to tell you all the characteristics and importance of the hydrographic basins of Spain.
Hydrographic basins of Spain
Each basin is further divided into sub-basins. We define these sub-basins as the area of ​​land whose surface runoff flows entirely through a series of streams, rivers, and eventually lakes. This water runoff flows towards a point in a watercourse, which is generally a lake or a river confluence. From this confluence, a larger river is formed, flowing towards the sea. Let's look at the main river basins of Spain and their characteristics.
Duero hydrographic basin
This is the river basin that runs through the northwest of the Iberian Peninsula and flows into the sea at Porto. It has a surface area of ​​approximately 97,290 km², of which 81% lies within Spanish territory and 19% within Portuguese territory. It is the largest river basin covering the entire Iberian Peninsula.
Ebro River Basin
This is the river basin that flows through the northeast of the Iberian Peninsula. It begins in the Sierra de HĂjar mountain range and reaches its mouth at the Ebro Delta. Its drainage basin covers approximately 85.000 square kilometers, making it the second largest in the entire Iberian Peninsula. Most of the rainfall that feeds the Ebro River originates in the Pyrenees Mountains to the north. To learn more about this important river, you can consult the article on the Ebro River and the facts and interesting details about the rivers of Spain.
Tagus River Basin
This is the river that runs through the western part of the Iberian Peninsula and flows into Lisbon. Its area is 78,467 km², distributed as follows: 66% (55,645 km²) in Spain and 34% in Portugal. It is the third largest river in the Iberian Peninsula.
Guadiana hydrographic basin
It is the one that runs through the center and southwest of the Iberian Peninsula. Its mouth is located between Vila Real de Santo AntĂłnio and Ayamonte, making the border between Portugal and Spain. The number of main tributaries of this hydrographic basin is 137. This means that there are 137 rivers that feed all ecosystems with abundant water. Among the rivers that make up the Guadiana watershed are the following: the Guadlamez, the Bullaque, the Estena, the ZĂşjar, the ZapatĂłn, the Gevorra, the Murtigas stream and the Ardila stream, to name only the contributions of more than 90 HmÂł. of natural form.
Hydrographic basin of the Guadalquivir river
It is the most important in the south of the peninsula. It is located entirely in Spain. Its extension is 57.527 km and extends through 12 provinces belonging to four autonomous communities, of which Andalusia represents more than 90% of the surface of the basin. The geographic space of the Guadalquivir demarcation is configured and delimited by various elements. On the one hand, we have the steep edges of Sierra Morena to the north. In the southern part we have the Betic mountain ranges and in the part close to the sea the Atlantic Ocean.
The climate of this entire region is Mediterranean. Among its characteristics, we see that it is temperate and warm, with an average annual temperature of 16.8 degrees Celsius. Rainfall is irregular, averaging 550 liters per square meter. The territory's location, open to the Atlantic, means that oceanic storms with a westerly component penetrate the area. These storms are responsible for the distribution of rainfall, with their fronts advancing in a southwest-northeast direction. Once they reach the Iberian Peninsula, rainfall reaches its maximum levels on the highest peaks that border and define the Guadalquivir River basin. This rainfall is often torrential, meaning that long periods of drought alternate with high temperatures that cause erosion.
When rainfall occurs in torrential downpours, it happens sporadically but intensely. In other words, when precipitation falls, it usually does so heavily, leaving a large amount of runoff that ends up damaging ecosystems and crops. To learn more about the effects of drought in this basin, you can read the article on the effects of drought in Spain and the situation of reservoirs in summer.
Hydrographic basins of Spain: JĂşcar
This part includes all the basins that discharge into the Mediterranean Sea. We start from the margin of the left part of the Gola del Segura and at its mouth with the Cenia river. The total extension is 42.988,6 km² and extends through the provinces of Albacete, Alicante, Castellón, Cuenca, Valencia and Teruel, as well as a small area in the province of Tarragona.
Hydrographic basins of Spain: Segura river
The Segura River Basin is the one that runs through the southeast of the Iberian Peninsula and flows into the Mediterranean Sea. Its surface area is approximately 18.870 km² , affecting four autonomous communities: the Region of Murcia (almost entirely), the Community of Andalusia (provinces of JaĂ©n, Granada, and AlmerĂa), Castilla-La Mancha (province of Albacete), and the Valencian Community (province of Alicante). It is administered by the Segura River Basin Authority (CHS).
Importance of the hydrographic basins of Spain
As we know, a country's water resources are based on the sum of its surface and groundwater volumes. River basins are responsible for storing as much surface water as possible. To do this, reservoirs are built whose main purpose is to collect river water for storage. This water is used for various purposes, including domestic use, agriculture, and industry. You can find information about the current state of Spain's reservoirs in 2024 and the effects of drought in Spain.
I hope that with this information you can learn more about the hydrographic basins of Spain and their main characteristics.