Water Resources in Spain: Rivers, Lakes, and Wetlands
**Factors Influencing Water Resources in Spain**
Several factors influence the availability and distribution of water resources in Spain:
- Weather: Plays a crucial role in determining the quantity and distribution of water in rivers, lakes, and aquifers. Precipitation patterns create a contrast between “wet Spain” (with sufficient precipitation) and “dry Spain” (with pronounced summer droughts).
- Relief and Topography: Influence the organization of watersheds, the erosive capacity of rivers and lakes, and the formation of aquifers.
- Lithology: Rock type and its characteristics can favor surface runoff or facilitate water infiltration and the formation of aquifers.
- Vegetation: Influences water availability.
- Human Beings: Consume water for irrigation and supply, attempting to compensate for this expenditure through regulatory frameworks and infrastructure development.
**Spanish Rivers**
Factors Influencing Non-Peninsular Rivers
a) Climate: Determines the absolute flow and regime of rivers. (Absolute flow is the quantity of water passing a given point in the river per second, and the river regime refers to seasonal variations).
- Snowy Regime Rivers: Originate in mountains, with maximum flows occurring in late spring or summer due to snowmelt.
- Rainwater Regime Rivers: Flow depends solely on precipitation.
- Mixed Regime: Can be pluvio-nival or nivo-pluvial.
b) Relief and Topography: Determine the organization of watersheds and hydrographic basins. (A hydrographic basin is the territory whose waters flow into a main river and its tributaries. A hydrographic slope is the set of basins that flow into the same sea).
Peninsular Hydrographic Slopes
- Cantabrian Slope Rivers: Short, originating in mountains close to the coast. They have high erosive power, especially if the slopes are not protected by vegetation. These rivers are numerous, with a regular flow regime due to abundant precipitation.
- Atlantic Slope Rivers: Long, as they originate near the Mediterranean and flow into the Atlantic.
- Mediterranean Slope Rivers: Short, except for the Ebro, due to the proximity of the sea to the mountains where they originate. They are often gullied, with a very irregular regime.
**Spanish Lakes and Wetlands**
Lakes
Generally small and seasonal.
a) Endogenous Lakes: Caused by internal forces or phenomena of the Earth.
- Tectonic Lakes: Formed by land subsidence due to the action of folds or faults.
- Volcanic Lakes: Located in the craters of ancient, dormant volcanoes.
b) Exogenous Lakes: Originated by external phenomena or forces such as erosion caused by ice, water, or wind.
- Glacial Lakes: Formed from the excavation of cirques by ice in a glacial valley.
- Karst Lakes: Originally created in depressions due to the dissolution of limestone or gypsum.
- Arheic Lakes: The most common type of exogenous lake, characteristic of arid or semiarid regions.
- Wind Lakes: Excavated by wind action on soft materials.
- Coastal Lakes or Lagoons: Salt lakes separated from the sea by a coastal barrier. Many are found in the Guadalquivir, Mar Menor, and at the mouths of some rivers.
Wetlands
Wetlands are extensions of shallow terrain, in some cases intermittently covered by water (they may disappear in the summer). These include deltas, *albuferas* (coastal lagoons), and peat bogs. These areas are of great biological interest, hosting many species adapted to aquatic and terrestrial environments, and especially for being a nesting and stopover site for migratory birds. Notable examples include the Daimiel National Park, the lagoons of Toledo, Albacete, the Ebro Valley, and Ciudad Real, the Guadalquivir delta, the Ebro delta, the *Marismas del Odiel* (Odiel Marshes), and the lagoons of southern Valencia and the Mar Menor.