Water Diversity in Spain: Factors Influencing Rivers, Lakes, and Aquifers
Water Diversity in Spain
A Water-Diversity in Spanish territory is influenced by a variety of human and physical factors. Climate plays a prominent role, as the availability of water in rivers, lakes, and aquifers depends on precipitation. Spain experiences both humid and dry conditions, influencing the organization of river basins, the capacity of rivers, and the formation of lakes and aquifers. Lithology affects surface runoff and water infiltration into aquifers. Vegetation acts as a radiation shield and reduces evaporation. Human activities, such as water consumption, irrigation, and the construction of reservoirs and diversions, also have a significant impact.
Spanish Rivers: Influencing Factors
1) Climate: Precipitation determines the absolute flow and regime of rivers. The absolute flow is the amount of water passing a given point per second. The fluvial regime refers to the seasonal variations in flow, which depend on precipitation patterns, including snowfall. Rivers in high mountain areas have maximum flows in spring or early summer due to snowmelt, with low flows in winter. The regime of other rivers depends solely on rainfall, or a mix of rainfall and snowmelt.
2) Topography: The relief determines the organization of basins and slopes, influencing river erosion and the construction of hydraulic works. A river basin is the territory drained by a main river and its tributaries, separated by divides. The Cantabrian slope drains 69% of peninsular rivers into the Atlantic, while the Mediterranean slope drains 31%. Steeper slopes increase river erosion. Hydraulic works are often favored by steep topography.
Hydrographic Slopes of the Peninsula
Rivers of the Cantabrian slope are short, originating in mountains near the coast. They have a large erosive force, especially if not protected by vegetation. These rivers are numerous, abundant, and have a very regular regime due to consistent rainfall. This allows for the construction of hydroelectric power plants. Rivers of the Atlantic slope are long, originating far from the Atlantic. They flow through plains and have an irregular regime with summer low flows. Mediterranean rivers, except for the Ebro, are short and have an irregular regime with significant summer low flows. They often experience catastrophic floods in autumn. Reservoirs are built to regulate flow and supply water for agriculture, industry, and population centers. Floods are frequent when heavy rain occurs.
Balearic and Canary Rivers
Rivers in the Balearic and Canary Islands are small streams with low water levels. In the Canary Islands, there is overexploitation of aquifers.
Spanish Lakes and Wetlands
Lakes in Spain are often small and seasonal. They can become clogged by sediment from rivers and surrounding lands, and by inappropriate practices such as water extraction for irrigation, well drilling, and drainage. Lakes can be classified as:
- Endogenous Lakes: Formed by internal forces of the earth. Tectonic lakes form in areas of faulting, while volcanic lakes are formed by erosion.
- Exogenous Lakes: Cirque lakes form in glacial valleys, while karst lakes are created by the dissolution of limestone. Arreic lakes are found in arid and semi-arid regions, where water accumulates in depressions. Saltwater lagoons are separated from the sea by a coastal barrier.
Wetlands are areas of land covered by shallow water, including lagoons, marshes, and deltas. They are important for biodiversity, serving as a transition between land and water and as a habitat for migratory birds. Examples include the Tables of Damiel and the Albufera of Valencia.
Aquifers
Aquifers are underground formations where water accumulates after infiltrating through the soil. Water can be extracted from aquifers through rivers, springs, or direct extraction. Overexploitation and pollution from human activities are major problems. Most aquifers are found in tertiary depressions near rivers and mountain headwaters. In the Balearic and Canary Islands, most water resources come from aquifers.