Lakes and Groundwater Systems in the Iberian Peninsula

Lakes of the Iberian Peninsula

In the Iberian Peninsula, there are not many endorheic areas. In the majority of cases (within the catalog of Spanish lakes), the gaps are small with shallow surface depth; such level oscillations mean they often disappear in summer. These are small lakes that human action has dried and turned into agricultural areas. We can distinguish the following types:

1. Endogenous Origin

These are related to tectonic events or volcanoes. The largest lakes on the Earth's surface have this source and can be very deep. In Spain, the best example is La Janda.

2. Exogenous Origin

These lakes have a most varied typology and can be classified according to the generating agent into the following types:

• Glacial: These are produced by the action of glaciers in high mountains, whether by the digging action of the glacier tongue or by the obstruction of water caused by moraine deposits. The first are circular and the second are elongated; both are very deep. They are located in the highlands of the Andes. In the Spanish Pyrenees slope, there are over 400; in the Iberian Range, the Black Lagoon is located, and the largest glacial lake is Sanabria.
• Karst origin: These are located in basins excavated by the dissolution of water in soluble rocks such as gypsum and limestone. The most important are the Lagoons of Ruidera and Fuente de Piedra, as well as a good number of underground lakes.
• Arheic source: These are in depressed areas where rainwater gently collects and evaporates. They have variable dimensions and depth, and are characterized by significant seasonality.
• Gaps and coastal wetlands: These are located in coastal plains formed by the action of marine sediments and contributions from watercourses.

3. Mixed Origin

These are lakes of tectonic origin but are fed by waters of karst origin. Wet areas such as the lakes and ponds of Fuente de Piedra (Malaga) have great ecological interest.

Groundwater and Aquifers

Groundwater refers to water found in the subsoil where it has arrived by filtration of rainwater; the storage place is called an aquifer. Subterranean waters have been traditionally exploited through springs and wells. Their location has been an important factor in human settlement and the appearance of characteristic landscapes such as Mediterranean gardens.

Although Spanish aquifers represent a moderate amount, in areas of the south and east, the rates of groundwater extraction are very high. Today, many have been declared overexploited.