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Pirineos-Monte Perdido

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This will cross-reference all available documents in our data base related to the UNESCO World Heritage Site

Hydrology

The hydrological network on the Spanish side of the Pyrenees-Monte Perdido World Heritage Site is structured around five main rivers, the Ara, the Arazas, the Bellos, the Yaga and the Cinca, all of which receive water from their respective tributary gullies and from springs and seeps.
Given that this is a limestone massif, surface water is rare and is limited to the rivers, boggy areas and three lakes or tarns.

The volumes of water vary considerably due to the presence of numerous karstic formations such as potholes, dolines and seeps.

As in many other areas of the Pyrenees, the watercourses are torrents and so undergo considerable variation in flow volume over the course of the year.

Most of these rivers are pluvial and nival and are at their highest in spring as a result of the copious rain and the thawing of snow up in the mountains during this season.

The volume of water in the rivers at this time is known locally as mayenco, meaning snow and ice meltwater. The rivers are at their lowest in winter and summer, although convective storms in the hottest months can cause occasional major spates.

Broadly speaking, the watercourses in this part of the Pyrenees are torrents. As the water has to cover very steep gradients, it can reach considerable speeds and become very turbulent, providing the right conditions for mechanical erosion as well as the dissolving of the limestone rock.

The various aquatic organisms that live in these environments have developed various adaptive strategies to cope with their habitat.
Another of the factors to consider is the physical and chemical composition of the water, since this is closely related to the type of rocky substratum that it crosses and to its source (rainwater, meltwater or filtration).

Unlike in other massifs where impermeable materials such as granite predominate, there are few lakes or tarns in the Monte Perdido area as water cannot accumulate due to the characteristics of the limestone rock. There are just three masses of water in the protected area:

  • Frozen Lake: At an altitude of 2,980 m between the peaks of Monte Perdido and El Cilindro. The surface area of the lake is 4,000 m2.
  • Marbor or Tucarroya Lake: At an altitude of 2,600 m, this lake covers a surface area of 90,000 m2. It is regarded as one of the most beautiful in the entire chain of mountains, particularly because it is watched over by the hanging glacier on the north face of Monte Perdido.
  • Soum de Ramond Lake: This lake is located on the south side of this peak and formed recently following the thawing of a vast field of ice.

The peat bogs and boggy areas located in a number of depressions in the ground are of outstanding limnological and ecological interest. These spots are accumulations of meltwater or water from small springs. The most notable are to be found in various areas above the Carriata Cirque and also below the Brecha de Roland gap.