Lakes

Amazonian Lakes: From High Andes to Floodplains

The Amazon Basin has few large lakes surrounded by uplands. However, some slow-flowing river channel water bodies can function as lakes. There are two basic lake types in the Amazon Basin based on elevation: High Andean lakes and Floodplain lakes.

 

Conservando la Cuenca Amazónica Aguas Amazonicas

Flooded forest and floodplain lakes in Eastern Bolivia. Department – Country: El Beni – Bolivia Main Basin – Sub Basin: Madeira – Mamoré Main Stem Photographer: Luiz Claudio Marigo

High Andean lakes

The high Andean lakes, found at elevations usually above 3,500 m. The largest lake in the Andes is Lake Titicaca, but it does not drain into the Amazon Basin. Therefore, the largest lake in the Amazon Basin is Lake Junín located in Central Peru, in the upper Ucayali Basin at about 4,800 m. In addition, throughout the entire upper basin there are hundreds of smaller Andean lakes, usually called in Spanish lagunas rather than lagos, and many are fed, at least partially, by glaciers.

Floodplain lakes

The open water bodies that stud Amazonian floodplains represent the second type of lake and are found only in the Basin lowlands. In rivers that exhibit pronounced curves such as the Ucayali, Purús and Juruá, erosive processes can remove all the sediments from a meander. As a result, the river forms a new, straighter channel, abandoning the meander and becoming isolated from the main channel. This abandoned meander is known as an “oxbow lake”, due to its shape after separating from the main course, or “madrevieja” in Spanish, referencing its previous connection to the main river channel.

On the other hand, although the Amazon River has minimal meandering, its floodplain is not homogeneous and has numerous depressions where lakes are formed. During extensive flooding these lakes fill with water, which persists even during the low-water season, as water depth is sufficient to prevent colonization by forest. A very clear example of this type of process occurs in the Lower Basin, near Santarém, where the largest floodplain lakes are found, reaching areas larger than 50 km2 even during the low water period. This same process occurs in savannas. The largest savanna lakes in the Amazon Basin are in Eastern Bolivia, such as Lago Rogaguado and Lago Ginebra in the Llanos de Moxos.

Seasonal lakes, such as those recognized by the Ramsar Convention on Wetlands, also occur in the Amazon Basin. These are found on floodplains, savannas, and in some of the drier regions of the high Andes.

 

 

WETLANDS TYPES