Lake Rocha SAM-09

Riparian Nation(s) Uruguay
Surface Area 72 km2 Mean Depth 0.58 m Volume 0.04 km3
Shoreline Catchment Area 1312 km2 Residence Time
Frozen Period None Mixing Type Polymictic Morphogenesis/Dam
Related Info/Site


Uruguay has several coastal lagoons in the southeastern and eastern part of the country. Many of them, including Laguna de Rocha, are comprised in the Biosphere Reserve designated by Man and the Biosphere Program (MAB) of UNESCO.

Like most recent lagoons, Laguna de Rocha was formed through the rise of sea level during the last 6,000-8,000 years. It is separated from the Atlantic Ocean by a sand bar, which is sometimes opened by wave action and thixotropy as well as artificially. The intrusion of salt water during open-bar periods produces a clear gradient of salinity that controls physical and chemical water parameters. There are five inflowing rivers, of which the Arroyo Rocha (average flux 13.4 m3 sec-1) and the Las Conchas are the most important. This lagoon is known for its production of fish, crab, shrimp and molluscs harvested by fisherman families living on its southern shore.

The Limnology Department, Faculty of Sciences, Univ. de la Republica, has been studying the lagoon system since 1986 and is currently constructing a limnology station which is expected to serve also as an operative centre for researches on other coastal lagoons.

Photo of Lake Rocha
Photo: R. Sommaruga