The secrets of Lake Kivu
An international and interdisciplinary team of researchers has published a work synthesizing all current knowledge about Lake Kivu. A lake that has been the subject of great scientific and industrial desire for well over a decade. An ecosystem with chemical, biological and geological characteristics that makes it totally unique.
A permanent lid 250 metres down
Lake Kivu is a meromictic lake, i.e., a lake whose surface waters and deep waters never mix. There are two main reasons for this: first of all, its depth and low exposure to wind, preventing convection through the force of the wind, which would normally mix the waters several tens of metres down. “Although the surface waters are currently colder, they contain less salt than the deep waters", explains François Darchambeau, researcher at ULg’s Chemical Oceanography Unit and co-editor of the work. “The deep waters are approximately 2°C warmer than the surface waters but, above all, they are far richer in salt (up to 6 grams per litre). This high salt content affects the density of the water and considerably increases the energy required to make the waters of the lake mix together fully. Since it is located at altitude of 1 400 metres and wedged between a volcanic chain whose peaks exceed 4 000 metres, therefore partially blocking the wind, this energy doesn’t exist. Hence, only the first 60 metres of the lake mix regularly, during the dry season."
(1) Jean-Pierre Descy, François Darchambeau, Martin Schmid and co., Lake Kivu, Limnology and biochemistry of a tropical great lake, Springer, 2012.