Lake area
Length of the banks
Maximum depth
Average volume
Average altitude
of the water body
Dwell time
theoretical waters
Watershed area
from Lake Geneva*
Permanent population
in the watershed**
*The Lake Geneva watershed is the entire territory where surface water flows into Lake Geneva. It extends mainly across Switzerland (cantons of Vaud, Valais, Geneva and Fribourg) and France (departments of Haute-Savoie and Ain). It is fed by several rivers, including the Rhône , its main tributary, as well as the Arve, the Dranse, the Venoge and the Aubonne.
**Data for France: 2017 – Data for Switzerland: 2018
In winter, lake water quality measurement campaigns return to a monthly schedule, as the development of algae in suspension in the water slows down. In fact, it's at this time of year that the surface waters are the most transparent.
Winter circulation adds oxygen to the lake by mixing oxygen-rich surface water with deep water, which contains less oxygen due to the decomposition of algae. In the case of a complete winter circulation, the oxygen deficit is fully compensated. In the case of repeated incomplete winter mixing, as has been the case since winter 2012-2013, the oxygen deficit at the bottom of the lake widens. At present, the lake lacks oxygen at depth, with adverse consequences for aquatic life and the release of phosphorus and certain metals trapped in the sediments.
Winter mixing also brings the nutrients needed for algae growth (mainly nitrogen and phosphorus) to the surface. But the cold, combined with low solar radiation, means that algae suspended in the water cannot develop immediately.
Cold and windy spells mix surface water with deep water. Winter mixing is complete if the lake waters manage to mix all the way to the bottom. Otherwise, mixing is said to be incomplete. The more severe the winter, the greater the mixing depth.
Discover the fascinating real-time dynamics of the waters of Lake Geneva thanks to two innovative models, designed by researchers in the region, revealing the movements and temperatures of the lake.
Discover the latest temperature, Secchi transparency, turbidity and chlorophyll a concentration measurement data and their evolution.
