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How much does the lake warm or cool over the year? How does its oxygen level change? And how does its transparency and the development of algae fluctuate? To better understand its functioning, follow the evolution of the lake with the seasons.

Lake Geneva in spring

Warming and restart of algal development

In the spring, the campaigns of measurement of the quality of the water of the lake become bi-monthly again to follow the heating of the water and the restarting of the development of the algae in suspension in the water.

Winter mixing has led to the remobilization of nutrients (mainly nitrogen and phosphorus) necessary for algal development at the surface. The spring warming, combined with the increase in solar radiation, allows the restarting of algal growth in the nutrient-rich surface layer. The restart of the algae development is accompanied by a decrease in the transparency of the surface waters.

Algae are important to the functioning of the lake as they form the basis of the food chain. Most of them are not a problem, but some species are problematic: those that clog fishing nets, and toxic cyanobacteria.

(c) Maude Rion

(c) Maude Rion

The temperature of the waters of Lake Geneva in spring

Increased air temperature and longer daylight hours cause surface waters to warm up to about 30 m depth.


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Discover the latest data on temperature, Secchi transparency, turbidity and chlorophyll a concentration and their evolution.

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