Edité le 07/08/2007

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Le Guide du Patrimoine naturel de la Région Rhône-Alpes "Le Lac d'Annecy" est sorti.
Disponible en Français sur simple demande auprès d'Asters : 04 50 66 47 62

GPN_LAN_couv.jpgRésumé en anglais
Guidebook of the natural heritage: Lake Annecy

This unique mountain lake, with steep cliffs and wooded slopes, offers you its secrets. From the last glaciations during the Middle Ages, via the periods of development of a craft and country lifestyle, the lake had always constituted a shrine to brighten up human populations. Center of tourism and sports activities, Lake Annecy is today known and recognized for its pure crystalline waters that continue to forge its reputation in France and the world.

Between city and nature

Juxtaposition of natural spaces and urbanized banks entails a fine organization of the territory: protective measures of natural spaces and water quality management have allowed the preservation of the exceptional character of the place. Since the 1960s, efforts have been made to save both the quality of water and life in the lake by creating a waste water collection network and natural areas such as wetlands near the open water.Today, Lake Annecy is in good shape! Its exceptional transparency shows it. It is classified in the category of lakes with clear waters and medium productivity. Scientists speak about oligotrophic lakes.

Valuable reeds

During the 20th century, aquatic reed beds moved from one hundred hectares to only eleven. Since 2007, the main causes of their regression have been identified: its fragilisation by building ports, pontoons, artificially protecting of banks and by the stabilization of the lake level since 1965. It is necessary to protect reed beds for their functions of purification, protection of banks against erosion, accommodation of animals and for their landscaped interest. Therefore, since 2011, the SILA Intercity Syndicate for Lake Annecy have been carrying out important works of ecological engineering. The on-going scientific follow-up has already brought encouraging results.

 A vast container

Four main rivers bring approximatively 60% of the surface water in the lake. Everywhere around the lake, limestones are affected by the rainwater, creating a real underground that leads water from the top of the mountains to the lake. The Thiou is the single outlet in Annecy. 

From the precursory geologic wrinkling to the work of the glaciers

During the Cretaceous period, up to 250 meters of reef limestone settled. The convergence of the tectonic plates entails the closure of the alpine ocean then the collision of continents creating subalpine relief. During the last 2.6 million of years, about thirty glaciations shaped the lake's basin.

Natural habitats shaped by the relief

After the retreat of glaciers, communities of flora and fauna have developed and adapted themselves to the constraints of sloping, richness of the soil, wind and temperature. On the banks and flat grounds, wetlands, which are rich in biodiversity, coexist next to agricultural areas.