LAC DE LA MOUCHE

Lac de la Mouche is held back by a 410 m-long semi-viaduct dam built between 1881 and 1890. The 94-hectare lake can be easily circumnavigated on foot or by mountain bike on a 7 km ride. You can admire the reflections of the villages of St-Ciergues and Perrancey, and the forests that dominate the lake.

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Fun tour also available on the Id-Vizit app:
Lac de la Mouche and the underwater legends
Together, we'll discover the lake, you on the hiking trail, and me below the water. This lake is known as the most natural of the 4 lakes in the Langres region. In spring, from April to June, the waters are so clear that we can dive right in! Look closely, and you might even see the bubbles of our diving friends, who have also come to take advantage of the visibility offered by this lake. You know, when we dive, we think of legends and monsters, each more bizarre than the last. But do you know all these stories?

For nature lovers :
Lac de Saint-Ciergues, or réservoir de la Mouche, is one of four artificial reservoirs in the Langrois region created at the end of the 19th century to ensure the navigability of the Marne-Saône canal in summer. Its eutrophic waters occupy the bottom of a deep valley in the Langres Plateau, which has resulted in a relatively steep slope (never less than 5%). This biotope is characterized by its highly variable water level, depending on the time of year and the needs of the canal (fairly low in late summer and autumn).

Vegetation :
These particular conditions favor a special type of vegetation, stabilized a long time ago and depending on the humidity gradient: submerged vegetation with, in particular, an algae of the "lustre-d'eau" type, quite rare as it tends to regress in polluted water, amphibious vegetation and, at the hinge of these two groups, the water plantain with grassy leaves, a remarkable species which had never been reported in Haute-Marne before and which is proving to be abundant at Saint-Ciergues. These are followed by abundant stands of sedge and baldingera, which are massive on the lakeshore and dominate the appearance of the riparian vegetation. They are home to a rare species, marsh germander, which is on the red list of plants in Champagne-Ardenne, but is well adapted to temporary flooding and has occasionally large populations here. Meadow vegetation resistant to the mechanical pressure of waves and winter flooding is found on the upper part of the banks (with angular garlic, a rare species protected in Champagne-Ardenne), relayed by tall-herb vegetation more nitrophilic at the limit of maximum water extension. The two main streams of the La Mouche reservoir and the dozen or so rivulets flowing around its perimeter support the development of specilized amphibious vegetation associated with flowing water.

Fauna:
Avifauna is well represented here, although less abundant than in some other reservoirs in the region (few landing zones and mudflats). Nevertheless, the lake attracts many migratory bird species, and autumn brings waterfowl, some of which overwinter here: coots, ducks, grebes, shelducks, teal and scaups. Great grebes and coots breed here. The reedbed conceals the nesting grounds of a number of passerines, and various birds of prey frequent the site. Nearly sixty species have been listed, including 34 protected species and some on the national, regional and Birds Directive red lists. The lake is also an important site for the reproduction of amphibians, particularly frogs.
The state of conservation of the ZNIEFF is good, although the proliferation of fires (concentrated in the flooded trampled meadow) destroys significant areas of interesting vegetation, as does the over-use of the reservoir in summer, which leads to severe degradation of the banks and vegetation belts near the tarmac roads by trampling and parking.

DATAtourisme France