Lac de Grand-Lieu
| Lac de Grand-Lieu | |
|---|---|
 |
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| Location | Saint-Philbert-de-Grand-Lieu, Loire-Atlantique |
| Coordinates | 47°05′N 1°40′W / 47.083°N 1.667°WCoordinates: 47°05′N 1°40′W / 47.083°N 1.667°W |
| Type | Natural |
| Primary inflows | Boulogne, Ognon |
| Primary outflows | Acheneau |
| Catchment area | 700 km2 (270 sq mi) |
| Basin countries | France |
| Surface area | 62.92 km2 (24.29 sq mi) Summer: 35 km2 (14 sq mi) |
| Average depth | 1.6 m (5 ft 3 in) |
| Max. depth | 4 m (13 ft) |
| Surface elevation | 5 m (16 ft) |
| Islands | 3 |
Lac de Grand-Lieu is a lake located to the south-west of Nantes, in the Loire-Atlantique, France, and almost entirely in Saint-Philbert-de-Grand-Lieu. At an elevation of 5 m, its surface area is 62.92 km², making it the largest lake in France in winter, but second after Lac du Bourget in summer.
The lake is classified as a Local Nature Reserve, and use of boats on the lake are prohibited for all but a small number of licensed professional fishermen.
Due to the lake classification, as a protected area, its access is restricted. Navigation on the lake is prohibited, only seven professional fishermen have been assign a specific authorisation to do so. Because of its small topography, and its wild vegetation, the lake is difficult to access. Except during the winter floods, it is only accessible from a few locations, such as at Bouaye in the north, at Pierre Aigüe in Saint-Aignan-Grandlieu and la Chevrolière in the east.
For visitors, a museum has been created to present the lake and its ecosystem as well as the history of local fishermen. An observatory allows tourists to have a look at the wildlife in its natural habitat.
An exhibition on the lake is offered at The lake House at Grand-lieu in Bouaye and a tour is also available at The old Guerlain Pavillon which overlooks the lake.
In the site the soil was formed about 50 million years, the current topography around two millions years ago, and the transformation of the current landscape took shape during the Neolithic period. Six thousand years ago the areas which had not been filled by the sand were covered by a dense forest. The deposits of this forest build overtime and it is today the fifth largest in France. It contains around 29 million cubic meters of peat. The bottom of the lake is composed of various deposits and their thickness can reach about thirty meters. Aquifers containing fresh water have been formed in these layers. An analysis at carbon 14 has been used to date that water, the result showed that is water would be locked up for 8 700 years.
Before the creation of a piping work during the 18th century, the water of the lake was release via the large swamp close to the island of Couetils, then join the course of the Tenu river which cross this zone before reaching the large Loire river. The zone where the junction with The Tenu occur was made close to the island Marguerite (area which was originally called the three channels)
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Wikipedia