Lac du Génépy

Lac du Génépy is a high-altitude glacial lake in the Savoie Alps, sitting in the commune of Aussois at the foot of the Labby Glacier, within the Vanoise massif. Its milky, turquoise-tinted water and the ring of granite peaks around it make it one of the most sought-after hiking destinations on this side of Vanoise National Park.

Where is Lac du Génépy?

The lake sits at roughly 2,900 m of elevation, tucked into a glacial cirque closed off by the peaks of Dent Parrachée and Rateau d'Aussois. It belongs to the commune of Aussois, in the Savoie department (Auvergne-Rhône-Alpes region), not far from Modane. The surrounding area falls within the core zone of Vanoise National Park, which means stricter nature-protection rules apply: camping is only allowed within a limited overnight window, and disturbing wildlife is prohibited.

How do you reach the lake?

The hike starts from the parking area at the dams (the "barrages") above Aussois, at around 2,000 m. From there the trail first heads toward the Refuge de la Dent Parrachée, at 2,511 m, then bends off behind the refuge, marked with the national park's yellow signposts, toward Lac du Génépy. About half an hour past the refuge, the path crosses a footbridge over a mountain stream before continuing up to the lake. The full ascent from the parking lot typically takes 3.5 to 4 hours one way, with close to 900 m of elevation gain. It's not technically difficult, but it is long and demands a reasonable level of fitness and sturdy footwear — better suited to experienced hikers than first-timers. Marmots are commonly spotted along the way, and ibex can often be seen higher up the slopes.

Why is the water milky?

The lake is fed by meltwater from the Labby Glacier, which hangs above it on the massif side. Glaciers grind rock into extremely fine particles — glacial flour — and it's this suspended sediment that gives Lac du Génépy its distinctive pale, opalescent colour, which shifts with the light and time of day. On the lake's right bank, a moraine marks how far the Labby Glacier extended during the Little Ice Age (roughly 1550–1850), when it reached considerably lower than it does today.

When is the best time to visit?

Given the altitude and how long snow lingers here, the trail is generally in full walking condition from June through September, though the lower sections can sometimes be reached from April onward. In peak summer, an early start is worthwhile — both because of the demanding high-mountain terrain and because wildlife tends to be more active in the cooler morning hours.

FAQ

How long does it take to reach Lac du Génépy? From the parking area at the dams above Aussois, plan on 3.5 to 4 hours of walking one way, depending on fitness and trail conditions.

Is the hike difficult? The route is long, with about 900 m of elevation gain, but it doesn't require climbing equipment. Sturdy trekking boots and some route planning — ideally with an IGN map — are recommended.

Can you swim in the lake? The water comes directly from glacial meltwater and stays very cold year-round, and the area lies within the national park's protected core zone, so swimming isn't practiced here.

What wildlife might you see on the way? Marmots and chamois are commonly seen along the trail, and ibex are often visible in the higher sections, both typical of Vanoise National Park's high-altitude wildlife.

Is this hike suitable for beginners? It isn't technically demanding, but the distance, altitude, and changeable alpine weather mean some prior high-mountain hiking experience is advisable, along with checking the forecast before setting out.