Swiss drought exposes islands—and leaves a border lake in crisis

Drought has reshaped two Swiss border-region lakes, exposing land that locals rarely see. Off Stäfa, Lake Zurich’s low water has revealed a small island around the Stäfner Stein. The lake stood at 405.24 metres above sea level, and the newly exposed ground is large enough for a small boat to moor nearby and for visitors to stop for a picnic.

Farther west, the Doubs has retreated from Lac des Brenets, which marks part of the boundary between France’s Franche-Comté and Switzerland’s canton of Neuchâtel. Grass and weeds now cover stretches of its exposed bed. At the lake’s northern end, water remains in a shrinking basin, while the waterfall where the lake ends has stopped flowing.

The two landscapes have drawn attention for different reasons: one has revealed a temporary island, the other is losing water, boat traffic and familiar shoreline. Both are visible signs of an exceptionally dry period across the region.

At Lac des Brenets, the water is retreating by as much as 22 centimetres a day. Yvan Durig, owner and captain of the lake’s navigation company, measures the remaining basin manually because the monitoring station now sits too far from the water. It has about nine metres of depth, against the usual 25 to 30 metres.

On October 1, the lake’s level fell to 735.34 metres above sea level, or 14.66 metres below where it should be. The record low set in 1906, a drop of 15.35 metres, was expected to be surpassed within days. A narrow stream now runs through weeds across the exposed bed.

Several forces have combined to drain the lake. Geological fissures allow water to escape underground, while rainfall has been below average and repeated heatwaves have intensified the drying. Switzerland recorded its hottest June, July and August since national measurements began in 1864. The Doubs normally forms the lake at Les Brenets after rising in France’s Jura mountains.

The disappearing water has shut down a summer livelihood and unsettled a community shaped by the lake. Durig halted boat operations on July 20, in the middle of the season. During a normal peak period, his company carries 200 to 300 people a day. Pontoons and dozens of boats now sit stranded on the dry bed.

The shoreline also carries personal memories. David Favre, a 76-year-old amateur local historian from Les Brenets, recalled summers spent swimming, fishing and jumping into the water as a child. He said the lake had become a source of “utter despair”. Favre said conditions had deteriorated since the drought of 2018, with the lake emptying every few years and, in his view, possibly soon every year.

Maxime Fallet, who works for a Doubs riverboat excursion company, fears the lake is “destined to disappear”. He described a sadness in Les Brenets when people discuss the Doubs, tied to the possibility of losing a place that has been part of local life for generations.

French and Swiss authorities have been discussing ways to slow the lake’s losses since 2022. A joint task force was established to examine options, including limiting the water draining through geological fissures. The work has yet to produce decisive action.

Durig wants the lakebed sealed. “We must take action -- indeed, be proactive -- and seal the lakebed,” he said. He measures the water level each day as the remaining basin contracts. For the navigation company, every lost day of the season has a direct cost; for Les Brenets, the water’s retreat is changing a defining part of the local landscape.

Lake Zurich’s exposed island is likely to remain visible for a while, with no prolonged period of rain in sight and the lake expected to take time to return to its normal level. At Lac des Brenets, the immediate marker is the approaching 1906 low-water record. The two lakes face different local consequences, but the retreating water is already shaping what residents and visitors can see and do.