Inland waterways: Could the season be coming to an end soon due to low water levels?

​From the tower of Überlingen Minster, Lake Constance looks almost Caribbean in mid-July. The popular webcam, which is viewed thousands of times a day, shows a fascinating phenomenon: diatoms are removing carbon dioxide from the water. This process produces tiny calcium carbonate crystals, which reflect the blue sky and the green of the algae to create a striking turquoise hue. This temporary growth of diatoms is beautiful, completely non-toxic and ecologically harmless. Above all, however, the low water level is not visible from this perspective – from here, the lake is still a paradise for water sports enthusiasts.

Various locations on Lake Constance

Things look very different at the other end of the harbour. “We already have five boats that are stuck in their moorings and can’t get out,” reports Mike Tuppen. He is the harbour master in Lindau-Zech. “Two weeks ago, it was still fine.” Since then, however, the water level has been falling. And there’s no end in sight. Even now, in the middle of summer, the affected owners are having to ask themselves how on earth they’re going to get their boats out of the lake in the autumn. The navigation channel is now only 1.20 metres deep, reports Tuppen, adding: “There are only berths left for motorboats.”

Lake Constance is a prime example of just how unusual the situation is on inland waterways across much of Germany. In winter, people are used to low water levels. Until now, in summer, these have been, at most, a temporary phenomenon.

Normally, the water level in Lake Constance fluctuates between 2.70 metres in March and 4.30 metres in summer. It currently stands at 3.05 metres – which is the winter level. However, all harbours and jetties are built to cope with the summer water level.

Huge quantities of water are missing

Across Germany, lakes are losing enormous volumes of water. According to the NIWIS low-water information system, the total loss over the last 25 years amounts to 60 billion cubic metres. That is equivalent to the combined volume of water in Lake Constance, Lake Starnberg, Lake Chiemsee, Lake Ammer and Lake Müritz. This water, which has flowed into the sea and not returned, is contributing directly to the rise in sea levels.

However, not all harbours are affected. In Hagnau, for example, harbour master Irena Willer reports: “Thanks to our new jetties and dredging work, we’re having no problems in the berths. This year, we’re absolutely swamped with enquiries from visitors.” Previously, the harbour was notorious as a ‘keel-kisser’. In Fischbach, too, people are keeping their cool. “We’re a dinghy harbour,” explains the harbour warden, who wishes to remain anonymous. With a draught of 60 to 80 centimetres, the jetties are still easily accessible. If in doubt, dinghy sailors simply raise the centreboard.

A significant water shortage on Lake Untersee

The water shortage is more evident on the Untersee. The water level there, at just 2.54 metres, is well below the summer average of 4.20 metres. Even in winter, it is usually half a metre higher. Martin Graf, who is in charge of the ports of Iznang and Moos, reports: “We now have permission to use stern anchors in the buoy field. The boats no longer drift, but lie as they would in a southerly wind.” However, problems arise in northerly winds or during thunderstorms. Graf: “If an anchor fails to hold, the boat crashes into the others and then drifts into the shallows.”

Two new finger jetties have already been built in deeper water, but many moorings at the access jetty are now dry. In Moos, Graf organised a yacht reshuffle. “We can still quickly bring yachts ashore with a draught of up to 1.20 metres; there isn’t enough water under the crane for any deeper draughts. We’ve already taken many out of the lake.” Their season, having only just begun, could already be over. “Some are still hoping for a major change in the weather, as happened last year; others have moved their boats to the Wäschbruck harbour in Radolfzell, opposite Moos,” said Graf.

We advise against sailing trips

There, in Wäschbruck, Pino Palumbo says: “We can still accommodate boats with a draught of 1.60 metres.” However, there is a guest fee of 17 euros per night. Normally, yachts come for a week’s holiday on Lake Constance, lower their masts before the three Rhine bridges in Konstanz, and raise them again once they’ve passed them. But due to the limited number of mooring options, these visitors are now staying away. Palumbo, too, advises against sailing trips because of the lack of moorings.

Long-term berth holders are filling the gaps, but some berth holders are critical of the way berths are being allocated. “The last of the deeper berths are taken, in case we run into problems ourselves,” says Palumbo. Two yachts with a draught of two metres have already been craned out – their season is over. And here, too, there is no end in sight. On the day of the interview, the water level dropped by a further two centimetres.

Shallow buoy fields on the Obersee

At Obersee, Sylvie Schneider from the Wasserburg Water Sports Club reports: “Inside the outer jetty, the boats still have enough draught. But it’s shallow in the buoy field.” This can be dangerous. A dinghy cruiser, for example, ran aground there during a storm, sprang a leak and sank – as far as it could. The water rescue service had to salvage the boat.

The situation on the Rhine is coming to a head

Further north, on the Rhine, the situation is also coming to a head. Jutta Handloser from the Oberwinter marina reports: “We’ve got 60 centimetres in the entrance; at times it was as little as 20.” Last week, a sailing boat got stuck in the entrance, sucked mud into its engine cooling system and had to be towed to a jetty – a floating landing stage – by the fire brigade and the water police. In any case, there is no longer any space for leisure boats on either side of the navigation channel. Handloser: “I’m telling everyone who doesn’t need to go out: just stay put where you are!”

In Neuss on the Rhine, Karl-Peter Lux from the Novesia Yacht Club explains: “The cargo ships already have to navigate right up to the groynes – those are the breakwaters here on the Rhine.” Fortunately, the harbour has been dredged, so larger yachts still have enough water under their keels. “Our sailors are on the IJsselmeer anyway,” adds Lux. This means he can lend a hand to his colleagues at the Düsseldorf Sailing Club across the river, whose harbour is already too shallow.

The situation is also critical at Lake Chiemsee

The situation is similar at Lake Chiemsee. Arnold Kotschisch, harbour master in Seebruck, reports an extremely low inflow of water. Lake Chiemsee flows unregulated into the Alz next to its harbour. Hardly any water is coming in from the two tributaries, the Prien and the Tiroler Achen. There was a brief downpour in mid-June; since then, only a trickle has been flowing into Lake Chiemsee.

Kotschisch: “With a draught of 1.50 metres, we’re running out of space here. The yachts can stay, mind you, but they won’t be able to leave.” Not even to the crane – there isn’t enough water beneath the hook either. Kotschisch has taken in two boats from other harbours; their owners are now also paying for two berths. At least the steamer jetty at Seebruck is once again being served by coastal shipping; for a short while, there wasn’t enough water there either.

In Breitbrunn, Andreas Jell says: “A sailing boat with a draught of over 1.80 metres will soon no longer be viable on Lake Chiemsee.” Nevertheless, he remains calm: “In the leisure sector, you can adapt. There are more important things.”

Enormous economic consequences

In early July, the Federal Institute of Hydrology reported: “Water levels and discharge rates in all free-flowing German inland waterways have fallen.” This also has economic consequences, particularly for commercial shipping. “The 135-tonne freighters – that is, those meeting the European standard – are now sailing with only a third of their capacity, whilst the 110-tonne vessels, which are slightly smaller, can still carry half their capacity,” explains Karl-Peter Lux from Neuss.

A considerable amount of cargo is being loaded onto lorries, but they cannot replace the entire freight capacity. At the Baden-Württemberg Institute for Lake Research, its director, Walter Hetzenauer, is currently dealing with an unusually high number of interview requests. This is understandable, as 77 per cent of all monitoring stations in the federal state are recording extremely low or very low water levels, with no immediate prospect of improvement. As well as water levels, the institute’s scientists are keeping a close eye on water temperatures. “However, critical oxygen concentrations have not yet been reached at any monitoring station,” says Hetzenauer.

Even a look back at 2025 is alarming

Back in March, the review of 2025 had already stated: “Too warm, with a pronounced heatwave.” It was 1.9 degrees warmer than the average for the years 1961 to 1990, whilst June was as much as 4.4 degrees above that average.

As far as water levels are concerned, there is a contrasting trend. Summer and winter are apparently becoming more similar. However, hardly any conclusions have been drawn from this so far. Admittedly, “there is a need for action”, according to a statement backed by the state government. On the other hand, Baden-Württemberg held the chairmanship of the International Lake Constance Conference for two years. And even the feasibility study on climate neutrality in Lake Constance shipping, carried out three years ago, has resulted in measures that are, at best, only measurable on a seismic scale.

Water levels in Switzerland are also low

Water levels are also low in Switzerland. The Mannenbach jetty on the Untersee has become too shallow for passenger boats. At Lac de Brenets, the water level is a full seven metres below normal, with boats and jetties sitting on dry land. The water level there has recently been falling at a rate of 22 centimetres a day.

The ice reserves in the Alpine glaciers are under severe strain; on 29 June, the Swiss glacier monitoring network GLAMOS reported that the winter’s snow reserves had already been used up. Since 1880, this has only happened once before, in 2022.

Despite the clear figures, some people refuse to face reality. Low water levels, as one often hears, were a feature of the past too. Things will sort themselves out. It’s much like the mantras of Black Forest ski lift operators, who hope for stable snow conditions in the years to come after every mild winter.

Impact on water sports still manageable

In fact, the impact on water sports is relatively minor. At least when compared with the environmental and economic consequences: a decline in the value of facilities and businesses associated with water sports.

To make matters worse, less water heats up more quickly. According to the authorities, toxic blue-green algae are already appearing off Eriskirch and also off Lindau. Anyone who swallows water here risks skin irritation and diarrhoea. And unlike the diatoms off Überlingen, blue-green algae aren’t even pretty to look at.