Low water is making inland shipping less reliable. More freight may move by road and rail, pushing up transport costs—and, eventually, consumer prices.

In August the Rhine at Kaub, a key measuring point in Germany, fell to just six centimetres, a record low, according to Reuters. The Rhine was not alone. Rivers across Europe, including the Danube in Hungary and Romania, the Po in Italy and the Loire in France, also reached exceptionally low levels.

Such conditions could become more common. Today, extremely low water levels might be expected to persist for about 40 consecutive days. In future, that figure could rise to 80.

Massimiliano Zappa, who heads meteorological forecasting at the Federal Institute for Forest, Snow and Landscape Research (WSL), told SRF that Europe has not experienced conditions like these since the 1940s. By the end of the century, he reckons, such episodes could occur twice as often.

That poses a problem for inland shipping. The effects were already evident this summer. On the Rhine, cargo vessels were sometimes able to carry only a fraction of their usual loads. Freight that would normally travel by river had to be shifted to roads and railways.

The result was a sharp rise in transport costs, particularly for heavy or bulky goods such as sand, fuel and grain. For such cargoes there are few cheap alternatives to shipping. A large inland vessel can carry roughly 100 times as much as a lorry while requiring far fewer workers.

Julia Arlinghaus, a professor of logistics and supply-chain management at the University of St Gallen, says road transport became markedly more expensive during the summer. At times, the cost of moving fuel from Rotterdam to Basel rose tenfold.

Swiss consumers felt the effect at petrol stations. Some estimates suggest that transport bottlenecks added about 16 cents to the price of a litre of fuel, says Ms Arlinghaus—almost 8% of the cost of filling a tank.

Some freight may shift from rivers to roads permanently. Studies suggest that, under an extreme climate scenario, about 4% of goods now carried by inland vessels could move to lorries in the long term.

That may sound modest. On the route to Basel, however, it would amount to a substantial increase in traffic. Ms Arlinghaus estimates that replacing that river capacity would require about 1,000 additional lorries a day.

Fuel is not the only product at risk of becoming more expensive. Building materials such as gravel and cement could also face higher transport costs. So could food. Large quantities of grain and animal feed travel by inland waterways, meaning that higher freight costs could eventually feed through into the prices of meat, eggs and bread.

The effect is difficult to isolate. Energy prices, harvests, labour costs and other pressures all influence what consumers pay. But as Europe’s rivers become less dependable, one of the continent’s cheapest ways of moving heavy goods may become less useful. The alternatives are costlier—and consumers are likely to bear at least some of the difference.

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