The German rivers carried very little to extremely little water for months this year. Such low water levels occurred “significantly more often than in previous years,” according to an evaluation by the “Science Media Center” (SMC) of the hydrological year 2025/26. The hydrological year ends on October 31st.
Soils, groundwater and rivers go into the winter with major deficits - the time of year in which water reservoirs normally fill up again, especially because significantly less water evaporates in the winter months.
The SMC relies, among other things, on figures from the Low Water Information System (NIWIS). Accordingly, the hydrological year 2025/26 was characterized by low water levels in nine major river basins in Germany. As early as January 2026, around a fifth of the discharges – the volume of water that passes through a river cross-section every second – were classified as “very low” or “extremely low”. In August and September, the proportion of these two categories was reportedly 35 percent.
In the Rhine region in September, around 54 percent of discharges were in the “very low” or “extremely low” categories – the average for previous years was only seven percent. In the Danube region, a full 87 percent of discharges were “very low” or “extremely low,” compared to five percent in previous years.
According to NIWIS, this classification is based on a comparison of current discharges with values from the corresponding season between 1991 and 2020. A discharge is considered “very low” if it is among the lowest five percent of the comparison values, and “extremely low” if it falls below the lowest one percent.
According to the information, the soils also experienced a severe drought. The winter of 2025/26 was drier than normal. In the summer, an “extreme drought” developed, especially in southern Germany.
Enno Nilson from the Federal Institute of Hydrology (BfG) told the Science Media Center that historically, low water levels on the Rhine were often winter events triggered by severe cold, ice and snow. “The fact that we now only experience summer low water levels caused by heat and drought fits into the picture that we have projected under the conditions of advancing climate change,” says Nilson.
He said: "In the past 30 days, around 37 percent of the usual precipitation was missing in the part of Central Europe that is hydrologically relevant for Germany, and in large parts of the Rhine and Danube catchment areas it was around 50 percent."
The now beginning of winter is actually the time when the waters fill up again. But it remains to be seen to what extent this will actually happen. It is clear that long and intensive land rains are necessary to really replenish the waters.
Projections show that in the foreseeable future there will still be a lot of water in Germany throughout the year, although it will be distributed very unevenly across the seasons. “More severe droughts and low water phases in the summer half of the year are partially compensated for by higher annual average precipitation and runoff in the winter half of the year,” predicts Nilson. “This would not necessarily create a water quantity problem, but rather a distribution problem between regions and between seasons.”
Christian Wolter from the Leibniz Institute for Freshwater Ecology and Inland Fisheries (IGB) in Berlin considers the 2025/2026 period to be the lowest in discharge since water level records began. Low water levels are also a result of human intervention: Since the 19th century, many German rivers have been straightened, shortened, fortified and expanded into waterways. This means that the water flows away much faster. Fortified banks also prevented the rivers from spreading. “Instead, their bottom deepens by several meters.”
Low water has a variety of effects on the living creatures in the river. A combination of low water and high temperatures is particularly critical. Low water levels can therefore affect the entire ecological functionality of a river. “The most effective measure to protect river ecosystems and their biodiversity is to revitalize the natural dynamics of rivers,” advised Wolter. “So we can’t just plan away or dredge away low water.”
A climate-adapted transport policy means aligning the infrastructure and shipping more closely with the natural water conditions. "These include, for example, smaller ships with shallower drafts. Dams are not a solution as they destroy the river landscape, promote evaporation and shift the drought problem further downstream."
Thorsten Wagener from the University of Potsdam confirmed that discharge volumes in many European rivers this year were at their lowest level in decades. “Due to the increasing influence of climate change, we are losing the natural snow and glacier storage in mountain regions,” said the professor of hydrological systems. “If this problem is combined with dry winter and spring and high evaporation in the hot summer, then we have a perfect storm – or rather a perfect drought.”
Thomas Hein from the University of Natural Resources and Life Sciences in Vienna warned that long periods of low water levels in highly regulated waters lead to a massive reduction in habitats along the river banks and in the adjacent floodplains. He recommended renaturation measures such as improved connections to floodplains or moorland wetting, which, however, would take a lot of time.
