With summer coming to an end and winter approaching, concerns about heat waves, forest fires and drought seem long ago. But although more than a hundred millimeters of rain fell in the Netherlands last month, according to the Ministry of Infrastructure and Water Management, there is still an ‘imminent water shortage’. In particular, the water level in the Rhine reached record lows this year. How did that happen? If you look further back than last summer, you can see that this has actually been going on all year. This is apparent from an analysis by NRC of the water flow through the river, based on data from Rijkswaterstaat and the German and Swiss environmental services. A wet month of February and two rainy weeks in April could not prevent the drainage and water level in the Rhine from decreasing. “Even if you compare it with 2018 [also a very dry year], you can see that the low water discharge started much earlier this year,” says Marit van Tiel, who studies the hydrology of glaciers at the University of Freiburg. A runner along the dried up Rhine near Cologne in Germany. Photo Friedemann Vogel Houseboats are on dry land in the Waal near Nijmegen in August 2022. Photo Piroschka van de Wouw One of the hunger stones in Worms, Germany. In times of drought and low water levels, people used to write warnings on stones there, often with dates, although there are doubts about the correctness of the dates Foto Tilman Blasshofer / Reuters Photo Yann Schreiber / AFP) This does not only apply to the river downstream. According to the Swiss environmental service Bundesamt für Umwelt, the summer water discharge in the Swiss Rhine has not been so low since the start of the measurements. The contrast with the summer of last year is great. At that time, heavy rainfall for weeks led to major flooding in the Rhine and Meuse, especially in Germany, Belgium and the southern Netherlands. That flood claimed at least two hundred lives in Germany and Belgium, thousands of people had to leave their homes. Much less snow The low water level this year was not only due to little rain in the river basin, says Van Tiel. “Due to the drought, there was much less snow than usual in the Alps this winter. And that melted even earlier in the year because of the high temperatures.” The glaciers are therefore in a very bad state, while they, together with snow, are important for the Rhine. Especially in summer and autumn, the meltwater compensates for part of the low amount of precipitation in the rest of the catchment, sometimes up to a fifth of what flows through the river. This year clearly shows the consequences of the high temperatures and drought in the Alps, agrees Matthias Huss. He is affiliated with the Swiss university ETH Zurich and director of Glamos, an organization that monitors the state of glaciers in the Alps. “In August, snow melt made almost no contribution to the drainage of the Rhine, even though snow would normally still melt. On the other hand, the glaciers did melt hard this summer, making a greater contribution to the water flow than normal.” In fact, the glaciers have never melted as fast as this year , according to measurements taken by Huss and other researchers last month. The reservoirs lost about three cubic kilometers of ice this year, more than 6 percent of their total volume. Normally, losses of 2 percent are considered extreme. A big difference with the drought of 2018 is that a lot of snow fell in the Alps, so that the glaciers remained better protected against solar radiation. The snow melting so quickly this year was probably also caused by the Saharan sand that descended from North Africa into Europe in March. Normally the white snow reflects radiation well, but the dark layer of sand absorbed more heat. Despite the rain in recent weeks, researcher Marit van Tiel does not see this year’s shortage being fully supplemented any time soon. It will have to rain heavily for a long period of time. “And the lowest water levels can often be seen around September and October.” A view on the future This year’s developments show how the dynamics of the Rhine can change in the coming decades. As glaciers retreat, meltwater from the Alps contributes less and less to water discharge into the Rhine, researchers from the International Commission on the Hydrology of the Rhine Region concluded in a report last June. The committee is a collaboration between researchers from countries through which the Rhine flows. If greenhouse gas emissions do not go down, most glaciers will probably have disappeared by the end of this century. In the long run, for example, the water supply is almost exclusively dependent on the amount of precipitation. And that is problematic. When water levels are too low, ships can no longer sail, agriculture and industry may use less water. It shows how dependent people are on rivers and how big the problems can become during prolonged drought. Low water also leads to all kinds of other problems. For example, with a low discharge, the water heats up faster when the temperatures are high. The average water temperature of the Rhine is already about one and a half degrees higher than a century ago. This can affect biological processes and in the long run be harmful to animals and plants that live in the river. When water levels are too low, ships can no longer sail, agriculture and industry may use less water The quality of river waters is important, says Klaas Groen, department head at Rijkswaterstaat and Dutch representative in the International Commission for the Hydrology of the Rhine region. He points out that rivers and reservoirs in the Alps are used, among other things, for electricity generation, and downstream in Germany for industry and electricity generation. The International Commission for the Protection of the Rhine also emphasized this important function of the Rhine in 2018 in a study on low water levels over the past century . The consequences of low water for society and the economy have increased, the report states. But contrary to popular belief, the researchers write, the long periods of low water in the Rhine in the first half of the 20th century could actually be more intense and last longer than later in that century. The research largely attributes this to the arrival of reservoirs in the Alpine region, with which the water supply can be somewhat regulated. Particularly downstream, prolonged periods of low water are less common than in the past. But: with climate change, it looks like the Rhine will take on a more erratic dynamics again, and we will have to deal with low water more often. The Rhine catchment area is starting to resemble that of rivers such as the Tigris and the Nile, says Klaas Groen of Rijkswaterstaat. “There is still plenty of water upstream, but less and less downstream.” According to him, it is therefore important that countries make mutual agreements about how they deal with the uses of such a river, especially in a time of climate change. For example, how much water agriculture and industry are allowed to use. Graphics Fokke Gerritsma and Roos Liefting . Design Sanne van Griensven A version of this article also appeared in the newspaper of October 7, 2022