In Emmerich, the water level fell to a historic low at the beginning of the week. This is not only a problem for shipping. In an interview, expert Daniel Bachmann explains what consequences low water still has and what needs to be done to reduce it in the future.
There is low water in the Rhine - a historic low of zero centimeters was measured in Emmerich on Monday. How extraordinary is the situation at the moment?
Daniel Bachmann: That is an extraordinary situation. In recent years, there have been repeated low water levels in our rivers such as the Rhine and Elbe. In 2018, many rivers fell below record low water levels. It was also relatively dry in 2019 and now again in 2022; It's unusual that this is happening so often now. Don't forget, we're still early in the year. Late summer, when there is usually little rain, is yet to come.
A low water level like this triggers a veritable chain reaction. What are the consequences of low water?
Such a low water affects different areas. On the one hand there is shipping: it is no longer possible to transport so much cargo per ship, supply chains are interrupted. The timing is of course unfavorable, now that hard coal and lignite are also being increasingly used again. Hydroelectric power plants may also have to be shut down because not enough water can flow through the turbines. In France, we also see that it can become a problem when there is a lack of cooling water for nuclear power plants. In addition, many industries take water from the rivers, which may now only be possible to a limited extent. And then of course there are many other factors: the whole ecosystem suffers, as does tourism and fishing.
There are early warning systems for floods. Is there something like this for low water?
That would certainly be possible. The question is whether you need some kind of early warning system, because low water is a rather gradual process in contrast to high water, which - in comparison - then comes "suddenly". When there is a flood, you can see the destruction immediately and immediately. In their everyday lives, people are initially less aware of low water. In the event of a flood, immediate readiness is required. A flood passes more quickly than a low tide, which can last for several months. From a purely hydrological point of view, you no longer feel a flood a year later - low water can still have an impact long after that, when the river bed is already full again.
Which are they?
Low water eats away at the groundwater levels. In Saxony-Anhalt, for example, the groundwater levels have fallen between 60 centimeters and one meter in the last four years. And that applies not only to the rivers, but to the entire area. If these large aquifers are full, you can survive a dry year if they are refilled the next year. But now there have been many dry years.
So the effects of low water become more serious the more often we experience it in a row?
Yes absolutely. The natural (groundwater) reservoirs, but also the technical reservoirs such as the large dams, no longer fill up when it is dry for a long time. This is of course a problem. In the case of the dams, which often also have flood protection tasks, there is also a conflict of interest: If we keep the dams full, not much can be held back in the event of a flood - if they are less full, it is harder for us to bridge low water phases.
You mentioned that dealing with high water can teach you a lot about dealing with low water. What exactly?
We are currently researching this as part of our research project DryRivers, funded by the Federal Ministry of Education and Research as part of the funding measure WaX - water extreme events. It's about transferring the risk management that already exists for dealing with floods to low water. Basically, it is a question of comprehensively considering the probabilities of low water events in combination with the resulting damage in risk management, including those for ecology and leisure.
What can be done to mitigate the damage caused by low water?
One is storage. Dams have a kind of reserve space that provides a certain amount of drainage for the water. One can also try to use the sponge city concept. Water could be stored here during heavy rain and used during low water episodes. But that is still being researched. Secondly, structural measures in bodies of water can reduce damage caused by low water: fairways in larger bodies of water for shipping or low-water channels in smaller bodies of water for ecology are examples. Thirdly, one could start on the industrial and private consumer side: it would be possible to save water or temporarily limit how much water may be withdrawn. The Federal Association of Inland Shipping calls for deepening of critical points in the fairway.
Do you think this measure makes sense?
I think that would make sense for the Rhine. The Rhine is used a lot and, with its connections to the major seaports and industrial regions, is an important artery for inland shipping. It's only a matter of a few places in the course of the Rhine.
Will we have to expect low water more frequently in the future?
We are in the process of climate adaptation. I am very much in favor of us doing everything we can to meet the climate targets. But we also need to think about how to deal with the consequences of climate change that we are experiencing right now. There is high water, but there is also low water.
How long does a low water phase like the current one in the Rhine usually last?
This can take a while. For it to end, it has to rain a lot, and it has to rain continuously. A few thunderstorms sweeping across the country are not enough. The river levels then rise again relatively quickly. In order to replenish the groundwater levels, we would need another rainy autumn and winter, and even that would probably not be enough. We will feel that for years to come - if we ever get the groundwater reservoir refilled.
How will we know that groundwater levels are low?
In extreme cases, the withdrawal of groundwater could be restricted, which would then affect the irrigation of the home garden, for example. The lack of water could also affect agriculture. I don't want to paint the devil on the wall: we will probably not have a drinking water problem in Germany. But there can certainly be limitations in other areas.
Charlotte Raskopf spoke to Daniel Bachmann
The interview first appeared on Capital.de.
