Future discharges in the Rhine and Meuse: lower in summer and higher in winter
Expert(s) |
Frederiek Sperna Weiland
|
Joost Buitink
Deltares, Rijkswaterstaat and the KNMI have been working together for the Ministry of Infrastructure and Water Management to formulate the insights from the latest climate scenarios in terms of the implications for the discharge regime of the Rhine and Meuse rivers. The analysis shows that the mean winter and spring discharges will rise in both rivers.
In the summer half-year (March to August), mean discharges will continue to decrease due to less precipitation and higher evaporation in the Rhine and Meuse catchments. The total discharge in the winter half-year (September to February) will increase because of rising temperatures.
KNMI’23 scenarios result in new insights for future discharges
On 9 October 2023, the KNMI published the KNMI’23 climate scenarios for the Netherlands. These new scenarios show that we will be faced with an acceleration in sea level rise, higher average temperatures, drier summers and wetter winters. At the same time, extreme weather events will occur more frequently, and the summers may experience heavier showers.
Implications for discharge scenarios for the Rhine and Meuse
All the new discharge scenarios show lower river discharges for the Rhine and Meuse in the summer half-year. The decrease varies between 10 and 30% for 2100. We can now therefore say with more confidence that discharges will be lower in the summer half-year. For both the Rhine and Meuse, the mean winter and spring discharges will be higher. Rising temperatures will lead to the gradual disappearance of the glaciers in the Alps. The thickness of the snowpack in the Alps will also strongly decrease over the course of the century.
More precipitation will fall as rain (instead of snow), increasing the mean winter discharge and reducing the contribution of meltwater to the Rhine. As variations and extremes increase, the challenge for water managers will be greater, both in the Netherlands and in our neighbouring countries. The discharge scenarios are based on the current situation and they are policy-neutral.
Looking far ahead: after 2100
For the first time, these new national discharge scenarios provide an opportunity to look at the situation after 2100. A total of fifteen climate scenarios were analysed to determine the effects on Rhine and Meuse discharges. In the most extreme scenarios, the mean low discharges will continue to decline after 2100 and maximum discharges are likely to increase further.
Both the dry and wet scenarios indicate that the mean summer discharge will be lower than in the KNMI’14 scenarios. Because higher discharges in winter and lower discharges in summer cancel each other out, there will be virtually no change in the annual mean.
Follow-up
These discharge scenarios specifically represent the climate effects on the mean and low discharges. Research into the impact and effect of the discharge scenarios will be conducted in follow-up studies, including policy studies such as the Freshwater Delta Programme, the Sea Level Rise Knowledge Programme, the Climate-Resilient Freshwater Supplies in the Main Water System Programme and the Integrated River Management Programme.
The Delta Scenarios will be published in early 2024. They will combine the climate and discharge scenarios with the socioeconomic developments affecting water demand and upstream discharges. In the course of 2024, Deltares, working with Rijkswaterstaat and the KNMI, will publish a report as a follow-up to the current study. It will address future changes in high and extremely high discharges.
