Five questions about the consequences of the severe weather in Switzerland

Severe weather in Switzerland. The water is so high that many holiday areas flood. There are also landslides and sometimes falling boulders. What effect does the high water level in the Alps have on the Netherlands? Bas Boterman, senior advisor water management and crisis management and Jasper Stam, senior advisor crisis management and information provision of Rijkswaterstaat, answer five questions.

1. When do high water levels occur at Lobith? (where the Rhine enters)?

"High water levels in the Rhine are caused by a combination of meltwater from the Alps and prolonged or heavy precipitation in large parts of the Rhine basin." According to Boterman and Stam, it is important to emphasize that extremely high water on the Rhine does not just happen. "A multitude of factors influence this such as snow melt, intensity and duration of precipitation, the area where that precipitation falls and the saturation of the soil. If all these factors coincide in an unfavorable way, extreme situations with very high water levels arise."

2. How does Rijkswaterstaat warn of very high water levels? Who monitors what and what is acted upon?

"In the Water Management Centre (WMCN) in Lelystad, experts monitor the current and expected water levels 24 hours a day, 365 days a year. Reports on the expected water levels are available to everyone on waterinfo.rws.nl and on a specific site. If the expected water levels exceed the established limit values, the WMCN warns water managers and safety regions of high water and informs via flood notification several times a day about how the high water is developing and what is expected in the coming days. With this information, these organizations then take the necessary measures to prevent damage and victims. Think of the timely evacuation of floodplains, the construction of temporary barriers (for example at Nijmegen, Deventer, Kampen) and the establishment of dike monitoring."

As with other stormy weather, these warnings use color codes (yellow, orange, and red) to indicate the severity of the situation. With color code yellow we speak of an increased discharge situation and standard measures are taken, but the consequences remain limited. Code red is issued for serious and exceptional situations where large-scale emergency measures are required. Stam explains that there is intensive cooperation with the KNMI. "Because the water level forecasts depend to a large extent on the weather, the experts of Rijkswaterstaat work intensively with meteorologists from the KNMI within the walls of the Water Management Centre. For the Rhine specifically, the WMCN makes water level forecasts up to 14 days ahead. These can also be found on a special site."

3. Suppose it rains heavily for a long time in Switzerland, how long does it take before the water reaches our country? Do we also receive warnings from abroad?

"From Basel (Switzerland), water takes more than five days to reach the border with the Netherlands. Only heavy precipitation or snow melt from Switzerland can never lead to an extreme high water situation," boterman emphasizes.

Stam explains how we work together with neighbouring countries. "The countries in the Rhine basin cooperate a lot through institutionalised partnerships. Rijkswaterstaat, for example, works together with the relevant organisations in Germany, Belgium, Luxembourg, France, Austria and Switzerland to make water level forecasts. For example, the measuring systems are linked and knowledge and data are exchanged on a regular basis. Think, for example, of information about the snow supply in the Alps, water levels and weather data and the management of reservoirs. But also new insights to achieve better water level expectations and adjustments in the course of the river."

"Only heavy precipitation or snow melt from Switzerland can never lead to an extreme high water situation"

4. What are situations that lead to high river levels?

"This depends on the extent to which the water level peaks of the German tributaries Moselle, Main and Neckar coincide with each other on the main stream of the Rhine. For exceptional high water situations, precipitation in the German part of the catchment area is particularly decisive. For example, at the beginning of 1995, the Rhine reached an extreme discharge of 12,000 m3/s. Prior to reaching this water level, the German part of the Rhine basin averaged approximately in twelve days. 160 mm of precipitation," boterman said.

Only extreme precipitation (as in June 2023) in the Alps will generally not lead to extreme water levels in the Netherlands, Stam emphasizes. "This is because the high water peak will level off before it reaches the Netherlands. In Switzerland, the high water peak is still steep and short. As soon as it reaches the Netherlands, the peak is lower but lasts longer. The peak is also dampened because it first passes through a number of reservoirs."

5. Finally. Does RWS also indicate what people can do in the event of such a warning?

"Yes. Attention is also paid to what people can do, which is mainly initiated by our ministry and the national ongoing theme campaign Ons Water. On the website Overstroomik.nl , for example, you can see how high the water comes to you in the event of a flood. And give tips on the measures you can take. Also on onswater.nl you can find tips and facts about flooding but also drought. So yes, we have sites to warn but it is not a direct task for us to inform citizens. This is largely the work of the security regions."

For more information, visit the Covenant's climate page .