IJsselmeer Area

The IJsselmeer area is at the heart of Dutch water management. It harbours special assets for nature and cultural history. The Afsluitdijk barrier dam has provided the entire area with more protection and made land reclamation possible. It also created a freshwater buffer that benefits drinking water supplies, agriculture, industry and nature in much of the Netherlands. Society as a whole uses the lakes and their shores in many ways, for example for leisure activities and shipping.  

Challenges

The sea level is rising, possibly faster than expected. This makes it more difficult at current lake levels to discharge IJsselmeer water into the Wadden Sea. At the same time, more river water flows into the IJsselmeer in extremely wet conditions. For example, the level of the IJsselmeer and Markermeer lakes reached record highs in the 2023-2024 high-water period, not least because the wind restricted the options for discharging the water. If we do nothing, flood risk management in the IJsselmeer area will come under pressure and problems with excessive water in areas outside the dikes will become more frequent.  

During longer dry periods, the IJssel River brings in less water and Rijkswaterstaat maintains the freshwater stocks by discharging less water. This can lead to salinisation. It will be necessary to respond by managing the level of water in the lake, particularly because economic developments, mitigating land subsidence and the effects of climate change are also expected to result in more demand for fresh water. Given these developments, the amount of work required in the IJsselmeer area is increasing.  

Generic Delta Decisions

To preserve the functions of the IJsselmeer area in the future as well, it is important to respond flexibly to developments and new insights. The basis for this has been set out in the three generic delta decisions of the Delta Programme: Flood risk management, Fresh water and Spatial adaptation.  

In addition, there is a Delta Decision for the IJsselmeer area that includes decisions made on the basis of the national interest. It specifically addresses water level management in the IJsselmeer and Markermeer lakes in relation to the freshwater supplies, flood risk management and water discharge into the Wadden Sea. The 2015 Delta Programme and the National Water Programme (NWP) state that the national government will maintain the average winter level in the IJsselmeer and Markermeer until 2050 in line with the Water Level Decree for the IJsselmeer Area (which was adopted in 2018). This Decree also safeguards a layer of water of 20 cm for freshwater supplies by introducing a flexible water level during the summer. Water is discharged from the IJsselmeer to the Wadden Sea by a combination of gravity discharge and pumping (from late 2026 onwards) at the Afsluitdijk barrier dam.  

Preferred strategy for the IJsselmeer area

A preferred strategy for the IJsselmeer area has been drawn up elaborating the details of the delta decision. It defines goals and measures for keeping flood risk management and freshwater supplies up to standard, and for increasing flexibility. Regional visions of the future and planning for investments with a long life cycle are very important here.  

• Flood risk management:  
  • To maintain the long-term average winter level in the IJsselmeer and the Markermeer. 
  • Gravity discharge when possible, pumping when necessary. 
  • Moderate management of the lake level peaks after 2050. 
  • Option: a rise in the level of the lake in the winter of up to 30 cm after 2050. 
• Freshwater availability:  
  • Flexible water level management in the IJsselmeer and the Markermeer during the summer period. 
  • A frugal approach to water and reducing use. 
  • Option: increase the summer bandwidth from 20 cm to a maximum of 50 cm after 2050.