Preferred strategy for the IJsselmeer area

The aim of the Delta Decision for the IJsselmeer Area is to preserve the functions of the IJsselmeer area in the future and to strengthen them where possible. In addition, the Delta Decisions for Flood Risk Management, Fresh Water and Spatial Adaptation are also important for this area. The ambitions in these decisions have been set out in greater detail in the preferred strategy for the IJsselmeer area. The implementation of the preferred strategy consists of specific measures for the IJsselmeer area. 

Flood risk management

By 2050, the primary flood defences (the defences that protect us against water from the sea, and from the large rivers and lakes) must comply with the statutory standards that have been in force since 1 January 2017. The level of water in the IJsselmeer and Markermeer lakes in the winter is very important here.  

The guiding principle is that the average winter level in the IJsselmeer area will not rise in line with the sea level between now and 2050. After 2050, a limited rise is an option; flexibility and adaptive rises in the water level in line with sea level rise are the main priorities.  

The water level in the IJsselmeer area is controlled with discharge sluices and pumps in the Afsluitdijk barrier dam. The strategy for flood risk management is based on the principle of ‘gravity discharge when possible, pumping when necessary’. Dike upgrades and the use of pumps on the Afsluitdijk are the main solutions in the IJsselmeer area to ensure that the standards for flood risk management continue to be met after 2025. 

Fresh water

The freshwater strategy focuses on two levels: the main water system and the regional water system. At the first level, securing the freshwater buffer is central alongside measures to tackle salinisation. At the second level, the focus is on retaining water in the regional system, reducing water use and tackling salinisation. 

In the IJsselmeer area, flexible level management is used to form the largest possible freshwater buffer. On the basis of current knowledge and insights, unless action is taken in the future, less water will flow to the IJsselmeer area through the IJssel river due to the uneven erosion of the riverbeds. This is because the bed of the Waal river naturally erodes faster than the beds of the Lower Rhine and the IJssel. It is unclear whether this can be prevented by flexible management of the Driel complex. This would involve closing the complex so that more water flows to the IJssel and the IJsselmeer area. If the discharge from Germany through the Rhine falls even further, bringing in water from the Amsterdam-Rhine Canal to the IJsselmeer area is an option. In the period between now and 2026, this issue will be explored through the Climate-Resilient Freshwater Supplies in the Main Water System strategy. 

The regional parties in the IJsselmeer area are committed to retaining water as much as possible and reducing the use of water by saving water and with smart water management. 

For a robust freshwater buffer, it is important to ensure that as little salt water as possible enters the IJsselmeer through the discharge sluices and locks in the Afsluitdijk. Rijkswaterstaat is looking at a range of options to achieve this, including collecting salt water in deep pits (salt traps) behind the discharge sluices.  

New developments requiring water have consequences for the freshwater buffer needed in the IJsselmeer area. For example, demand for drinking water could increase as a result of housing construction, the emergence of hydrogen plants for the energy transition, the construction of mega data centres and additional demand for water in the peatland areas to mitigate carbon emissions and land subsidence.  

The IJsselmeer Area Freshwater Stress Test demonstrates the need to reduce water shortages in the future and implement measures for salt management. This can be done by raising the water influx, reducing water demand or by not allowing new water users in the area. A policy framework for new water users is therefore becoming important. In the administrative agreement relating to the Updating of Water Allocation for the IJsselmeer Area, it was agreed to update the current policy framework. A new stress test will follow in 2024, providing a picture of which measures are needed to achieve the ambition of limiting water shortages in the IJsselmeer area to a frequency of once every twenty years. This is also part of the research for the periodical evaluation of the preferred strategy.  

Spatial adaptation as an integral component 

Spatial adaptation is a part of all plans and measures for the IJsselmeer area. An integrated assessment approach has been developed that links spatial development to the Water and Soil as Leading Factors policy paper, systemic measures and climate-robust planning. This integrated approach results in measures that serve multiple goals and obviates the need for a separate preferred strategy.