IJsselmeer Region Delta Decision
The Delta Decision on the IJsselmeer Region involves three strategic choices: discharges into the Wadden Sea, the water level of the IJsselmeer, Markermeer and Randmeren, and the freshwater supply.
An important element of the proposed decision is that the average winter water level of the IJsselmeer remains the same up until 2050. The water will be discharged into the Wadden Sea using a combination of sluices and pumps. If the sea level and weather allow, water will be discharged using sluices. If this is not possible, pumps will be used to guarantee sufficient water is discharged. T enable this, more pumps will be built on the Closure Dike. This is far less expensive than allowing the water level to rise along with the level of the sea. For the period after 2050, allowing the water level to rise in a limited way in line with the sea level (by a maximum of 10 cm to 30 cm) remains an open option but only if this is necessary and cost effective.
The proposed decision also proposes making the target water levels more flexible. In this way, the water management authority can respond better to expected weather conditions and create a larger freshwater supply in the summer months. If the climate or the economy changes, the water supply and water consumption can be changed accordingly. It is important to keep supply and demand in balance. Using flexible water-level management, it is possible to increase the freshwater buffer in the IJsselmeer region step by step, and at the same time, cut demand.
With the first step in flexible water management, in the summer the freshwater reserve in the IJsselmeer, Markermeer and Zuidelijke Randmeren will rise by 20 cm. If demand rises, the buffer can be further increased to a “water slice” of 40 cm to 50 cm. To make flexible water-level management possible, the areas along the banks will be designed flexibly. After 2050, it may be desirable to have more water flow via the IJssel into the IJsselmeer in dry spells. Whether or not that will be necessary will depend on climate change.