Measures and work

• More space for water
  The water level at peak load will rise from +0.15 metres to +0.18 metres NAP. This is because the planning area has become slightly smaller. As a result, the water level may rise by 3 centimetres.
• Relocation to Hooiweg
  The boundary of the area will be relocated to Hooiweg. This means that no new embankment will be needed along lake Leekstermeer. This is better for the tranquility of the nature reserve.
• New and modified weirs 
  There will be two new weirs will at Hooiweg. The existing Doolhof weir will also be modified. The fixed thresholds at lake Leekstermeer will remain as they are.

• Raising embankments
  The existing embankments in the area will be raised. This will keep the area safe during high water levels. 

We are redesigning nature in a number of places in the area. This will enable the plants and animals in the area to cope better with the extra amount of water. This will make nature stronger and more robust, even under more extreme weather conditions.

We take various measures to protect and strengthen nature:

• The area between Hooiweg and lake Leekstermeer will not be involved in the balancing lake, as it is an important nature area.
• We are making the banks of ditches less steep so that marshland nature can grow. This is good for birds such as the bittern.
• We are expanding the wetland area so that plants and animals that thrive in water can live there.
• We create "refuge mounds" for animals so that they have a safe place to go during high water.
• The water only stays in the area for a few days. After that, it flows away again. This ensures that nature is preserved as much as possible.

We are expanding De Onlanden balancing lake, additional measures are needed to keep the area safe and accessible. For example:

• Pumps at the Zanddijk and Sandebuur pumping station are being reinforced and will have greater capacity.
• Roads such as Woudrustlaan and Roderwolderdijk will be raised.
• Access roads for TenneT and Gasunie will be modified.
• Homes on Roderwolderweg and Moleneind are protected against water.
• A concrete path on the Weeringse dyke will be raised and will function as dyke.
• Low sections of the Drentse dyke will be raised to prevent damage.

These measures ensure that people remain safe and that water can be drained away effectively.

The pumping station will be enlarged. This will enable it to drain water more effectively during heavy rainfall. Currently, the water cannot always be drained quickly enough during extreme rainfall.
If the water level rises temporarily after heavy rainfall, the modified pumping station will ensure the water level returns to normal more quickly.

The new pump can drain 1.5 litres of water per second per hectare. This complies with the latest climate standards. The work is scheduled for 2026 or 2027. Until then, an extra pump will be used in case of emergencies.

In the autumn of 2025, construction began on two new weirs at Hooiweg/Matsloot. We are also modifying the Doolhof weir. The weirs will be completed in 2026.

The remaining work, such as raising embankments and implementing nature measures and additional measures, will also start in the first quarter of 2026. The complete expansion of the balancing lake will be completed in 2027.

Current information can be found under Work.

 

An ecological work protocol applies during the work. This ensures coordination between ecologists from the water authority and the contractor. A number of measures are being taken to protect nature: 

• Earthworks are carried out outside the breeding season. This also applies to work that generates a lot of noise, such as installing sheet piling.
• The sheet piling of the weirs positioned in such a way that animals cannot enter the construction pit. 
• The construction pit is pumped dry under ecological supervision; fish and other aquatic animals are captured. 
• A fence will be erected along Hooiweg. This will prevent otters and other animals from crossing Hooiweg during the work. 
• The supply and removal of soil and materials takes place on existing roads and paths, and also on road plates. 
• Measures are in place to prevent pollution.