De Onlanden nature reserve, which is located close to Groningen, can already absorb 7.5 million cubic meters of water. But given climate change, that is not enough for the future. To ensure that the city of Groningen and the surrounding area keep dry feet, the capacity of the water storage at the Leekstermeer must be increased. So the province of Drenthe has decided to increase capacity by another 5.2 million cubic meters.
The Noorderzijlvest Water Board has had three variants investigated and the so-called ‘Hooiweg variant’ appears to be the most suitable. Because nature also benefits most from this variant. It is also the cheapest variant. Moreover, all parties involved, such as provinces, municipalities, nature managers and the Noorderzijlvest Water Board, agree with that variant.
Natuurmonumenten was critical of other alternatives and is happy with this variant. “De Onlanden has been a great success story from the start. An incredible number of species have been landed here. That continues. We are proud of that. De Onlanden has truly become an international name as a nature reserve of quality. With this work we can we further increase and improve that capacity,” says forest ranger Bart Zwiers.
The water storage is intended for emergency situations. “We have calculated with a situation that only occurs once every 100 years. But in such a situation you need more storage capacity. To cope with such a situation you will have to be able to store more water,” says Marieke van Leeuwen, project leader of the Noorderzijlvest Water Board.
The maximum water level must be able to rise by 35 centimeters. To achieve this, a kind of wall is actually built around the nature reserve. “To be able to retain that extra water, we will have to raise the quays around the area and you will have to install a weir in the waterway to retain that water.”
Work is scheduled to begin in 2025. Before implementation, the effects on the environment must first be examined in more detail.
The Onlanden was designated as a water storage and nature reserve after the city of Groningen was confronted with major flooding in the late 1990s. Entire parts of the city were in danger of being flooded. “We never wanted that again,” Van Leeuwen concludes.