Finding a balance between water storage and nature in De Onlanden

It is still very dry now, but the showers will come one day. The Onlanden ensures that Groningen keeps its feet dry, the area acts as a water storage facility when there is a lot of rainfall. As heavier rains are expected, it is planned to store additional water in De Onlanden.

Climate change is causing an extremely dry summer, but extremely wet periods are also expected. Since 2012, De Onlanden, on the border of Groningen and Drenthe, collects water in case of heavy rains. Six months ago, De Onlanden was still completely full of water. “It was quite an extreme situation,” says Marieke van Leeuwen of the Noorderzijlvest water board. “In February, a lot of rain fell successively in a short time. De Onlanden did what he had to do; the water that flowed from the Drents plateau to the bottom of Groningen is collected. But, based on the models climatic conditions of the KNMI, a moment passes. comes that De Onlanden no longer satisfies.”

Together with the three northern provinces and other water authorities, the Noorderzijlvest water authority therefore wants to create additional space for 5.2 million cubic meters of water, with the collection capacity now at 7.5 million cubic meters. This must be done within the current boundaries of De Onlanden, by raising the quays and placing dams, which will be raised if necessary.

The procedure for creating additional water storage began in March this year. In the spring, documents were available for inspection and responses could be submitted, and information evenings for stakeholders were also organized. Answers are now formulated to the answers. The additional space for water is to be ready in 2025, but exactly how this will be done is not yet determined. And a lot depends on it: in recent years, the region has turned into a nature reserve of more than 2,500 hectares, which benefits many aquatic animals. Otter also found De Onlanden and sea eagles and bitterns were observed.

Van Leeuwen: “We have to take action, the longer you wait, the more chances there are that Groningen will get your feet wet one day. De Onlanden is for the short term. For the long term, we keep talking and looking: what else can we still do is there any other places we can store water is under consideration but not going fast.

The water peak will be absorbed with the expansion of De Onlanden. But Natuurmonumenten mainly insists on collecting the water before it flows into De Onlanden. “By raising weirs and quays, you solve the problem of peak load. It is necessary, but in the event of extreme drought like the one we are experiencing again this year, it is useless,” says Fred Prak of Natural monuments. “A sustainable and climate-resistant option is to retain water longer in all waterways. So that the natural sponge effect, as it was before, occurs again. The water storage capacity then increases for peak times, but until then by holding it longer you also have a lot more water available throughout the catchment during a dry spell. the water board is preparing such plans, but given the extreme drought of recent years, we would prefer to see the result sooner than ‘after 2025’.”

Once the extra space has been created, the intention is to work with compartments, where the vulnerable nature will only store the extra water at the last possible moment. There are vulnerable species that cannot stay underwater (too long). Van Leeuwen: “De Onlanden simply has a double function. On the one hand, the ecological value that we must carefully manage. On the other hand, the “flood safety task” for extreme situations. We have to find a balance in this.”

Work in the area will begin once the environmental impact assessment procedures and project decision are completed, likely next year.