These nature managers ask water boards to turn on the tap | climate

All kinds of special marsh birds breed in the Zouweboezem nature reserve, but the water board keeps the water level too low and that causes problems. The water board also has a role to play in Junner Koeland in Overijssel. NU.nl visited the areas in the run-up to the elections.

While flakes of wet snow flutter down, Maarten Breedveld of the Zuid-Hollands Landschap walks into the Zouweboezem. Boots are not a superfluous luxury, because the area south of the Lek between Lexmond and Meerkerk is swampy.

Yet that is a distorted picture, because the protected marsh area (Natura 2000 area) is actually too dry. The water should be higher.

“Look, you can no longer call this kind of reed land,” says Breedveld, pointing into the area. “There are still some pieces of reed, but it has become very grassy. That is because the area is no longer flooded.”

Due to the low water level, the reed beds of the Zouwboezem are becoming increasingly grassed. Photo: Job van der Plicht

Marsh birds leave the Zouweboezem

The Zouweboezem used to flood, but since the water boards have been able to control the water level more precisely and faster, it hardly ever floods, says Breedveld. “The dynamics in the water level are gone. There are also so many interests involved. Housing, agriculture, nature.”

What also does not help is that the water system that the Rivierenland water board must manage is tens of kilometers in size. “Then you see that tailor-made solutions are not possible in such a Natura 2000 area,” explains Breedveld.

The result is that typical marsh birds are having an increasingly difficult time in the Zouweboezem. The mustache or the great reed warbler, for example. The bittern chooses to breed a little further along the river Lek. “In an area the size of a large living room, while there were hundreds of acres of reed marsh here.”

Nearly two hundred purple herons breed in the Zouweboezem. Nowadays they are forced to do so in trees. Photo: Getty Images

Purple herons forced into the tree

The crake has also disappeared from the area and the dozens of purple herons – for which the Zouweboezem is known – are also having a hard time.

“With almost two hundred breeding pairs, we have one of the largest purple heron colonies in Northwest Europe here,” says Breedveld. The purple herons always nested on the ground among the reeds. “But due to the low water level, the swamp area has become extremely accessible to predators such as the fox, which now rambles through here.”

The purple herons fled into the tree and nested there. But there is also a danger: the pine marten has already reported in the Zouweboezem and is undoubtedly eager to snack in the herons’ nests.

So the water level has to rise. “It is usually 80 to 85 centimeters above NAP here,” says Breedveld. “But without having an impact on local residents, the level can go to 1 meter. That is just the difference between dryness and wetness.”

Zuid-Hollands Landschap, which manages the Zouweboezem, has been discussing this for some time with the Rivierenland water board. But the water level hasn’t changed so far. Breedveld advocates quick action. “I would consider it a gamble if we sailed this course for another ten years. And the question is whether it is wise to gamble with a Natura 2000 area.”

Ancient cowlands along the Overijsselse Vecht

140 kilometers away is the Junner Koeland, a nature reserve along the Overijsselse Vecht. Together with the Arrier Koeland on the other bank, it is one of the last remnants of stream valley grasslands. They are bursting with unique biodiversity: flowers, bees, butterflies, birds – even the trees and shrubs are special.

Typical floral wealth of the Junner Koeland. Photo: NU.nl

This is related to the Vecht and the cultural history. Until the advent of fertilizer, the sandy soils of the eastern Netherlands consisted largely of heaths. They were extensively grazed by sheep herds. And thanks to the sheep manure, small high fields were possible around the villages: ash trees. They supplied rye, among other things.

But the esdorpen along the Vecht had a third source of food: cow’s milk. The village had a total of about thirty cows, which were grazed together. The animals could graze there because of the unique subsoil. And they created the unique landscape at the same time.

The Junner Koeland is not only a unique nature reserve, but also provides a glimpse of a piece of cultivated land where almost nothing has changed since the Middle Ages. The current owner, Staatsbosbeheer, also continues grazing with cows. Small herds that roam freely – a balancing act against grassification caused by nitrogen pollution.

The result can be seen in the summer: the soil is then covered with a carpet of flowering herbs. Purple thyme, pink Fighting carnations, yellow bedstraw and the blue of harebells, dog violets, long speedwell and blue button. Very rare flowers also grow there, such as the mint pennyroyal and, very locally, the mountain orchid. That is an orchid that otherwise only occurs in South Limburg.

The Junner Koeland is supposed to flood in winter, with calcareous water from the Vecht. This is happening less and less due to canalization and incision of the river, so that the area is acidifying. Photo: Nico Arkes, Staatsbosbeheer

Stream valley grasslands should be flooded

In the winter you can’t see any of that floral splendor. The area that is bone dry and full of flowers every summer is bright green. Or all blue. Because the stream valley grasslands should be flooded in winter. At least in the past.

“I’m proud of how we manage it,” says Bert Haamberg, forester ecology of the Junner and Arrier Koeland. “But there’s one thing I can’t do myself: I can’t turn the faucet.”

The Overijsselse Vecht was channeled a century ago. The current has become much shorter and water is drained much faster. Only a few stamps remain of the original stream valley grasslands that existed on a large scale from the German border to Zwolle.

Calcium-rich water needed in the fight against acidification

The latter areas are also in danger of slowly shrinking. This is because the winter floods occur less often, flood an increasingly smaller area – and last shorter: a few days, instead of weeks.

This area is also affected by acidification. This is a direct result of nitrogen pollution. It would be nice if the nitrogen supply decreased, but to preserve the area for the future, the return of the water is even more essential, says Haamberg.

“Periodic flooding with the calcareous water of the Vecht reduces the effects of this acidification on the soil and the plants. It would be nice for the future if the area flooded more often and the water could then remain there for longer.”

But how? Water authorities are under increasing pressure because of a dual mission that seems contradictory. They must prevent flooding. And at the same time remedy summer droughts. This can be done by retaining more water in winter. But then we will sometimes have to accept wet feet locally in winter, say hydrologists.

In order to restore the stream valley grasslands along the Vecht, canalisation should ideally be reversed. The river would then have to meander through the landscape and, above all, become less deep: from a water highway back to a rippling river.

Bert Haamberg of Staatsbosbeheer, at an old Vecht channel in the Junner Koeland. The shrubs in the area are also special. Lots of wild roses and blackthorns. The endangered blackthorn page occurs and gray shrikes breed there. Photo: Rolf Schuttenhelm, NU.nl

Planned new weir can be salvation

The rescue of the Junner Koeland in particular can also be made of concrete: a weir. After the channeling of the Vecht, weirs were necessary to prevent the river from completely emptying in the summer. The nearest weir, near the hamlet of Junne, is exactly the wrong way for the Junner and Arrier Koeland: upstream. This means that the Vecht cuts deeper just behind the weir and the nature areas are flooded less often.

That weir, owned by the water board, is old and has been rejected due to damage. A new weir must be built. And there are calls for that new weir to be built a few kilometers downstream. For the Junner and Arrier Koeland it would be a rescue. But as always with water, there are more interests involved, and they all have to be able to sit around the same tables.

Haamberg does not want to disrupt that process and therefore stick to the essence: “I don’t care how it happens. But if we want to preserve this unique stream valley grassland for the future, more water has to be added in the winter.”

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