Natuurmonumenten (Dutch Society for Nature Conservation) and Rijkswaterstaat (the executive agency of the Ministry of Infrastructure and Water Management) are restoring one of the largest freshwater lakes in western Europe by constructing islands, marshes and mud flats from the sediments that have accumulated in the lake in recent decades. These 'Marker Wadden' will form a unique ecosystem that will boost biodiversity in the Netherlands.
Lake Markermeer (700 km2) was split off from Lake IJsselmeer in 1976, when a dam was built between Enkhuizen and Lelystad. Disconnected from the sea and rivers, the lake became a stagnant system. The lake has barely any natural shores, and its waters are often extremely turbid as wind and waves churn up the accumulated sediments from the relatively shallow lake floor (2-4 m deep). As a result, fish and bird populations have declined dramatically. The construction of this archipelago, these new islands give nature a major boost with newly created habitats for water plants, shellfish, birds and fish. Islands with natural shores and spawning areas will be built with sand, clay and silt dredged from the lake. This way a robust, clear-watered nature area arises in the heart of the Netherlands: a natural jewel where migrating birds, fish and other animals will thrive.
Natuurmonumenten is the largest private organisation for nature conservation in the Netherlands. We manage over 100,000 hectares (1,000 km2) of land and water, from large nature reserves to small natural areas of high ecological value and beauty. Natuurmonumenten is run by and for people who care for nature. Contact
Questions or comments on this project you can email us at: [email protected]kerwadden.nl
Natuurmonumenten has initiated the Marker Wadden project. The construction of these islands is undertaken together with Rijkswaterstaat and Boskalis, a Dutch maritime construction company.
The sediments from the Markermeer are used to construct spawning areas, islands and natural shores such as wetlands and beaches. Bringing back these habitats will greatly benefit endangered plants and animals. By restoring the lake we will create a robust ecosystem in the heart of the Netherlands, which will play a key role in the national (and international) ecological network of habitats and species. Moreover, the lake will become much more attractive for water sports and nature lovers. The harbour island of Marker Wadden will be accessible to the public.
Marker Wadden is one of the biggest nature restoration projects in western Europe, aiming to restore an area of up to 100 square kilometres. The start of this project is made possible in part by the Dream Fund of the Dutch National Postcode Lottery.
Lake Markermeer (700 square kilometres) was split off from the Lake IJsselmeer in 1976, when the Houtrib dike between Enkhuizen and Lelystad was completed.
Both lakes used to be part of the Zuiderzee, a North Sea inlet dammed off in 1932. Today, the Markermeer has lost most of its natural shores to land reclamation and flood protection measures, and is cut off from the sea and rivers by dams and dikes. In many places a thick layer of silt has accumulated on the lake floor, where it suffocates bottom-dwelling organisms. Moreover, the water of the lake is often extremely turbid due to sediments being churned up by the waves. This reduces the amount of light reaching lower depths and inhibits the growth of algae and water plants. As a result, fish and bird populations have declined dramatically.
This project is about the construction of islands with natural shores, and trap the silt to decrease water turbidity. Suspended sediments will settle on the lee side of the islands. This will greatly improve habitat quality for endangered plants and animals. By restoring the Lake Markermeer we will create a robust ecosystem in the heart of the Netherlands, which will play a key role in the national (and international) ecological network. Moreover, the lake will become much more attractive for water sports and nature lovers.
During the last twenty years, the Markermeer ecosystem has deteriorated dramatically. Research has shown that multiple factors have contributed to this decline. The fact that the Lake no longer flushed by the sea and rivers has resulted in significant siltation of the lake. The thick layer of mud on the lake floor is suffocating bottom-dwelling organisms. Turbidity from suspended sediments has greatly reduced primary production by algae and water plants. Moreover, the lake has barely any natural shores or shallow littoral zones. As a result, many water plants, fish and mollusks such as the zebra mussel are struggling to survive.
The decrease in primary production and reduced invertebrate and fish populations in the Markermeer have led to a food shortage for many water birds. Since the 1980s, birds such as the common pochard, tufted duck and common goldeneye have declined by more than 75%!
One of the main problems of the Lake Markermeer is the thick layer of silt covering the lake floor. The silt problem in the Markermeer is partly due to the construction of the dam between Lelystad and Enkhuizen. This dam was completed in 1976. The plan at that time was to convert the lake into polder land. However, land reclamation kept being postponed, and in 2006 the Dutch government abandoned the plan altogether. By then the Markermeer had been cut off from the Lake IJsselmeer for more than thirty years. The separation of the two lakes had a major impact on the water quality and ecology of the Markermeer. Before the dam was built, fine sediments were flushed out from the Markermeer by currents transporting the silt to deeper parts of the IJsselmeer. This no longer being the case, a suffocating blanket of silt has now accumulated on the bottom of the Markermeer.
The Marker Wadden project will be implemented in a number of steps. The first phase will be carried out by Natuurmonumenten and Rijkswaterstaat (the executive agency of the Ministry of Infrastructure and Water Management) and involves construction of seven nature island (1300 hectares) including an 'underwater landscape' of spawning areas and shallow and deep channels. The costs of this first phase amount to 90 million euros.
The main funding for this project has been raised by Natuurmonumenten, the Dutch National Postcode Lottery, Ministry of Infrastructure and Water Management, Ministry of Agriculture, Nature and Food Quality, the provinces of Flevoland and North-Holland.
Following a comprehensive tendering process, Boskalis has been selected to carry out the Marker Wadden project. Preliminary work for building the first nature started in spring 2016. The first five islands are completed in 2021 end the sixth and seventh islands in 2023.
The first island of the Marker Wadden project will be constructed at about four kilometres from the dam between Enkhuizen and Lelystad. On and around the island a landscape will develop with reed marshes, mud flats and shallow littoral zones, where aquatic plants and invertebrates, fish and birds will thrive. The harbour island will also have a boat landing stage and a sandy beach.
The vast expanse of water, wide skies and broad horizons are important qualities of the Markermeer. Therefore the islands will be constructed far enough from the lake shores to not interrupt the view. From the dam between Enkhuizen and Lelystad the first island will be just visible in the distance. Visitors to the islands will enjoy the magnificent views from the island shores.
The construction of the nature islands in the Markermeer are an enormous technical challenge. Innovative techniques will be required to keep the costs as low as possible. The project offers an excellent opportunity to develop and showcase Dutch expertise on 'building with nature'.
'Building with nature' makes use of natural processes to develop sustainable engineering solutions that benefit both humans and nature. In the case of the Marker Wadden project, building with nature involves developing 'soft', natural flood defenses, and using natural sediment transport processes to reduce turbidity and build islands with lake sediments. Close to the location of the first island a deep channel will be dug, in which large amounts of sediment will accumulate due to natural flow patterns and gravity. The trapped sediment will be used to build the islands. Marker Wadden is one of the flagship projects of the Dutch water engineering sector. This project will help to promote the export of Dutch expertise on 'Building with nature', particularly in the areas of flood protection, water quality improvement and sediment management.
The ambition for Marker Wadden is to increase bird diversity in the Markermeer area. For the sake of nature, and for birdwatchers and other visitors to enjoy. The Marker Wadden project will greatly enhance opportunities for birdwatchers, nature lovers and other visitors. The harbour island will have a boat landing stage and a small settlement. For visitors a modest pavilion and four holiday houses and some buildings for research and management. Together a handful of small buildings able to generate their own energy and their own drinking water, as well as purifying their own wastewater. An off-grid settlement. The other islands are not accessible, they are tranquil places reserved for wildlife.
Many species of migratory birds overwinter on the Markermeer, spend their breeding or moulting season here, or use the lake as a resting place between their overwintering areas in Africa and breeding grounds in Scandinavia, northwest Russia and Siberia.
The Lake Markermeer is a Natura 2000 site and an important habitat for many bird species. In particular, the Markermeer serves as breeding grounds for common tern and cormorant, and as feeding and resting area for the barnacle goose, common goldeneye, little gull, great crested grebe, greylag goose, goosander, gadwall, red-crested pochard, tufted duck, common spoonbill, coot, smew, northern shoveller, widgeon, common pochard, scaup (bluebill) and black tern. Birds such as tundra swan, black-headed gull, Mediterranean gull, little grebe and common shelduck come to the Markermeer to moult, rest, and or overwinter. The Marker Wadden project will greatly increase food and habitat availability for these birds.
Although fish mass and diversity in the Markermeer have decreased strongly since the 1980s, the lake still harbours a broad range of fish species. Common fish species in the Markermeer include smelt, roach, rudd, perch, bream, carp, tench, pike, ruffe, three-spined stickleback and zander. Rarer species such as houting, burbot, sea trout, asp and catfish are occasionally found. For fish-eating birds, the presence of fish, particularly smelt, is essential. The Marker Wadden project should help to restore water quality and primary productivity, and hence increase fish populations.