Wallin’s Oasis – an artificial wetland
A wetland acts as a sponge that stops the flow of water and acts as a filter for nutrients. Constructed wetlands work particularly well in the agricultural landscape in order to reduce leaching from agricultural land before the nutrients reaches the sea. In addition to reduced eutrophication, bird life and biodiversity is favored, since valuable new habitats for aquatic plants, birds, amphibians and aquatic invertebrates are created in the area.
The main purification processes in a wetland is denitrification (bacteria convert nitrate to nitrogen gas) and sedimentation (mainly phosphorus). The plants also bind in their biomass nitrogen and phosphorus. The effect of wetlands varies, but under favorable conditions, a well-constructed wetlands take up between 500 and 1 500 kg of nitrogen per hectare per year and about 100 kg of phosphorus. The theoretical nutrient reduction from Wallin’s oasis, which is 0.5 ha is thus about 500 kg nitrogen and 50 kg of phosphorus per year. The local government of Åland takes water samples from the ditch, which permits evaluation of the efficiency of the wetland.
In addition to the direct environmental impact, the purpose of the wetlands is to provide an opportunity for the general public, particularly children and young people, to get acquainted with a wetland and get information about why wetlands are important and how they work. Three info signs next to the wetland tells the visitors about why this wetland is constructed, who Wallin was, of plant and animal life in the wetlands and how a wetland works. The place is well suited for demonstration purpose, then it is easy to stop there by car or bus and to build lookouts over the wetland.
The project plan is made by Peter Feuerbach from the The Rural Economy and Agricultural Society of Halland. The wetland was completed in summer 2014. Wallin’s Oasis is a joint project between the PAF and Ålandsbanken, the Baltic Sea Fund and the Government of Åland where PAF and the Bank of Åland stands as financiers, the Baltic Sea Fund as project coordinator and the government as landowners and after construction also as the owner of the wetland.