Ålanda Dam, Sweden

Two large lakes with genetic unique fish stock in southwest Sweden will be reconnected by removing a small dam between them, a dam that blocks the migration of biodiversity.


In southwest Sweden, Lake Anten and Lake Mjörn are two large lakes with a genetically unique trout population. The dam building at the end of the 18th century caused a stop in the exchange of genetic material between the lakes and their tributaries. This has caused the lake system to suffer from an in-breeding situation, severely decreasing the trout population. Also, several other species can not migrate over the Ålanda Dam, leading to a decrease in the freshwater pearl mussel hosted in Valån, one of the major tributaries.

At a glance

Project typeDemolition
Project statusLive
Demolition dateSummer 2024
Km to be openedTwo km, and two very large lakes with more than 20 tributaries
Focal speciesBrown trout of a genetically specific type
Project websitewww.sportfiskarna.se

Project context and opportunity

This is an opportunity to reconnect two large lakes that have been separated from each other for about a century. This is a very important part of the restoration work in the area, showing that Open Rivers plays a vital part in an ongoing restoration ambition. This will allow the genetically unique brown trout to host a strong population, gaining the whole ecosystem of the two rivers and their tributaries. It will also gain the red-listed and threatened freshwater pearl mussel that lives in one of the tributaries.

Project aims

A blocking dam between two large lakes in southwest Sweden will be removed. This will open up two km of river upstream and reconnect the lakes, benefitting species such as brown trout, eel, freshwater pearl mussel and salmon. The project will take important steps forward in restoring the lake system with its tributaries. It is an essential goal to demolish the Ålanda dam and to make it possible for fish, mammals and invertebrates to migrate up and down. It will also create an 800-meter-long stream habitat that was lost when the dam was built. The restoration can be further developed with future planned work upstream in the tributaries, and the trout population will be once again vital.