River Alsterån

River Alsterån is a 125 km long river in south-eastern Sweden with a catchment area of 1 525 km². It is one of Kalmar County’s most valuable watercourses and is a Natura 2000 site in its entirety within the county.

From its source, Lake Alstern, River Alsterån flows through varied terrain in two branches before reaching Lake Allgunnen, one of Sweden’s largest unregulated lakes. From Allgunnen, the water flows on through three outlets that join further downstream before the river flows into the Baltic Sea at Pataholm in Kalmarsund. The upper part of River Alsterån is dominated by coniferous forest and marshland, while the lower parts are characterized by farmland and deciduous forest. River Alsterån also passes wetlands and swamp forests on its journey.

Biological values and threatened species
River Alsterån has high natural values thanks to its varied habitats. It is an important spawning ground for salmon and trout, but other species such as eel, sea lamprey, catfish, lamprey and stone loach are also present. In total, around 18 fish species have been reported in the system. However, salmon populations are in decline, making them a priority species in Natura 2000 management.

The river has a rich benthic fauna with rare and endangered species as well as significant terrestrial flora and fauna. Birds living in the vicinity of aquatic habitats include ospreys, sandwich terns, white-tailed eagles and kingfishers. Another priority species under the EU Habitats Directive is the otter, which has declined sharply since the 1950s but is now recovering.

The Alsterån estuary and coastal lagoons in Kalmarsund are also part of the Natura 2000 site. These brackish water environments have a rich flora and support species such as the predatory fish sea trout, pike and perch. However, the coastal ecosystems of Kalmarsund and the Alsterån estuary are also severely affected by eutrophication and reduced recruitment of, for example, the predatory fish pike and perch.

The river has a rich benthic fauna with rare and endangered species as well as significant terrestrial flora and fauna.

Environmental impacts and restoration needs
For a long time, River Alsterån was used for timber rafting, which led to the clearing of boulders and changes in the bottom substrate and hydrology. The river has also been dammed for mills and hydropower, and large wetlands have been drained, negatively affecting water flow.

During the 1970s, water quality deteriorated due to acidification. However, the situation has improved through reduced acidification and extensive liming efforts. Nevertheless, according to the EU Water Framework Directive, River Alsterån has only a moderate ecological status due to a lack of connectivity, altered morphology and recurrent summer water shortages, which negatively affect ecosystems.

Restoration actions
According to the Natura 2000 management plan, measures to ensure free migration routes, successful spawning and functioning hydrology are priorities. Within the Improve Aquatic LIFE project, the following actions are planned:

• Removal of a migration barrier, opening up 3,000 meters of river to fish and other organisms.
• Biotope restoration of approximately 1,300 meters to restore habitats for plants, animals and fish spawning.
• Restoration of approximately 23 hectares of wetland to improve the natural hydrology downstream.
• Measures in coastal lagoons to improve recruitment conditions for predatory fish.

The measures will improve connectivity, hydrology, water quality, biodiversity and fish production, and benefit Natura 2000 species such as salmon, stone loach and lamprey. They will also enhance the typical species of brook lamprey, ferret and minnow and help mitigate recurrent water scarcity.