Silenced Rapids and Waterfalls: Habitat Loss and Management of Bypassed Reaches in the Regulated Rivers of Sweden

Abstract

Habitat destruction is a global driver of biodiversity loss. In rivers, damming and river regulation for hydropower have caused extensive loss of high gradient, riffle, rapid and waterfall habitats. Restoring these habitats, which support unique biodiversity, should be an urgent priority, but inadequate documentation hampers evaluation of different management strategies. Focusing on Sweden, where river regulation affects most catchments, we mapped and quantified characteristics (e.g., slope, length, discharge) of 968 bypassed reaches (BRs), that is, river sections that are dewatered due to diversion of discharge for hydropower production. The extent of habitat loss associated with BRs is substantial, summing to a total length of 1,256 km, 94% of which is predominantly comprised of former riffles, rapids and waterfalls. BRs are typically located in larger rivers at central river network positions, highlighting their potential importance for hydrological and ecological connectivity. These habitat losses are poorly addressed by current management: three quarters of Swedish BRs have no mandated minimum discharge. Of the remainder, 88% have a discharge

Keywords

habitat degradation; minimum discharge; hydropower; rheophilic fish; water diversion; environmental flows

Published in

Water Resources Research
2026, volume: 62, number: 2, article number: e2025WR040752
Publisher: AMER GEOPHYSICAL UNION

SLU Authors

• Segersten, Joel

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    

• Degerman, Erik

  • Department of Aquatic Resources (SLU Aqua), Swedish University of Agricultural Sciences
    

• Donadi, Serena

  • Department of Aquatic Resources (SLU Aqua), Swedish University of Agricultural Sciences
    

• Widén, Åsa

  • Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences
    

• Mckie, Brendan

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Environmental Sciences
Oceanography, Hydrology, Water Resources

Publication identifier

• DOI: https://doi.org/10.1029/2025WR040752

Permanent link to this page (URI)

https://res.slu.se/id/publ/146395