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Abstract

Water levels in hydropower-managed lakes and reservoirs frequently fluctuate in response to demands for electricity. These sudden and occasionally extreme variations tend to severely degrade littoral zones, the shallow nearshore areas that provide vital habitats for many aquatic organisms. When these habitats are altered or disappear, many species struggle to survive, leading to a decline in biodiversity. As awareness of these ecological impacts increase, so too does interest in finding practical, targeted measures to improve conditions for the species that depend on these environments.

Among the measures being explored is the use of Lake-in-Reservoirs (LiRs), which aim to buffer the effects of water level regulation on littoral habitats. LiRs are small and sheltered areas within reservoirs that are intended to uphold more stable hydrological conditions, even as the surrounding water body experiences fluctuations. By recreating the relatively stable conditions of natural littoral zones in lakes, LiRs may provide a refuge for species that are sensitive to hydrological disturbances.

This essay examines the feasibility and potential of using LiRs to enhance biodiversity in regulated aquatic systems. A systematic literature review was conducted to identify documented LiR implementations, resulting in seven confirmed cases, all located in Sweden and Norway. This essay draws from these cases, as well as a broader range of scientific studies, industry reports, and technical documentation. It focuses on how LiRs function under different environmental and regulatory conditions, as well as the factors that affect their effectiveness.

The findings suggest that LiRs can help preserve key ecological functions and partially offset the biodiversity loss. However, losses associated with hydropower operations and site-specific conditions, such as reservoir morphology, substrate composition, and local climate, appear to affect both the practical implementation of LiRs and the ecological outcomes they can achieve.

In sum, LiRs appear to be a promising yet insufficiently explored method for supporting local biodiversity and lake productivity in regulated lakes and reservoirs. While they may not be suitable for every given setting, strategic planning and adaptation to specific local conditions can increase their effectiveness as a conservation measure. Nevertheless, more research is needed to identify where LiRs are most effective and how they can best support long-term ecosystem health and resilience.

Keywords

regulated lakes; hydropower reservoirs; mitigation measures; lake-in-reservoir

Published in

Aqua introductory research essay
2025, number: 2025:1
Publisher: Department of Aquatic Resources, Swedish University of Agricultural Sciences

SLU Authors

UKÄ Subject classification

Environmental Management
Ecology

Publication identifier

  • DOI: https://doi.org/10.54612/a.4i0gptefj0
  • eISBN: 978-91-8124-137-2

Permanent link to this page (URI)

https://res.slu.se/id/publ/144014