Climate Change-Induced Alterations in River Flow and Their Consequences for Ecosystems in Boreal Rivers

Variations in precipitation patterns during the seasons are expected as a result of climate change, which will affect the hydrological regimes of boreal rivers. Such changes can influence ecological conditions, e.g., by altering suitable habitat areas and the functioning of riparian zones. This study investigates the effects of seasonal flow variations in two regulated boreal rivers on suitable habitat availability for European grayling and on the extent of riparian zones, using hydraulic modelling of both river systems. Grayling habitat suitability was assessed based on previously defined preferences for water depth and flow velocity. Riparian zones were analysed by modelling the inundation period for different discharge scenarios. The simulations were based on representative seasonal discharge scenarios, neglecting daily flow characteristics and sub-daily flow patterns. The results indicate that the ecosystems in both study cases are affected by the projected impacts of climate change. With the increasing annual flow, the grayling habitat areas can be enlarged in Luleälven, while a higher winter discharge and reduced spring flood have a narrowing impact on the riparian zone.