Abstract
Study region
Eight rivers in Slovenia and Croatia that are tributaries of the Danube River or the Adriatic Sea
Study focus
The different types of hydropower plants alter river hydrology at several temporal scales and to a varying degree, respectively, but impacts have hardly been quantified in an integrative way structured by hydropower plant type. Hence, we analysed hydrological data from rivers affected by 13 HPPs belonging to 3 operational types, namely run-of-river (RoR), storage (ST), and diversion storage (DST). Daily discharge data in pre- and post-impact periods were compared by applying the Ecodifference and Indicators of Hydrologic Alteration methods. In addition, sub-daily discharge data were analysed for potential alterations induced by hydropeaking.
New hydrological insights for the region
Studied HPP types caused mostly strong but varying alterations of flow regime. To facilitate comparisons, the three existing impact indicators were integrated into a composite Holistic Score of River Hydrology Impact. Holistic Score of River Hydrology Impact showed that DST HPPs caused most severe impacts in residual river reaches, followed by ST HPPs, while RoR HPPs had less severe impact. Environmental flows were not provided to five of six residual river reaches. We detected hydropeaking in 9 HPPs, but probably underestimated their impacts, as sub-daily discharge was only available for 58% of the gauging stations in the study area.
Eight rivers in Slovenia and Croatia that are tributaries of the Danube River or the Adriatic Sea
Study focus
The different types of hydropower plants alter river hydrology at several temporal scales and to a varying degree, respectively, but impacts have hardly been quantified in an integrative way structured by hydropower plant type. Hence, we analysed hydrological data from rivers affected by 13 HPPs belonging to 3 operational types, namely run-of-river (RoR), storage (ST), and diversion storage (DST). Daily discharge data in pre- and post-impact periods were compared by applying the Ecodifference and Indicators of Hydrologic Alteration methods. In addition, sub-daily discharge data were analysed for potential alterations induced by hydropeaking.
New hydrological insights for the region
Studied HPP types caused mostly strong but varying alterations of flow regime. To facilitate comparisons, the three existing impact indicators were integrated into a composite Holistic Score of River Hydrology Impact. Holistic Score of River Hydrology Impact showed that DST HPPs caused most severe impacts in residual river reaches, followed by ST HPPs, while RoR HPPs had less severe impact. Environmental flows were not provided to five of six residual river reaches. We detected hydropeaking in 9 HPPs, but probably underestimated their impacts, as sub-daily discharge was only available for 58% of the gauging stations in the study area.