Patch-scale habitat dynamics: three metrics to assess ecological impacts of frequent hydropeaking

Human activities significantly alter natural river flows, impacting ecosystem functioning and
biodiversity worldwide. Hydropeaking, resulting from intermittent on-demand hydropower
generation, introduces sub-daily flow fluctuations exceeding natural variability. While the
effects of single hydropeaking events are well-studied, the cumulative impacts of frequent
hydropeaking requires further exploration. This study aims to develop metrics that captures
changes in habitat dynamics at the patch scale (i.e. individual micro-habitats within the habi-
tat mosaic) due to reoccurring hydropeaking. Using hydrodynamic simulations, we introduce
three patch-scale metrics to quantify habitat dynamics with high spatial (0.5 m) and temporal
(10 min) resolution: (M1) Habitat probability within patches, assessing spatio-temporal diver-
sity of habitats; (M2) Habitat shifts within patches, evaluating habitat persistence for sessile
organisms (e.g. vegetation, invertebrates); and (M3) Spatial shifts of habitats, indicating habi-
tat relocation affecting mobile species (e.g. adult fish). Using eight hydro-morphological
scenarios representing different levels of anthropogenic modification of flow and morph-
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ology, we demonstrate that these metrics effectively quantify changes in habitat dynamics
at patch-scale. The results highlight the ecological relevance of these metrics and their
potentially utility for river management. By identifying areas susceptible to ecological
impacts, these metrics may serve as tools for hydropeaking mitigation, enabling more tar-
geted and spatially explicit habitat management and restoration.