Macroinvertebrate Habitat Dynamics under Frequent Hydropower-Induced Discharge Fluctuations: Patch-Scale Metrics to Quantify Effects of Hydropeaking and Morphological Complexity

Abstract Hydropeaking, driven by intermittent hydropower production, induces frequent and rapid sub-daily discharge fluctuations that alter riverine habitats and cause biodiversity loss worldwide. Benthic macroinvertebrates are particularly vulnerable due to their limited mobility, complex life cycles, and sensitivity to rapid hydraulic change. Yet, tools to quantify hydropeaking impacts on macroinvertebrate habitats at ecologically relevant spatio-temporal scales remain limited. Here, we present and evaluate a patch-scale approach to quantify macroinvertebrate habitat dynamics under hydropeaking. Using high-resolution hydrodynamic modelling (0.5 m spatial, 10 min temporal resolution) in a 1 km alpine river reach, we generated a habitat time-series and derived four complementary metrics: habitat probability, habitat shifts, drift risk, and desiccation risk. We analyzed metric interactions, applied multimetric clustering to identify recurring habitat–risk regimes, and related these to local morphology-driven structural complexity. Results show that hydropeaking increases habitat dynamics, with frequent habitat shifts occurring even in patches with highest habitat probabilities. Structurally complex areas generally support higher habitat probability and lower drift risk, but may remain exposed to desiccation, revealing trade-offs among key hydraulic stress mechanisms. These patterns demonstrate that the metrics capture ecologically relevant habitat responses, while confirming that structural complexity alone cannot eliminate the stress induced by frequent hydropeaking. Overall, the proposed metrics provide an ecologically meaningful framework to study macroinvertebrate habitat dynamics under hydropeaking. By explicitly linking hydraulic stress mechanisms, habitat dynamics, and morphological context, the framework supports process-based river management in regulated rivers.