Effects of repeated hydropeaking waves on benthic invertebrates: a flume study

In late summer 2013, we conducted a set of controlled simulations in five steel flumes directly fed by an Alpine stream (Fersina stream, left tributary to the Adige River, Trentino, Italy), where benthic invertebrates can freely colonize the flumes by downstream drift and egg deposition. We simulated a repetition of 5 daily hydropeaking events, lasting approximately 6 hours, of different intensities. We collected benthic samples before and after the set of simulations to determine changes in the benthic communities due to the depletive effect of repeated hydropeaking inducing the massive drift of invertebrates. During each simulation, we collected drifting organisms at short time intervals. We observed: 1) a strong increase in drift during the initial discharge increase; 2) drift responses proportional to the absolute discharge increase; 3) a decrease in the drift responses over successive days; 4) a decrease in benthic abundances at the end of the simulations