Moving waters to mitigate hydropeaking: A case study from the Italian Alps

We assessed the effect of a hydropeaking diversion mitigation measure that allows for additional hydropower production, which markedly reduced on 10-km stream reach in north-eastern Italian Alps. Hydropeaking, caused by storage plant, affected study from 1920s to 2015, when cascade three small run-of-the-river plants was installed divert hydropeaks plant outlet directly into intake RoRs plants, and released downstream confluence with major free-flowing tributary. The flow regime mitigated shifted hydropeaking-dominated baseflow-dominated winter, variability represented only snowmelt rainfall late spring summer. application two recently proposed sets indicators, hydraulic analysis wave, together assessment biotic changes, allowed quantifying changes ecohydraulic processes associated mitigation. changed residual type, much less frequent hydropeaks; although an average two-fold increase downramping rates were recorded junction tributary, these did not represent ecological concern. functional composition macrobenthic communities slightly response mitigation, but taxonomic recover conditions typical more natural regimes. This likely due dilution pollutants resulting slight worsening water quality. Conversely, hyporheic showed diversity abundance interstitial taxa, especially sites most hydropeaking. space availability, brought reduction fine sediments clogging. Besides illustrating feasible option Alpine streams, our work suggests importance monitoring both benthic communities, sediment supply regimes, physico-chemical quality parameters.