Hydropower effects at different temporal scales in an Alpine river

Abstract

In the last decade a strong scientific base has recognized that the pattems of temporal variation in river flows are the driving forces in structuring the function of riverine ecosystems (the "natural flow-regime paradigm"; PoFF et al. 1997). We analyzed the changes in flow regime of the river Adige, the second longest Italian river, which is strongly affected by the operation of 30 hydropower-producing reservoirs in its watershed. We used different temporal scales: (l) mean daily discharge data, recorded from 1923 to 2006, were used to evaluate alterations in the components o f the natural flow regime due to hydropower plants construction and operation; (2) the same data were analysed on a shorter timeframe (19972006) to identify the effects of changes in seasonal electricity demand and hydroelectric power plant management; and (3) the spatial and temporal effects of a single hydropeaking wave on benthic communities were assessed at sites in the first 8 km downstream o f a hydropower plant. We assessed the extent of catastrophic drift of invertebrates (CULP et al. 1985; i.e., generated by any disturbance) induced by a sharp rise in discharge and the ability of the different taxa to avoid the washout effect.