Abstract
Exploitation of hydropower potential in alpine areas undermines the ecological integrity of rivers. Damming and water abstraction substantially alter the physical habitat template of rivers, with strong repercussions on aquatic communities and their resources. Tools are needed to predict and manage the consequences of these alterations on the structure and functioning of macroinvertebrate communities and resource availability in alpine streams. We developed habitat preference models for taxa, functional feeding guilds, and organic resources to quantify the effects of discharge alteration on macroinvertebrate communities in two alpine streams. Our physical habitat model related an indirect measure of bottom hydraulic forces (FST hemispheres) to the distribution of macroinvertebrate taxa and their resources. We observed that flow-dependent habitat availability for macroinvertebrate communities generally decreased with increasing water abstraction. We were able to relate these changes to near-bed hydraulic conditions. Our results suggest, however, the existence of upper discharge thresholds delimiting optimal habitat conditions for taxa. In contrast, we found weak effects of near-bed hydraulic conditions on resource distribution. Overall, our findings contribute towards predicting the impacts of water abstraction on macroinvertebrate communities in small alpine streams and the benefits of baseflow restoration.
Highlights
The hydropower potential of alpine streams is widely exploited for electricity generation
The Lesgiüna catchment covers an area of 36 km2, of which 66% are above the water intakes
The dominant sediment grain size class was constant within sites except that it was higher in late spring at the Lesgiüna
Summary
The hydropower potential of alpine streams is widely exploited for electricity generation. This involves the construction of dams for high-head storage and the development of a network of conduits for water abstraction, trans-catchment transfer and water return to downstream rivers after turbination. The strategic role of hydropower will be consolidated, new hydropower infrastructure will be created, and concessions for hydropower operators will be re-negotiated [6]. These developments concern large and conspicuous hydropower schemes, and, increasingly, those on small streams [7]
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