Bruno, M.C.

Carolli, M.

Maiolini, B.

Siviglia, A.

Maiolini, Bruno

Carolli, Mauro

Bruno, Maria Cristina

Archivio istituzionale della ricerca - Fondazione Edmund Mach

Geophysical Research AbstractsVol. 12, EGU2010-2355-1, 2010EGU General Assembly 2010© Author(s) 2010The ecological effects of thermopeaking in Alpine streams in flumesimulationsBruno Maiolini (1), Mauro Carolli (1), M. Cristina Bruno (1), and Annunziato Siviglia (2)(1) Fondazione Edmund Mach, Environment and Natural Resources Area, S. Michele all’Adige (Tn), Italy(bruno.maiolini@iasma.it), (2) Department of Civil and Environmental Engineering, University of TrentoIn Alpine areas, the temporal patterns of hydropower plants operations can have consequences for the waterbodies which receive downstream releases in the form of "hydropeaking", typically consisting in sharp releasesof turbinated water in the river reaches below dams. Hydropeaking may significantly affect also the thermalregime of rivers: typically power plants fed by hypolimnetic releases from large dams cause a reduction insummer temperature and an increase in winter temperatures for long distances downstream. Very few studies haveaddressed the effects of the short-term temperature fluctuations related to hydropeaking (i.e., thermopeaking) onaquatic fauna, although they can be a major cause of riverine habitat degradation posing serious threats to aquaticcommunities.In the Adige River watershed, warm thermopeaking occurs from September to January and results in additional(up to 4°C) heating to the natural dial fluctuations; cold thermopeaking occurs from March to July and cools downthe temperature (up to 6°C), in contrast with the natural trend that would result in heating during the day.The biological effects of thermopeaking are difficult to study in nature, because they are associated with hy-dropeaking, which is known to cause a high catastrophic drift due to the increased intensity of bed scour. However,controlled simulations of thermopeaking events could be performed in artificial flumes. We used artificial flumeswhich had proved to perform discharge manipulations which simulate hydropeaking events, and conducted foursimulations, two warm thermopeakings in early and late winter, and two cold-thermopeakings, in early and latesummer, respectively. The impact of thermopeaking on benthic macroinvertebrates was assessed by collectingthose organisms which are displaced from the substrate and drift in the water column. Displacement can be active(i.e., part of the behavioural repertoire of certain insect species), or passive (i.e., catastrophic and generated byany disturbance). Drifting invertebrates were collected at time intervals before the simulation, and at continuous,short-time intervals during the simulation in order to follow the changes in drift over a short time period duringthe simulation.We assessed the effects of thermopreaking on the benthos community by answering to the following questions:1) Do thermal alterations induce an increase in drift of benthic invertebrates?3) Do a reduction or an increase in water temperature have different effects of invertebrate drift?Benthic invertebrates responded more to the cold thermopeaking simulations, with differences among taxa withdifferent life strategies and ecological requirements.

The ecological effects of thermopeaking in Alpine streams in flume simulations

https://openpub.fmach.it/bitstream/10449/21724/1/EGU2010-2355-1%20maiolini.pdf

The ecological effects of thermopeaking in Alpine streams in flume simulations

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Archivio istituzionale della ricerca - Fondazione Edmund Mach