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We present an assessment of the potential impacts of climate change on hydropower production within a paradigmatic, very highly exploited cryospheric area of upper Valtellina valley in the Italian Alps. Based on dependable and unique hydrological measures from our high-altitude hydrometric network Idrostelvio during 2006-2015, we set up the Poly-Hydro model to mimic the cryospheric processes driving hydrological flow formation in this high-altitude area. We then set up an optimization tool, which we call Poly-Power, to maximize the revenue of the plant manager under given hydrological regimes, namely, by proper operation of the hydroelectric production scheme (reservoirs, pipelines, and power plants) of the area. We then pursue hydrological projections until 2100, feeding Poly-Hydro with the downscaled outputs of three general circulation models from the Intergovernmental Panel on Climate Change Fifth Assessment Report, under the scenarios Representative Concentration Pathway (RCP) 2.6, RCP 4.5, and RCP 8.5. We assess hydrological flows in two reference decades, that is, at half century (2040-2049), and end of century (2090-2099). We then feed the so obtained hydrological scenarios as inputs to Poly-Power, and we project future production of hydroelectric power, with and without reoperation of the system. The average annual stream flows for hydropower production decreases along the century under our scenarios (-21 to +7%, on average - 5% at half century; -17 to -2%, average - 8%, end of century), with ice cover melting unable to offset such decrease. Reduction in snowfall and increase in liquid rainfall are the main factors affecting the modified hydrological regime. Energy production (and revenues) at half century may increase under our scenarios (-9 to +15%, +3% on average). At the end of century in spite of a projected increase on average (-7 to +6%, +1% on average), under the warmest scenario RCP 8.5 decrease of energy production is consistently projected (-4% on average). Our results provide an array of potential scenarios of modified hydropower production under future climate change and may be used for brain storming of adaptation strategies.