Among the issues that are most relevant in the study of climate change (CC), hydropower plays a double role. On one hand, it will be affected by the change in water availability for hydropower plants. On the other hand, as the present major source of renewable energy, it is useful to support and increase the energy production and to reduce the human induced CC. The aim of the activity presented in this paper is the impact evaluation of expected CC on future reservoir control, the assessment of variations in hydropower production, and the identification of possible changes in water management. This activity is part of ACQWA project whose aim is the use of advanced modeling techniques to quantify the influence of CC on the major determinants of river discharge and to analyze their impact on society and economy. The activity has been focused on the development of a model of the management of a complex hydropower system as a function of climate conditions and electricity prices. The methodology was applied to a case study, the hydropower system in Valle d'Aosta Region in Italy. A conceptual scheme of the network of plants and reservoirs was developed and its optimal management was computed by means of a simple optimization tool, using energy prices and inflows as the main drivers of the system. The expected variations in reservoir management and power production were quantified through a comparison between optimization results of present and future years. Results show a statistically significant decrease in overall hydropower production; they give indications of variations in monthly production and interannual variability, causing an increase in water deficits and, as a consequence, in possible water conflicts among water uses. These results point out the limits of the current water policy and call for the introduction of a true integrated and adaptive approach.