Hydropower is a very important component of the Swiss energy mix, but its future is jeopardized by several factors. To clarify the long-term scenarios, an assessment of the risks and opportunities is necessary. This thesis analyses these complex dynamics, and focuses more particularly on the problems related to climate change and the liberalization of electricity markets. A general analysis of all the drivers that can affect hydropower is first carried out on the basis of a rich literature. Then, the impacts of climate change and market liberalization are analysed by means of specific quantitative methods. The case studies in Switzerland and Italy show that the impact of climate change is relatively low. Local characteristics are important. In addition, an appropriate management may significantly reduce energy production and revenue losses. Uncertainties about runoff are also relatively low, because long-term forecasting is only slightly affected by the different greenhouse gas scenarios. Electricity prices create more uncertainty. Results from a pumped-storage project upstream from the Mauvoisin dam show that present market conditions jeopardize investment in energy storage.