In the context of climate change, hydropower dams and reservoirs are being promoted as mitigation and adaptation tools. The reoperation of dam reservoirs is also being considered, particularly in countries where dams are currently undergoing relicensing procedures. In Switzerland, a country that is often considered to be the water tower of Europe, concerns are being expressed about the future of water resources. These concerns are reinforced by the fact that the country’s water system is heavily impounded by hydropower dams whose licenses are about to expire. Discussions are emerging on future hydropower production and on multipurpose projects in the context of hydropower dam reservoir reoperation. Building on previous studies in political ecologies of water and on studies of environmental and sociotechnical imaginaries, and relying on policy documents and interviews with water and energy stakeholders, we investigate the way in which multiple use of hydropower dam reservoirs is envisioned in Switzerland and in the Valais canton. At the moment in Switzerland, the idea of multiple use of dam reservoirs is far from being recognised as a water and energy management paradigm; it is, however, strongly associated with climate-related socio-environmental changes in the water sector and with changes in ideas about water, dam futures, energy and the social structure. We highlight the coexistence of three different environmental and sociotechnical imaginaries and connect these imaginaries with ongoing and future hydrosocial change.