Dams affect rivers and other freshwater ecosystems around the world. The structural performance and service delivery of many dams has seldom been assessed; many are unsafe and no longer deliver designed benefits. Changes in hydrology from climate change will require assessment of safety and operations of infrastructure. This creates an opportunity during relicensing for modification or removal of dams to render them safe, maximise their services and minimise social and environmental impacts. We examined case studies of reassessment of dams from Australia (New South Wales), China, France and the United States that illustrated the following: the management challenge of aging and unsafe dams; unrealised opportunities to improve environmental, social and economic benefits; and the benefits of inventory and relicensing systems. Key elements of an ideal regulatory system to optimise water infrastructure performance are identified, comprising periodic (time-limited) relicensing of all infrastructure overseen by an independent regulatory agency that would take decisions in the public interest through a transparent process, involving public participation. Each dam would have an identified owner who must apply best-available technologies to maximise safety, socioeconomic and environmental performance. Dam renovation could minimise current non-climate impacts, improve migration of aquatic wildlife and even attenuate some climate impacts on freshwater biota.