What else do managers need to know about warming rivers? A United Kingdom perspective

River flow and water temperature are fundamental controls of freshwater ecosystems. Hence, future warming could impact valued habitats and species, particularly those with cold water preferences (such as salmonids). Warming could also exacerbate existing environmental pressures or diminish the effectiveness of management interventions. Climate model projections provide compelling evidence of the need for adaptation despite uncertainty about the timing, nature, and distribution of impacts on water quality, vulnerable species, and habitats. Low-regret adaptation options to manage temperature impacts include increasing riparian shade, enhancing thermal refugia, and removing thermal barriers or hotspots. Indirect controls include managing river flows through abstraction and discharge regulation, moderating flow control structures, and manipulating channel hydromorphology. However, fundamental gaps in understanding may limit the effectiveness of some of these measures, leading to undesired side effects, wasted resources, ineffectual outcomes, or limited uptake. These knowledge gaps include where to target measures, how to implement in different situations, how to maximize co-benefits and integrate with other policy objectives, and how to support implementation across rural and agricultural landscapes. Despite many uncertainties, restoration of riparian shade and river flows has the potential to deliver multiple benefits even if this does not include retarding rates of warming.