Increasing frequencies of droughts and hot extremes, as well as increasing precipitation variabilities worldwide, can trigger conflicts of water use. Proactive and sustainable water management is required, that can benefit from basing decisions on longer-range weather forecasts such as the subseasonal- to seasonal (S2S) timescale that aim to predict hydrometeorological development of events in the coming weeks and months. This ICCLAS-led session aims at consolidating the current state of opportunities for hydrological decision making on S2S predictability, particularly in reservoir operation for hydroelectric power generation, irrigation and water resources. We invite for both disciplinary and cross-disciplinary abstracts from climate, hydrology and engineering sciences. We ask particularly for contributions addressing 1) skill analyses of S2S predictions, 2) statistical postprocessing and skill improvement approaches, 3) community efforts to provide operational products, and 4) efforts bridging from science to practice. Interdisciplinary case studies for different climate regions worldwide are particularly encouraged.