We introduce CoOPLAaGE, a meta-strategy and the related toolbox, supporting effective transformation in multi-level hydro-social systems, through participatory decision and implementation. Building on a set of international and diverse case studies over 15 years (Daniell et al., 2010)(Emeline Hassenforder, Ferrand, Pittock, Daniell, & Barreteau, 2015)(Legrand, Ducrot, Van Paassen, Monteiro, & Rousseau, 2014; Pommerieux, Bourblanc, & Ducrot, 2014)(Ferrand, Hassenforder, Ducrot, Barreteau, & Abrami, 2013)(Magombeyi, Rollin, & Lankford, 2008), selected principles, methods and tools have been improved and harmonized to support transformative processes at all governance and operations' scales. (Re-)Coupling scales, sectors, actors and perspectives, issues, methods, decision' steps is a complex challenge, with technical, social, procedural, methodological dimensions (see e.g. Saravanan, Mcdonald, & Mollinga, 2009). Through an integration and implementation focus, it can enhance the efficiency of public intervention and the mutual benefit from all actors' efforts. In this note, we summarize the key principles and expose an overview of this strategy. We develop the different components of CoOPLAaGE: PrePar for participatory engineering of decision procedures, SMAG for baseline governance assessment, Just-A-Grid for distributive justice dialogue, Wat-A-Game for participatory modeling and simulation, CooPlan for participatory planning, ENCORE-ME for monitoring and evaluation and Scoolplaage for capacity building.