This chapter presents case studies to better understand the causal mechanisms at work linking participation with environmental outcomes of decision-making processes (DMPs). It explores whether and how participation impacted on the environmental standards of planning outputs across the case studies, drawing on the causal mechanisms identified in. The chapter presents author's analysis by the followings: examining outputs; discussing conceptual mechanisms that potentially explain environmental output quality (mechanism clusters I–III); assessing actual implementation of plans in the studied sub-basins; and returning to explanatory mechanisms that address effective implementation (mechanism clusters IV and V). Whereas the first and second mechanism clusters describe the effects of participation in a more 'additive' logic (wherein participants bring in advocacy or knowledge individually), the third cluster engages with discursive interaction. Different styles and intensities of communication can evolve during group discussion in participatory processes, and impact on the environmental quality of process outputs.