Executive summary:
This work conducts a desk literature survey, complemented with deep dive case studies involving experts and key stakeholders from 8 international basins representative of different socioeconomic and biophysical contexts, to document the barriers (and opportunities) for Transformational Adaptation Policies (TAP) adoption. We apply inductive methods to identify common candidate theories across case studies that explain the emergence and persistence of barriers for TAP adoption, while identifying enablers that may help overcome these barriers. We assess the ways in which key players in the water policy arena (including water users, regional communities, decision-makers, regulators, water works suppliers, donors) may contribute to create barriers to TAP adoption; and how this network of players and their interactions condition the relevance and strength of these barriers. Leveraging on this information, we propose a series of common principles and guidelines centered around regulations, institutions and policy, incentives, information, and debiasing, to guide the adoption of TAP that contribute to sustainable and equitable economic development and welfare growth, including under conditions of uncertainty.