- In the western United States, climate change is likely to bring greater uncertainty and extreme events outside the range for which water infrastructure, governance, and allocation mechanisms have been designed. In addition, many water systems already struggle with issues of institutional fragmentation, ineffective governance, and unsustainable management practices. Adaptive capacity, or the ability to cope with stressors and adjust to changing conditions, is a critical factor in reducing system vulnerability and increasing resilience. Two governance approaches, integrated water resources management and polycentricity, have been posited to increase adaptive capacity by reducing fragmentation of governance across sectors and levels of government. This paper examines the water planning and governance systems of 11 states to (1) assess the extent to which they incorporate or promote integrated resources management and polycentricity, and (2) characterize the states’ adaptive capacity based on the determinants of (a) comprehensiveness and integration, (b) knowledge and learning, (c) resources, (d) authority and legitimacy, and (e) participation and networks. While governance approaches among states differ based on their historical development, stakeholder preferences, and other contextual factors, states which incorporate more integrated water resources management principles and display more polycentric tendencies in their water governance were found to have higher levels of all adaptive capacity determinants except for resources. Potential approaches to increase adaptive capacity and promote sustainable, secure water futures in the study area could include better integration of management concerns, greater data sharing and accessibility, dedicated investment in water planning and project implementation, enabling communities or regions to self-organize and tailor local solutions to water issues, and building more inclusive stakeholder engagement and participation processes. The development of inclusiveness and local self-organizing authority could be particularly critical in overcoming institutional rigidity and path dependence, helping to gain the public support needed to reshape entrenched systems.