The Cornerstones Report identifies the foundational elements that are required to develop and apply market-based options to sustain the freshwater environment and the water users who depend on it. Through an examination of these elements, the authors find that the barriers to market-based reallocation—namely the absence of sustainable limits on freshwater use, the lack of tradable water rights, and limited institutional capacity for measurement and enforcement—also hinder water sustainability efforts more broadly. Options for addressing these barriers are most effectively pursued at a local level in concert with state and federal agencies within the unique institutional, ecohydrological, and economic conditions of Arizona’s water geographies.