Watershed management varies greatly across the world. Local conditions are generally dictated by how watershed management is regulated at national, regional, and local scales. Both multisectoral and community-based participatory involvement in watershed management can positively impact the quality and effectiveness of outcomes. This localization can also be vital to the achievement of the UN’s Sustainable Development Goals. In recent years, the term “sustainability” has become overused, has limited quantifiable meaning, and can create “fuzzy” targets. We suggest that an outcome that focuses on “thrivability” is more appropriate; this refers to the ability to not only sustain positive conditions for future generations but to create conditions that allow for all living things (present and future) to have the ability and opportunity to thrive. A thrivability approach aligns with the 2030 Agenda’s ultimate goal: prosperity for all beings on earth. This study uses a thrivability lens to compare two study sites. Primary and secondary data were collected for both the Regional District of Nanaimo (RDN), Canada, and Hydrographic Region VIII (HR-VIII), Brazil, and have been input and analyzed through our Thrivability Appraisal to determine each region’s watershed thrivability score. The Thrivability Appraisal uses seven sustainability principles as the overarching framework. These are then related to four individual subcomponents of watershed health and three common interest tests based on primary environmental perception and secondary technical data as inputs. Assuming the centricity of water for prosperity, the final scoring is a culmination of the 49 total indicators. A comparison is then drawn to the regions’ capacity to achieve the eight targets for UN Sustainable Development Goal (SDG) 6. The outcome illustrates each region’s water management strengths and weaknesses, allowing for lessons to be learned and transferred to other multijurisdictional watersheds.

This article reviews recent studies that address water sustainable management opportunities and challenges in megacities around the world, with an emphasis on the case of Rio de Janeiro Metropolitan Region, one of the two megacities in Brazil. With reference to recent debates on water, megacities, and the climate crisis, as well as UN Water and Global Report Initiative documents, we focused on the implementation of the 2030 Agenda Sustainable Development Goal 6: Clean Water and Sanitation for All. The new Brazilian sanitation legal framework regulates public–private partnerships. In this context, the manuscript discusses the main question concerning water, sanitation, and hygiene that arises in the Brazilian case study: is universality possible in profit-oriented models? Through the current technical and academic literature consulted, the paper compares initiatives involving multiple stakeholder governance models that depend on private resources to implement universal access to drinking water, sanitation, and water-related extreme event controls, pointing out alternatives that can help to achieve the targets of SDG. Validation by key informants supports the synthesis of the reviewed documents, and the findings illustrate that concerted public efforts together with market mechanisms can help to overcome challenges and surpass the profit-oriented logics of private companies to achieve access to healthy and safe water, adequate sanitation, and improved hygiene, especially for vulnerable populations. This finding has transferability to other megacities in emerging countries that are facing public–private partnership debates on the provision of clean water and sanitation for all.