The very geography of Nepal and India is such that these two countries must engage with each other in social, economic, and political spheres; water resources is one of the most important spheres. This study reviews the experience of cooperation in the Kosi basin between India and Nepal, focusing on the perceptions of risks and opportunities by decision makers. The following five categories of risk are examined at four tipping points, 1954, 1966, 1991, and 2015: capacity and knowledge, accountability and voice, sovereignty and autonomy, equity and access, and stability and support. The study provides deeper insights about the perceived risks as far as negotiations on the proposed Kosi high dam are considered. The perceived risks have grown significantly from 1954 to 2015 for Nepal as compared to India. In 2015, Nepal has all five categories of perceived risks. The study also proposes risk reduction strategies to reduce the level of perceived risks for both Nepal and India, which is an area of future research. The study may facilitate the negotiation process for the Kosi High Dam Project leading to mutually agreed win-win solutions for both riparian countries. © 2019 American Society of Civil Engineers.