The environmental management of watersheds presents a complex governance issue due to their large spatial scales that include overlapping jurisdictions, competing interests in resource use, and lack of coordination among stakeholders. The Rideau Canal, spanning 200 km between the cities of Ottawa and Kingston, is an interesting case study as it is a multi-watershed system over which municipal, provincial and federal governments have authority. However, these governments have been unsuccessful in addressing system-wide issues such as shoreline development, erosion and invasive species that have significantly impacted the ecological integrity of the canal. A shift toward polycentric governance, which are systems of multi-scale governance, in which well-informed publics can contribute to the Rideau Canal’s management is required. This thesis examines how co-governance can be conceptualized for the RC by (1) analyzing convergences in stakeholder perspectives about the environment and governance, and (2) comparing collaborative causal mapping exercises with various stakeholders to current government engagement efforts. A tiered co-governance framework that intentionally links existing small-scale activities to system-wide formal venues of knowledge sharing could democratize environmental governance on the Rideau Canal to improve its management. Beyond its practical contributions, this research also contributes to developing the academic literature on co-governance for multi-watershed waterways that have both constructed and natural aspects.