Flowing through the political centre of Canada, the Ottawa River is an invaluable source of potable water, industrial sustenance, recreational mediation and aesthetic prestige. Inseparable from un-ceded Algonquin lands, the river divides two provinces and is governed by multiple political bureaucracies which take different approaches to water stewardship. The river may be healthier than it once was, but emerging Anthropocene threats like microplastics, low water levels during record breaking summer heat and neocolonial developments are enhancing regional water insecurity. Based on fieldwork conducted during the summer of 2016, this research describes how localized confluences of people, institutions, technology and non-human species are responding to assembling ecological pressures by configuring new approaches to Ottawa River watershed stewardship. I explore how such confluences constitute the citizen-science labour of the Ottawa Riverkeeper Riverwatcher monitoring program, the political activism of First Nations and allied resistance to the Energy East oil pipeline.