Through ethnographic methods, this thesis investigates how adaptation projects for the Meuse (Netherlands) and Magdalena (Colombia) Rivers shape, legitimise, and contest dominant river futures. Chapter 2 conceptualises river imaginaries and shows how modern, market-driven, and eco-centric visions coalesce into an ecomodernist imaginary that consolidates truth regimes about river futures. Chapter 3 analyses the performative authority of the Dutch Maasmodel, demonstrating how modelling practices co-produce territorial transformations, reinforce dominant configurations, and constrain alternative imaginaries despite moments of counterperformativity or counter-modelling. Chapter 4 explores future-making in the Lower Magdalena, revealing how ecomodernist adaptation logics rely on manufactured ignorance that silences rooted, amphibian imaginaries. Chapter 5 shows how ecohydrological modelling naturalises river futures, rendering only calculable and codable futures legitimate while downplaying community concerns. The conclusion synthesises how ecomodernist norms shape adaptation governance, how models consolidate truth regimes, and how contestation emerges—highlighting the need for diverse onto-epistemic mediums capable of representing plural river imaginaries and enabling more just, representative river futures.