Understanding the conditions that favor the persistence of metapopulations inhabiting riverine landscapes is a critical challenge in guiding conservation and restoration efforts aimed at preserving the biodiversity and ecological integrity of freshwater environments. In this work, we propose a modeling framework to investigate the transient persistence of fluvial metapopulations, i.e., the temporary occupation of riverscape patches by a metapopulation that is expected to go extinct in the long run. The theoretical foundation of our approach is rooted in the concept of ecological reactivity, which provides an effective complement to asymptotic stability analysis for studying the short-term response of ecological systems to impulsive perturbations to otherwise stable equilibria. Our results indicate that, under ecohydrological conditions conducive to a reactive metapopulation extinction equilibrium, even a metapopulation that is asymptotically bound to extinction can colonize parts of the riverscape for non-negligible periods of time. We find that the temporal scales associated with these transient phenomena, in the presence of repeated positive perturbations of the extinction equilibirum, may allow for reactive pseudo-persistence, i.e., an arbitrarily long delay in the eventual extinction of the metapopulation that may occur well below the deterministic extinction threshold. By identifying the ecohydrological drivers of reactive metapopulation persistence, as well as the riverscape patches that contributes the most to transient metapopulation dynamics over different temporal scales, our analysis may provide valuable suggestions for the spatial prioritization of conservation and restoration efforts.