1. Water-resource management should maintain ecological condition, including population viabilities of aquatic taxa. Many arid and semi-arid regions have experienced elevated water regulation and face drying and warming climates. 2. We combined stochastic, population dynamics models for four fish species with differing life histories with simulated regulated and unregulated flow regimes to assess the relative robustness of fish population persistence to different scenarios of climate change and water management. 3. Water regulation had a larger effect than differences in climate, negatively affecting one species through increased summer flows, and stabilizing population trajectories for two species that were sensitive to cease-to-flow events; the other species was insensitive to regulation or climate. 4. The greater importance of water regulation suggests that management of water regulation and human use can be used to insulate fish, to some degree, from the effects of future climate change. 5. General deductions from our results, such as the importance of inter-annual variability and the application of demographic modelling tools, are readily transferable to other systems. 6. Synthesis and applications. Our scenario-based approach was able to assess the population-level effects of multiple concurrent stressors and represents an effective framework for identifying management strategies that are robust to uncertainty in future environments.