Increased abundance and range expansions of non-native smallmouth bass (Micropterus dolomieu) in the upper Colorado River basin have coincided with declines in native fishes, therefore controlling smallmouth bass is a priority management strategy for native fish conservation. Abundance of smallmouth bass is known to vary in response to environmental conditions, with long growing seasons and hydrologic and thermal stability during the post- hatching period producing large cohorts of smallmouth bass. We used a recently developed population model for smallmouth bass in the Yampa and Green Rivers in the upper Colorado River basin to forecast smallmouth bass population responses to a range of potential future hydrologic conditions. The model combines daily river discharge and water temperature data to predict annual recruitment and incorporates impacts of density dependence, age specific natural mortality, and exploitation due to mechanical removal efforts. We simulated smallmouth bass responses across 400 hydrologic traces produced by ensembles of five different hydrologic models and assumed current policies driving reservoir storage and water release operations were maintained. Future hydrologic conditions will likely promote high population densities of smallmouth bass. Assessing responses of non-native species to future environmental conditions is a first step in identifying potential changes to current control methods, including increasing efforts or trying alternative methods.