This paper introduces a new approach for setting streamflow-based river ecosystem management targets and this method is called the "Range of Variability Approach" (RVA). The proposed approach derives from an aquatic ecology theory concerning the critical role of hydrological variability and associated characteristics of timing, frequency, duration and rates of change, in sustaining ecosystems. The method is intended for application on rivers wherein the conservation of native aquatic biodiversity and protection of natural ecosystem functions are primary river management objectives.