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Increasing recognition of the importance of ecosystem services in water resources management has accelerated the development and applications of environmental flows requirements for lotic ecosystems which are often dependent on groundwater. However, most environmental flows management focuses on water infrastructure, like dams or diversions, without explicitly taking groundwater into account and ignoring the importance of groundwaters’ contribution to environmental flows. Here, we introduce two methods for estimating groundwater contribution to environmental flows: 1) a groundwater-centric method, which proposes that high levels of ecological protection are maintained if 90% of groundwater discharge is preserved and 2) a surface water-centric method, which quantifies groundwater’s contribution to environmental flows from streamflow using region-specific streamflow sensitivity metrics and local environmental flows policies. The two methods are tested in British Columbia, Canada, which has a diverse, complex, and highly coupled groundwater-surface water systems. The two methods gave comparable results in different hydrogeoclimatic settings. Though the two methods are demonstrated using British Columbia as a case study, this framework can be implemented across different spatial and temporal scales for different regions and globally in data-scarce, hydrologically complex landscapes. Application of these methods can aid in a robust and holistic assessment of environmental flows, taking into account the often missing groundwater component. Keywords: Groundwater, Environmental flows, British Columbia, Surface water …