Terminal basins are often highly sensitive to streamflow contributions, making them especially vulnerable to freshwater ecosystem degradation when streamflow is diverted or altered. The Great Salt Lake (GSL) terminal basin in Utah supports a unique ecosystem including the saline lake, peripheral wetlands, and snowmelt-driven streams, all which face high stress from competition for freshwater resources. Recent efforts to increase streamflow to GSL and reverse lake decline underscore the need to simultaneously consider instream flow requirements for contributing rivers and delivery needs for the GSL peripheral wetlands, so water dedicated and delivered to the GSL can achieve ecological benefits to the basin as a whole. Here we present a functional flows framework for rivers and managed wetlands draining to the GSL. Functional flows are components of the annual hydrograph that support riverine functions and processes critical to aquatic ecosystem health. Functional flow components specific to the GSL basin describe aspects of the region’s snowmelt-dominated annual hydrograph including winter low flow, spring ascension flow, peak flow, recession flow, and summer low flow, which are characterized by metrics quantifying the magnitude, timing, duration, frequency, and rate of change of flow. These metrics were generated for 180 reference-condition streamgages within the GSL basin and the Middle Rockies ecoregion. The functional flow metrics were then paired with basin characteristics and climate data to predict water year-specific functional flow target ranges at all ungaged streams in the GSL basin, and results are being made publicly available through map-based visualization. These predicted flows can be used as initial targets to inform decisions on when, where, and how much water to deliver to streams, managed wetlands, and the GSL.