The datasets provide Grid-to-Grid (G2G) hydrological model estimates of daily mean river flow (m3s-1) on a 1 km x 1 km grid. The river flows provided here are generated using the G2G model for Great Britain driven by observation-based meteorological data. They provide spatially consistent simulations of natural and anthropogenically influenced daily mean river flows. The natural flows are for the period 1st January 1961 to 31st December 2021, the observed-anthropogenically influenced flows are for 1st January 1999 to 31st December 2014 and the mean-anthropogenically influenced flows are for 1st January 1961 to 31st December 2021. The G2G hydrological model spatial river flow simulations are available as follows: (a) Natural river flows across the whole of Great Britain, excluding Orkney and Shetland islands (b) Anthropogenically influenced river flows across the whole of England Full details about this dataset can be found at https://doi.org/10.5285/d0588746-9632-4c75-94f2-67e20ba34cad