The Grid-to-Grid (G2G) is a national-scale grid-based hydrological model which typically operates on a 1km x 1km grid at a 15-minute time-step (Bell et al. 2009). It was originally configured to cover Great Britain (GB) and output natural river flows, but was more recently extended to cover Northern Ireland (NI), and to take account of anthropogenic influences (abstractions and discharges) where available (Rameshwaran et al. 2022).