My study area is too large to be processed in its entireity by any hydrological modelling software I have found yet. I will have to break it up in to smaller areas, but there will be flow across these tiles. My outcome needs to include the total flow for each stream. Are there any tips or best practices for approaching this?
EDIT: My study area is 3740 square km and the DEM is 1 metre resolution (from lidar). It can be split into two major watersheds of roughly equal size. I'd assumed these would be too large to process on their own as I have trouble even loading them into most software.