Capturing hotspots of fresh submarine groundwater discharge using a coupled surface–subsurface model

•A coupled surface-subsurface modeling approach is presented to estimate fresh SGD.•Fresh SGD to a 159km-long coast was 31% of river discharge and 14% of precipitation.•Our results suggested significant fresh SGD flows at riverbeds after river floods.•Variability of fresh SGD reduces substantially after aggregation in space and time.•The proposed approach bridges gaps between point measurements and global products.