Here I read that the Norwegians could find an extra 20 GW generating capacity, without spoiling their nature too much. Sweden would be less than that. About storage capacity (TWh), I understand that it would be "plenty" :-)

http://www.cedren.no/Portals/Cedren/Pdf/HydroBalance/1_HarbyA_Balancing%20power%20from%20Norwegian%2 0hydro.pdf

This is a slide show. There was a real report by CEDREN somewhere but I cannot find it now.