Just for the record, the calculation time; > GRASS 6.4.2svn (patUTM32):~ > r.watershed italy_dem20_final > stream=stream_total accumulation=accumulation_total threshold=10000 -m > memory=2000 (cells: 364 million) GRASS 6.4.2svn: done in two hours. GRASS 7,svn, on the same machine: 36 min :) Markus