I need to do a bunch of analysis on a city using for that, watersheds . As smaller the watersheds are, better are quality of my work. Due to the vertical accuracy of SRTM DEM, I know there are some limitation of area. For example, as smaller the areas are, less diluted the errs are. I was wondering if anybody could shed a light on how small my watershed areas could be and still be Trustworthy. Indication of any paper or article would also help.