Thank you very much, Mark! You gave me "more fuel" to keep moving ahead from the point i've been stuck for weeks! Good to know you had same difficulties with the batch delineation, so I don't credit my difficulties to my lack of experience. I'm trying to build an interesting model using the ArcGIS in a postdoctoral project, but I'm new to GIS and wouldn't have arrived where I am without the help of experienced users like you. I also have to say that the limitations of the tools (ArcMap and ArcHydro) and the "unhelpful help files" of both are very frustrating. I really thought the state of the art was more advanced. Anyway, I will start getting familiar this GeoHMS you mentioned and then try the path you suggested. I really appreciate your help!