Delineating Watersheds using NHDPlus V.2 Data

Hello everyone!

I'm pretty new to GIS however I am using ArcMap 10.0 and ArcHydro 2.0?.. anyways the pre-processing for watershed delineation is pretty much the same it seems with older versions of archydro.

I have pre-processed all of the NHDPlus v.2 data for the United States (i.e. built stream grids (@5000 cells), stream links, catchment grids, catchments, drainage lines, and adjoint catchments for each HUC2 and its sub-sections. I used the pre-made "fdr" and "fac" raster files that I downloaded from NHDPlus V.2 website: http://www.horizon-systems.com/nhdpl...lusV2_data.php

I want to be able to merge my created grids and layers so that I can delineate by point from wherever. Right now I can easily delineate watersheds by point within each sub-section, however if I have larger watersheds that I would like to create (i.e. Brazos R.), it doesn't delineate the entire watershed because the grids are too small for the basin. I've tried to merge the rasters via "Mosaic to Rasterdataset" tool and the layers with the "Merge" tool but it's not registering anything. I think its because I'm not calculating any cells properly? I just want to be able to delineate larger watersheds using my already pre-processed data.

Any thoughts on this or help with this would be great :) :)

Thank you,

~Sydney~