Is the flow accumulation tool in ArcHydro the same as the flow accumulation tool in the spatial analyst toolbox? The ArcHydro one is taking a very long time to run, and I'm wondering if the spatial analyst one will do any better. I'm using the tool on the BowlFDR, following along the steps in the ArcHydro tutorial, for Warren County, KY. The file size is over 4 gigs. The longest I've let it run is 5 days. The progress is always at "updating flow accumulation." Before I started using ArcHydro though, I could run flow accumulation for the county using the spatial analyst tool and it took less than a day. Will the results be any different using ArcHydro vs. spatial analyst?