Hi, I'm not sure if this addresses your particular problem but I ran into something related. I went through the entire terrain evaluation process, sucessfully I thought until I got to the point of creating the geometric network. The network creation process failed on an invalid Grid-ID error, (don't recall the specific error message...it was different from the error message you saw, but...) Now to the point. After many hours of painstaking backtracking, I traced the problem to an area near the edge of the DEM where there was enough data for the system to delineate a drainage line but no catchment was created during the catchment phase, so the Grid-ID was not correctly populated, a problem which was further propogated as I moved through the Arc Hydro workflow. The problem steemed from the fact that I used a political boundary to clip my original DEM, which resulted in interterminate flow along the edge. I reclipped using a hydrologic boundary and everything worked swimmingly. Again, not sure this is applicable to your problem but I didn't know it was applicable to mine until I discovered it! Good Luck! Greg
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