I have produced two Hydro Networks (junctions and edges) for two Lidar tiles, and now I'm trying to combing these feature classes without destroying any of the attribute data.
In the attached image I have my two sets of tile junctions/edges. I removed the Hydro (Geometric) Network in order to use ArcMap's topology functions. After merging feature classes (X junctions merged to Y junctions / X lines merged to Y lines) I performed a series of "X features must not overlap Y features" and "no pseudo nodes" topology corrections. Through this, I was able to combine all the junctions and lines AND preserve all the original attribute information (with newly-calculated shape lengths, since some of the lines had been combined).
The problem is, I don't know how to put these junctions and lines "back" into a Hydro Network. The reason I'm interested in doing this is to use Utility Network Analyst to show flow direction for each of the lines. Is the Network even necessary? I suppose I don't really understand the functionality of these Hydro Networks.