All NetMap Digital Hydroscapes (watershed datasets) come with meta data; however, datasets will not contain all meta data since it depends on what tools a user applies. In addition, NetMap tools and databases are continuously being updated. The latest meta data is obtainable online here.
Your existing metadata can be updated using ArcToolbox > Conversion Tools Metadata > Import Metadata.
Download this file and in the Import Metadata, it will be the Source Metadata, while your existing reach layer will be the Target Metadata.