The following files contain NHD flowlines and waterbodies, organized by HUC-04 watersheds for 0204, 0205, 0206, 0207, and 0208. The source for the data is the NHD plus high resolution dataset (U.S. Geological Survey, 2017). U.S. Geological Survey, 2017, National Hydrography Dataset Plus High Resolution (NHDPlus HR) - USGS National Map Downloadable Data Collection: .
The following files contain physiographic region boundaries for the Chesapeake Bay Watershed (CBW) and Delaware River Basin (DRB). The source for the CBW is the Hydrogeomorphic Regions of the Chesapeake Bay Watershed: HGMR (Brakebill & Kelley, 2000). The source for the DRB is the EPA Level III Ecoregions of the Continental United States (USEPA, 2011).