The comid field of these data can be used to join to the National Hydrography Dataset Plus V2.1 (NHDPlusV2) flowline comid or catchment featureid attributes. The included attributes follow the same data model as the NHDPlusV2 but include numerous updates and improvements to network connectivity. All attributes that depend on network connectivity have been recalculated. These attributes are based on the NHDPlusV2 network geometry and modifications retrieved from the National Water Model V2.1 (NWMv2.1) and "E2NHDPlusV2_us: Database of Ancillary Hydrologic Attributes and Modified Routing for NHDPlus Version 2.1 Flowlines" (E2NHDPlusV2) datasets. The attributes included are: comid, tocomid, fcode, nameID, lengthkm, reachcode, frommeas, tomeas, arbolate_sum, terminalpa ,hydroseq, levelpathi, pathlength, dnhydroseq, areasqkm, totdasqkm, terminalfl, dnlevelpat. These attributes are available in three formats: csv, fst, and parquet. "fst" is a high-performance format for use with the R programming language "fst" package. "parquet" is a high-performance format for use with multiple programming languages (including python) that support the Apache Arrow Parquet format.