The WA State National Hydrography Dataset (NHD) is the standard hydrography for Washington and contains linear watercourses representing streams, rivers, canals, ditches, coastline, pipelines, and artificial paths (centerlines through water polygon features such as lakes, estuaries, or double-banked streams). NHD Waterbody along with WA NHD Area represent the polygon water features.

Flowline data for Washington are developed at a resolution of 1:4,800 to 1:24,000. This dataset was extracted from the USGS in March 2019 and projected into WA State Plane Coordinates South. Strahler Stream Order has been added. The National Hydrography Dataset (NHD) is a feature-based database that interconnects and uniquely identifies the stream segments or reaches that make up the nation's surface water drainage system. This high-resolution NHD, generally is developed at 1:24,000/1:12,000 scale, but many areas of Washington State have been improved to 1:4800 scale. NHD data was originally developed at 1:100,000-scale and exists at that scale for the whole country. Local resolution NHD is being developed where partners and data exist. The NHD contains reach codes for networked features, flow direction, names, and centerline representations for areal water bodies. Reaches are also defined on waterbodies and the approximate shorelines of the Great Lakes, the Atlantic and Pacific Oceans and the Gulf of Mexico. The NHD also incorporates the National Spatial Data Infrastructure framework criteria established by the Federal Geographic Data Committee. Stream Orders in Washington State range from 1 to 10. The smallest headwater streams are a 1, and the Columbia River is a 10.

A detailed data dictionary is available at https://nhd.usgs.gov/userguide.html?url=NHD_User_Guide/Feature_Catalog/NHD_Feature_Catalog.htm

This feature class contains a BETA version of Water Type attached to the Skagit and Samish River Basin NHDFlowlines. This Beta version of the Water Type is the result of a pilot project. The field is for users of NHD who want access to Water Type and who are not under Forest Practices rules. The Water Type uses Shorelines Master Program, type S, streams and Fish Presence Data, type F streams, from both WA Dept Natural Resources and WA Dept Fish and Wildlife. Type N streams are those that are not S or F.