Washington State Department of EcologyThe WA State National Hydrography Dataset (NHD) is the standard hydrography for Washington. NHD Lines represent linear NHD hydrographic landmark features used for cartographic representation. Some of these are: Bridge, Dam, Flume, Gate, Levee, Sounding Datum Line. NHD Lines should not be confused with NHD Flowlines which are the major blue line data. NHD Line data for Washington are developed at a resolution of 1:4,800 to 1:24,000. This dataset was extracted from and projected into WA State Plane Coordinates South. The National Hydrography Dataset (NHD) is a feature-based database that as a whole 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. A detailed data dictionary is available at https://nhd.usgs.gov/userguide.html?url=NHD_User_Guide/Feature_Catalog/NHD_Feature_Catalog.htmArcGIS FeatureLayerhttps://hub.arcgis.com/datasets/78b89fab8d9e42079c43aaca6961728d_4engState of Washington Geospatial Open Data PortalPublicHydrography - NHD Lines [Washington (State)]Web servicesWashington (State)Last Modified: 2025-08-14