USGS Watershed Boundary Dataset (WBD) Overlay Map Service from The National Map - National Geospatial Data Asset (NGDA) Watershed Boundary Dataset (WBD)

The Watershed Boundary Dataset (WBD) from The National Map (TNM) defines the perimeter of drainage areas formed by the terrain and other landscape characteristics....源自国家地图（The National Map，TNM）的流域边界数据集（Watershed Boundary Dataset，WBD），界定了由地形及其他景观特征所形成的汇水区域的周界……