Watershed Boundary - 10 Digit

This dataset at 1:24,000 scale is a greatly expanded version of the hydrologic units created in the mid-1970's by the U.S. Geological Survey under the sponsorship of the Water Resources Council. The WBD is a complete set of hydrologic units from new watershed and subwatersheds less than 10,000 acres to entire river systems draining large hydrologic unit regions, all attributed by a standard nomenclature. Development of the Watershed Boundary Dataset started in the early 1990's and has progressed to the format and attribution that is now being distributed. The delineation and attribution was done on a state basis using a variety of methods and source data. Each state HU dataset has gone through an extensive quality review process to ensure accuracy and compliance to the Federal Standard for Delineation of Hydrologic Unit Boundaries before and during submittal to USDA-NRCS National Geospatial Management Center (NGMC). More information can be found from the USGS Watershed Boundary Dataset page.本数据集比例尺为1:24000，是20世纪70年代中期由美国地质调查局（U.S. Geological Survey, USGS）在水资源委员会（Water Resources Council）资助下研制的水文单元的大幅扩充版本。流域边界数据集（Watershed Boundary Dataset, WBD）涵盖了从新划定的面积不足10000英亩的流域、子流域，到覆盖大型水文单元区域的完整河流水系在内的全套水文单元，所有要素均采用标准命名法完成属性标注。本流域边界数据集的研制始于20世纪90年代初，现已演进至当前对外分发的格式与属性规范。数据集的边界划定与属性标注以州为单位开展，采用了多种方法与源数据。每份州级水文单元（Hydrologic Unit, HU）数据集在提交至美国农业部自然资源保护局（United States Department of Agriculture - Natural Resources Conservation Service, USDA-NRCS）国家地理空间管理中心（National Geospatial Management Center, NGMC）的前后，均经过了严格的质量审查流程，以确保数据精度与合规性，符合《水文单元边界划定联邦标准》要求。更多详细信息可查阅美国地质调查局流域边界数据集官方页面。