HUC8 - CONUS Shapefile

This resource contains a shapefile of HUC-8 (eight digit Hydrologic Unit Codes) for the Continental United States (CONUS).

The Watershed Boundary Dataset (WBD) is a comprehensive aggregated collection of hydrologic unit data consistent with the national criteria for delineation and resolution. It defines the areal extent of surface water drainage to a point except in coastal or lake front areas where there could be multiple outlets as stated by the "Federal Standards and Procedures for the National Watershed Boundary Dataset (WBD)" “Standard” (http://pubs.usgs.gov/tm/11/a3/). Watershed boundaries are determined solely upon science-based hydrologic principles, not favoring any administrative boundaries or special projects, nor particular program or agency. This dataset represents the hydrologic unit boundaries to the 12-digit (6th level) for the entire United States. Some areas may also include additional subdivisions representing the 14- and 16-digit hydrologic unit (HU). At a minimum, the HUs are delineated at 1:24,000-scale in the conterminous United States, 1:25,000-scale in Hawaii, Pacific basin and the Caribbean, and 1:63,360-scale in Alaska, meeting the National Map Accuracy Standards (NMAS). Higher resolution boundaries are being developed where partners and data exist and will be incorporated back into the WBD. WBD data are delivered as a dataset of polygons and corresponding lines that define the boundary of the polygon. WBD polygon attributes include hydrologic unit codes (HUC), size (in the form of acres and square kilometers), name, downstream hydrologic unit code, type of watershed, non-contributing areas, and flow modifications. The HUC describes where the unit is in the country and the level of the unit. WBD line attributes contain the highest level of hydrologic unit for each boundary, line source information and flow modifications.

本资源包含美国大陆（CONUS）HUC-8（八位水文单元代码）的shapefile。水土流域边界数据集（WBD）是一套综合的、符合国家划界和分辨率标准的 hydrologic unit 数据集合。它定义了地表水径流至某一点的区域范围，除非在沿海或湖岸地区，根据“联邦国家水土流域边界数据集（WBD）标准和程序”（http://pubs.usgs.gov/tm/11/a3/）“标准”所述，可能存在多个出口。水土流域边界仅基于科学的水文原则确定，不偏袒任何行政边界或特殊项目，也不偏袒特定项目或机构。本数据集表示整个美国的水文单元边界至12位（第六级）。某些区域还可能包括表示14位和16位水文单元（HU）的附加子划分。至少，水文单元在美国大陆的划界比例尺为1:24,000，夏威夷、太平洋盆地和加勒比地区的比例为1:25,000，阿拉斯加的比例为1:63,360，符合国家地图精度标准（NMAS）。在合作伙伴和数据存在的地方，正在开发更高分辨率的边界，并将将其纳入WBD。WBD数据以多边形及其对应线条的集合形式提供，这些线条定义了多边形的边界。WBD多边形属性包括水文单元代码（HUC）、面积（以英亩和平方公里表示）、名称、下游水文单元代码、流域类型、非贡献区域和流量修改。HUC描述了单元在国家中的位置和单元的级别。WBD线条属性包含每个边界的最高级别水文单元、线条来源信息和流量修改。