Watershed Boundary Dataset HUC 6s

Retirement Notice: This item is in mature support as of April 2026 and will be retired in December 2027. A new version of this item is available for your use. Esri recommends updating your maps and apps to use the new version. Each drainage area is considered a Hydrologic Unit (HU) and is given a Hydrologic Unit Code (HUC) which serves as the unique identifier for the area. HUC 2s, 6s, 8s, 10s, & 12s, define the drainage Regions, Subregions, Basins, Subbasins, Watersheds and Subwatersheds, respectively, across the United States. Their boundaries are defined by hydrologic and topographic criteria that delineate an area of land upstream from a specific point on a river and are determined solely upon science based hydrologic principles, not favoring any administrative boundaries, special projects, or a particular program or agency. The Watershed Boundary Dataset is delineated and georeferenced to the USGS 1:24,000 scale topographic basemap. Hydrologic Units are delineated to nest in a multi-level, hierarchical drainage system with corresponding HUCs, so that as you move from small scale to large scale the HUC digits increase in increments of two. For example, the very largest HUCs have 2 digits, and thus are referred to as HUC 2s, and the very smallest HUCs have 12 digits, and thus are referred to as HUC 12s. Dataset Summary Phenomenon Mapped: Watersheds in the United States, as delineated by the Watershed Boundary Dataset (WBD) Geographic Extent: Contiguous United States, Alaska, Hawaii, Puerto Rico, Guam, US Virgin Islands, Northern Marianas Islands and American Samoa Projection: Web Mercator Update Frequency: Annual Visible Scale: Visible at all scales, however USGS recommends this dataset should not be used for scales of 1:24,000 or larger. Source: United States Geological Survey (WBD) Data Vintage: January 7, 2025 Questions? Please leave a comment below if you have a question about this layer, and we will get back to you as soon as possible.

退休通知：本数据集自2026年4月起进入成熟支持阶段，并将于2027年12月正式退役。目前已有新版本可供使用，Esri建议您更新相关地图与应用，以适配新版本。
每个汇水区均被视为水文单元（Hydrologic Unit, HU），并分配有水文单元代码（Hydrologic Unit Code, HUC）作为该区域的唯一标识符。其中，HUC 2、HUC 6、HUC 8、HUC 10与HUC 12级代码分别对应美国全境的流域大区、流域亚区、流域、子流域、小型流域与子小型流域。其边界依据水文与地形准则划定，界定了河流特定点位上游的陆地区域，完全基于科学水文原理确定，不偏向任何行政边界、专项工程或特定项目与机构。
本流域边界数据集（Watershed Boundary Dataset, WBD）依据美国地质调查局（United States Geological Survey, USGS）1:24,000比例尺地形底图进行划定与地理配准。水文单元采用多层级分级汇水系统进行嵌套划分，并配有对应的HUC代码，因此从低比例尺切换至高比例尺时，HUC代码的位数会以2位为增量递增。例如，级别最高的HUC包含2位数字，即HUC 2级；级别最低的HUC包含12位数字，即HUC 12级。
数据集概述
制图对象：美国境内由流域边界数据集（WBD）划定的流域
地理覆盖范围：美国本土、阿拉斯加州、夏威夷州、波多黎各、关岛、美属维尔京群岛、北马里亚纳群岛和美属萨摩亚
投影坐标系：网络墨卡托投影（Web Mercator）
更新频率：年度更新
可见比例尺：全比例尺下均可显示，但美国地质调查局建议本数据集不适用于1:24,000或更大比例尺的应用场景
数据来源：美国地质调查局（USGS）
数据时效时间：2025年1月7日
咨询方式：若您对此图层有任何疑问，请在下方留言，我们将尽快回复。