16-digit HU

Abstract: This file contains Hydrologic Unit (HU) polygon boundaries for the United States, Puerto Rico, and the U.S. Virgin Islands. The data is a seamless National representation of HU boundaries from 2 to 14 digits compiled from U.S. Geological Survey (USGS) National Hydrography Dataset (NHD) and U.S. Department of Agriculture (USDA) National Resources Conservation Service (NRCS) Watershed Boundary Dataset (WBD) sources. Purpose: This data is intended primarily for geographic display and analysis of regional and national data, and can also be used for illustration purposes at intermediate or small scales (1:250,000 to 1:2,000,000). See https://apps.nationalmap.gov/help/ for assistance with The National Map viewer, download client, services, or metadata.

摘要：本文件包含美国、波多黎各及美属维尔京群岛的水文单元（Hydrologic Unit, HU）多边形边界数据。该数据集为涵盖2至14位编码的水文单元边界的无缝全国范围数据集，整合自美国地质调查局（U.S. Geological Survey, USGS）的全国水文数据集（National Hydrography Dataset, NHD）以及美国农业部（U.S. Department of Agriculture, USDA）自然资源保护局（National Resources Conservation Service, NRCS）的流域边界数据集（Watershed Boundary Dataset, WBD）数据源。用途：本数据集主要用于区域及全国尺度地理数据的可视化展示与分析，亦可用于中、小比例尺（1:250000至1:2000000）场景下的制图演示。如需获取《国家地图（The National Map）》查看器、下载客户端、服务或元数据相关帮助，请访问https://apps.nationalmap.gov/help/。