Hydrologic Unit (HUC8) Boundaries for Alaskan Watersheds

The United States is divided and sub-divided into successively smaller hydrologic units which are classified into four levels: regions, sub-regions, accounting units, and cataloging units. The hydrologic units are arranged or nested within each other, from the largest geographic area (regions) to the smallest geographic area (cataloging units). Each hydrologic unit is identified by a unique hydrologic unit code (HUC) consisting of two to eight digits based on the four levels of classification in the hydrologic unit system. A shapefile (or geodatabase) of watersheds for the state of Alaska and parts of western Canada was created by merging two datasets: the U.S. Watershed Boundary Dataset (WBD) and the Government of Canada's National Hydro Network (NHN). Since many rivers in Alaska are transboundary, the NHN data is necessary to capture their watersheds. The WBD data can be found at https://catalog.data.gov/dataset/usgs-national-watershed-boundary-dataset-wbd-downloadable-data-collection-national-geospatial- and the NHN data can be found here: https://open.canada.ca/data/en/dataset/a4b190fe-e090-4e6d-881e-b87956c07977. The included python script was used to subset and merge the two datasets into the single dataset, archived here.

美国被逐层划分为尺寸依次缩小的水文单元，该分类体系共设四级：区域、亚区域、核算单元与编目单元。水文单元彼此嵌套，覆盖范围从最大的地理区域（区域）逐步收缩至最小的地理单元（编目单元）。每个水文单元均配有唯一的水文单元代码（hydrologic unit code, HUC），代码长度为2至8位数字，匹配水文单元体系的四级分类规则。本数据集整合了阿拉斯加州及加拿大西部部分区域的流域形状文件（shapefile）或地理数据库（geodatabase），整合来源为两份公开数据集：美国国家流域边界数据集（U.S. Watershed Boundary Dataset, WBD）与加拿大政府国家水文网络（National Hydro Network, NHN）。鉴于阿拉斯加州存在多条跨境河流，需依托加拿大国家水文网络的数据方能完整覆盖其流域范围。美国国家流域边界数据集的获取地址为https://catalog.data.gov/dataset/usgs-national-watershed-boundary-dataset-wbd-downloadable-data-collection-national-geospatial-，加拿大国家水文网络的数据获取地址为https://open.canada.ca/data/en/dataset/a4b190fe-e090-4e6d-881e-b87956c07977。本次附带的Python脚本用于对两份数据集进行子集提取与合并，以生成本单一数据集，相关存档文件可于此获取。