Watersheds for U.S Geological Survey National Stream Quality Accounting Network (NASQAN) sampling sites 1996-2000.

These data were released prior to the October 1, 2016 effective date for the USGS’s policy dictating the review, approval, and release of scientific data as referenced in USGS Survey Manual Chapter 502.8 Fundamental Science Practices: Review and Approval of Scientific Data for Release. A digital representation of the watersheds of 43 sites on large river systems sampled by the National Stream Quality Accounting Network (NASQAN) of the U. S. Geological Survey (USGS) in 2000 was created primarily from 1:250,000 hydrologic units(HUCs) in the United States. Watershed information from Canada and Mexico was incorporated to complete the areas draining to the sampling sites from outside the United States. The sampled rivers are in one of [...]

本数据集发布于2016年10月1日之前，彼时美国地质调查局（United States Geological Survey，简称USGS）有关科学数据审核、批准与发布的政策尚未生效，该政策详见《美国地质调查局勘测手册第502.8章：基础科学实践：科学数据发布的审核与批准》。2000年，美国地质调查局（USGS）下属的全国河流质量核算网络（National Stream Quality Accounting Network，简称NASQAN）针对其采样的大型河网中的43个点位的流域开展数字化表征工作，该数据集主要基于美国本土1:25万比例尺水文单元（Hydrologic Units，简称HUCs）构建。为完整覆盖采样点境外（美国以外）的汇水区域，研究团队整合了加拿大与墨西哥的流域相关数据。本次采样涉及的河流隶属于[...]