Attributes for NHDPlus Catchments (Version 1.1) for the Conterminous United States: Nutrient Inputs from Fertilizer and Manure, Nitrogen and Phosphorus (N&P), 2002

This data set represents the estimated amount of nitrogen and phosphorus in kilograms for the year 2002, compiled for every catchment of NHDPlus for the conterminous United States. The source data set is County-Level Estimates of Nutrient Inputs to the Land Surface of the Conterminous United States, 1982-2001 (Ruddy and others, 2006). The NHDPlus Version 1.1 is an integrated suite of application-ready geospatial datasets that incorporates many of the best features of the National Hydrography Dataset (NHD) and the National Elevation Dataset (NED). The NHDPlus includes a stream network (based on the 1:100,00-scale NHD), improved networking, naming, and value-added attributes (VAAs). NHDPlus also includes elevation-derived catchments (drainage areas) produced using a drainage enforcement technique first widely used in New England, and thus referred to as "the New England Method." This technique involves "burning in" the 1:100,000-scale NHD and when available building "walls" using the National Watershed Boundary Dataset (WBD). The resulting modified digital elevation model (HydroDEM) is used to produce hydrologic derivatives that agree with the NHD and WBD. Over the past two years, an interdisciplinary team from the U.S. Geological Survey (USGS), and the U.S. Environmental Protection Agency (USEPA), and contractors, found that this method produces the best quality NHD catchments using an automated process (USEPA, 2007). The NHDPlus dataset is organized by 18 Production Units that cover the conterminous United States. The NHDPlus version 1.1 data are grouped by the U.S. Geologic Survey's Major River Basins (MRBs, Crawford and others, 2006). MRB1, covering the New England and Mid-Atlantic River basins, contains NHDPlus Production Units 1 and 2. MRB2, covering the South Atlantic-Gulf and Tennessee River basins, contains NHDPlus Production Units 3 and 6. MRB3, covering the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy River basins, contains NHDPlus Production Units 4, 5, 7 and 9. MRB4, covering the Missouri River basins, contains NHDPlus Production Units 10-lower and 10-upper. MRB5, covering the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf River basins, contains NHDPlus Production Units 8, 11 and 12. MRB6, covering the Rio Grande, Colorado and Great Basin River basins, contains NHDPlus Production Units 13, 14, 15 and 16. MRB7, covering the Pacific Northwest River basins, contains NHDPlus Production Unit 17. MRB8, covering California River basins, contains NHDPlus Production Unit 18.本数据集记录了2002年美国本土毗邻地区所有NHDPlus汇水区的氮、磷估算量，单位为千克。其源数据集为《1982-2001年美国本土陆地表面养分投入县级估算》（Ruddy及其他作者，2006年）。 NHDPlus Version 1.1（NHDPlus V1.1）是一套集成化的可直接投入应用的地理空间数据集，整合了美国国家水文数据集（National Hydrography Dataset, NHD）与美国国家高程数据集（National Elevation Dataset, NED）的多项优质特性。该数据集包含基于1:10万比例尺NHD构建的河网系统，优化了网络关联、命名规则及增值属性（Value-Added Attributes, VAAs）。此外，NHDPlus还包含采用排水强化技术生成的高程衍生汇水区（汇水区域），该技术最早在新英格兰地区广泛应用，因此被称为“新英格兰方法”。该技术的具体流程为：将1:10万比例尺的NHD数据“嵌入”数字高程模型，若有可用数据则结合美国国家流域边界数据集（National Watershed Boundary Dataset, WBD）构建“边界墙”。经修改后的数字高程模型（HydroDEM）可用于生成与NHD和WBD匹配一致的水文衍生数据。在过去两年间，来自美国地质调查局（U.S. Geological Survey, USGS）、美国环境保护署（U.S. Environmental Protection Agency, USEPA）的跨学科团队及承包商经研究证实，该方法通过自动化流程可生成最高质量的NHDPlus汇水区（USEPA, 2007年）。NHDPlus数据集按照18个生产单元进行组织，覆盖美国本土毗邻全域。 NHDPlus V1.1数据按照美国地质调查局的主要河流流域（Major River Basins, MRBs, Crawford及其他作者，2006年）进行分组。其中：MRB1涵盖新英格兰与中大西洋河流流域，包含NHDPlus生产单元1和2；MRB2涵盖南大西洋-墨西哥湾和田纳西河流域，包含NHDPlus生产单元3和6；MRB3涵盖五大湖、俄亥俄河、上密西西比河及苏里斯-雷德-雷尼河流域，包含NHDPlus生产单元4、5、7和9；MRB4涵盖密苏里河流域，包含NHDPlus生产单元10-下和10-上；MRB5涵盖下密西西比河、阿肯色-怀特-红河及德克萨斯-墨西哥湾河流域，包含NHDPlus生产单元8、11和12；MRB6涵盖里奥格兰德、科罗拉多河及大盆地流域，包含NHDPlus生产单元13、14、15和16；MRB7涵盖太平洋西北部河流流域，包含NHDPlus生产单元17；MRB8涵盖加利福尼亚河流域，包含NHDPlus生产单元18。