Watershed-wide Priority Agricultural Watershed Rankings 2021

Open the Data Source: https://gis.chesapeakebay.net/ags/rest/services/PriorityAgriculturalWatersheds/PAW_WW_2021/MapServer/0 In 2010, the U.S. Environmental Protection Agency (EPA), U.S. Geological Survey (USGS) and regional Land Grant Universities developed Priority Agriculture Watershed (PAW) maps to inform where to focus federal funding for agricultural conservation practices to reduce the greatest nitrogen and phosphorus loads to the tidal Chesapeake Bay. Since then, Priority Agriculture Watershed maps have been used to target implementation funds including EPA Region 3 Chesapeake Bay Implementation, Regulatory and Accountability Program grants, National Fish and Wildlife Foundation (NFWF) Chesapeake Bay Stewardship grants and U.S. Department of Agriculture Natural Resource Conservation Service (NRCS) Farm Bill programs. The NRCS targeting effort was the precursor to USDA creating the Chesapeake Bay Watershed Initiative which created dedicated Farm Bill funding for the watershed. The data layers used to create the original 2009 maps were updated by a 2018 release of the USGS SPARROW model (https://doi.org/10.3133/sir20185051) for delivered loads of nitrogen or phosphorus from agricultural sources, agricultural land uses and Clean Water Act Section 303(d) 2016 reports used to emphasize local waters impaired from potential agriculture-related sources. This approach integrates modeling (SPARROW) and monitoring (303d) data to prioritize USGS 12-digit hydrologic units (HUCs) for Chesapeake Bay and local water quality benefits. The PAW analysis ranked HUCs across the Chesapeake Bay watershed in terms of their contribution of nitrogen (N) and phosphorus (P) pollutants to Chesapeake Bay streams. HUCs that fell above a threshold to be considered an Agricultural HUC (AgHUC) were ranked across the watershed based on SPARROW modeled stream pollutant movement between catchments, or Delivered Loading Rate (DLR), for N and for P separately. These rankings were performed across the watershed as well as across each state to enable more flexible mapping comparisons, and especially to facilitate interactive web applications for the public to use to examine results. In addition, the fraction of all SPARROW-derived local catchment 303(d) assessed streams that were in SPARROW-derived agricultural catchments, and that carried 303(d) Agriculture-related pollutants within the same HUC, was produced in this analysis. Percent rankings for the fractional data was not created as it was deemed inappropriate due to the meaningful coarseness of this statistic. This dataset represents the watershed-wide rankings. State-specific rankings can be found here: https://gis.chesapeakebay.net/ags/rest/services/PriorityAgriculturalWatersheds/PAW_WW_2021/MapServer/0打开数据源：https://gis.chesapeakebay.net/ags/rest/services/PriorityAgriculturalWatersheds/PAW_WW_2021/MapServer/0 2010年，美国环境保护署（U.S. Environmental Protection Agency, EPA）、美国地质调查局（U.S. Geological Survey, USGS）以及区域赠地大学联合研发了优先农业流域（Priority Agriculture Watersheds, PAW）地图，用于明确联邦资金的投向重点，以开展农业保护措施，最大程度削减输入潮汐切萨皮克湾的氮、磷负荷。 此后，优先农业流域地图被用于定向拨付各类实施资金，包括EPA第三区切萨皮克湾实施、监管与问责计划拨款、美国国家鱼类和野生动物基金会（National Fish and Wildlife Foundation, NFWF）切萨皮克湾管护拨款，以及美国农业部（U.S. Department of Agriculture, USDA）自然资源保护服务局（Natural Resource Conservation Service, NRCS）的农业法案项目。 NRCS的定向工作是美国农业部设立切萨皮克湾流域倡议的前置基础，该倡议为该流域设立了专项农业法案资金。 2018年发布的USGS SPARROW模型（https://doi.org/10.3133/sir20185051）更新了用于制作2009年原始地图的数据图层，该模型用于模拟农业源氮、磷输送负荷、农业土地利用情况，以及《清洁水法》第303(d)条2016年报告，以凸显受潜在农业相关污染源影响的本地受损水体。 本研究方法整合了建模（SPARROW）与监测（303(d)）数据，以对切萨皮克湾流域及本地水质效益相关的USGS 12位数字水文单元（hydrologic units, HUCs）进行优先级排序。 优先农业流域分析针对切萨皮克湾流域内的水文单元，按照其向切萨皮克湾溪流输送氮（N）、磷（P）污染物的贡献进行排名。将满足农业水文单元（Agricultural HUC, AgHUC）阈值的水文单元，基于SPARROW模型模拟的集水区间溪流污染物迁移过程，分别针对氮和磷的输送负荷率（Delivered Loading Rate, DLR）进行流域范围内的排名。 此类排名同时在全流域及各州范围内开展，以支持更灵活的制图对比，尤其便于开发面向公众的交互式网络应用程序，供其查询分析结果。 此外，本分析还生成了两项指标的占比数据：一是经SPARROW模型识别的农业集水区内，接受303(d)条款评估的本地溪流占所有经SPARROW模型评估溪流的比例；二是这些溪流在同一水文单元内携带农业相关污染物的比例。由于该统计指标存在固有粗粒度特征，被认为不适用于百分比排名，因此未对分数数据生成排名结果。 本数据集代表全流域范围内的优先级排名结果。各州专属的优先级排名可通过以下链接获取：https://gis.chesapeakebay.net/ags/rest/services/PriorityAgriculturalWatersheds/PAW_WW_2021/MapServer/0