LNWB Ch09 Artificial Drainage - agriculture parsels nooksack shape files

Compressed GIS files used in PhaseIIITask4 to create ditch and tile drain layers. Spatial data files specifying the areas with ditch and tile drainage were developed in 2004 by the USDA, Natural Resources Conservation Service (NRCS; Resource Conservationist, John Gillies, and Agricultural Engineer, Dean Renner). Drainage coefficients from NRCS technical guides are shown in Table 2. The drained areas were estimated using a geographic information system (GIS) to identify hydric soils on agricultural land use areas, based on the assumption that if a hydric soil was cleared and in agricultural use, then there was a drainage system in place to manage water using sub-surface (tile) and surface (open ditch) practices. For the Lower Nooksack Water Budget these are areas used to determine the tile drained and ditch drained fraction of each drainage model element as well as to assign drainage coefficients. This resource is a subset of the LNWB Ch09 Artificial Drainage Collection Resource.用于第三阶段任务4（PhaseIIITask4）中创建明沟与暗管排水图层的压缩型地理信息系统（Geographic Information System，GIS）文件。 2004年，美国农业部（United States Department of Agriculture，USDA）下属自然资源保护局（Natural Resources Conservation Service，NRCS；由资源保护学家约翰·吉利斯（John Gillies）与农业工程师迪恩·伦纳（Dean Renner）负责）编制了明确定义明沟与暗管排水区域的空间数据文件。NRCS技术指南中的排水系数详见表2。研究借助地理信息系统（GIS）识别农业用地范围内的湿土以估算排水区域范围，其核心假设为：若某湿土被开垦并用于农业生产，则当地配套建设了地下（暗管）与地表（明沟）排水系统以调控土壤水分。在努克萨克下游水量预算（Lower Nooksack Water Budget）中，此类区域用于确定各排水模型单元的暗管排水占比与明沟排水占比，并分配排水系数。 本数据集为LNWB第9章人工排水合集资源的子集。