Estimates of subsurface tile drainage extent for the conterminous United States, early 1990s

This dataset is a 30-meter resolution national-scale raster of estimated subsurface tile drainage extent based on early 1990s county areas of subsurface tile drains and geospatial datasets of cropland and poorly drained soil. Specifically, it was developed using 1) county-level acres of subsurface tile drain extents from Sugg (2007); 2) the extent of cultivated cropland from the National Land Cover Database (NLCD) 2011; 3) the extent of poorly drained soil from the State Soil Geographic (STATSGO) database Version 2; 4) the extent of federally-owned land, and 5) county administrative boundaries. Sugg's (2007) area of subsurface tile drains within each county was evenly allocated to potentially drained land -- cropland with poorly drained soil. The estimated area of subsurface tile drains in each cell is expressed in square meters. In most cases, the estimated subsurface drainage extent in each cell is less than the actual area of the cell in the raster. Sugg, Zachary, 2007, Assessing U.S. farm drainage: can GIS lead to better estimates of subsurface drainage extent?: World Resources Institute, Washington D.C., accessed December 2013, at http://www.wri.org/publication/assessing-us-farm-drainage.

本数据集为分辨率30米的国家级栅格数据，基于20世纪90年代初县级地下暗管排水（subsurface tile drainage）面积数据，以及耕地与低排水性土壤的地理空间数据集，估算得到全国地下暗管排水范围。具体而言，本数据集依托以下5类数据构建完成：1）Sugg（2007）发布的县级地下暗管排水面积数据；2）美国国家土地覆盖数据库（National Land Cover Database, NLCD）2011版的耕地范围数据；3）州土壤地理（State Soil Geographic, STATSGO）第二版数据库中的低排水性土壤范围数据；4）联邦所有土地范围；5）县级行政边界。Sugg（2007）统计的各县级地下暗管排水面积，被均匀分配至具备排水潜力的土地——即种植耕地且土壤为低排水性的区域。每个栅格单元内的地下暗管排水估算面积以平方米为单位表示。多数情况下，单个栅格单元内估算得到的地下暗管排水范围，小于该栅格单元的实际总面积。Sugg, Zachary, 2007年，《美国农田排水评估：地理信息系统（GIS）能否助力更精准的地下暗管排水范围估算？》，世界资源研究所，华盛顿哥伦比亚特区，2013年12月获取，网址：http://www.wri.org/publication/assessing-us-farm-drainage.