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.