Raster dataset showing saturated thickness (in feet) of the alluvium in the Lower Arkansas River Valley, Southeast Colorado, January 1 - May 31, 2015 and December 1 - 31, 2015 (hereafter defined as "spring"). Saturated thickness values based on water levels measured in the study area and median lake level at John Martin Reservoir during this time period. Surface interpolations for water-table altitude were done using Inverse Distance Weighting using coordinate and altitude data from "Wells and water-level altitude in the alluvium in the Lower Arkansas River Valley, Southeast Colorado, Spring and Fall 2002, 2008, and 2015" (see cross reference section in metadata), and surface interpolation of bedrock was done using Topo to Raster using elevation (20-ft contours) from "Bedrock contours underlying the alluvium of the Lower Arkansas River Valley, Southeast Colorado" (see cross reference section in metadata) in ArcGIS Desktop v10 (Environmental Systems Research Institute, 2011).