Data release containing geospatial data and metadata for select hydrogeologic characteristics of the alluvium in the Lower Arkansas River Valley, Southeast Colorado, 2002, 2008, and 2015. This data release accompanies U.S. Geological Survey Scientific Investigations Map 3378 (https://doi.org/10.3133/sim3378). Geospatial datasets and metadata include: - Rasters showing estimated thickness of the alluvium; fall-to-fall and spring-to-spring water-table altitude change, 2002 to 2008, 2008 to 2015, and 2002 - 2015; and estimated saturated thickness in the alluvium, fall and spring 2002, 2008, and 2015. - Shapefiles showing bedrock contours underlying the alluvium; the outline of the study area and John Martin Reservoir in Bent County, Colorado; well locations and measured water-level altitude in those wells in the fall and spring of 2002, 2008, and 2015. For the purposes of this data release, "fall" is defined as June 1 through November 30, and "spring" is defined as January 1 through May 31 and December 1 through 31 of the same year.