The High Plains aquifer extends from south of 32 degrees to almost 44 degrees north latitude and from 96 degrees 30 minutes to 104 degrees west longitude. The aquifer underlies about 175,000 square miles in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming. The Republican River Basin is about 25,000 square miles and is located in northeast Colorado, northern Kansas, and southwest Nebraska. The Republican River Basin overlies the High Plains aquifer for 87 percent of the basin area. This dataset consists of a raster of water-level changes for the High Plains aquifer, in the Republican River Basin, 2002 to 2015. This digital dataset was created using water-level measurements from (1) 977 wells, which are located in the Republican River Basin, and (2) 546 wells, which are located within 20 miles outside the boundary of the Republican River Basin. These 1,523 wells were measured in both 2002 and in 2015. The map was reviewed for consistency with the relevant data at a scale of 1:1,000,000.