Mitigating the effects of salinity (total dissolved solids [TDS]) and selenium on water quality in the lower Gunnison River Basin of western Colorado is a major concern for land managers. In cooperation with the Bureau of Reclamation, the U.S. Geological Survey completed a study to develop multiple linear regression (MLR) models to estimate salinity and selenium loads in the lower Gunnison River Basin. The objective of the study was to refine existing models by improving the regressions and using additional geospatial and water-quality data. This data release presents the basin characteristics and loads used to calibrate the models. Also provided are salinity and selenium yield rasters determined by empirical Bayesian kriging of loads estimated by the models. The yield rasters define the study area boundary. The "Lower_Gunnison_River Basin_Data.7z" file contains subfolders for the salinity (TDS) and selenium (Se) data. Both subfolders contain raster datasets used to compute basin characteristics (variables), a shapefile of basin characteristics and loads used as input to the models, a raster dataset of predicted yields, and individual metadata files for the shapefile and raster data. The raster datasets also represent the boundary of the study area.