The U.S. Geological Survey (USGS ), in cooperation with the Bureau of Reclamation, completed a review of dissolved selenium data collected from the Selenium Management Program network during each water year (WY) in the lower Gunnison River Basin, in western Colorado. The data tables include dissolved-selenium concentrations, selected streamflow data, and computed loads as well as dissolved selenium regression model calibration and output tables. Concentration and streamflow data are compiled from the USGS National Water Information System database. Tables include monitoring location identification information, data collection time frames, concentration data, as well as calculations of mean, median, select percentiles, and percentage reduction in loads. Tables are organized by each year, with a zipped folder for WY 2018 (October 1, 2017 through September 30, 2018) and WY 2019 (October 1, 2018 through September 30, 2019). Within each zipped folder is a metadata .xml file describing each comma-separated value (.csv)data file contained therein . The methods used to complete this review are available in Henneberg (2018), and Mayo and Leib (2012).