This dataset contains a zipped file (dailyQs.zip) of daily streamflow data for 1,378 streamgages in 19 study regions in the conterminous U.S. from October 1, 1980 through September 30, 2013 from mostly undisturbed watersheds. USGS streamgages that were identified as being of “reference” quality in the GAGES-II dataset (https://water.usgs.gov/lookup/getspatial?gagesII_Sept2011) and had at least 10 complete water years (WYs) during the study period from WY1981 through WY2013 were selected. Daily streamflow data were retrieved from the National Water Information System (NWIS) on April 18, 2016. This dataset also contains an Excel file (compWYs.xlsx) indicating for each WY during the study period whether a streamgage had a complete streamflow record (no missing values) during that year. Only complete WYs of daily streamflow data during the study period from the selected streamgages were used to compute the empirical FDC quantiles to which regression equations were fitted. These data support a concurrent publication (Over and others, 2018).