Groundwater samples were collected from domestic and public-supply wells in the Eagle Ford study area in 2015–16, in the Fayetteville study area in 2015, and in the Haynesville study area in 2014–15. One sample of produced water was collected from a gas well in the Haynesville Shale in Rusk County, Texas in 2010, and 5 samples of produced water were collected from oil and condensate wells in the Eagle Ford Shale in Gonzales and Lavaca Counties, Texas in 2015. Groundwater samples were analyzed for major ions, nutrients, and trace elements; methane, methane H and C isotopic compositions, and C1-C5 gas composition; H and O isotopic composition of water; noble gas concentrations and isotopic compositions; tritium, sulfur hexafluoride (SF6), and carbon-14 in dissolved inorganic carbon (DIC), and δ13C-DIC; and volatile organic compounds (VOCs). Water from hydrocarbon wells was analyzed for a subset of these constituents.