This data release consists of data (in four tables) for assessing the time scales of arsenic variability in three production wells in New Hampshire; tables that describe the data fields in the data tables are also included in the data release. High-frequency (every 5 to 15 minutes) and bi-monthly water-quality monitoring of a bedrock-aquifer domestic well (425651070573701), a bedrock-aquifer public-supply well (425400070545401), and a glacial-aquifer public-supply well (425311070535801) was completed between 2014 and 2018. Concentrations of arsenic and other geochemical constituents and dissolved gases, as tracers of groundwater age, were measured on a bimonthly basis; physicochemical data, including specific conductance, pH, dissolved oxygen, pumping rate, and water level were measured at high-frequency intervals (every 5 to 15 minutes). Attached Files: Table_1_DGmodel2014-18.xlsx: Detailed information on the calibration of dissolved gas models to dissolved gas concentrations (neon, argon, krypton, xenon, nitrogen, oxygen, carbon dioxide, methane, hydrogen, and nitrous oxide). Table_2_Tracers2014-18.xlsx: Detailed information on calculations of environmental tracer data. Table_3_TracerLPM2014-18.xlsx: Dissolved gas modeling results, environmental tracer concentrations (tritium, tritiogenic helium-3, sulfur hexafluoride, carbon-14, and chlorofluorocarbons [CFCs], and results for the mean age of groundwater by calibration of lumped parameter models to tracer concentrations. Table_4_ConcentrationsValues2014-18.xlsx: Values of selected physiochemical parameters collected during well purging and selected chemical concentrations from filtered samples collected on various dates at each well; includes physical characteristics, depth to water, and pumping rate, calculated from continuous data.