Methods for computing 7Q2 and 7Q20 low-streamflow statistics to account for possible trends

First posted June 3, 2022 For additional information, contact: Director, New England Water Science CenterU.S. Geological Survey10 Bearfoot RoadNorthborough, MA 01532 Low-streamflow statistics, such as the annual minimum 7-day streamflow (which is likely to be exceeded in 9 out of 10 years on average [7Q10]), that are computed by using full historical record may not accurately represent current conditions at sites with statistically significant trends low over time. Recent research suggests a contemporary subset (specifically, most recent 30 years) compute an estimate 7Q10 more represents when trend present. This report presents results Monte Carlo simulation experiment artificial low-streamflow records, derived from characteristics streamflows 174 U.S. Survey streamgages, test whether similar approach appropriate for computation 1 2 (7Q2) and 19 20 (7Q20). The indicate 30-year also best computing 7Q2 7Q20 where detected.