New Hampshire StreamStats

StreamStats for New Hampshire incorporates regression equations that can be used to estimate the long-term flood discharges at recurrence intervals of 2-, 5-, 10-, 25-, 50-, 100-, and 500-years. In addition, regression equations can provide estimates of the seasonal (spring, summer, fall, and winter) and annual 7-day 2-year (7Q2) and 7-day 10-year (7Q10) low-flow frequency values, as well as seasonal period-of record and period-of-record flow durations (60-, 70-, 80-, 90-, 95-, and 98-percent exceedences). The regression equations are applicable for ungaged reaches of unregulated New Hampshire streams. The reports below present the equations used to estimate the flow statistics, describe the errors associated with the estimates, and describe the methods used to develop the equations and to measure the basin characteristics used in the equations. Users should familiarize themselves with the reports before using StreamStats to obtain estimates of streamflow statistics for ungaged sites.

• Flynn, Robert H., 2003, Development of regression equations to estimate flow durations and low-flow-frequency statistics in New Hampshire streams: U.S. Geological Survey Water-Resources Investigations Report 02-4298, 66 p.
• (Flynn, R.H. and Tasker, G.D., 2004, Generalized Estimates from Streamflow Data of Annual and Seasonal Ground-Water-Recharge Rates for Drainage Basins in New Hampshire: U.S. Geological Survey Scientific Investigations Report 2004-5019, 61 p.
• Olson, S.A., 2009, Estimation of flood discharges at selected recurrence intervals for streams in New Hampshire: U.S. Geological Survey Scientific Investigations Report 2008-5206, 57 p.

Click on this link to obtain general information on the New Hampshire application, as well as specific sources and computation methods for basin characteristics. 

StreamStats outputs report the uncertainty of the estimates for ungaged basins when basin characteristics for selected sites are within the ranges of the basin characteristics for streamgages that were used to develop the regression equations. Errors for basins with basin characteristics that are beyond these bounds are unknown. The applicable ranges of the basin characteristics are provided in the outputs and messages are provided when basin characteristics are outside of the applicable ranges.

The above report by Olsen (2009) describes a technique for estimating flood discharges at selected recurrence intervals for an ungaged site upstream or downstream from a streamgage using a drainage-area adjustment that is not implemented in StreamStats. Interested users should refer to the report for information on use of the method. StreamStats includes a different method for making such adjustments.

The basin characteristics and streamflow statistics presented for streamgages in the report by Flynn (2003) are not yet available through StreamStats. As a result, outputs obtained for ungaged sites when using the Estimate Flows Based on Similar Streamgaging Stations tool will not include estimates of streamflow statistics based on those presented by Flynn (2003).