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Water Resources of New Hampshire and Vermont
The New Hampshire Watershed Tool


Cooperator: New Hampshire Department of Environmental Services,

Project Contact for further information: Robert Flynn, 603-226-7824,

Project Description: Estimates of low-flow statistics, flow durations, and ground-water-recharge rates are needed to assist water-resource managers in assessing surface-water resources and ground-water availability during periods of low flow in New Hampshire. Often these estimates are required at ungaged sites where no observed streamflow data are available for analysis. The U.S. Geological Survey (USGS), in cooperation with the New Hampshire Department of Environmental Services (NHDES), developed regression equations for estimating the (1) spring, summer, fall, winter, and annual 7-day, 2-year and 7-day 10-year low flows; and the (2) spring, summer, fall, winter, and annual 60-, 70-, 80-, 90-, 95-, and 98-percent flow durations. A report by Flynn (2003) documents the development of the streamflow-frequency estimation equations. Regression equations were also developed for estimating the spring, summer, fall, winter, and annual ground-water-recharge rates. A report by Flynn and Tasker (2004) documents the development of these equations. (see related reports below)

The New Hampshire Watershed Tool (NHWT), a geographic information system (GIS) application, was created to automate the determination of basin-characteristics required for the flow-frequency and ground-water-recharge equations. The Tool then applies the equations to estimate low-flow frequency, flow duration, or ground-water recharge for a user-selected point on a stream. The Tool is built upon the National Hydrography Dataset (NHD) and NHD Watershed Tool. The application customized for New Hampshire also calculates standard error of predication and 90-percent prediction intervals.

Product: Open File Report 2005-1172, The New Hampshire Watershed Tool: A Geographic Information System Tool to Estimate Streamflow Statistics and Ground-Water Recharge Rates, by Scott A. Olson, Robert H. Flynn, Craig M. Johnston, and Gary D. Tasker

This report is only available online:

ArcView window displayed when a point on a stream is selected.


Other reports related to this Tool are available online:

Flynn, R.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 WRIR 02-4298.

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 (SIR) 2004-5019.


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Page Last Modified: Wednesday, 25-Jan-2017 13:27:47 EST