Prepared in cooperation with the

New Hampshire Department of Environmental Services

The New Hampshire Watershed Tool: A Geographic

Information System Tool to Estimate Streamflow

Statistics and Ground-Water-Recharge Rates

Open-File Report 2005-1172

U.S. Department of the Interior

U.S. Geological Survey
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

In cooperation with the

New Hampshire Department of Environmental Services

Open-File Report 2005-1172

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2005

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: http://www.usgs.gov/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation: Olson, S.A., Flynn, R.H., Johnston, C.M., and Tasker, G.D., 2005, The New Hampshire Watershed 

Tool: A geographic information system tool to estimate streamflow statistics and ground-water-recharge rates: 

U.S. Geological Survey Open-File Report 2005-1172, 13 p.
iii

Contents

Abstract ................................................................................................... 1

Introduction................................................................................................ 1

Purpose and Scope ................................................................................. 1

Estimating Flow-Frequency Characteristics of Ungaged, Unregulated, Rural 

New Hampshire Streams........................................................................ 1

Regression Equations .............................................................................. 2

Using the Flow-Frequency Regression Equations ............................................. 2

Estimating Ground-Water-Recharge Rates of Drainage Basins in New Hampshire ............ 2

Regression Equations .............................................................................. 2

Using the Ground-Water-Recharge Rate Regression Equations.............................. 4

New Hampshire Watershed Tool........................................................................ 5

System Requirements .............................................................................. 5

Data Requirements ................................................................................. 5

Installation of the New Hampshire Watershed Tool .......................................... 7

Using the New Hampshire Watershed Tool...................................................... 9

Additional Utilities of New Hampshire Watershed Tool ....................................... 12

Summary ................................................................................................... 12

Selected References .................................................................................... 12

Figures

1. Flowchart showing directory structure and naming convention of the data 

files required by the New Hampshire Watershed Tool. Hydrologic unit codes 

01070001 and 01080101 are shown as examples .......................................... 6

2. Map showing available coverage in New Hampshire of National Hydrography 

Datasets (NHD) compatible with the NHD Toolkit version 7.0.0 and the New 

Hampshire Watershed Tool .................................................................. 8

3. Screenshot of an ArcView window with the New Hampshire Watershed 

Tool installed ................................................................................. 10

4. Screenshot of ArcView window displayed when a point on a stream is selected ... 11
iv

Tables

1. Regression equations for estimating flow duration and low-flow statistics for 

unregulated, ungaged, rural New Hampshire streams ................................. 3

2. Ranges of basin characteristics used in development of the regression equations 

for estimating flow duration and low-flow statistics of ungaged, unregulated 

streams in New Hampshire .................................................................. 4

3. Regression equations for estimating ground-water-recharge rates of rural 

New Hampshire drainage basins............................................................ 4

4. Ranges of basin characteristics used in development of the regression equations 

for estimating ground-water-recharge rates of rural drainage basins in New 

Hampshire .................................................................................... 5

5. Data layers the New Hampshire Watershed Tool used to compute basin 

characteristics................................................................................. 9

6. Buttons that run the functions of the New Hampshire Watershed Tool ............... 10

Conversion Factors

Multiply By To obtain

Length

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

Area

square mile (mi2) 2.590 square kilometer (km2) 

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

Pertinent Web Sites

Web Site Owner Source of Access date

http://www.cits.rncan.gc.ca Natural Resources Canada Canadian elevation datasets May 4, 2005

http://www.granit.sr.unh.edu Complex Systems Research 

Center

Topographic images of 

New Hampshire

May 4, 2005

http://nhd.usgs.gov U.S. Geological Survey National Hydrography

Dataset

May 4, 2005

http://ned.usgs.gov U.S. Geological Survey National Elevation Dataset May 5, 2005

http://nh.water.usgs.gov U.S. Geological Survey 

New Hampshire-Vermont 

Water Science Center

New Hampshire 

Watershed Tool Report

June 6, 2005

http://www.climatesource.com Climate Source PRISM Precipitation May 4, 2005

Datasets
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

Abstract

Estimates of low-flow statistics, flow durations, and 

ground-water-recharge rates are needed to assist waterresource managers in assessing surface-water resources and 

ground-water availability. Often these estimates are required at 

ungaged sites where no observed streamflow data are available 

for analysis. Regression equations for estimating low-flow 

statistics and flow durations, and for estimating groundwater-recharge rates at ungaged sites have been developed for 

New Hampshire. However, use of these equations requires 

numerous input parameters, such as basin and climatic 

characteristics. This report describes a customized geographic 

information system (GIS) application, the New Hampshire 

Watershed Tool, that automates the measurement of the 

characteristics used for input to the regression equations and 

calculates the corresponding flow statistics and ground-waterrecharge rates.

Introduction

The population of New Hampshire grew by 11.4 percent—approximately 141,000 people—from 1990 to 2000 and 

another 215,000 people are expected to live in the state by the 

year 2025 (New Hampshire State Data Center, 2001). Because 

this population growth has caused increased demands on water 

resources, improved tools are needed by water-resources managers to characterize water availability and ensure sufficient 

supply for all users—domestic, commercial, and agricultural—while maintaining aquatic habitat.

The U.S. Geological Survey (USGS), in cooperation with 

the New Hampshire Department of Environmental Services 

(NHDES), has developed regression equations for estimating 

low-flow statistics, flow durations, and ground-water recharge 

rates (Flynn, 2003; Flynn and Tasker, 2004). Equations for 

low-flow statistics include spring, summer, fall, winter, and 

annual 7-day 2-year and 7-day 10-year low flows. Equations 

for flow-duration statistics include spring, summer, fall, 

winter, and annual 60-, 70-, 80-, 90-, 95-, and 98-percent 

flow durations. 

To solve the equations accurately, consistently, and 

quickly, a computer application, the New Hampshire Watershed Tool (referred to herein as the “Tool”), was developed. 

This geographic information system (GIS) application is based 

on the National Hydrography Dataset (NHD) tools (U.S. 

Geological Survey and U.S. Environmental Protection Agency, 

2004) and automates the delineation of drainage-basin boundaries and the calculation of basin characteristics required by 

the equations. The Tool includes software that was written 

in the computer language FORTRAN to solve the regression 

equations and compute the accuracy of the results. 

Purpose and Scope

The purpose of this report is to describe development 

and use of (1) regression equations for estimating low-flowfrequency characteristics of ungaged, unregulated, rural New 

Hampshire streams; (2) regression equations for estimating 

ground-water-recharge rates of drainage basins in New Hampshire; and (3) the New Hampshire Watershed Tool.

Estimating Flow-Frequency

Characteristics of Ungaged,

Unregulated, Rural New Hampshire

Streams

The most reliable estimates of flow-frequency 

characteristics are generally obtained by frequency analysis 

of flow data from gaged streams. Estimates, however, often 

are required at stream locations where no data are available. 

To solve this problem, regression equations were developed 

for estimating low-flow statistics and flow durations at 

ungaged, unregulated streams in rural drainage basins in New 

Hampshire by relating flow-frequency characteristics to basin 

and climatic characteristics at gaged locations. Details of the 

development of the equations are discussed in Flynn (2003).
2 The New Hampshire Watershed Tool: A GIS Tool to Estimate Streamflow Statistics and Ground-Water-Recharge Rates

Regression Equations

The equations for estimating the flow-frequency characteristics were developed using generalized least squares (GLS) 

regression methods (Tasker, 1987) and the GLSNET software 

(G.D. Tasker, K.M. Flynn, A.M. Lumb, W.O. Thomas, Jr., 

U.S. Geological Survey, written commun., 1995). Tasker and 

Stedinger (1989) demonstrated that GLS regression provides 

the most appropriate results for hydrologic purposes because 

the principles of GLS allow weight to be given to each station in the analysis to compensate for differences in length of 

record and for streamflow data that are correlated spatially 

and temporally. The equations for estimating flow duration 

(daily-mean discharges exceeded a given percentage of time) 

were developed using ordinary least squares (OLS) regression 

procedures (SAS Institute Inc., 1990) because period-of-record 

flow-duration statistics lack the annual time series required by 

GLSNET software. A summary of the equations is included 

in table 1.

The average basin slope (BS) and maximum basin elevation (MxBE) were derived from the National Elevation Dataset 

(U.S. Geological Survey, 2001). The average basin slope was 

determined using the ARC/INFO SLOPE command (Environmental Systems Research Institute, Inc., 1994).

The basin characteristics that are climatic in nature, such 

as precipitation, temperature, and snow cover, were derived 

from 2-kilometer grid Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) (Daly, 2000) data. These 

grids were resampled with bilinear interpolation to a 30-metercell resolution with the ARC/INFO RESAMPLE command 

(Environmental Systems Research Institute, Inc., 1994). The 

grids representing the average winter precipitation, the mean 

annual temperature, and the summer temperature were manually extrapolated into Canada to cover portions of drainage 

basins for New Hampshire streams extending into Canada.

The coniferous and mixed coniferous-deciduous forest 

data were derived from the 1992 National Land Cover Dataset 

(NLCD) (U.S. Geological Survey, 2000). The grids were 

extended into Canada using a similar land-cover dataset available for Canada at a 25-meter resolution (Brenna Beaulieu, 

Quebec Ministry of the Environment, written commun., 2001).

Using the Flow-Frequency Regression Equations

Application of the regression equations developed to 

estimate flow-frequency characteristics is limited to sites 

on ungaged, unregulated streams in rural New Hampshire 

drainage basins and to sites with basin characteristics that are 

within the range used in the development of the equations. The 

ranges of basin characteristics used in the regression analysis 

are shown in table 2. If basin characteristics from an ungaged 

site are outside of these ranges, the accuracies of the predictions are unknown. The Tool alerts the user if basin characteristics are outside the allowable ranges. It also identifies the 

presence of dams, based on a dataset available from the U.S. 

Environmental Protection Agency (1998). Because dams may 

indicate flow regulation within the delineated drainage basin, 

users of the Tool need to assess the degree of flow regulation 

and its effect on the accuracy of estimated flows.

Basin characteristics used for developing the regression equations were determined with a GIS using datasets 

and methods explained in Flynn (2003). Application of the 

equations using basin characteristics derived by other means, 

or using data sources or methods that deviate from those 

described in this report, may introduce bias and produce 

streamflow statistics with unknown error.

The standard error of prediction and prediction intervals 

are measures of the accuracy of results obtained from the 

regression equations. These statistics are computed and output 

by the New Hampshire Watershed Tool. Users of the Tool can 

refer to the report by Flynn (2003) for a detailed explanation 

of the measures and how they are computed.

Estimating Ground-Water-Recharge

Rates of Drainage Basins in

New Hampshire

Regression equations were developed for estimating 

ground-water-recharge rates of rural drainage basins in New 

Hampshire by relating estimates of ground-water-recharge 

rates to basin and climatic characteristics of gaged basins. 

Details of the development of the equations are described in 

Flynn and Tasker (2004).

Regression Equations

The equations for estimating the ground-water-recharge 

rates were developed using generalized least squares (GLS) 

regression methods (Tasker, 1987). Ten basin characteristics 

having the most predictive power were selected as independent 

variables in the annual and seasonal equations. The equations 

are shown in table 3.

The climatic characteristics of the basin, such as precipitation, temperature, and snowcover, were derived from 

2-kilometer grid Parameter-elevation Regressions on Independent Slopes Model (PRISM) (Daly, 2000) data. These grids 

were resampled with bilinear interpolation to a 30-meter-cell 

resolution with the ARC/INFO RESAMPLE command (Environmental Systems Research Institute, Inc., 1994). The grids 

representing the average monthly mean winter temperature 

and the mean annual snowfall were manually extrapolated into 

Canada, as necessary. The mean annual precipitation grid was 

extended into Canada, as necessary, by using annual precipitation data from Canada (Ghislain Jacques, Environment 

Quebec, written commun., January 17, 2002).

The coniferous and mixed coniferous-deciduous forest 

grids were derived from the 1992 National Land Cover Dataset (NLCD) (U.S. Geological Survey, 2000). The grids were 
Estimating Flow-Frequency Characteristics of Ungaged, Unregulated, Rural New Hampshire Streams 3

Table 1. Regression equations for estimating flow duration and low-flow statistics for unregulated, ungaged, rural New Hampshire 

streams.

[Statistic, Pwinxx, Psprxx, Psumxx, Pfallxx are the xx-percent duration flows for winter (win), spring (spr), summer (sum), and fall (fall), respectively; Pporxx 

is the xx-percent duration flow for the period-of-record (por); 7Qt, 7-day, t-year or season low flow. All flows are in cubic feet per second (ft3/s); *, multiply by; 

BCF, Bias correction factor; DA, drainage area, in square miles; BS, average basin slope, in percent; MxBE, maximum basin elevation, in feet; The following 

basin characteristics were derived from 2-kilometer grid Parameter-elevation Regressions on Independent Slopes Model (PRISM) (Daly, 2000) data from 1961 

to 1990 resampled with bilinear interpolation to a 30-meter-cell resolution: ABT, basinwide mean of the average mean annual temperature, in degrees Fahrenheit; SBT, basinwide mean of the average monthly mean temperature during the summer (June 1 to October 31), in degrees Fahrenheit; SGP, average total summer precipitation (June 1 to October 31) at basin-outlet point, in inches; WCP, average total winter precipitation (January 1 to March 15) at the basin centroid, 

in inches; SpGP, average total spring precipitation (March 16 to May 31) at basin-outlet point, in inches. The following basin characteristics were derived from 

the 1992 National Land Cover Data Set (NLCD) (U.S. Geological Survey, 2000): C, percent of basin covered by coniferous forest, in percent; CD, percent of 

basin covered by mixed coniferous and deciduous forest, in percent]

Statistic BCF Regression equation

Flow duration

Pwin60 =

Pwin70 =

Pwin80 =

Pwin90 =

Pwin95 =

1.01935

1.01824

1.01431

1.01631

1.01942

* 10-0.74691 * (DA)1.05501 * (C)-0.31447 * (WCP)1.04311

* 10-0.85475 * (DA)1.06248 * (C)-0.32065 * (WCP)1.085

* 10-0.88606 * (DA)1.0528 * (C)-0.28824 * (WCP)1.00598

* 10-1.04824 * (DA)1.06566 * (C)-0.23842 * (WCP)0.9677

* 10-1.17324 * (DA)1.06732 * (C)-0.21459 * (WCP)0.95736

Pwin98 =

Pspr60 =

Pspr70 =

Pspr80 =

Pspr90 =

1.03264

1.00679

1.00596

1.00668

1.00811

* 10-1.22564 * (DA)1.05571 * (C)-0.15768 * (WCP)0.83447

* 100.000678 * (DA)1.01298 * (BS)0.31101

* 10-0.0748 * (DA)1.01608 * (BS)0.28206

* 10-0.0203 * (DA)1.01729 * (BS)0.23293 * (CD)-0.08555

* 10-0.04102 * (DA)1.01595 * (BS)0.15284 * (CD)-0.11743

Pspr95 =

Pspr98 =

Psum60 =

Psum70 =

Psum80 =

1.00936

1.01373

1.05101

1.06039

1.07543

* 10-0.0632 * (DA)1.01597 * (BS)0.099718 * (CD)-0.15498

* 10-0.10609 * (DA)1.02007 * (BS)0.11425 * (CD)-0.24025

* 1011.8078 * (DA)1.18298 * (SBT)-9.04402 * (C)-0.1922 * (SGP)2.86063

* 1014.0257 * (DA)1.19901 * (SBT)-10.3043 * (C)-0.20291 * (SGP)2.77037

* 1014.0788 * (DA)1.2123 * (SBT)-10.5568 * (SGP)2.76521

Psum90 =

Psum95 =

Psum98 =

Pfall60 =

Pfall70 =

1.09816

1.12433

1.13959

1.02332

1.02860

* 1017.8757 * (DA)1.2409 * (SBT)-12.691 * (SGP)2.58347

* 1019.5562 * (DA)1.28282 * (SBT)-13.8734 * (SGP)2.7607

* 1024.8367 * (DA)1.25479 * (SBT)-16.1965 * (SGP)1.78959

* 10-0.70158 * (DA)0.94819 * (MxBE)0.24926 * (C)-0.08028

* 10-1.02695 * (DA)0.95106 * (MxBE)0.32968 * (C)-0.12032 

Pfall80 =

Pfall90 =

Pfall95 =

Pfall98 =

Ppor60 =

1.03285

1.04291

1.06287

1.10999

1.01422

* 10-1.43202 * (DA)0.94519 * (MxBE)0.4377 * (C)-0.16618

* 10-1.90346 * (DA)0.95483 * (MxBE)0.54551 * (C)-0.21994

* 10-2.34912 * (DA)0.98509 * (MxBE)0.63994 * (C)-0.26681

* 10-2.93315 * (DA)1.02072 * (MxBE)0.76078 * (C)-0.29871

* 10-3.53416 * (DA)1.08542 * (SGP)2.54435

Ppor70 =

Ppor80 =

Ppor90 =

Ppor95 =

Ppor98 =

1.01800

1.03216

1.05674

1.07750

1.11561

* 10-1.65947 * (DA)1.09815 * (ABT)-1.29046 * (SGP)2.59298

* 100.14014 * (DA)1.14248 * (ABT)-2.7358 * (SGP)2.83256

* 102.94244 * (DA)1.19434 * (ABT)-4.72162 * (SGP)2.92621

* 105.05371 * (DA)1.23203 * (ABT)-6.13047 * (SGP)2.89144

* 106.24458 * (DA)1.28081 * (ABT)-7.19399 * (SGP)3.13133

7Q2 win =

7Q10 win =

7Q2 spr =

7Q10 spr =

7Q2 sum =

1.01469

1.02279

1.01039

1.01307

1.14416

Low-Flow Frequency 

* 10-0.86255 * (DA)1.05538 * (C)-0.22494 * (WCP)0.88402

* 10-1.24495 * (DA)1.08506 * (C)-0.20848 * (WCP)0.9756

* 10-0.93746 * (DA)1.04219 * (SpGP)0.93329 * (C)-0.12319

* 10-1.35488 * (DA)1.06065 * (SpGP)1.08213 * (C)-0.12298

* 1014.00639 * (DA)1.22668 * (SBT)-10.70843 * (SGP)2.88837

7Q10 sum =

7Q2 fal =

7Q10 fal =

7Q2 yr =

7Q10 yr =

1.27148

1.02686

1.06484

1.14477

1.27688

* 1018.56974 * (DA)1.36816 * (SBT)-14.06792 * (SGP)3.55322

* 10-1.3758 * (DA)0.96049 * (MxBE)0.39654 * (C)-0.12046

* 10-2.55435 * (DA)0.97395 * (MxBE)0.68011 * (C)-0.22167

* 103.77893 * (DA)1.24597 * (ABT)-5.77815 * (SGP)3.39819

* 105.33462 * (DA)1.39481 * (ABT)-7.67405 * (SGP)4.16826
4 The New Hampshire Watershed Tool: A GIS Tool to Estimate Streamflow Statistics and Ground-Water-Recharge Rates

Table 2. Ranges of basin characteristics used in development of the regression equations for estimating flow duration 

and low-flow statistics of ungaged, unregulated streams in New Hampshire.

Basin characteristic Abbreviation Minimum Mean Maximum

Drainage area (square miles) DA 3.26 97.2 689

Average basin slope (percent) BS 3.19 16.5 38.1

Maximum basin elevation (feet) MxBE 260 3,120 6,290

Average summer gage precipitation (inches) SGP 16.5 18.7 23.1

Average spring gage precipitation (inches) SpGP 6.83 8.85 11.5

Average winter basin centroid precipitation (inches) WCP 5.79 7.96 15.1

Average mean annual basin temperature (degrees Fahrenheit) ABT 36.0 42.3 48.7

Average mean summer basin temperature (degrees Fahrenheit) SBT 52.9 58.7 64.4

Percent coniferous forest (percent) C 3.07 20.9 56.2

Percent mixed coniferous-deciduous forest (percent) CD 6.21 26.6 46.1

extended into Canada using a similar land-cover dataset avail- Hampshire Watershed Tool alerts the user if basin characterisable for Canada at a 25-meter resolution (Brenna Beaulieu, tics are outside the allowable ranges.

Quebec Ministry of the Environment, written commun., 2001). Basin characteristics used for developing the regression 

equations were determined with a GIS using datasets and 

Using the Ground-Water-Recharge Rate

methods explained in Flynn and Tasker (2004). Application 

of the equations using basin characteristics derived by other 

Regression Equations means, or using data sources or methods that deviate from 

those described in this report, may introduce bias and produce 

Application of the regression equations is limited to rural ground-water-recharge-rate estimates with unknown error.

New Hampshire drainage basins with basin characteristics The standard error of prediction and prediction intervals 

that are within the range of those used in the development of are measures of the accuracy of results obtained from the 

the equations. The ranges of basin characteristics used in the regression equations. These statistics are computed and output 

regression analysis are shown in table 4. If the equations are by the New Hampshire Watershed Tool. Users of the Tool can 

applied to basins with characteristics outside of these ranges, refer to the report by Flynn and Tasker (2004) for a detailed 

the accuracies of the predictions are unknown. The New explanation of the measures and how they are computed.

Table 3. Regression equations for estimating ground-water-recharge rates of rural New Hampshire drainage 

basins.

[All recharge results are in inches per season or year. The following basin characteristics were derived from 2-kilometer grid Parameter-elevation Regressions on Independent Slopes Model (PRISM) (Daly, 2000) data from 1961 to 1990 resampled with bilinear interpolation to a 30-meter-cell resolution: AGP, average annual precipitation at basin-outlet point of basin, in inches; WBT, basinwide 

mean of the minimum monthly mean temperature during the winter (January 1 to March 31), in degrees Fahrenheit; SpGP, average 

total spring precipitation (March 16 to May 31) at basin-outlet point, in inches; ASC, basinwide average of the mean annual snowfall, 

in inches; SPG, average total summer precipitation (June 1 to October 31) at basin-outlet point, in inches; ABT, basinwide mean of the 

average mean annual temperature, in degrees Fahrenheit; FCP, average total fall precipitation (November 1 to December 31) at basin 

centroid, in inches; ACP, average annual precipitation at the basin centroid, in inches. The following basin characteristics were derived 

from the 1992 National Land Cover Data Set (NLCD) (U.S. Geological Survey, 2000): C, percent of basin containing coniferous forest, in percent; and CD, percent of drainage basin containing mixed coniferous and deciduous forest, in percent]

Ground-waterrecharge-rate period Regression equation

Winter -3.485 + 0.160(AGP) + 0.168(WBT) - 0.041(C)

Spring -1.544 + 0.721(SpGP) + 0.045(ASC) - 0.032(C)

Summer 3.725 + 0.573(SGP) - 0.223(ABT) - 0.039(CD)

Fall 0.389 + 0.499(FCP) - 0.049(C)

Annual -1.932 + 0.589(ACP) - 0.176(C)
New Hampshire Watershed Tool 5

Table 4. Ranges of basin characteristics used in development of the regression equations for estimating ground-waterrecharge rates of rural drainage basins in New Hampshire.

Basin characteristic Abbreviation Minimum Mean Maximum

Average annual gage precipitation (inches) AGP 35.83 42.93 53.11

Average summer gage precipitation (inches) SGP 16.46 18.60 23.11

Average spring gage precipitation (inches) SpGP 6.83 8.85 11.54

Average annual basin-centroid precipitation (inches) ACP 37.44 45.32 75.91

Average mean annual basin temperature (degrees Fahrenheit) ABT 36.05 42.35 48.69

Average minimum winter basin temperature (degrees Fahrenheit) WBT 0.8 10.61 19.88

Percent coniferous forest (percent) C 3.07 20.65 56.18

Percent mixed coniferous-deciduous forest (percent) CD 6.21 26.05 46.13

Average fall basin-centroid precipitation (inches) FCP 6.57 8.38 15.20

Average annual snowcover (inches) ASC 54.46 102.41 219.07

New Hampshire Watershed Tool

A GIS application, the New Hampshire Watershed Tool, 

was developed to determine the basin characteristics required 

by the equations for estimating low-flow frequencies, flow 

durations, and ground-water-recharge rates for basins in 

New Hampshire. This application allows the user to interactively select a point on a stream of interest. The Tool 

automatically delineates the upstream drainage area, quantifies 

the required basin characteristics, solves the regression 

equations, and calculates the standard error of prediction and 

prediction intervals.

The Tool was developed in the Environmental Systems 

Research Institute, Inc. (ESRI) ArcView version 3.2 software 

(1996a) using ESRI Avenue programming language (Environmental Systems Research Institute, Inc., 1996b) and was converted to an ESRI ArcView extension. Extensions are plug-in 

programs that can be easily loaded into ArcView or unloaded 

as needed. The drainage-basin delineation is based on the 

NHD and the NHD Toolkit (U.S. Geological Survey and U.S. 

Environmental Protection Agency, 2004) and uses drainage-boundary delineation concepts from the NHD Watershed 

extension (J.R. Hill, Horizon Systems Corporation, and P.A. 

Steeves, U.S. Geological Survey, written commun., 2001).

System Requirements

The New Hampshire Watershed Tool requires the following software and toolkits:

1. ESRI ArcView version 3.2 or 3.3;

2. The ESRI ArcView 3.x Spatial Analyst (version 2) 

extension; and

3. The NHD Toolkit, version 7.0.0 (U.S. Geological Survey 

and U.S. Environmental Protection Agency, 2004).

The NHD Toolkit is available for download from the 

NHD website, http://nhd.usgs.gov/. The NHD Toolkit contains 

a suite of extensions, some of which are used to process 

NHD data and others that are required for execution of the 

New Hampshire Watershed Tool.

The computer and operating system requirements for 

the Tool are defined by the ESRI ArcView software. The Tool 

successfully runs in Microsoft Windows98, NT, 2000, and 

XP. Other operating systems have not been tested. Notepad, a 

program for viewing text files commonly packaged with the 

Microsoft Windows operating system, is required. Required 

disk space for the entire suite of topographic map images, 

NHD data, and other supporting datasets for computing basin 

characteristics for the entire State of New Hampshire is estimated to be 5 to 6 gigabytes. Data such as the NHD and the 

topographic map images, however, can be installed in different 

locations on a local network. One gigabyte of virtual memory 

is required for delineating the full range of drainage-basin 

sizes in New Hampshire.

Data Requirements

The New Hampshire Watershed Tool requires 5 to 6 

gigabytes of data to work statewide. Furthermore, for the Tool 

to function properly, the data directory must be structured 

and use the naming convention shown in figure 1. For each 

hydrologic unit, there are two directories whose names begin 

with the hydrologic unit code and end in either “_24shp” 

or “_ws.” The folder with the “_24shp” suffix contains the 

1:24,000-scale NHD for New Hampshire projected into 

the New Hampshire State Plane coordinate system and 

converted to the ESRI ArcView shapefile format using the 

NHD Arc2shape extension. The naming conventions of the 

subdirectories in the “_24shp” directory are generic to the 

NHD and are explained in the help files of NHD extensions. 

The NHD for New Hampshire, and the processing instructions, 
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6 The New Hampshire Watershed Tool: A GIS Tool to Estimate Streamflow Statistics and Ground-Water-Recharge Rates

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Figure 1. Directory structure and naming convention of the data files required by the New Hampshire 

Watershed Tool. Hydrologic unit codes 01070001 and 01080101 are shown as examples.
7

can be downloaded from the NHD Web site, http://nhd.usgs.

gov/. In 2005, the NHD, in the format required by the NHD 

Toolkit version 7.0.0, was available in 5 of the 16 hydrologic 

units in New Hampshire (fig. 2). Automatic delineation of 

drainage boundaries by the New Hampshire Watershed Tool 

is not possible outside of the regions with NHD coverage. 

A function allowing the user to enter a predetermined basin 

boundary in any part of the state is discussed later in this 

report, and can be used to apply the Tool in regions where 

NHD coverage is unavailable.

The folders with the “_ws” suffix (fig. 1) contain the 

NHD WATershed SUPport (WATSUP) datasets required for 

delineating a drainage basin for any selected point along a 

NHD reach. Detailed instructions for processing the data in 

the “_ws” folders to prepare them for use with the New Hampshire Watershed Tool can be obtained from the Applications 

section of the NHD Web site, http://nhd.usgs.gov/watershed/

watershed_tool_inst_TOC.html (Steeves, 2002).

The WATSUP datasets in the “_ws” folder include 

the flow accumulation grid, “accum”; the flow direction 

grid, “dir_grd”; and a polygon coverage of drainage-basin 

catchments for each stream reach in the NHD, “shed_cov.” 

These WATSUP datasets are derived from the National 

Elevation Dataset (NED) (U.S. Geological Survey, 2001) or 

higher resolution U.S. Geological Survey 10-meter Digital 

Elevation Models (DEMs) (U.S. Geological Survey, 2004), 

where available.

 The first step in developing the WATSUP datasets 

involves adjusting the elevation datasets for the hydrologic 

conditions observed in the NHD (Saunders, 2000). The 

ARC/INFO command TOPOGRID (Environmental Systems 

Research Institute, Inc., 1994) and the ARC/INFO script, 

“agree.aml,” (Hellweger and Maidment, 1997) are applied 

to the elevation datasets to produce an elevation grid with a 

10-meter cell size that is hydrologically correct and horizontally matches the NHD network. Next, basin boundaries taken 

from the Natural Resources Conservation Service (NRCS) 

12-digit Watershed Boundary Dataset (WBD) (Natural 

Resources Conservation Service, 2004) are utilized to enforce 

agreement of the elevation grid with these boundaries.

The modified DEM, which now has horizontal agreement 

with the NHD and the WBD, undergoes one last hydrologic 

conditioning process using the ARC/INFO GRID command 

FILL. FILL identifies and removes isolated elevation sinks 

and insures proper surface drainage for all elevation cells. 

The ARC/INFO GRID commands FLOWDIRECTION 

and FLOWACCUMULATION are then used to create the 

flow-direction and flow-accumulation grids, “dir_grd” and 

“accum,” respectively, using the hydrologically conditioned 

DEM as input.

A watershed catchment coverage is then created using the 

ARC/INFO GRID command WATERSHED with the flowdirection grid and a rasterized representation of the stream network as input. The ARC/INFO GRID command GRIDPOLY 

is used to convert the output grid from the WATERSHED 

command to the polygon coverage “shed_cov.” Each polygon 

New Hampshire Watershed Tool

is then attributed with a code corresponding to the reach code 

of the NHD reach that intersects the polygon. 

The final dataset in the “_ws” folder is a copy of the 

NHD-reach route system in ESRI shapefile format that is 

put into a folder named “dendrite.” The shapefile is named 

“dendrite” also. It can be edited and reaches can be removed 

from the dendrite shapefile for purposes of preventing a user 

from selecting a reach where the regression equations are not 

applicable. Artificial channels and diversions are examples of 

channels that could be removed from the dendrite shapefile. 

The creation of the dendrite dataset is further explained in the 

instructions for processing the WATSUP dataset, http://nhd.

usgs.gov/watershed/watershed_tool_inst_TOC.html.

The “nh_ff” folder (fig. 1) contains the data for computing basin and climatic characteristics. There are 12 grid datasets projected into New Hampshire State Plane coordinates in 

the folder. A brief description and the source for each of these 

grids is listed in table 5. 

The “Utilities” folder contains some of the basic geographic features, such as roads and basin, town, and county 

boundaries, which are displayed by the New Hampshire 

Watershed Tool to assist the user in locating stream reaches of 

interest. This folder also stores the point coverage “nhdams” 

and the shapefile, “huc8.shp,” which are used by the Tool 

to check for potential upstream flow regulation and to load 

hydrologic unit data, respectively. The programs “pdur.

exe” and “recharge.exe” and datasets for solving the regression equations and analyzing the prediction intervals also 

are located in this directory. Each user of the Tool must have 

a copy of the utilities directory on their own workstation 

because this directory is used as a temporary workspace for 

saving files created during intermediate computation steps..

The final dataset used by the Tool is the USGS topographic map images in electronic format at 1:24,000 scale. 

These maps are known also as Digital Raster Graphics (DRG). 

The images simplify the process of accurately locating 

streams. The DRGs can be obtained from the New Hampshire 

Geographically Referenced Analysis and Information Transfer 

System (NH GRANIT) at http://www.granit.sr.unh.edu/.

Installation of the New Hampshire Watershed

Tool

Once the required ESRI software and NHD toolkit have 

been installed, the datasets and utilities have been loaded 

in the appropriate directory structure, and the New Hampshire Watershed Tool extension has been copied to the ESRI 

ArcView extensions directory, the Tool is ready for use. To 

load the Tool extension into ArcView, select the “File” menu 

in the ArcView window and select “Extensions.” A window of 

available extensions will open. Load the extension by clicking 

the box to the left of “NH Watershed Tool.”

After the New Hampshire Watershed Tool extension 

is loaded, a menu named “NHSETUP” will appear in the 

ArcView application window when the project window is 
8 The New Hampshire Watershed Tool: A GIS Tool to Estimate Streamflow Statistics and Ground-Water-Recharge Rates

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Figure 2. Available coverage in New Hampshire of National Hydrography Datasets (NHD) compatible with the NHD Toolkit version 7.0.0 and the New Hampshire Watershed Tool.

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New Hampshire Watershed Tool 9

Table 5. Data layers the New Hampshire Watershed Tool used to compute basin characteristics.

[NED, National Elevaiton Dataset (U.S. Geological Survey, 2001); NLCD, National Land Cover Dataset of 1992 

(U.S. Geological Survey, 2000); PRISM, Parameter-elevation Regressions on Independent Slopes Model data from 

1961 to 1990 (Daly, 2000)]

Name of 

data layer Description Source

Dem_grid Digital Elevation Model NED

Fall_precip Average total fall precipitation (November 1 to December 31) PRISM

Precip_ann Mean annual precipitation PRISM

Snow_ann Mean annual snowfall PRISM

Spr_precip Average total spring precipitation (March 16 to May 31) PRISM

Sum_precip Average total summer precipitation (June 1 to October 31) PRISM

Sum_temp Average monthly mean temperature in summer (June 1 to October 31) PRISM

Tmean_ann Average annual mean temperature PRISM

Win_precip Average total winter precipitation (January 1 to March 15) PRISM

Win_tmin Average monthly minimum temperature in winter (January 1 to March 31) PRISM

Conif Coniferous forest NLCD

Mix_4est Mixed coniferous and deciduous forest NLCD

active. This setup routine should be executed when the extension is first loaded into each new ESRI ArcView project file to 

identify the locations of required data and the utilities folder 

and to create the map of New Hampshire in the view window. 

Once the setup routine is run, it will not be needed again in the 

ESRI ArcView project file and the “NHSETUP” menu will 

disappear. Saving and using only this project file will eliminate the need to run the setup routine again.

The setup routine first prompts the user for the location 

of the utilities folder. The user must browse for the “utilitieslocation.txt” file located in the user’s utilities directory. The 

location of the data folders is requested in a similar manner, 

and the user must browse for the “datalocation.txt” file 

(fig. 1) located in the directory that contains the data folders. 

The location of the topographic map database file (topo.dbf) 

also is requested; however, these data are not required and the 

search for this file can be canceled. When the setup for the 

New Hampshire Watershed Tool is complete, the routine then 

opens a window displaying a map of New Hampshire. The 

Tool menu (“NHWT_Options”) and buttons are now displayed 

in the ESRI ArcView menubar and toolbar, respectively. The 

ESRI ArcView window may need to be enlarged to display the 

entire menubar and toolbar. An example of an ESRI ArcView 

project window with the Tool loaded and installed is shown in 

figure 3.

Using the New Hampshire Watershed Tool

This section of the report includes instructions for using 

the New Hampshire Watershed Tool. To be successful, the user 

must be familiar with the basic functions of ESRI ArcView, 

such as panning and zooming, making themes active, interactively identifying features, and turning the display themes on 

and off.

With the setup complete, the Tool is ready for use. There 

are four buttons on the toolbar that run the major functions 

of the Tool. These buttons are displayed in table 6. The first 

button, the “Load Hydrologic Unit” button , is used to load 

the appropriate hydrography data and link to the appropriate 

support files for computing basin characteristics before a basin 

can be delineated. With the “Load Hydrologic Unit” button 

depressed, the cursor is used to select the hydrologic unit 

where the stream of interest is located. The hydrologic unit 

boundaries are outlined in gray by default (fig. 3). Automatic 

delineation of drainage boundaries by the Tool is not possible 

outside the regions with NHD coverage. A function allowing 

the user to enter a predetermined basin boundary in any part 

of the state and obtain low-flow-frequency or ground-waterrecharge-rate results is discussed later in this report.

With a hydrologic unit selected, the “Low-Flow 

Estimator” or “Ground-Water-Recharge-Rate Estimator” 

button can be depressed and a point on a stream selected. 

For a point to be selected on a stream, the “HUC_24shp 

– Reach” theme, where HUC is the hydrologic unit code, 
10 The New Hampshire Watershed Tool: A GIS Tool to Estimate Streamflow Statistics and Ground-Water-Recharge Rates

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Figure 3. Screenshot of an ArcView window with the New Hampshire Watershed Tool installed.

Table 6. Buttons that run the functions of the New Hampshire Watershed Tool.

[Buttons are shown in figures 3 and 4; NHD, National Hydrography Dataset]

Button Name Function

Load Hydrologic Unit

Low-Flow Estimator

Ground-Water-RechargeRate Estimator

Delineate with FlowDirection Grid

Loads NHD data and locates support data sets for the hydrologic unit interactively selected.

Delineates a drainage basin by use of NHD for a selected point on a stream, computes the basin 

characteristics, and solves the flow duration and low-flow frequency regression equations.

Delineates a drainage basin by use of NHD for a selected point on a stream, computes the basin 

characteristics, and solves the ground-water-recharge-rate regression equations.

Delineates a drainage basin by use of the flow direction and accumulation grids for a point 

interactively selected, computes the basin characteristics, and solves the selected regression 

equations.
New Hampshire Watershed Tool 11

must be active. The basin above this point is automatically 

delineated implementing the functionality of the NHD. The 

basin characteristics upstream of this point and the estimated 

flow-frequency or ground-water-recharge-rate data are then 

automatically computed and displayed as shown in the 

example in figure 4. The tabular results are displayed and 

can be saved to disk using Notepad. Before displaying lowflow-frequency results, the Tool identifies the presence of 

dams within the delineated drainage basin based on a dataset 

available from the U.S. Environmental Protection Agency 

(1998). It is the responsibility of the user to assess the degree 

of flow regulation that may exist as a result of any dam, 

including dams that may not be identified in the dam dataset, 

and to evaluate whether flows are sufficiently unregulated to 

ensure results from the Tool are valid.

The “Delineate with Flow Direction Grid” tool functions 

similarly to the “Low-Flow Estimator” and “Ground-Water 

Recharge-Rate Estimator” tool, but with several important differences. First, the basin delineation is done with flow-direction and flow-accumulation grids. A flow-direction grid is a 

grid in which each cell contains information on the direction 

of flow at that cell. This directional information can be used 

to compute a flow-accumulation grid—a grid in which each 

cell is assigned a value equal to the number of cells that flow 

into it. Basin delineation with these grids takes more time and 

computer resources than basin delineation using the NHD 

approach. Attempting to delineate large basins, such as those 

greater than a few hundred square miles, with the “Delineate 

with Flow Direction Grid” tool may exceed the capabilities 

of a personal computer. A second difference is that the user is 

prompted to select between estimates for flow-frequency or 

ground-water-recharge rates when the “Delineate with Flow 

Direction Grid” tool button is pressed. The user’s selection remains in effect until the “Delineate with Flow Direction 

Grid” tool button is pressed again. Selecting the hydrologic unit previous to the delineation is not required.

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Figure 4. ArcView window displayed when a point on a stream is selected.
12 The New Hampshire Watershed Tool: A GIS Tool to Estimate Streamflow Statistics and Ground-Water-Recharge Rates

Two technical difficulties have been identified in the 

Tool. The first is related to braided streams. Users should 

review the boundary where it crosses the braided reach and 

confirm that the Tool delineated this part of the boundary correctly. It is best to avoid a braided reach by selecting a point 

of interest either upstream or downstream of the braid. The 

second problem can occur if the point chosen for delineation is 

at a confluence. For example, if a drainage basin above a confluence is of interest and the point selected is too close to the 

confluence, both catchments related to the reaches entering the 

confluence may be delineated; however, only the headwater 

catchments above the reach that the selected point is on will be 

included in the total drainage area. To avoid the problem, the 

Tool requires selected points to be farther than 100 feet (in the 

display’s scale) upstream or downstream from the confluence.

Additional Utilities of New Hampshire

Watershed Tool

Additional utilities are provided in the New Hampshire 

Watershed Tool. These include features such as computing 

flow-frequency or ground-water-recharge-rate estimates for a 

user-provided polygon that defines a drainage area of interest, locating streams by name, and displaying flow-frequency 

statistics at USGS stream-gaging stations.

A menu on the ESRI ArcView menubar titled “NHWT_

Options” is visible when the Tool extension is loaded. This 

menu has nine selections. The first two are the “Select Utilities 

Location” and “Select Data Location” menu options. These 

can be used if datasets or the utilities folder are moved and 

the user does not want to run the setup routines again. When 

one of these options is selected, the user must browse for the 

respective “utilitieslocation.txt” or “datalocation.txt file,” as 

described in the previous section “Installation of the New 

Hampshire Watershed Tool.”

Two other options under the “NHWT_Options” menu 

are used to locate features and move around on the displayed 

map of New Hampshire. The “Zoom to New Hampshire Map” 

option zooms in or out so that the window displays the entire 

State of New Hampshire. The “Locate Stream by Name” 

option opens a window listing all the names of the streams in 

the currently loaded hydrologic unit. Once the user selects a 

stream, the map display zooms to that stream. Another option, 

“Watershed display properties,” allows the user to toggle the 

display of the watershed polygon from shaded to unshaded for 

subsequent drainage-basin delineations. The option “Display 

Gage Information” provides streamflow statistics for selected 

stream-gaging stations that were originally used to develop the 

flow-estimating equations. The station must first be selected 

with the ESRI ArcView Selection tool.

The option “Compute with User Polygon” computes the 

basin characteristics and estimated flow-frequency characteristics of a basin polygon that is provided by the user. To use 

this option, the user must first load a polygon into the view 

window. After selecting the “Compute with User Polygon” 

option, the user will be prompted for the name of the polygon 

representing the basin of interest and for the pour point or outlet of the basin polygon. If the user does not enter a pour point 

coverage or shapefile, the Tool will estimate a pour point if the 

NHD at the pour point location has been loaded into the view 

window using the “Load Hydrologic Unit” button . The 

“Compute with User Polygon” option is useful if the basin 

boundary delineated by the Tool requires manual editing, or is 

in hydrologic units where the NHD does not exist to support 

automated basin boundary delineation.

A menu item called “Clean Workspace” deletes many of 

the temporary work files that are left in the utilities directory. 

This option, however, does not delete files from the default 

ArcView Temp directory. A menu item called “About” provides a short explanation of the New Hampshire Watershed 

Tool.

Summary

This report describes a tool that has been developed by 

the U.S. Geological Survey, in cooperation with the New 

Hampshire Department of Environmental Services, for applying regression equations that estimate (1) seasonal and annual 

7-day low-flow frequency for recurrence intervals of 2 and 

10 years; (2) seasonal and annual flow duration for daily 

discharges exceeded 60, 70, 80, 90, 95, and 98 percent of 

the time; and (3) seasonal and annual ground-water-recharge 

rates. The customized geographic information system (GIS) 

application, the New Hampshire Watershed Tool, is based on 

the National Hydrography Dataset toolkit. The Tool automates 

the delineation of basin boundaries, derives values of basin 

characteristics included as independent variables in a series 

of regression equations, and solves the regression equations, 

significantly reducing the manual processing time normally 

required.

Selected References

Daly, Christopher, 2000, PRISM (Parameter-elevation Regressions on Independent Slopes Model) 1961–1990 datasets: 

U.S. Department of Agriculture and Natural Resources Conservation Service Climate Mapping Project: National Water 

and Climate Center, Oregon State University Partnership.

Environmental Systems Research Institute, Inc. (ESRI), 1994, 

ARC/INFO users guides, version 7: Redlands, Calif.

Environmental Systems Research Institute, Inc. (ESRI), 

1996a, ArcView GIS: The geographic information system 

for everyone: Redlands, Calif., 350 p.
13

Environmental Systems Research Institute, Inc. (ESRI), 

1996b, Avenue: Customization and application development 

for ArcView: Redlands, Calif., 259 p.

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 WaterResources Investigations Report 02-4298, 66 p.

Flynn, R.H., and Tasker, G.D., 2004, Generalized estimates 

from streamflow data of annual and seasonal ground-waterrecharge rates for drainage basins in New Hampshire: 

U.S. Geological Survey Scientific Investigations Report 

2004-5019, 61 p.

Hellweger, F., and Maidment, D.R., 1997, AGREE-DEM 

Surface reconditioning system, accessed October 21, 2004, 

at http://www.crwr.utexas.edu/gis/gishyd98/quality/agree/

agree.htm.

Natural Resources Conservation Service, 2004, Watershed 

boundary dataset (WBD), accessed May 5, 2004, at 

http://www.ncgc.nrcs.usda.gov/branch/gdb/products/

watershed/index.html.

New Hampshire State Data Center, 2001, Population dataset, 

accessed April 17, 2002, at URL http://www.state.nh.us/osp/

sdc/sdc.html.

Saunders, William, 2000, Preparation of DEMs for use in 

environmental modeling analysis, in Maidment, D.R., and 

Djokic, Dean [eds.], 2000, Hydrologic and hydraulic modeling support with geographic information systems: Redlands, 

Calif., Environmental Systems Research Institute, Inc., 

p. 29–51. 

Selected References

SAS Institute, Inc., 1990, SAS/STAT User’s guide (vers. 6, 

4th ed.): Cary, N.C., v. 1 and v. 2, 1,686 p.

Steeves, P.A., 2002, NHD Applications: NHD Watershed, 

accessed September 2002, at http://nhd.usgs.gov/

applications.html#nhdwatershed.

Tasker, G.D., 1987, Theory and application of generalized 

least squares, in Medina, K.D., Analysis of surface-water 

data network in Kansas for effectiveness in providing 

regional streamflow information: U.S. Geological Survey 

Water-Supply Paper 2303, p. 24–26.

Tasker, G.D., and Stedinger, J.R., 1989, An operational GLS 

model for hydrologic regression: Journal of Hydrology, 

v. 3, p. 361–375.

U.S. Environmental Protection Agency, 1998, National inventory of dams in BASINS, accessed January 25, 2005, at 

http://www.epa.gov/ost/basins/metadata/dams.htm.

U.S. Geological Survey, 2000, National land cover dataset: 

U.S. Geological Survey Fact Sheet 108-00, accessed 

August 28, 2001, at http://mac.usgs.gov/mac/isb/pubs/

factsheets/fs10800.html.

U.S. Geological Survey, 2001, National elevation dataset, 

accessed May 5, 2004, at http://edcnts12.cr.usgs.gov/ned/.

U.S. Geological Survey, 2004, Digital Elevation Models 

(DEMs), accessed October 26, 2004, at 

http://edc.usgs.gov/products/elevation/dem.html.

U.S. Geological Survey and U.S. Environmental Protection 

Agency, 2004, National hydrography dataset, accessed 

May 5, 2004, at http://nhd.usgs.gov/.
Prepared by the USGS New Hampshire-Vermont Water Science

Center Publications Unit—Debra H. Foster, Anita Cotton, and

Ann Marie Squillacci

For more information concerning the research in this report, contact:

Brian Mrazik, Director,

U.S. Geological Survey

NH-VT Water Science Center

361 Commerce Way

Pembroke, NH 03275

dc_nh@usgs.gov

or visit our Web site at:

http://nh.water.usgs.gov
Olson, S.A., Flynn, R.H., Johnston, C.M., and Tasker, G.D.—The New Hampshire Watershed Tool: A Geographic Information System Tool to Estimate Streamflow 

Statistics and Ground-Water-Recharge Rates—Open File Report 2005-1172