Comparison of Methods for Determining 

Streamflow Requirements for Aquatic 

Habitat Protection at Selected Sites on the 

Assabet and Charles Rivers, Eastern 

Massachusetts, 2000–02

By Gene W. Parker, David S. Armstrong (U.S. Geological Survey), and 

Todd A. Richards (Massachusetts Division of Fisheries and Wildlife)

In cooperation with the

Massachusetts Executive Office of Environmental Affairs, Department of Conservation and 

Recreation, Town of Hudson, and Massachusetts Division of Fisheries and Wildlife

Scientific Investigations Report 2004-5092

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: 2004

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

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:

Parker, G.W., Armstrong, D.S., and Richards, T.A., 2004, Comparison of methods for determining streamflow 

requirements for aquatic habitat protection at selected sites on the Assabet and Charles Rivers, Eastern Massachusetts, 

2000–02: U.S. Geological Survey Scientific Investigations Report 2004-5092, 72 p.
 iii

Contents

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

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Description of Study Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Methods for Determining Streamflow Requirements for Aquatic Habitat Protection. . . . . . . . . . . . . . . . 4

Water-Surface-Profile Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

R2Cross Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Wetted-Perimeter Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Range of Variability Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Tennant Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Streamflow Requirements for Aquatic Habitat Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Assabet River near Westborough . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Cold Harbor Brook near Northborough . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Danforth Brook at Hudson . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Fort Meadow Brook near Hudson . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Elizabeth Brook near Stow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Nashoba Brook at West Concord . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Charles River near Hopkinton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Mine Brook near Franklin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Charles River at Medway. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Fish-Community Sampling and Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Sampling Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Assabet River Basin Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Charles River Basin Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Fish-Community Assessments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Comparison of Streamflow Requirement Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

References Cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Appendix 1: Water-Surface-Profile Model Documentation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Figures

1, 2. Maps showing:

1. Location of major river basins in Massachusetts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

2. Location of study sites and six streamflow-gaging stations near the Charles 

and Assabet River Basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

3. Photographs showing A, Riffle and B, pooled reaches on the Charles River at 

Medway, on August 1, 2001, during a period of low flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

4. Diagram showing A, stream channel for River Station 133.7; B, graph of relation 

between altitude and wetted perimeter; and C, graph of relation between wetted 

perimeter and discharge at Fort Meadow Brook near Hudson. . . . . . . . . . . . . . . . . . . . . . . . . . . .9
iv 

5–14. Photographs showing:

5. Assabet River near Westborough, upstream view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

6. Cold Harbor Brook near Northborough, upstream view . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

7. Danforth Brook at Hudson, upstream view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

8. Fort Meadow Brook near Hudson, upstream view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

9. Elizabeth Brook near Stow, downstream view. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

10. Nashoba Brook at West Concord, downstream view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

11. Charles River near Hopkinton, upstream view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

12. Mine Brook near Franklin, downstream view. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

13. Charles River at Medway, downstream views of the study reaches: A, the 

upstream riffle; and B, the downstream riffle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

14. Massachusetts Division of Fisheries and Wildlife personnel barge 

electrofishing for the fish-community assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

15. Pie chart of target fish community for the Quinebaug River . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

16. Map showing location of fish-sampling sites and habitat study sites in the Charles 

and Assabet River Basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

17. Pie chart of fish species habitat-use classifications: A, main stem free-flowing sites 

on the Assabet River, 2000–01; and B, main stem free-flowing sites on the Charles 

River, 2000–01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

18–20. Box plots comparing:

18. Streamflow requirements determined by the R2Cross 3-of-3 criteria, 

R2Cross 2-of-3 criteria, and Wetted-Perimeter methods for all cross sections 

analyzed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

19. R2Cross, 3-of-3 criteria, R2Cross, 2-of-3 criteria, and Wetted-Perimeter method 

streamflow requirements determined at 9 riffle sites in the Assabet and 

Charles River Basins and at 10 streamflow-gaging stations in southern New 

England reported in Armstrong and others (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

20. Drainage area at 9 riffle sites in the Assabet and Charles River Basins at 

10 streamflow-gaging stations in southern New England reported in 

Armstrong and others (2004), and six streamflow-gaging stations near the 

Assabet and Charles River Basins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

21. Graph of quartiles of mean monthly discharges for the period 1976–2000 for six 

streamflow-gaging stations compared with median streamflow requirements 

estimated by the R2Cross 3-of-3 criteria, R2Cross 2-of-3 criteria, and WettedPerimeter methods for nine riffles in the Assabet and Charles River Basins . . . . . . . . . . . . . . 40

Tables

1. Locations and characteristics of riffle reaches, Assabet and Charles Rivers, 

Massachusetts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2. R2Cross hydraulic criteria for four hydraulic parameters for protection of aquatic 

habitat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3. Streamflows required for habitat protection determined by means of the R2Cross 

3-of-3 criteria method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4. Streamflows required for habitat protection determined by means of the R2Cross 

2-of-3 criteria method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5. Streamflows required for habitat protection determined by means of the WettedPerimeter method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
 v

6. Hydraulic characteristics at critical cross sections meeting R2Cross and WettedPerimeter method criteria for habitat protection at the Assabet River near 

Westborough . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

7. Hydraulic characteristics at critical cross sections meeting R2Cross and WettedPerimeter method criteria for habitat protection at Cold Harbor Brook near 

Northborough . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

8. Hydraulic characteristics at critical cross sections meeting R2Cross and WettedPerimeter method criteria for habitat protection at Danforth Brook at Hudson . . . . . . . . . . . .17

9. Hydraulic characteristics at critical cross sections meeting R2Cross and WettedPerimeter method criteria for habitat protection at Fort Meadow Brook near Hudson. . . . . .18

10. Hydraulic characteristics at critical cross sections meeting R2Cross and WettedPerimeter method criteria for habitat protection at Elizabeth Brook near Stow . . . . . . . . . . . .20

11. Hydraulic characteristics at critical cross sections meeting R2Cross and WettedPerimeter method criteria for habitat protection at Nashoba Brook at West Concord. . . . . .21

12. Hydraulic characteristics at critical cross sections meeting R2Cross and WettedPerimeter method criteria for habitat protection at Charles River near Hopkinton . . . . . . . . .23

13. Hydraulic characteristics at critical cross sections meeting R2Cross and WettedPerimeter method criteria for habitat protection at Mine Brook near Franklin . . . . . . . . . . . . .24

14. Hydraulic characteristics at critical cross sections meeting R2Cross and WettedPerimeter method criteria for habitat protection at Charles River at Medway . . . . . . . . . . . . .25

15. Percentages of fish in each habitat-use classification sampled in flowing reaches 

of several river basins in Massachusetts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

16. Number of each species and percent of total number of fish collected in the 

main stem, tributaries, and headwaters of the Assabet and Charles River Basins,

by the Massachusetts Division of Fisheries and Wildlife from 1999 through 2001 . . . . . . . . . .32

17. Summary of R2Cross and Wetted-Perimeter streamflow requirements for nine riffle 

sites included in analysis, Assabet and Charles River Basins . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

18. Streamflow requirements estimated by the Tennant method from the combined 

records of six streamflow-gaging stations near the Assabet and Charles River 

Basins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41

19. Flow statistics determined for Indicators of Hydrologic Alteration approach for six 

streamflow-gaging stations near the Assabet and Charles River Basins. . . . . . . . . . . . . . . . . .47

CONVERSION FACTORS AND VERTICAL DATUM

Local datums used in this report were arbitrarily set at the time of the fieldwork and are not 

referenced to any National Geodetic Vertical Datum. 

Multiply By To obtain

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

cubic foot per second per square mile 

(ft3/s/mi2)

0.01093 cubic meter per second per square kilometer 

(m3/s/km2)

foot (ft) 0.3048 meter (m)

foot per second (ft/s) 0.3048 meter per second (m/s)

mile (mi) 1.609 kilometer (km)

square foot (ft2) 0.09290 square meter (m2)

square mile (mi2) 259 hectare

square mile (mi2) 2.590 square kilometer (km2)

Comparison of Methods for Determining 

Streamflow Requirements for Habitat 

Protection at Selected Sites on the Assabet and 

Charles Rivers, Eastern Massachusetts, 2000–02

By Gene W. Parker, David S. Armstrong (U.S. Geological Survey), and 

Todd A. Richards (Massachusetts Division of Fisheries and Wildlife)

Abstract

Four methods used to determine streamflow requirements 

for habitat protection at nine critical riffle reaches in the Assabet 

River and Charles River Basins were compared. The methods 

include three standard setting techniques—R2Cross, Wetted 

Perimeter, and Tennant—and a diagnostic method, the Range 

of Variability Approach. One study reach is on the main stem of 

the Assabet River, four reaches are on tributaries to the Assabet 

River (Cold Harbor Brook, Danforth Brook, Fort Meadow 

Brook, and Elizabeth Brook), three are on the main stem of the 

Charles River, and one is on a tributary to the Charles River 

(Mine Brook). The strength of the R2Cross and WettedPerimeter methods is that they may be applied at ungaged 

locations whereas the Tennant method and the Range of 

Variability Approach require a period of streamflow record for 

analysis.

Fish community assessments conducted at or near riffle 

sites in flowing reaches of the Assabet River and Charles River 

Basins were used to indicate ecological conditions. The fish 

communities in the main stem and tributary reaches of both the 

Assabet and Charles River Basins indicated degraded aquatic 

ecosystems. However, the degree of degradation differs 

between the two basins. The extreme predominance of tolerant, 

generalist species in the Charles River fish community demonstrates the cumulative impacts of flow, habitat, and waterchemistry degradation, combined with the effects of nearby 

impoundments and changing land use.

The range of discharges for nine ungaged riffle reaches 

defined by the median R2Cross 3-of-3 criteria, R2Cross 2-of-3 

criteria, and Wetted-Perimeter streamflow requirements, was 

0.86 cubic foot per second per square mile, 0.18 cubic foot per 

second per square mile, and 0.23 cubic foot per second per 

square mile, respectively. Application of R2Cross and WettedPerimeter methods to sites with altered streamflows or at sites 

that are riffles only at low to moderate flows can result in a 

greater variability of streamflow requirements than would result 

if the methods were applied to riffles on natural channels with 

unaltered streamflows. The R2Cross 2-of-3 criteria and the 

Wetted-Perimeter streamflow requirements for the Assabet and 

Charles River sites show narrower interquartile ranges and 

lower median streamflow requirements than for 10 index 

streamflow-gaging stations in southern New England. This 

is especially evident for the R2Cross 2-of-3 criteria and 

Wetted-Perimeter results that were close to half of the flow 

requirements determined at the 10 southern New England 

stations.

The R2Cross and Wetted-Perimeter methods were also 

compared to the Range of Variability Approach analysis and 

the Tennant Method. The median R2Cross 3-of-3 criteria 

streamflow requirement for the nine riffles is close to the 75th 

percentile of the monthly mean flows during the summer lowflow period from six streamflow-gaging stations near the 

Assabet and Charles River Basins having mostly unaltered 

flow. This streamflow requirement is close to the median 

Tennant 40-percent-flow requirement for good habitat condition for the same six nearby stations. The R2Cross 2-of-3 

criteria and Wetted-Perimeter results were less than the 25thpercentile of monthly mean flows during the summer months 

for the six stations. These streamflow requirements are in the 

poor habitat range as indicated by a Tennant analysis of the 

same six stations. These comparisons indicate that the R2Cross 

and Wetted-Perimeter methods underestimate streamflow 

requirements when applied to sites in smaller drainage areas 

and channels that are runs at higher flows.
2 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Introduction

During the summer (July through September), when water 

levels are naturally low and the demand for water is high, water 

users are in competition for a limited supply of water. Federal, 

State and local agencies, as well as private citizens’ groups, are 

concerned that streamflows altered by water withdrawals and 

returns could reduce the quality and quantity of the habitat that 

supports the biological integrity of the Assabet River and 

Charles River systems in eastern Massachusetts (fig. 1).

It is generally recognized that the quantity and quality of 

available water may not be sufficient to meet all needs and 

interests of area stakeholders. The Massachusetts Department 

of Conservation and Recreation (MADCR) determined that the 

Assabet River and Charles River Basins could serve as pilot 

areas in which to test methods for determining streamflow 

requirements for habitat protection. The U.S. Geological 

Survey (USGS), in cooperation with the Massachusetts 

Executive Office of Environmental Affairs (EOEA) Watershed 

Initiative Program and MADCR, began a habitat assessment in 

2001 to determine the streamflow requirements in the Assabet 

and Charles River Basins.

In addition, the USGS coordinated its work with fishassessment studies conducted by the Massachusetts Division of 

Fish and Wildlife to evaluate the current (1999–2002) fish 

population in the Assabet and Charles River Basins. Armstrong 

and others (2001) and Bain and Meixler (2000) have documented the utility of using fish to document flow-altered 

conditions in the Northeast. In 2002, a project was started by the 

USGS in cooperation with the Town of Hudson, MA, and in 

collaboration with the Organization of the Assabet River, to 

study additional riffle reaches in the Assabet River Basin. The 

USGS, in cooperation with the MADCR, coordinated the 

habitat project with a ground-water modeling project for the 

Assabet River Basin. The results from the modeling simulations 

will help to quantify the effects of water-use practices on 

streamflow and habitat in the Assabet River Basin.

Techniques for assessing streamflows for habitat 

protection can generally be categorized in three ways: standardsetting, incremental, and diagnostic methods (Instream Flow 

Council, 2002). Standard-setting methods use predetermined 

decision-making formulas or criteria to yield a single streamflow value. Incremental methods involve the analysis of habitat 

conditions at a specific site in relation to multiple decision 

variables for the exploration of different flow-management 

alternatives. Diagnostic methods consist of the examination of 

streamflow records over time for the identification of any 

changing conditions. The selection of a flow to protect habitat 

is based on the results of the different flow-management 

alternatives tested. Incremental methods were not used in this 

project due to their site-specific application.

The R2Cross (Nehring, 1979; Espegren, 1996, 1998) and 

Wetted-Perimeter (Nelson, 1984; Leathe and Nelson, 1986) 

methods are standard-setting, in-stream flow methods that 

require site-specific physical and hydraulic data. Cross-section 

data, and measurements of water depths in a riffle for a range of 

discharges are used to develop and calibrate a step-backwater 

flow model of a riffle habitat. The flow model is then used to 

simulate the physical and hydraulic data used in the R2Cross 

and Wetted-Perimeter methods. An advantage of the R2Cross 

and Wetted-Perimeter methods is that they are based upon 

results from a hydraulic model calibrated to field observations 

and do not require streamflow records; thus, the streamflow 

requirements obtained by these methods can be applied in 

hydrologically disturbed drainage basins and at gaged or 

ungaged sites.

The Tennant standard-setting method (Tennant, 1976) is 

based on a percentage of the average annual discharge for the 

period of streamflow records at a site. Specified percentages of 

the average annual discharge for a site correspond to specified 

levels of quality of habitat protection (excellent to poor). 

The limitation of the method is the requirement of having a 

continuous streamflow record to analyze. Application of the 

Tennant method to streamflow records at sites with altered flow 

conditions would influence subsequent calculations and results.

The Range of Variability Approach (RVA) (Richter and 

others, 1997), which is a diagnostic method, identifies and 

diagnoses an appropriate range of variation in 33 indicators 

of hydrologic alterations (IHA) parameters for a period of 

streamflow record at a site. The range of variation in these 

indicators is used to identify initial streamflow targets for flow 

management and habitat protection. As with the Tennant 

method, application of the method to streamflow records at sites 

with altered flow conditions would influence subsequent 

calculations and results.

Parker and Armstrong (2001) presented preliminary 

results of the R2Cross and Wetted-Perimeter analyses for five 

riffle reaches in the Assabet and Charles River Basins to 

estimate streamflow requirements for habitat protection. The 

results were considered preliminary because the flow conditions were generally too low for model calibration in the flow 

range of interest due to the dry weather prior to December 2001. 

Since the publication of the Parker and Armstrong (2001) 

report, study of the original five riffle reaches has been 

completed and five new reaches have been analyzed.
Introduction 3

42 ̊30'

42 ̊00'

73 ̊30' 73 ̊00' 72 ̊30' 72 ̊00' 71 ̊30'

71 ̊00' 70 ̊30'

70 ̊00'

41 ̊30'

Map derived from MassGIS and USGS digital files

CAPE COD 

BAY

RHODE ISLAND SOUND

NANTUCKET SOUND BUZZARDS BAY VINEYARD SOUND

BLOCK ISLAND SOUND

BOSTON BAY

NEWPORT 

BAY

NARRAGANSETT BAY

MUSKEGET CHANNEL

IPSWICH BAY

0 10 20 30 40 50 KILOMETERS

0 10 20 30 40 50 MILES

ASSABET AND CHARLES STUDY BASINSDRAINAGE-BASIN BOUNDARIES AND BASINS

EXPLANATION

MASSACHUSETTS–RHODE ISLAND MAJOR BASINS

MASSACHUSETTS

RHODE ISLAND

BLACKSTONE

PAWTUXET QUINEBAUG

PAWCATUCK

ANNAQUATUCKET

SAUGATUCKET PETTAQUAMSCUTT

MASKERCHUGG

WOONASQUATUCKET

HUNT

MOSHASSUCK

BLACKSTONE

NASHUA

MERRIMACK

ASSABET

(CONCORD)

CONCORD & SUDBURY

(CONCORD)

SHAWSHEEN

PARKER

IPSWICH

NORTH COASTAL

BOSTON HARBOR

MYSTIC

(BOSTON HARBOR)

NEPONSET

(BOSTON HARBOR)

WEYMOUTH & WIER

(BOSTON HARBOR)

CHARLES

NORTH & SOUTH RIVER

(SOUTH COASTAL)

SOUTH COASTAL SHORE

(SOUTH COASTAL)

CAPE COD

ISLANDS

BUZZARDS BAY

TAUNTON

NARRAGANSETT BAY

& MT. HOPE BAY SHORE

TEN MILE

HOOSIC

(HUDSON)

HOUSATONIC

DEERFIELD

WESTFIELD

FARMINGTON

CONNECTICUT

MILLERS

CHICOPEE

QUINEBAUG

FRENCH

BASHBISH

(HUDSON)

NORTH COASTAL

ISLANDS

QUINEBAUG

MERRIMACK

KINDERHOOK

(HUDSON)

NB & MHB

ISLANDS

COASTAL

BLACKSTONE

QUINEBAUG

CT

Figure 1. Location of major river basins in Massachusetts.
4 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Purpose and Scope

This report compares three standard-setting methods and a 

diagnostic method for estimating the flow necessary to maintain 

aquatic habitat in the Assabet and Charles Rivers. The study 

area includes riffle reaches of the main stem Charles and 

Assabet Rivers and riffle reaches on tributaries to the Assabet 

and Charles Rivers in Massachusetts. The report describes 

streamflow requirements determined by means of the R2Cross 

(Nehring, 1979; Espegren, 1996, 1998), Wetted-Perimeter 

(Nelson, 1984; Leathe and Nelson, 1986), Tennant methods 

(Tennant, 1976), and by the RVA (Richter and others, 1997). 

Incremental methods were not used in this project because of 

their site-specific application. Streamflow requirements for 

aquatic habitat protection were determined from data collected 

in 2001 and 2002 at 10 sites: 3 sites on the main stem Charles 

River, 1 site on the main stem of the Assabet River, and 1 site 

each on Mine Brook in the Charles River Basin and Nashoba 

Brook, Elizabeth Brook, Danforth Brook, Fort Meadow Brook, 

and Cold Harbor Brook in the Assabet River Basin. Streamflow 

requirements for aquatic habitat protection were determined 

by the R2Cross and Wetted-Perimeter methods at 9 of the 10 

riffle sites in the Charles and Assabet River Basins. These 

requirements were compared with average monthly discharges 

determined by using the RVA method and with streamflow 

requirements determined by using the Tennant method for six 

nearby streamflow-gaging stations.

The report also describes the fish communities at or near 

riffle sites in the Assabet and Charles River Basin study areas. 

The report evaluates the health of the habitat in relation to the 

fish population. The evaluation is based on the results of fishpopulation surveys conducted in the study basins during 2000–

02. In addition, the report relates the results to analysis of the 

target fish community determined for the Quinebaug River 

Basin, MA.

Description of Study Sites

The Assabet and Charles Rivers are in nearby drainage 

basins in eastern Massachusetts (fig. 1). The Assabet River is a 

subbasin of the Concord River and is bounded by the Nashua 

and Blackstone River Basins to the west and the Sudbury River 

Basin to the east and south. The Charles River drains into 

Boston Harbor and is bounded by the Blackstone River Basin to 

the west, the Sudbury River to the North, and Taunton and 

Neponset River Basins to the south.

The main-stem study site in the headwaters of the Assabet 

River is a riffle near Westborough, MA (fig. 2). Five tributary 

study sites are on riffles on Nashoba Brook, Elizabeth Brook, 

Danforth Brook, Fort Meadow Brook, and Cold Harbor Brook 

(table 1). The Assabet River study site is about 100 ft downstream of the bridge over Fisher Street in Westborough, MA. 

The Nashoba Brook study site is about 110 ft downstream 

of Commonwealth Avenue in West Concord, MA, and about 

950 ft upstream of the brook’s mouth at the Assabet River. The 

Elizabeth Brook study site is just downstream of a ford on an 

unnamed road in Stow, MA, and about 0.72 mi upstream of the 

brook’s mouth at the Assabet River. The Fort Meadow Brook 

study site is in Hudson, MA, about 1.5 mi upstream from the 

brook’s mouth at the Assabet River. The Danforth Brook study 

site is in Hudson, MA, about 1.35 mi upstream of the brook’s 

mouth at the Assabet River. The Cold Harbor Brook study site 

is in Northborough, MA, about 2.9 mi upstream of the brook’s 

mouth at the Assabet River.

The two main-stem Charles River study sites are riffles 

upstream of the Walker Street Bridge and the streamflowgaging station on the Charles River at Medway (01103200). 

An additional main-stem study site is in the headwaters of the 

Charles River on a riffle in Hopkinton, MA, about 300 ft downstream of Echo Lake and about 3,450 ft upstream of the State 

Route 85 culvert in Milford, MA. The Mine Brook study site is 

at a riffle about 800 ft east of the intersection of Routes 140 and 

I-495 in Franklin, MA (table 1).

Methods for Determining Streamflow 

Requirements for Aquatic Habitat 

Protection

Two standard-setting methods, the R2Cross method 

(Espegren, 1996, 1998; Nehring, 1979) and the WettedPerimeter method (Nelson, 1984; Leathe and Nelson, 1986), 

were applied at 10 riffle study sites in the Assabet and Charles 

River Basins for the evaluation of streamflow requirements 

for aquatic habitat protection. For comparison purposes, the 

Tennant method (Tennant, 1976), a standard-setting method, 

and the RVA method (Richter and others, 1996), a diagnostic 

method, were applied to records from six streamflow-gaging 

stations at sites with relatively unaltered streamflows and 

within 30 mi of the ten riffle study sites. The results of the 

comparison indicate the minimal streamflows that could protect 

aquatic habitat in relatively unaltered-flow basins in the region 

around the Assabet and Charles River Basins.
Methods for Determining Streamflow Requirements for Aquatic Habitat Protection 5

Squannacook River near Squannacook River near 

West Gronton (01096000) West Gronton (01096000)

Danforth Brook at Hudson, MA Danforth Brook at Hudson, MA

Cold Harbor Brook near Northborough, MA Cold Harbor Brook near Northborough, MA

Elizabeth Brook Elizabeth Brook

 near Stow, MA near Stow, MA

Sevenmile River near Sevenmile River near

Spencer (01175670) Spencer (01175670)

RIFFLE REACH RIFFLE REACH 

Charles River at Medway, MA Charles River at Medway, MA

Charles River near Hopkinton, MA Charles River near Hopkinton, MA

Worcester Worcester

GAGING STATION AND NUMBER GAGING STATION AND NUMBER

Assabet River near Assabet River near 

Westborough, MA Westborough, MA

EXPLANATION EXPLANATION

STATE BOUNDARY STATE BOUNDARY

BASIN BOUNDARY BASIN BOUNDARY

Mine Brook near Franklin, MA Mine Brook near Franklin, MA

Indian Head River near Indian Head River near

Hanover, MA (01105730) Hanover, MA (01105730)

Branch River at Forestdale, RI (01111500) Branch River at Forestdale, RI (01111500)

Fort Meadow Brook near Hudson, MA Fort Meadow Brook near Hudson, MA

Assabet Assabet

Charles Charles

42 ̊30'

43 ̊30'

42 ̊00'

72 ̊00' 71 ̊00'

Base from U.S. Geological Survey digital data,

Massachusetts State Plane, zone 4151,1991

1:25,000 series

ATLANTIC

OCEAN

Squannacook River near 

West Groton (01096000)

Danforth Brook at Hudson, MA

Cold Harbor Brook near Northborough, MA

Elizabeth Brook Elizabeth Brook

 near Stow, MA near Stow, MA

Elizabeth Brook

 near Stow, MA

Sevenmile River near

Spencer (01175670)

RIFFLE REACH 

Charles River at Medway, MA

Charles River near Hopkinton, MA

STREAMFLOW-GAGING STATIONS AND NUMBER

Assabet River near 

Westborough, MA

EXPLANATION

STATE BOUNDARY

BASIN BOUNDARY

Mine Brook near Franklin, MA

Indian Head River near

Hanover, MA (01105730)

Branch River at Forestdale, RI (01111500)

Fort Meadow Brook near Hudson, MA

Assabet

Charles

Beaver Brook near 

North Pelham, NH (010965852)

Nashoba Brook Nashoba Brook

near W. Concord, MA near W. Concord, MA

Nashoba Brook

near W. Concord, MA

Old Swamp River

near South

Weymouth, MA (01105600)

(01175670)

0 50 MILES

0 50 KILOMETERS

CONNECTICUT

RHODE ISLAND

Boston

NEW HAMPSHIRE

MASSACHUSETTS

Providence

Nashua

Worchester

Methuen

Plymouth

Fitchburg

0 50 MILES

0 50 KILOMETERS

73 ̊00'

42 ̊30'

42 ̊00'

72 ̊00'

71 ̊00'

70 ̊00'

ATLANTIC OCEAN

Massachusetts

Bay

Nantucket

Sound

STUDY

BASINS

Figure 2. Location of study sites and six streamflow-gaging stations near the Charles and Assabet River Basins, Massachusetts.
6 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Table 1. Locations and characteristics of riffle reaches, Assabet and Charles Rivers, Massachusetts.

[ft, foot; mi2, square mile]

River basin Stream name Town Riffle location

Approximate

riffle length

(ft)

Drainage

area

(mi2)

Assabet River Assabet River Westborough 100 ft downstream of Fisher Street Bridge 100 6.79

Cold Harbor Brook Northborough 250 ft downstream of Cherry Street culvert 60 5.06

Danforth Brook Hudson 300 ft upstream of Route 85 culvert 80 5.12

Fort Meadow Brook Hudson 1,350 ft upstream of Shay Street culvert 90 4.85

Elizabeth Brook Stow 1,060 ft south of White Pond Road 70 18.7

Nashoba Brook West Concord 110 ft downstream of Commonwealth Avenue Bridge 130 48.01

Charles River Charles River Hopkinton 3,450 ft upstream of State Route 85 culvert in Milford 90 1.58

Mine Brook Franklin 680 ft upstream of Route 140 culvert 87 10.0

Charles River Medway 1,480 ft upstream of Walker Street Bridge 30 65.7

Charles River Medway 600 ft upstream of Walker Street Bridge 110 65.7

Application of the R2Cross and Wetted-Perimeter 

methods requires careful selection of study sites in riffle 

habitats. A riffle is a section of channel, usually between pools, 

that has gravel-to-cobble-sized bed material. The water surface 

is turbulent with little or no whitewater and average velocities 

are in the range of 0.6 ft/s to 1.6 ft/s (Bain and Stevenson, 1999). 

Appropriate riffles for application of the R2Cross and WettedPerimeter methods extend across the entire channel, are fairly 

stable, and maintain hydraulic control over a range of low to 

moderate flows. Differences in channel geometry among riffles 

can create variability in the determined streamflow requirements. For example, reaches that have large boulders or woody 

debris in the channel or altered streambeds or banks should be 

avoided. If possible, riffle sites are chosen that represent natural 

riffle conditions. The methods work best in riffles in alluvial 

channels that adjust their width and depth to accommodate 

higher flows. Alterations to channels can have a direct effect on 

streamflow recommendations generated by these methods. The 

artificial widening or narrowing of the stream channel at a site 

can affect wetted perimeter, average velocity, and average 

depth. The reinforcement of stream banks and streambeds with 

riprap prevents natural width and depth adjustments. Consequently, streamflow requirements determined for natural riffle 

sites may not be sufficient to protect habitat at sites in a widened 

channel and may be excessive at sites in an artificially restricted 

channel; conversely, flow requirements estimated at sites with 

a narrowed channel may not provide sufficient flows for habitat 

protection in unaltered stream reaches.

Water-Surface-Profile Modeling

A water-surface-profile model, the U.S. Army Corps of 

Engineers Hydrologic Engineering Center’s River Analysis 

System (HEC-RAS; Brunner, 2001), was used in this study to 

simulate the water-surface profile for each riffle site and to 

determine the hydraulic parameters required for application of 

both the R2Cross and Wetted-Perimeter methods. HEC-RAS is 

designed to perform one-dimensional hydraulic calculations for 

a network of natural or constructed channels under steady or 

gradually varying flow. The computational procedure is based 

on the solution of the one-dimensional energy equation from 

one stream section to the next. Energy losses are evaluated 

by friction (Manning’s equation) and channel contraction or 

expansion (Brunner, 2001). Once calibrated, the HEC-RAS 

model is used to simulate hydraulic parameters for a wide range 

of discharges. R2Cross streamflow requirements are determined from a staging table of discharges, water-surface 

altitudes, stream-top width, average depth, average velocity, 

and percentage of bankfull wetted perimeter. Wetted-perimeter 

streamflow requirements are determined from plots of wetted 

perimeter and discharge, wetted perimeter and water-surface 

altitude, and stream cross section.

R2Cross Method

The R2Cross method requires selection of a critical riffle 

along a stream and is based on the assumption that a discharge 

chosen to maintain habitat in the riffle is sufficient to maintain 

habitat for fish in nearby pools and runs for most life stages of 

fish and aquatic invertebrates (Nehring, 1979). As can be seen 

in figure 3, the flow conditions at a pooled reach include slower 

velocities, greater depths, and greater wetted perimeters than 

the flow conditions found at an adjacent riffle reach for the 

same discharge. Streamflow requirements for habitat protection 

in riffles are based on minimum flows that meet or exceed 

criteria for three hydraulic parameters: average depth, percent 

of bankfull wetted perimeter, and average water velocity 

(table 2). Criteria for these hydraulic variables were developed 

in Colorado to quantify the amount of streamflow required for 

“preserving the natural environment to a reasonable degree” 

(Espegren, 1996).
Methods for Determining Streamflow Requirements for Aquatic Habitat Protection 7

A.

B.

Figure 3. A, Riffle and B, pooled reaches on the Charles River at Medway, Massachusetts, on 

August 1, 2001, during a period of low flow.
8 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

To account for seasonal streamflow variability, the 

R2Cross method establishes different streamflow requirements 

for the summer and winter seasons. Initial streamflow 

recommendations in Colorado are based upon the minimal 

streamflows that meet or exceed all three hydraulic criteria 

during the high-flow period in summer and any two of the three 

hydraulic criteria during its low-flow period in winter (table 2). 

In contrast to Colorado, Massachusetts’s flows are generally 

lowest in mid summer and early fall (July through September). 

For this study, R2Cross streamflow recommendations were 

determined by the methods based on 3-of-3 and 2-of-3 

hydraulic criteria. The criteria are scaled to each channel on the 

basis of the bankfull channel width and wetted perimeter.

Streamflow requirements for habitat protection in riffles 

determined by using the R2Cross methodology usually involve 

the calculation of the energy loss in the form of friction 

(Manning’s equation) for a single cross section in a study riffle. 

HEC-RAS was used to simulate the water-surface profile for 

each riffle site. Use of multiple cross-sections and the HECRAS model provides improved simulations of the hydraulic 

conditions expected in riffles in comparison to conditions 

simulated by modeling an individual cross section.

Wetted-Perimeter Method

The Wetted-Perimeter method is based on the assumption 

that there is a direct relation between the wetted perimeter in a 

riffle and fish habitat in streams (Annear and Conder, 1984; 

Lohr, 1993). The wetted perimeter of a stream, defined as the 

width of the streambed and stream banks in contact with water 

for an individual cross section, is used as a measure of the 

availability of aquatic habitat over a range of discharges 

(Annear and Conder, 1984; Nelson, 1984). A plot of the relation 

between wetted perimeter and discharge indicates the discharge 

that fully wets the bottom of the channel bed (fig. 4). These 

plots generally have a characteristic shape—steeper at low 

discharges and flatter at high discharges. Initially, as the 

channel fills with water, the wetted perimeter increases sharply 

for each unit increase in discharge. Once the water rises above 

the bottom of the bank, the rate of increase of wetted perimeter 

for each unit increase of discharge abruptly decreases. This 

abrupt decrease is indicated by the curves breakpoint. The 

breakpoint is used to determine the streamflow required for 

habitat protection. On a stream cross section, this point 

theoretically corresponds to the break in slope at the bottom of 

a stream bank where the water surface would begin to rise up 

the banks when flows increase, or recede in a more horizontal 

direction from the stream banks when flows decrease.

The Wetted-Perimeter method should be applied only to 

cross sections in riffle habitats. The method should not be 

applied in other habitats such as pools or runs. The WettedPerimeter method is best applied to rectangular or trapezoidal 

cross sections within riffles on straight reaches. The shape of 

the relation between wetted perimeter and discharge is largely a 

function of channel geometry. The bottom of the bank is most 

readily identified in the field in channels with rectangular or 

trapezoidal cross sections, which produce a more defined 

breakpoint than triangular or bowl-shaped cross-sections 

(Gippel and Stewardson, 1998). In practice, there is seldom a 

single break in slope in the wetted-perimeter-to-discharge 

relation. The slope of the stream banks, the presence of bars or 

boulders, or other irregularities in the streambed or banks can 

contribute to the lack of a distinct breakpoint or multiple breaks 

in slope. Less well-defined breakpoints may also be a function 

of the number, density, and location of points surveyed along a 

cross section.

The Wetted-Perimeter method is best applied in alluvial 

channels that can naturally adjust their depth and width. 

Application of the method to disturbed channels (widened or 

narrowed) or channels with hardened stream banks (rip-rap or a 

stone wall) will likely increase the variability of streamflow 

requirements determined by the method. Cross sections should 

be selected to avoid woody debris, large rocks, or other 

obstructions that extend above the water surface. Cross sections 

on bends where the channel has a deep thalweg against the bank 

on outside of the bend, and a point bar on the inside of the bend, 

should also be avoided where possible. Cross sections at 

transitions between the riffle itself and other habitats at the 

upstream or downstream ends of the riffle should also be 

avoided.

For this study, several detailed cross sections were 

surveyed at each riffle site. Points that corresponded to changes 

in slope of the streambeds and banks were surveyed along the 

cross section. The altitudes of the bottoms of the stream banks 

that corresponded to a fully wetted channel were determined 

during surveying. These surveyed bottom-of-the-bank altitudes 

were used to determine of Wetted-Perimeter streamflow 

requirements. In cross sections where the transition between 

streambed and bank is gradual, several points defining the 

transition were surveyed along with points that defined the 

channel width.

Table 2. R2Cross criteria for four hydraulic parameters for 

protection of aquatic habitat.

[Source: Modified from Espegren, 1996. ft, foot; ft/s, foot per second; 

>, greater than or equal to]

Stream

top width

(ft)

Average

depth

(ft)

Bankfull

wetted

perimeter

(percent)

Average 

velocity

(ft/s)

1–20 0.2 50 1.0

21–50 0.2–0.5 50 1.0

51–60 0.5–0.6 50–60 1.0

61–100 0.6–1.0 >70 1.0
Methods for Determining Streamflow Requirements for Aquatic Habitat Protection 9

01 23 4 8 5 6 7 9 10 11 12 13 14 15 16 17 18 19

DISCHARGE, IN CUBIC FEET PER SECOND

WETTED PERIMETER,

IN FEET

0

10 

15

20

25

20

498.0

498.5

499.0

499.5

500.0

500.5

501.0

501.5

ALTITUDE, IN FEET

A. Fort Meadow Brook near Hudson

Cross Section 133.7

STATION, IN FEET

0 10 20 30 40 50

Bank station

Field determined 

bottom of bank

60 70

498.0

498.2

498.4

498.6

498.8

499.0

ALTITUDE, IN FEET

B.

C.

Fort Meadow Brook near Hudson

Cross Section 133.7

Fort Meadow Brook near Hudson

Cross Section 133.7

WETTED PERIMETER

0 5 10 15 20 25

18.4

Bottom, right bank

Bottom, left bank

Bottom, right bank

Bottom, left bank

2.2

Figure 4. A, Stream channel for River Station 133.7; B, graph of relation between altitude and wetted perimeter; and C, graph 

of relation between wetted perimeter and discharge at Fort Meadow Brook near Hudson, Massachusetts.
10 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Plots of water-surface altitude and wetted perimeter were 

also used in this study to identify breakpoints due to changes in 

channel geometry. In a rectangular or trapezoidal channel with 

steep banks, the altitudes of the bottoms of the left and right 

banks define a narrow range of elevations that corresponds 

with a break in slope. If the breakpoint on the plot of wetted 

perimeter and discharge was not associated with the altitudes of 

the bottoms of banks or if there were multiple breakpoints, the 

breakpoint on the plot of wetted perimeter and water-surface 

altitude plot that most closely corresponds with the elevations 

of the left and right bottoms of bank is used to determine 

the streamflow requirement. In a triangular or bowl-shaped 

channel, or trapezoid-shaped channel where one or both banks 

have a shallow slope, the surveyed bottoms of banks may not 

correspond with or bracket a breakpoint. If the bottoms of banks 

were not at the same altitudes, a breakpoint on the wetted 

perimeter and discharge plot that corresponds with the altitudes 

of the bottoms of banks was used to determine the streamflow 

requirement. If no breakpoint corresponded to the altitudes of 

the bottoms of banks, a breakpoint near or between the altitudes 

of the bottoms of banks that corresponds with the channel width 

was used to determine the streamflow requirement. If the 

bottoms of banks were not at the same altitude, and there were 

no distinct breakpoints between the bottoms of banks, a 

streamflow requirement was not determined for that cross 

section.

Range of Variability Approach

The RVA method identifies the range of target streamflows as the interquartile ranges for each of 33 statistical 

indicators of IHA parameters. The method is a diagnostic 

technique used to guide management effort to restore or 

maintain natural variability in hydrologic systems (Instream 

Flow Council, 2002). The IHA Analysis (Richter and others, 

1996) was developed by the Nature Conservancy to assess the 

range of variation of discharge for a river through a statistical 

characterization of ecologically related hydrologic parameters. 

The technique uses daily streamflow records to determine the 

variation in the 33 parameters. Half of the statistics measure the 

central tendency of the magnitude or the rate of change of water 

conditions, and half focus on the magnitude, duration, timing, 

and frequency of extreme events. This information may be used 

to formulate target ranges for streamflows for river management. The technique is best applied to gaged, unregulated 

streams to document the natural variability that can occur in 

streamflows.

Tennant Method

The Tennant method (Tennant, 1976) is a standard-setting 

technique that bases its streamflow requirements on the observation that aquatic-habitat conditions are similar in streams 

carrying the same proportion of the mean annual flow (QMA). 

To account for seasonal streamflow variability, the Tennant 

Method established different streamflow requirements for the 

summer and winter seasons on the basis of different percentages 

of the QMA. In the mountainous western United States, where 

the Tennant method was developed, precipitation patterns and 

snowmelt runoff typically result in low streamflows in fall and 

early winter and high streamflows in the summer. Therefore, 

the Tennant streamflow recommendations are higher in the 

summer than in the winter. In southern New England, streamflow generally is lowest in mid summer and early fall and 

highest in spring. Thus, the summer streamflow criteria recommended by Tennant may be high. Because low summer streamflows in southern New England may also be linked to additional 

stresses, such as high stream temperatures and low dissolved 

oxygen concentrations, both the Tennant summer and winter 

criteria are evaluated in this report for use during summer. The 

Tennant method is best applied to gaged, unregulated streams.

Streamflow Requirements for 

Aquatic Habitat Protection

The R2Cross and Wetted-Perimeter standard-setting 

methods were used to evaluate streamflow requirements for 

habitat protection for sites on the Assabet River and Charles 

River for the summer period. Ten riffle reaches were identified 

for determination of streamflow requirements. One of these 

sites was in the headwaters of the Assabet River, five were on 

tributaries to the Assabet River, two were on the main stem of 

the Charles River, one was in the headwaters of the Charles 

River, and one was on a tributary to the Charles River. With the 

exception of two tributary sites in the Assabet River Basin, all 

sites might have had altered flow conditions due to wellfield 

withdrawals or direct diversion of flow upstream of the study 

sites.

Assabet River near Westborough

The study reach on the Assabet River riffle is about 100 ft 

downstream of the Fisher Street Bridge near Westborough, MA 

(fig. 5). Five cross sections of trapezoidal shape were surveyed 

on July 25, 2002, along a 100-ft reach and included in the 

hydraulic, water-surface-profile model. The channel is bounded 

by an open field along its left bank with a narrow border of 

shrubs. Scattered trees and shrubs in front of hardwood forest 

bound the right bank. The bed material is primarily silt and sand 

with a few cobbles. The bank material is composed of organic 

silt and sand. The stream has a moderate slope; the water 

surface drops from about 0.5 to 0.1 ft along the study reach 

at measured flows ranging from 0.05 to 27.3 ft3/s.

The HEC-RAS model was calibrated as a subcritial flow 

regime by using the standard upstream-step energy method 

as documented in Appendix 1. The calibration accuracy was 

calculated as the root mean square of the differences between 

the observed and modeled water-surface altitudes for all cross 
Streamflow Requirements for Aquatic Habitat Protection 11

Figure 5. Assabet River near Westborough, Massachusetts, upstream view.

sections with measured discharges in the modeled reach. 

The calibration accuracy was 0.015 ft over the entire reach 

for all measured discharges. The HEC-RAS software 

occasionally indicated the need for more cross sections to 

reduce velocity head drops between sections. Interpolated 

cross sections were added to the model between surveyed 

cross sections to reduce the velocity head drops between 

sections and improve the model calibration to observed 

water-surface altitudes.

The R2Cross analysis to determine the required 

streamflow for habitat protection was based upon the 

HEC-RAS simulation results for the cross sections 116.71, 

127.83, and 136.38 (tables 3 and 4). The cross sections at river 

stations 116.71, 127.83, and 136.38 were identified as the 

critical sections in the riffle reach because they are upstream 

of the point where the riffle is influenced by any backwater. 

The limiting R2Cross criterion was the average velocity for 

3-of-3 criteria and average depth for 2-of-3 criteria for all 

three study sections.

Relations between wetted perimeter and discharge and 

between altitude of water surface and wetted perimeter were 

determined for cross sections at river stations 116.71, 127.83, 

and 136.38 on the basis of the HEC-RAS simulations for a 

range of discharges up to bankfull flow. The discharges identified by the Wetted-Perimeter method as required for habitat 

protection during the summer period are summarized in table 5. 

The hydraulic parameters associated with these discharges as 

well as the hydraulic characteristics of the discharges that met 

the R2Cross 3-of-3 and 2-of-3 criteria requirements are 

summarized in table 6.

Cold Harbor Brook near Northborough

The riffle study reach on Cold Harbor Brook (fig. 6) is 

about 250 ft downstream of the bridge on Cherry Street in 

Northborough, MA. Six cross sections of trapezoidal shape 

were surveyed on July 26, 2002, along a 60-ft reach and 

included in the water-surface-profile model. The channel gently 

meandered along the length of the study reach. There are 

scattered trees and shrubs with open fields along the right bank 

and a narrow border of shrubs on the left bank of the channel. 

The bed material is primarily silt and sand with a few cobbles. 

The bank material is composed of organic soil, silt, and sand. 

The stream has a moderate slope; the water surface drops about 

0.6 to 0.2 ft along the study reach at measured flows ranging 

from 0.1 to 11.9 ft3/s.

The HEC-RAS model was calibrated as a subcritial flow 

regime by using the standard upstream-step energy method as 

documented in Appendix 1. The model calibration accuracy 

was 0.006 ft over the entire reach for all measured discharges. 

The HEC-RAS software occasionally indicated the need for 

more cross sections to reduce velocity-head drops between 

sections. Interpolated cross sections were added to the model 

between surveyed cross sections to reduce the velocity-head 

drops between sections and improve the model calibration to 

observed water-surface altitudes.
12 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Table 3. Streamflows required for habitat protection determined by means of the R2Cross 3-of-3-criteria method.

[ft3/s, cubic foot per second; ft3/s/mi2, cubic foot per second per square mile; mi2, square mile]

River and reach

Drainage

area

(mi2

)

River station

Discharge Limiting

R2Cross

criteria (ft3

/s) (ft3/s/mi2)

Assabet River Basin

Assabet River near Westborough 6.79 116.71

127.83

136.38

5.8

6.8

8

0.854

1.001

1.178

Velocity.

Velocity.

Velocity.

Cold Harbor Brook near Northborough 5.06 137.4 3.5 .692 Velocity.

Danforth Brook at Hudson 5.12 25.9

51.9

60.8

68.7

81.6

14.4

10.10

8.10

10.4

11.5

2.813

1.973

1.582

2.031

2.246

Velocity.

Velocity.

Velocity.

Velocity.

Velocity.

Fort Meadow Brook near Hudson 4.85 133.7 7.3 1.505 Velocity.

Elizabeth Brook near Stow 18.7 202.05

213.57

229.45

241.46

10

9

10.5

12

.535

.481

.561

.642

Depth.

Velocity.

Depth.

Depth.

Nashoba Brook at West Concord 48.01 120.3

142.5

164.5

7.1

6.8

5.8

.148

.141

.12

Depth.

Velocity.

Velocity.

Charles River Basin

Charles River near Hopkinton 1.58 101.39

157.84

166.01

2.2

2

2.7

1.392

1.266

1.709

Velocity.

Velocity.

Velocity.

Mine Brook near Franklin 10.1 112.91

123.60

143.62

164.85

173.65

187.25

9

7

6.2

4.2

2.5

8.2

.891

.693

.614

.416

.248

.812

Velocity.

Velocity.

Velocity.

Velocity.

Velocity.

Velocity.

Charles River near Medway upstream 65.7 1,481.8

1,498.9

45.4

52.8

.691

.804

Depth.

Depth.

Charles River near Medway downstream 65.7 691.6 57 .868 Depth.
Streamflow Requirements for Aquatic Habitat Protection 13

Table 4. Streamflows required for habitat protection determined by means of the R2Cross 2-of-3-criteria method.

[ft3/s, cubic foot per second; ft3/s/mi2, cubic foot per second per square mile; mi2, square mile]

River and reach

Drainage

area

(mi2

)

River station

Discharge Limiting

R2Cross

criteria (ft3/s) (ft3

/s/mi2)

Assabet River Basin

Assabet River near Westborough 6.79 116.71

127.83

136.38

0.6

.4

.45

0.088

.059

.066

Depth.

Depth.

Depth.

Cold Harbor Brook near Northborough 5.06 137.4 .2 .53 Depth.

Danforth Brook at Hudson 5.12 25.9

51.9

60.8

68.7

81.6

.18

.40

1.20

.90

2

.035

.078

.234

.176

.391

Depth.

Depth.

Depth.

Depth.

Depth.

Fort Meadow Brook near Hudson 4.85 133.7 2.2 .454 Depth.

Elizabeth Brook near Stow 18.7 202.05

213.57

229.45

241.46

5

6.5

3.6

10.2

.267

.348

.193

.548

Velocity.

Depth.

Velocity.

Velocity.

Nashoba Brook at West Concord 48.01 120.3

142.5

164.5

5.2

5.5

4.2

.108

.115

.089

Velocity.

Depth.

Depth.

Charles River Basin

Charles River near Hopkinton 1.58 101.39

157.84

166.01

0.21

2.0

.22

0.133

1.266

.139

Wetted perimeter.

Depth.

Wetted perimeter.

Mine Brook near Franklin 10.1 112.91

123.6

143.62

164.85

173.65

187.25

2.3

.8

1.1

1.1

1.9

3.8

.228

.079

.109

.107

.188

.376

Depth.

Depth.

Depth.

Wetted perimeter.

Depth.

Depth.

Charles River near Medway upstream 65.7 1,481.8

1,498.9

8

11.6

.122

.177

Velocity.

Velocity.

Charles River near Medway downstream 65.7 691.6 21.6 .329 Velocity.
14 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Table 5. Streamflows required for habitat protection determined by means of the Wetted-Perimeter method.

[ft3/s, cubic foot per second; ft3/s/mi2, cubic foot per second per square mile; mi2, square mile]

River and reach

Drainage

area

(mi2)

River

station

Discharge

(ft3/s) (ft3/s/mi2)

Assabet River Basin

Assabet River near 

Westborough

6.79 116.71

127.83

136.38

0.6

.2

.2

0.088

.029

.029

Cold Harbor Brook near 

Northborough

5.06 137.4 1.3 .257

Danforth Brook at Hudson 5.12 25.9

81.6

.5

2

.195

.82

Fort Meadow Brook near 

Hudson

4.85 133.7 1.7 .351

Elizabeth Brook near 

Stow

18.7 202.05

213.57

229.45

241.46

3.5

1.8

5.5

3

.187

.096

.294

.16

Nashoba Brook at West 

Concord

48.01 120.3

142.5

164.5

7.0

5

4

.146

.104

.083

Charles River Basin

Charles River near 

Hopkinton

1.58 101.39

166.01

0.2

.45

0.127

.285

Mine Brook near Franklin 10.1 112.91

123.6

143.62

164.85

173.65

187.25

5.8

5.2

6.2

6.5

5.6

2.2

.574

.515

.614

.644

.337

.218

Charles River near 

Medway upstream

65.7 1,481.8

1,498.9

16.5

7.7

.251

.117

Charles River near 

Medway downstream

65.7 691.6 8.7 .132

River and reach

Drainage

area

(mi2)

River

station

Discharge

(ft3/s) (ft3/s/mi2)

Table 6. Hydraulic characteristics at critical cross sections meeting R2Cross and Wetted-Perimeter method criteria for habitat 

protection at the Assabet River near Westborough, Massachusetts.

[ft, foot; ft3/s, cubic foot per second; ft/s, foot per second; --, not applicable]

River

station

Discharge

(ft3/s)

Top width

(ft)

Wetted 

perimeter

(ft)

Average

depth

(ft)

Average 

velocity

(ft/s)

Notes

116.71 13 14.12 14.95 -- -- Bankfull discharge.

5.75 -- 14.06 0.42 1 Meets 3-of-3 criteria.

.6 -- 13.56 .20 .22 Meets 2-of-3 criteria.

.6 -- 13.56 .20 .22 Meets wetted-perimeter criteria.

127.83 13 15.47 15.53 -- -- Bankfull discharge.

6.75 -- 14.16 .48 1 Meets 3-of-3 criteria.

.4 -- 12.39 .20 .16 Meets 2-of-3 criteria.

.2 -- 11.87 .12 .14 Meets wetted-perimeter criteria.

136.38 13 21.22 21.92 -- -- Bankfull discharge.

8 -- 19.97 .42 1 Meets 3-of-3 criteria.

.45 -- 11.16 .20 .21 Meets 2-of-3 criteria.

.2 -- 10.45 .15 .13 Meets wetted-perimeter criteria.
Streamflow Requirements for Aquatic Habitat Protection 15

The R2Cross analysis to determine the required streamflow for habitat protection was based upon the HEC-RAS 

model results for the cross section at river station 137.4 

(tables 3 and 4). The hydraulic characteristics that met the 

R2Cross 3-of-3 and 2-of-3 criteria requirements from the 

calibrated model for each cross section are summarized in 

table 7. The cross section at river station 137.4 was identified 

as being the critical section in the riffle reach because it is 

upstream of the point where the riffle is influenced by backwater. The limiting R2Cross criterion was the average velocity 

for 3-of-3 criteria and the average depth for 2-of-3 criteria.

Wetted perimeter-discharge and stage-wetted perimeter 

relations were determined for cross sections at river station 

137.4 on the basis of the HEC-RAS simulations for a range of 

discharges up to bankfull flow. The discharge identified by the 

Wetted-Perimeter method as required for habitat protection 

during the summer period are summarized in table 5. The 

hydraulic parameters associated this discharge are summarized 

in table 7.

Figure 6. Cold Harbor Brook near Northborough, 

Massachusetts, upstream view.

Table 7. Hydraulic characteristics at critical cross sections meeting R2Cross and Wetted-Perimeter method criteria for habitat 

protection at Cold Harbor Brook near Northborough, Massachusetts.

[ft, foot; ft3/s, cubic foot per second; ft/s, foot per second; --, not applicable]

River

station

Discharge

(ft3/s)

Top width

(ft)

Wetted

perimeter

(ft)

Average

depth

(ft)

Average 

velocity

(ft/s)

Notes

137.4 7.2 14.22 14.49 -- -- Bankfull discharge.

3.5 -- 10.12 0.3 1 Meets 3-of-3 criteria.

.26 -- 7.84 .2 .17 Meets 2-of-3 criteria.

1.3 -- 8.73 .30 .51 Meets wetted-perimeter criteria.
16 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Danforth Brook at Hudson

The riffle section studied on Danforth Brook (fig. 7) is 

about 300 ft upstream of the Route 85 culvert in a conservation 

area owned by the town of Hudson. Seven cross sections were 

surveyed on September 19, 2001, in this study reach, six of 

which were included in the water-surface-profile model. The 

cross sections were along an 80-ft length of pool and riffle 

habitats and were predominantly trapezoidal in shape. The 

channel takes a shallow bend to the left along the study reach. 

There are scattered trees and shrubs along both banks, the 

bed material is primarily cobbles, and the bank material is 

composed of rich organic soil, silt, sand, and cobbles. The 

stream has a moderately steep slope. The water surface drops 

about 1.8 to 1.6 ft along the study reach for all measured flows 

ranging from 0.009 ft3/s to 28.5 ft3/s.

The HEC-RAS model was calibrated as a subcritial flow 

regime by using the standard upstream-step energy method as 

documented in Appendix 1. The model calibration accuracy 

was 0.004 ft over the entire reach for all measured discharges. 

The HEC-RAS software occasionally indicated the need for 

more cross sections to reduce velocity head drops between 

sections. Interpolated cross sections were added to the model 

between surveyed cross sections to reduce the velocity head 

drops between sections and improve the model calibration to 

observed water-surface altitudes.

The R2Cross analysis to determine the required streamflow for habitat protection was based upon the HEC-RAS 

model results for cross sections at river stations 25.9, 51.9, 

60.8, 68.7, and 81.6 (tables 3 and 4). The hydraulic characteristics that met the R2Cross 3-of-3 and 2-of-3 criteria requirements from the calibrated model for each cross section are 

summarized in table 8. The cross sections at river stations 25.9, 

51.9, 60.8, 68.7, and 81.6 were identified as being the critical 

sections in the riffle reach because they are upstream of the 

point where the riffle is influenced by backwater. The limiting 

R2Cross criterion for 3-of-3 criteria was the average velocity 

and the average depth was the limiting criterion for 2-of-3 

criteria at all sections. Parker and Armstrong (2001) reported 

a preliminary estimate of the required streamflow for habitat 

protection of 10.5 to 14.3 ft3/s, which meets 3-of-3 criteria for 

two cross sections at this site. The estimates in table 3 are the 

result of a HEC-RAS simulation that is calibrated over a greater 

range of discharges. The streamflow requirements that meet 3-

of-3 criteria range from 8.1 to 14.4 ft3/s for five cross sections 

(table 3).

Relations between wetted perimeter and discharge and 

between altitude of the water surface and wetted perimeter were 

determined for cross sections at river stations 25.9 and 81.6 on 

the basis of the HEC-RAS simulations for a range of discharges 

up to bankfull flow. The discharges identified by the WettedPerimeter method as required for habitat protection during the 

summer period as range from 0.5 to 2.0 ft3/s (table 5). The 

hydraulic parameters associated with these discharges are 

summarized in table 8. The range of discharges in table 5 for 

Danforth Brook are considerably greater than the preliminary 

estimates reported by Parker and Armstrong (2001). The 

estimates in table 5 are the result of a HEC-RAS simulation that 

was calibrated over a greater range of discharges than the range 

that was used in the preliminary analysis.

Figure 7. Danforth Brook at Hudson, Massachusetts, upstream view.
Streamflow Requirements for Aquatic Habitat Protection 17

Table 8. Hydraulic characteristics at critical cross sections meeting R2Cross and Wetted-Perimeter method criteria for habitat 

protection at Danforth Brook at Hudson, Massachusetts.

[ft, foot; ft3/s, cubic foot per second; ft/s, foot per second; --, not applicable]

River

station

Discharge

(ft3/s)

Top width

(ft)

Wetted

perimeter

(ft)

Average

depth

(ft)

Average 

velocity

(ft/s)

Notes

25.9 44 20 20.77 -- -- Bankfull discharge.

14.4 -- 19.64 0.75 1 Meets 3-of-3 criteria.

.18 -- 16.25 .2 .06 Meets 2-of-3 criteria.

.5 -- 17.38 .27 .11 Meets wetted-perimeter criteria.

51.9 44 21.45 21.74 -- -- Bankfull discharge.

10.1 -- 18.67 .55 1 Meets 3-of-3 criteria.

.4 -- 12.45 .22 .15 Meets 2-of-3 criteria.

60.8 44 21.18 21.48 -- -- Bankfull discharge.

8.1 -- 19.43 .42 1 Meets 3-of-3 criteria.

1.2 -- 17.27 .21 .34 Meets 2-of-3 criteria.

68.7 44 23.09 23.3 -- -- Bankfull discharge.

10.4 -- 21.3 .49 1 Meets 3-of-3 criteria.

.9 -- 18.1 .23 .22 Meets 2-of-3 criteria.

81.6 44 25.05 25.62 -- -- Bankfull discharge.

11.5 -- 23.59 .5 1 Meets 3-of-3 criteria.

2 -- 20.74 .25 .39 Meets 2-of-3 criteria.

2 -- 20.74 .25 .39 Meets wetted-perimeter criteria.

Fort Meadow Brook near Hudson

The study site on Fort Meadow Brook (fig. 8) is 1,350 ft 

upstream of the Shay Street culvert in Hudson, MA. Five cross 

sections were surveyed on July 29, 2002, along a 90-ft reach. 

The streambed is primarily cobble with some overlying gravel. 

The cross sections are roughly trapezoidal in shape. The stream 

banks along the channel have rich organic bank material with 

large pine trees along both sides. The left bank is primarily lawn 

under the pine trees with patches of shrub vegetation along the 

right bank. The stream has a moderate slope. The water surface 

drops about 0.6 ft along the study reach for all measured flows 

between 0.84 ft3/s and 6.8 ft3/s. A HEC-RAS model was calibrated to simulate a subcritial flow regime by using the standard 

upstream-step energy method as documented in Appendix 1. 

The model calibration accuracy was 0.01 ft over the entire 

modeled reach for all the measured discharges.

The R2Cross analysis to determine the required 

streamflow for habitat protection was based upon the HECRAS simulation results for the cross section at river station 

133.7 (tables 3 and 4). The hydraulic characteristics that met the 

R2Cross 3-of-3 and 2-of-3 criteria requirements from the calibrated model are summarized in table 9. The cross section at 

river station 133.7 was identified as being the critical section 

in the riffle reach. The limiting R2Cross criterion for 3-of-3 

criteria was the average velocity and the limiting criterion for 

2-of-3 criteria was average depth.

Relations between wetted perimeter and discharge and 

between altitude of the water surface and wetted perimeter were 

determined for cross sections at river station 133.7 on the basis 

of the HEC-RAS simulations for a range of discharges up to 

bankfull flow. The discharge identified by the WettedPerimeter method as required for habitat protection during the 

summer period is presented in table 5. The hydraulic parameters 

associated with this discharge are summarized in table 9.
18 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Figure 8. Fort Meadow Brook near Hudson, Massachusetts, 

upstream view.

Table 9. Hydraulic characteristics at critical cross sections meeting R2Cross and Wetted-Perimeter method criteria for habitat 

protection at Fort Meadow Brook near Hudson, Massachusetts.

[ft, foot; ft3/s, cubic foot per second; ft/s, foot per second; --, not applicable]

River

station

Discharge

(ft3/s)

Top width

(ft)

Wetted

perimeter

(ft)

Average

depth

(ft)

Average 

velocity

(ft/s)

Notes

133.7 10 19.17 19.57 -- -- Bankfull discharge.

7.3 -- 19.18 0.38 1 Meets 3-of-3 criteria.

2.2 -- 17.54 .20 .63 Meets 2-of-3 criteria.

1.7 -- 16.57 .17 .60 Meets wetted-perimeter criteria.
Streamflow Requirements for Aquatic Habitat Protection 19

Elizabeth Brook near Stow

The riffle reach studied on Elizabeth Brook (fig. 9) is just 

downstream of a ford about 0.2 mi south of White Pond Road 

on an unnamed road in Stow. Six cross sections were surveyed 

on September 27, 2001, in this study reach; all were included in 

the water-surface-profile model. The cross sections were along 

a 70-ft length of riffle. The channel bends slightly to the right 

and is predominantly trapezoidal in shape. There are shrubs 

along both banks and larger deciduous trees further from the 

channel banks. The bed material is primarily gravel and 

cobbles. Bank material is a mixture of rich organic soil and 

cobbles. The reach has a moderate slope and the water surface 

dropped 0.7 ft to 1.1 ft along the study reach at the measured 

discharges, which ranged from 1.8 ft3/s to 50.1 ft3/s. The model 

was run as a subcritical flow regime by using the standard 

upstream-step energy method as documented in Appendix 1. 

The calibration accuracy was 0.02 ft over the entire modeled 

reach for all the measured discharges.

The R2Cross analysis was based upon the HEC-RAS 

simulation results for cross sections at river stations 202.05, 

213.57, 229.45, and 241.46 (tables 3 and 4). The hydraulic 

characteristics that met the R2Cross 3-of-3 and 2-of-3 criteria 

requirements from the calibrated model are summarized in 

table 10. The cross section at river stations 202.05, 213.57, 

229.45, and 241.46 were identified as being critical because 

they are upstream of the point where the riffle is influenced by 

backwater. The limiting R2Cross criteria for 3-of-3 criteria 

were the average depth at sections 202.05, 229.45, and 241.46 

and average velocity at section 213.57. Average velocity 

was the limiting criterion for 2-of-3 criteria at sections 202.05, 

229.45, and 241.46 and average depth was limiting at section 

213.57.

The 3-of-3 R2Cross results (table 3) range from ranged 

from 9 to 12 ft3/s for four cross sections modeled. This range in 

discharges is smaller than the 3-of-3 R2Cross results reported 

by Parker and Armstrong (2001) for the same cross sections 

(7.4 to 15.0 ft3/s). The HEC-RAS model used for this report was 

calibrated from a larger number of measurements made over a 

greater range of discharges.

Relations between wetted perimeter and discharge and 

between altitude of the water surface and wetted perimeter were 

determined for cross sections at stations 202.05, 213.57, 

229.45, and 241.46 on the basis of the HEC-RAS simulations 

for a range of discharges up to bankfull flow. The discharges 

identified by the Wetted-Perimeter method as required for 

habitat protection during the summer period are summarized in 

table 5. The hydraulic parameters associated with these 

discharges are summarized in table 10. The range of discharges 

in table 5 for Elizabeth Brook is about the same as reported in 

the preliminary estimates reported by Parker and Armstrong 

(2001).

Figure 9. Elizabeth Brook near Stow, Massachusetts, downstream view.
20 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Table 10. Hydraulic characteristics at critical cross sections meeting R2Cross and Wetted-Perimeter method criteria for habitat 

protection at Elizabeth Brook near Stow, Massachusetts.

[ft, foot; ft3/s, cubic foot per second; ft/s, foot per second; --, not applicable]

River

station

Discharge

(ft3/s)

Top width

(ft)

Wetted

perimeter

(ft)

Average

depth

(ft)

Average 

velocity

(ft/s)

Notes

202.50 40.4 31.67 32.04 -- -- Bankfull discharge.

10 -- 22.24 0.32 1.4 Meets 3-of-3 criteria.

5 -- 20.79 .24 1 Meets 2-of-3 criteria.

3.5 -- 20.27 .20 .86 Meets wetted-perimeter criteria.

213.57 40.4 27.54 28.15 -- -- Bankfull discharge.

9 -- 1 .35 1 Meets 3-of-3 criteria.

6 -- 26.05 .28 .82 Meets 2-of-3 criteria.

1.8 -- 24.93 .17 .43 Meets wetted-perimeter criteria.

229.45 40.4 26.78 27.01 -- -- Bankfull discharge.

10.5 -- 23.17 .27 1.67 Meets 3-of-3 criteria.

3.6 28.81 19.84 .18 1 Meets 2-of-3 criteria.

5.5 -- 22.13 .20 1.27 Meets wetted-perimeter criteria.

241.46 40.4 23.09 29.21 -- -- Bankfull discharge.

12 -- 26.13 .29 1.07 Meets 3-of-3 criteria.

10.2 -- 25.92 .28 1 Meets 2-of-3 criteria.

3.0 -- 24.51 .20 .61l Meets wetted-perimeter criteria.

Nashoba Brook at West Concord

The riffle section studied on Nashoba Brook (fig. 10) is 

about 110 ft downstream of the bridge under Commonwealth 

Avenue in West Concord. Four cross sections were surveyed on 

August 5, 2002, in this study reach, all of which were included 

in the water-surface-profile model. The cross sections were 

along a 130-ft length of riffle habitat and were predominantly 

trapezoidal in shape. The channel takes a shallow bend to the 

left along the study reach. There are scattered trees and shrubs 

along the left bank with a vertical stone-and-concrete wall along 

the right bank. The bed material is primarily cobbles, and the 

left bank material is composed of rich organic soil, silt, sand, 

and cobbles. The stream has a moderate slope. The water 

surface drops about 0.7 to 0.3 ft along the study reach for all 

measured flows ranging from 1.0 ft3/s and 74.9 ft3/s. A HECRAS model was calibrated to simulate a subcritial flow regime 

by using the standard upstream-step energy method as documented in Appendix 1. The calibration accuracy was 0.01 ft 

over the entire modeled reach for all the measured discharges.

The R2Cross analysis to determine the required 

streamflow for habitat protection was based upon the HECRAS model results for the cross sections at river stations 120.3, 

142.5, and 164.5 (tables 3 and 4). The hydraulic characteristics 

that met the R2Cross 3-of-3 and 2-of-3 criteria requirements 

from the calibrated model are summarized in table 11. The cross 

sections at river stations 120.3, 142.5, and 164.5 were identified 

as being the critical sections in the riffle reach. The limiting 

R2Cross criteria for 3-of-3 criteria were the average depth at 

section 120.3 and average velocity at sections 142.5 and 164.5. 

Average velocity was the limiting criterion for 2-of-3 criteria at 

section 120.3 and average depth was limiting at sections 142.5 

and 164.5.

Relations between wetted perimeter and discharge and 

between altitude of the water surface and wetted perimeter 

were determined for cross sections at stations 120.3, 142.5, and 

164.5 on the basis of the HEC-RAS simulations for a range of 

discharges up to bankfull flow. The discharges identified by the 

Wetted-Perimeter method as required for habitat protection 

during the summer period are summarized in table 5. The 

hydraulic parameters associated with these discharges are 

summarized in table 11.

Resulting normalized discharges estimated by The 

R2Cross and Wetted-Perimeter methods as needed to protect 

habitat are significantly less than the results from the other 

study sites (tables 3, 4, and 6). The wall on the right bank, which 

is on the outside of the channel bend, restricted the natural 

movement of the channel in that direction. The results for this 

site were not included in any subsequent analyses.
Streamflow Requirements for Aquatic Habitat Protection 21

Figure 10. Nashoba Brook at West Concord, Massachusetts, downstream view.

Table 11. Hydraulic characteristics at critical cross sections meeting R2Cross and Wetted-Perimeter method criteria for habitat 

protection at Nashoba Brook at West Concord, Massachusetts.

[ft, foot; ft3/s, cubic foot per second; ft/s, foot per second; --, not applicable]

River

station

Discharge

(ft3/s)

Top width

(ft)

Wetted

perimeter

(ft)

Average

depth

(ft)

Average 

velocity

(ft/s)

Notes

120.3 150 27.36 29.58 -- -- Bankfull discharge.

7.1 -- 22.32 0.27 1.19 Meets 3-of-3 criteria.

5.2 -- 22.23 .24 1 Meets 2-of-3 criteria.

7.0 -- 22.25 .25 1.26 Meets wetted-perimeter criteria.

142.5 150 26.53 28.59 -- -- Bankfull discharge.

6.8 -- 23.38 .29 1 Meets 3-of-3 criteria.

5.5 -- 23.29 .27 .89 Meets 2-of-3 criteria.

5 -- 23.25 .26 .85 Meets wetted-perimeter criteria.

164.5 150 25.73 28.02 -- -- Bankfull discharge.

5.8 -- 19.17 .30 1 Meets 3-of-3 criteria.

4.2 -- 18.72 .26 .88 Meets 2-of-3 criteria.

4 -- 18.64 .25 .86 Meets wetted-perimeter criteria.
22 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Charles River near Hopkinton

The riffle section studied on the Charles River in 

Hopkinton (fig. 11) is about 300 ft downstream of the Echo 

Lake Dam, which regulates the flow through the study section, 

and 3,450 ft upstream of State Route 85 culvert in Milford. 

Seven cross sections were surveyed on August 2, 2001, all of 

which were included in the water-surface-profile model. The 

cross sections were along a 90-ft length of pool and riffle 

habitats and were predominantly trapezoidal in shape. The 

channel takes a shallow meander starting with a bend to the 

right along the study reach. There are scattered trees and shrubs 

along both banks, the bed material is primarily cobbles, and the 

bank material is composed of organic soil, silt, sand, and 

cobbles. The stream has a moderately steep slope. The channel 

in this river section was frequently dry during the period of this 

study. The water surface drops about 1.6 ft to 1.1 ft along the 

study reach for all measured flows ranging from 0.03 ft3/s and 

8.4 ft3/s. A HEC-RAS model was calibrated to simulate a 

subcritial flow regime by using the standard upstream-step 

energy method as documented in Appendix 1. The calibration 

accuracy was 0.01 ft over the entire modeled reach for all the 

measured discharges.

The R2Cross analysis to determine the required streamflow for habitat protection was based upon the HEC-RAS 

model results for the cross section at river stations 101.39, 

157.84, and 166.01 (tables 3 and 4). The hydraulic characteristics from the calibrated model used to meet the R2Cross 3-of3 and 2-of-3 criteria requirements are summarized in table 12. 

The cross sections at river stations 101.39, 157.84, and 166.01 

were identified as being critical. The limiting R2Cross criterion 

for 3-of-3 criteria was the average velocity and wetted 

perimeter was the limiting criterion for 2-of-3 criteria.

Relations between wetted perimeter and discharge and 

between altitude of the water surface and wetted perimeter were 

determined for cross sections at stations 101.39 and 166.01 on 

the basis of the HEC-RAS simulations for a range of discharges 

up to bankfull flow. The discharges identified by the WettedPerimeter method as required for habitat protection during the 

summer period are summarized in table 5. The hydraulic 

parameters associated with these discharges are summarized in 

table 12.

Figure 11. Charles River near Hopkinton, Massachusetts, upstream view.
Streamflow Requirements for Aquatic Habitat Protection 23

Table 12. Hydraulic characteristics at critical cross sections meeting R2Cross and Wetted-Perimeter method criteria for habitat 

protection at Charles River near Hopkinton, Massachusetts.

[ft, foot; ft3/s, cubic foot per second; ft/s, foot per second; --, not applicable]

River

station

Discharge

(ft3/s)

Top width

(ft)

Wetted

perimeter

(ft)

Average

depth

(ft)

Average 

velocity

(ft/s)

Notes

101.39 8.4 11.69 12.04 -- -- Bankful discharge.

2.2 -- 7.16 0.33 1 Meets 3-of-3 criteria.

.21 -- 6.02 .22 .17 Meets 2-of-3 criteria.

.2 -- 5.98 .22 .16 Meets wetted-perimeter criteria.

157.84 8.4 10.79 11.49 -- -- Bankful discharge.

2.0 -- 6.04 .35 1 Meets 3-of-3 criteria.

.38 -- 5.74 .34 .21 Meets 2-of-3 criteria.

166.01 8.4 14.74 15.04 -- -- Bankful discharge.

2.7 -- 10.96 .28 1 Meets 3-of-3 criteria.

.22 -- 7.52 .26 .12 Meets 2-of-3 criteria.

.45 -- 10.18 .23 .21 Meets wetted-perimeter criteria.

Mine Brook near Franklin

The riffle section on Mine Brook (fig. 12) is about 680 ft 

upstream of a culvert under Route 140 in the town of Franklin. 

Seven cross sections were surveyed on August 8, 2001, along an 

87-ft length of riffle habitat and all were included in the watersurface-profile model. The predominantly trapezoidal cross 

sections are in a straight reach of riffle channel. The reach flows 

through a forest of large deciduous trees and a few scattered 

shrubs line both banks. The bed material is primarily cobbles 

and the bank material is a mixture of organic soil and cobbles. 

The water surface dropped 0.7 to 1.10 ft along the study reach 

at measured discharges ranging from 2.03 ft3/s to 70 ft3/s. A 

HEC-RAS model was calibrated to simulate a subcritial flow 

regime by using the standard upstream-step energy method 

as documented in Appendix 1. The calibration accuracy was 

0.01 ft over the entire reach for measured discharges.

The R2Cross analysis was applied on the basis of the 

HEC-RAS model results for the cross sections at river stations 

112.91, 123.60, 143.62, 164.85, 173.65, and 187.25 (tables 3 

and 4). The hydraulic characteristics from the calibrated model 

used to meet the R2Cross 3-of-3 and 2-of-3 criteria requirements are summarized in table 13. The cross sections at all six 

river stations were identified as being critical. The limiting 

R2Cross criterion for 3-of-3 criteria was average velocity. 

Average depth was the limiting 2-of-3 criterion at stations 

112.91, 123.60, 143.62, 173.65, and 187.25 and wetted 

perimeter was limiting at station 164.85.

The 3-of-3 R2Cross results (table 3) ranged from 2.5 to 

9 ft3/s for the six cross sections modeled. This range of 

discharges is smaller than the 3-of-3 results reported by Parker 

and Armstrong (2001) for four cross-sections (2.4 to 8.75 ft3/s). 

The HEC-RAS model used for this report was calibrated from a 

larger number of measurements made over a greater range of 

discharges than the model used by Parker and Armstrong 

(2001).

Relations between wetted perimeter and discharge and 

between altitude of the water surface and wetted perimeter were 

determined for cross sections at stations 112.91, 123.60, 

143.62, 164.85, 173.65, and 187.25 on the basis of the HECRAS simulations for a range of discharges up to bankfull flow. 

The discharges identified by the Wetted-Perimeter method as 

required for habitat protection during the summer period as are 

summarized in table 5. The hydraulic parameters associated 

with these discharges are summarized in table 13. The 

discharges in table 5 for Mine Brook range from 2.1 to 6.5 ft3/s 

for six cross sections modeled. These discharges are greater 

than the discharges reported in the preliminary estimates 

reported by Parker and Armstrong (2001) for four cross sections 

(1.0 to 5.2 ft3/s). The four cross-sections analyzed in the Parker 

and Armstrong (2001) report are included in the six cross 

sections analyzed in this report. The current results are more 

than 0.1 ft3/s/mi2 higher than the results in the preliminary 

report.
24 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Figure 12. Mine Brook near Franklin, Massachusetts, downstream view.

Table 13. Hydraulic characteristics at critical cross sections meeting R2Cross and Wetted-Perimeter method criteria for habitat 

protection at Mine Brook near Franklin, Massachusetts.

[ft, foot; ft3/s, cubic foot per second; ft/s, foot per second; --, not applicable]

River

station

Discharge

(ft3/s)

Top width

(ft)

Wetted

perimeter

(ft)

Average

depth

(ft)

Average 

velocity

(ft/s)

Notes

112.91 48 24.91 25.34 -- -- Bankful discharge.

9 -- 21.95 0.41 1 Meets 3-of-3 criteria.

2.3 -- 18.00 .25 .52 Meets 2-of-3 criteria.

5.8 -- 20.99 .33 .84 Meets wetted-perimeter criteria.

123.60 48 18.90 19.95 -- -- Bankful discharge.

7 -- 16.54 .43 1 Meets 3-of-3 criteria.

.8 -- 10.46 .20 .39 Meets 2-of-3 criteria.

5.2 -- 15.52 .37 .92 Meets wetted-perimeter criteria.

143.62 48 17.49 18.26 -- -- Bankful discharge.

6.2 -- 15.11 .41 1 Meets 3-of-3 criteria.

1.1 -- 12.23 .20 .45 Meets 2-of-3 criteria.

6.2 -- 15.08 .41 1 Meets wetted-perimeter criteria.

164.85 48 14.94 16.42 -- -- Bankful discharge.

4.2 -- 12.98 .33 1 Meets 3-of-3 criteria.

1.1 -- 8.21 .27 .51 Meets 2-of-3 criteria.

6.5 -- 14.46 .40 1.17 Meets wetted-perimeter criteria.

173.65 48 16.38 17.96 -- -- Bankful discharge.

2.5 -- 11.64 .22 1 Meets 3-of-3 criteria.

1.9 -- 10.25 .20 .93 Meets 2-of-3 criteria.

5.6 -- 11.97 .22 1.32 Meets wetted-perimeter criteria.

187.25 48 20.79 21.66 -- -- Bankful discharge.

8.2 -- 19.40 .44 1 Meets 3-of-3 criteria.

3.8 -- 18.88 .21 .67 Meets 2-of-3 criteria.

2.2 -- 18.78 .28 .43 Meets wetted-perimeter criteria.
Streamflow Requirements for Aquatic Habitat Protection 25

Charles River at Medway

Two riffle sections were studied along a 1,500 ft reach 

upstream of the streamflow-gaging station at Charles River at 

Medway (01103200). The first riffle is at the upstream end of 

the reach and the downstream riffle is about 600 ft upstream of 

the Walker Street Bridge (fig. 13). The survey of 11 crosssections in this study reach was completed between July and 

September, 2001. Nine cross-sections were included in a single 

water-surface-profile model spanning the river length from 

Walker Street Bridge to the upstream riffle; the cross sections at 

river stations 641.1 and 691.6 were at the downstream riffle and 

those at river stations 1466.3, 1481.8, and 1498.9 were at the 

upstream riffle. The riffle cross sections are predominantly 

trapezoidal in shape. The channel takes several shallow bends 

along the course of the study reach. The vegetation along the 

southern banks of the reach includes large hemlocks, with 

deciduous trees, small shrubs, and lawn along the northern side. 

The bed material is primarily gravel; the bank material is a 

mixture of organic soil, silt, sand, and cobbles. The surveyed 

water surface dropped 2.49 ft along the study reach at 8.2 ft3/s 

and 2.14 ft at 76.2 ft3/s. A HEC-RAS model was calibrated 

to simulate a subcritial flow regime by using the standard 

upstream-step energy method as documented in Appendix 1 at 

the end of this report. The calibration accuracy was 0.10 ft over 

the entire reach for measured discharges.

The R2Cross analysis to determine streamflow requirements for habitat protection was based upon the HEC-RAS 

simulation results for the cross sections at river station 691.6 in 

the downstream study riffle and at river stations 1481.8 and 

1498.9 in the upstream riffle (tables 3 and 4). The hydraulic 

characteristics from the calibrated model that met the R2Cross 

3-of-3 and 2-of-3 criteria requirements for both the upstream 

and downstream riffle reaches are summarized in table 14. For 

the downstream riffle, the cross section at river station 691.6 

was identified as being the critical because it is upstream of the 

point where the riffle is influenced by backwater. The upstream 

cross sections at river stations 1481.8 and 1498.9 are upstream 

of the influence of backwater. The limiting R2Cross criterion

for 3-of-3 criteria was the average depth at the study sections for 

both riffle reaches. Average velocity was limiting for 2-of-3 

criteria at the study sections for both riffle reaches. The results 

have not changed from the results presented in the preliminary 

report (Parker and Armstrong, 2001).

Relations between wetted perimeter and discharge and 

between altitude of the water surface and wetted perimeter were 

determined for the cross section at river station 691.6 in the 

downstream study riffle and at river stations 1481.8 and 1498.9 

in the upstream riffle. The relations were developed on the basis 

of the HEC-RAS simulations for a range of discharges up to 

bankfull flow. The HEC-RAS model used in the WettedPerimeter method analysis was not changed from the model 

presented by Parker and Armstrong (2001). However, the 

output for the model was analyzed by using the WettedPerimeter methods presented in this report. The discharges 

identified by the Wetted-Perimeter method as required for 

habitat protection during the summer period for both riffle 

reaches are summarized in table 5. These discharges are 

different from those presented by Parker and Armstrong (2001). 

The hydraulic parameters associated with these discharges are 

summarized in table 14.

Table 14. Hydraulic characteristics at critical cross sections meeting R2Cross and Wetted-Perimeter method criteria for habitat 

protection at Charles River at Medway, Massachusetts.

[ft, foot; ft3/s, cubic foot per second; ft/s, foot per second; --, not applicable]

River

station

Discharge

(ft3

/s)

Top width

(ft)

Wetted

perimeter

(ft)

Average

depth

(ft)

Average 

velocity

(ft/s)

Notes

691.6 172 61.39 62.51 -- -- Bankful discharge.

57 -- 58.7 0.61 1.59 Meets 3-of-3 criteria.

21.6 -- 56.52 .39 1 Meets 2-of-3 criteria.

8.7 -- 54.98 .24 .67 Meets wetted-perimeter criteria.

1,481.8 172 53.41 53.73 -- -- Bankful discharge.

45.4 -- 41.00 .53 2.08 Meets 3-of-3 criteria.

8 -- 30.40 .26 1 Meets 2-of-3 criteria.

16.5 -- 34.27 .33 1.45 Meets wetted-perimeter criteria.

1,498.9 172 58.02 59.40 -- -- Bankful discharge.

52.8 -- 45.91 .58 2.03 Meets 3-of-3 criteria.

11.6 -- 35.50 .33 1 Meets 2-of-3 criteria.

7.7 -- 34.66 .31 .73 Meets wetted-perimeter criteria.
26 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

A.

B.

Figure 13. Charles River at Medway, Massachusetts, downstream views of the study reaches: 

A, the upstream riffle; and B, the downstream riffle.
Fish-Community Sampling and Assessment 27

Fish-Community Sampling and 

Assessment

Fish-community assessments involve the sampling and 

description of fish species to indicate the ecological condition 

of a river. Fish-community data used in this report were 

collected in the Assabet and Charles River Basins between 

August 1999 and September 2002 by the Massachusetts 

Division of Fisheries and Wildlife (MDFW) as part of the 

MDFW Statewide Fisheries Assessment Program. Fishcommunity data were also collected in the Charles River Basin 

during August of 2002 by the Massachusetts Department of 

Environmental Protection (MADEP), Division of Watershed 

Management, as part of the MADEP Charles River Watershed 

Monitoring Program. Fish were sampled during summer 

periods of low to moderate streamflow because fish assemblages during summer are relatively stable and contain the full 

range of resident species (Gibson and others, 1996). Biological 

monitoring in this study targeted fish because they are longlived and are sensitive to a wide range of stresses. In comparison to macroinvertebrates, fish are easy to identify, and the 

relations between fish and stream health are better understood 

and valued by the public. In addition, streamflows adequate to 

maintain fisheries are usually sufficient to maintain macroinvertebrates and other aquatic life. A disadvantage of using fish 

to indicate flow degradation is that fish integrate the effects of 

many stresses; thus, it is difficult to determine the effect of each 

stress.

The fish-community assessment was designed to characterize the diversity and relative abundance of fish species, and 

the length-frequency distribution of fish in the Charles and 

Assabet Basins. Sampling reaches were distributed over the 

length of the main stem and tributaries of the Charles and 

Assabet Basins. Sampling reaches included at least 300 ft of 

stream length, where possible. Fish were sampled by electrofishing with pulsed direct current (DC) backpack units and 

barges (Massachusetts Division of Fisheries and Wildlife, 

written commun., 2003) (fig. 14). Backpack electrofishing units 

are best used in small or shallow streams and were appropriate 

for sampling most tributary and headwater reaches of the 

Assabet and Charles Rivers. Barge electrofishing units are best 

used in wadeable reaches where a stronger power supply and 

more labor for electrofishing are required. Barge units were 

appropriate for sampling many of the free-flowing reaches of 

the main stems of the Assabet and Charles Rivers.

Fish sampled in this study were classified on the basis of 

their habitat use. Fish communities were compared to a target 

fish community developed for the Quinebaug River (Bain and 

Meixler, 2000). The Quinebaug target fish community (fig. 15) 

can be used to represent a healthy fish community for larger 

streams and smaller rivers in the region. Habitat-use categories 

developed for the Quinebaug River have been used to assess 

fish communities in other river basins in Massachusetts and 

Rhode Island (table 15) (Armstrong and others, 2001; 

Armstrong and Parker, 2003).

Fish were classified into three macrohabitat classes on the 

basis of their habitat use: macrohabitat generalists, fluvial 

dependents, and fluvial specialists (Bain and Knight, 1996, 

Bain and Meixler, 2000). Macrohabitat generalists, such as 

pumpkinseed and redfin pickerel, are fish species that use a 

broad range of habitat. They include species commonly found 

in lakes, reservoirs, and streams, and can complete their life 

cycle in any one of these systems. Fluvial dependents, such 

as white sucker, require access to streams or flowing-water 

habitats for a specific life stage, but otherwise are commonly 

found in lakes, reservoirs, and streams. Fluvial specialists, such 

as blacknose dace and creek chubsucker, are almost always 

reported in streams or rivers and require flowing-water habitats 

throughout their life cycle (Bain and Travnichek, 1996).

Fish can live in different habitat conditions in different 

geographic areas. For example, in Massachusetts, fish that 

require cold or well-oxygenated water are found primarily in 

flowing streams. Therefore, for the purposes of this study, the 

Quinebaug target fish community was modified from Bain and 

Melch (2000) to accommodate for regional differences in 

habitat requirements. The Creek chub were reclassified from a 

macrohabitat generalists to a fluvial specialist based on their 

habitat used in Massachusetts streams. The American eel, a 

catadromous fish that requires access to stream habitats 

for a portion of its life cycle, was reclassified from a fluvial 

dependent to a macrohabitat generalist because it occupies a 

wide range of habitats during the portion of its life cycle in 

freshwater streams. Stocked rainbow trout, brown trout, and 

brook trout (as opposed to the wild trout found in the samples), 

were not included in the fish-community analysis. Trout 

captured in waters not stocked with trout were considered wild. 

Trout captured in cold water streams were categorized as wild 

or stocked based on fish size (trout less than 0.5 ft are not 

stocked) and species.
28 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Figure 14. Massachusetts Division of Fisheries and Wildlife personnel barge electrofishing for the 

fish-community assessment.

25 %

25 %

50 %

TARGET FISH COMMUNITY

MACROHABITAT GENERALIST

FLUVIAL DEPENDENT

FLUVIAL SPECIALIST

Figure 15. Target fish community for the 

Quinebaug River, Massachusetts (modified from 

Bain and Meixler, 2000).
Fish-Community Sampling and Assessment 29

1A location along the named watershed with a drainage area greater than 30 square miles.

2Modified from Bain and Meixler (2000).

3Tributary site, a location in the watershed with a drainage area less than 30 square miles.

Table 15. Percentages of fish in each habitat-use classification sampled in flowing reaches of several river basins in Massachusetts.

[ --, target percentage has not been developed]

Habitat-use

classification

Watershed

Quinebaug Westfield Shawsheen Blackstone Nashua Assabet Charles Housatonic Ipswich

Main-Stem Site1

Macrohabitat generalist species 36.4 22.1 92.1 36.1 30.2 50.4 98.1 70.1 97.0

Fluvial-dependent species 36.2 28 1.2 58.8 32 23.7 1.7 12.9 1.5

Fluvial-specialist species 27.4 49.9 6.7 5.1 37.8 25.9 .2 17 1.5

Taget for Main-Stem Reaches2

Macrohabitat generalist species 25 -- -- -- -- -- -- -- --

Fluvial-dependent species 25 -- -- -- -- -- -- -- --

Fluvial-specialist species 50 -- -- -- -- -- -- -- --

Tributary Site3

Macrohabitat generalist species 8.4 4.6 70.4 24.4 8.1 49.4 87.6 13.6 75.9

Fluvial-dependent species 21.3 5.4 7.7 35.0 21.2 17.3 8.5 12.3 2.6

Fluvial-specialist species 70.3 90 21.9 40.6 70.7 33.3 3.9 74.1 21.5

Fish-sampling information and community assessments 

were categorized by basin size and free-flowing status. Reaches 

with drainage areas of greater than 30 mi2 were classified as 

main-stem reaches (M. Anderson and A. Olivero, The Nature 

Conservancy, written commun., 2003). Reaches with drainage 

areas less than 30 mi2 were classified as tributary or headwater 

reaches. Only the fish-community data from the main-stem 

reaches were directly compared to the Quinebaug River target 

fish communities. The Quinebaug River target fish-community 

was developed for the main stem between the outlet of the East 

Brimfield Reservoir and the Massachusetts–Connecticut State 

boundary. Data gathered from tributaries were also used to 

illustrate their degree of degradation in comparison to target 

fish communities. Although fish information gathered on tributaries has not often been published in terms of target fish communities, several characteristics of tributary fish communities 

makes the comparison valid, with certain limitations. For 

example, tributary sites are expected to have a higher proportion 

of fluvial-fish species than main-stem reaches (M.B. Bain, 

Cornell University, oral commun., 2003); in particular, the 

riffle reaches included in this study should be composed nearly 

exclusively of fluvial fish under restored conditions. Most of the 

habitat in these riffle reaches is unsuitable for macrohabitat 

generalists.

Analysis conducted by using recent fish collections in the 

Quinebaug, Blackstone, Westfield, Nashua, Housatonic, and 

Shawsheen Rivers (table 15) strongly indicates that tributaries 

should have a higher percent of fluvial fish than their corresponding main-stem reaches. In all cases, main-stem samples 

consisted of considerably higher percentages of macrohabitat 

generalists than their tributaries. Even the most impaired rivers, 

such as the Ipswich, exhibited this trend. Under restored conditions (as represented by the target fish community proportions 

developed for the Quinebaug River Basin), the tributaries 

should exhibit a higher proportion of fluvial fish than the main 

stem. Conservatively, for the purpose of this report, tributary 

fish communities will be considered degraded if the proportion 

of macrohabitat generalists is greater than 25 percent.

Sampling Results

Fish communities from a range of habitat types were 

assessed to characterize fish-species diversity, relative abundance, and length-frequency distribution in the Assabet and 

Charles River Basins. To assess anthropogenic effects on the 

fish community, the composition of the fish communities in the 

Assabet and Charles River systems was compared to a target 

fish community developed for the Quinebaug River (Bain and 

Meixler, 2000) as well as to the fish communities in other river 

basins in Massachusetts.
30 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Assabet River Basin Sampling

From 1999 to 2001, 1,980 fish of 22 different species were 

collected at 33 free-flowing sites in the Assabet River Basin 

(fig. 16). In the main stem of the Assabet River, from June 2000 

to August 2001, 781 fish of 22 different species (table 16) were 

collected from 6 sites. The electrofishing effort included a total 

length of more than 2,470 ft of stream, with site lengths ranging 

from 325 to 570 ft.

In the tributaries and headwaters, 1,199 fish of 17 different 

species were collected from 27 sites between August 1999 and 

August 2000. The electrofishing effort included a length of 

more than 8,800 ft of stream, with site lengths ranging from 170 

to 650 ft. The 27 sites included 3 from the Assabet River headwaters (these sites have contributing areas of 30 mi2 or less), 

and 14 from tributaries, including Assabet Brook, Cold Harbor 

Brook, Elizabeth Brook, Fort Meadow Brook, Great Brook, 

Guggins Brook, Hog Brook, Hop Brook, Mill Brook, Nashoba 

Brook, North Brook, Spencer Brook, and 2 unnamed 

tributaries.

Charles River Basin Sampling

Between 2000 and 2002, 1,025 fish of 19 different species 

were collected at 11 free-flowing sites in the Charles River 

Basin (fig. 16). In the main stem of the Charles River, 639 fish 

of 16 different species were collected from 4 sites (table 16). 

From September 2001 to August 2002, four fish collections 

were made. The electrofishing effort included a total length of 

more than 2,350 ft of stream, with site lengths ranging from 260 

to 1,190 ft.

In 9 tributaries and in the headwaters, 386 fish of 16 

different species were collected from 16 sites. From August 

2000 to September 2002, 16 fish collections were made. 

The electrofishing effort included a total length of more than 

2,620 ft of stream, with site lengths ranging from 325 to 552 ft. 

In addition to the Charles River headwaters, tributaries sampled 

include Beaver Brook, Cherry Brook, Chicken Brook, Fuller 

Brook, Hopping Brook, Mine Brook, Stony Brook, Stop River, 

and Trout Brook.

Fish-Community Assessment

In accordance with habitat-use classifications used in this 

report, fish species sampled in the Assabet and Charles River 

main stems were divided into one of three macrohabitat classes: 

macrohabitat generalists, fluvial dependents, and fluvial specialists. Stocked fish previously described were removed from 

the count at this stage of the analysis. Fish in the free-flowing 

reaches of the Assabet River main stem consisted of 52.9 percent macrohabitat generalists, 22.3 percent fluvial dependents, 

and 24.8 percent fluvial specialists (fig. 17). White sucker and 

American eel dominated the fish communities in the main stem, 

composing by number 24 and 10 percent of the main-stem 

samples, respectively. The remaining 20 species each made up 

less than 10 percent of the total number of fish collected. Fish 

in the free-flowing reaches of the Charles River main stem 

consisted of 98.3 percent macrohabitat generalists and 1.7 

percent fluvial dependents. No fluvial specialists were sampled 

in this reach. American eel (40 percent), redbreast sunfish (29 

percent), and bluegill (19 percent) dominated the fish communities in the main stem. The remaining 10 species each made up 

less than 10 percent of the total number of fish collected. In 

general, the Charles River is dominated by macrohabitat 

generalist species; fluvial species are rare or absent.

Habitat-use classifications for the main-stem Charles 

and Assabet River fish communities were compared to habitatuse classifications for target fish communities developed for 

the Quinebaug River, Massachusetts. Fish in the Quinebaug 

River target fish community with the classifications used in 

this report had a population consisting of 25 percent 

macrohabitat generalists, 25 percent fluvial dependents, and 

50 percent fluvial specialists (fig. 15). The percentages of 

fluvial fish species in the Charles River were considerably 

less than those in the Quinebaug target fish community (fig. 15 

and fig. 17). The fish community of the Assabet River main 

stem is less dominated by macrohabitat generalists and is less 

degraded than the fish community found in the Charles River 

(fig. 17).
Fish-Community Sampling and Assessment 31

42 ̊30'

43 ̊30'

42 ̊00'

72 ̊00' 71 ̊00'

Base from U.S. Geological Survey digital data,

Massachusetts State Plane, zone 4151,1991

1:25,000 series

ATLANTIC

OCEAN

Squannacook River near 

West Groton (01096000)

Sevenmile River near

Spencer (01175670)

STREAMFLOW-GAGING STATION AND NUMBER

EXPLANATION

BASIN BOUNDARY

FISH-SAMPLING SITES

Indian Head River near

Hanover, MA (01105730)

Branch River at Forestdale, RI (01111500)

Assabet

Charles

Beaver Brook near 

North Pelham, NH (010965852)

Old Swamp River

near South

Weymouth, MA (01105600)

(01175670)

0 50 MILES

0 50 KILOMETERS

CONNECTICUT

RHODE ISLAND

Boston

NEW HAMPSHIRE

MASSACHUSETTS

Providence

Nashua

Worchester

Methuen

Plymouth

Fitchburg

0 50 MILES

0 50 KILOMETERS

73 ̊00'

42 ̊30'

42 ̊00'

72 ̊00'

71 ̊00'

70 ̊00'

ATLANTIC OCEAN

Massachusetts

Bay

Nantucket

Sound

STUDY

BASINS

Figure 16. Location of fish-sampling sites and habitat study sites in the Charles and Assabet River Basins, Massachusetts.
32 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Table 16. Number of each species and percent of total number of fish collected in the main stem, tributaries, and headwaters of the 

Assabet and Charles River Basins, Massachusetts, by the Massachusetts Division of Fisheries and Wildlife from 1999 through 2001.

[Species: FD, Fluvial dependent species; FS, Fluvial specialist species; MG, Macrohabitat generalist species. <, actual value is less than value shown]

Habitat-use

classification

Number

collected Percent

Assabet River Basin

Mainstem

White sucker (FD) 185 24

American eel (MG) 75 10

Blacknose dace (FS) 74 9

Fallfish (FS) 74 9

Bluegill (MG) 72 9

Largemouth bass (MG) 58 7

Redbreast sunfish (MG) 56 7

Yellow bullhead (MG) 39 5

Redfin pickerel (MG) 25 3

Brown trout (FS) 20 3

Pumpkinseed (MG) 19 2

Golden shiner (MG) 17 2

Rainbow trout (FS) 16 2

Creek chubsucker (FS) 15 2

Spottail shiner (MG) 11 1

Yellow perch (MG) 8 1

Black crappie (MG) 6 < 1

Chain pickerel (MG) 4 < 1

Brown bullhead (MG) 2 < 1

Banded sunfish (MG) 2 < 1

Tiger trout (FS) 1 < 1

All species 780 100

Assabet River Basin—Continued

Tributaries and headwaters

White sucker (FD) 208 17

Blacknose dace (FS) 188 16

Brook trout (FS) 175 15

Pumpkinseed (MG) 133 11

Redfin pickerel (MG) 118 10

Golden shiner (MG) 75 6

Yellow bullhead (MG) 72 6

Chain pickerel (MG) 47 4

American eel (MG) 40 3

Largemouth bass (MG) 37 3

Bluegill (MG) 34 3

Brown bullhead (MG) 27 2

Fallfish (FS) 19 2

Brown trout (FS) 10 < 1

Creek cubsucker (FS) 7 < 1

Yellow perch (MG) 6 < 1

Banded sunfish (MG) 3 < 1

All species 1,199 100

Habitat-use

classification

Number

collected Percent
Fish-Community Sampling and Assessment 33

Table 16. Number of each species and percent of total number of 

fish collected in the main stem, tributaries, and headwaters of the 

Assabet and Charles River Basins, Massachusetts, by the 

Massachusetts Division of Fisheries and Wildlife from 1999 

through 2001.—Continued

[Species: FD, Fluvial dependent species; FS, Fluvial specialist species; MG, 

Macrohabitat generalist species. <, actual value is less than value shown]

Species Number

collected Percent

Charles River Basin

Mainstem

American eel (MG) 254 40

Redbreast sunfish (MG) 184 29

Bluegill (MG) 124 19

Pumpkinseed (MG) 27 4

Largemouth bass (MG) 14 2

White sucker (FD) 11 2

Smallmouth bass (MG) 4 < 1

White catfish (MG) 4 < 1

Yellow perch (MG) 4 < 1

Black crappie (MG) 3 < 1

Yellow bullhead (MG) 3 < 1

Chain pickerel (MG) 2 < 1

White perch (MG) 2 < 1

Brown bullhead (MG) 1 < 1

Brown trout (FS) 1 < 1

Golden shiner (MG) 1 < 1

All species 639 100

Charles River Basin—Continued

Tributaries and headwaters

Redfin pickerel (MG) 96 25

Yellow bullhead (MG) 91 24

Bluegill (MG) 65 17

White sucker (FD) 33 9

Largemouth bass (MG) 25 6

Redbreast sunfish (MG) 14 4

Brown bullhead (MG) 13 3

Pumpkinseed (MG) 12 3

Brook trout (FS) 10 3

Chain pickerel (MG) 8 2

Brown trout (FS) 5 1

Yellow perch (MG) 5 1

American eel (MG) 4 1

Golden shiner (MG) 2 < 1

Black crappie (MG) 1 < 1

Redfin/Chain pickerel 

hybrid (MG)

1 < 1

Swamp darter (MG) 1 < 1

All species 386 100

50.4 %

23.7 %

25.9 %

98.1 %

1.7 %

0.2 %

CHARLES RIVER,

MAIN STEM, FREE-FLOWING SITES,

2000–01

N=1,199

ASSABET RIVER,

MAIN STEM, FREE-FLOWING SITES,

2000–01

N=781

MACROHABITAT GENERALIST

FLUVIAL DEPENDENT

FLUVIAL SPECIALIST

A.

B.

Figure 17. Fish species habitat-use classifications: 

A, main-stem free-flowing sites on the Assabet River, 

2000–01; and B, main-stem free-flowing sites on the 

Charles River, 2000–01.
34 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Fish communities were sampled in two adjacent reaches 

on the Charles River main stem in Medway. High-gradient 

riffles and runs, good canopy cover and stable substrates dominated the upstream reach. Lower gradient, runs and pools, open 

canopy and sandy substrate dominated the downstream reach. 

The fish community in the upstream reach would be expected to 

be dominated by fluvial species that prefer high water velocities. The downstream reach had habitat suitable for generalist 

species, but would be expected to have the same fluvial species 

as in the upstream reach but in fewer numbers. The fish 

community in the downstream reach should more closely 

resemble the Quinebaug River target fish community. Both the 

upstream and downstream reaches, however, yielded fish populations heavily dominated by generalists (both greater than 95 

percent macrohabitat generalists). The higher proportion of 

generalists indicates that the fish community is degraded. The 

specific nature of this degradation could be caused by changes 

in physical habitat, impoundments, or a degradation of water 

quantity or quality.

Target fish communities have not been designed for tributaries and headwater reaches. The percentage of fluvial species 

in tributaries and headwaters is expected to be much higher than 

in the main-stem reaches of the corresponding river systems. 

The fish species compositions of the Assabet and Charles River 

tributaries and headwaters are considerably different. Fish in 

the free-flowing reaches of the Assabet River tributaries and 

headwaters consisted of 50.8-percent macrohabitat generalists, 

17.9-percent fluvial dependents, and 31.3-percent fluvial 

specialists. White sucker (17 percent), blacknose dace (16 

percent), brook trout (15 percent), pumpkinseed (11 percent), 

and redfin pickerel (10 percent) dominated the fish communities in the Assabet River tributaries and headwaters. The 

remaining 12 species each composed less than 10 percent of the 

total number of fish collected. Fish in the free-flowing reaches 

of the Charles River tributaries and headwaters consisted of 

88.9-percent macrohabitat generalists, 8.7-percent fluvial 

dependents, and 2.4-percent fluvial specialists. Redfin pickerel 

(25 percent), yellow bullhead (24 percent), and bluegill (17 

percent) dominated the fish communities in the Charles River 

tributaries and headwaters. The remaining 13 species each 

composed less than 10 percent of the total number of fish 

collected. These results indicate that the macrohabitat generalists compose a larger proportion of the fish community in the 

tributaries and main stem of the Charles River than would be 

expected in either basin.

Despite the apparent degraded state of the fish communities in the tributaries and headwaters of both river systems, the 

results do support the theory that tributary fish communities 

consist of a greater percentage of fluvial fish than the main-stem 

fish communities. In both basins, the tributaries have a higher 

percentage of fluvial species than the corresponding main-stem 

reaches.

Fish communities were also sampled in two headwater and 

tributary riffle sites in the Assabet River Basin. The two sites 

are the Assabet River near Westborough and Danforth Brook at 

Hudson, MA. The composite fish-community data for those 

two sites had almost the same percentage of generalist fish 

species than the percentage found in the composite of data for 

all the Assabet River tributary (54 percent versus 50.8 percent) 

sampling sites. These two sites are dominated by riffles and 

would have been expected to be composed of nearly all fluvial 

species if the river was ecologically unaltered.

The fish communities in the main stem and tributaries in 

both the Assabet and Charles River Basins for all habitat types 

indicate degraded aquatic ecosystems. However, the degree 

of degradation differs between the two basins. In the Assabet 

River Basin tributaries, only 30 percent (8 of 27) of the samples 

were devoid of fluvial fish species. Also, 38 percent (10 of 27) 

of the fish-community samples were composed of 75 percent or 

more fluvial fish species. In the Charles River tributaries, 56 

percent (9 of 16) of the samples were devoid of fluvial fish. 

Only 13 percent (2 of 16) of the tributary fish community 

samples were composed of 75 percent more fluvial fish species. 

Many of the generalist species are tolerant to degraded water 

quality. The extreme predominance of tolerant generalist 

species in the 16 samples from the Charles River demonstrates 

the cumulative effects of degraded flow, habitat, and water 

quality on the fish communities, combined with the effects of 

nearby impoundments and changing land use.

Comparison of Streamflow 

Requirement Methods

A review of the streamflow requirements (tables 3, 4, 

and 5) determined at selected cross sections, excluding the 

Nashoba Brook riffle site, by using the R2Cross and WettedPerimeter methods (fig. 18) illustrates the variability that can 

be found within and between these two standard-setting 

methods of analysis. For the nine riffle sites, the 25th and 75th 

percentiles interquartile range of the streamflow requirements, 

normalized for drainage area, for the R2Cross 3-of-3 criteria 

method are 0.65 ft3/s/mi2 and 1.48 ft3/s/mi2. The streamflow 

requirements derived from the R2Cross 2-of-3 criteria and 

Wetted-Perimeter methods have a narrower interquartile 

range of 0.09 ft3/s/mi2 to 0.26 ft3/s/mi2 and 0.12 ft3/s/mi2 to 

0.38 ft3/s/mi2, respectively, than the interquartile range for the 

R2Cross 3-of-3 criteria requirements. The interquartile ranges 

from the R2Cross 2-of-3 criteria and Wetted-Perimeter methods 

(fig. 17) agree closely with each other but do not overlap with 

the R2Cross 3-of-3 criteria results. The lack of overlap indicates 

that the methods identify different streamflow requirements.
Comparison of Streamflow Requirement Methods 35

0.0

0.5

1.0

1.5

2.0

2.5

3.0

DISCHARGE, IN CUBIC FEET PER SECOND PER SQUARE MILE

R2 Cross, 3-of-3 R2 Cross, 2-of-3 Wetted Perimeter

90th percentile

25th percentile

10th percentile

75th percentile

Median

Outlier

EXPLANATION

Figure 18. Streamflow requirements determined by the R2Cross 3-of-3 criteria, R2Cross 2-of-3 criteria, and 

Wetted-Perimeter methods for all cross sections analyzed.
36 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Table 17 shows the average of the cross-section flow 

requirements within each of the nine riffle reaches. The median 

and mean streamflow requirements determined by the R2Cross 

3-of-3 criteria were 0.86 ft3/s/mi2 and 1.10 ft3/s/mi2, respectively. The higher mean streamflow values reflect the influence 

of high flow events on the computation. The median and mean 

R2Cross 2-of-3 criteria streamflow requirements for habitat 

protection were 0.18 ft3/s/mi2 and 0.22 ft3/s/mi2, respectively. 

The median and mean Wetted-Perimeter streamflow requirements were 0.23 ft3/s/mi2 and 0.27 ft3/s/mi2, respectively.

A comparison of the R2Cross and Wetted-Perimeter 

streamflow requirements from the 9 Assabet River and 

Charles River sites to results determined from 10 index 

streamflow-gaging stations in southern New England reported 

by Armstong and others (2004) (fig. 19) shows that the 

streamflow requirements for the Assabet and Charles River 

sites are lower. The 10 index streamflow-gaging stations were 

the Squannacook River near West Groton, MA (01096000), 

Beaver Brook near North Pelham, NH (010965852), Old 

Swamp River near South Weymouth, MA (01105600), Wood 

River near Arcadia, RI (01117800), Mount Hope River near 

Warrenville, CT (01121000), Little River near Hanover, CT 

(01123000), South River near Conway, MA (01169900), Green 

River near Colrain, MA (01170100), Sevenmile River near 

Spencer, MA (01175670), and Green River at Williamstown, 

MA (01333000). These 10 index stations were on rivers with 

nearly unaltered streamflows and a variety of land uses. Most of 

the riffle sites in the Assabet and Charles River sites were on 

stream reaches with altered streamflows and areas of suburban 

land use. The size of the contributing areas of the Assabet River 

and Charles River study sites were generally less than those of 

the 10 index streamflow-gaging stations in southern New 

England (fig. 20). The median drainage area of the 9 Assabet 

and Charles River sites is 5.9 mi2; the median drainage areas for 

the 10 southern New England stations were 32.6 mi2. The 

R2Cross 3-of-3 streamflow requirements from both data sets 

have similar median values, however, the streamflow requirements for the Assabet and Charles River sites show a wider 

interquartile range than that for the southern New England 

stations. This is especially evident for the R2Cross 2-of-3 and 

Wetted-Perimeter results that were close to half of the flows 

determined at the 10 southern New England stations.

Differences in the streamflow requirements from these 

two standard-setting methods for the different riffle sites may 

be due to differences in stream-channel geometry between sites. 

Stream-channel morphology differs between stream systems, 

between tributaries of a single system, within a single reach, 

and even within the same channel type (Wood-Smith and 

Buffington, 1996; Trainor and Church, 2003). Channel cross 

sections and bed topography also vary over time. This variability may be small in stable, straight channels or large in 

rapidly changing channels.

The R2Cross and Wetted-Perimeter methods are applied to 

riffle habitats, which usually are stable stream features. Stream 

systems are not static, however. Alluvial channels adjust to 

produce an approximate equilibrium between the channel 

and the water and sediment it must transport (Leopold and 

Maddock, 1953). This quasi-equilibrium is achieved through 

changes in channel type, cross section (width, depth), slope, 

and bed topography (hydraulic roughness). The shape of the 

cross section of a natural channel primarily depends on stream 

discharge, although other factors, such as bedrock, a tributary 

delivering quantities of sediment, varying bank materials, 

riparian vegetation, or changes in flow resistance from woody 

debris can cause local differences.

Table 17. Summary of R2Cross and Wetted-Perimeter 

streamflow requirements for nine riffle sites included in analysis, 

Assabet and Charles River Basins, Massachusetts.

[ft3/s/mi2, cubic foot per second per square mile]

River and reach

Discharge (ft3/s/mi2)

R2Cross

Wetted 

perimeter 3 of 3

criteria

2 of 3

criteria

Assabet River near Westborough 1.01 0.07 0.05

Cold Harbor Brook near 

Northborough

.69 .05 .26

Danforth Brook at Hudson 2.13 .18 .24

Fort Meadow Brook near Hudson 1.5 .45 .35

Elizabeth Brook near Stow .56 .33 .18

Charles River near Hopkinton 1.44 .38 .21

Mine Brook near Franklin .61 .18 .47

Charles River at Medway upstream .75 .15 .18

Charles River at Medway 

downstream

.87 .33 .13

Median 0.87 0.18 0.21

Mean 1.06 .24 .23
Comparison of Streamflow Requirement Methods 37

90th percentile

25th percentile

10th percentile

75th percentile

Median

Outlier

DISCHARGE AREA, IN SQUARE MILES

CHARLES AND

ASSABET RIVERS

SOUTHERN

NEW ENGLAND

LOW FLOW

GROUP

CHARLES AND

ASSABET RIVERS

SOUTHERN

NEW ENGLAND

LOW FLOW

GROUP

0.0

0.5

1.0

1.5

2.0

2.5

3.0

EXPLANATION

CHARLES AND

ASSABET RIVERS

SOUTHERN

NEW ENGLAND

LOW FLOW

GROUP

R2 Cross 3-of-3 R2 Cross 3-of-3 Wetted Perimeter

Figure 19. R2Cross, 3-of-3 criteria, R2Cross, 2-of-3 criteria, and Wetted-Perimeter method streamflow requirements 

determined at 9 riffle sites in the Assabet and Charles River Basins, Massachusetts, and at 10 streamflow-gaging stations 

in southern New England reported in Armstrong and others (2004).
38 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

90th percentile

25th percentile

10th percentile

75th percentile

Median

Outlier

DISCHARGE AREA, IN SQUARE MILES

CHARLES AND

ASSABET SITES

TEN SOUTHERN

NEW ENGLAND

STATIONS

SIX STATIONS NEAR

THE CHARLES AND

ASSABET SITES

0

10

20

30

40

50

60

70

80

90

100

EXPLANATION

Figure 20. Drainage area at 9 riffle sites in the Assabet and Charles River Basins, Massachusetts, at 10 streamflowgaging stations in southern New England reported in Armstrong and others (2004), and six streamflow-gaging stations 

near the Assabet and Charles River Basins.
Comparison of Streamflow Requirement Methods 39

Over time, channels will respond to altered flow conditions. For example, changes in land use, such as urbanization, 

can increase runoff and result in increased channel width. 

Impoundments may cause upstream aggradation and downstream degradation of sediment. Reduced discharges are 

thought to result in reduced channel widths and depths, 

decreases in channel cross-sectional area, width-to-depth ratio 

changes, and emplacement of large woody debris; the extent of 

these changes depends on the particle sizes of bed load, bed, and 

banks. Vegetation established on bars during prolonged lowflow periods also may affect channel capacity and processes. 

Channel adjustments are not instantaneous; channels can exist 

in non-equilibrium states for substantial periods of time 

(Jacobson and others, 2001). The degree to which stream 

channels adjust to altered flows and the effects of these channel 

adjustments on Wetted-Perimeter and R2Cross streamflow 

requirements is not well understood.

A diagnostic method (RVA) [Richter and others, 1997] 

and a standard-setting method (Tennant, 1976; Instream Flow 

Council, 2002) were applied to streamflow records from 1976 

to 2000 for the summer low-flow period from six streamflowgaging stations in MA, NH, and RI near the Assabet and 

Charles River Basins with relatively unaltered flow. The six 

streamflow-gaging stations chosen for this analysis were the 

Squannacook River near West Groton, MA (01096000), Beaver 

Brook near North Pelham, NH (010965852), Old Swamp River 

near South Weymouth, MA (01105600), Indian Head River 

near Hanover, MA (01105730), Branch River at Forestdale, RI 

(01111500), and Sevenmile River near Spencer, MA 

(01175670) (fig. 2).

The RVA method defines the range of target streamflows 

as the interquartile ranges for each of 33 statistical IHA 

parameters (Richter and others, 1996). Half of the statistics 

measure the central tendency of the magnitude or rate of change 

of flow, and half focus on the magnitude, duration, timing, and 

frequency of extreme events. The results the IHA analyses for 

all six streamflow-gaging stations are presented in table 19 at 

the end of this report.

The variability of monthly discharges among the six 

streamflow-gaging stations is mostly due to the differences in 

the contributing drainage areas for the stations. A linear 

regression plot between drainage area and the medians of the 

monthly flow durations showed that R2 ranged from 0.90 to 

0.99 for the lower-quartile flows and from 0.88 to 0.99 for the 

upper-quartile flows. These values indicate that at least 90 

percent of the variability in streamflows is due to the differences 

in the drainage areas for each of the streamflow-gaging stations. 

Consequently, regional streamflow statistics were determined 

by combining the monthly flows, normalized by drainage area, 

from each of the streamflow-gaging stations.

The interquartile ranges of the mean monthly discharges 

for the six streamflow-gaging stations (fig. 21), normalized for 

drainage area, are mostly bracketed by the R2Cross 3-of-3 

criteria on the upper end and the R2Cross 2-of-3 criteria and 

Wetted-Perimeter median streamflow requirements on the 

lower end for the summer low-flow period of July through 

September. The drainage areas for the six nearby streamflowgaging stations are significantly larger than the drainage areas 

for the nine Assabet and Charles River Basin riffle sites 

(fig. 20). The median R2Cross 2-of-3 and Wetted-Perimeter 

requirements are less than the 25th-percentile monthly flow for 

the summer months. Use of a monthly flow statistic can indicate 

only variability between years. Monthly flow statistics do not 

give an indication of daily variation. An analysis of the duration 

of daily flows during each month of the year, which was beyond 

the scope of this report, would give a better understanding of 

how often the streamflow requirements are met within any 

month of the year.

The Tennant method (Tennant, 1976) bases its streamflow 

requirements on the observation that aquatic habitat conditions 

are similar in streams carrying the same proportion of the 

mean annual flow (QMA). The Tennant method has different 

criteria for the winter (October–March) and summer (April–

September) flow periods. During summer low-flow periods, 

specified percentages of the mean annual discharge (QMA) are 

defined as providing good, fair, and poor habitat conditions, 

respectively, according to Tennant (1976). The medians for the 

six streamflow-gaging stations are presented in table 18. The 

median R2Cross 3-of-3 criteria streamflow requirement for the 

nine riffles (0.87 ft3/s/mi2; table 17) is close to the Tennant 0.4 

QMA, which is defined as providing good-habitat conditions 

(0.74 ft3/s/mi2). The median Wetted-Perimeter and R2Cross 

2-of-3 criteria streamflow requirements (0.21 ft3/s/mi2 and 

0.18 ft3/s/mi2; table 15) are close to the Tennant 0.1 QMA, 

which is defined as providing poor habitat conditions 

(0.19 ft3/s/mi2).
40 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Application of R2Cross and Wetted-Perimeter methods to 

sites with altered streamflows or at sites that are only riffles at 

low to moderate flows can result in a greater variability of 

streamflow requirements than would result if the methods were 

applied to riffles on natural channels with unaltered streamflows. The R2Cross 2-of-3 and the Wetted-Perimeter 

streamflow requirements for the Assabet and Charles River 

sites show narrower interquartile ranges and lower median 

steamflow requirements than for 10 index streamflow-gaging 

stations in southern New England stations (Armstrong and 

others, 2004). The R2Cross 2-of-3 and Wetted-Perimeter 

results were also less than the 25th-percentile of monthly mean 

flows during the summer months as determined for six nearby 

streamflow-gaging stations. These streamflow requirements are 

in the poor habitat range as indicated by a Tennant analysis of 

the same six stations. These comparisons indicate that the 

R2Cross and Wetted-Perimeter methods under-estimate 

streamflow requirements when applied to sites in smaller 

drainage areas and channels that are runs at higher flows.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

October

November

December

January

February

March

April

May

June

July

August

September

October

75th percentile

median

25th percentile

R2Cross 3-of-3

R2Cross 2-of -3

Wetted Perimeter

DISCHARGE PER AREA, IN CUBIC FEET PER SECOND PER SQUARE MILE

Figure 21. Quartiles of mean monthly discharges for the period 1976–2000 for six streamflow-gaging stations compared 

with median streamflow requirements estimated by the R2Cross 3-of-3 criteria, R2Cross 2-of-3 criteria, and WettedPerimeter methods for nine riffles in the Assabet and Charles River Basins, Massachusetts.
Conclusions 41

Conclusions

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

the Massachusetts Executive Office of Environmental Affairs 

Watershed Initiative Program and Massachusetts Department 

of Conservation and Recreation, began a habitat assessment 

in 2001 to determine the streamflow requirements in the 

Assabet and Charles River Basins. In addition, the USGS 

coordinated its work with fish-assessment studies conducted 

by the Massachusetts Division of Fisheries and Wildlife to 

evaluate the current (2000–02) fish population in the Assabet 

and Charles River Basins. In 2002, a project was started by the 

USGS in cooperation with the Town of Hudson, MA, and in 

collaboration with the Organization of the Assabet River, to 

study additional riffle reaches in the Assabet River Basin. This 

report presents comparisons of R2Cross and Wetted-Perimeter 

methods of determining streamflow requirements with the 

Range of Variability Approach and Tennant method. The 

variability of the R2Cross and Wetted-Perimeter methods were 

also determined by comparison of results from the Assabet 

River and Charles River sites to results from riffles near 10 

index streamflow-gaging stations in Southern New England. 

The study area includes two main-stem riffle reaches and a 

main-stem headwater reach of the Charles River, a main-stem 

headwater reach of the Assabet River and six reaches on 

tributaries to the Assabet and Charles Rivers in Massachusetts. 

The Assabet River tributary reaches were on Cold Harbor 

Brook, Danforth Brook, Fort Meadow Brook, Elizabeth Brook, 

and Nashoba Brook. The main-stem headwater reach of the 

Assabet River was near Westborough. The Charles River Basin 

reaches were on Mine Brook and on the main stem of the 

Charles River at Medway and the main-stem headwater reach of 

the Charles River was near Hopkinton.

Fish-community assessments were used to indicate 

the ecological condition of the Assabet and Charles Rivers. 

Biological monitoring in this study targeted fish because they 

are long-lived, and are sensitive to a wide range of stresses. 

Fish-community data used in this report were collected in 

the Assabet and Charles River Basins between August 1999 

and September 2002, as part of the Massachusetts Division 

of Fisheries and Wildlife Statewide Fisheries Assessment 

Program. Additional fish-community data used in this report 

were collected in the Charles River Basin during August 

of 2002, as part of the Massachusetts Department of 

Environmental Protection, Charles River Watershed 

Monitoring Program. Sampling reaches were distributed 

over the length of the main stem and tributaries of the 

Charles and Assabet River Basins.

The observed fish communities in the main stems of the 

Charles and Assabet Rivers were compared to the expected 

target-fish community developed for the Quinebaug River, 

as well as to the fish communities in other river basins in 

Massachusetts. Fish were classified into three macrohabitat 

classes on the basis of their habitat use: macrohabitat generalists, fluvial dependents, and fluvial specialists (Bain and 

Knight, 1996, Bain and Meixler, 2000). Stocked fish, including 

rainbow trout, brown trout, and stocked brook trout were not 

included in the fish-community analysis.

Fish-sampling information and community assessments 

were categorized by basin size and free-flowing status. Reaches 

with drainage areas of greater than 30 mi2 were classified 

as main-stem reaches (Anderson and Olivero, The Nature 

Conservancy, written commun., 2003). Reaches with drainage 

areas less than 30 mi2 were classified as tributary or headwater 

reaches. Only the fish-community data from the main-stem 

reaches were compared to target fish communities developed 

for the Quinebaug River because target fish communities have 

only been developed for main-stem reaches. Tributary sites are 

expected to have larger proportions of fluvial fish species than 

main-stem reaches (M.B. Bain, Cornell University, oral 

commun., 2003). Analysis of recent fish collections in the 

Quinebaug, Blackstone, Westfield, Nashua, Housatonic, and 

Shawsheen River Basins strongly indicates that tributaries 

normally have a higher percent of fluvial fish than their 

corresponding main-stem reaches.

Table 18. Streamflow requirements estimated by the Tennant 

method from the combined records of six streamflow-gaging 

stations near the Assabet and Charles River Basins, 

Massachusetts.

[ft3/s/mi2, cubic foot per second per square mile]

Percentage

of mean

annual

flow

Tennant

classification

Median

streamflow 

requirement

(ft3/s/mi2)

0.5 Excellent habitat, April–September 0.93

.4 Good habitat, April–September

Outstanding habitat, October–March

0.74

.3 Fair habitat, April–September

Excellent habitat, October–March

.56

.2 Good habitat, October–March .37

.1 Poor habitat, April–September

Fair/Poor habitat, October–March

.19
42 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Fish in the free-flowing reaches with drainage areas 

greater than 30 mi2 in the Assabet River main stem consisted of 

52.9 percent macrohabitat generalists, 22.3 percent fluvial 

dependents, and 24.8 percent fluvial specialists. Fish in freeflowing reaches with drainage areas greater than 30 mi2 in the 

Charles River main stem consisted of 98.3 percent macrohabitat 

generalists, 1.7 percent fluvial dependents, and no fluvial 

specialists. In general, the Charles River is dominated by 

macrohabitat generalist species; fluvial species are rare or 

absent. The percentages of fluvial fish species in the Charles 

River were considerably less than those in the Quinebaug River 

target fish community. These higher percentages of generalists 

indicate that the Charles River fish community is degraded. The 

species composition of the Assabet River main stem also indicates a degraded fish community, although the fish-community 

of the Assabet River Basin is less degraded than that of the 

Charles River Basin.

The fish species compositions of the Assabet and Charles 

River tributaries and headwaters are considerably different. 

Fish in free-flowing reaches with drainage areas less than 30 

mi2 in the Assabet River tributaries and headwaters consisted of 

50.8-percent macrohabitat generalists, 17.9-percent fluvial 

dependents, and 31.3-percent fluvial specialists. Fish in freeflowing reaches in the Charles River tributaries and headwaters 

consisted of 88.9-percent macrohabitat generalists, 8.7-percent 

fluvial dependents, and 2.4-percent fluvial specialists. These 

results indicate that the macrohabitat generalists compose a 

larger proportion of the fish community in the tributaries and 

main stem of the Charles River than would be expected. The 

composite data for all the Assabet River tributaries strongly 

indicates that the fish community is also degraded.

The fish communities in the main stem and tributary 

reaches of both the Assabet and Charles River Basins for all 

habitat types indicate degraded aquatic ecosystems. However, 

the degree of degradation of the Charles River fish community 

is greater than that of the Assabet River fish community. The 

extreme predominance of tolerant generalist species in the 

Charles River fish community demonstrates the effects of 

degraded flow, habitat, and water quality combined with the 

effects of nearby impoundments and changing land use.

The R2Cross and Wetted-Perimeter methods require 

collection of site-specific physical and hydraulic data, such as 

channel geometry, average velocity, and average depth at riffle 

sites. An advantage of the R2Cross and Wetted-Perimeter 

methods is that they are based upon results from a calibrated 

hydraulic model and do not require streamflow records; thus, 

the flow values obtained by these methods can be applied in 

hydrologically disturbed drainage basins and at carefully 

selected gaged or ungaged sites. Consequently, streamflow 

requirements determined for natural riffle sites may not be 

sufficient to protect habitat at sites in a widened channel and 

may be excessive at sites in an artificially restricted channel. 

Conversely, flow requirements estimated at sites with a 

narrowed channel may not provide sufficient flows for habitat 

protection in undisturbed stream reaches. Because one site 

(Nashoba Brook in the Assabet River Basin) had a concrete wall 

along its right bank, the estimated streamflow requirement for 

this site was not included in comparisons with results obtained 

by other methods.

The median streamflow requirements defined by the 

R2Cross 3-of-3 criteria, R2Cross 2-of-3 criteria, and WettedPerimeter methods for the nine natural riffle reaches were 

0.86 ft3/s/mi2, 0.18 ft3/s/mi2, and 0.23 ft3/s/mi2, respectively. 

For the R2Cross 3-of-3 criteria method for the nine riffle 

sites, the 25th and 75th percentiles interquartile range of the 

streamflow requirements, normalized for drainage area are 

0.65 ft3/s/mi2 and 1.48 ft3/s/mi2, respectively. The streamflow 

requirements derived from the R2Cross 2-of-3 criteria and 

Wetted-Perimeter methods have a narrower interquartile 

range of 0.09 ft3/s/mi2 to 0.26 ft3/s/mi2 and 0.12 ft3/s/mi2 to 

0.38 ft3/s/mi2, respectively, than the interquartile range for the 

R2Cross 3-of-3 criteria requirements. The discharge required 

for each riffle site was calculated by averaging the streamflow 

requirements for the critical cross sections within each riffle 

reach.

A comparison of the R2Cross and Wetted-Perimeter 

streamflow requirements from the 9 Assabet River and Charles 

River sites to results determined from 10 index streamflowgaging stations in southern New England reported by 

Armstrong and others (2004) shows that the streamflow 

requirements for the Assabet River and Charles River sites are 

lower. Most of the riffle sites in the Assabet and Charles River 

sites were on stream reaches with altered streamflows and areas 

of suburban land use. The R2Cross 3-of-3 streamflow requirements from both data sets have similar median values; however, 

the streamflow requirements for the Assabet and Charles River 

sites show a wider interquartile range than that for the southern 

New England stations. This is especially evident for the 

R2Cross 2-of-3 and Wetted-Perimeter results that were close to 

half of the flows determined at the 10 southern New England 

stations. Differences in the streamflow requirements from these 

two standard-setting methods for the different riffle sites may 

be due to differences in stream-channel geometry between sites. 

The degree to which stream channels adjust to altered flows and 

the effects of these channel adjustments on Wetted-Perimeter 

and R2Cross streamflow requirements is not well understood.
Acknowledgments 43

The RVA diagnostic method was applied to records for the 

common period of 1976 to 2000 from six streamflow-gaging 

stations with relatively unaltered flow in or around the Assabet 

River and Charles River Basins, so that regional and seasonal 

comparisons with the R2Cross and Wetted-Perimeter results for 

the nine ungaged riffle reaches could be made. The median 

R2Cross and Wetted-Perimeter streamflow requirements for 

July through September mostly bracket the interquartile ranges 

of the mean monthly discharges normalized for drainage area 

from all six streamflow-gaging stations. The R2Cross 2-of-3 

and Wetted-Perimeter median flow requirements are less than 

the 25th-percentile flow for all 5 months of June through 

October.

The Tennant standard-setting method was applied to the 

records for the same six regional streamflow-gaging stations 

used in the RVA analysis. The Tennant method commonly 

defines minimum streamflows for small streams during summer 

flow periods as 40, 30, and 10 percent of the mean annual 

discharge (QMA); these values represent good, fair, and poor 

habitat conditions, respectively. The median R2Cross 3-of-3 

criteria streamflow requirement for the nine riffles compares 

closely to the median Tennant 0.4 QMA definition for good 

habitat. The median Wetted-Perimeter and R2Cross 2-of-3 

criteria streamflow requirement compares closely to the median 

Tennant 0.1 QMA definition for poor habitat. These results 

correspond well with the R2Cross and Wetted-Perimeter 

streamflow requirements, which, in turn, bracket the RVA 

monthly interquartile ranges for the summer-period.

Application of R2Cross and Wetted-Perimeter methods to 

sites with altered streamflows or at sites that are riffles only at 

low to moderate flows can result in a greater variability of 

streamflow requirements than would result if the methods 

were applied to riffles on natural channels with unaltered 

streamflows. The R2Cross 2-of-3 and the Wetted-Perimeter 

streamflow requirements for the Assabet and Charles River 

sites show narrower interquartile ranges and lower median 

steamflow requirements than for 10 index streamflow-gaging 

stations in southern New England (Armstrong and others, 

2004). The R2Cross 2-of-3 and Wetted-Perimeter results were 

also less than the 25th-percentile of monthly mean flows during 

the summer months as determined for six nearby streamflowgaging stations. These streamflow requirements are in the poor 

habitat range as indicated by a Tennant Method analysis of the 

same six stations. These comparisons indicate that the R2Cross 

and Wetted-Perimeter methods underestimate streamflow 

requirements when applied to sites in drainage areas smaller 

than 30 mi2 and channels that are runs at higher flows.

Acknowledgments

The authors are grateful to Susan Beede and Suzanne Flint 

from the Organization of the Assabet River and to Anna Eleria 

and Dudley Bonsal from the Charles River Basin Association 

for assistance with field surveys and surface-water data 

collection during this study. The authors would also like to 

thank Michael J. Fleming for assistance in coordinating 

volunteer activities. The cooperation of several public and 

private landowners who granted access to the Assabet and 

Charles River riffle study sites is also appreciated.

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of Fish, Wildlife, and Parks: Bozeman, MT, Montana 

Department of Fish, Wildlife, and Parks, variously paged.

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selected sites on the Assabet and Charles Rivers, eastern 

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D.P., 1996, A method for assessing hydrologic alteration 

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Braun, D.P., 1997, How much water does a river need?: 

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recreation, and related environmental resources, in Instream 

flow needs, volume II: Boise, ID, Proceedings of the 

symposium and specialty conference on instream flow needs, 

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Table 19. Flow statistics determined for 

Indicators of Hydrologic Alteration approach for 

six streamflow-gaging stations near the Assabet 

and Charles River Basins, Massachusetts.

Table 19 47

Table 19. Flow statistics determined for Indicators of Hydrologic Alteration approach for six streamflow-gaging stations near the 

Assabet and Charles River Basins, Massachusetts.

Period or condition

Percentile

10th 25th 50th 75th 90th (75-25)/50

SQUANNACOOK RIVER NEAR WEST GROTON, MA (01096000) Pre-impact period: 1976–2000 (25 years)

Magnitude of monthly mean discharge (cubic feet per second)

October 19.57 25.66 40.06 99.52 156.46 1.84

November 30.35 52.4 108.7 150.08 225.33 .9

December 39.61 65.11 85.65 183.39 252.38 1.38

January 37.42 68.97 132.1 180.85 244.18 .85

February 59.76 86.91 123.86 199.73 248.41 .91

March 131.88 188.37 227.61 275.11 417.17 .38

April 96.9 146.63 246.37 334.48 410.51 .76

May 59.91 95.5 145.26 180.35 239.59 .58

June 26.78 38.72 61.13 134.87 258.27 1.57

July 14.76 24.74 30.9 60.1 76.35 1.14

August 12.93 18.15 26.94 49.56 79.45 1.17

September 12.55 15.13 26.47 37.97 53.02 .86

Magnitude and duration of annual discharge conditions (cubic feet per second)

1-day minimum 6.8 9.25 12 14.5 17.8 .44

3-day minimum 7.08 9.37 13 14.83 18 .42

7-day minimum 7.59 10.07 13.71 15.79 18.34 .42

30-day minimum 9.71 12.64 16.67 19.58 29 .42

90-day minimum 13.65 17.22 25.76 35.6 48.32 .71

1-day maximum 655.6 820.5 1,200 2,035 2,368 1.01

3-day maximum 459.07 631.83 804 1,311.17 1,520.93 .84

7-day maximum 348.37 421.57 586.43 857.57 957.94 .74

30-day maximum 233.13 262.37 335.43 424.38 556.03 .48

90- day maximum 166.68 195.43 242.04 281.67 333.64 .36

 Zero discharge days 0 0 0 0 0 0

7-day minimum/mean annual 

discharge

.06 .08 .11 .15 .2 .68

Timing of annual discharge extremes (Julian day)

Date of minimum 1-day discharge 226.6 237 256 272 283.8 .1

Date of maximum 1-day discharge 314.8 28.5 74 102.5 121.6 .2

Frequency and duration of high and low pulses 

Times that daily discharge is less 

than the 25th percentile of daily 

discharge (count)

3.6 4.5 6 8.5 12.6 .67

Days that daily discharge is less 

than the 25th percentile

5.94 7.92 11.22 17.5 30.84 .85

Times that daily discharge is 

greater than the 75th percentile of 

daily discharge (count)

5.6 8.5 11 14 17 .5

Days that daily discharge is greater 

than the 75th percentile

3.99 5.71 7.75 11.08 12.86 .69
48 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

SQUANNACOOK RIVER NEAR WEST GROTON, MA (01096000), Pre-impact period: 1976–2000 (25 years)—Continued

Rate and frequency of hydrograph changes

Mean of all positive differences 

between consecutive daily 

discharges (rise rate) 

31.09 40.18 51.26 73.37 90.46 0.65

Mean of all negative differences 

between consecutive daily 

discharges (fall rate)

-40.44 -31.61 -24.49 -19.4 -15.03 -.5

Number of reversals 85.6 93 95 104 108 .12

BEAVER BROOK AT NORTH PELHAM, MA (010965852), Pre-impact period: 1976–2000 (25 years)

Magnitude of monthly mean discharge (cubic feet per second)

October 11.15 14.24 25.03 69.74 107.29 2.22

November 17.66 30.3 74.9 102.47 142.71 .96

December 27.06 32.35 59.97 122.37 175.35 1.5

January 25.77 48.53 79.77 116.68 170.25 .85

February 37.79 55.89 85.79 121.96 180.61 .77

March 90.21 126.48 147.13 188.29 282.45 .42

April 62.37 87.18 147.23 213.72 281.69 .86

May 42.15 63.05 92.55 121.81 132.93 .63

June 16.07 21.48 42.63 72.07 183.06 1.19

July 6.1 10.01 20.51 41.45 52.29 1.53

August 3.51 5.8 15.14 31.63 60.96 1.71

September 4.07 6.35 16 23.89 35.97 1.1

Magnitude and duration of annual discharge conditions (cubic feet per second)

1-day minimum 1.2 1.95 4.6 5.65 8.7 .8

3-day minimum 1.27 2.07 4.87 5.88 9.07 .78

7-day minimum 1.37 2.29 5.24 7.37 9.64 .97

30-day minimum 1.95 3.66 7.48 11.23 16.66 1.01

90-day minimum 3.43 7.73 15.33 21.54 31.22 .9

1-day maximum 393.6 519 753 1,270 1,464 1

3-day maximum 311.47 402 601 975.33 1,147.33 .95

7-day maximum 225.8 294.93 452.86 622.21 780.03 .72

30-day maximum 140.41 172.72 226.27 289.72 399.72 .52

90- day maximum 117.08 127.9 161.47 190.33 222.39 .39

 Zero discharge days 0 0 0 0 0 0

7-day minimum/mean annual 

discharge

.02 .02 .07 .09 .15 1.07

Timing of annual discharge extremes (Julian day)

Date of minimum 1-day discharge 220.2 242 254 270 283.6 .08

Date of maximum 1-day discharge 320 28 74 97 162.2 .19

Table 19. Flow statistics determined for Indicators of Hydrologic Alteration approach for six streamflow-gaging stations near the 

Assabet and Charles River Basins, Massachusetts.—Continued

Period or condition

Percentile

10th 25th 50th 75th 90th (75-25)/50
Table 19 49

BEAVER BROOK AT NORTH PELHAM, MA (010965852), Pre-impact period: 1976–2000 (25 years)—Continued

Frequency and duration of high and low pulses 

Times that daily discharge is less 

than the 25th percentile of daily 

discharge (count)

3 5 7 9 13.4 0.57

Days that daily discharge is less 

than the 25th percentile

6.28 7.24 11.14 17.37 27.35 .91

Times that daily discharge is 

greater than the 75th percentile of 

daily discharge (count)

5.6 7.5 11 13 17 .5

Days that daily discharge is greater 

than the 75th percentile

4.47 6.5 9 11.17 13.01 .52

Rate and frequency of hydrograph changes

Mean of all positive differences 

between consecutive daily 

discharges (rise rate) 

16.45 24 34.9 40.65 57.02 .48

Mean of all negative differences 

between consecutive daily 

discharges (fall rate)

-22.2 -17.14 -14.63 -10.61 -7.29 -.45

Number of reversals 80.4 88 93 100 111.6 .13

OLD SWAMP RIVER NEAR SOUTH WEYMOUTH, MA (01105600), Pre-impact period: 1976–2000 (25years)

Magnitude of monthly mean discharge (cubic feet per second)

October 1.69 2.51 3.41 8.1 10.64 1.64

November 3.28 4.71 8.97 11.99 18.43 .81

December 3.62 5.54 8.95 15.4 21.35 1.1

January 3.56 8.2 11.64 16.84 27.25 .74

February 6.14 6.92 11.93 16.59 24.8 .81

March 7 10.01 13.72 20.07 29.96 .73

April 5.02 7.33 12.01 17.57 26.69 .85

May 4.38 5.6 8.14 10.91 16.42 .65

June 1.54 2.48 3.17 9.57 23.25 2.24

July .7 .92 1.82 5.36 6.7 2.44

August .81 1.24 3.11 4.37 7.5 1.01

September .71 1.4 2.17 3.47 7.69 .96

Table 19. Flow statistics determined for Indicators of Hydrologic Alteration approach for six streamflow-gaging stations near the 

Assabet and Charles River Basins, Massachusetts.—Continued

Period or condition

Percentile

10th 25th 50th 75th 90th (75-25)/50
50 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

OLD SWAMP RIVER NEAR SOUTH WEYMOUTH, MA (01105600), Pre-impact period: 1976–2000 (25 years)—Continued

Magnitude and duration of annual discharge conditions (cubic feet per second)

1-day minimum 0.15 0.19 0.33 0.51 0.62 0.98

3-day minimum .16 .23 .36 .56 .71 .9

7-day minimum .19 .31 .51 .68 .84 .73

30-day minimum .34 .58 .93 1.18 1.72 .65

90-day minimum .82 1.48 1.91 2.92 3.76 .75

1-day maximum 59.2 100 122 193.5 278 .77

3-day maximum 44.13 59.17 83.33 122 198.33 .75

7-day maximum 29.25 37.86 54.14 74.5 110.94 .68

30-day maximum 16.93 19.16 26.58 34.23 43.89 .57

90- day maximum 11.41 15.16 19.16 20.74 25.94 .29

 Zero discharge days 0 0 0 0 0 0

7-day minimum/mean annual 

discharge

.03 .04 .05 .08 .1 .84

Timing of annual discharge extremes (Julian day)

Date of minimum 1-day discharge 201.4 212 237 273 276.4 .17

Date of maximum 1-day discharge 331.2 25.5 71 107.5 141 .22

Frequency and duration of high and low pulses 

Times that daily discharge is less 

than the 25th percentile of daily 

discharge (count)

6 8.5 11 12 15.4 .32

Days that daily discharge is less 

than the 25th percentile

4.51 6.21 8 9.38 16.53 .4

Times that daily discharge is 

greater than the 75th percentile of 

daily discharge (count)

9.8 16 20 23.5 26.8 .38

Days that daily discharge is greater 

than the 75th percentile

2.63 3.36 5 5.69 7.12 .47

Rate and frequency of hydrograph changes

Mean of all positive differences 

between consecutive daily 

discharges (rise rate) 

3.74 6.13 7.35 9.5 11.79 .46

Mean of all negative differences 

between consecutive daily 

discharges (fall rate)

-4.87 -3.76 -2.8 -2.38 -1.43 -.49

Number of reversals 88.6 100 106 112 117 .11

Table 19. Flow statistics determined for Indicators of Hydrologic Alteration approach for six streamflow-gaging stations near the 

Assabet and Charles River Basins, Massachusetts.—Continued

Period or condition

Percentile

10th 25th 50th 75th 90th (75-25)/50
Table 19 51

SEVENMILE RIVER NEAR SPENCER, MA (01175670), Pre-impact period: 1976–2000 (25 years)

Magnitude of monthly mean discharge (cubic feet per second)

October 3.17 5.66 18.07 28.68 2.63 3.17

November 6.83 12 22 26.55 1.26 6.83

December 8.05 14.56 25.48 36.9 1.2 8.05

January 10.24 19.52 28.92 41.33 .96 10.24

February 12.14 18.57 26.54 36.7 .78 12.14

March 23.11 28.77 37.63 46.87 .5 23.11

April 19.07 29 41.4 48.43 .77 19.07

May 13.92 17.86 21.96 31.39 .45 13.92

June 5.08 6.35 17.41 32.33 1.94 5.08

July 2.18 4.38 7.37 9.39 1.18 2.18

August 1.71 3.72 7.75 13.68 1.62 1.71

September 1.09 1.88 5.96 10.9 2.59 1.09

Magnitude and duration of annual discharge conditions (cubic feet per second)

1-day minimum .11 .17 .29 .62 .89 1.55

3-day minimum .15 .22 .3 .82 .97 1.99

7-day minimum .19 .31 .4 1.02 1.44 1.76

30-day minimum .35 .45 1.12 1.83 2.9 1.23

90-day minimum .81 1.65 2.24 4.09 6.91 1.09

1-day maximum 75.2 99.5 161 194.5 235.6 .59

3-day maximum 55.47 80.33 117.33 149.5 182.73 .59

7-day maximum 41.34 59.5 83.57 102.14 141.14 .51

30-day maximum 27.85 37.43 47.1 56.22 68.3 .4

90- day maximum 22.3 27.55 32.46 37.32 39.8 .3

 Zero discharge days 0 0 0 0 0 0

7-day minimum/mean annual 

discharge

.01 .02 .03 .06 .1 1.79

Timing of annual discharge extremes (Julian day)

Date of minimum 1-day discharge 209 240 257 273 279.6 .09

Date of maximum 1-day discharge 295 20.5 70 102.5 154.4 .22

Frequency and duration of high and low pulses 

Times that daily discharge is less 

than the 25th percentile of daily 

discharge (count)

4 5.5 8 9.5 12.8 .5

Days that daily discharge is less 

than the 25th percentile

4.56 7.4 11.57 15.61 21.58 .71

Times that daily discharge is 

greater than the 75th percentile of 

daily discharge (count)

7.6 9.5 12 15 19.4 .46

Days that daily discharge is greater 

than the 75th percentile

3.86 5.61 6.83 8.66 10.15 .45

Table 19. Flow statistics determined for Indicators of Hydrologic Alteration approach for six streamflow-gaging stations near the 

Assabet and Charles River Basins, Massachusetts.—Continued

Period or condition

Percentile

10th 25th 50th 75th 90th (75-25)/50
52 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

SEVENMILE RIVER NEAR SPENCER, MA (01175670), Pre-impact period: 1976–2000 (25 years)—Continued

Rate and frequency of hydrograph changes

Mean of all positive differences 

between consecutive daily 

discharges (rise rate) 

4.04 4.95 7.02 8.38 9.34 0.49

Mean of all negative differences 

between consecutive daily 

discharges (fall rate)

-4.3 -3.63 -3.01 -2.38 -1.88 -.41

Number of reversals 95 98 106 111.5 124.8 .13

INDIAN HEAD RIVER AT HANOVER, MA (01105730), Pre-impact period: 1976–2000 (25 years)

Magnitude of monthly mean discharge (cubic feet per second)

October 9.98 14.21 26.03 62.55 81.87 1.86

November 24.31 34 65.8 81.38 116.56 .72

December 29.08 39.08 59.77 118.98 155.27 1.34

January 25.11 55.29 79.03 114.15 176.25 .74

February 44.77 58.04 93.57 115.85 152.88 .62

March 68.22 79.02 98.9 149.11 190.03 .71

April 41.09 53.4 83.3 122.6 197.5 .83

May 30.02 41.11 63.16 82.5 104.92 .66

June 12.39 16.78 24.33 55.02 154.55 1.57

July 6.42 7.88 12.47 37.73 49.38 2.39

August 4.85 8.09 20.48 37.66 53.92 1.44

September 4.97 8.86 15.51 24.03 49.98 .98

Magnitude and duration of annual discharge conditions (cubic feet per second)

1-day minimum .72 2.1 3.5 4.25 5.58 .61

3-day minimum 1.1 2.42 3.77 4.87 6.56 .65

7-day minimum 2.03 2.89 4.44 7.35 8.22 1

30-day minimum 3.06 5.01 6.54 10.2 14.03 .79

90-day minimum 5.93 8.64 13.78 23.48 29.31 1.08

1-day maximum 334.4 422.5 600 759.5 946.2 .56

3-day maximum 256.8 341.17 469 578.83 748.07 .51

7-day maximum 168.8 231.5 287.86 404.21 489 .6

30-day maximum 114.87 133.75 184.87 218.75 240.76 .46

90- day maximum 78.22 97.5 125.72 148.43 169.21 .41

 Zero discharge days 0 0 0 0 0 0

7-day minimum/mean annual 

discharge

.04 .05 .08 .11 .15 .83

Timing of annual discharge extremes (Julian day)

Date of minimum 1-day discharge 200.2 212.5 257 275 277.4 .17

Date of maximum 1-day discharge 331.6 26.5 63 107.5 155.4 .22

Table 19. Flow statistics determined for Indicators of Hydrologic Alteration approach for six streamflow-gaging stations near the 

Assabet and Charles River Basins, Massachusetts.—Continued

Period or condition

Percentile

10th 25th 50th 75th 90th (75-25)/50
Table 19 53

INDIAN HEAD RIVER AT HANOVER, MA (01105730), Pre-impact period: 1976–2000 (25 years)—Continued

Frequency and duration of high and low pulses 

Times that daily discharge is less 

than the 25th percentile of daily 

discharge (count)

3.6 5 7 9 13.4 0.57

Days that daily discharge is less 

than the 25th percentile

4.75 7.03 10.17 16.2 26.24 .9

Times that daily discharge is 

greater than the 75th percentile of 

daily discharge (count)

7.6 12 15 18 19.4 .4

Days that daily discharge is greater 

than the 75th percentile

3.33 4 6.83 7.9 11.58 .57

Rate and frequency of hydrograph changes

Mean of all positive differences 

between consecutive daily 

discharges (rise rate) 

15.23 25.01 30.3 36.28 40.45 .37

Mean of all negative differences 

between consecutive daily 

discharges (fall rate)

-16.99 -16.12 -12.27 -9.98 -6.95 -.5

Number of reversals 90 95 102 111 119.2 .16

BRANCH RIVER AT FORESTDALE, RI (01111500), Pre-impact period: 1976–2000 (25 years)

Magnitude of monthly mean discharge (cubic feet per second)

October 58.48 69.11 85.87 132.27 333.57 .74

November 77.36 109.83 156.17 226.18 323.52 .75

December 79.76 109.42 162.61 324.03 460.44 1.32

January 96.07 129.06 252.77 323.18 491.65 .77

February 139.18 174.43 242 337.61 380.22 .67

March 179.57 233.9 307.68 400.42 580.01 .54

April 128.04 186.42 305.23 398.53 643.49 .69

May 121.68 126.34 184.39 271.84 320.77 .79

June 47.71 52.88 84.47 180.72 375.49 1.51

July 25.55 33.47 46.1 85.97 127.54 1.14

August 22.39 26.45 52.13 94.34 157.08 1.3

September 21.47 33.38 45.87 72.59 116.05 .85

Table 19. Flow statistics determined for Indicators of Hydrologic Alteration approach for six streamflow-gaging stations near the 

Assabet and Charles River Basins, Massachusetts.—Continued

Period or condition

Percentile

10th 25th 50th 75th 90th (75-25)/50
54 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

BRANCH RIVER AT FORESTDALE, RI (01111500), Pre-impact period: 1976–2000 (25 years)—Continued

Magnitude and duration of annual discharge conditions (cubic feet per second)

1-day minimum 11 14.5 18 22.5 27.2 0.44

3-day minimum 11.2 14.67 19.33 24.33 28.53 .5

7-day minimum 11.94 15.5 21.29 26.57 32.2 .52

30-day minimum 14.96 21.78 25.87 37.7 46.61 .62

90-day minimum 24.01 34.97 47.19 59.26 89.4 .51

1-day maximum 788.6 1,180 1,730 2,170 3,350 .57

3-day maximum 623.67 988 1,155 1,581.17 2,634.67 .51

7-day maximum 441.06 662.71 862.57 1,153.64 1,859.91 .57

30-day maximum 305.24 371.35 546.1 655.08 763.09 .52

90- day maximum 238.48 278.5 368.53 413.01 493.6 .36

 Zero discharge days 0 0 0 0 0 0

7-day minimum/mean annual 

discharge

.06 .08 .12 .15 .18 .51

Timing of annual discharge extremes (Julian day)

Date of minimum 1-day discharge 203 220.5 248 265.5 275.4 .12

Date of maximum 1-day discharge 308.2 26 71 96.5 143 .19

Frequency and duration of high and low pulses 

Times that daily discharge is less 

than the 25th percentile of daily 

discharge (count)

4.6 5 7 8.5 11.4 .5

Days that daily discharge is less 

than the 25th percentile

5.36 8.38 14 18.4 23.78 .72

Times that daily discharge is 

greater than the 75th percentile of 

daily discharge (count)

7.6 9 11 16 17 .64

Days that daily discharge is greater 

than the 75th percentile

3.42 5.06 7.29 9.99 11.95 .68

Rate and frequency of hydrograph changes

Mean of all positive differences 

between consecutive daily 

discharges (rise rate) 

35.06 55.39 68.31 99.31 116.72 .64

Mean of all negative differences 

between consecutive daily 

discharges (fall rate)

-48.82 -43.72 -32.63 -25.31 -17.85 -.56

Number of reversals 93 98.5 105 108 113 .09

Table 19. Flow statistics determined for Indicators of Hydrologic Alteration approach for six streamflow-gaging stations near the 

Assabet and Charles River Basins, Massachusetts.—Continued

Period or condition

Percentile

10th 25th 50th 75th 90th (75-25)/50
Appendix 1: Water-Surface-Profile 

Model Documentation

Appendix 57

Contents

Assabet River near Westborough, Massachusetts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Cold Harbor Brook near Northborough, Massachusetts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Danforth Brook near Hudson, Massachusetts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Fort Meadow Brook near Hudson, Massachusetts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Elizabeth Brook near Stow, Massachusetts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Nashoba Brook at West Concord, Massachusetts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

Charles River near Hopkinton, Massachusetts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Mine Brook near Franklin, Massachusetts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Charles River at Medway, Massachusetts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Tables

1-1. HEC-RAS model calibration to measured streamflows and water-surface 

altitudes at Assabet River near Westborough, Massachusetts . . . . . . . . . . . . . . . . . . . . . . . . . .60

1-2. HEC-RAS model calibration to measured streamflows and water-surface 

altitudes at Cold Harbor Brook near Northborough . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61

1-3. HEC-RAS model calibration to measured streamflows and water-surface 

altitudes at Danforth Brook near Hudson . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62

1-4. HEC-RAS model calibration to measured streamflows and water-surface 

altitudes at Fort Meadow Brook near Hudson . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64

1-5. HEC-RAS model calibration to measured streamflows and water-surface 

altitudes at Elizabeth Brook near Stow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65

1-6. HEC-RAS model calibration to measured streamflows and water-surface 

altitudes at Nashoba Brook at West Concord . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67

1-7. HEC-RAS model calibration to measured streamflows and water-surface 

altitudes at Charles River near Hopkinton. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69

1-8. HEC-RAS model calibration to measured streamflows and water-surface 

altitudes at Mine Brook near Franklin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70

1-9. HEC-RAS model calibration to measured streamflows and water-surface 

altitudes at Charles River at Medway, Massachusetts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71

Appendix 59

Assabet River near Westborough, 

Massachusetts

Six measurements of water surfaces were taken at five 

surveyed cross sections for the purpose of model calibration. 

The calibration discharges were modeled at normal (subcritical) 

depth for the most downstream section and a slope of 

0.0008 ft/ft was set as a downstream boundary condition. This 

slope was calculated from water-surface altitudes at surveyed 

reference points at the most downstream end of the reach. 

Bankfull discharge was estimated by comparison with the 

altitudes of observed bankfull indicators surveyed at the study 

site. 

Initial roughness coefficients for each cross section were 

estimated by solution of Manning’s equation on the basis of the 

measured discharges and surveyed cross-sectional areas and 

slopes. The authors, as required, varied the roughness coefficients for each cross section, until calculated water-surface 

altitudes matched measured water-surface altitudes with 

reasonable accuracy. The variability in the roughness coefficients between river stations (table 1-1) is due to the variability 

of the actual flow length as opposed to the straight-line lengths 

between river stations. The longer path the water takes in 

flowing around the bed material at different discharges changes 

the energy slope in the analysis and is compensated for by 

increasing the roughness coefficient to obtain acceptable model 

calibration. The calibration accuracy was 0.015 ft over the 

entire reach for both measured discharges. 

For all study sites, the HEC-RAS software occasionally 

indicated the need for more cross sections to reduce velocity 

head drops between sections. Addition of interpolated cross 

sections would reduce the number of these messages, but would 

not significantly affect the water-surface profile. 

Cold Harbor Brook near Northborough, 

Massachusetts

Seven measurements of water surfaces were taken at each 

of five surveyed cross sections for the purpose of model calibration. The calibration discharges were modeled at normal 

(subcritical) depth for the most downstream section and a slope 

of 0.0008 ft/ft was set as a downstream boundary condition. 

This slope was calculated from water-surface altitudes at 

surveyed reference points at the most downstream end of the 

reach. Bankfull discharge was estimated by comparison with 

the altitudes of observed bankfull indicators surveyed at the 

study site. 

Initial roughness coefficients for each cross section were 

estimated by solution of Manning’s equation on the basis of the 

measured discharges and surveyed cross-sectional areas and 

slopes. The roughness coefficients for each cross section were 

varied as required until calculated water-surface altitudes 

matched measured water-surface altitudes with reasonable 

accuracy. The variability in the roughness coefficients between 

river stations (table 1-2) is due to the variability of the actual 

flow length as opposed to the straight-line lengths between river 

stations. The longer path the water takes in flowing around the 

bed material at different discharges changes the energy slope in 

the analysis and is compensated for by increasing the roughness 

coefficient to obtain acceptable model calibration. The calibration accuracy was 0.006 ft over the entire reach for both 

measured discharges. 

Danforth Brook near Hudson, 

Massachusetts

Nine measurements of water surfaces were taken at each of 

six surveyed cross sections for the purpose of model calibration. The calibration discharges were modeled at normal 

(subcritical) depth for the most downstream section and a slope 

of 0.01 ft/ft was set as a downstream boundary condition. This 

slope was calculated from water-surface altitudes at surveyed 

reference points at the most downstream end of the reach. 

Bankfull discharge was estimated by comparison with the 

altitudes of observed bankfull indicators surveyed at the study 

site. 

Initial roughness coefficients for each cross section were 

estimated by solution of Manning’s equation on the basis of the 

measured discharges and surveyed cross-sectional areas and 

slopes. The roughness coefficients for each cross section were 

varied as required until calculated water-surface altitudes 

matched measured water-surface altitudes with reasonable 

accuracy. The variability in the roughness coefficients between 

river stations (table 1-3) is due to the variability of the actual 

flow length as opposed to the straight-line lengths between river 

stations. The longer path the water takes in flowing around the 

bed material at different discharges changes the energy slope in 

the analysis and is compensated for by increasing the roughness 

coefficient to obtain acceptable model calibration. The calibration accuracy was 0.037 ft over the entire reach for both 

measured discharges. 
60 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Table 1-1. HEC-RAS model calibration to measured streamflows and water-surface altitudes at Assabet River near Westborough, 

Massachusetts.

[ft, foot; ft/ft, foot per foot; ft2, square foot; ft3/s, cubic foot per second; --, not applicable]

River 

station

Discharge

(ft3/s)

Manning’s 

coefficient

Flow area

(ft2)

Hydraulic

radius

(ft)

Slope

(ft/ft)

Froude

number

Observed

water altitude

(ft)

Calculated

water-surface 

altitude

(ft)

100 0.052 2 4.35 0.43 0.0008 0.00 497.64 497.62

100 .104 1.081 4.59 .45 .0008 .01 497.64 497.64

100 .185 .838 5.73 .52 .0008 .01 497.75 497.75

100 5.22 .079 11.03 .84 .0008 .09 -- 498.2

100 6.84 .062 11.26 .85 .0008 .11 498.22 498.22

100 27.3 .05 24.8 1.37 .0008 .16 -- 499.16

109.99 .052 .035 3.21 .24 .0000 .01 497.64 497.62

109.99 .104 .035 3.52 .26 .0000 .01 497.64 497.64

109.99 .185 .033 5.01 .36 .0000 .01 497.72 497.75

109.99 5.22 .033 11.43 .75 .0002 .09 -- 498.2

109.99 6.84 .033 11.71 .77 .0002 .11 498.21 498.22

109.99 27.3 .035 26.05 1.48 .0003 .14 499.16 499.16

116.71 .052 .183 .29 .04 .0365 .16 497.78 497.78

116.71 .104 .209 .53 .06 .0359 .15 497.81 497.81

116.71 .185 .284 .83 .08 .054 .14 497.85 497.84

116.71 5.22 .05 5.64 .4 .0033 .25 -- 498.21

116.71 6.84 .05 5.91 .42 .0048 .31 498.23 498.23

116.71 27.3 .035 19.2 1.17 .0008 .22 499.14 499.16

127.83 .052 .2 .35 .05 .0195 .11 498.03 497.99

127.83 .104 .202 .5 .06 .0352 .15 498.01 498.01

127.83 .185 .376 1.31 .11 .0234 .07 498.09 498.09

127.83 5.22 .074 5.57 .41 .0072 .26 498.43 498.43

127.83 6.84 .085 6.86 .48 .0085 .25 498.52 498.52

127.83 27.3 .12 17.15 .94 .0154 .29 499.18 499.18

136.38 .052 .13 .34 .05 .0086 .12 498.13 498.09

136.38 .104 .13 .61 .07 .0074 .11 498.13 498.13

136.38 .185 .298 1.44 .14 .0092 .06 498.21 498.21

136.38 5.22 .172 5.76 .33 .0459 .27 498.56 498.56

136.38 6.84 .12 7.08 .37 .0214 .27 498.63 498.63

136.38 27.3 .07 2.5 .82 .0046 .25 499.25 499.25
Appendix 61

Table 1-2. HEC-RAS model calibration to measured streamflows and water-surface altitudes at Cold Harbor Brook near Northborough, 

Massachusetts.

[ft, foot; ft/ft, foot per foot; ft2, square foot; ft3/s, cubic foot per second]

River 

station

Discharge

(ft3/s)

Manning’s

coefficient

Flow area

(ft2)

Hydraulic

radius

(ft)

Slope

(ft/ft)

Froude

number

Observed

water altitude

(ft)

Calculated

water-surface 

altitude

(ft)

100 0.1 0.09 0.79 0.14 0.0008 0.06 498.47 498.47

100 .96 .045 2.25 .31 .0008 .13 498.71 498.71

100 1.9 .024 2.66 .27 .0008 .24 498.76 498.76

100 4.6 .037 6.38 .5 .0008 .18 499.09 499.09

100 5.1 .04 7.27 .55 .0008 .16 499.16 499.16

100 7.3 .045 9.88 .7 .0008 .15 499.36 499.36

100 11.9 .061 16.11 1.05 .0008 .12 499.82 499.82

125.7 .1 .9 1.31 .23 .0152 .03 498.8 498.8

125.7 .96 .193 2.42 .38 .0096 .11 498.99 498.99

125.7 1.9 .065 2.98 .38 .0028 .18 499.07 499.07

125.7 4.6 .049 5.47 .37 .0025 .24 499.32 499.32

125.7 5.1 .046 6.04 .38 .0021 .24 499.36 499.36

125.7 7.3 .095 9.12 .51 .0056 .19 499.55 499.55

125.7 11.9 .1 14.93 .79 .0036 .15 499.88 499.88

131.7 .1 .391 .83 .1 .0202 .06 498.9 498.9

131.7 .96 .09 2 .22 .0064 .18 499.04 499.04

131.7 1.9 .099 2.58 .26 .0147 .25 499.11 499.11

131.7 4.6 .031 5.22 .39 .0012 .25 499.33 499.33

131.7 5.1 .042 5.81 .4 .002 .24 499.37 499.38

131.7 7.3 .274 9.41 .6 .0387 .17 499.65 499.62

131.7 11.9 .152 14.21 .76 .0091 .17 499.92 499.92

137.4 .1 .299 .89 .12 .0082 .06 498.97 498.97

137.4 .96 .592 2.21 .26 .1764 .15 499.15 499.15

137.4 1.9 .168 2.87 .31 .0265 .21 499.22 499.22

137.4 4.6 .036 4.01 .37 .0029 .33 499.34 499.34

137.4 5.1 .034 4.5 .4 .0023 .31 499.37 499.38

137.4 7.3 .085 8.35 .57 .0052 .2 499.68 499.68

137.4 11.9 .041 14.94 .64 .0008 .17 499.93 499.93

147.7 .1 .39 .8 .12 .0177 .06 499.05 499.05

147.7 .96 .026 2.57 .22 .0003 .14 499.23 499.24

147.7 1.9 .039 3.81 .28 .0009 .16 499.34 499.34

147.7 4.6 .285 7.14 .49 .04 .16 499.59 499.59

147.7 5.1 .255 7.45 .5 .0345 .17 499.61 499.61

147.7 7.3 .1 10.16 .61 .0045 .16 499.78 499.78

147.7 11.9 .075 13.48 .79 .0027 .17 499.98 499.99
62 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Table 1-3. HEC-RAS model calibration to measured streamflows and water-surface altitudes at Danforth Brook near Hudson, 

Massachusetts.

[ft, foot; ft/ft, foot per foot; ft2, square foot; ft3/s, cubic foot per second; --, not applicable]

River 

station

Discharge

(ft3/s)

Manning’s

coefficient

Flow area

(ft2)

Hydraulic

radius

(ft)

Slope

(ft/ft)

Froude

number

Observed

water altitude

(ft)

Calculated

water-surface 

altitude

(ft)

18.2 0.009 0.7 0.22 0.08 0.01 0.02 496.55 496.54

18.2 .11 .22 .76 .1 .01 .08 496.63 496.63

18.2 .15 .397 1.5 .14 .01 .05 496.71 496.71

18.2 1.5 .122 3.21 .24 .01 .16 496.86 496.86

18.2 3.1 .108 4.98 .3 .01 .19 496.98 496.98

18.2 4.4 .098 5.9 .35 .01 .22 497.03 497.04

18.2 5.5 .095 6.7 .38 .01 .23 497.09 497.09

18.2 12 .085 10.48 .53 .01 .27 497.3 497.3

18.2 28.5 .053 13.58 .65 .01 .45 497.46 497.46

25.9 .009 1.2 .59 .07 .0049 .01 496.64 496.62

25.9 .11 .521 1.67 .12 .0094 .03 496.72 496.71

25.9 .15 1.144 3.01 .19 .0138 .02 496.81 496.8

25.9 1.5 .222 5.82 .33 .0065 .08 496.97 496.97

25.9 3.1 .2 7.76 .43 .009 .11 497.08 497.08

25.9 4.4 .218 9.52 .51 .0112 .11 497.18 497.18

25.9 5.5 .179 10.38 .55 .009 .12 497.22 497.22

25.9 12 .149 13.88 .71 .0118 .18 497.41 497.41

25.9 28.5 .052 16.11 .81 .005 .34 497.53 497.53

51.9 .009 .05 .11 .03 .0006 .08 496.65 496.65

51.9 .11 .123 .99 .1 .0018 .06 496.8 496.8

51.9 .15 .18 1.8 .16 .0012 .04 496.88 496.88

51.9 1.5 .067 3.91 .28 .0016 .13 497.05 497.05

51.9 3.1 .06 5.8 .35 .0019 .16 497.17 497.17

51.9 4.4 .06 7.48 .43 .0018 .16 497.27 497.27

51.9 5.5 .06 8.36 .47 .002 .17 497.32 497.32

51.9 12 .02 10.6 .56 .0005 .27 497.44 497.44

51.9 28.5 .035 14.17 .7 .0036 .42 497.63 497.63

60.8 .009 .389 .12 .05 .0157 .05 497.1 497.1

60.8 .11 .303 .89 .08 .02 .08 497.22 497.22

60.8 .15 .5 1.54 .1 .0219 .05 497.27 497.27

60.8 1.5 .2 3.82 .22 .0212 .15 497.41 497.41

60.8 3.1 .101 4.37 .24 .0155 .25 -- 497.44

60.8 4.4 .093 5.35 .29 .0137 .27 497.5 497.5

60.8 5.5 .12 6.95 .37 .0156 .23 497.58 497.58

60.8 12 .089 9.3 .47 .0164 .33 497.7 497.7

60.8 28.5 .044 11.93 .58 .0103 .55 497.83 497.83

68.7 .009 1.2 .37 .06 .0145 .02 497.26 497.26

68.7 .11 .624 1.83 .12 .0113 .03 497.39 497.39

68.7 .15 1.374 2.81 .17 .0267 .02 497.45 497.45

68.7 1.5 .244 4.17 .23 .0248 .13 497.53 497.53

68.7 3.1 .084 5.46 .29 .0054 .19 497.6 497.6
Appendix 63

68.7 4.4 0.132 6.98 0.35 0.0127 0.19 497.68 497.68

68.7 5.5 .173 9.05 .43 .0153 .16 497.78 497.78

68.7 12 .104 10.61 .5 .0158 .28 497.85 497.85

68.7 28.5 .055 13.56 .61 .0117 .47 497.99 497.99

81.6 .009 1.8 .77 .08 .0053 .01 497.36 497.36

81.6 .11 .301 1.87 .13 .0021 .03 497.45 497.45

81.6 .15 .345 2.78 .17 .0017 .02 497.51 497.51

81.6 1.5 .08 4.39 .22 .0025 .13 497.6 497.6

81.6 3.1 .095 5.89 .28 .0063 .18 497.68 497.68

81.6 4.4 .093 8.01 .35 .0048 .16 497.77 497.77

81.6 5.5 .079 9.8 .42 .0028 .15 497.85 497.85

81.6 12 .05 11.68 .49 .003 .26 497.93 497.93

81.6 28.5 .042 15.6 .64 .0048 .4 498.1 498.1

Table 1-3. HEC-RAS model calibration to measured streamflows and water-surface altitudes at Danforth Brook near Hudson, 

Massachusetts.—Continued

[ft, foot; ft/ft, foot per foot; ft2, square foot; ft3/s, cubic foot per second; --, not applicable]

River 

station

Discharge

(ft3/s)

Manning’s

coefficient

Flow area

(ft2)

Hydraulic

radius

(ft)

Slope

(ft/ft)

Froude

number

Observed

water altitude

(ft)

Calculated

water-surface 

altitude

(ft)

Fort Meadow Brook near Hudson, 

Massachusetts

Five measurements of water surfaces were taken at each of 

five surveyed cross sections for the purpose of model calibration. The calibration discharges were modeled at normal 

(subcritical) depth for the most downstream section and a slope 

of 0.007 ft/ft was set as a downstream boundary condition. This 

slope was calculated from water-surface altitudes at surveyed 

reference points at the most downstream end of the reach. 

Bankfull discharge was estimated by comparison with the 

altitudes of observed bankfull indicators surveyed at the study 

site. 

Initial roughness coefficients for each cross section were 

estimated by solution of Manning’s equation on the basis of the 

measured discharges and surveyed cross-sectional areas and 

slopes. The roughness coefficients for each cross section were 

varied as required until calculated water-surface altitudes 

matched measured water-surface altitudes with reasonable 

accuracy. The variability in the roughness coefficients between 

river stations (table 1-4) is due to the variability of the actual 

flow length as opposed to the straight-line lengths between river 

stations. The longer path the water takes in flowing around the 

bed material at different discharges changes the energy slope in 

the analysis and is compensated for by increasing the roughness 

coefficient to obtain acceptable model calibration. The calibration accuracy was 0.010 ft over the entire reach for both 

measured discharges. 

Elizabeth Brook near Stow, 

Massachusetts

Seven measurements of water surfaces were taken at each 

of six surveyed cross sections for the purpose of model calibration. The calibration discharges were modeled at normal 

(subcritical) depth for the most downstream section and a slope 

of 0.0197 ft/ft was set as a downstream boundary condition. 

This slope was calculated from water-surface altitudes at 

surveyed reference points at the most downstream end of the 

reach. Bankfull discharge was estimated by comparison with 

the altitudes of observed bankfull indicators surveyed at the 

study site. 

Initial roughness coefficients for each cross section were 

estimated by solution of Manning’s equation on the basis of the 

measured discharges and surveyed cross-sectional areas and 

slopes. The roughness coefficients for each cross section were 

varied as required until calculated water-surface altitudes 

matched measured water-surface altitudes with reasonable 

accuracy. The variability in the roughness coefficients between 

river stations (table 1-5) is due to the variability of the actual 

flow length as opposed to the straight-line lengths between river 

stations. The longer path the water takes in flowing around the 

bed material at different discharges changes the energy slope in 

the analysis and is compensated for by increasing the roughness 

coefficient to obtain acceptable model calibration. The calibration accuracy was 0.019 ft over the entire reach for both 

measured discharges. 
64 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Table 1-4. HEC-RAS model calibration to measured streamflows and water-surface altitudes at Fort Meadow Brook near Hudson, 

Massachusetts.

[ft, foot; ft/ft, foot per foot; ft2, square foot; ft3/s, cubic foot per second]

River 

station

Discharge

(ft3/s)

Manning’s

coefficient

Flow area

(ft2)

Hydraulic

radius

(ft)

Slope

(ft/ft)

Froude

number

Observed

water altitude

(ft)

Calculated

water-surface 

altitude

(ft)

100 1.167 0.092 2.82 0.17 0.0071 0.18 497.87 497.87

100 1.485 .079 2.98 .18 .007 .21 497.88 497.88

100 1.665 .124 4.19 .25 .007 .14 497.95 497.95

100 3.531 .105 5.99 .35 .007 .17 498.06 498.06

100 6.773 .1 8.65 .49 .007 .19 498.22 498.22

114.9 1.167 .194 3.7 .27 .0099 .11 497.98 497.98

114.9 1.485 .125 3.85 .28 .0059 .13 497.99 497.99

114.9 1.665 .142 4.51 .31 .0059 .12 498.06 498.03

114.9 3.531 .14 7.09 .44 .0065 .13 498.21 498.21

114.9 6.773 .13 10.48 .63 .0059 .14 498.42 498.42

124.4 1.167 .18 2.15 .18 .0426 .23 498.08 498.07

124.4 1.485 .152 2.44 .18 .0376 .25 498.09 498.09

124.4 1.665 .15 2.82 .18 .0351 .25 498.12 498.12

124.4 3.531 .069 4.85 .28 .0063 .24 498.24 498.24

124.4 6.773 .012 8.11 .45 .0001 .22 498.41 498.42

133.7 1.167 .181 2.36 .16 .0402 .21 498.39 498.39

133.7 1.485 .131 2.52 .17 .0294 .25 498.4 498.4

133.7 1.665 .118 2.72 .17 .0261 .26 498.41 498.41

133.7 3.531 .074 4.48 .24 .0103 .28 498.51 498.51

133.7 6.773 .05 6.88 .36 .0043 .29 498.64 498.64

150.9 1.167 .174 3.54 .21 .0122 .13 498.52 498.51

150.9 1.485 .18 3.85 .22 .0166 .14 498.54 498.53

150.9 1.665 .18 4.56 .24 .0128 .13 498.58 498.57

150.9 3.531 .17 7.47 .31 .0138 .15 498.71 498.71

150.9 6.773 .09 10.42 .41 .005 .17 498.83 498.83
Appendix 65

Table 1-5. HEC-RAS model calibration to measured streamflows and water-surface altitudes at Elizabeth Brook near Stow, 

Massachusetts.

[ft, foot; ft/ft, foot per foot; ft2, square foot; ft3/s, cubic foot per second]

River 

station

Discharge

(ft3/s)

Manning’s

coefficient

Flow area

(ft2)

Hydraulic

radius

(ft)

Slope

(ft/ft)

Froude

number

Observed

water altitude

(ft)

Calculated

water-surface 

altitude

(ft)

174.35 1.8 0.196 4.76 0.21 0.0197 0.14 497.03 497.03

174.35 4.1 .127 6.15 .26 .0197 .23 497.09 497.09

174.35 9 .092 8.19 .34 .0197 .33 497.18 497.18

174.35 15.3 .07 9.55 .39 .0197 .45 497.24 497.24

174.35 31 .06 13.51 .54 .0197 .55 497.4 497.4

174.35 40.4 .083 19.46 .73 .0197 .43 497.63 497.63

174.35 50.1 .088 25.29 .69 .0197 .42 497.82 497.78

185.68 1.8 .074 3.66 .19 .0056 .2 497.2 497.14

185.68 4.1 .074 5.53 .26 .0082 .25 497.23 497.23

185.68 9 .085 8.48 .37 .0141 .31 497.38 497.37

185.68 15.3 .084 11.73 .4 .0183 .36 497.47 497.47

185.68 31 .048 15.27 .49 .0111 .51 497.58 497.58

185.68 40.4 .055 21.54 .67 .0081 .4 497.79 497.78

185.68 50.1 .038 24.13 .74 .0041 .42 497.85 497.86

202.05 1.8 .07 2.64 .15 .0131 .31 497.34 497.33

202.05 4.1 .067 4.55 .22 .0123 .34 497.42 497.43

202.05 9 .044 6.63 .3 .008 .43 497.53 497.53

202.05 15.3 .053 9.12 .39 .0126 .47 497.67 497.64

202.05 31 .028 12 .4 .0082 .72 497.71 497.72

202.05 40.4 .039 20.48 .64 .0049 .43 498.05 497.99

202.05 50.1 .04 22.3 .69 .0059 .47 498.01 498.05

213.57 1.8 .1 4.16 .17 .0092 .19 497.51 497.47

213.57 4.1 .088 5.9 .23 .012 .25 497.55 497.54

213.57 9 .059 9.03 .34 .0066 .3 497.65 497.66

213.57 15.3 .073 12.51 .47 .0098 .31 497.8 497.8
66 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

213.57 31 0.1 17.51 0.64 0.0258 0.39 497.98 497.98

213.57 40.4 .088 23.28 .83 .0134 .33 498.23 498.2

213.57 50.1 .06 24.62 .87 .008 .38 498.21 498.24

229.45 1.8 .07 2.18 .16 .0172 .36 497.67 497.66

229.45 4.1 .057 3.84 .19 .0156 .44 497.75 497.75

229.45 9 .052 5.37 .23 .0239 .61 497.82 497.82

229.45 15.3 .058 9 .37 .0163 .49 497.98 497.98

229.45 31 .048 14.71 .57 .0098 .49 498.21 498.21

229.45 40.4 .055 18.74 .69 .0103 .45 498.36 498.36

229.45 50.1 .055 19.25 .71 .0146 .54 498.38 498.38

241.46 1.8 .057 2.61 .13 .0108 .34 497.69 497.83

241.46 4.1 .135 6.63 .26 .0186 .21 498 498

241.46 9 .13 9.62 .37 .025 .27 498.13 498.12

241.46 15.3 .095 12.98 .49 .0147 .3 498.25 498.25

241.46 31 .062 17.6 .64 .0099 .39 498.42 498.42

241.46 40.4 .081 22.94 .79 .0123 .35 498.62 498.62

241.46 50.1 .09 24.59 .83 .0191 .39 498.67 498.67

Table 1-5. HEC-RAS model calibration to measured streamflows and water-surface altitudes at Elizabeth Brook near Stow, 

Massachusetts.—Continued

[ft, foot; ft/ft, foot per foot; ft2, square foot; ft3/s, cubic foot per second]

River 

station

Discharge

(ft3/s)

Manning’s

coefficient

Flow area

(ft2)

Hydraulic

radius

(ft)

Slope

(ft/ft)

Froude

number

Observed

water altitude

(ft)

Calculated

water-surface 

altitude

(ft)

Nashoba Brook at West Concord, 

Massachusetts

Nine measurements of water surfaces were taken at each of 

four surveyed cross sections for the purpose of model calibration. The calibration discharges were modeled at normal 

(subcritical) depth for the most downstream section and a slope 

of 0.0143 ft/ft was set as a downstream boundary condition. 

This slope was calculated from water-surface altitudes at 

surveyed reference points at the most downstream end of the 

reach. Bankfull discharge was estimated by comparison with 

the altitudes of observed bankfull indicators surveyed at the 

study site. 

Initial roughness coefficients for each cross section were 

estimated by solution of Manning’s equation on the basis of the 

measured discharges and surveyed cross-sectional areas and 

slopes. The roughness coefficients for each cross section were 

varied as required until calculated water-surface altitudes 

matched measured water-surface altitudes with reasonable 

accuracy. The variability in the roughness coefficients between 

river stations (table 1-6) is due to the variability of the actual 

flow length as opposed to the straight-line lengths between river 

stations. The longer path the water takes in flowing around the 

bed material at different discharges changes the energy slope in 

the analysis and is compensated for by increasing the roughness 

coefficient to obtain acceptable model calibration. The calibration accuracy was 0.008 ft over the entire reach for both 

measured discharges. 
Appendix 67

Table 1-6. HEC-RAS model calibration to measured streamflows and water-surface altitudes at Nashoba Brook at West Concord, 

Massachusetts.

[ft, foot; ft/ft, foot per foot; ft2, square foot; ft3/s, cubic foot per second]

River 

station

Discharge

(ft3/s)

Manning’s

coefficient

Flow area

(ft2)

Hydraulic

radius

(ft)

Slope

(ft/ft)

Froude

number

Observed

water altitude

(ft)

Calculated

water-surface 

altitude

(ft)

100 1 0.26 8.65 0.39 0.0014 0.03 496.57 496.57

100 2.5 .172 11.95 .51 .0014 .05 496.72 496.72

100 6.7 .101 16.22 .64 .0014 .09 496.9 496.9

100 7.3 .1 16.98 .67 .0014 .09 496.93 496.93

100 13.9 .083 22.71 .86 .0014 .11 497.15 497.15

100 20.6 .073 26.9 1 .0014 .13 497.32 497.32

100 27.3 .064 29.54 1.08 .0014 .15 497.42 497.42

100 30 .067 32.21 1.13 .0014 .15 497.52 497.52

100 74.9 .049 47.43 1.54 .0014 .22 498.07 498.07

120.3 1 .16 2.32 .16 .025 .19 497 497

120.3 2.5 .15 4.25 .2 .0313 .23 497.1 497.1

120.3 6.7 .058 5.49 .25 .0145 .43 497.16 497.16

120.3 7.3 .084 6.72 .3 .019 .35 497.21 497.21

120.3 13.9 .045 8.72 .38 .0084 .45 497.3 497.3

120.3 20.6 .037 11.26 .49 .0053 .46 497.42 497.42

120.3 27.3 .033 13.38 .57 .0043 .47 497.51 497.51

120.3 30 .023 14.49 .62 .002 .46 497.56 497.56

120.3 74.9 .032 27.98 1.05 .0031 .45 498.13 498.13

142.5 1 .17 3.28 .17 .0129 .13 497.27 497.27

142.5 2.5 .05 4.27 .2 .0033 .23 497.32 497.32

142.5 6.7 .04 6.78 .29 .0037 .32 497.43 497.43

142.5 7.3 .04 7.61 .32 .003 .3 497.44 497.46

142.5 13.9 .04 9.85 .41 .0047 .38 497.57 497.56

142.5 20.6 .05 12.61 .52 .0072 .4 497.67 497.68

142.5 27.3 .05 14.57 .59 .008 .42 497.76 497.76

142.5 30 .045 14.73 .6 .0074 .46 497.76 497.77

142.5 74.9 .02 25.65 .97 .0016 .51 498.18 498.2

164.5 1 .045 2.57 .14 .0018 .18 497.35 497.35

164.5 2.5 .056 3.69 .2 .0056 .26 497.43 497.41

164.5 6.7 .065 6.29 .32 .0097 .32 497.55 497.55

164.5 7.3 .065 6.66 .34 .0097 .33 497.58 497.57

164.5 13.9 .055 9.2 .44 .0093 .39 497.7 497.7

164.5 20.6 .045 11.75 .54 .0064 .41 497.82 497.82

164.5 27.3 .04 13.49 .6 .006 .45 497.91 497.9

164.5 30 .04 13.61 .6 .0069 .49 497.92 497.91

164.5 74.9 .141 22.68 .86 .1176 .61 498.32 498.29
68 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Charles River near Hopkinton, 

Massachusetts

Three measurements of water surfaces were taken at each 

of seven surveyed cross sections for the purpose of model 

calibration. The calibration discharges were modeled at normal 

(subcritical) depth for the most downstream section and a slope 

of 0.002 ft/ft was set as a downstream boundary condition. This 

slope was calculated from water-surface altitudes at surveyed 

reference points at the most downstream end of the reach. 

Bankfull discharge was estimated by comparison with the 

altitudes of observed bankfull indicators surveyed at the study 

site. 

Initial roughness coefficients for each cross section were 

estimated by solution of Manning’s equation on the basis of the 

measured discharges and surveyed cross-sectional areas and 

slopes. The roughness coefficients for each cross section were 

varied as required until calculated water-surface altitudes 

matched measured water-surface altitudes with reasonable 

accuracy. The variability in the roughness coefficients between 

river stations (table 1-7) is due to the variability of the actual 

flow length as opposed to the straight-line lengths between river 

stations. The longer path the water takes in flowing around the 

bed material at different discharges changes the energy slope in 

the analysis and is compensated for by increasing the roughness 

coefficient to obtain acceptable model calibration. The calibration accuracy was 0.006 ft over the entire reach for both 

measured discharges. 

Mine Brook near Franklin, 

Massachusetts

Five measurements of water surfaces were taken at each of 

seven surveyed cross sections for the purpose of model calibration. The calibration discharges were modeled at normal 

(subcritical) depth for the most downstream section and a slope 

of 0.019 ft/ft was set as a downstream boundary condition. This 

slope was calculated from water-surface altitudes at surveyed 

reference points at the most downstream end of the reach. 

Bankfull discharge was estimated by comparison with the 

altitudes of observed bankfull indicators surveyed at the study 

site. 

Initial roughness coefficients for each cross section were 

estimated by solution of Manning’s equation on the basis of the 

measured discharges and surveyed cross-sectional areas and 

slopes. The roughness coefficients for each cross section were 

varied as required until calculated water-surface altitudes 

matched measured water-surface altitudes with reasonable 

accuracy. The variability in the roughness coefficients between 

river stations (table 1-8) is due to the variability of the actual 

flow length as opposed to the straight-line lengths between river 

stations. The longer path the water takes in flowing around the 

bed material at different discharges changes the energy slope in 

the analysis and is compensated for by increasing the roughness 

coefficient to obtain acceptable model calibration. The calibration accuracy was 0.014 ft over the entire reach for both 

measured discharges. 

Charles River at Medway, 

Massachusetts

Nine measurements of water surfaces were taken at each of 

nine surveyed cross sections the study reach for the purpose of 

model calibration. The calibration discharges were modeled at 

normal (subcritical) depth for the most downstream section. 

The downstream boundary was set to known elevations determined from the stage discharge relation for streamgaging 

station at Charles River at Medway (01103200) for the 

discharges that corresponded to when water surface measurements were made at the riffle sections. Bankfull discharge was 

estimated by comparison with the altitudes of observed bankfull 

indicators surveyed at the study site. 

Initial roughness coefficients for each cross section were 

estimated by solution of Manning’s equation on the basis of the 

measured discharges and surveyed cross-sectional areas and 

slopes. The roughness coefficients for each cross section were 

varied as required until calculated water-surface altitudes 

matched measured water-surface altitudes with reasonable 

accuracy. The variability in the roughness coefficients between 

river stations (table 1-9) is due to the variability of the actual 

flow length as opposed to the straight-line lengths between river 

stations. The longer path the water takes in flowing around the 

bed material at different discharges changes the energy slope in 

the analysis and is compensated for by increasing the roughness 

coefficient to obtain acceptable model calibration. The calibration accuracy was 0.097 ft over the entire reach for both 

measured discharges. 
Appendix 69

Table 1-7. HEC-RAS model calibration to measured streamflows and water-surface altitudes at Charles River near Hopkinton, 

Massachusetts.

[ft, foot; ft/ft, foot per foot; ft2, square foot; ft3/s, cubic foot per second; --, not applicable]

River 

station

Discharge

(ft3/s)

Manning’s

coefficient

Flow area

(ft2)

Hydraulic

radius

(ft)

Slope

(ft/ft)

Froude

number

Observed

water altitude

(ft)

Calculated

water-surface 

altitude

(ft)

93.91 0.028 0.599 0.74 0.2 0.002 0.01 498.1 498.1

93.91 2.551 .03 2.28 .35 .002 .32 498.44 498.44

93.91 8.408 .053 7.31 .74 .002 .22 499.12 499.12

101.39 .028 .8 .35 .11 .0325 .04 -- 498.2

101.39 2.551 .07 2.37 .33 .0101 .33 498.58 498.58

101.39 8.408 .035 7.64 .63 .001 .24 499.13 499.13

133.22 .028 .355 .65 .22 .0008 .02 498.27 498.27

133.22 2.551 .015 2.31 .33 .0005 .33 498.62 498.62

133.22 8.408 .032 6.41 .69 .0011 .27 499.16 499.16

144.91 .028 1.2 .55 .12 .0286 .03 -- 498.38

144.91 2.551 .035 2.1 .32 .0034 .37 498.66 498.66

144.91 8.408 .035 5.75 .65 .0017 .31 499.17 499.17

157.84 .028 2.478 .87 .17 .0318 .01 498.92 498.92

157.84 2.551 .15 2.01 .33 .0661 .38 499.14 499.14

157.84 8.408 .16 6.17 .54 .0423 .32 499.56 499.56

166.01 .028 3 .85 .17 .0471 .01 499.39 499.37

166.01 2.551 .2 2.86 .26 .0626 .3 499.65 499.65

166.01 8.408 .24 7.75 .52 .0623 .26 500.03 500.04

184.11 .028 3 1.37 .32 .0063 .01 499.62 499.61

184.11 2.551 .169 3.91 .46 .0105 .16 500.04 500.04

184.11 8.408 .062 5.73 .58 .0056 .33 500.26 500.26
70 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

Table 1-8. HEC-RAS model calibration to measured streamflows and water-surface altitudes at Mine Brook near Franklin, 

Massachusetts.

[ft, foot; ft/ft, foot per foot; ft2, square foot; ft3/s, cubic foot per second]

River 

station

Discharge

(ft3/s)

Manning’s

coefficient

Flow area

(ft2)

Hydraulic

radius

(ft)

Slope

(ft/ft)

Froude

number

Observed

water altitude

(ft)

Calculated

water-surface 

altitude

(ft)

100 2.03 0.16 4.14 0.24 0.019 0.17 495.89 495.89

100 2.3 .197 5.16 .28 .019 .15 495.95 495.95

100 4 .175 6.88 .35 .019 .17 496.04 496.04

100 17.2 .123 14.34 .61 .019 .26 496.42 496.4

100 70 .113 33.18 1.13 .019 .34 497.19 497.19

112.91 2.03 .068 3.57 .21 .0053 .22 496 496

112.91 2.3 .078 4.45 .25 .0047 .18 496.05 496.05

112.91 4 .042 5.4 .28 .0024 .25 496.1 496.1

112.91 17.2 .028 12.6 .55 .0015 .32 496.44 496.44

112.91 70 .025 32.17 1.06 .001 .37 497.22 497.22

123.6 2.03 .087 3.75 .26 .0061 .19 496.16 496.17

123.6 2.3 .078 4.05 .28 .005 .19 496.14 496.19

123.6 4 .06 4.73 .31 .0055 .26 496.23 496.23

123.6 17.2 .11 12.67 .7 .0164 .28 496.71 496.71

123.6 70 .055 24.49 1.03 .0087 .48 497.34 497.34

143.62 2.03 .052 3.71 .28 .002 .18 496.23 496.23

143.62 2.3 .079 4.29 .31 .0039 .17 496.28 496.28

143.62 4 .036 4.55 .33 .002 .27 496.29 496.3

143.62 17.2 .032 11.98 .72 .0015 .29 496.78 496.78

143.62 70 .03 23.05 1.2 .0029 .48 497.42 497.42

164.85 2.03 .07 3.29 .28 .0047 .2 496.3 496.3

164.85 2.3 .041 3.64 .3 .0015 .2 496.32 496.33

164.85 4 .055 4.09 .32 .006 .3 496.36 496.36

164.85 17.2 .019 10.08 .66 .0008 .36 496.75 496.79

164.85 70 .09 21.31 1.21 .0289 .5 497.55 497.55

173.65 2.03 .09 2.15 .21 .027 .36 496.45 496.45

173.65 2.3 .103 2.46 .21 .0324 .35 496.48 496.48

173.65 4 .053 3.02 .23 .0163 .49 496.49 496.53

173.65 17.2 .1 10.63 .66 .0207 .34 497.04 497.04

173.65 70 .11 23.6 1.22 .033 .45 497.86 497.85

187.25 2.03 .129 3.59 .21 .0199 .22 496.97 496.96

187.25 2.3 .265 5.23 .28 .0338 .15 497.05 497.05

187.25 4 .142 5.77 .31 .0212 .22 497.08 497.08

187.25 17.2 .101 11.93 .59 .0191 .33 497.41 497.41

187.25 70 .1 21.89 .99 .0455 .55 497.9 497.9
Appendix 71

Table 1-9. HEC-RAS model calibration to measured streamflows and water-surface altitudes at Charles River at Medway, 

Massachusetts.

[ft, foot; ft/ft, foot per foot; ft2, square foot; ft3/s, cubic foot per second; --, not applicable]

River 

station

Discharge

(ft3/s)

Manning’s

coefficient

Flow area

(ft2)

Hydraulic

radius

(ft)

Slope

(ft/ft)

Froude

number

Observed

water altitude

(ft)

Calculated

water-surface 

altitude

(ft)

100 8.2 0.035 14.35 0.32 0.0008 0.18 -- 787.99

100 10.5 .035 16.63 .35 .0009 .19 -- 788.04

100 12.6 .035 18.92 .35 .001 .2 -- 788.09

100 14.2 .035 20.27 .37 .001 .2 -- 788.11

100 19.1 .035 23.53 .43 .0011 .22 -- 788.17

100 32.6 .035 28.86 .52 .0017 .27 -- 788.27

100 44 .035 33.44 .6 .0019 .3 -- 788.35

100 49.7 .035 37.43 .67 .0017 .28 -- 788.43

100 76.2 .035 43.72 .77 .0024 .35 -- 788.54

374.2 8.2 .035 12.73 .47 .0006 .17 -- 788.19

374.2 10.5 .035 14.61 .51 .0007 .18 -- 788.26

374.2 12.6 .033 16.2 .52 .0007 .19 -- 788.31

374.2 14.2 .032 17.09 .53 .0007 .2 -- 788.34

374.2 19.1 .028 19.56 .59 .0007 .22 -- 788.42

374.2 32.6 .022 23.85 .68 .0007 .29 -- 788.54

374.2 44 .021 27.72 .75 .0007 .32 -- 788.65

374.2 49.7 .021 30.05 .79 .0008 .33 788.68 788.71

374.2 76.2 .023 38.61 .96 .001 .35 -- 788.93

580.9 8.2 .035 27.65 .44 .0001 .08 788.27 788.25

580.9 1.5 .032 31.79 .48 .0001 .08 788.31 788.32

580.9 12.6 .03 35.15 .51 .0001 .09 788.31 788.37

580.9 14.2 .028 37.03 .53 .0001 .09 -- 788.4

580.9 19.1 .024 42.51 .58 .0001 .1 788.39 788.47

580.9 32.6 .025 54.2 .67 .0002 .13 788.56 788.63

580.9 44 .036 68.82 .68 .0004 .14 788.71 788.8

580.9 49.7 .042 76.6 .75 .0005 .13 788.76 788.87

580.9 76.2 .063 107.41 1.04 .0009 .12 789.24 789.18

641.1 8.2 .5 5.71 .33 1.0067 .43 788.49 788.27

641.1 10.5 .5 6.74 .37 1.0197 .44 788.47 788.33

641.1 12.6 .5 7.54 .4 1.0773 .46 788.47 788.37

641.1 14.2 .5 7.98 .41 1.195 .49 788.41 788.39

641.1 19.1 .5 9.47 .37 1.7431 .58 788.62 788.46

641.1 32.6 .5 15.01 .36 2.0714 .63 788.77 788.63

641.1 44 .482 27.58 .46 .761 .41 788.93 788.87

641.1 49.7 .39 33.42 .53 .3534 .36 -- 788.96

641.1 76.2 .088 54.49 .81 .0091 .27 789.28 789.29

691.6 8.2 .047 12.23 .22 .0033 .25 788.84 788.9

691.6 10.5 .048 14.55 .26 .0032 .25 788.92 788.94

691.6 12.6 .049 16.64 .3 .0031 .24 788.94 788.98

691.6 14.2 .05 18.1 .32 .0031 .24 788.92 789

691.6 19.1 .043 20.48 .36 .0028 .27 789 789.05
72 Determining Streamflow Requirements for Aquatic Habitat Protection, Assabet and Charles Rivers, Eastern MA, 2000–02

691.6 32.6 0.032 24.84 0.44 0.0024 0.35 789.12 789.12

691.6 44 .024 27.8 .48 .0017 .4 789.2 789.18

691.6 49.7 .02 29.25 .51 .0013 .42 -- 789.2

691.6 76.2 .034 45.14 .76 .0021 .34 789.21 789.47

1284 8.2 .06 22.65 .52 .0005 .09 -- 789.52

1284 10.5 .06 25.92 .58 .0005 .09 -- 789.59

1284 12.6 .06 28.56 .63 .0006 .1 -- 789.65

1284 14.2 .06 30.62 .66 .0006 .1 -- 789.7

1284 19.1 .06 35.86 .72 .0007 .11 -- 789.81

1284 32.6 .06 45.95 .87 .001 .13 -- 790

1284 44 .06 50.48 .94 .0013 .16 -- 790.09

1284 49.7 .06 51 .95 .0017 .18 -- 790.1

1284 76.2 .06 72.16 1.26 .0013 .17 790.48 790.48

1466.3 8.2 .04 3.81 .17 .0345 .91 790.26 790.11

1466.3 10.5 .04 4.21 .19 .0412 1.01 790.33 790.13

1466.3 12.6 .04 4.77 .21 .0401 1.01 790.4 790.15

1466.3 14.2 .04 5.23 .23 .0384 1 790.35 790.17

1466.3 19.1 .04 6.45 .27 .0367 1.01 -- 790.23

1466.3 32.6 .07 14.72 .4 .0367 .61 790.61 790.49

1466.3 44 .07 21.63 .55 .0204 .48 -- 790.67

1466.3 49.7 .07 25.27 .62 .0164 .44 -- 790.76

1466.3 76.2 .07 35.84 .8 .0136 .42 791.05 791.01

1481.8 8.2 .07 7.83 .26 .0148 .36 790.5 790.5

1481.8 10.5 .064 9.08 .29 .013 .38 790.54 790.54

1481.8 12.6 .06 9.96 .31 .0126 .4 790.7 790.57

1481.8 14.2 .057 10.62 .32 .0121 .42 790.56 790.59

1481.8 19.1 .051 12.23 .35 .0117 .46 -- 790.63

1481.8 32.6 .043 17.15 .45 .0091 .5 790.73 790.77

1481.8 44 .044 21.27 .52 .0089 .5 -- 790.87

1481.8 49.7 .044 23.83 .57 .0083 .49 -- 790.93

1481.8 76.2 .046 33.26 .73 .0076 .47 791.19 791.15

1498.9 8.2 .11 10.81 .31 .0149 .24 790.76 790.76

1498.9 10.5 .09 11.4 .32 .014 .28 790.76 790.78

1498.9 12.6 .075 11.83 .33 .0127 .32 790.84 790.79

1498.9 14.2 .067 12.1 .34 .0118 .35 790.8 790.8

1498.9 19.1 .059 13.8 .37 .0115 .4 -- 790.84

1498.9 32.6 .053 17.8 .45 .0126 .48 790.97 790.95

1498.9 44 .055 22.43 .52 .0126 .48 -- 791.06

1498.9 49.7 .059 24.7 .55 .014 .47 -- 791.11

1498.9 76.2 .065 35.15 .67 .0145 .46 791.38 791.33

Table 1-9. HEC-RAS model calibration to measured streamflows and water-surface altitudes at Charles River at Medway, 

Massachusetts.—Continued

[ft, foot; ft/ft, foot per foot; ft2, square foot; ft3/s, cubic foot per second; --, not applicable]

River 

station

Discharge

(ft3/s)

Manning’s

coefficient

Flow area

(ft2)

Hydraulic

radius

(ft)

Slope

(ft/ft)

Froude

number

Observed

water altitude

(ft)

Calculated

water-surface 

altitude

(ft)