Evaluation of Streamflow Requirements for Habitat Protection by Comparison to Streamflow Characteristics at Index Streamflow-Gaging Stations in Southern New England By David S. Armstrong, Gene W. Parker, and Todd A. Richards (Massachusetts Division of Fisheries and Wildlife) Water-Resources Investigations Report 03-4332—Version 1.10

ABSTRACT

Streamflow characteristics and methods for determining streamflow requirements for habitat protection were investigated at 23 active index streamflow-gaging stations in southern New England. Fish communities sampled near index streamflow-gaging stations in Massachusetts have a high percentage of fish that require flowing-water habitats for some or all of their life cycle. The relatively unaltered flow condition at these sites was assumed to be one factor that has contributed to this condition.

Monthly flow durations and low flow statistics were determined for the index streamflow-gaging stations for a 25-year period from 1976 to 2000. Annual hydrographs were prepared for each index station from median streamflows at the 50-percent monthly flow duration, normalized by drainage area. A median monthly flow of 1 ft3/s/mi2 was used to split hydrographs into a high-flow period (November–May), and a low-flow period (June–October). The hydrographs were used to classify index stations into groups with similar median monthly flow durations. Index stations were divided into four regional groups, roughly paralleling the coast, to characterize streamflows for November to May; and into two groups, on the basis of base-flow index and percentage of sand and gravel in the contributing area, for June to October.

For the June to October period, for index stations with a high base-flow index and contributing areas greater than 20 percent sand and gravel, median streamflows at the 50-percent monthly flow duration, normalized by drainage area, were 0.57, 0.49, and 0.46 ft3/s/mi2 for July, August, and September, respectively. For index stations with a low base-flow index
and contributing areas less than 20 percent sand and gravel, median streamflows at the 50-percent monthly flow duration, normalized by drainage area, were 0.34, 0.28, and 0.27 ft3/s/mi2 for July, August, and September, respectively. Streamflow variability between wet and dry years can be characterized by use of the interquartile range of median streamflows at selected monthly flow durations. For example, the median Q50 discharge for August had an interquartile range of 0.30 to 0.87 ft3/s/mi2 for the high-flow group and 0.16 to 0.47 ft3/s/mi2 for the
low-flow group.

Streamflow requirements for habitat protection were determined for 23 index stations by use of three methods based on hydrologic records, the Range of Variability Approach, the Tennant method, and the New England Aquatic-Base-Flow method. Normalized flow management targets determined by the Range of Variability Approach for July, August, and September ranged between 0.21 and 0.84 ft3/s/mi2 for the low monthly flow duration group, and 0.37 and 1.27 ft3/s/mi2 for the high monthly flow duration group. Median streamflow requirements for habitat protection during summer for the 23 index streamflow-gaging stations determined by the Tennant method, normalized by drainage area, were 0.81, 0.61, and 0.21 ft3/s/mi2 for the Tennant 40-, 30-, and 10-percent of the mean annual flow methods, representing good, fair, and poor stream habitat conditions in summer, according to Tennant. New England Aquatic-Base-Flow streamflow requirements for habitat protection during summer were determined from median of monthly mean flows for August for index streamflow-gaging stations having drainage areas greater than 50 mi2. For five index streamflow-gaging stations in the low median monthly flow group, the average median monthly mean streamflow for August, normalized by drainage area, was 0.48 ft3/s/mi2.

Streamflow requirements for habitat protection were determined for riffle habitats near 10 index stations by use of two methods based on hydraulic ratings, the Wetted-Perimeter and R2Cross methods. Hydraulic parameters required by these methods were simulated by calibrated HEC-RAS models. Wetted-Perimeter streamflow requirements for habitat protection, normalized by drainage area, ranged between 0.13 and 0.58 ft3/s/mi2, and had a median value of 0.37 ft3/s/mi2. Streamflow requirements determined by the R2Cross 3-of-3 criteria method ranged between 0.39 and 2.1 ft3/s/mi2, and had a median of 0.84 ft3/s/mi2. Streamflow requirements determined by the R2Cross 2-of-3 criteria method, normalized by drainage area, ranged between 0.16 and 0.85 ft3/s/mi2 and had a median of 0.36 ft3/s/mi2, respectively. Streamflow requirements determined by the different methods were evaluated by comparison to streamflow statistics from the index streamflow-gaging stations.

CONTENTS

Abstract. 1

Introduction 2

Purpose and Scope 2

Description of Study Area 2

Previous Studies. 4

Relations among Flow Regimes, Stream Processes, and Aquatic Habitat 5

Acknowledgments 5

Streamflow Characteristics at Index Streamflow-Gaging Stations in Southern New England 5

Index Stations 6

Selection Criteria 6

Basin Characteristics 6

Fish-Community Sampling and Assessment 6

Flow Statistics for Index Stations 10

Flow-Duration Statistics 11

Low-Flow Statistics 19

Characterization of Flow Regimes for Index Stations 19

Classification of Index Stations 19

Flow Regimes for Index-Station Groups 22

Streamflow Variability for Groups of Index Stations 24

Streamflow Requirements for Habitat Protection at Index Stations in Southern New England 27

Methods for Determining Streamflow Requirements Based on Hydrologic Records 28

Range of Variability Approach 28

Tennant Method 29

New England Aquatic-Base-Flow Method 29

Streamflow Requirements Determined from Hydrologic Records 30

Range of Variability Approach 30

Tennant Method 30

New England Aquatic-Base-Flow Method 34

Methods for Determining Streamflow Requirements Based on Hydraulic Ratings 34

Water-Surface-Profile Modeling 34

Wetted-Perimeter Method 36

R2Cross Method 36

Streamflow Requirements Determined from Hydraulic Ratings 38

Wetted-Perimeter Method 38

R2Cross Method 39

Evaluation of Streamflow Requirements 41

Suggestions for Further Study 44

Summary and Conclusions 44

References Cited 45

Appendix 1: Annual Flow-Duration Curves for 10 Index Streamflow-Gaging Stations in southern New England 59

Appendix 2: Procedures for Application of the Wetted-Perimeter Method 67

Appendix 3: Study-Site Descriptions , Documentation of Input, Calibration Data for HEC-RAS Models, and Hydraulic Variables Simulated by Calibrated HEC-RAS Models for 10 Index Streamflow-Gaging Stations in Southern New England 71

FIGURES

1. Map showing location of index stations, and riffle study sites, southern New England 3

2. Photograph showing Massachusetts Division of Fisheries and Wildlife and U.S. Geological Survey personnel identifying, counting, and measuring fish collected by electrofishing 9

3, 4. Graphs showing:

3. Annual flow-duration curves for Wood River near Arcadia, RI (01117800), and Green River at Williamstown, MA (01333000), for water years 1976–2000 13

4. August streamflows at the Sevenmile River near Spencer, MA (01175670):

A, August daily mean hydrographs for 1990, 1978, and 1977 water years;

B, August monthly fduration curves for 1990, 1978, and 1977 water years; and

C, August median monthly duration curve, for water year 1976–2000 15

5. Map showing classification of index streamflow-gaging stations in southern New England 23

6–8. Graphs showing:

6. Regionalized medians of the 50-percent monthly flow durations, normalized by drainage area, for index stations grouped by A, geographic region, November– May; and B, magnitude of median 50-percent monthly flow durations, June–October 24

7. Median monthly flow durations, normalized by drainage area, and the interquartile range about the 25-, 50-, and 75-percent monthly flow durations for June through October for the high- and low- median monthly flow-duration groups for index stations: A, June; B, July; C, August; D, September; and E, October 25

8. Median of average daily discharge for n-day low-flow statistics, normalized by drainage area, for the high- and low-median monthly flow-duration groups, for index stations for water years 1976–2000 27

9. Schematic showing A, cross section of stream channel; and B, relation between wetted perimeter and discharge 37

10. Graphs showing comparison of Range of Variability Approach flow-management targets, normalized by drainage area, to the 25th and 75th percentiles of the 50-percent monthly flow duration for the: A, low monthly flow-duration group; B, high monthly flow-duration group 43

TABLES

1. Locations, descriptions, and basin characteristics of index stations for flow statistics and determination of streamflow requirements in southern New England 7

2. Scientific names and habitat-use classifications of fish in southern New England 10

3. Percentages of fish in each habitat-use classification sampled in flowing reaches of several river basins in Massachusetts 11

4. Location and descriptions of fish sampling stations, fish-sampling date, electrofishing methods and effort, reach length, reach width, and fish numbers and species for 10 rivers in Massachusetts 12

5. Habitat-use classifications for reaches near 10 index stations in Massachusetts 12

6. Median and interquartile ranges for 50-percent monthly flow-duration discharges (Q50), normalized by drainage area, for 23 index streamflow-gaging stations in southern New England for water years 1976–2000 16

7. Median and interquartile range for n-day low-flow statistics, normalized by drainage area, for 23 index stations in southern New England for water years 1976–2000 20

8. Range of Variability Approach: flow statistics for characterization of hydrologic variation 28

9. Relations between aquatic-habitat condition and mean annual flow described by the Tennant method for small streams 29

10. Seasonal New England Aquatic-Base-Flow default streamflow requirements 29

11. Range of Variability Approach flow-management targets as defined by the 25th and 75th percentiles of monthly mean flows, normalized by drainage area, for index streamflow-gaging stations in southern New England for water years 1976–2000 31

12. The mean annual-flow statistic used by the Tennant and Canadian Atlantic Provinces methods and the streamflows representing summer habitat conditions determined by percentages of the mean annual flow, normalized for drainage area, at 23 index stations in southern New England 33

13. Hydraulic criteria for determination of R2Cross streamflow requirements for habitat protection 38

14. Average streamflow requirements determined by the Wetted-Perimeter method for 10 index streamflow-gaging stations in southern New England 38

15. Streamflow requirements and corresponding flow durations determined by the R2Cross method for 10 index streamflow-gaging stations in southern New England 40

16. Field-determined bankfull discharges for 10 index streamflow-gaging stations in southern New England 40

17. Summer streamflow requirements and corresponding flow durations for the high-flow group and low-flow groups of index streamflow-gaging stations in southern New England 42

18. Flow statistics determined by the Indicators of Hydrologic Alteration Approach, normalized by drainage area, for index streamflow-gaging stations: Wood River, Little River, Squannacook River, Green River in Williamstown, Branch River, and South River 51

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