Office of Research and Development

National Risk Management Research Laboratory, Ada, Oklahoma 74820

Assessment of Near-Stream 

Ground Water-Surface Water 

Interaction (GSI) of a Degraded 

Stream before Restoration

EPA 600/R-07/058 | August 2008 | www.epa.gov/ada

Office of Research and Development

National Risk Management Research Laboratory, Ada, Oklahoma 74820

Elise A. Striz 

Robert S. Kerr Environmental Research Center

Paul M. Mayer

Project Officer, 

Robert S. Kerr Environmental Research Center

Assessment of Near-Stream 

Ground Water-Surface Water 

Interaction (GSI) of a Degraded 

Stream before Restoration
ii

Notice

The U.S. Environmental Protection agency through its Office of Research and 

Development funded the research described here. This research report has been 

subjected to the Agency’s peer and administrative review and approved for publication as an EPA document. Mention of trade names or commercial products does not 

constitute endorsement or recommendation for use.

Striz, Elise A. and Paul M. Mayer. Assessment of Near-Stream Ground 

Water-Surface Water Interaction (GSI) of a Degraded Stream before Restoration” 

EPA/600/R-07/058. U.S. Environmental Protection Agency, 2008.

Front Cover photos:

A view of Minebank Run looking upstream at Transect 3 in July 2002.

Aerial view of Minebank Run taken from low-level blimp platform 

(photo courtesy of Ken Jewell).

Regional ground water equipotentials on March 22, 2002.

Back Cover photos:

Composite topographic and aerial photograph of a portion of the heavily urbanized Minebank Run wtershed showing locations of piezometers (red dots) and 

the I-695 Beltway in the lower left (courtesy of Robert Shedlock).

Incision and infrastructure exposure at Minebank Run before restoration.

Location of monitoring well transects in relation to restoration design 

(Figure courtesy of Maryland Department of Environmental Protection and 

Resource Management).
iii

Foreword

The U.S. Environmental Protection Agency is charged by Congress with protecting the Nation’s land, air, and water 

resources. Under a mandate of national environmental laws, the Agency strives to formulate and implement actions 

leading to a compatible balance between human activities and the ability of natural systems to support and nurture 

life. To meet this mandate, EPA’s research program is providing data and technical support for solving environmental 

problems today and building a science knowledge base necessary to manage our ecological resources wisely, 

understand how pollutants affect our health, and prevent or reduce environmental risks in the future.

The National Risk Management Research Laboratory is the Agency’s center for investigation of technological 

and management approaches for preventing and reducing risks from pollution that threatens human health and the 

environment. The focus of the Laboratory’s research program is on methods and their cost-effectiveness for prevention 

and control of pollution to air, land, water, and subsurface resources; protection of water quality in public water 

systems; remediation of contaminated sites, sediments and ground water; prevention and control of indoor air pollution; 

and restoration of ecosystems. NRMRL collaborates with both public and private sector partners to foster technologies 

that reduce the cost of compliance and to anticipate emerging problems. NRMRL’s research provides solutions 

to environmental problems by: developing and promoting technologies that protect and improve the environment; 

advancing scientific and engineering information to support regulatory and policy decisions; and providing the technical 

support and information transfer to ensure implementation of environmental regulations and strategies at the national, 

state, and community levels.

This publication has been produced as part of the Laboratory’s strategic long-term research plan. It is published and 

made available by EPA’s Office of Research and Development to assist the user community and to link researchers with 

their clients. This report describes a case study of the influence of stream channel geomorphology on surface water 

and ground water hydrology. The objective of the study was to characterize ground water-surface water interaction 

(GSI) in Minebank Run (MBR), a degraded urban stream in Baltimore County, Maryland that was slated for restoration. 

This study represents the first phase in quantifying the effects of stream restoration on GSI at MBR and is intended to 

provide the basis for comparison of post-restoration GSI at MBR. 

Stream restoration at MBR will utilize stream channel reconstruction methods designed to stabilize banks and reduce 

erosion, an approach intended to protect property and sewer and drinking water infrastructure. A clear understanding 

of GSI behavior under degraded conditions is necessary to quantify the effects of geomorphic methods of restoration 

on GSI. In turn, GSI is known to influence stream function such as nutrient uptake, stream metabolism, and primary 

production. Thus, the value of these baseline data extends to predicting the influence of geomorphic structure on GSI 

behavior and on subsequent biogeochemical and biotic response. 

Robert W. Puls, Acting Director

Ground Water and Ecosystems Restoration Division

National Risk Management Research Laboratory

v

Contents

Notice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix

1.0 Introduction ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.0 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3.0 Site Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4.0 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Study design and site characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Ground water-surface water interaction analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5.0 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Stream geomorphology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Stream geological setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Regional surface water and ground water hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Characterization of near-stream ground water-surface water interaction . . . . . . . . . . . . . . . . . . 21

Temperature verification of ground water-surface water interaction . . . . . . . . . . . . . . . . . . . . . 31

Stream flow verification of ground water-surface water interaction . . . . . . . . . . . . . . . . . . . . . . 32

Storm surge ground water-surface water interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

6.0 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

7.0 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

8.0 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
vi

Figures

1. Scales of ground water surface water interaction (image adapted from 

Stream Corridor Restoration Handbook; FISWRG, 1998). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2. Minebank Run watershed geographic location (adapted from “Watershed Characteristics 

and Pre-Restoration Surface-Water Hydrology of Minebank Run, Baltimore County, Maryland, 

Water Years 2002–04,” Doheny et al., 2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3. Minebank Run Watershed (adapted from “Watershed Characteristics and Pre-Restoration 

Surface-Water Hydrology of Minebank Run, Baltimore County, Maryland, Water Years 

2002–04,” Doheny et al., 2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4. Incision and infrastructure exposure at Minebank Run before restoration. . . . . . . . . . . . . . . . . . . . 6

5. Location of the Minebank Run Study Reach in Cromwell Valley Park (adapted from“Watershed 

Characteristics and Pre-Restoration Surface-Water Hydrology of Minebank Run, Baltimore 

County, Maryland, Water Years 2002–04,” Doheny et al., 2006). . . . . . . . . . . . . . . . . . . . . . . . . . . 7

6. Location of monitoring well transects in relation to restoration design (Figure courtesy of 

Maryland Department of Environmental Protection and Resource Management). . . . . . . . . . . . . . 8

7. Transect monitoring well network design. Distances not to scale (image adapted from Stream 

Corridor Restoration Handbook FISWRG, 1998). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

8. Stainless steel piezometer used in piezometer nests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

9. Location of monitoring wells and piezometer nests Minebank Run Study reach. . . . . . . . . . . . . . . 9

10. Example vertical equipotential stream cross section with left bank and right bank 

compartments on either side of the stream thalweg divide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

11. Transect 1 at beginning of study in Fall 2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

12. Transect 2 at beginning of study in Fall 2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

13. Transect 3 at beginning of study in Fall 2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

14. Ground surface elevation cross sections at Transects 1, 2, and 3 at beginning of study. . . . . . . . . . 14

15. Geological cross section lines for Minebank Run study site. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

16. Minebank Run Thalweg Cross Section A-A’. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

17. Transect 3 Cross Section B-B’. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

18. Transect 2 Cross Section C-C’. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

19. Transect 1 Cross Section D-D’. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

20. Regional ground water equipotentials on March 22, 2002. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

21. Regional ground water equipotentials on August 22, 2002. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

22. Regional ground water equipotentials on September 23, 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

23. Transect 1 vertical cross section equipotentials on March 22, 2002. . . . . . . . . . . . . . . . . . . . . . . . . 22

24. Transect 1 vertical cross section equipotentials on June 24, 2002. . . . . . . . . . . . . . . . . . . . . . . . . . 22

25. Transect 1 vertical cross section equipotentials on August 22, 2002 (study low) ............... 23

26. Transect 1 vertical cross section equipotentials on September 30, 2002. . . . . . . . . . . . . . . . . . . . . 23
vii

27. Transect 1 vertical cross section equipotentials on December 17, 2002. . . . . . . . . . . . . . . . . . . . . . 23

28. Transect 1 vertical cross section equipotentials on September 23, 2003 (study high). . . . . . . . . . . 24

29. Transect 2 vertical cross section of equipotentials on March 22, 2002. . . . . . . . . . . . . . . . . . . . . . 24

30. Transect 2 vertical cross section of equipotentials on June 24, 2002. ........................ 25

31. Transect 2 vertical cross section of equipotentials on August 22, 2002 (study low). . . . . . . . . . . . 25

32. Transect 2 vertical cross section of equipotentials on September 30, 2002. . . . . . . . . . . . . . . . . . . 25

33. Transect 2 vertical cross section of equipotentials on December 17, 2002. . . . . . . . . . . . . . . . . . . 26

34. Transect 2 vertical cross section of equipotentials on September 23, 2003 (study high). . . . . . . . . 26

35. Transect 3 vertical cross section of equipotentials on March 22, 2002. . . . . . . . . . . . . . . . . . . . . . 27

36. Transect 3 vertical cross section of equipotentials on June 24, 2002 . . . . . . . . . . . . . . . . . . . . . . . . 27

37. Transect 3 vertical cross section of equipotentials on August 22, 2002 (study low). . . . . . . . . . . . 27

38. Transect 3 vertical cross section of equipotentials on September 30, 2002. . . . . . . . . . . . . . . . . . . 28

39. Transect 3 vertical cross section of equipotentials on December 17, 2002. . . . . . . . . . . . . . . . . . . 28

40. Transect 3 vertical cross section of equipotentials on September 23, 2003 (study high). . . . . . . . . 28

41. Transect 1 continuous stream bed piezometer temperatures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

42. Transect 2 continuous stream bed piezometer temperatures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

43. Transect 3 continuous stream bed piezometer temperatures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

44. Steam discharge hydrograph in response to storm event on August 3, 2002. . . . . . . . . . . . . . . . . . 33

45. Transect 1 piezometer hydrograph response to storm event on August 3, 2002. . . . . . . . . . . . . . . . 33

46. Transect 2 piezometer hydrograph response to storm event on August 3, 2002. . . . . . . . . . . . . . . . 33

47. Transect 3 piezometer hydrograph response to storm event on August 3, 2002. . . . . . . . . . . . . . . . 34

48. GSI flow rates at Transect 1 during storm surge on August 3, 2002. . . . . . . . . . . . . . . . . . . . . . . . . 34

49. Transect 1 piezometer temperature response to storm event on August 3, 2002. . . . . . . . . . . . . . . 34

50. Transect 2 piezometer temperature response to storm event on August 3, 2002. . . . . . . . . . . . . . . 35

51. Transect 3 piezometer temperature response to storm event on August 3, 2002. . . . . . . . . . . . . . . 35

Tables

Table 1. Transect 1 Piezometer Conductivity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Table 2. Transect 2 Piezometer Conductivity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Table 3. Transect 3 Piezometer Conductivity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Table 4. Comparison of ground water levels on dates of March 22, 2002, August 22, 2002 and

September 23, 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Table 5. Ground water (GW) and surface water (SW) flow calculations for Transect 1. . . . . . . . . . . . 29

Table 6. Ground water (GW) and surface water (SW) flow calculations for Transect 2. . . . . . . . . . . . 30

Table 7. Ground water (GW) and surface water (SW) flow calculations for Transect 3. . . . . . . . . . . . 30

Table 8. Stream flow at each of the transects on specific dates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
viii

Acknowledgments

We offer our sincere gratitude to the USGS researchers, Ed Doheny, Roger Starsonick, and Bob Shedlock for their 

tremendous work in collecting surface and ground water hydrology data and preparing the pre-restoration surface water 

hydrology analysis. We thank Baltimore County Department of Environmental Protection and Resource Management, 

especially Don Outen, Steve Stewart, Karen Ogle, and Candy Crowell for their assistance in site selection and 

continuing project support. We also thank Brad Scroggins, Ken Jewell, Steve Acree, Randall Ross, and Russell Neill 

for invaluable field and technical assistance. Finally, we thank the Cromwell Valley Park personnel, especially Leo 

Rebetsky, for supporting the project and providing unfettered access to the stream site at all times. 
ix

Abstract

In Fall 2001, EPA undertook an intensive collaborative research effort with the US Geological Survey (USGS) and 

the Cary Institute of Ecosystem Studies to evaluate the impact of restoration on water quality at a degraded stream in 

an urban watershed using a before/after stream restoration study design. One objective was to evaluate if particular 

stream restoration techniques improve ground water-surface water interaction (GSI) and if beneficial hydrologic 

exchanges between the stream and riparian/floodplain may be enhanced to improve water quality. An essential piece 

of this comprehensive study was to characterize, measure, and quantify near-stream (GSI) before and after stream 

restoration at specific stream features and assess how the geomorphology and geology at each feature impact GSI. 

This research report describes the pre-restoration study of GSI at specific stream features in a degraded urban stream 

in Towson, MD. The study employed a comprehensive evaluation of the surface water hydrology, ground water 

hydrology, geomorphology, and geology along a specific stream reach slated for restoration. Ground water level 

measurements in piezometer nests in the stream bed and banks over time were found to be sufficient to characterize 

the losing or gaining nature of near-stream GSI. Temperature measurements were used to verify these interactions. 

The GSI was simply and effectively quantified using gradients calculated from the piezometer nest ground water 

levels and Darcy’s law in a simple compartment model. Flow was quantified and used to calculate residence times in 

the sediments. These residence times may be used to quantify the mass removal of nutrients and other contaminants 

if reaction kinetics are known. Results of the pre-restoration study reveal the highly variable nature of GSI on the 

temporal and spatial scales of interest. Results also reveal how specific stream features and settings influence GSI. 

Flow and residence time were found to be closely dependent on the stream feature geology and geomorphology. 

Consequently, any restoration that impacts these features likely will strongly influence GSI. Results of this study 

established the pre-restoration GSI. An identical study of the post-restoration GSI is underway. These results will be 

compared to the pre-restoration state in a second report to evaluate the impact of stream restoration on GSI to determine 

if improvements in water quality may be achieved.

Keywords: Baltimore, Maryland; geomorphology; ground water; ground water-surface water interaction; GSI; 

hydrology; hyporheic; Minebank Run; restoration; temperature; urban stream 

1

1.0

Introduction

Stream restoration is comprised of a group of techniques 

that are intended to improve the physical, chemical and 

ecological functions of a degraded stream (Falk et al. 

2006). Physical functions include the stream’s ability to 

manage its flow and sediment load. Chemical functions 

include the stream’s assimilative capacity to process 

nutrients and other contamination to maintain stream 

water quality. Ecological functions include providing 

aquatic and riparian habitats. All of these beneficial 

stream functions are intimately tied to the stream flow 

and the exchange of water in and out of the stream 

bed and banks known as ground water-surface water 

interaction (GSI).

GSI in streams is broadly defined as the exchange of 

ground water and surface water of a stream at several 

temporal or spatial scales. Watershed scale GSI is on the 

order of miles and involves ground water discharge over 

an entire watershed which supplies the stream base flow. 

Near-stream scale GSI, on the order of feet and days, 

captures the losing/gaining reaches of streams where 

transport and processing of nutrients that support aquatic 

and riparian habitats occurs. Sediment scale GSI refers 

to exchanges in the stream beds and banks that occur on 

the scale of inches and minutes. GSI in the near-stream 

and sediment scale is often called hyporheic flow and is 

critical for support of aquatic life.

 One goal of stream restoration has been to improve 

GSI in the belief that enhanced exchange will improve 

the physical, chemical, and ecological functions of a 

stream. A critical key to unlock the impact of restoration 

on stream function is the ability to quantify GSI flow 

in and out of the stream and evaluate how restoration 

impacts this flow. In the case of water quality, GSI flow, 

magnitude, and direction may be used to calculate mass 

removal of nutrients and contaminants in the stream bed 

and banks using the measured reaction kinetics before 

and after restoration. Efforts to understand the physical 

factors which influence GSI and to develop practical 

methods to quantify it, however, have been hindered 

by the inherent complexity of the multiple temporal 

and spatial scales of the interaction. The challenges of 

evaluating near-stream GSI at various stream features, in 

particular, remain an impediment to assessing whether or 

not particular stream restoration actions have improved 

GSI and stream function. 

In 2001, EPA/ORD/GWERD undertook an intensive 

collaborative effort with the US Geological Survey 

(USGS), Cary Institute of Ecosystem Studies and 

Baltimore County Department of Environmental 

Protection and Resource Management (DEPRM) to 

evaluate the impact of restoration on a degraded stream 

in an urban watershed using a before/after stream 

restoration study design. The main objective was to 

assess if stream restoration would improve the water 

quality of a degraded stream by improving its physical, 

chemical, and ecological functions. An essential piece 

of this comprehensive study was to evaluate the effects 

of particular stream restoration techniques on GSI. The 

hypothesis was that a degraded stream has poor GSI and 

if restoration could enhance GSI, water quality could 

be improved through beneficial hydrologic interactions 

between the stream and riparian/floodplain. 

To assess the impact of restoration on GSI, it was 

essential to characterize, measure, and quantify nearstream GSI at specific stream features. Our study, 

therefore, had two phases, one before and one after 

restoration. The objectives of the pre-restoration study 

which took place from Fall 2001 to Summer of 2004 

were to: 

1. Evaluate the stream geomorphology and geology 

at specific stream features and assess how stream 

geomorphology and geology at specific stream 

features influences GSI.

2. Develop effective and simple methods to 

characterize, measure, quantify and verify GSI at 

specific stream features to establish baseline GSI in 

the unrestored stream for comparison to the restored 

state. 

The objectives of the post-restoration phase, currently 

underway, are to employ methods developed during 

pre-restoration phase to evaluate water quality benefits 

of specific stream restoration techniques due to effects 

on GSI. 

This research report describes the results of the prerestoration assessment of GSI at specific stream features 

and methods to effectively and simply quantify it. The 

second research phase will describe the post-restoration 

GSI in relation to the pre-restoration state and quantify 

the mass removal of nutrients and contaminants 

which can be attributed to restoration impact on GSI. 

This comparison is intended to assess the impact of 

restoration on GSI and water quality due to specific 

stream restoration techniques. The results should 

provide restoration designers and stakeholders practical 

methods to measure GSI to determine mass removal 

of nutrients and contaminants in stream sediments and 

identify specific restoration techniques which improve 

GSI to enhance water quality and other beneficial stream 

functions.

3

2.0

Background 

Numerous hydrologic, chemical, and ecological benefits 

to streams and riparian areas have been associated 

with near-stream GSI (Boulton et al., 1998; Cirmo 

and McDonnell, 1997; Hayashi and Rosenberry, 2002; 

Kasahara and Hill, 2006; Poole et al., 2006). Often a 

claim is made that stream restoration can enhance GSI 

and benefit stream function. For example, restoring 

incised streams in order to reconnect stream channels to 

floodplains, may improve near-stream GSI. Interaction 

may also be improved by incorporating permeable 

sediments in stream beds and banks in place of low 

conductivity strata. These changes may increase the 

transport of nutrient laden water into the organic rich 

soil profiles in the floodplain and riparian zones. These 

nutrients may be utilized by riparian plants or denitrified 

by microbial activity, thereby improving water quality 

by reducing excess nitrogen and other nutrients. There 

is also the potential for removal of contaminants through 

adsorption in the stream sediments. In addition, 

restoring stream channels may enhance a stream’s ability 

to manage its flow and sediment load, reducing sediment 

transport. In this way, restoration which improves GSI is 

predicted to also improve water quality.

To date, few studies have assessed the effects of 

restoration on GSI (Kasahara and Hill, 2006). If an 

objective of stream restoration is to improve GSI, it 

is critical to characterize, measure, and quantify this 

exchange in the near-stream environment. However, 

GSI is notoriously difficult to evaluate because 

interactions are hidden and occur at spatially and 

temporally variable scales (Winter et al. 1998). In 

addition, the literature has employed inconsistent 

terminology to describe GSI.

Examples of GSI are demonstrated in Figure 1, which 

represents a general depiction of the sources of water 

to a stream in a watershed. Precipitation falling to the 

earth may become surface runoff to the stream or enter 

the subsurface ground water system. GSI includes the 

ground water and shallow subsurface flow that moves 

down gradient and discharges to the stream. GSI also 

encompasses stream water exiting and re-entering 

stream beds and banks through near-stream paths. The 

scales of these interactions are spatially and temporally 

variable and restoration will have a different impact on 

each.

To simplify the scale issue, this study employed a 

definition developed by Boulton et al. (1998) who 

separated GSI into three main scale categories; 

watershed, near-stream, and sediment scale GSI. 

Boulton et al. described watershed scale GSI as the 

regional perennial ground water flow to the stream 

shown in Figure 1. Watershed GSI occurs on the scale of 

miles and years and is typically defined as the base flow 

of a stream which is measured by stream gaging. At this 

scale, the ground water is assumed to discharge evenly 

to the stream with no variation along its length. As 

this discharge is a function of the watershed hydrologic 

setting, including ground water storage characteristics 

and climate, watershed GSI is typically not targeted and 

is unlikely to be modified in any significant fashion by 

stream restoration.

Near-stream GSI occurs on the scale of feet and days, 

as stream and ground water flows into and out of stream 

beds and banks (Figure 1). Near-stream GSI captures 

the spatial variability of the interaction along the length 

of a stream where reaches may be losing or gaining. In 

a losing reach, water moves from the stream into the bed 

and banks to ground water. In a gaining reach, ground 

water moves into the stream, thereby providing a portion 

of its flow. Stream restoration is highly likely to affect 

near-stream GSI, especially if it impacts the stream 

channel features, including stream depth, width, and bed 

and bank materials.

Sediment-scale GSI involves the small exchanges on the 

order of inches and minutes within the stream bed and 

banks. This interaction is a function of various factors 

including small changes in stream flow and stream bed 

structure (Castro and Hornberger, 1991; Savant et al., 

1987). Stream restoration may greatly impact sedimentscale GSI but designing stream restorations to target 

these specific interactions may not be practical as they 

are difficult to maintain. Near-stream and sediment 

scale GSI are often referred to as hyporheic exchange, 

a lumped term that we will avoid using to prevent 

confusion.

For this study, near-stream GSI was of special interest 

because the exchange of surface and ground water in 

the stream bed and banks may be significantly impacted 

by stream restoration. Current methods available to 

characterize and measure near-stream GSI include 

stream and ground water level measurements, flow and 

temperature surveys, seepage measurements, numerical 

flow and heat modeling, and stream and subsurface 

tracer studies (Harvey and Wagner, 2000; Kalbus et al., 

2006). These approaches have been used alone or in 

combination to measure and quantify GSI. 
4

Figure 1. Scales of ground water surface water interaction (image adapted from Stream Corridor Restoration Handbook; FISWRG, 1998).

One set of techniques to quantify GSI employs ground 

water levels and stream flow measurements, usually 

coupled with ground water/stream tracer studies and 

analytical/numerical flow modeling. Bencala et al. 

(1984) and Bencala (1984) performed comprehensive 

tracer studies of streams to interpret the dynamic 

physical and chemical properties that control tracer 

transport in the stream and hyporheic zone. Harvey 

and Bencala (1993) were able to simulate and assess 

the impact of stream features on hyporheic GSI by 

measuring near-stream ground water levels and tracer 

studies. Wroblicky et al. (1998) also used water levels 

and tracer studies in transient numerical flow simulations 

to quantify the spatial and seasonal variation in reach 

scale GSI. Harvey et al. (1996) evaluated the reliability 

of tracer studies by testing their sensitivity to stream 

flow conditions. Choi and Harvey (2000) identified the 

need to address several storage zones in the stream to 

account for tracer behavior. Harvey and Wagner (2000) 

and Kalbus et al. (2006) described and summarized 

methods to quantify near-stream GSI. 

Another set of techniques to quantify GSI uses stream 

and ground water temperature monitoring and heat 

modeling. Silliman and Booth (1993) and Constantz 

(1998) provided some of the first examples of the use of 

temperature measurements to identify losing and gaining 

portions of streams. Silliman et al. (1995) also provided 

mathematical formulations to quantify flux across the 

streambed for one-dimensional flow using measured 

temperatures. Conant (2004) used ground water levels 

and mapped streambed temperature to quantify stream 

bed GSI. Becker et al. (2004) quantified ground water 

discharge using stream flow measurements, stream 

temperature surveys and heat transport modeling of 

temperature gradients below the stream bed. Stonestrom 

and Constantz (2004) and Stonestrom and Constantz 

(2003) provide excellent descriptions of temperature 

measurement and modeling methods to quantify GSI. 

Once GSI is measured and quantified, it may be 

possible to evaluate the factors that influence it and 

those that may be modified through stream restoration. 

Many studies have established the influence of stream 

geomorphology and geology on GSI along a stream 

reach (Savant et al., 1987; Castro and Hornberger, 

1991; Eshelman et al., 1994; Fryar et al., 2000; Harvey 

and Bencala, 1993; Poole et al., 2006; Gooseff et al., 

2006). For example, streams in high conductivity 

alluvial settings composed of cobbles and sands offer 

less resistance and therefore greater potential for GSI. 

Streams flowing through heavy clays would be expected 

to have less interaction. Highly incised streams in 

consolidated bed rock would likely experience less GSI 

than stream meandering through sandy point bars. Deep 

pools with low velocities will likely interact differently 

with the ground water system than swift flowing 

reaches. In addition, geomorphology and geology 

will affect the residence time in the stream sediments, 

thereby influencing biological interactions in the near 

stream environment. Longer residence times may allow 

sustained microbial activity such as denitrification. It 

is therefore, of interest to determine how geologic and 

geomorphologic characteristics of the stream influence 

hydrology and residence time. 
5

3.0

Site Description

The stream selected for this study was Minebank 

Run (MBR), a second order stream located in a small 

watershed in the Piedmont physiographic region of 

Maryland in the south central section of Baltimore 

County (Figure 2). The headwaters of MBR are on 

the east side of Towson, MD and its outlet confluences 

with lower Gunpowder Falls, a major tributary of the 

Chesapeake Bay. 

The choice of MBR was made after several 

reconnaissance trips with Baltimore Department of 

Environmental Protection and Resource Management 

(DEPRM) personnel to streams slated for restoration 

in Baltimore County. MBR had already undergone 

successful restoration of its headwaters in 1999 and its 

lower reaches were scheduled to be restored in 2004 

and 2005. The unrestored reach possessed several 

characteristics that made it ideal for the before/after 

study, including a heavily degraded stream condition, 

a comprehensive geomorphic and riparian restoration 

design with significant manipulation of the stream 

channel and banks along the entire length of stream, a 

USGS stream gaging station, and convenient site access. 

The MBR watershed covers 3.24 square miles and the 

stream itself is three miles in length (Figure 3). Stream 

channel slopes are <1 percent in most locations (Doheny 

et al., 2006). Relief varies from 100 to 300 ft in the 

watershed. There is about a 340 ft drop in elevation from 

the headwaters of MBR to its outlet at Gunpowder Falls. 

The watershed geology is composed of a complex series 

of crystalline rocks including the Setters formation, 

the Cockeysville Marble and the Loch Raven Schist 

(Doheny et al., 2006). Underlying this group is the 

Baltimore Gneiss. Maps of surface geology show that 

the crystalline rocks are overlain by alluvial deposits 

composed of cobbles, gravels, and sands (Crowley et 

al., 1976). Some clay deposits were noted in the upper 

reaches of the watershed. The stream flows through 

exposed crystalline rocks in the upper reaches and 

unconsolidated deposits of colluvium and alluvium in 

lower reaches.

MBR is a classic example of stream that has undergone 

massive changes as a consequence of urban development 

in the watershed. When settled, the watershed was 

historically agricultural, but is now about 80% urbanized 

Figure 2. Minebank Run watershed geographic location (adapted from “Watershed Characteristics and Pre-Restoration 

Surface-Water Hydrology of Minebank Run, Baltimore County, Maryland, Water Years 2002–04,” Doheny et al., 2006).
6

Figure 3. Minebank Run Watershed (adapted from “Watershed Characteristics and Pre-Restoration Surface-Water 

Hydrology of Minebank Run, Baltimore County, Maryland, Water Years 2002–04,” Doheny et al., 2006).

with over 25% impervious surfaces (Doheny et al, 

2006). The stream has several runoff outfalls along 

its length including one from the I-95 corridor. The 

combination of fairly large stream slopes, significant 

relief and runoff from impervious surfaces causes 

the stream to experience pronounced flashy behavior 

during storm events (Doheny et al, 2006). MBR has 

experienced many of the geomorphic changes expected 

with flashy urban flows and is deeply incised with 

little to no riparian buffer. This incision has exposed 

infrastructure such as sewer lines and caused extensive 

bank failure, threatening personal property (Figure 4). 

In addition, this incision contributes to heavy sediment 

loads and diminished ecological condition. 

As a consequence of its poor condition and threats to 

property and infrastructure, Minebank Run was one 

of the streams targeted by DEPRM for restoration. A 

detailed restoration study was made of the stream and 

comprehensive restoration designs for the entire stream 

were prepared. In 1999, about 1.5 miles of MBR 

from the headwaters downstream were restored. The 

remainder of the stream was scheduled to be restored 

in 2004. The headwater restoration included Natural 

Stream Channel Design (NSCD) techniques such as 

bank armoring with rip-rap, step pools, and meanders 

(Rosgen, 1996). Riparian restoration included geotextile 

bank stabilization and substantial riparian revegetation. 

Although these efforts were intended solely to achieve 

geomorphic stability to protect infrastructure and 

property, we speculated that restoration may influence 

GSI and water quality of MBR.

Figure 4. Incision and infrastructure exposure at Minebank Run before restoration.
7

Study design and site characterization

In the summer of 2001, a short section of the unrestored 

reach of MBR in Cromwell Valley Park, Towson, MD 

was selected for intensive study (Figure 5). A 

continuous stream gauge, 01583980 Minebank Run 

at Loch Raven, MD, had already been installed in 

the park by the USGS at MBR in 2000 (Figure 5). A 

new continuous stream gage, 0158397967 Minebank 

Run near Glen Arm, MD, was installed upstream of 

the study reach (Figure 5). A continuous rain gage, 

392449076331100 Minebank Run Rain Gage, was also 

installed to provide a real time precipitation record 

(Figure 5). 

In the Fall 2001, the locations of the three transects 

were chosen for intensive study of the stream before 

restoration (Figure 5). These locations were selected 

based on the unrestored condition of the reach and the 

restoration plans (Figure 6). The intent was to position 

transects in locations where degraded stream features 

would undergo a specific restoration technique. The 

study was designed to measure baseline conditions 

in the degraded stream condition and then measure 

the response to the restoration. To that end, the 

geomorphology of Minebank Run was evaluated by the 

USGS and published in a recent report (Doheny et al., 

2007). 

Transect 1, was located at a deeply incised pool where 

a new stream channel was to be created (Figure 5). 

Transect 2, was positioned 237 ft upstream of Transect 

1 and placed across an incised narrow riffle and point 

bar which was to be armored and raised (Figure 5). 

Transect 3, was positioned 148 ft upstream of Transect 2 

and located in a flat shallow terrace section which was 

to undergo little modification (Figure 5). An ancillary, 

3-piezometer nest was placed in the stream channel 

approximately 100 ft downstream of Transect 1 was 

occasionally sampled for hydrology.

4.0

Methods

Figure 5. Location of the Minebank Run Study Reach in Cromwell Valley Park (adapted from“Watershed Characteristics and Pre-Restoration Surface-Water Hydrology of Minebank Run, Baltimore County, Maryland, Water Years 

2002–04,” Doheny et al., 2006).
8

Figure 6. Location of monitoring well transects in relation to restoration design (Figure courtesy of Maryland Department of Environmental Protection and Resource Management).

In November 2001, an EPA field team installed the 

monitoring wells and piezometers at each transect at 

the site. The transect monitoring design (Figure 7) 

was composed of paired two-inch diameter monitoring 

wells in the floodplain and nests of three piezometers 

in the stream bed and banks. This design was intended 

to capture the spatial and temporal scales of nearstream GSI and the larger regional ground water flow 

system. For each transect, nests of three piezometers 

were installed in the stream bed and banks using a 

SimcoTM direct push rig. The piezometers were one-inch 

diameter stainless steel with six inch long wire-wound 

screens with 0.01 inch mesh (Figure 8). Piezometer 

nests installed in the stream bed were driven to depths 

of approximately two, four, and six feet below ground 

surface in the thalweg. Next, piezometer nests were 

installed on each banks close to the stream edge. Bank 

piezometers were driven to depth to match the same 

mean sea level elevations of the piezometers in the 

stream. Throughout this report, the piezometers in the 

stream bed and banks will be identified as shallow, 

medium, and deep.

In addition to the piezometer nests, two-inch PVC cased 

monitoring wells with five-foot screens were installed 

in the floodplain near the stream. Pairs of wells were 

placed approximately fifty feet perpendicularly from 

the stream thalweg. One well of each pair was installed 

just below the water table and the second well of each 

pair was installed to the point of bedrock refusal. Single 

monitoring wells were placed approximately one 

hundred feet from the stream thalweg. After installation, 

all piezometers and monitoring wells were developed to 

ensure proper ground water sampling. The piezometer 

and monitoring well locations and elevations were 

surveyed using standard line of sight methods. The 

aerial map shows the georeferenced locations of the 

monitoring wells and piezometer nests (Figure 9). 

As the monitoring wells were installed, 5 cm diameter 

(ID) continuous cores were collected to refusal using 

a GeoprobeTM direct drive system. The cores were 

characterized to describe the lithology. In July 2004, 

additional cores were collected at all of the stream bed 

and bank piezometer nests and characterized. Slug 

testing was done at all of the piezometers using falling 

and rising head tests to determine conductivity (Bouwer 

and Rice, 1976 and Bouwer, 1989). 

Water levels were measured at all of the wells and 

piezometers approximately every two weeks starting 

in January 2002. To capture the continuous time scale, 

many of the piezometer nests and some of the floodplain 

wells were fitted with SolinstTM Model 3001 data loggers 

in March 2002 to measure temperature and ground 

water elevation every five minutes. These data loggers 

were downloaded every three months. Ground water 

data were collected until the wells were removed for the 

restoration in July 2004. 
9

Shallow/deep

monitoring wells Piezometer well

nests

Shallow/deep

monitoring wells

Figure 7. Transect monitoring well network design. Distances not to scale (image adapted from Stream Corridor Restoration Handbook, FISWRG, 1998).

Figure 8. Stainless steel piezometer used in piezometer nests.

Figure 9. Location of monitoring wells and piezometer nests Minebank Run Study reach.

All of the site characterization and ground water level 

data were measured in English units of feet for increased 

resolution at the small scales involved in this study. 

All of the calculations were also done in units of feet 

to maintain consistency. Data and calculations were 

reviewed and stored in electronic form in databases or 

MS Excel spreadsheets according to the approved EPA 

Quality Assurance Project Plan. The USGS stream 

and rain gage data for MBR are available on line http://

waterdata.usgs.gov/nwis/. 

Ground water-surface water interaction analysis

One factor known to impact near-stream GSI is the 

geomorphological setting, the physical relationship 

between the stream and the ground surface. The stream 

geomorphological setting at each of the transects was 

evaluated using field observations, stream profiles, and 

stream velocity. The stream profile defines the cross 

sectional area at each transect which, in turn, determines 

the channel velocity for a given stream flow rate. The 

flow velocity through each transect was evaluated to 

determine if geomorphology created a stream hydrologic 

setting that influenced the GSI.
10

Another factor known to influence near-stream GSI is 

the geological setting. Geological setting is important 

because the lithology provides the stream bed location 

relative to the geologic layers. Geological setting also 

defines the conductivity of the sediments, a measure of 

the resistance to ground water-surface water exchange 

in the near steam sediments, with low conductivities 

limiting exchange and high conductivities enhancing 

exchange. If a stream is situated in highly conductive 

alluvial sediments such as sands and gravels, water 

will exchange easily in these zones. If fractures or 

other preferential flow features are present, GSI may be 

enhanced. If a stream is in silt, clays or incising into 

rock, near-stream GSI is limited by these non-conductive 

sediments. The geologic setting at MBR was defined 

using cores to develop lithologic cross sections and slug 

testing to assess hydraulic conductivity (Bouwer and 

Rice, 1976 and Bouwer, 1989). 

To describe the watershed scale GSI at MBR, the 

regional stream and ground water hydrology were 

assessed. The USGS evaluated the MBR site prerestoration stream hydrology data and published a 

comprehensive surface water hydrology report (Doheny, 

et al., 2006). The regional ground water flow system 

was defined using traditional horizontal ground water 

equipotential contours across the site developed from 

the biweekly ground water level data. These contours 

provided the ground water flow magnitude and direction 

across the site and gave some insight into the interaction 

of the regional ground water flow with the stream. 

The near-stream GSI on the scale of tens of feet was 

demonstrated at each of the transects using vertical 

equipotential contours from piezometer water levels 

measured biweekly (Figure 10). These contours allowed 

the potential gradients under each of the stream transects 

to be visualized and the flow directions inferred. 

Although numerous methods were available to quantify 

GSI, it was immediately apparent from the data that 

most were not suited to the situation at MBR. Ground 

water equipotentials evaluated both seasonally and for 

the ground water high and low during the study at each 

of the transects demonstrated a complex flow system 

that was spatially and temporally variable. Traditional 

tracer and modeling techniques (Harvey and Bencala 

1993) typically assume steady state conditions and 

were not suitable to capture the spatial and temporal 

variation observed in the near-stream GSI at Minebank 

Run. Tracer tests would need to be run each time the 

flow field varied to capture its unique signature. Flow 

and temperature modeling was also impractical as the 

models require many boundary and hydrologic condition 

assumptions and therefore, the true transient nature 

of the near-stream GSI would be nearly impossible to 

reproduce. 

An objective of the study was to develop a transparent 

and effective method to quantify the GSI before and after 

restoration. We decided to employ a simple hydrologic 

flow analysis which used measured water levels from the 

piezometer nests. The vertical and horizontal gradients 

were calculated from these measured values at each 

of the transects. These gradients were used in Darcy’s 

Figure 10. Example vertical equipotential stream cross section with left bank and right bank compartments on either 

side of the stream thalweg divide.
11

law to determine the flow at each of the transects over 

time by applying some simple assumptions. The first 

assumption was that the thalweg of the stream acts as a 

ground water divide at shallow depths near the stream 

bed such that flow on one side of the stream is not 

influenced by the flow on the other. In small headwater 

streams with partial penetration and perennial base flow 

such as MBR, this approach was strongly supported 

by near-stream piezometer temperature and ground 

water level measurements at the site. This allowed 

the flow system to be split into a left and a right bank 

compartment on either side of the stream thalweg divide 

as shown in Figure 10.

The second assumption was the ground water seepage, 

q, in each compartment can be represented by one 

constant linear vector. This vector was determined 

by calculating the vertical and horizontal gradients in 

each compartment separately based on the water levels 

measured in the stream bed and bank piezometers and 

applying Darcy’s law:

h h q k i k

x z

  ∂ ∂

= − +     ∂ ∂ (1)

where k was the hydraulic conductivity measured by 

slug tests at the site. The horizontal gradient, ∂h/∂x, was 

calculated for each bank using the difference between 

the piezometer water levels in the stream bank and 

stream beds. Concurrently, the vertical gradient, ∂h/∂z, 

was determined using the water levels in stream bed 

piezometers. A negative horizontal or vertical gradient 

was defined as flow in toward the stream. The resultant 

seepage vector through the compartment on either side 

of the stream center line was then defined by determining 

its magnitude, ∂h/∂s, , and its direction counterclockwise 

from horizontal, θ, using equations 2 and 3.

2 2

h h h

s x z

∂ ∂ ∂       = +      ∂ ∂ ∂      

 (2)

tan

h h

z x

  ∂ ∂ θ =     ∂ ∂ (3)

Once the magnitude of the seepage vector and its 

direction were known, it was possible to calculate 

the residence time, t, along a path line, s, through the 

compartment:

t s q n = ( ) / (4)

where n is the porosity which was calculated from core 

measured bulk densities at each transect. A volumetric 

flow for the compartment was also determined:

Q qA = (5)

where A is the unit cross sectional area perpendicular to 

the flow vector.

The GSI flow rates for each transect were calculated on 

several dates to demonstrate the spatial and temporal 

variation in the near-stream GSI at MBR. To verify the 

results, the GSI rates were compared to the measured 

stream flow rates to assess if they supported the losing 

and gaining nature of the stream along the reach. In 

addition, the continuous record of temperature obtained 

from the SolinstTM Model 3001 data loggers installed in 

the shallow and medium depth piezometers in the stream 

beds was evaluated to verify the losing or gaining nature 

of the GSI at each stream transect using the methods of 

Stonestrom and Constantz (2003). 

MBR experienced several storm surges during the 

study. The impact of these events was captured by 

the continuous data loggers which measured level 

and temperature every five minutes. The continuous 

temperature record during the storm surge in the 

piezometers was evaluated using the methods of 

Stonestrom and Constantz (2003) to help assess the 

residence time of the stream water as the surge drove 

water into the stream bed sediments. Water levels in 

the stream bed and bank piezometers were plotted to 

show how one particular storm surge event influenced 

GSI. Darcy’s law was applied as a first approximation 

to make an estimate of the storm surge flow rates into 

the stream bed which varied continuously over time. 

The application of Darcy’s law under these conditions 

was not rigorous. Typically one may use the gradients 

from these measurements and Darcy’s law to assess the 

seepage velocity into the stream bed as was done for the 

vertical equipotentials for the bi-weekly water level data. 

However in the case of a storm surge, the hydraulic 

gradient in the stream bed and banks is continuously 

changing as a function of time so flow is not steady. 

The flow is also moving at high velocity, which means 

it is turbulent, with Re>1. Therefore Darcy’s law is not 

truly applicable as it assumes steady laminar flow with a 

Reynolds number, Re<1. More research will be needed 

to develop the appropriate equations to truly evaluate 

this unsteady, turbulent flow system.

13

5.0

Results

Stream geomorphology

At MBR, transects were strategically placed so 

the unrestored stream physical features could be 

used to provide insights into the impact of stream 

geomorphology on stream flow behavior and the prerestoration GSI. Transect 1 was located at a deep pool 

with severe incision on the left bank (top half of picture) 

and a depositional point bar on the right bank (lower 

half of picture) (Figure 11). Transect 2 was located at 

a shallow, narrow riffle with an incised left bank and 

a point bar on the right bank (Figure 12). Transect 3 

was located at a shallow, wide terrace (Figure 13). The 

piezometer nests can be seen in the stream bed and 

banks (Figure 11). The stream bed piezometers were 

replaced flush with the stream after a storm event bent 

them (Figure 13).

Figure 11. Transect 1 at beginning of study in Fall 2001.

Figure 12. Transect 2 at beginning of study in Fall 2001.

Figure 13. Transect 3 at beginning of study in Fall 2001. 

The mean sea level ground surface elevation of the 

stream profiles at Transects 1, 2, and 3 at the beginning 

of the study is shown in Figure 14. At Transect 1, 

stream velocity at base flow was measured as 0.19 ft/sec. 

This low velocity was a consequence of incision at 

this transect which had created a deep, wide pool with 

large cross sectional area. This low velocity created a 

relatively static setting for interaction with the ground 

water in the stream bed and banks. At Transect 2, 

the stream flowed through a narrow shallow cross 

section with a measured base flow stream velocity 

of 0.66 ft/sec. This high velocity created a dynamic 

setting for interaction with the underlying ground 

water. At Transect 3, flow moved through a large flat 

cross sectional area defined by the stream terrace. The 

measured base flow stream velocity was 0.29 ft/sec and 

created a static environment for GSI.
14

Figure 14. Ground surface elevation cross sections at Transects 1, 2, and 3 at beginning of study.

Stream geological setting

At MBR, cores were collected and characterized to 

create several cross sections to define the geological 

setting (Figure 15). Cross section A-A’ was defined 

along the stream thalweg and shows the lithology 

described by the core holes near the deep stream 

bed piezometers, 146, 149 and 153 (Figure 16). The 

lithology directly under the stream was gravelly clay 

ranging from five to ten feet thick, underlain by a clay 

layer. A thick layer of poorly sorted sand was found 

under the clay. Sediment cores did not reach bed rock at 

these sites. 

Figure 15. Geological cross section lines for Minebank Run study site.
15

Figure 16. Minebank Run Thalweg Cross Section A-A’.

Cross section B-B’ was constructed based on cores 

extracted along Transect 3 (Figure 17). Piezometer 146 

was in the thalweg of the stream, 162 was in the left 

bank and 157 was in the right bank. The other cores 

were located at the floodplain monitoring wells. The 

lithology on the left side of the stream was a top layer of 

sandy clay underlain by a gravelly clay that varied from 

3-6 feet thick. On the right side of the stream, the top 

layer was silty clay underlain by gravelly clay near the 

stream bed and sandy clay farther away from the stream. 

The clay layer was only found on the right side of the 

stream and was a few feet thick. A continuous layer of 

poorly sorted sand was encountered under both sides 

of the stream. Limestone bedrock was encountered on 

both sides of the stream but not reached directly under 

the stream. 

Figure 17. Transect 3 Cross Section B-B’.
16

Cross section C-C’ was constructed from cores collected 

along Transect 2 (Figure 18). Piezometer 149 was in 

the thalweg of the stream, 167 was located in the left 

bank, and 171 was in the right bank. On the left side of 

the stream, the lithology was sandy clay underlain by 

the gravelly clay. On the right side of the stream, the 

top layer was part of a point bar composed of gravels 

and underlain by gravelly clay. The clay layer was only 

encountered under the right side of the stream. A thick 

continuous layer of poorly sorted sand was encountered 

under both sides of the stream. Limestone bedrock was 

encountered on the left side of the stream but was not 

reached directly under the stream or on the right side. 

Figure 18. Transect 2 Cross Section C-C’.

Cross section D-D’ was constructed from the cores collected along Transect 1 (Figure 19). Piezometer 153 was 

in the thalweg of the stream and piezometers 176 and 

179 were located in the left and right bank, respectively. 

Both sides of the stream exhibited a top layer of sandy 

clay underlain by the gravelly clay. The gravelly clay 

was about twice as thick on the right side of the stream 

as on the left. The clay layer was evident under the right 

bank of the stream but disappeared on the left bank. A 

thick continuous layer of poorly sorted sand was encountered under both sides of the stream. The limestone 

bedrock, located at shallow depths under the left side 

dipped steeply before flattening out under the stream and 

right hand side. 

Figure 19. Transect 1 Cross Section D-D’.
17

These cross sections demonstrate that the stream and 

floodplain were composed of thick sections of gravelly 

clay, clay, and sand underlain by limestone bedrock. The 

gravelly clay and sands were found on both sides of the 

stream and the clay was located on the right side in the 

floodplain. The limestone bedrock was encountered 

at depth and cores indicated it was weathered and 

fractured. However, as the limestone was so removed 

from the stream bed, that the possibility of preferential 

flow from the bedrock fractures to the stream was 

dismissed. 

Before this geological characterization, the MBR 

watershed was described as being composed of strictly 

heterogeneous alluvial deposits ranging from cobbles, 

gravels and sands which were underlain by limestone 

bedrock. A search was made to determine if a manmade 

dam was used in the watershed to account for the clay 

layers (Walter and Merritts 2008), but no historical 

evidence for such a structure could be located. However, 

historical records, including maps and photographs, 

were discovered of extensive iron mining operations 

active until the 1800s that stripped topsoil throughout the 

watershed (Dorothy Merritts, personal communication). 

This type of mining involved digging shallow pits along 

the watershed, excavating a shipping canal parallel to the 

current stream thalweg, and constructing limestone kilns 

along the stream channel. Slag from historic smelting 

operations can be seen in the stream channel today 

and some unusual sediment layers observed in incised 

banks of Minebank Run are probably derived from the 

intensive mining activity of this era (Dorothy Merritts, 

personal communication). Based on this information, 

the geological setting for Minebank Run has clearly been 

very disturbed. 

To complete the description of the geological setting 

and interpret its impact on GSI, conductivity, k, was 

measured using slug tests at each of the transect 

piezometers at MBR. The results are shown in Tables 

1, 2 and 3, respectively. The measured values were in 

general agreement with the geological characterizations 

of the cores in the stream bed and banks. At Transect 

1, the piezometers were screened in a heterogeneous 

gravelly clay and the conductivity ranged from 0.01 to 

310.0 ft/day. The low values in the deeper piezometers 

indicate they were in a clay layer whereas the medium 

depth stream bed and right bank piezometers were 

most likely screened in cobble layer, perhaps part of 

an abandoned channel not clearly identifiable from 

the cores. At Transect 2, the conductivities were also 

representative of a heterogeneous gravelly clay but had 

less of a range from 0.07- 9.2 ft/day. At Transect 3, 

the conductivities were consistent and higher because 

the piezometers were screened in the sand, with the 

exception of one deep piezometer in the clay. The range 

was 10.0-58.0 ft/day. 

Table 1. Transect 1 Piezometer Conductivity

Name Location Estimated K

(ft/day)

BAEe176 T1 LB deep 0.01

BAEe177 T1 LB medium 6.90

BAEe178 T1 LB shallow 3.70

BAEe153 T1 Stream deep 0.14

BAEe154 T1 Stream medium 310.00

BAEe155 T1 Stream shallow ND

BAEe179 T1 RB deep 0.89

BAEe180 T1 RB medium 170.00

BAEe181 T1 RB shallow 19.00

Table 2. Transect 2 Piezometer Conductivity

Name Location Estimated K

(ft/day)

BAEe167 T2 LB deep 8.00

BAEe168 T2 LB medium 9.20

BAEe169 T2 LB shallow 0.07

BAEe149 T2 Stream deep 2.70

BAEe150 T2 Stream medium 5.10

BAEe151 T2 Stream shallow ND

BAEe171 T2 RB deep 1.80

BAEe172 T2 RB medium 0.41

BAEe173 T2 RB shallow 2.30

Table 3. Transect 3 Piezometer Conductivity

Name Location Estimated K

(ft/day)

BAEe162 T3 LB deep 46.00

BAEe163 T3 LB medium 38.00

BAEe164 T3 LB shallow 49.00

BAEe146 T3 Stream deep 0.14

BAEe147 T3 Stream medium 14.00

BAEe148 T3 Stream shallow 47.00

BAEe157 T3 RB deep 58.00

BAEe158 T3 RB medium 10.00

BAEe159 T3 RB shallow 32.00

The conductivity of the sediments in the stream bed 

and banks have significant implications for GSI. The 

magnitude of ground water flow in the bed and banks, 

q, is directly proportional to the magnitude of the 

conductivity, k, and the hydraulic gradient, h, as defined 

in Darcy’s law for flow in saturated sediments, q=kh. 

For example, Transect 1 has high conductivities in the 

shallow- and medium-depth stream bed and in the right 

bank piezometers suggesting higher exchange of ground 

water and surface water in response to the hydraulic 

gradient created by the stream and regional ground water 

elevations. 

The left bank at Transect 1 had lower conductivity, 

suggesting lower exchange rates under similar stream 
18

flow rates. All of the deep piezometers at Transect 1 

had low conductivity, which suggested sediments at 

this depth would limit ground water and surface water 

exchange. Conductivity at Transect 2 was homogeneous 

throughout all locations and depths, suggesting 

homogeneous ground water exchange throughout all 

depths across the channel. Transect 3, situated in sands 

with conductivity an order of magnitude higher than 

the other transects, would be expected to have greater 

ground water-surface water exchange in response to 

changes in the stream or regional ground water levels.

Regional surface water and ground water hydrology

The regional surface water hydrology of Minebank Run 

was evaluated by the USGS and published in a recent 

report (Doheny et al., 2006). According to the report, 

the average annual precipitation for the Baltimore region 

is 42 inches. Water year 2002 was considered a drought 

with an annual precipitation of 32.95 inches. Water 

year 2003 was a wet year with a total precipitation of 

64.19 inches. In water year 2002, the low mean annual 

discharge for MBR at the Glen Arm, MD, stream gage 

just above Transect 3 was measured as 1.15 ft3

/sec. In 

water year 2003, the high mean annual discharge of 

4.34 ft3/sec was reported at this same gage.

Using these values, it was possible to estimate a range 

of the mean amount of ground water discharged to the 

stream on a regional scale each day during years 2002 

and 2003 of this study. Assuming that stream flow is 

entirely base flow, a mean discharge of 1.15 ft3/sec in 

2002 translates into about 99,360 ft3/day of ground 

water entering the stream above the gage. For 2003, 

the annual mean discharge of 4.34 ft3/sec translates into 

374,976 ft3/day of ground water entering the stream 

which represents a small portion of the ground water 

storage in the 2.1 square miles drained above the gage. 

At the watershed scale, assuming that this discharge 

is equally distributed along the length of the stream 

(ca. two miles for this gage), discharge ranges from 

0.0036 ft3/day/ft in 2002 to 0.0135 ft3/day/ft in 2003.

These data demonstrate that little of the total ground 

water enters the stream as base flow. Because MBR 

only partially penetrates the thick sediments under the 

thalweg as demonstrated in the geological cross sections, 

the stream intercepts little ground water. The majority 

of ground water moves slowly at depth down the valley 

under the stream with very little interaction with the 

stream because the ground water and surface water are 

not defined by the same boundary. 

This minimal interaction between the ground water and 

stream system revealed by the stream hydrology at the 

watershed scale can also be seen in the ground water 

hydrology at MBR. Figure 20 displays the horizontal 

equipotentials derived from the ground water level 

measurements for each of the transects at the beginning 

of the study on March 22, 2002 for a 400 x 400 ft 

region around the stream reach. These equipotentials 

show that ground water flow moves from roughly 

west to east across the study site. The gradient ranges 

from 2.0 - 4.0 ft/100 ft. With an estimated average 

hydraulic conductivity of 20 ft/day, this translates into 

a ground water seepage velocity of 0.4 - 0.8 ft/day. 

The equipotentials on March 22, 2002 are not clearly 

perturbed by the stream, which means that minimal 

ground water was moving into the stream. These 

data are corroborated by the stream gage flow of only 

0.87 ft3/sec on this date.
19

Figure 20. Regional ground water equipotentials on March 22, 2002.

In the summer of 2002, MBR experienced a severe 

drought. Figure 21 displays the equipotentials on 

August 22, 2002 for the ground water low created by 

the drought. The flow was still from west to east. The 

gaged stream flow for this date was 0.04 ft3/sec. During 

this time, the stream ceased to flow at Transects 1 and 

2 and stream water began entering the ground water 

system as recharge due to dropping ground water levels. 

As a consequence, equipotentials show the complete lack 

of interaction of the ground water with the stream.

Figure 21. Regional ground water equipotentials on August 22, 2002.
20

In 2003, the MBR watershed received high rainfall 

amounts. In response to this recharge, a ground 

water level high was recorded on September 23, 2003 

(Figure 22). The stream gage reflected this event with a 

recorded flow of 7.7 ft3/sec. The regional ground water 

equipotentials, which clearly show the influence of the 

stream, are strongly distorted by stream interaction at 

both Transect 1 and Transect 3. The stream was acting 

as the drain for the additional recharge.

Figure 22. Regional ground water equipotentials on September 23, 2003.

These equipotentials demonstrate the temporal 

variability of the ground water levels and stream flow. 

The ground water levels varied greatly over time at the 

site, with water levels at some of the monitoring wells 

differing by more than seven feet from the low to the 

high (Table 4). The equipotentials also capture the 

spatial variability in the ground water levels. The water 

level variation in specific wells increases with increasing 

distance from the stream; wells farthest from the stream 

showed the greatest variation in water level while wells 

close to the stream maintained a smaller range.
21

Table 4. Comparison of ground water levels on dates of March 22, 2002, August 22, 2002, and September 23, 2003

Name Location 3/22/2002

msl (ft)

8/22/2002

msl (ft)

9/23/2003

msl (ft)

High vs. Low

msl (ft)

BAEe182 T1 MW 100 ft Left bank NA NA 219.93 NA

BAEe183 T1 MW 50 ft Left bank 216.83 215.30 218.96 3.66

BAEe178 T1 Left bank shallow 215.06 NA 216.97 NA

BAEe155 T1 Stream shallow 215.42 NA NA NA

BAEe186 T1 Riffle shallow 214.49 212.12 214.38 2.26

BAEe181 T1 Right bank shallow 215.24 NA 215.23 NA

BAEe191 T1 MW 50 ft Right bank 214.35 210.87 217.13 6.26

BAEe192 T1 MW 100 ft Right bank 214.36 210.71 217.58 6.87

BAEe170 T2 MW 100 ft Left bank 217.78 216.30 219.72 3.42

BAEe175 T2 MW 50 ft Left bank 217.48 216.14 218.95 2.81

BAEe169 T2 Leftbank shallow 217.48 216.53 218.59 2.06

BAEe151 T2 Stream shallow 216.98 216.19 216.73 0.54

BAEe173 T2 Right bank shallow 217.43 216.24 217.97 1.73

BAEe195 T2 Point bar shallow 217.48 215.89 218.45 2.56

BAEe188 T2 MW 180 ft Right bank 216.25 213.78 221.23 7.45

BAEe161 T3 MW 110 ft Left bank 219.82 218.72 222.78 4.06

BAEe160 T3 MW 150 ft Left bank 220.50 219.37 222.96 3.59

BAEe 166 T3 MW 50 ft Left bank NA NA 220.57 NA

BAEe164 T3 Left bank shallow 219.45 218.49 220.03 1.54

BAEe148 T3 Stream shallow 219.51 218.66 219.83 1.17

BAEe159 T3 Right bank shallow 219.34 218.53 220.33 1.80

BAEe156 T3 MW 50 ft Right bank 219.05 217.56 221.42 3.86

BAEe145 T3 MW 100 ft Right bank 219.25 217.08 222.79 5.71

Characterization of Near-Stream Ground WaterSurface Water Interaction 

Once the geomorphology, geology, stream and ground 

water hydrology for MBR were described, the nearstream GSI was characterized. Vertical equipotential 

contours were created at each of the transects using 

measured piezometer-nest water levels for several dates 

to show the gradients under each of the stream transects 

at a scale in tens of feet. The equipotentials were drawn 

using an automatic contouring program for the dates 

of March 22, 2002, June 24, 2002, August 22, 2002, 

September 30, 2002, December 17, 2002 and September 

23, 2003. These dates were selected to show seasonal 

variation and capture the GSI on the ground water low 

observed on August 22, 2002 and the ground water high 

on September 23, 2003. The gaged stream flow on these 

dates was 0.87, 0.35, 0.04, 0.12, 1.7, and 7.7 ft3

/sec, 

respectively. For all vertical equipotential figures, the 

black, solid line represents the stream bed profile at 

the transects in Fall 2001. The blue line represents 

the ground water level surface based on the shallow 

piezometer measurements (e.g. Figure 23). Ground 

water level is drawn across the stream for reference, but 

it does not represent actual stream water level which is 

a function of other factors besides ground water level. 

Note that the automatic contouring can create artifacts 

from edge effects outside the data points which should 

be ignored. Flow is from high to low equipotential.

Transect 1 was a deep incised pool with a slow base 

flow velocity and high conductivity. These features 

would suggest it would experience good exchange 

with the ground water system. Figures 23 to 28 show 

vertical ground water equipotentials under Transect 1 

for select dates. The March 22, 2002 equipotentials 

indicate flow was moving from the stream into the bed 

and banks, demonstrating that the stream was losing 

water. The situation was the same for June 24, 2002 but 
22

the gradients were greater. These data suggest that water 

level in the pool was sufficient relative to the ground 

water to allow stream water to move continuously 

into the stream bed and banks. Near the height of the 

drought on August 22, 2002, the pool dried up and 

the water levels in the piezometers dropped below the 

shallow stream bed and bank piezometers. Flow then 

moved under the bed, down gradient, and parallel to the 

stream as part of the larger regional ground water flow 

system. Therefore, ground water was not interacting 

with surface water at this time. On September 30, 2002, 

ground water levels had risen above the stream and there 

was once more interaction between ground and surface 

water. Consequently, stream flow moved downward and 

outward to the left bank. During the ground water high 

on September 23, 2003, Transect 1 flowed from the left 

bank under the stream to the right bank. The stream bed 

shallow piezometer was lost in a storm and could not 

be used to create these contours. Although the ground 

water levels had risen, the stream depth in the pool 

was apparently sufficient to prevent ground water from 

discharging upward into the stream. Overall, Transect 1 

was a consistently losing reach.

Figure 23. Transect 1 vetical cross section equipotentials on March 22, 2002. 

Figure 24. Transect 1 vertical cross section equipotentials on June 24, 2002. 
23

Figure 25. Transect 1 vertical cross section equipotentials on August 22, 2002 (study low). 

Figure 26. Transect 1 vertical cross section equipotentials on September 30, 2002. 

Figure 27. Transect 1 vertical cross section equipotentials on December 17, 2002. 
24

Figure 28. Transect 1 vertical cross section equipotentials on September 23, 2003 (study high). 

Transect 2 was a shallow narrow riffle with a steep 

incised left bank and a point bar on the right bank with a 

high base flow velocity. Piezometers in Transect 2 were 

situated in low conductivity sediments with slow hydrologic exchange. Figures 29-34 show the ground water 

equipotentials under Transect 2 for select dates. Ground 

water flow was consistently from the stream banks into 

the bed, indicating that Transect 2 was a gaining reach. 

The vertical gradient ranged from a low of 0.02 ft/ft during the drought to a high of 0.1 ft/ft on Sept. 23, 2003. 

Stream width was narrow and surface flow was swift so 

the area for GSI was small. This geomorphology was 

likely the cause of a focused upwelling of ground water 

discharge at this point. Rapid flow at this reach may also 

have allowed for more discharge to the stream. 

Figure 29. Transect 2 vertical cross section of equipotentials on March 22, 2002. 
25

Figure 30. Transect 2 vertical cross section of equipotentials on June 24, 2002. 

Figure 31. Transect 2 vertical cross section of equipotentials on August 22, 2002 (study low). 

Figure 32. Transect 2 vertical cross section of equipotentials on September 30, 2002. 
26

Figure 33. Transect 2 vertical cross section of equipotentials on December 17, 2002. 

Figure 34. Transect 2 vertical cross section of equipotentials on September 23, 2003 (study high). 

Transect 3 was a wide shallow stream terrace with low 

stream velocity and high conductivity bed sediments. 

Figures 35-40 show the ground water equipotentials 

under Transect 3 for the chosen dates. Stream water 

consistently moved from the stream into the beds and 

banks at low gradients ranging from 0.005 to 0.02 ft/ft, 

indicating that Transect 3 was a losing reach. On 

December 17, 2002, however, the direction of flow 

reversed and began moving into the stream. During 

the ground water high level on September 23, 2003, 

this reversal was complete, and the transect became 

a gaining reach with a gradient of 0.022 ft/ft. The 

vertical gradients in Transects 1 and 2 were of similar 

magnitude, but gradients at Transect 3 were about an 

order of magnitude less, likely a consequence of the 

conductive stream bed lithology. The bed and banks at 

Transects 1 and 2 were composed of the same gravelly 

clay. Transect 3, however, had more sandy sediments 

and a higher conductivity as shown in Table 1, indicating 

that gradients may be lower. This high conductivity 

may have allowed the flow direction to be more easily 

reversed over a short time frame. 
27

Figure 35. Transect 3 vertical cross section of equipotentials on March 22, 2002. 

Figure 36. Transect 3 vertical cross section of equipotentials on June 24, 2002. 

Figure 37. Transect 3 vertical cross section of equipotentials on August 22, 2002 (study low). 
28

Figure 38. Transect 3 vertical cross section of equipotentials on September 30, 2002. 

Figure 39. Transect 3 vertical cross section of equipotentials on December 17, 2002. 

Figure 40. Transect 3 vertical cross section of equipotentials on September 23, 2003 (study high). 
29

Using the gradients and Darcy’s law as described in 

Methods, near-stream GSI flow was calculated for 

all transects on the selected dates. Flow results for 

Transect 1 are calculated based on a five-foot wide by 

five-foot deep compartment (Table 5). In the incised 

pool on Transect 1, water consistently moved into the 

ground water system at a high rate due to conductive 

sediments and high vertical gradients, indicating that 

this reach was a losing section of the stream. On 

March 22, 2002, a volumetric flow rate, Q, of 6.32 and 

8.06 ft3/day/ft2 moved into the ground water system on 

the right and left banks, respectively. At this rate, the 

ground water residence time, to cover a five foot path, s, 

was 0.32 and 0.25 days, respectively. On June 24, 2002, 

the rate was substantially higher with 35.56 ft3/day/ft2

entering the ground water system on the right bank and 

37.17 ft3/day/ft2 entering the left bank. Higher rates 

were a consequence of the encroaching drought which 

lowered ground water levels below the stream bed. By 

August 22, 2002, the drought was so severe that no 

stream flow was present at Transect 1 and therefore 

no interaction occurred between ground and surface 

water. All surface water was moving into ground water 

just upstream of Transect 2. The GSI returned to a rate 

of 1.55 and 4.46 ft3/day/ft2 to the ground water for the 

right and left banks by December 2002. GSI at Transect 

1 could not be calculated on September 23, 2003, 

the ground water high because the shallow stream 

piezometer was lost in a storm in June 2003. Overall, 

the data demonstrated Transect 1 was in a losing reach 

with high and variable volumetric flow rates and low 

residence times in the stream bed sediments.

Table 5. Ground water (GW) and surface water (SW) flow calculations for Transect 1

Date Compartment dh/dz* dh/dx** dh/ds K (ft/day) q (ft/day) A (ft2) Q( ft3/d) s (ft) n*** t (days) Direction

3/22/2002 Transect 1 Right Bank 0.020 0.005 0.020 310.00 6.32 1.00 6.32 5.00 0.41 0.32 SW to GW

6/24/2002 Transect 1 Right Bank 0.114 0.008 0.115 310.00 35.56 1.00 35.56 5.00 0.41 0.06 SW to GW

8/22/2002 Transect 1 Right Bank NO CONNECTION

9/30/2002 Transect 1 Right Bank 0.035 0.000 0.035 310.00 10.79 1.00 10.79 5.00 0.41 0.19 SW to GW

12/17/2002 Transect 1 Right Bank 0.005 0.000 0.005 310.00 1.55 1.00 1.55 5.00 0.41 1.32 SW to GW

9/23/2003 Transect 1 Right Bank SHALLOW PIEZOMETER DESTROYED

3/22/2002 Transect 1 Left Bank 0.020 0.021 0.026 310.00 8.06 1.00 8.06 5.00 0.41 0.25 SW to GW

6/24/2002 Transect 1 Left Bank 0.114 0.036 0.120 310.00 37.17 1.00 37.17 5.00 0.41 0.06 SW to GW

8/22/2002 Transect 1 Left Bank NO CONNECTION

9/30/2002 Transect 1 Left Bank 0.035 0.033 0.048 310.00 14.82 1.00 14.82 5.00 0.41 0.14 SW to GW

12/17/2002 Transect 1 Left Bank 0.005 0.014 0.014 310.00 4.46 1.00 4.46 5.00 0.41 0.46 SW to GW

9/23/2003 Transect 1 Left Bank SHALLOW PIEZOMETER DESTROYED

*Positive flow from stream: Negative flow to stream **Positive flow out from stream: Negative flow in toward stream ***Calculated from soil core bulk density

The GSI flow results for Transect 2 were calculated 

based on a five-foot wide by five-foot deep compartment 

(Table 6). In this high velocity riffle with an incised 

left bank and a point bar on the right bank, flow 

moved consistently from the ground water into the 

stream. The low rates were a consequence of the less 

conductive sediments and lower vertical gradients. On 

March 22, 2002, a volumetric flow rate, Q, of 0.07 and 

0.10 ft3/day/ft2 moved into the stream from the ground 

water on the right and left banks, respectively. At this 

rate, residence time to cover a five foot path was 21.03 

and 15.17 days for the right and left banks, respectively. 

On June 24, 2002 when flow rates were substantially 

higher, 0.52 ft3

/day/ft2 entered the ground water system 

on the right bank and 0.51 ft3/day/ft2 entered the left 

bank. By August 22, 2002, the drought was so severe 

that no stream flow was present at Transect 2 and 

therefore no GSI. All surface water moved into ground 

water just upstream of Transect 2. The GSI remained in 

this range through the rest of 2002 but returned to 0.90 

and 0.91 ft3/day/ft2 on September 23, 2003, the date of 

the ground water level high. Overall, the data indicated 

that Transect 2 was a consistently gaining reach with low 

and relatively consistent volumetric flow rates and high 

residence times in the stream bed sediments.
30

Table 6. Ground water (GW) and surface water (SW) flow calculations for Transect 2

Date Compartment dh/dz* dh/dx** dh/ds K (ft/day) q (ft/day) A (ft2) Q (ft3/d) s (ft) n*** t (days) Direction

3/22/2002 Transect 2 Right Bank -0.010 -0.016 0.019 3.90 0.07 1.00 0.07 5.00 0.31 21.03 GW to SW

6/24/2002 Transect 2 Right Bank -0.131 -0.025 0.133 3.90 0.52 1.00 0.52 5.00 0.31 2.99 GW to SW

8/22/2002 Transect 2 Right Bank NO CONNECTION

9/30/2002 Transect 2 Right Bank -0.091 -0.023 0.094 3.90 0.37 1.00 0.37 5.00 0.31 4.25 GW to SW

12/17/2002 Transect 2 Right Bank -0.167 -0.028 0.169 3.90 0.66 1.00 0.66 5.00 0.31 2.35 GW to SW

9/23/2003 Transect 2 Right Bank -0.227 -0.044 0.231 3.90 0.90 2.00 1.80 5.00 0.31 1.72 GW to SW

3/22/2002 Transect 2 Left Bank -0.010 -0.024 0.026 3.90 0.10 1.00 0.10 5.00 0.31 15.17 GW to SW

6/24/2002 Transect 2 Left Bank -0.131 -0.019 0.132 3.90 0.51 1.00 0.51 5.00 0.31 3.01 GW to SW

8/22/2002 Transect 2 Left Bank NO CONNECTION

9/30/2002 Transect 2 Left Bank -0.091 -0.0222 0.0935 3.90 0.36 1.00 0.36 5.00 0.31 4.25 GW to SW

12/17/2002 Transect 2 Left Bank -0.167 -0.0318 0.169 3.90 0.66 1.00 0.66 5.00 0.31 2.35 GW to SW

9/23/2003 Transect 2 Left Bank -0.227 -0.0564 0.234 3.90 0.91 1.00 0.91 5.00 0.31 1.70 GW to SW

*Positive flow from stream. Negative flow to stream **Positive flow out from stream, Negative flow in toward stream ***Calculated from soil core bulk density

The GSI flow results for Transect 3 were calculated 

based on a five-foot wide by five-foot deep compartment 

(Table 7). Results indicated a generally losing reach at 

this wide, shallow terrace where water moved slowly 

from the stream into the ground water system despite 

sediments that were conductive. On March 22, 2002, 

a volumetric flow rate, Q, of around 0.61 ft3/day/ft2

passed to the stream from the ground water on the right 

and left banks, respectively. At this rate, the residence 

time, to cover a five-foot path was about 2.4 days. 

On June 24, 2002, the rate was substantially lower; 

0.15 ft3/day/ft2 entered the ground water system on the 

right bank and 0.02 ft3/day/ft2 entered the left bank. On 

August 22, 2002, the drought was severe and the stream 

lost more surface water to the ground water system. The 

stream started to recover and, by December 2002, ground 

water and surface water flowed slowly downstream 

parallel to the stream bed with little interaction. During 

the ground water high on September 23, 2003, the GSI 

had reversed direction and Transect 3 became a gaining 

reach, receiving 1.34 ft3/day/ft2 from the left bank and 

0.71 ft3/day/ft2 from the right bank. Overall, Transect 3 

was a consistently losing reach with long residence times 

which experienced a flow reversal to a gaining reach in 

the wet year of 2003. 

Table 7. Ground water (GW) and surface water (SW) flow calculations for Transect 3

Date Compartment dh/dz* dh/dx** dh/ds K (ft/day) q (ft/day) A (ft2) Q (ft3/d) s (ft) n*** t (days) Direction

3/22/2002 Transect 3 Right Bank 0.020 0.003 0.020 30.50 0.61 1.00 0.61 5.00 0.29 2.37 SW to GW

6/24/2002 Transect 3 Right Bank 0.005 0.002 0.005 30.50 0.15 1.00 0.15 5.00 0.29 9.51 SW to GW

8/22/2002 Transect 3 Right Bank 0.020 0.002 0.019 30.50 0.58 1.00 0.58 5.00 0.29 2.50 SW to GW

9/30/2002 Transect 3 Right Bank 0.010 0.004 0.010 30.50 0.31 1.00 0.31 5.00 0.29 4.75 SW to GW

12/17/2002 Transect 3 Right Bank 0.000 0.002 0.002 30.50 0.06 1.00 0.06 5.00 0.29 23.77 parallel to bed

9/23/2003 Transect 3 Right Bank -0.005 -0.022 0.022 30.50 0.67 2.00 1.34 5.00 0.29 2.16 GW to SW

3/22/2002 Transect 3 Left Bank 0.020 -0.001 0.020 30.50 0.61 1.00 0.61 5.00 0.29 2.39 SW to GW

6/24/2002 Transect 3 Left Bank 0.005 -0.001 0.001 30.50 0.02 1.00 0.02 5.00 0.29 95.08 SW to GW

8/22/2002 Transect 3 Left Bank 0.020 0.003 0.020 30.50 0.61 1.00 0.61 5.00 0.29 2.38 SW to GW

9/30/2002 Transect 3 Left Bank 0.010 0.0008 0.0099 30.50 0.30 1.00 0.30 5.00 0.29 4.80 SW to GW

12/17/2002 Transect 3 Left Bank 0.000 0.000 0.000 30.50 0.00 1.00 0.00 5.00 0.29 NA parallel to bed

9/23/2003 Transect 3 Left Bank -0.005 -0.011 0.012 30.50 0.36 2.00 0.71 5.00 0.29 4.06 GW to SW

*Positive flow from stream; Negative flow to stream **Positive flow out from stream; Negative flow in toward stream ***Calculated from soil core bulk density
31

Temperature verification of ground watersurface water interaction

Transect 1 exhibited strongly losing behavior. This 

movement of surface water to the ground water was 

corroborated by the continuous stream bed ground 

water temperatures measured in the data loggers around 

March 22, 2002 at both the shallow and medium depths 

(Figure 41). These temperatures clearly exhibited the 

expected diurnal temperature variation of the stream 

surface water as it moved relatively quickly into the 

highly conductive bed sediments at Transect 1. This 

diurnal temperature swing in the stream bed piezometers, 

which varied by several degrees Celsius, strongly 

supported the conclusion that this deeply incised pool in 

conductive sediments was consistently losing.

Figure 41. Transect 1 continuous stream bed piezometer 

temperatures.

Vertical equipotentials mapped over time showed 

Transect 2 to be a consistently gaining reach. Data 

from the stream bed piezometer in Transect 2 on the 

days around March 22, 2002 demonstrated relatively 

consistent temperatures at the medium depth as ground 

water discharged to the stream (Figure 42). The 

temperature in the stream bed piezometers displayed 

steady ground water temperature unaffected by the 

diurnal variation in the stream water temperature. The 

mild variation in the shallow piezometer temperature 

over 0.5 degree Celsius range was most likely a function 

of the sediment temperature and not stream water 

movement. If stream water was moving into the bed, as 

it did at Transect 1, the temperature would likely show a 

diurnal variation of several degrees.

Figure 42. Transect 2 continuous stream bed piezometer 

temperatures.

Vertical equipotentials showed Transect 3 to be a 

slowly losing reach with parallel flow under the bed. 

Consequently, temperature in the stream bed piezometers 

would be expected to display the diurnal variation of 

the stream surface temperature. However, continuous 

stream bed temperatures for Transect 3 for the days 

around March 22, 2002 indicated that temperature in 

the shallow piezometer varied diurnally but that the 

medium-depth piezometer did not (Figure 43). This 

temperature signature was closer to that of Transect 2, a 

gaining reach, than that of the losing reach at Transect 1. 

This may have been a consequence of the very slow flow 

into the bed which was too small to strongly reflect the 

diurnal variation of the stream surface temperature. 

Figure 43. Transect 3 continuous stream bed piezometer 

temperatures.
32

Stream flow verification of ground watersurface water interaction

The classification of the specific transects as losing 

or gaining from the above near-stream GSI flow 

calculations and temperature analysis were also verified 

by examining the stream flow measurements at each 

transect. By comparing these values, the flow loss 

and gain between transects can be roughly assessed. 

However, this approach may only be used if no 

tributaries or springs are along the study reach which 

was the case. 

Table 8 shows measurements of surface stream flow 

that were made at the USGS stream flow gage above 

Transect 3, Transect 3, Transect 2, Transect 1, and just 

below Transect 1 over time. Nearly all measurements 

indicated loss of stream flow between the stream 

gage and just below Transect 1, a finding supported 

by the equipotential analysis. Table 8 shows little 

difference in stream flow between Transects 3 and 

2, corresponding to the low GSI calculated at these 

transects. However, a consistent loss of flow between 

Transects 2 and Transect 1 and between Transect 1 and 

below corresponds to the GSI calculations which show 

Transect 1 to be strongly losing. 

Table 8. Stream flow at each of the transects on specific dates

Date Q--Gage 

(cfs)

Q-Transect 3

(cfs)

Q-Transect 2

(cfs)

Q-Transect 1

(cfs)

Q-Below Transect 1

(cfs)

1/15/2002 0.385 0.396* 0.396* 0.357 0.226

3/05/2002 0.489 0.489* 0.489* 0.499 0.397

5/20/2002 0.726 0.711* 0.711* 0.626 0.478

7/15/2002 0.220 0.208* 0.208* 0.133 0.073

9/03/2002 0.166 0.179 0.172 0.141 0.014

11/07/2002 0.691 0.643* 0.643* 0.622 0.579

1/13/2003 ----- 1.45* 1.45* 1.44 1.38

3/10/2003 3.40 3.15* 3.15* 3.89 3.59

5/12/2003 1.62 1.37* 1.37* 1.39 1.34

7/07/2003 2.68 2.53 2.61 2.59 2.29

9/02/2003 1.16 1.04* 1.04* 0.95 0.83

11/09/2004 0.802* 0.802* ----- ----- -----

*--One discharge measurement was made that approximately represents both locations. 

Storm surge ground water-surface water 

interaction

From November 2001 to July 2004, Minebank Run 

stream experienced eighteen large storm discharges 

in response to major precipitation events (Doheny et 

al., 2006). Instantaneous peak discharges during these 

events ranged from 247- 1390 ft3

/sec compared to a 

mean annual discharge of 1.15 ft3/s-4.34 ft3/s (Doheny 

et al., 2006). All of these events were captured in real 

time by the continuous data loggers installed in the 

piezometer nests and monitoring wells. 

A storm on August 3, 2002 with a duration of 1.0 hour 

produced 1.18 inches of rainfall (Doheny et al., 2006). 

The peak gage height measured 7.58 feet and discharge 

in the stream increased from 0.05 ft3

/sec (drought 

conditions) to an instantaneous peak discharge of 725 

ft3/sec (Doheny et al., 2006). The stream gage response 

is shown in Figure 44. Remarkably, the storm surge 

peaked and disappeared within about two hours.
33

Figure 44. Stream discharge hydrograph in response to 

storm event on August 3, 2002.

The shallow and medium depth piezometers in the 

stream bed exhibited the expected rise in water level 

with the storm surge (Figure 45). Strikingly, the rise and 

fall of the hydrograph matched the timing of the stream 

discharge almost exactly and covered some six feet of 

water level fluctuation. The stream bed at Transect 1 

had a high conductivity of 310 ft/day, which enabled 

this almost instantaneous interaction. The right bank 

piezometer had a high conductivity of 170 ft/day and 

also reflected a similar but reduced and delayed rise and 

fall in water level as a consequence of the head loss and 

time lag as water moved through the sediments. The 

piezometer in the left bank, positioned in sediments with 

much lower hydraulic conductivity (7 ft/day), responded 

with a lower and delayed peak. 

Figure 45. Transect 1 piezometer hydrograph response 

to storm event on August 3, 2002.

The response of the stream bed and bank piezometers at 

Transect 2 to the August 2002 event is shown in Figure 

46. The conductivity in the stream bed at Transect 2 was 

3.9 ft/day, about two orders of magnitude less than at 

Transect 1. Though the stream was gaining at Transect 

2, the response of the stream bed piezometers was 

similar to Transect 1. The height of the storm surge at 

this transect was unknown but was likely less than the 

stream gage peak height because this transect was 

situated at a point bar which would have allowed over 

bank flow, thus reducing the height of the storm surge. 

The shallow depth stream bed piezometer data logger 

failed so no data were collected. The right bank 

piezometer located in the point bar near the stream 

reflected about the same rise as the stream bed 

piezometer. The left bank piezometer was located about 

thirty feet from the stream bed piezometer and showed a 

much smaller increase in water level because of the large 

head loss through the gravelly clay sediments. 

Figure 46. Transect 2 piezometer hydrograph response 

to storm event on August 3, 2002.

The response of the stream bed and bank piezometers at 

Transect 3 to the August 2002 event is shown in Figure 

47. This transect was a shallow wide terrace with an 

average stream bed conductivity of 30.5 ft/day. The 

near-stream GSI equipotential analysis showed that 

Transect 3 was a slowly losing reach. As the storm 

surge passed through, water level in the stream bed 

piezometers rose almost four feet. The medium depth 

piezometer exhibited less of a rise, reflecting the head 

loss as the water was pushed into the bed sediments. 

The left bank stream piezometer was in conductive sands 

and thus, showed a similar rise, muted by the distance 

from the stream bed. The right bank piezometer, 

although in similarly conductivity sediments, showed an 

unexpected muted response.
34

Figure 47. Transect 3 piezometer hydrograph response 

to storm event on August 3, 2002.

The August 3, 2002 storm surge clearly drove water 

rapidly into the stream beds and banks as shown by the 

water levels. Despite its limitations for this unsteady, 

turbulent flow system discussed in the methods section, 

Darcy’s law was used as a first estimate of the temporal 

variation in GSI in the stream bed at Transect 1 on the 

August 3, 2002 storm event. Figure 48 displays the flow 

rates calculated using Darcy’s law and the gradient in the 

stream bed as a function of time during the storm surge. 

The results reveal a flow that was strongly driven down 

into the stream bed (positive), peaking at the height of 

the storm surge, falling off, and finally reversing back 

into in the stream (negative). This event demonstrates 

how rapidly the storm surge affects the GSI in the stream 

bed. Such events may significantly influence stream 

function but have not typically been quantified in GSI 

evaluations.

Figure 48. GSI flow rates at Transect 1 during storm 

surge on August 3, 2002.

In addition to the change in water level, data loggers also 

recorded changes in water temperature in the stream bed 

piezometers during and after the storm event. Figure 49 

shows the temperature response at Transect 1 from 

midnight August 2 to midnight August 12. Just before 

the storm event, Transect 1 was a strongly losing reach 

and the stream bed piezometers reflected a diurnal 

variation in both the shallow and medium depth 

piezometers. As the storm surge moved through, stream 

water was driven into the bed. The temperature response 

showed a cooling of almost 8 degrees Celsius in the 

medium depth piezometer. In the days following the 

storm surge, the shallow depth piezometer showed a 

muted diurnal temperature response. The medium depth 

stream bed piezometer reflected a constant temperature 

indicating that the water driven deeper into the bed by 

the storm surge was cooling to match the ground water 

temperature and no new water was moving down into 

the bed. At this time, the losing nature of Transect 1 was 

changed to gaining as stream water driven into the bed 

water was flowing back into the stream. This reversal 

lasted almost 8 days after which the flow was 

reestablished as losing at Transect 1 when the diurnal 

pattern resumed on August 11. 

Figure 49. Transect 1 piezometer temperature response 

to storm event on August 3, 2002.

Figure 50 shows the temperature response at Transect 2 

from midnight August 2 to midnight August 12. The 

shallow stream bed piezometer data logger failed, so no 

data were available at this depth. Just before the storm 

event, Transect 2 was a consistently gaining reach. The 

stream bed and the nearby right bank piezometer in 

the point bar reflected a corresponding ground water 

temperature pattern. As the storm passed, a surge of 

cool stream water was driven into the bed. Unlike the 

response at Transect 1, the medium depth stream bed 

piezometer showed a short dip in temperature at the 

time of the storm surge and then quickly returned to the 
35

steady ground water temperature signature expected 

for a gaining reach. The right bank piezometer did not 

reflect this dip and the left bank piezometer showed no 

response with the stream temperature during the entire 

period. This limited response was likely a function of 

low hydraulic conductivity at this transect (3.9 ft/day) 

which precluded a large amount of water from moving 

into the stream bed and banks. 

Figure 50. Transect 2 piezometer temperature response 

to storm event on August 3, 2002.

Figure 51 shows the temperature response at Transect 3 

from midnight August 2 to midnight August 12. Just 

before the storm event, Transect 3 was a weakly 

losing reach. The shallow piezometer showed the 

diurnal variation of the stream temperature, while the 

medium-depth piezometer reflected the steady ground 

water temperature. As the storm passed, stream water 

was driven into the bed and the temperature response 

showed a cooling of about three degrees Celsius in the 

shallow piezometer and one degree in the medium-depth 

piezometer, a pattern similar to Transect 1, but reflecting 

the lower conductivity of transect 3. The temperature 

also did not return to a pre-storm temperature as did 

Transect 1. The right bank and left bank piezometers 

showed no discernable response to the event.

Figure 51. Transect 3 piezometer temperature response 

to storm event on August 3, 2002.

37

The first objective of this pre-restoration study was to 

assess the stream geomorphology and geology at specific 

stream features and determine their influence on GSI 

at MBR. Our results strongly demonstrated the impact 

of geology and geomorphology on GSI. For example, 

Transect 1 was located at a deep incised pool in highly 

conductive sediments, creating a setting of low velocity 

flow and high hydrostatic gradient between the stream 

and the surrounding ground water. Consequently, the 

stream was consistently losing. Transect 2 was located 

at a narrow riffle with high velocity in low conductivity 

sediments where the reach was consistently gaining at 

a low rate due to the swift flow in a low conductivity 

stream bed, creating a hydraulic gradient conducive to 

flow into the stream. Transect 3 was located in a shallow, 

wide terrace with slow velocity in conductive sediments, 

a feature creating a mildly losing reach that reversed to 

gaining when the ground water levels were high. The 

tremendous variation in GSI at each stream feature 

clearly demonstrated the impact of geomorphology and 

geology. 

The second objective of the pre-restoration study was to 

develop effective and simple methods to characterize, 

measure, and quantify near-stream GSI at specific stream 

features. Our results demonstrated that using a network 

of monitoring wells and piezometer nests to measure 

water levels at defined time intervals was sufficient to 

characterize and quantify the GSI at MBR at both the 

regional and near-stream scale. 

Ground water equipotentials defined by the bi-weekly 

water levels at all of the site wells were used to assess the 

ground water gradients at the regional watershed scale 

at MBR. Our results demonstrated that ground water 

flow varied greatly over space and time at the regional 

scale at MBR. Given this variability, it was important to 

be aware that numerous factors influence ground water 

gradients and the interaction of the ground water with 

the stream on a regional scale. The system was never 

in a steady state and frequent sampling of ground water 

levels and stream flow were necessary to characterize 

hydrology. 

The regional ground water horizontal equipotentials 

were not very useful for interpreting the near-stream GSI 

because they did not reveal the impact of the stream on 

the ground water flow system. This was not unexpected, 

as the majority of groundwater discharges at depth 

from the MBR watershed and only a small amount is 

intercepted by the stream as base flow. For MBR, the 

regional scale should not be used to describe near-stream 

GSI as it can not capture the spatial and temporal scale 

at which this interaction occurs. The regional scale 

horizontal equipotentials also do not address the vertical 

gradients which define the exchange in and out of the 

stream beds and banks at the near-stream scale.

The near-stream GSI at MBR was easily characterized 

and quantified using the vertical equipotentials developed 

from the stream bed and bank piezometer water levels. 

On the near- stream scale, the losing or gaining nature 

of the stream features at each transect could be seen on 

these equipotentials. Equipotentials also showed the 

near-stream GSI to be highly spatially and temporally 

variable at each feature. Consequently, many of the 

typical methods used to quantify GSI at this scale, such 

as tracer tests or numerical heat and flow modeling would 

be impractical or fail to capture this variation. 

Our results showed that a simple model which split 

the stream into two compartments at the thalweg was 

sufficient to quantify the GSI flow at each stream 

feature. The horizontal and vertical gradients for each 

compartment were calculated using the water levels in 

the stream bed piezometers and banks at each sampling 

time. These gradients were then substituted into the 2-D 

vector form of Darcy’s law to determine the magnitude 

and direction of the seepage vector along the resultant 

flow path through the compartment on either side of the 

stream at each transect. The residence time of the water 

to pass through a five foot deep compartment was then 

determined. This simple approach allowed the spatial 

and temporal variation in the near-stream GSI to be 

quantified biweekly using easily obtained ground water 

level measurements. The results showed Transect 1 was 

consistently losing but the magnitude of GSI was highly 

variable, ranging from 1.55 to 37.17 ft3

/day/ft2 with a 

residence time of 1.32 to 0.06 days over the two year 

study period. Transect 2 was in a weakly gaining reach 

with GSI flow ranging from 0.07 to 1.80 ft3/day/ft2. The 

residence time through a five foot depth was from 1.70 

to 21.03 days. Transect 3 was in a losing reach that 

reversed to gaining during a period of high ground water 

levels. As a losing reach, GSI flow at Transect 3 reached 

a maximum of 0.61 ft3/day/ft2 with a residence time of 

2.37 days. As a gaining reach, GSI flow at Transect 3 

reached a maximum gain of 1.34 ft3/day/ft2 with a 

residence time of 2.16 days to pass through five feet. The 

alternating losing and gaining behavior was verified by 

stream flow measurements and continuous temperature 

data at each transect. 

6.0

Discussion
38

The impact of a storm surge on GSI was also evaluated 

at the transects using water level and temperature 

readings collected at 5 minute intervals in the stream bed 

and bank piezometers using continuous data loggers. 

Our results showed that the storm surge drove water 

into the stream bed at each feature to various degrees 

depending on geomorphology and geology. GSI at 

Transect 1 during the storm surge was estimated using 

Darcy’s law and showed flow entering the bed and then 

reversing rapidly. Temperature data also confirmed the 

impact of the storm surge on GSI at each transect and 

helped assess the residence time of the surge in the bed. 

The direction of the near-stream GSI at each of the 

features is critical to the issue of water quality. If the 

flow direction is consistently from the ground water to 

the stream, as found at Transect 2, the water quality in 

the stream is being impacted by ground water quality. 

When no stream water enters the bed or banks, little 

processing of stream contaminants in the sediments 

to improve stream water quality occurs. If flow is 

consistently from the stream into the stream bed and 

banks, as at Transect 1 and Transect 3, beneficial 

processing such as denitrification and adsorption may 

occur (Kaushal et al. 2008). The magnitude of the 

near-stream GSI flow at each feature is also critical. 

High flows in high conductivity settings move more 

fluid through the system as seen at Transect 1. Slower 

flows, like at Transect 2 and 3, move less fluid but 

increase residence time. Increasing residence time is 

critical for increasing the mass removal of nutrients 

and contaminants via biological processes and can only 

be determined by knowing the GSI flow direction and 

magnitude (Kaushal et al. 2008). 

From the assessment of near-stream GSI, it is clear 

that geomorphology and geological setting are major 

factors that impact the magnitude and direction of 

near-steam GSI. These factors will be greatly impacted 

by restoration efforts which can change both the 

geomorphology of the stream channel and the underlying 

sediments. Restoration that changes geology and 

geomorphology will alter GSI. GSI, in turn, influences 

biological processes like nitrification and denitrification 

which control the flux of nitrogen in water and, 

therefore, dictate water quality. Therefore, the potential 

exists to identify and select restoration techniques that 

enhance GSI and improve water quality. 
39

1. Stream channel geomorphology and geologic 

setting, especially stream channel width, depth, and 

sediment lithology strongly influenced near-stream 

GSI at MBR. 

2.The regional ground water horizontal equipotentials 

developed from bi-weekly ground water level 

measurements at MBR varied substantially spatially 

and temporally and did not provide the required 

resolution for interpreting the near-stream GSI.

3.The characterization of near-stream GSI at MBR 

stream features as losing or gaining was easily 

demonstrated using cross-sections of vertical 

equipotentials developed from water levels 

measured in piezometer well nests in the stream bed 

and banks. 

4. Near-stream GSI flow rates were simply and 

effectively quantified at MBR stream features using 

a simple hydrologic analysis of stream bed and bank 

piezometer nest water levels measured bi-weekly. 

5.The direction and magnitude of near stream GSI at 

MBR varied spatially and temporally among and 

within stream features. Some features changed from 

losing to gaining during the study. 

6.Residence times derived from a stream bed 

compartment model at each stream feature at MBR 

were highly variable given their dependency on 

GSI flow rate. Mass removal of nutrients and 

contaminants in stream bed sediments is dependent 

upon residence times.

7.The spatial and temporal variability of GSI at MBR 

precluded the use of traditional stream tracer tests 

and modeling to characterize and quantify GSI as 

they are not suited to capture the highly variable 

nature of the exchange.

8. Near-stream GSI losing and gaining behavior 

was verified by stream flow measurements and 

continuous data logger temperature data at each of 

the stream features at MBR. 

9.Continuous data loggers that measure water level 

and temperature were successfully employed at 

MBR to evaluate the impact of a storm surge on GSI 

at stream features. 

10. Given the dependency of GSI at MBR on stream 

features and their geomorpholigical settings, 

any restoration activity impacting these features 

would likely also impact the GSI. The magnitude 

and direction of GSI change could be easily 

characterized using water levels in piezometer nest 

in the stream bed and banks measured at regular 

time intervals.

7.0

Conclusions

41

8.0

References

Becker, M. W., T. Georgian, H. Ambrose, J. Siniscalchi, 

and K. Fredrick. Estimating flow and flux of 

ground water discharge using water temperature 

and velocity. Journal of Hydrology 296: 221-233 

(2004).

Bencala, K. E., V.C. Kennedy, G.W. Zellweger, A.P. 

Jackman, and R.J. Avanzino. Interactions of 

solutes and stream bed sediment, 1, An experimental 

analysis of cation and anion transport in a mountain 

stream. Water Resources Research 20 (12): 1797-

1804 (1984).

Bencala, K.E. Interactions of solutes and stream 

bed sediment, 2, A dynamic analysis of coupled 

hydrologic and chemical processes that determine 

solute transport. Water Resources Research 20, 

(12): 1804-1814 (1984).

Boulton, A. J., S. Findlay, P. Marmonier, E. Stanley, 

and H. M. Valett. The functional significance of 

the hyporheic zone in streams and rivers. Annual 

Review of Ecological Systems 29: 59-81 (1998).

Bouwer, H. The Bouwer and Rice slug test—an update. 

Ground Water 27:304-309 (1989). 

Bouwer, H. and R.C. Rice. A slug test method for 

determining hydraulic conductivity of unconfined 

aquifers with completely or partially penetrating 

wells. Water Resources Research 12: 423-428 

(1976).

Castro, N.M. and G.M. Hornberger. Surfacesubsurface water interactions in an alluviated 

mountain stream. Water Resources Research 27: 

1613-1621 (1991).

Choi, J., J.W. Harvey, and M. Conklin. Characterizing 

multiple timescales of stream and storage zone 

interaction that affect solute fate and transport in 

streams. Water Resources Research 36 (6): 1511-

1518 (2000).

Cirmo, C.P. and J.J. McDonnell. Linking the hydrologic 

and biogeochemical controls of nitrogen transport 

on near-stream zones of temperate forested 

catchments: a review. Journal of Hydrology 199: 

88-120 (1997).

Conant, B. Delineating and quantifying ground water 

discharge zones using streambed temperatures. 

Ground Water 42 (2): 243-257 March-April 2004.

Constantz, J. Interaction between stream temperature, 

streamflow and groundwater exchanges in alpine 

streams. Water Resources Research 34 (7): 1609-

1615 (1998).

Crowley, W.P., J. Reinhardt, and E.T. Cleaves. Geologic 

Map of Baltimore County and City. Maryland 

Geologic Survey (1976).

Doheny, E.J., R.J. Starsoneck, E.A. Striz, and P. M. 

Mayer. Watershed Characteristics and PreRestoration Surface-Water Hydrology of Minebank 

Run, Baltimore County, Maryland, Water Years 

2002–04,USGS Scientific Investigations Report 

2006-5179 (2006).

Doheny, E.J., R.J. Starsoneck, P.M. Mayer, and E.A. 

Striz. Pre-restoration geomorphic characteristics 

of Minebank Run, Baltimore County, Maryland, 

2002-04. USGS Scientific Investigations Report 

2007-5127 (2007).

Eshleman, K., J.S. Pollard, and A.K. O’Brien. 

Interactions between groundwater and surface 

water in a Virginia Coastal Plain Watershed, I. 

Hydrological Flowpaths. Hydrological Processes 8: 

389-410 (1994).

Falk, D.A., M.A. Palmer, and J.B. Zedler. “Foundations 

of Restoration Ecology.” Island Press, Washington, 

DC. 2006, 364 pp. 

Federal Interagency Stream Restoration Working 

Group (FISRWG), “Stream Corridor Restoration:

Principles, Processes, and Practices,” GPO Item 

No. 0120-A; SuDocs No. A 57.6/2:EN 3/PT.653. 

ISBN-0-934213-59-3, October 1998.

Fryar, A.E., E.J. Wallin, and D.L. Brown. Spatial 

and temporal variability in seepage between a 

contaminated aquifer and tributaries to the Ohio 

River. Ground Water Monitoring and Remediation 

129-146, Summer 2000. 

Gooseff, M.N., J. K. Andersen, S.M. Wondzell, J. 

LaNier, and R. Haggerty. A modeling study of 

hyporheic exchange pattern and the sequence, size 

and spacing of stream bedforms in the mountain 

stream networks, Oregon, USA. Hydrological 

Processes 20: 2443-2457 (2006).

Harvey, J.W. and K.E. Bencala. The effect of streambed 

topography on surface-subsurface water interaction 

in mountain catchments. Water Resources Research 

29 (1) 89-98 (1993).

Harvey, J.W., B.J. Wagner, and K.E. Bencala. 

Evaluating the reliability of the stream tracer 
42

approach to characterize stream-subsurface water 

exchange. Water Resources Research 32 (8): 2441-

2451 (1996).

Harvey, J.W. and B.J. Wagner. “Quantifying hydrologic 

interactions between streams and their subsurface 

hyporheic zones.” Streams and Ground Waters,

Jones, J.A and Mulholland, P. J. eds, Academic 

Press, San Diego, 2000, 425 pp. 

Hayashi, M. and D.O. Rosenberry. Effects of 

groundwater exchange on hydrology and ecology 

of surface water. Ground Water 40 (3): 309-316 

(2002).

Kalbus, E., F. Reinstorf, and M. Schirmer. Measuring 

methods for groundwater-surface water interactions: 

a review. Hydrology and Earth System Sciences

10: 873-887 (2006).

Kasahara, T. and A.H. Hill. Effects of riffle-step 

restoration on hyporheic zone chemistry in N-rich 

lowland streams. Canadian Journal of Fisheries 

and Aquatic Sciences 63: 120-133 (2006).

Kaushal, S., P.M. Groffman, P.M. Mayer, E. Striz, and A. 

Gold. Effects of stream restoration on denitrification 

in an urbanizing watershed. Ecological Applications

18:789-804 (2008). 

Poole, G.C., J.A. Stanford, S.W. Running, and C.A. 

Frissell. Multiscale geomorphic drivers of 

groundwater flow paths: subsurface hydrologic 

dynamics and hyporheic habitat diversity. Journal 

of North American Benthological Society 25 (2): 

288-303 (2006).

Rosgen, D., “Applied River Morphology,” Wildland 

Hydrology, Pagosa Springs, CO, 1996.

Savant, S.A., D.D. Reible, and L.J. Thiobedeaux. 

Convective transport within stable river sediments. 

Water Resources Research 23: 1763-1768 (1987).

 Silliman, S.E., J. Ramirez, and R.L. McCabe. 

Quantifying downflow through creek sediments 

using temperature time-series: one dimensional 

solution incorporating measured surface 

temperature. Journal of Hydrology 167: 99-119 

(1995).

Silliman, S.E. and D.F. Booth. Analysis of timeseries measurements of sediment temperature for 

identification of gaining vs. losing portions of Juday 

Creek, Indiana. Journal of Hydrology 46: 131-148 

(1993). 

Stonestrom, D.A. and J. Constantz. Heat as a Tool for 

Studying Movement of Ground Water Near Streams, 

USGS Circular 1260, 2003.

Stonestrom, D.A. and J. Constantz. Using Temperature 

to Study Stream-Ground Water exchanges,” USGSS 

Geological Survey Fact Sheet 2004-3010, 2004.

Walter, R.C. and D.J. Merritts. Natural streams and the 

legacy of water-powered mills. Science 319: 299-

304 (2008)

Winter, T.C., J.W. Harvey, O.L. Franke, and W.M. 

Alley. Ground Water and Surface Water, A Single 

Resource, USGS Circular 1139, 1998.

Wroblicky, G.J., M.E. Campana, H.M. Valett, and C.N. 

Dahm. Seasonal variation in surface-subsurface 

water exchange and lateral hyporheic area of two 

stream-aquifer systems. Water Resources Research

34 (3): 317-328 (1998).

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