U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2013–5051

Prepared in cooperation with Meagher County Conservation District

Groundwater and Surface-Water Interaction within the 

Upper Smith River Watershed, Montana, 2006–2010

Eden

Camp

Baker

Smith River

Smith River

North Fork

S. Fork

White 

Sulphur 

Springs

USGS Streamflow-Gaging 

Station 06077500

USGS Streamflow-Gaging 

Station 06077200

USGS Streamflow-Gaging 

Station 06076690 USGS Streamflow-Gaging 

Fort Station 06076560

Logan

Smith River

Sheep Creek

Ming Coulee

Hound Creek

Rock Creek

Tenderfoot Creek

Newlan Creek

Beaver Creek

Big Birch Creek

Camas Creek Eagle Creek

Newlan

Reservoir

Lake

Sutherlin

Willow

Creek

Fourmile

Creek

Benton Gulch Whitetail Creek
Front cover.

Upper right: USGS streamflow-gaging station at the Smith River near Eden, Mont., July 4, 2012. 

Photo taken by Abigail L. Caldwell.

Center right: Installation of monitoring well at North Fork Smith River near mouth near White 

Sulphur Springs, Mont., July 13, 2006. Photo taken by James Constantz, U.S. Geological 

Survey.

Lower right: Monitoring well and temporary streamflow-gaging station at the South Fork Smith 

River, 4.8 miles below Cottonwood Creek, near White Sulphur Springs, Mont. August 29, 

2008. Photo taken by Rodney R. Caldwell, U.S. Geological Survey.

Back cover.

Upper: Survey of monitoring wells and temporary streamflow-gaging station at the Smith River 

below North Fork Smith River, near White Sulphur Springs, Mont. July 31, 2007. Photo 

taken by Rodney R. Caldwell, U.S. Geological Survey.

Lower: Aerial photo looking east with the Smith River and the USGS streamflow-gaging 

station at the Smith River below Newlan Creek near White Sulpur Springs, Mont. in the 

foreground and the mouths of Newlan Creek and Big Birch Creek near the center of the 

picture, August 26, 2006. Photo taken by Rodney R. Caldwell, U.S. Geological Survey.
Groundwater and Surface-Water 

Interaction within the Upper Smith River 

Watershed, Montana, 2006–2010

By Rodney R. Caldwell and Cheryl A. Eddy-Miller

Prepared in cooperation with Meagher County Conservation District

Scientific Investigations Report 2013–5051

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

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Suggested citation:

Caldwell, R.R., and Eddy-Miller, C.A., 2013, Groundwater and surface-water interaction within the upper Smith River 

Watershed, Montana 2006–2010: U.S. Geological Survey Scientific Investigations Report 2013–5051, 88 p.,

http://dx.doi.org/10.3133/sir20135051.

ISSN 2328-031X (print)

ISSN 2328-0328 (online)

ISBN 978-1 4113 3721-3
iii

Acknowledgments

We gratefully acknowledge the landowners who gave access to their property for the 

acquisition of data. We also thank members of the Meagher County Conservation District that 

have supported this project. Special thanks to Otto Olson for his local knowledge and contribution of groundwater levels and Newlan Creek Reservoir data. Kathy Hochstrat provided 

streamflow and diversion information for the North Fork Smith River. Several scientists with 

the Montana Department of Natural Resources and Conservation including Larry Dolan, 

Russell Levens, Mike Roberts, and Bill Uthman provided background information including 

access to hydrologic data collected in the area.

This work was completed through the combined effort and expertise of several USGS 

colleagues during the collection, compilation, and analysis of hydrologic data including 

streamflow measurements, surveys, well installation, and groundwater levels. These colleagues 

included Fred Bailey, Craig Bowers, Tom Cleasby, Phil Karper, Sean Lawlor, Steve Lynn, 

Peter McCarthy, Steve Nichols, David Nimick, Kevin Sattler, Todd Schmidt, William Stotts, 

Andy Skerda, and Andrea Stanley. DeAnn Dutton provided field time and was the primary 

Geographic Information System specialist for this project. Hannah Nilges provided field time 

and a thorough review and compilation of the data collected for this study. Michael Cannon 

was involved in the early phases of study design, field work, and data interpretation. A special 

thanks to Ron Shields (USGS, retired) who graciously volunteered several days in the field, 

verified data, and provided guidance on many aspects of this study. Jim Constantz (USGS, 

National Research Program) provided detailed guidance throughout the project from the initial 

groundwater and surface-water interaction monitoring network design, implementation in the 

field, and assistance with the analysis of the data collected.
iv

Contents

Acknowledgments........................................................................................................................................iii

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

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

Purpose and Scope ..............................................................................................................................2

Description of Study Area ...................................................................................................................2

Climate...........................................................................................................................................5

Groundwater.................................................................................................................................5

Surface Water..............................................................................................................................6

Water Use .....................................................................................................................................7

Study Design and Approach ........................................................................................................................7

Groundwater Monitoring.....................................................................................................................7

Surface-Water Monitoring..................................................................................................................9

Synoptic Streamflow Measurements.......................................................................................9

Groundwater and Surface-Water Interaction Monitoring Networks ........................................15

Monitoring and Modeling of Heat Transport..................................................................................15

Surface-Water System ...............................................................................................................................20

Streamflow at Long-Term USGS Streamflow-Gaging Stations...................................................20

Streamflow at Temporary USGS Streamflow-Gaging Stations...................................................23

Groundwater and Surface-Water Interaction within the Upper Smith River Watershed ...............23

Generalized Groundwater Flow Direction and Streamflow Gains and Losses ........................23

Period of Limited Irrigation (October to April).......................................................................23

Irrigation Season (May through September) ........................................................................24

Estimated Groundwater Discharge and the Effects of Irrigation Practices on 

Streamflow .............................................................................................................................40

Qualitative Interpretation of Temperature and Water-Level Data..............................................42

South Fork Smith River at Birky Road (Groundwater and Surface-Water 

Monitoring Site 1).........................................................................................................44

South Fork Smith River 4.8 Miles below Cottonwood Creek (Groundwater and 

Surface-Water Monitoring Site 2).............................................................................44

South Fork Smith River near Mouth (Groundwater and Surface-Water 

Monitoring Site 3).........................................................................................................44

North Fork Smith River near Mouth (Groundwater and Surface-Water 

Monitoring Site 4).........................................................................................................52

Smith River below North Fork Smith River (Groundwater and Surface-Water 

Monitoring Site 5).........................................................................................................52

Smith River at Birch Creek Road and Smith River below Woods Gulch 

(Groundwater and Surface-Water Monitoring Sites 6 and 7)...............................53

Smith River above Mud Springs Creek (Groundwater and Surface-Water 

Monitoring Site 8).........................................................................................................58

Smith River below Newlan Creek (Groundwater and Surface-Water 

Monitoring Site 9).........................................................................................................58

Smith River above Rock Springs Creek (Groundwater and Surface-Water 

Monitoring Site 10).......................................................................................................58

Simulation of Water and Heat Transport ........................................................................................65
v

Figures

1. Location of Smith River watershed, Montana .........................................................................3

2. Generalized geology of the Smith River watershed, Montana .............................................4

3. Monthly mean precipitation at White Sulphur Springs and at Deadman Creek in 

the Little Belt Mountains north of White Sulphur Springs, Montana, 2006–2010. 

Data from National Weather Service station White Sulphur Springs 2 and the 

Natural Resources Conservation Service Deadman Creek Snowpack Telemetry 

(SNOTEL) site.................................................................................................................................6

4. Location of wells used in the study of the upper Smith River watershed, 

Montana .........................................................................................................................................8

5. Location of U.S. Geological Survey streamflow-gaging stations in the upper 

Smith River watershed, Montana ............................................................................................10

6. Location of synoptic streamflow measurement sites in the upper Smith River 

watershed, Montana..................................................................................................................12

7. Daily mean streamflow at the Smith River below Newlan Creek near 

White Sulphur Springs, Montana U.S. Geological Survey streamflow-gaging 

station (station 06076560) and corresponding synoptic streamflow measurement 

dates, water years 2007 and 2008 ............................................................................................14

8. Location of groundwater and surface-water interaction monitoring sites 

in the upper Smith River watershed, Montana......................................................................18

9. Channel geometry, monitoring well network, and thermistor and/or 

pressure transducer locations at the Smith River below North Fork Smith River 

monitoring site (station 06075810). Groundwater altitudes and stream stage for 

May 24, 2007 ................................................................................................................................19

10. Streambed flow and heat transport in a gaining and a losing stream. A, Gaining 

reach. B, Losing reach. (Schematics modified from Constantz and Stonestrom, 

2003) ..............................................................................................................................................21

11. Computed daily streamflow at U.S. Geological Survey Smith River streamflowgaging stations on the Smith River for water years 2006 through 2010.............................22

Simulated Water Fluxes between Groundwater and Surface Water........................................65

Discussion.....................................................................................................................................................65

Summary........................................................................................................................................................68

References Cited..........................................................................................................................................69

Appendixes ...................................................................................................................................................71

Appendix 1. Site-Identification Systems ..............................................................................................72

Appendix 2. Cross-Sectional Model Descriptions and Results........................................................73

South Fork Smith River near Mouth........................................................................................74

North Fork Smith River near Mouth........................................................................................74

Smith River above Mud Springs Creek ..................................................................................76

Appendix 3. Water Flux Calculations of Cross-Section Models.......................................................80

South Fork Smith River near Mouth........................................................................................80

North Fork Smith River near Mouth........................................................................................80

Smith River above Mud Springs Creek ..................................................................................80

Appendix 4. Cross-Sectional Model Sensitivity Analysis..................................................................87
vi

12. Generalized potentiometric surface, groundwater-flow direction, and delineation 

of gaining and losing stream reaches during periods of limited diversions, upper 

Smith River watershed, Montana, 2007–2008. (Based on synoptic measurements 

during March 2007, October 2007, and April 2008)................................................................25

13. Instantaneous streamflow and cumulative tributary inflow of the A, South Fork 

Smith River; B, North Fork Smith River; and C, upper Smith River, Montana, 

March 22, 2007 ............................................................................................................................35

14. Generalized potentiometric surface, groundwater-flow direction, and delineation 

of gaining and losing stream reaches during irrigation season conditions, upper 

Smith River watershed, Montana, August 2007.....................................................................39

15. Instantaneous streamflow and cumulative tributary inflow of the A, South Fork 

Smith River; B, North Fork Smith River; and C, upper Smith River, Montana, 

August 1, 2007..............................................................................................................................41

16. Streamflow at the Smith River below Newlan Creek streamflow-gaging station 

(station 06076560) and the combined streamflow of major tributaries in the upper 

Smith River watershed, Montana, April 2010 through September 2010 ............................42

17. Water temperature at South Fork Smith River temporary streamflow-gaging 

stations and local air temperature, upper Smith River watershed, Montana, 

May 2007 through October 2007 and May 2008 through November 2008 .........................43

18. Data collected at the South Fork Smith River at Birky Road monitoring site 

(station 06075775). A, Altitude of stream stage and groundwater at well SF0606B; 

B, Difference in head between the groundwater at well SF0606B and stream; C, Hourly temperature of stream at station and in monitoring well SF0606B at 

depths of 1.39 feet and 2.89 feet below the streambed; and D, Diel temperature 

variation in monitoring well SF0606B at depths of 1.39 feet and 2.89 feet below 

the streambed, May 2007 through November 2007 and March 2008 through 

December 2008............................................................................................................................45

19. Data collected at the South Fork Smith River monitoring site (station 06075780) 

4.8 mi below Cottonwood Creek. A, Altitude of stream stage and groundwater at 

well SF0605; B, Difference in hydraulic head between groundwater and stream; 

C, Hourly temperature measurements of air at station 06075785, in stream at the 

South Fork Smith River (station 06075780), and in monitoring well SF0605 at depths 

of 1.48 ft and 2.98 ft below the streambed; and D, Diel temperature variation in 

monitoring well SF0605 at depths of 1.48 ft and 2.98 ft below the streambed, 

March 2007 through November 2007 and April 2008 through December 2008.................47

20. Channel geometry, monitoring well network, and thermistor and/or pressure 

transducer locations at South Fork Smith River near mouth monitoring site 

(station 06075785). Groundwater altitudes and stream stage for May 11, 2007 ...............49

21. Data collected at the South Fork Smith River near mouth monitoring site (station 

06075785). A, Altitude of stream stage and groundwater at well SF0603; 

B, Difference in hydraulic head between the groundwater at well SF0603 and 

stream; C, Hourly temperature measurements of air at station 06075785, stream 

at station 06075785, in monitoring well SF0603 at depths of 1.65 ft and 3.15 ft 

below the streambed; and D, Diel temperature variation in monitoring well 

SF0603 at depths of 1.65 ft and 3.15 ft below the streambed, March 2007 

through December 2007 and March 2008 through December 2008 ...................................50

22. Channel geometry, monitoring well network, and thermistor and/or pressure 

transducer locations at North Fork Smith River near mouth monitoring site 

(station 06075700). Groundwater altitudes and stream stage for May 11, 2007 ...............53
vii

23. Data collected at the North Fork Smith River near mouth monitoring site (station 

06075700). A, Altitude of stream stage and groundwater at well NF0602; B, 

Difference in hydraulic head between the groundwater at well NF0602 and 

stream; C, Hourly temperature measurements of air at station 06075785, stream 

at station 06075700, and in monitoring well NF0602 at depths of 1.42 ft and 2.92 ft 

below the streambed; and D, Diel temperature variation in monitoring well NF0602 

at depths of 1.42 ft and 2.92 ft below the streambed, March 2007 through 

December 2007 and March 2008 through December 2008 ..................................................54

24. Data collected at the Smith River below North Fork Smith River monitoring site 

(station 06075810). A, Altitude of stream stage and groundwater at well SR0616; 

B, Difference in hydraulic head between groundwater at well SR0616 and stream; 

C, Hourly temperature measurements of air at station 06075785, in stream at station 

06075810, and in monitoring well SR0616 at depths of 1.72 ft and 3.22 ft below the 

streambed; and D, Diel temperature variation in monitoring well SR0616 at depths 

of 1.72 ft and 3.22 ft below the streambed, March 2007 through November 2007 

and March 2008 through December 2008...............................................................................56

25. Channel geometry, monitoring well network, and thermistor and/or pressure 

transducer locations at Smith River above Mud Springs Creek monitoring site 

(station 06075850). Groundwater altitudes and stream stage for April 30, 2008...............59

26. Data collected at the Smith River above Mud Springs Creek monitoring site 

(station 06075850). A, Altitude of stream stage and groundwater at well SR0609; 

B, Difference in hydraulic head between groundwater at well SR0609 and stream; 

C, Hourly temperature measurements of air at station 06075785, in stream at station 

06075850, and in monitoring well SR0609 at depths of 1.4 ft and 2.9 ft below the 

streambed; and D, Diel temperature variation in monitoring well SR0609 at depths 

of 1.4 ft and 2.9 ft below the streambed, March 2007 through December 2007 and 

March 2008 through December 2008.......................................................................................60

27. Channel geometry, monitoring well network, and thermistor and/or pressure 

transducer locations at Smith River above Rock Springs Creek monitoring site 

(station 06076580). Groundwater altitudes and stream stage for May 9, 2007 .................62

28. Data collected at the Smith River above Rock Springs Creek monitoring site 

(station 06076580). A, Altitude of stream stage and groundwater at well SR0605; 

B, Difference in hydraulic head between groundwater at wells SR0605 and 

SR0606B and stream; C, Hourly temperature measurements of air at station 

06075785, in stream at station 06076580, and in monitoring well SR0605 at depths 

of 1.6 ft and 3.1 ft below the streambed; and D, Diel temperature variation in 

monitoring well SR0605 at depths of 1.6 ft and 3.1 ft below the streambed, 

March 2007 through November 2007 and March 2008 through December, 2008 ............63

Appendix Figures

1-1. Location-numbering system for wells.....................................................................................72

2-1. Boundary conditions and observation points for the VS2DH model, South Fork 

Smith River near mouth (station 06075785) monitoring site cross section........................73

2-2. Observed and simulated temperature for the South Fork Smith River near mouth 

monitoring site (station 06075785), 2007 and 2008. (Horizontal and vertical hydraulic 

conductivities were set at 3x10-6 feet per second.) ..............................................................75

2-3. Boundary conditions and observation points for the VS2DH model, North Fork 

Smith River near mouth (station 06075700) monitoring site cross section........................76
viii

2-4. Observed and simulated temperature for the North Fork Smith River near mouth 

monitoring site (station 06075700), 2007 and 2008. (Horizontal and vertical hydraulic 

conductivities were set at 3x10-6 feet per second) ...............................................................77

2-5. Boundary conditions and observation points for the VS2DH model, Smith River 

above Mud Springs Creek (station 06075850) monitoring site cross section...................78

2-6. Observed and simulated temperatures for the Smith River above Mud Springs 

Creek monitoring site (station 06075850), 2008. (Horizontal and vertical hydraulic 

conductivities were set at 4x10-5 feet per second.) ..............................................................79

3-1. Water-flux information, in cubic feet per day (ft

3

/d), for the South Fork Smith 

River near mouth (station 06075785) modeled cross section. A, Location of 

model boundaries; B, Daily flux across model boundaries, 2007; C, Daily flux 

across model boundaries, 2008; and D, Simulated temperature distributions 

inside the model domain on three selected dates (arrows indicate direction and 

magnitude of water flux). Flux estimates for the streambed boundary (blue lines) 

are shown as positive when water is moving from the groundwater system to the 

stream and negative when moving from the stream to the groundwater system. 

Flux estimates from the bottom and side boundaries (black, red, and purple lines) 

are positive when the water flux is into the surrounding groundwater system and 

negative when the water flux past the boundary is into the stream..................................81

3-2. Water-flux information, in cubic feet per day (ft

3

/d), for the North Fork Smith 

River near mouth (station 06075700) modeled cross section. A, Location of model 

boundaries; B, Daily flux across model boundaries, 2007; C, Daily flux across 

model boundaries, 2008; and D, Simulated temperature distributions inside the 

model domain on three selected dates (arrows indicate direction of water flux).

Flux estimates for the streambed boundary (blue lines) are shown as positive 

when water is moving from the groundwater system to the stream and negative 

when moving from the stream to the groundwater system. Flux estimates for the 

bottom and side boundaries (black, red, and purple lines) are positive when the 

water flux is into the surrounding groundwater system and negative when the 

water flux past the boundary is into the stream....................................................................83

3-3. Water-flux information, in cubic feet per day (ft

3

/d), for the Smith River above 

Mud Springs Creek (station 06075850) modeled cross section. A, Location of model 

boundaries; B, Daily flux across model boundaries, 2008; and C, Simulated 

temperature distributions inside the model domain on three selected dates 

(arrows indicate direction of water flux). Flux estimates for the streambed 

boundary (blue lines) are shown as positive when water is moving from the 

groundwater system to the stream and negative when moving from the stream 

to the groundwater system. Flux estimates for the bottom and side boundaries 

(black, red, and purple lines) are positive when the water flux is into the 

surrounding groundwater system and negative when the water flux past the 

boundary is into the stream ......................................................................................................85

4-1. Observed and simulated temperatures with varied hydraulic conductivity values 

and ratios of vertical (Kv) to horizontal (Kh) hydraulic conductivity of the VS2DH 

2-dimensional model of the Smith River above Mud Springs Creek monitoring site 

(station 06075850), 2008..............................................................................................................88
ix

Tables

1. U.S. Geological Survey streamflow-gaging stations in the Smith River watershed, 

Montana .......................................................................................................................................11

2. Site descriptions and locations for synoptic streamflow measurements in the 

upper Smith River watershed, Montana.................................................................................13

3. Groundwater and surface-water interaction monitoring sites in the upper 

Smith River watershed, Montana ............................................................................................16

4. Summary of gains and losses calculated from synoptic streamflow measurements 

during periods of limited diversions, upper Smith River watershed, Montana, 

2007–08 .........................................................................................................................................24

5. Estimated streamflow gains and losses, upper Smith River watershed, Montana, 

March 22, 2007 ............................................................................................................................26

6. Estimated streamflow gains and losses, upper Smith River watershed, 

 October 16, 2007..........................................................................................................................29

7. Estimated streamflow gains and losses, upper Smith River watershed, April 10, 

2008 ...............................................................................................................................................32

8. Estimated streamflow gains and losses, upper Smith River watershed, Montana, 

August 1, 2007..............................................................................................................................36

9. Summary of hydraulic parameters used in final calibrated VS2DH simulations of 

selected modeled cross sections in the upper Smith River watershed, Montana..........66

10. Summary of estimated water flow across streambed boundaries of the South 

Fork Smith River, North Fork Smith River, and Smith River modeled cross sections ......66
x

Conversion Factors, Datum, and Acronyms

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3) 

cubic foot (ft3) 0.02832 cubic meter (m3) 

acre-foot (acre-ft) 1,233 cubic meter (m3)

Flow rate

acre-foot per year (acre-ft/yr) 1,233 cubic meter per year (m3/yr)

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

foot per day (ft/d) 0.3048 meter per day (m/d)

foot per year (ft/yr) 0.3048 meter per year (m/yr)

cubic foot per second (ft3/s)

cubic foot per day (ft3/d)

 0.02832

 28.31685

cubic meter per second (m3/s)

liters per day (L/d)

cubic foot per month (ft3/month) 0.02832 liter per second (L/s)

gallon per day (gal/d) 0.003785 cubic meter per day (m3/d)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s)

Mass

ounce (oz) 28.35 gram (g) 

pound (lb) 0.4536 kilogram (kg) 

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83)

Altitude, as used in this report, refers to distance above specified vertical datum.

Water-year definition:

Water year is the 12-month period from October 1 through September 30 of the following 

calendar year. The water year is designated by the calendar year in which it ends. For example, 

water year 2007 is the period from October 1, 2006 through September 30, 2007.
xi

Acronyms and abbreviations used in this report:

E east

ET evapotranspiration 

GIS Geographic Information System

GPS Global Positioning System 

GWIC Groundwater Information Center 

lsd land surface datum

MBMG Montana Bureau of Mines and Geology

MCCD Meagher County Conservation District

MDNRC Montana Department of Resources and Conservation

N north

NRCS Natural Resources Conservation Service

NWIS National Water Information System

RTK Real-Time Kinematic

USGS U.S. Geological Survey

2-D two-dimensional
Abstract

The 125-mile long Smith River, a tributary of the 

Missouri River, is highly valued as an agricultural resource 

and for its many recreational uses. During a drought starting 

in about 1999, streamflow was insufficient to meet all of the 

irrigation demands, much less maintain streamflow needed for 

boating and viable fish habitat. In 2006, the U.S. Geological 

Survey, in cooperation with the Meagher County Conservation District, initiated a multi-year hydrologic investigation of 

the Smith River watershed. This investigation was designed 

to increase understanding of the water resources of the upper 

Smith River watershed and develop a detailed description of 

groundwater and surface-water interactions. A combination 

of methods, including miscellaneous and continuous groundwater-level, stream-stage, water-temperature, and streamflow 

monitoring was used to assess the hydrologic system and the 

spatial and temporal variability of groundwater and surfacewater interactions. Collectively, data are in agreement and 

show: (1) the hydraulic connectedness of groundwater and 

surface water, (2) the presence of both losing and gaining 

stream reaches, (3) dynamic changes in direction and magnitude of water flow between the stream and groundwater with 

time, (4) the effects of local flood irrigation on groundwater 

levels and gradients in the watershed, and (5) evidence and 

timing of irrigation return flows to area streams. 

Groundwater flow within the alluvium and older 

(Tertiary) basin-fill sediments generally followed land-surface 

topography from the uplands to the axis of alluvial valleys 

of the Smith River and its tributaries. Groundwater levels 

were typically highest in the monitoring wells located within 

and adjacent to streams in late spring or early summer, likely 

affected by recharge from snowmelt and local precipitation, 

leakage from losing streams and canals, and recharge from 

local flood irrigation. The effects of flood irrigation resulted in 

increased hydraulic gradients (increased groundwater levels 

relative to stream stage) or even reversed gradient direction at 

several monitoring sites coincident with the onset of nearby 

flood irrigation. Groundwater-level declines in mid-summer 

were due to groundwater withdrawals and reduced recharge 

from decreased precipitation, increased evapotranspiration, 

and reduced leakage in some area streams during periods 

of low flow. Groundwater levels typically rebounded in late 

summer, a result of decreased evapotranspiration, decreased 

groundwater use for irrigation, increased flow in losing 

streams, and the onset of late-season flood irrigation at some 

sites.

The effect of groundwater and surface-water interactions 

is most apparent along the North and South Forks of the Smith 

River where the magnitude of streamflow losses and gains 

can be greater than the magnitude of flow within the stream. 

Net gains consistently occurred over the lower 15 miles of the 

South Fork Smith River. A monitoring site near the mouth of 

the South Fork Smith River gained (flow from the groundwater to the stream) during all seasons, with head gradients 

towards the stream. Two upstream sites on the South Fork 

Smith River exhibited variable conditions that ranged from 

gaining during the spring, losing (flowing from the stream to 

the groundwater) during most of the summer as groundwater 

levels declined, and then approached or returned to gaining 

conditions in late summer. Parts of the South Fork Smith River 

became dry during periods of losing conditions, thus classifying this tributary as intermittent. The North Fork Smith River 

is highly managed at times through reservoir releases. The 

North Fork Smith River was perennial throughout the study 

period although irrigation diversions removed a large percentage of streamflow at times and losing conditions persisted 

along a lower reach. The lowermost reach of the North Fork 

Smith River near its mouth transitioned from a losing reach to 

a gaining reach throughout the study period.

Groundwater and surface-water interactions occur 

downstream from the confluence of the North and South Fork 

Smith Rivers, but are less discernible compared to the overall 

magnitude of the main-stem streamflow. The Smith River was 

perennial throughout the study. Monitoring sites along the 

Smith River generally displayed small head gradients between 

the stream and the groundwater, while one site consistently 

showed strongly gaining conditions. Synoptic streamflow 

measurements during periods of limited irrigation diversion in 

2007 and 2008 consistently showed gains over the upper 

41.4 river miles of the main stem Smith River where net 

gains ranged from 13.0 to 28.9 cubic feet per second. 

Continuous streamflow data indicated net groundwater 

discharge and small-scale tributary inflow contributions of 

around 25 cubic feet per second along the upper 10-mile reach 

of the Smith River for most of the 2010 record. A period of 

intense irrigation withdrawal during the last two weeks in 

Groundwater and Surface-Water Interaction within the 

Upper Smith River Watershed, Montana, 2006–2010

By Rodney R. Caldwell and Cheryl A. Eddy-Miller
2 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

May was followed by a period (early June 2010 to mid-July 

2010) with the largest net increase (an average of 71.1 cubic 

feet per second) in streamflow along this reach of the Smith 

River. This observation is likely due to increased groundwater 

discharge to the Smith River resulting from irrigation return 

flow. By late July, the apparent effects of return flows receded, 

and the net increase in streamflow returned to about 25 cubic 

feet per second. 

Two-dimensional heat and solute transport VS2DH models representing selected stream cross sections were used to 

constrain the hydraulic properties of the Quaternary alluvium 

and estimate temporal water-flux values through model boundaries. Hydraulic conductivity of the Quaternary alluvium of 

the modeled sections ranged from 3x10-6 to 4x10-5 feet per 

second. The models showed reasonable approximations of the 

streambed and shallow aquifer environment, and the dynamic 

changes in water flux between the stream and the groundwater 

through different model boundaries.

Introduction

The Smith River watershed is an important agricultural 

and recreational area in Meagher and Cascade Counties in 

west-central Montana (fig. 1). Nearly 35,000 acres of the 

Smith River watershed are irrigated, primarily with water 

directly withdrawn from the Smith River and its tributaries 

(Cannon and Johnson, 2004). Downstream (northward), the 

agricultural fields are replaced by a scenic canyon that draws 

thousands of recreationists each year. During a recent drought, 

which started in about 1999, streamflow was insufficient to 

meet all of the irrigation demands, much less maintain streamflow needed for boating and viable fish habitat (Montana 

Department of Natural Resources and Conservation, 2003). 

Largely in response to the lack of available surface water for 

irrigation, some irrigators have already switched, or are proposing to switch, from flood irrigation to sprinkler irrigation 

(Montana Department of Natural Resources and Conservation, 

2003). Additionally, some irrigators have considered using 

groundwater instead of surface water as a source of irrigation 

water. The effects of these changes in irrigation practices on 

the Smith River watershed are unknown.

In April 2006, the U.S. Geological Survey (USGS), in 

cooperation with the Meagher County Conservation District 

(MCCD), began a study of the hydrogeology of the Smith 

River Watershed. The project was supported through the 

combined resources of the Montana Department of Natural 

Resources and Conservation’s (MDNRC) Reclamation and 

Development Grants Program and the USGS Cooperative 

Water Program. The study was designed to improve understanding of the groundwater system with an emphasis on 

groundwater and surface-water interactions through a systematic program of data collection, research, and analysis. 

The findings of this study can assist water managers with the 

development of a comprehensive management program for 

the use and protection of water resources in the Smith River 

watershed.

This report is the second in a series of reports describing

the water resources of the Smith River watershed. The first 

report (Nilges and Caldwell, 2012) is a USGS Open-File 

report that summarizes the hydrologic data collected and 

compiled for the hydrogeologic study of Smith River watershed through water year 2010. This report describes the general hydrology and groundwater and surface-water interactions 

within the upper watershed based on collected data.

Purpose and Scope

The purpose of this report is to describe the spatial and 

temporal interactions of groundwater and surface water in the 

upper Smith River watershed. The description of groundwater and surface-water interactions includes: (1) generalized 

groundwater-flow direction, (2) the delineation of gaining 

(flow from the groundwater to the stream) and losing (flow 

from the stream to the groundwater) reaches of the upper 

Smith River and selected tributaries, (3) quantification of 

gains and losses under different hydrologic conditions, (4) 

the relation between groundwater levels and stream stage, 

(5) hydraulic properties of the Quaternary alluvium, and (6) 

estimated water fluxes between groundwater and surface water 

at selected stream cross sections.

Description of Study Area

The Smith River is a tributary to the Missouri River with 

a watershed encompassing approximately 2,000 square miles 

(mi2) or nearly 1.3 million acres in Meagher and Cascade 

Counties of west-central Montana. Study efforts were focused 

primarily on the approximately 1,200 mi2 in the upper watershed above the Tenderfoot Creek drainage (fig. 1).

The Smith River watershed lies within the structurally 

complex Northern Rocky Mountains Physiographic Division 

described by Fenneman and Johnson (1946), is characterized 

by somewhat rugged mountains, and relatively flat to incised 

river valleys. Elevations range from about 9,500 feet (ft) in the 

Big Belt Mountains to about 3,320 ft at the mouth of the Smith 

River near Ulm, Montana. Sedimentary, igneous, and metamorphic rocks ranging in age from Precambrian to Quaternary 

are present (fig. 2); the entire sequence of sedimentary rocks, 

including sandstone, siltstone, shale, limestone, and dolomite, 

totals approximately 26,000 ft in thickness (Groff, 1965). 

Runkel (1986) estimated Tertiary-age (65 to 2 million years 

ago) basin-fill sedimentary deposits may be 1,500 ft thick near 

White Sulphur Springs. Quaternary alluvium (Qal), which 

includes gravel, sand, and silt deposits, occurs along the Smith 

River and its tributaries. Igneous rocks crop out at various 

locations including an igneous sill located below the mouths 

of Big Birch and Newlan Creeks incised by the Smith River.
Introduction 3

Figure 1. Location of Smith River watershed, Montana.

N:\Jeff\den12_cmra00_0091_sir_caldwell\figures\figure_01.ai

R.3 W. R.2 W. R.1 W. R.1 E. R.2 E. R.3 E. R.4 E. R.5 E. R.6 E. R.7 E. R.8 E. R.9 E. R.10 E.

T.12 N.

T.20 N.

T.19 N.

T.18 N.

T.17 N.

T.16 N.

T.15 N.

T.14 N.

T.13 N.

T.11 N.

T.10 N.

T.9 N.

T.8 N.

T.7 N.

T.6 N.

T.5 N.

Missouri

River

47°30'

Smith River

South Fork

Willow

Creek

Fourmile

Creek

Beaver Creek

Big Birch Creek

Camas Creek

Lake

Sutherlin

Sheep Creek

 Newlan

Reservoir

Benton Gulch

Whitetail Creek

Newlan Creek

Smith River

North Fork

Rock Creek

Eagle Creek

Smith River

Ming Coulee

Tenderfoot Creek

Eden

Hound Creek

06077200

06076690

06076560

06076560

Ulm

Belt

Simms

Neihart

Cascade

Townsend

Sand

Coulee

Great

Falls

East

Helena

White

Sulphur

Springs

Fort

Logan

Camp

Baker

111°30' 111°00’ 110°30'

47°00’

46°30'

Little Belt

Mountains

Big Belt

Mountains

Crazy

Mountains

Castle

Mountains

Upper Smith River

Watershed

White Sulphur

Springs

White Sulphur

Springs

Deadman Creek

06077500

CHOUTEAU

COUNTY

CASCADE

COUNTY

BROADWATER

COUNTY

MEAGHER

COUNTY

JEFFERSON

COUNTY

LEWIS

AND

CLARK

COUNTY

JUDITH

BASIN

COUNTY

87

87

89

89

89

89

12

12

287

12

15

15

294

Deadman Creek

Base modified from U.S. Geological Survey digital National

Elevation Dataset, 30 meter, 2006

U.S. Census Bureau TIGER data, 1:100,000, 2000

Lambert Conformal Conic Projection

Standard parallels 45° and 49°, central meridian -109° 30"

North American Datum of 1983 (NAD83). EXPLANATION

0 5 10 MILES

0 5 10 KILOMETERS

River

Flathead

River

Missouri

Yellowstone

MONTANA

Butte

Helena

Bozeman

Missoula

Billings

Great Falls Clark Fork

River

Bitterroot

River

Study area

Location map

U.S. Geological Survey streamflow-

 gaging station and identifier

Natural Resources Conservation Service

 Snopack Telemetry (SNOTEL) Station

 and identifier

National Weather Service Climate

 Station and identifier

Upper Smith River Watershed boundary
4 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Figure 2. Generalized geology of the Smith River watershed, Montana.

N:\Jeff\den12_cmra00_0091_sir_caldwell\figures\figure_02.ai

R.2 W. R.1 W. R.1 E. R.2 E. R.3 E. R.4 E. R.5 E. R.6 E. R.7 E. R.8 E. R.9 E. R.10 E.

T.12 N.

T.20 N.

T.19 N.

T.18 N.

T.17 N.

T.16 N.

T.15 N.

T.14 N.

T.13 N.

T.11 N.

T.10 N.

T.9 N.

T.8 N.

T.7 N.

T.6 N.

Missouri

River

Smith River

South Fork

Beaver Creek

Big Birch Creek

Camas Creek

Sheep Creek

Newlan Creek

Smith River

North Fork

Rock Creek

Smith River

Ming Coulee

Tenderfoot Creek

Eden

Hound Creek

Ulm

Belt

Neihart

Cascade

Townsend

Sand

Coulee

White

Sulphur

Springs

Fort

Logan

Camp

Baker

111°45' 111°30' 111°15' 111°00' 110°45'

46°30'

CASCADE

COUNTY

BROADWATER

COUNTY

MEAGHER

COUNTY

LEWIS

AND

CLARK

COUNTY

JUDITH

BASIN

COUNTY

87

87

89

89

89

89

12

12

287

12

15

15

294

46°45'

47°15'

47°00'

Qal

Qal

Geology modified from Ross, Andrews, and Witkind,1955.

EXPLANATION

Quaternary alluvium

Geologic unit

Quaternary glacial drift

Tertiary to Cretaceous intrusive

 igneous rocks

Cretaceous to Jurassic rocks

Tertiary to Cretaceous volcanics

Tertiary sedimentary rocks

Qal

Qg

Ts

TKb Precambrian rocks

Permian to Cambrian rocks

TKv

KJu

u

u

u

u

u

Ts

Ts

Ts

Ts

TKb

TKb

Pu

Pu

Pu

Pu

Pu

Pu

KJu

KJu

TKv

TKv

TKv

Base modified from U.S. Geological Survey digital National

Elevation Dataset, 30 meter, 2006

U.S. Census Bureau TIGER data, 1:100,000, 2000

Lambert Conformal Conic Projection

Standard parallels 45° and 49°, central meridian -109° 30"

North American Datum of 1983 (NAD83).

0 5 10 MILES

0 5 10 KILOMETERS
Introduction 5

Grass and mixed rangeland accounts for the majority 

(about 55 percent) of the land cover in the watershed (U.S. 

Geological Survey, 2000). Conifer forests are located at the 

higher elevations and account for 39 percent of the total area. 

Pasture and crop lands account for most of the remaining 

land cover. The more arid lower elevations are dominated by 

grasslands with riparian vegetation near the streams. The study 

area contains a low-density rural population of approximately 

2,437 people, with 925 of those in the largest community, 

White Sulphur Springs (U.S. Census Bureau, 2000). Principal 

industries within the region are dependent upon the natural resources, and include agriculture, forestry, mining, and 

tourism.

Climate

Climate in the Smith River watershed is semi-arid with 

some semi-humid areas in the upper mountains. Summer 

temperatures are mild in the valleys with cooler temperatures 

in the higher elevations of the mountains. Monthly mean temperatures during the period of study (2006-2010) near White 

Sulphur Springs ranged from 14.9 oF (-9.5oC) in January 

1998 to 72.4oF (22.4oC) in July 2007 (National Climatic Data 

Center, 2011).

Precipitation varies both spatially and temporally in the 

Smith River watershed and is highly influenced by orography. 

Average annual precipitation (1971–2000) ranged from less 

than 12 inches per year (in/yr) in the lowland to the west and 

northwest of White Sulphur Springs to over 40 in/yr in the 

mountains (Oregon State University PRISM Group, 2006; 

Farnes, 2007). Monthly mean precipitation during the period 

of study (calendar years 2006–2010) near White Sulphur 

Springs (National Weather Service station White Sulphur 

Springs 2) ranged from 0.01 inch in February 2006 to 3.3 

inches in July 2009, whereas monthly mean precipitation at 

the Deadman Creek Natural Resources Conservation Service 

(NRCS) Snowpack Telemetry (SNOTEL) site ranged from 

about 0.7 inches in July 2007 and September 2008 to 6.9 

inches in April 2010 (fig. 3). Higher elevations accumulate 

more precipitation as snowpack and retain it longer into the 

summer than the lower elevations. The period of snowpack 

melting in the upper elevations is an important element of the 

seasonal water budgets.

Groundwater

Subsurface deposits and geologic formations that are 

capable of yielding useable quantities of water to wells or 

springs are classified as aquifers, whereas lower permeability deposits or geologic formations that restrict groundwater 

movement are classified as confining units (Heath, 1983). 

Unconfined or “water-table” aquifers occur where the saturated zone of the aquifer can equilibrate to atmospheric pressure and is free to rise and decline (Heath, 1983). Confined 

aquifers contain groundwater that is confined under pressure 

between layers of relatively impermeable or significantly 

less permeable material (Lohman, 1979). The confining unit 

prevents water in a confined aquifer from equilibrating with 

atmospheric pressure. The water level in a properly sealed 

well drilled into a confined aquifer will rise above the top of 

the aquifer (Heath, 1983). Semi-confined or leaky aquifers 

are partially confined by layers of low permeability through 

which water can still flow, but equilibration with atmospheric 

pressure is impeded (Freeze and Cherry, 1979). The potentiometric surface, which is the hydraulic head (the height above a 

datum, such as sea level), is an imaginary surface connecting 

points to which water would rise in tightly cased wells from a 

given point in an aquifer (Lohman, 1979). The potentiometric 

surface, like the water table in an unconfined aquifer, rises and 

falls in response to recharge and discharge of the aquifer. 

Unconfined, confined, and semi-confined aquifers occur 

within the basin-fill deposits (Quaternary alluvium and 

Tertiary sedimentary deposits) in the Smith River watershed 

(Montana Department of Natural Resources and Conservation, 

2003). The confined and semi-confined units are created by 

layers of low-permeability material of variable thickness and 

extent (such as clay layers). Most shallow wells in the study 

area (generally less than 30 ft deep) completed in Quaternary 

alluvium appear to be in unconfined aquifers. However, wells 

completed in Tertiary sediment and deeper wells in Quaternary 

alluvium may be in unconfined, semi-confined, or confined 

aquifers, depending on the presence or absence of confining 

layers. Often, drillers’ logs lack sufficient detail to determine if 

confining layers exist. Therefore, discussions and maps representing groundwater levels within this report are a composite 

of water levels in confined, semi-confined, and unconfined 

aquifers and these water levels collectively are herein referred 

to as the potentiometric surface.

The most productive and developed aquifers in the Smith 

River watershed are the Quaternary alluvium and the generally weakly consolidated Tertiary sediments of the valley 

lowlands and tributary drainages (Montana Department of 

Natural Resources and Conservation, 2003). The Quaternary 

alluvial aquifers are generally composed of sand and gravel 

with some clay layers. Most high-yielding wells are completed 

in the Quaternary alluvium. The Tertiary sedimentary aquifers 

generally have lower permeability due to the composition of 

fine-grained sediments. A few high-yielding wells have been 

completed in the Tertiary sediments, including an exploration well recently drilled for the USGS (Nilges and Caldwell, 

2012). A review of documented wells completed in the older 

sedimentary and igneous rocks included in the Groundwater 

Information Center (GWIC) database (Montana Bureau of 

Mines and Geology (MBMG), 2011) indicated that they typically have low yields and are only utilized for domestic and 

stock purposes.

Recharge to the Quaternary alluvium and Tertiary sediments of the valley lowlands and tributary drainages occur 

as infiltration from precipitation, leakage from streams and 

canals, and as leakage from underlying rocks. Discharge from 

the groundwater system occurs by withdrawal from wells, 
6 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

seepage to streams and drains, and evapotranspiration (ET). 

ET occurs in the lowlands where the water table is close to 

land surface in riparian areas with common phreatophytes 

(such as willows), in flood-irrigated agricultural lands, and in 

grasslands and pastures.

Surface Water

Perennial streamflow consists of surface runoff from 

precipitation and snowmelt and contributions from groundwater, termed base flow. Base flow changes spatially and temporally and is a function of groundwater recharge, ET, aquifer 

characteristics, groundwater-flow direction, and groundwater 

withdrawals. Streamflow is also affected by reservoir operation and diversions in the upper watershed. Reservoir and 

diversion operations may result in augmentation of low flows 

by releases from storage reservoirs, and dampening of high 

flows by reservoir storage.

The Smith River originates about 3 mi southwest of 

White Sulphur Springs at the confluence of the North and 

South Forks of the Smith River. The North Fork Smith River 

begins in the Little Belt Mountains to the northwest of White 

Sulphur Springs and flows for nearly 40 mi to the southwest as 

it gains flow from tributaries originating in both the Little Belt 

and the Castle Mountains before joining the South Fork Smith 

River. The South Fork Smith River begins in the Castle Mountains and flows to the west and northwest for about 38 mi. The 

South Fork Smith River gains flow from tributaries originating

from both the Castle and Big Belt Mountains and from an 

unsealed artesian well near its headwaters. The Smith River 

flows roughly northwest for about 125 mi until it ultimately 

joins the Missouri River near Ulm. The upper Smith River 

meanders extensively, particularly for the first 12 mi above 

Newlan Creek, where it flows through shallow, entrenched 

lowlands in gently rolling prairies, agricultural land, and small 

canyons. Beginning near the mouth of Eagle Creek, about 

45 mi downstream from its origin, the Smith River flows 

Figure 3. Monthly mean precipitation at White Sulphur Springs and at Deadman Creek in the Little Belt Mountains north of White 

Sulphur Springs, Montana, 2006–2010. Data from National Weather Service station White Sulphur Springs 2 and the Natural Resources 

Conservation Service Deadman Creek Snowpack Telemetry (SNOTEL) site.

N:\Jeff\den12_cmra00_0091_sir_caldwell\figures\figure_03.ai Monthly mean precipitation, in inches

White Sulphur Springs 2 weather station

EXPLANATION

Deadman Creek SNOTEL site

2006 2007 2008 2009 2010

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0
Study Design and Approach 7

through steep-sided canyons for nearly 60 mi. Major tributaries include Big Birch Creek, Camas Creek, Rock Creek, and 

Hound Creek from the Big Belt Mountains and Newlan Creek, 

Sheep Creek, Eagle Creek, and Tenderfoot Creek from the 

Little Belt Mountains.

Several reservoirs are located in the upper watershed. 

Most of the reservoirs are small (less than 500 acre-ft), 

privately owned impoundments (Montana Natural Resource 

Information System, 2010). The largest reservoirs are Lake 

Sutherlin (North Fork Smith River Reservoir) and Newlan 

Creek Reservoir. Lake Sutherlin (14,200 acre-ft capacity) is 

located about 9 mi northeast of White Sulphur Springs in the 

upper North Fork Smith River drainage (Montana Natural 

Resource Information System, 2010). Newlan Creek Reservoir 

(15,600 acre-ft capacity) is located about 6 mi northwest of 

White Sulphur Springs and collects inflow from upper Newlan 

Creek including water diverted from Sheep Creek into Newlan 

Creek (Montana Natural Resource Information System, 2010). 

Numerous canals and irrigation ditches traverse the upper 

watershed, some established in the 1870s. Canals used to 

transport irrigation and stock water range from short diversions 

from tributaries to longer systems such as the 15.5 mi-long 

South Side Canal diversion from the North Fork Smith River. A 

high-resolution hydrography data set (U.S. Geological Survey, 

2010) includes approximately 170 mi of canals and ditches in 

the Smith River watershed, with most (about 96 mi) located in 

the upper watershed. Drainage ditches, typically in the valley 

flats, were constructed to lower the water table to increase 

arable land for agricultural use. Several of these drainage 

ditches were observed to flow all year, every year, during the 

course of this study.

Water Use

Estimated surface-water and groundwater withdrawals 

in the Smith River watershed for the year 2000 were approximately 224.54 million gallons per day (Mgal/day) (252,200 

acre-feet per year (acre-ft/yr); Cannon and Johnson, 2004). 

Surface water sources supplied most (221.3 Mgal/day) of 

the water withdrawn. Nearly 99 percent of the water withdrawn was used for the irrigation of 34,650 acres of cropland 

and pasture (Cannon and Johnson, 2004). Of the water used 

for irrigation, which is withdrawn intermittently during the 

growing season from May through September, surface water 

sources supplied about 220 Mgal/day and groundwater sources 

supplied the remaining 2.7 Mgal/day. 

About 94 percent of the irrigated land in the Smith River 

watershed is located in the upper part of the watershed, above 

the Tenderfoot Creek drainage (Montana Department of Natural Resources and Conservation, 2003). About two-thirds of 

this land is flood irrigated, and the remaining third is irrigated 

using sprinklers (Montana Department of Natural Resources 

and Conservation, 2003). The majority of flood irrigation typically occurs during late spring to early summer. Some fields 

are flood irrigated again in late summer to early fall if water is 

available. Depending on the crop type, sprinkler irrigation can 

occur intermittently throughout the growing season 

(late-spring through summer). Alfalfa is typically irrigated 

throughout the summer, but suspended for a short period 

during mid-summer to allow for the first cutting. Approximately 89 percent of irrigated land is used to produce hay 

(grass and alfalfa) and grain, with the remaining irrigated land 

used for pasture (Cannon and Johnston, 2004).

Study Design and Approach

Methods used to study the hydrologic system in the study 

area and quantify groundwater interaction with surface water 

included periodic and continuous groundwater-level, streamstage, streamflow, and water-temperature measurement, and 

two-dimensional heat and solute transport modeling. Measurements were collected from a hydrologic monitoring network 

that included shallow monitoring wells, existing water-supply 

wells, deeper exploration wells, long-term USGS streamflowgaging stations, and temporary USGS streamflow-gaging stations. These monitoring sites are uniquely identified according 

to standard USGS procedures (see appendix 1). Data collected 

for this study are published in Nilges and Caldwell (2012) 

along with a detailed description of data collection methods.

Many groundwater and surface-water interaction investigations examine the surface runoff and base-flow components 

of perennial streamflow. Base flow is commonly determined 

using hydrograph separation, which differentiates the surfacerunoff component from the groundwater discharge component 

of streamflow. Direct base-flow estimates are difficult to determine for streams in which the flow is regulated by dams or 

diversions, which disrupt normal hydrograph recession curves. 

Base flow estimates were not calculated for the upper Smith 

River watershed, as flows were likely augmented by releases 

from storage reservoirs and dampened by reservoir storage.

Groundwater Monitoring

There are approximately 900 documented water wells in 

the Smith River watershed as shown in the GWIC database 

(Montana Bureau of Mines and Geology (MBMG), 2011). The 

wells are unevenly distributed, with the majority located in 

the more populated area near White Sulphur Springs and the 

valley flats, and few if any wells in the foothills and mountains. Throughout 2006, 139 wells were field inventoried for 

this study (fig. 4). These wells were selected on the basis of 

spatial distribution, availability of well log records, landowner permission, access, and proximity to the Smith River 

and its tributaries. The geographic positions of the wells were 

measured with a handheld global positioning system or with 

survey-grade Global Positioning System (GPS) survey equipment and Real-Time Kinematic (RTK) positioning. Altitudes 

of wellheads were also surveyed using survey-grade GPS survey equipment and RTK positioning with estimated accuracy 

of +/- 0.1 ft or less.
8 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Figure 4. Location of wells used in the study of the upper Smith River watershed, Montana.

N:\Jeff\den12_cmra00_0091_sir_caldwell\figures\figure_04.ai

Camp

Baker

Fourmile Cree

Willow k

Creek

South

Side

Canal

Spring Creek

Eagle Creek

Neihart

White 

Sulphur 

Springs

Smith River

Sheep Creek

Rock Creek

Tenderfoot Creek

Newlan Creek

Beaver Creek

Big Birch Creek

Camas Creek

47°00'

46°30'

46°45'

46°15'

111°15' 111°00' 110°45'

T. 14 N.

T. 13 N.

T. 12 N.

T. 11 N.

T. 10 N.

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

R. 2 E. R. 3 E. R. 4 E. R. 5 E. R. 6 E. R. 7 E. R. 8 E. R. 9 E.

Groundwater-level observation network well

Exploration well drilled for this study

Well used only for lithologic information

Groundwater/surface-water interaction 

observation network well

South Fork Smith River

North Fork

Smith River

0 3 6 MILES

0 3 6 KILOMETERS

Fort

Logan

CASCADE

COUNTY

MEAGHER

COUNTY

BROADWATER

COUNTY

JUDITH

BASIN

COUNTY

89

89

89

12

12

294

Base modified from U.S. Geological Survey digital National

Elevation Dataset, 30 meter, 2006

U.S. Census Bureau TIGER data, 1:100,000, 2000

Lambert Conformal Conic Projection

Standard parallels 45° and 49°, central meridian -109° 30"

North American Datum of 1983 (NAD83).

EXPLANATION

Upper Smith River Watershed boundary
Study Design and Approach 9

Groundwater-level monitoring provides information on 

groundwater-level trends and seasonal fluctuations in response 

to climate, water use, and canal operation. Available groundwater-level data collected by the USGS, MCCD, MDNRC, 

and the MBMG were utilized during this study (Nilges and 

Caldwell, 2012). Groundwater-level data include: (1) one-time 

water levels collected during well inventories, (2) water levels 

measured in approximately 80 wells on a semi-monthly basis 

by the USGS and other agencies over various time periods 

between the early 1990s and 2010, (3) water levels measured 

continuously by using pressure transducers (see Groundwater 

and Surface-Water Interaction Monitoring Networks section), 

and (4) water levels measured synoptically by the USGS in 

approximately 50 wells in March 2007, August 2007, October 

2007, March 2008, and March 2010. The synoptic and semimonthly water-level measurements resulted in a robust data set 

that was used to create synoptic potentiometric-surface maps. 

All groundwater-level data utilized for this study are published 

in Nilges and Caldwell (2012) along with a more detailed 

description of data-collection methods.

Surface-Water Monitoring

Streamflow data ranging from miscellaneous measurements to continuous data were measured at 65 sites during this 

study. All streamflow measurements were made using standard 

USGS protocols (Rantz and others, 1982; Nolan and Shields, 

2000; Turnipseed and Sauer, 2010). Streamflow data for sites 

within the Smith River watershed are available online through 

the USGS National Water Information System (NWIS) at 

http://waterdata.usgs.gov/mt/nwis/.

The USGS operated four long-term streamflow-gaging 

stations (fig. 1, fig. 5, and table 1) and 13 temporary streamflow-gaging stations (fig. 5 and table 1) during this study. The 

long-term streamflow gaging stations were operated 4 years or 

more and were ongoing, newly established, or reestablished 

during the course of the study. The long-term streamflowgaging stations include the following; (1) Smith River below 

Newlan Creek near White Sulphur Springs (station number 

06076560) at river mile 112.1, (2) Smith River near Fort 

Logan (station number 06076690) at river mile 83.6, (3) Smith 

River below Eagle Creek near Fort Logan (station number 

06077200) at river mile 80.8, and (4) Smith River near Eden, 

Montana (station number 06077500) at river mile 27.0 (fig. 1), 

which is downstream from the upper Smith River watershed.

Temporary streamflow-gaging stations are defined herein 

as short-term, study-specific staff gages, instrumented with 

pressure transducers over various time periods. Stage was 

recorded hourly from April through November during 2007 

and 2008 at five of the stations as part of the groundwater and 

surface-water interaction monitoring network (see Groundwater and Surface-Water Interaction Monitoring Networks 

section). Six additional temporary, study-specific streamflowgaging stations were installed in 2010 in an effort to estimate 

tributary inflow in the upper watershed. Stage was recorded 

hourly at 10 temporary stations during 2010. 

Streamflow was measured periodically at the streamflowgaging stations to create rating curves of streamflow versus 

stage. Staff gages were surveyed using survey-grade GPS 

equipment and RTK positioning with estimated accuracy of 

+/- 0.1 ft or less. Standard differential leveling surveys were 

conducted annually from 2006 through 2008 and in 2010 in 

order to examine the magnitude of changes in elevation due to 

frost heaving.

Synoptic Streamflow Measurements

Four large-scale synoptic streamflow measurements 

(seepage runs) were conducted within the upper Smith River 

watershed (fig. 6, table 2). Streamflow, temperature, and 

specific conductance measurements were made at up to 45 

sites along the Smith River and its tributaries during each of 

the synoptic streamflow measurements over a short period 

(less than 8 hours). The timing of the synoptic events was 

determined by monitoring weather forecasts and real-time 

streamflow data from USGS gaging stations in an attempt to 

minimize precipitation and snowmelt effects on streamflow. 

Rapidly changing streamflow conditions and storm events 

were avoided.

Synoptic streamflow measurement sites were selected 

based on aerial photographs, maps, ease of access, and the 

results of an April 2006 longitudinal survey of the Smith River 

from the confluence of North and South Forks of the Smith 

River to just above the mouth of Sheep Creek near Fort Logan 

(USGS gaging station 06076690). The longitudinal survey 

included the continuous logging of location from a watercraft 

using a handheld global positioning system. Temperature and 

specific conductance measurements of the stream water were 

simultaneously measured using a self-contained multi-parameter water-quality data logger (an In-situ Inc. multi-parameter 

TROLL 9500). Locations of observed tributaries and diversions as well as possible groundwater inflow indicated by 

observed changes in specific conductance and temperature 

were noted. An effort was made to quantify tributary and 

groundwater inflows at each of these locations by either 

measuring streamflow of tributaries at their mouths or by 

calculating tributary or groundwater inflows by measuring the 

streamflow in the main stem above and below the tributaries 

or suspected groundwater inflow.

Three of the synoptic streamflow measurements, on 

March 22, 2007, October 16, 2007, and April 10, 2008, 

were selected as periods of nearly stable streamflow with 

limited irrigation diversions and were used to determine net 

gains or losses (fig. 7). A fourth measurement, on August 1, 

2007, occurred during a period of intense local irrigation and 

was designed to examine altered flow conditions during an 

irrigation season. Numerous individual diversions were not 

measured during the August 1 event; therefore, that synoptic 
10 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Figure 5. Location of U. S. Geological Survey streamflow-gaging stations in the upper Smith River watershed, 

Montana.

N:\Jeff\den12_cmra00_0091_sir_caldwell\figures\figure_05.ai

Camp

Baker

Fourmile Cree

Willow k

Creek

South

Side

Canal

Spring Creek

Eagle Creek

Neihart

White 

Sulphur 

Springs

Smith River

Sheep Creek

Rock Creek

Tenderfoot Creek

Newlan Creek

Beaver Creek

Big Birch Creek

Camas Creek

47°00'

46°30'

46°45'

46°15'

111°15' 111°00' 110°45'

T. 14 N.

T. 13 N.

T. 12 N.

T. 11 N.

T. 10 N.

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

R. 2 E. R. 3 E. R. 4 E. R. 5 E. R. 6 E. R. 7 E. R. 8 E. R. 9 E.

Long-term U.S. Geological Survey streamflow-

 gaging station and identifier—Number

 corresponds to Table 1

Temporary U.S. Geological Survey streamflow-

 gaging station and identifier—Number

 corresponds to Table 1

South Fork Smith River

North

Fork Smith River

0 3 6 MILES

0 3 6 KILOMETERS

Fort

Logan

CASCADE

COUNTY

MEAGHER

COUNTY

BROADWATER

COUNTY

JUDITH

BASIN

COUNTY

89

89

89

12

12

294

Base modified from U.S. Geological Survey digital National

Elevation Dataset, 30 meter, 2006

U.S. Census Bureau TIGER data, 1:100,000, 2000

Lambert Conformal Conic Projection

Standard parallels 45° and 49°, central meridian -109° 30"

North American Datum of 1983 (NAD83).

EXPLANATION

Upper Smith River Watershed boundary

11

9

8

7

6 5

4

3

2

1

15

14

13

13

1

12

10

16
Study Design and Approach 11

Map 

number 

(fig. 5)

Station 

identification 

number

Location description Latitude Longitude Begin 

date End date

Streamflow 

measurement 

count

1

Station type

 1 06075775 South Fork Smith River at 

Birky Road 1.6 miles below 

Cottonwood Creek

46°26’48” 110°55’49” 3/22/2007 9/24/2010 18 Temporary

 2 06075780 South Fork Smith River 4.8 

miles below Cottonwood 

Creek

46°28’30” 110°56’47” 3/22/2007 10/22/2008 9 Temporary

 3 06075785 South Fork Smith River near 

mouth

46°31’24” 110°57’23” 3/22/2007 9/24/2010 17 Temporary

 4 463638110460501 North Fork Smith River at 

Studhorse Road near White 

Sulphur Springs, Montana

46°36’38” 110°46’08” 3/19/2010 9/24/2010 11 Temporary

 5 463426110464801 Fourmile Creek near mouth 

near White Sulphur Springs, 

Montana

46°34’26” 110°46’51” 5/18/2010 9/24/2010 10 Temporary

 6 463438110512401 Trinity Spring at Pond outflow 

near White Sulphur Springs, 

Montana

46°34’38” 110°51’27” 3/16/2010 9/24/2010 8 Temporary

 7 463340110501401 Willow Creek at South Side 

Canal near White Sulphur 

Springs, Montana

46°33’40” 110°50’17” 3/23/2010 10/8/2010 14 Temporary

 8 463242110520101 South Side Canal at Willow 

Creek near White Sulphur 

Springs, Montana

46°32’42” 110°52’04” 6/29/2010 10/8/2010 5 Temporary

 9 06075700 North Fork Smith River near 

mouth near White Sulphur 

Springs, Montana

46°32’09” 110°56’52” 1/13/1993 7/30/2010 50 Temporary

10 06075850 Smith River above Mud Springs 

Creek

46°34’14” 111°02’02” 3/22/2007 10/22/2008 8 Temporary

11 463357111031801 Big Birch Creek below diversion at 1.7 miles near White 

Sulphur Springs, Montana

46°33’57” 111°03’21” 7/19/2007 10/5/2010 15 Temporary

12 06076550 Newlan Creek at mouth near 

White Sulphur Springs, 

Montana

46°35’31” 111°02’57” 1/14/1993 10/1/2010 45 Temporary

13 06076560 Smith River below Newlan 

Creek near White Sulphur 

Springs, Montana

46°35’27” 111°03’29” 9/23/2004 12/16/2010 71 Long term

14 06076580 Smith River above Rock 

Springs Creek

46°37’57” 111°05’30” 9/14/2006 10/23/2008 9 Temporary

15 06076690 Smith River near Fort Logan, 

Montana

46°47’45” 111°10’44” 9/23/1977 10/28/2010 275 Long term

16 06077200 Smith River below Eagle Creek 

near Fort Logan, Montana

46°49’41” 111°11’32” 8/1/1996 12/16/2010 145 Long term

See 

fig.1.

 06077500 Smith River near Eden, 

Montana

47°11’21” 111°23’11” 8/4/1988 12/9/2010 53 Long term

1

Temporary, streamflow-gaging station operated less than 4 years over various time periods; long term, streamflow-gaging station operated 4 years or more.

Table 1. U.S. Geological Survey streamflow-gaging stations in the Smith River watershed, Montana.

[Map number, used for cross reference for locations plotted on figure 5; Station identification number, see “Site-Identification Systems” section for explanation; 

Latitude and longitude reported in degrees, minutes, and seconds relative to North American Datum of 1983]
12 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Figure 6. Location of synoptic streamflow measurement sites in the upper Smith River watershed, Montana.

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_06.ai

Camp

Baker

Fourmile Cree

Willow k

Creek

South

Side

Canal

Spring Creek

Eagle Creek

Neihart

White 

Sulphur 

Springs

Smith River

Sheep Creek

Rock Creek

Tenderfoot Creek

Newlan Creek

Beaver Creek

Big Birch Creek

Camas Creek

47°00'

46°30'

46°45'

46°15'

111°15' 111°00' 110°45'

T. 14 N.

T. 13 N.

T. 12 N.

T. 11 N.

T. 10 N.

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

R. 2 E. R. 3 E. R. 4 E. R. 5 E. R. 6 E. R. 7 E. R. 8 E. R. 9 E.

Stream reach—Reach number corresponds

 to Tables 5, 6, 7, and 8

Synoptic streamflow measurement site and

 identifier—Number corresponds to Table 2

South Fork Smith River

North

Fork Smith River

0 3 6 MILES

0 3 6 KILOMETERS

Fort

Logan

CASCADE

COUNTY

MEAGHER

COUNTY

BROADWATER

COUNTY

JUDITH

BASIN

COUNTY

89

89

89

12

12

294

Base modified from U.S. Geological Survey digital National

Elevation Dataset, 30 meter, 2006

U.S. Census Bureau TIGER data, 1:100,000, 2000

Lambert Conformal Conic Projection

Standard parallels 45° and 49°, central meridian -109° 30"

North American Datum of 1983 (NAD83).

EXPLANATION

Upper Smith River Watershed boundary

Reach 1

Reach 2

Reach 3

Reach 4

Reach 5

11 12

8

7

6

5

4 3

2

45 44

43

42

41

37-40

1

36

35

34

33

32 31

30

29

13

10

9

22

21 23

26

24 25

27 28

20

19 18

17

16

16

14 and 15

Inset map
Study Design and Approach 13

Map 

number 

(fig. 6)

Station identification 

number Location description River mile Latitude Longitude

South Fork Smith River

 1 06075775 South Fork Smith River at Birky Road 1.6 miles 

below Cottonwood Creek

15.0 46°26’48” 110°55’49”

 2 06075780 South Fork Smith River 4.8 miles below Cottonwood Creek11.8 46°28’30” 110°56’47”

 3 463057110570301 Hot Springs Creek at mouth 4.3 46°30’57” 110°57’06”

 4 463107110571401 Unnamed tributary to South Fork Smith River 

(number 1)

3.8 46°31’07” 110°57’17”

 5 463120110571701 Unnamed tributary to South Fork Smith River 

(number 2)

3.2 46°31’20” 110°57’20”

 6 06075785 South Fork Smith River near mouth 3.1 46°31’24” 110°57’23”

 7 463141110583701 South Fork Smith River at mouth 0.1 46°31’41” 110°58’40”

North Fork Smith River

 8 463327110523701 North Fork Smith River above Spring Creek 8.4 46°33’27” 110°52’40”

 9 463333110525501 Spring Creek near mouth 8.4 46°33’33” 110°52’58”

10 463256110545201 North Fork Smith River at Highway 360 Bridge 5.3 46°32’56” 110°54’55”

11 06075700 North Fork Smith River near mouth 2.6 46°32’09” 110°56’52”

12 463148110583001 North Fork Smith River at mouth 0.3 46°31’48” 110°58’33”

Smith River

13 06075810 Smith River below North Fork Smith River 122.2 46°32’07” 110°59’48”

14 463241111001801 Smith River above unnammed tributary 0.5 miles 

above Birch Creek Road

120.8 46°32’41” 111°00’21”

15 463240111001501 Unnamed tributary at mouth 0.5 miles above Birch 

Creek Road

120.7 46°32’40” 111°00’18”

16 463253111002901 Ditch at mouth on south side of Birch Creek Road 120.3 46°32’53” 111°00’32”

17 463255111002801 Ditch at mouth on north side of Birch Creek Road 120.2 46°32’55” 111°00’31”

18 463313111010501 Woods Gulch at mouth 119.1 46°33’13” 111°01’08”

19 463327111011401 Smith River below Woods Gulch 118.8 46°33’26” 111°01’14”

20 463330111011201 Ditch at mouth below Woods Gulch 118.4 46°33’30” 111°01’15”

21 463413111014701 Ditch at mouth above Mud Springs Creek (number 1) 117.1 46°34’13” 111°01’50”

22 463355111013901 Ditch at mouth above Mud Springs Creek (number 2) 116.3 46°33’55” 111°01’42”

23 06075850 Smith River above Mud Springs Creek 116.0 46°34’14” 111°02’02”

24 463437111021701 Smith River below Mud Creek 115.2 46°34’37” 111°02’20”

25 463518111030101 Smith River above Big Birch Creek 112.7 46°35’18” 111°03’04”

26 06075900 Big Birch Creek at mouth 112.6 46°35’14” 111°03’16”

27 06076550 Newlan Creek at mouth 112.4 46°35’31” 111°02’57”

28 06076560 Smith River below Newlan Creek 112.1 46°35’29” 111°03’27”

29 463636111050701 Smith River above Thompson Gulch 108.2 46°36’36” 111°05’10”

30 463638111051801 Thompson Gulch near mouth 108.1 46°36’38” 111°05’21”

31 463743111042701 Spring Creek at Highway 360 Bridge 106.5 46°37’43” 111°04’30”

32 06076580 Smith River above Rock Springs Creek 105.1 46°37’57” 111°05’30”

33 463911111055501 Smith River below Rock Springs Creek 103.1 46°39’11” 111°05’58”

34 464033111083501 Smith River at Highway 360 Bridge 98.4 46°40’33” 111°08’38”

Table 2. Site descriptions and locations for synoptic streamflow measurements in the upper Smith River watershed, Montana.

[Map number, used for cross reference for locations plotted on figure 6; Station identification number, see “Site-Identification Systems” section for explanation; 

River mile, distance above mouth; Latitude and longitude reported in degrees, minutes, and seconds referenced to North American Datum of 1983; main stem 

South Fork Smith River, North Fork Smith River, and Smith River stations in bold type]
14 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Map 

number 

(fig. 6)

Station identification 

number Location description River mile Latitude Longitude

Smith River—Continued

35 464034111092001 Unnamed tributary to Smith River at mouth near 

Fort Logan

 97.8 46°40’34” 111°09’23”

36 464043111100801 Unnamed tributary to Smith River from Soldiers 

Lake

 96.8 46°40’43” 111°10’11”

37 464218111113501 Smith River above Camas Creek 94.3 46°42’18” 111°11’31”

38 06076600 Camas Creek at mouth 94.2 46°42’19” 111°11’35”

39 06076650 Benton Gulch at mouth 94.1 46°42’20” 111°11’36”

40 464222111113201 Smith River below Benton Gulch 94.0 46°42’22” 111°11’35”

41 464550111094601 Smith River below Beaver Creek 88.1 46°45’50” 111°09’49”

42 06076690 Smith River near Fort Logan 83.6 46°47’45” 111°10’44”

43 464816111110001 Sheep Creek at mouth 82.7 46°48’17” 111°11’03”

44 464942111095101 Eagle Creek near mouth 81.4 46°49’42” 111°09’54”

45 06077200 Smith River below Eagle Creek 80.8 46°49’41” 111°11’32”

Table 2. Site descriptions and locations for synoptic streamflow measurements in the upper Smith River watershed, Montana.—

Continued 

[Map number, used for cross reference for locations plotted on figure 6; Station identification number, see “Site-Identification Systems” section for explanation; 

River mile, distance above mouth; Latitude and longitude reported in degrees, minutes, and seconds referenced to North American Datum of 1983; main stem 

South Fork Smith River, North Fork Smith River, and Smith River stations in bold type]

Water year 2007

Month

Water year 2008

0 Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

50

100

150

200

350

250

300

Streamflow, in cubic feet per second

Daily mean streamflow

EXPLANATION

Synoptic streamflow measurement

Figure 7. Daily mean streamflow at the Smith River below Newlan Creek near White Sulphur Springs, Montana U.S. Geological Survey 

streamflow-gaging station (station 06076560) and corresponding synoptic streamflow measurement dates, water years 2007 and 2008.
Study Design and Approach 15

measurement cannot be used with confidence for gain/loss 

estimates. 

The resulting gain or loss computed between measuring

points during a synoptic streamflow measurement is an estimate of the net rate of water exchange between the surface 

water and the groundwater, averaged over the length of a 

specified reach. The volume of water gained or lost by the 

stream during each synoptic measurement was calculated as 

follows:

 Net seepage gain or loss = Qd—T—Qu + D (1)

Where

 Qd = streamflow at the downstream end of a reach, 

 in cubic feet per second

 T = sum of all tributary inflows within a reach, in 

 cubic feet per second

 Qu = streamflow at the upstream end of a reach, 

 in cubic feet per second

 D = sum of all diversion outflows within a reach, in 

cubic feet per second

The calculated value of each gain or loss has a level of 

uncertainty that is associated with each streamflow measurement. This uncertainty in streamflow measurements, also 

known as measurement error, standard error, or indeterminate error, results from inherent inaccuracies associated with 

the equipment and techniques used during each streamflow 

measurement. Sources of these uncertainties in USGS streamflow measurements have been analyzed and a rating system 

has been developed to estimate this measurement error for 

individual streamflow measurements (Sauer and Meyer, 

1992). The rating system used in this investigation to estimate 

measurement error for each streamflow measurement is as 

follows: good with measured streamflow within 5 percent of 

actual streamflow (5 percent used in calculations); fair with 

measured streamflow within 5 to 8 percent of actual streamflow (8 percent used in calculations); and poor with measured 

streamflow 8 percent or greater of the actual streamflow (10 

percent used in calculations). Estimated error associated with 

each calculated gain or loss value was determined by using the 

flowing propagation of error formula:

 (2)

Where 

 s is the error propagated from all estimated 

individual measurement errors and a, b, n 

are the estimated errors for the streamflow 

measurement at each site.

Groundwater and Surface-Water Interaction 

Monitoring Networks

The groundwater and surface-water interaction monitoring networks, each with one to five monitoring wells (31 

total), were installed during 2006 and 2007 at 10 sites along 

the North and South Forks of the Smith River and the Smith 

River. Sites corresponded either with staff gages installed for 

this study or an existing streamflow-gaging station (table 3, 

fig. 8). Since all of the groundwater and surface-water network 

sites were located in low-lying areas adjacent to streams, 

nearly all sites were in areas with nearby flood irrigation. Five 

sites with 1 to 3 wells were designed to determine the general groundwater and surface-water flow direction, whereas 

five sites with 4 or 5 wells were designed to also estimate 

the hydraulic characteristics of the near-stream Quaternary 

alluvium and water flux (amount of water flowing between 

the groundwater and stream, see Monitoring and Modeling of 

Heat Transport section). Wells at each site were installed along 

a cross section perpendicular to the stream. Sites with one 

to three wells typically had wells installed within the stream 

approximately 2.5 ft from the stream bank. A typical cross section at sites with four to five wells had wells installed on both 

stream banks approximately 2.5 ft from the water’s edge, and 

wells installed within the stream approximately 2.5 ft from 

each stream bank (fig. 9). Deeper wells were installed within 

the stream at three sites to examine the relation of head (water 

level) to depth. In some cases, data from nearby existing monitoring wells or water-supply wells were also available. The 

area representing the stream banks, which is typically unsaturated, was generalized and designated as soil for this study. All 

data collected at the groundwater and surface-water interaction monitoring networks used for this study are published 

in Nilges and Caldwell (2012) along with a more detailed 

description of data collection methods.

Monitoring and Modeling of Heat Transport

The use of heat as a tracer in conjunction with stage 

and groundwater-level measurements has proven to be an 

effective method for estimating groundwater and surfacewater exchange at the streambed interface (Constantz and 

Stonestrom, 2003; Constantz, 2008; Essaid and others, 2008; 

Eddy-Miller and others, 2009). Water temperatures in area 

streams typically range from 0 to about 25 °C annually and 

can vary several degrees on a daily basis due to variations 

in air temperature (Nilges and Caldwell, 2012). Typically, 

groundwater is insulated from the daily air-temperature variation and groundwater temperature therefore remains fairly 

constant. Heat is transported continuously between the stream, 

s = ±( ) a + ±( )b + ±( ) 2 2 2 n
16 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed Map Number (fig. 8) Location description and station identification number of stream Site identification number of well Station name of well Well local identification number Latitude of well Longitude of well Altitude of land surface (feet) Well depth (feet) Open interval top (feet) Remarks 1 South Fork Smith River at Birky Road 1.6 miles below Cotton- wood Creek (station 06075775) 462649110554901 08N06E13CCCC01 SF0606B 46°26’48.8” 110°55’49.1” 5,040.70 4.80 4.50 Midstream, T, P 2 South Fork Smith River 4.8 miles below Cottonwood Creek (sta- tion 06075780) 462830110564701 08N06E11BABB02 SF0605 46°28’30.0” 110°56’47.3” 4,991.40 4.65 4.35 Midstream, T, P 3 South Fork Smith River near mouth (station 06075785) 463124110572301 09N06E22DBCD01 SF0601 46°31’23.9” 110°57’22.6” 4,921.10 4.97 4.67 Instream - 2.5 ft from REW, T 3 South Fork Smith River near mouth (station 06075785) 463124110572302 09N06E22DBCD02 SF0602 46°31’24.0” 110°57’22.6” 4,921.60 5.00 4.70 Bank - 2.5 ft from REW, T 3 South Fork Smith River near mouth (station 06075785) 463124110572303 09N06E22DBCD03 SF0603 46°31’23.7” 110°57’22.8” 4,920.76 4.76 4.46 Instream - 2.5 ft from LEW, T, P 3 South Fork Smith River near mouth (station 06075785) 463124110572304 09N06E22DBCD04 SF0604 46°31’23.6” 110°57’22.8” 4,922.46 7.23 6.93 Bank - 2.5 ft from LEW, T 4 North Fork Smith River near mouth (station 06075700) 463210110565101 09N06E14CCBC01 NF0601 46°32’09.6” 110°56’51.0” 4,950.01 5.40 5.10 Bank - 2.5 ft from REW, T 4 North Fork Smith River near mouth (station 06075700) 463210110565102 09N06E14CCBC02 NF0602 46°32’09.6” 110°56’51.0” 4,948.69 4.72 4.42 Instream - 2.5 ft from REW, T, P 4 North Fork Smith River near mouth (station 06075700) 463210110565103 09N06E14CCBC03 NF0603 46°32’09.5” 110°56’50.6” 4,949.26 4.50 4.20 Instream - 2.5 ft from LEW, T

 4 North Fork Smith River near 

mouth (station 06075700)

 463209110565101 09N06E14CCBC04 NF0604 46°32’09.4” 110°56’50.6” 4,950.51 5.74 5.44 Bank - 2.5 ft from 

LEW, T

 5 Smith River below North Fork 

Smith River (station 06075810)

 463207110594801 09N06E17DCDB01 SR0614 46°32’07.3” 110°59’48.5” 4,883.70 6.55 6.25 Bank - 2.5 ft from 

REW, T

 5 Smith River below North Fork 

Smith River (station 06075810)

 463207110594802 09N06E17DCDB02 SR0615 46°32’07.2” 110°59’48.5” 4,882.20 4.85 4.55 Instream - 2.5 ft 

from REW, T

 5 Smith River below North Fork 

Smith River (station 06075810)

 463207110594803 09N06E17DCDB03 SR0616 46°32’07.0” 110°59’48.5” 4,881.50 4.45 4.15 Instream - 2.5 ft 

from LEW, T, P

 5 Smith River below North Fork 

Smith River (station 06075810)

 463207110594804 09N06E17DCDB04 SR0617D 46°32’07.0” 110°59’48.5” 4,881.60 7.40 7.10 Instream - 2.5 ft 

from LEW

 5 Smith River below North Fork 

Smith River (station 06075810)

 463207110594805 09N06E17DCDB05 SR0617 46°32’07.0” 110°59’48.5” 4,884.80 8.40 8.10 Bank - 2.5 ft from 

LEW, T

 6 Smith River at Birch Creek Road 

(station 463257111002801)

 463251111003301 09N06E17BBBD01 SR06B 46°32’51.2” 111°00’33.4” 4,866.30 1.90 1.60 Instream - 2.5 ft 

from REW, T

Table 3. Groundwater and surface-water interaction monitoring sites in the upper Smith River watershed, Montana. [Map number, used for cross reference for locations plotted on figure 8; Station identification number, see “Site-Identification Systems” section for explanation; Site identification number, see “Site-Identification Systems” section for explanation; Station name, see “Site-Identification Systems” section for explanation; Well local identification number, identification number assigned to wells installed for the U.S. Geological Survey groundwater/surface-water interaction monitoring network; Latitude and longitude of well reported in degrees, minutes, seconds, and tenths of seconds referenced to North American Datum of 1983; Altitude of land surface, land-surface altitude, in feet, referenced to North American Vertical datum of 1988; Well depth, depth of well below land surface, in feet; Open interval top, depth of top of open interval below land surface, in feet; Remarks: Midstream, well located near middle of stream; Instream, well located in stream channel; Bank, well located on stream bank; T, instrumented with temperature loggers; P, instrumented with pressure transducer. Abbreviations: ft, feet; LEW, left edge of water; REW, right edge of water]
Study Design and Approach 17

Map 

Number 

(fig. 8)

Location description and station 

identification number of stream

Site identification 

number of well Station name of well

Well local 

identification 

number

Latitude of 

well

Longitude of 

well

Altitude 

of land 

surface 

(feet)

Well 

depth 

(feet)

Open 

interval 

top 

(feet)

Remarks

 7 Smith River below Woods Gulch 

(station 463327111011401)

 463326111011801 09N06E07ACBC01 SR0612 46°33’26.3” 111°01’17.9” 4,849.90 5.00 4.70 Instream - 2.5 ft from 

LEW, T

 7 Smith River below Woods Gulch 

(station 463327111011401)

 463326111011802 09N06E07ACBC02 SR0613 46°33’26.2” 111°01’17.6” 4,849.90 4.40 4.10 Instream - 2.5 ft from 

REW, T

 8 Smith River above Mud Springs 

Creek (station 06075850)

 463414111020201 09N05E01CDDA01 SR0608 46°34’14.2” 111°02’02.4” 4,829.20 6.15 5.85 Bank - 2.5 ft from 

REW, T

 8 Smith River above Mud Springs 

Creek (station 06075850)

 463414111020202 09N05E01CDDA02 SR0609 46°34’14.1” 111°02’02.5” 4,827.70 4.55 4.25 Instream - 2.5 ft from 

REW, T, P

 8 Smith River above Mud Springs 

Creek (station 06075850)

 463414111020203 09N05E01CDDA03 SR0609D 46°34’14.1” 111°02’02.4” 4,827.70 9.46 9.16 Instream - 2.5 ft from 

REW

 8 Smith River above Mud Springs 

Creek (station 06075850)

 463414111020301 09N05E01CDDA04 SR0610 46°34’13.9” 111°02’02.6” 4,827.50 4.15 3.85 Instream - 2.5 ft from 

LEW, T

 8 Smith River above Mud Springs 

Creek (station 06075850)

 463414111020302 09N05E01CDDA05 SR0611 46°34’13.9” 111°02’02.7” 4,829.00 5.65 5.35 Bank - 2.5 ft from 

LEW, T

 9 Smith River below Newlan 

Creek (station 06076560)

 463529111032501 10N05E35AABA01 SR06A 46°35’28.7” 111°03’25.3” 4,791.10 2.15 1.85 Instream - 2.5 ft from 

LEW, T, P

 9 Smith River below Newlan 

Creek (station 06076560)

 463529111032502 10N05E35AABA02 SR0601 46°35’28.9” 111°03’25.1” 4,793.90 6.35 6.05 Bank - 2.5 ft from 

LEW, T

 9 Smith River below Newlan 

Creek (station 06076560)

 463529111032503 10N05E35AABA03 SR0602 46°35’28.9” 111°03’25.1” 4,791.30 4.05 3.75 Instream - 2.5 ft from 

LEW, T

10 Smith River above Rock Springs 

Creek (station 06076580)

 463757111053001 10N05E15BACB01 SR0604 46°37’57.2” 111°05’30.1” 4,680.20 7.60 7.30 Bank - 2.5 ft from 

REW, T

10 Smith River above Rock 

Springs Creek (station 06076580)

 463757111053002 10N05E15BACB02 SR0605 46°37’57.2” 111°05’30.2” 4,677.50 4.70 4.40 Instream - 2.5 ft from 

REW, T, P

10 Smith River above Rock 

Springs Creek (station 06076580)

 463757111053003 10N05E15BACB03 SR0605D 46°37’57.1” 111°05’30.2” 4,677.30 6.35 6.05 Instream - 2.5 ft from 

REW

10 Smith River above Rock 

Springs Creek (station 06076580)

 463757111053101 10N05E15BACB04 SR0606B 46°37’56.9” 111°05’30.6” 4,677.60 4.90 4.50 Instream - 2.5 ft from 

LEW, T

10 Smith River above Rock 

Springs Creek (station 06076580)

 463757111053102 10N05E15BACB05 SR0607 46°37’56.9” 111°05’30.7” 4,679.20 5.50 5.20 Bank - 2.5 ft from 

LEW, T

Table 3. Groundwater and surface-water interaction monitoring sites in the upper Smith River watershed, Montana.—Continued [Map number, used for cross reference for locations plotted on figure 8; Station identification number, see “Site-Identification Systems” section for explanation; Site identification number, see “Site-Identification Systems” section for explanation; Station name, see “Site-Identification Systems” section for explanation; Well local identification number, identification number assigned to wells installed for the U.S. Geological Survey groundwater/surface-water interaction monitoring network; Latitude and longitude of well reported in degrees, minutes, seconds, and tenths of seconds referenced to North American Datum of 1983; Altitude of land surface, land-surface altitude, in feet, referenced to North American Vertical datum of 1988; Well depth, depth of well below land surface, in feet; Open interval top, depth of top of open interval below land surface, in feet; Remarks: Midstream, well located near middle of stream; Instream, well located in stream channel; Bank, well located on stream bank; T, instrumented with temperature loggers; P, instrumented with pressure transducer. Abbreviations: ft, feet; LEW, left edge of water; REW, right edge of water]
18 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed 

N:\Jeff\den12_cmra00_0091_sir_caldwell\figures\figure_08.ai

Camp

Baker

Fourmile Cree

Willow k

Creek

South

Side

Canal

Spring Creek

Eagle Creek

Neihart

White 

Sulphur 

Springs

Smith River

Sheep Creek

Rock Creek

Tenderfoot Creek

Newlan Creek

Beaver Creek

Big Birch Creek

Camas Creek

47°00'

46°30'

46°45'

46°15'

111°15' 111°00' 110°45'

T. 14 N.

T. 13 N.

T. 12 N.

T. 11 N.

T. 10 N.

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

R. 2 E. R. 3 E. R. 4 E. R. 5 E. R. 6 E. R. 7 E. R. 8 E. R. 9 E.

Groundwater and surface-water interaction

 monitorintg site and identifier—Number

 corresponds to Table 3

South Fork Smith River

North

Fork Smith River

0 3 6 MILES

0 3 6 KILOMETERS

Fort

Logan

CASCADE

COUNTY

MEAGHER

COUNTY

BROADWATER

COUNTY

JUDITH

BASIN

COUNTY

89

89

89

12

12

294

Base modified from U.S. Geological Survey digital National

Elevation Dataset, 30 meter, 2006

U.S. Census Bureau TIGER data, 1:100,000, 2000

Lambert Conformal Conic Projection

Standard parallels 45° and 49°, central meridian -109° 30"

North American Datum of 1983 (NAD83). EXPLANATION

Upper Smith River Watershed boundary

1

2

3

5 4

6

7

8

9

10

1

Figure 8. Location of groundwater and surface-water interaction monitoring sites in the upper Smith River 

watershed, Montana.
Study Design and Approach 19

N:\Jeff\den12_cmra00_0091_sir_caldwell\figures\figure_09.ai Altitude, in feet above North American Vertical Datum of 1988

4,879

4,883

4,882

4,887

4,878

4,881

4,885

4,886

4,884

4,889

4,876

4,877

4,888

4,880

staff gage

Right

bank

Well SR0617D

Well SR0616

Smith River

Well SR0617

Well SR0615

Well SR0615

Left bank

Well SR0614

Stream stage May 24, 2007

Groundwater altitudes May 24, 2007

Distance from left bank, in feet

EXPLANATION

Soil Instrument type

Thermistor

Upper instrumentation in

 monitoring well

Pressure transducer

Monitoring well installation

Lower instrumentation in

 monitoring well

Stream instrumentation

Stream instrumentation

Groundwater altitudes—Inferred

 between wells

Monitoring well and identifier—

 Perforated near bottom

Quaternary alluvium—Shallow

 near-streambed sediments

0 5 10 15 20 25 30 35

Figure 9. Channel geometry, monitoring well network, and thermistor and/or pressure transducer locations at the Smith River 

below North Fork Smith River monitoring site (station 06075810). Groundwater altitudes and stream stage for May 24, 2007.
20 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

underlying sediments, and adjacent groundwater (Constantz, 

2008). Whenever a difference in temperature exists between 

two points along a groundwater flow path, heat will be predominantly transported along with the moving groundwater 

(advective heat flow) and to a lesser extent by the conduction 

of heat (conductive heat flow) through the underlying streambed and aquifer material and water trapped between the fine 

sediment (Constantz and Stonestrom, 2003). In the case of a 

gaining stream reach (where groundwater is discharged to the 

stream through the streambed), the upward advection of heat 

due to the higher head in the groundwater is coupled with the 

downward conduction of heat via the streambed sediments 

(fig.10A). This combination of heat transport dampens the 

diurnal and seasonal temperature cycle seen in the stream 

water and attenuates the timing of the peaks and valleys of 

the thermal signal. In a losing stream reach (where surface 

water is discharged to the aquifer through the streambed), heat 

is transported downward by both conduction and advection. 

These two mechanisms of heat transport together create a thermal signal in the groundwater that shows more diel fluctuation 

(fig. 10B) than observed in the groundwater adjacent to a gaining stream reach (fig. 10A).

The method requires continuous stream temperature, 

stream stage, groundwater temperature at multiple depths 

below the streambed, and groundwater levels at the modeled 

streambed cross sections (Eddy-Miller and others, 2009). 

At modeled sites, data loggers recorded continuous (hourly) 

stream stage, groundwater levels in a single well, and temperature in the stream and at two depths in four monitoring wells 

(approximately 1.5 ft and 3.0 ft below the streambed) representing the sediment below the stream. Daily mean groundwater levels at each well within a modeled cross section, derived 

from hourly water levels, were required for model input. In 

order to construct a data set of hourly groundwater levels for 

the wells lacking continuous data, linear regressions were 

developed between the manual groundwater-level measurements of the well with hourly data and each of the other wells. 

These linear relations were used to estimate hourly groundwater levels for the three wells lacking continuous data. The 

hourly groundwater-level, stream-stage, and temperature data 

were then averaged to determine daily mean values.

The hydraulic conductivity of the Quaternary alluvium 

and water flux (flow or exchange) were quantitatively estimated using the two-dimensional groundwater heat and solute 

transport model VS2DH (Healy and Ronan, 1996; Healy, 

2008) and the graphical user interface VS2DI (Hsieh and 

others, 2000). The VS2DH model simulates the (advective 

and conductive) flow of heat through sediments to determine 

the hydraulic conductivity. The general modeling approach 

was similar to Eddy-Miller and others (2009). Models were 

developed for three stream cross sections on the basis of field 

surveys of channel geometry, stream stage, groundwater level, 

and temperature data. Detailed descriptions of the selected 

cross-section models constructed for this study are included in 

appendix 2.

The computer-model simulations were conducted using 

a range of vertical and horizontal conductivity values of the 

Quaternary alluvium, hydraulic conductivity of the unsaturated soil on the stream bank, typical values of porosity, 

dispersivity, heat capacity of the Quaternary alluvium, and 

heat capacity of water based on published values (Freeze and 

Cherry, 1979; Niswonger and Prudic, 2003). When available, 

the cross-section models were developed using data collected 

in a single field season (2007 or 2008). The developed model 

was then run using data from a second season to determine if 

the same parameters would yield output of simulated versus 

observed data within acceptable errors. The results of each 

model simulation were reviewed by comparing observed 

(measured) temperature data with the model results (simulated 

temperature at that location within the model). Hydraulic 

properties were adjusted until the simulated temperature values reasonably matched observed values (the best-fit model).

The flow of water (water flux) across the streambed, 

bottom, and side boundaries of the cross-section models was 

calculated using results of the calibrated 2-D water heat and 

solute transport VS2DH models (app. 3). Water flux calculated 

for each boundary represents the amount of water that flowed 

across the entire length of each boundary over a unit (1-ft) 

width. Modeled results of water-flux output were compared 

with the synoptic streamflow data and records from stagestreamflow relations at several locations.

Surface-Water System

Continuous streamflow monitoring on the Smith River 

and major tributaries allowed for a better understanding of 

the combined influence of tributary contributions, reservoir 

operation, diversions, return flow, and groundwater interaction 

through different parts of the watershed. This study marked 

the first time (water years 2006 through 2010) that four concurrent long-term streamflow-gaging stations were in operation on the Smith River (table 1). In addition, manual streamflow measurements and computed daily streamflow data were 

available for 13 temporary streamflow-gaging stations on the 

Smith River and selected tributaries (table 1) which allowed 

for further spatial definition of the surface-water system.

Streamflow at Long-Term USGS StreamflowGaging Stations

A review of computed daily streamflow at the four longterm USGS streamflow-gaging stations on the Smith River 

showed similar trends with high flows typically occurring 

in the spring to early summer and more stable, moderate to 

low flows occurring from mid-summer through early spring. 

Streamflow typically increased in a downstream direction, primarily due to additional tributary contribution and net groundwater inflow (fig. 11). The most upstream streamflow-gaging 

station on the Smith River, the Smith River below Newlan 
Surface-Water System 21

Figure 10. Streambed flow and heat transport in a gaining and a losing stream; A, Gaining reach. B, Losing reach. 

(Schematics modified from Constantz and Stonestrom, 2003).

N:\Jeff\den12_cmra00_0091_sir_caldwell\figures\figure_10.ai

A. Gaining reach of stream

B. Losing reach of stream

Not to scale

Not to scale

Thermistor

Thermistor

Temperature Temperature Temperature Temperature

Monitoring well Monitoring well

Monitoring well

Monitoring well Monitoring well

Monitoring well

Time

Time

Time

Time
22 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Creek gage (station number 06076560), includes contributions 

from upstream tributaries including the North Fork Smith 

River, South Fork Smith River, Birch Creek, and Newlan 

Creek and is partly regulated by Lake Sutherlin and by 

Newlan Creek Reservoir. The average annual streamflow for 

water years 2005–2010 was 80.9 cubic feet per second (ft3/s) 

with daily streamflow ranging from 17 ft3/s (September 3, 

2007) to 656 ft3/s (June 11, 2010). Another streamflowgaging station with continuous record for water years 2005-

2010, the Smith River below Eagle Creek near Fort Logan 

gage (station number 06077200), is located about 31 mi 

downstream from the Smith River below Newlan Creek gage 

and includes contributions from Camas Creek, Benton Gulch, 

Beaver Creek, Whitetail Creek, Sheep Creek, and Eagle 

Creek. Average annual streamflow was 244 ft3/s (water years 

2005–10) with daily streamflow ranging from 43 ft3/s (August 

31, 2007) to 2,040 ft3/s (June 5, 2010).

A review of streamflow statistics indicated that streamflow conditions during this study (2006–2010) were typical of 

the range of streamflow conditions expected long term. The 

average annual streamflow at Smith River below Eagle Creek 

streamflow-gaging station (station number 06077200), the 

longest continuously operating active streamflow-gaging station on the Smith River, was 224 ft3

/s for the period of record 

(1997–2010). Annual average streamflow was lower than the 

overall average annual streamflow in 2007 (178 ft3/s), was near 

the average in 2006, 2008, and 2009 (217 to 230 ft3/s), and was 

the second highest for the period of record in 2010 (373 ft3/s).

Full-year records (October 1, 2004 through September 

30, 2010) from the uppermost streamflow-gaging station, 

Smith River below Newlan Creek (station 06076560), and 

the streamflow-gaging station below Eagle Creek (station 

06077200), show a mean annual streamflow increase of 

163 ft3/s along this reach (Nilges and Caldwell, 2012). Therefore, the drainage area between the streamflow gaging stations, 

Smith River below Newlan Creek (station 06076560) and 

Smith River below Eagle Creek (station 06077200) contributed about 67 percent of the total streamflow observed at the 

Smith River below Eagle Creek.

Streamflow data collected seasonally at Smith River near 

Fort Logan provide a higher spatial resolution of streamflow 

gains between Smith River below Newlan Creek (station 

06076560) and the streamflow-gaging station below Eagle 

Creek (station 06077200). A median streamflow increase of 

36 ft3/s between the upper two streamflow-gaging stations, 

Smith River below Newlan Creek (80.9 ft3/s) and Smith River 

near Fort Logan (117 ft3/s), was observed when comparing 

data while both streamflow-gaging stations were in operation 

(intermittent periods between October 1, 2006 through October 31, 2010). Camas Creek is the most significant contributor of tributary inflow along this reach. A median streamflow 

increase of nearly 76 ft3/s between the Smith River near Fort 

Logan (117 ft3/s) and the Smith River below Eagle Creek 

(193 ft3/s) was observed when both streamflow-gaging stations 

were in operation (seasonally, 2006 through 2010). Tributary 

inflow from Sheep Creek was responsible for most of the 

increase along this reach. 

Figure 11. Computed daily streamflow at U.S. Geological Survey Smith River streamflow-gaging stations on the Smith River for water 

years 2006 through 2010.

0

500

1,000

1,500

2,000

2,500

3,000

3,500

Streamflow, in cubic feet per second

EXPLANATION

Water Year

Station 06076560 Smith River below Newlan Creek

Station 06076690 Smith River near Fort Logan

Station 06077200 Smith River below Eagle Creek

Station 06077500 Smith River near Eden

2006 2007 2008 2009 2010

N:\Jeff\den12_cmra00_0091_sir_caldwell\figures\figure_11.ai
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 23

Data from the two lower streamflow-gaging stations, 

Smith River below Eagle Creek (station 06077200, continuous 

operation) and the Smith River near Eden (station 06077500, 

seasonal operation), indicated a median streamflow increase 

of 58 ft3/s (23 percent) by comparing data collected while both 

streamflow-gaging stations were in operation between March, 

2006 and October, 2010. Although there are several tributaries 

along this 53.8-mi reach of the Smith River, there were periods 

when streamflow remained nearly identical or even decreased 

between the two stations. These observations could be affected 

by travel times, but are also likely affected by gains and losses 

along this section of the Smith River as it travels through the 

steep-sided limestone canyon.

Streamflow at Temporary USGS StreamflowGaging Stations

Temporary, study-specific, streamflow-gaging stations 

on the Smith River and selected tributaries were operated at 

various times and measurement frequencies (table 1) (fig. 11 

and table 1 in Nilges and Caldwell, 2012). The most complete 

data set was collected during the 2010 water year and allowed 

for a detailed evaluation of computed daily streamflow of the 

Smith River and major tributary inflows in the upper Smith 

River watershed. Although ungaged tributary inflow is likely 

variable and irrigation diversions during parts of the record 

were not measured, the net change in Smith River streamflow between the confluence of the North and South Forks of 

the Smith Rivers and about 10 mi downstream at the Smith 

River below Newlan Creek streamflow-gaging station (station 

06076560) can be generalized for the 2010 record. 

Groundwater and Surface-Water 

Interaction within the Upper Smith 

River Watershed

Similar water table and stream stage elevations combined 

with the significant diversion and application of main stem 

and tributary waters for irrigation supports a complex set of 

groundwater and surface-water interactions within the upper 

Smith River watershed. The interaction between surface water 

and near-stream groundwater can be qualitatively described as 

the direction and relative magnitude of flow based on measured 

groundwater levels, stage, and temperature. Groundwater and 

surface-water monitoring networks (for example, in- and nearstream monitoring wells and staff gages) provided temporal 

information to assess seasonal variations at specific locations.

Interactions are quantitatively described as gains and 

losses during single-day streamflow measurement events 

along several reaches and as simulated water fluxes between 

surface water and groundwater based on flow and heat transport modeling. Modeling of the movement of water and heat 

using temperature and water-level data collected from groundwater and surface-water monitoring networks increased the 

understanding of the hydraulic properties of the Quaternary 

alluvium (streambed and underlying aquifer material) and the 

varying rates of groundwater and surface-water exchange at 

several locations.

Generalized Groundwater Flow Direction and 

Streamflow Gains and Losses

Four large-scale synoptic groundwater-level and streamflow measurements allowed for the evaluation of groundwaterflow directions as well as the location of gaining and losing 

reaches of measured streams and the magnitude of the fluxes. 

Potentiometric-surface maps were constructed with water 

levels measured in approximately 130 wells within 2 weeks 

of each of the synoptic streamflow measurements. Generalized groundwater-flow directions are perpendicular to the 

potentiometric-surface contours from areas of recharge to 

areas of discharge. An understanding of the general direction 

of groundwater flow in the upper watershed at approximately 

the same time as the streamflow measurements (seepage runs) 

was achieved.

Groundwater gains/losses and associated error estimates 

were calculated along five reaches (fig. 6) for each of the 

synoptic events. An attempt was made to quantify all major 

tributary inflows and diversions. However, some small-scale 

tributaries or drains may have inadvertently been omitted. 

Therefore, calculated net gains or losses include groundwater inflow and leakage through the streambed, but may also 

include some small, unmeasured tributaries or diversions. 

This investigation only addressed gains and losses to the main 

stem Smith River and the North and South Forks of the Smith 

River. 

Period of Limited Irrigation (October to April)

Calculated gains and losses from the seepage runs conducted on March 22, 2007; October 16, 2007; and April 10, 

2008, during periods of very limited diversions for irrigation 

or stock use, differed in magnitude, but the direction (gaining 

or losing) of flow between the groundwater and the stream 

a long individual reaches remained the same (table 4). The 

groundwater levels at individual wells measured during these 

seepage runs typically varied less than 5 ft. Three potentiometric-surface maps constructed for these synoptic events are 

similar to one another, with only small differences detected at 

the map scale. A generalized potentiometric-surface map that 

represents groundwater levels measured during these spring 

and fall conditions is shown on figure 12. Groundwater generally followed land-surface topography from the uplands to the 

axis of alluvial valleys of the Smith River and its tributaries. 

Flow to and from the streams was apparent, especially at the 

lower ends of the North and South Forks of the Smith River, 

as well as the upper reach of the main stem Smith River. 
24 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Groundwater gradients ranged from approximately 10 to 50 ft/

mi in the upper Smith River valley.

Summaries of the synoptic streamflow measurements 

taken on March 22, 2007, October 16, 2007, and April 10, 

2008 during periods of limited diversions, and their calculated gains/losses are included in tables 5-7. The South Fork 

Smith River had net gains ranging from 2.44–9.33 ft3/s over 

the lower 14.9-mi reach (reach 1). The lower end of the North 

Fork Smith River had net losses ranging from 2.23–8.49 ft3/s 

over the lower 8.1-mi reach (reach 2). Although tributary 

inflows accounted for most of the net gains of streamflow over 

the upper 41.4 mi (reaches 4 and 5) of the main stem Smith 

River from below the North Fork Smith River to below Eagle 

Creek, groundwater or undocumented tributaries accounted 

for 13.0 to 28.9 ft3/s or 17 to 19 percent of the gains over that 

section of the stream.

Streamflow profiles constructed for periods of limited 

irrigation illustrate the spatial distribution of main-stem 

streamflow due to tributary inflow, inflow from groundwater 

discharge, and losses due to leakage to groundwater. The 

streamflow profiles representing synoptic measurements on 

March 22, 2007, October 16, 2007, and April 10, 2008 were 

generally similar to one another, although magnitudes of 

exchanges between groundwater and surface water differed. 

Instantaneous streamflow measurements on March 22, 2007, 

along the South Fork Smith River, North Fork Smith River, 

and the main stem Smith River are illustrated in figure 13. 

Also shown in figure 13 is the cumulative tributary inflow 

which includes all visible surficial tributary inflow measured 

or calculated along these reaches. Cumulative tributary inflow 

was calculated using the uppermost main-stem streamflow 

value and adding all tributary inflow in the downstream direction. Theoretically, if no gains or losses to or from the groundwater system occur, the main stem and cumulative tributary 

inflow would be equal. When the main stem streamflow profile 

is greater than the cumulative tributary inflow profile, a gain 

in streamflow from a groundwater source is indicated. When 

the cumulative tributary inflow is greater than the main-stem 

streamflow, loss to the groundwater system is indicated. 

The streamflow profile of the South Fork Smith River 

illustrates the initial net loss in streamflow due to leakage to 

groundwater, followed by downstream increases in streamflow 

greater than that accounted for by tributary inflow over the 

next 12 miles with a net gain of nearly 10 ft3/s (fig. 13A). The 

profile of the North Fork Smith River illustrates a net loss up 

to 3.6 ft3/s from below Spring Creek (river mile 8.4) to river 

mile 2.6 as main-stem streamflow falls below the cumulative 

tributary inflow (fig. 13B). The North Fork Smith River gained 

1.4 ft3/s as it traveled downstream between river miles 2.6 and 

0.3. The streamflow profile of the Smith River starting at the 

confluence of the North Fork and South Fork Smith Rivers and 

continuing downstream to the streamflow gaging station below 

Eagle Creek showed the most dramatic increases in streamflow 

from tributary inflow, namely Sheep Creek. Only a gradual 

increase in streamflow attributed to groundwater inflow is 

apparent along this reach on March 22, 2007 (fig. 13C). 

Irrigation Season (May through September)

The August 1, 2007 synoptic measurements represent an 

example of streamflow conditions during the irrigation season 

when snowmelt conditions have long passed and evapotranspiration (Bureau of Reclamation, 2007) is near its peak (table 

8, and fig. 14). Changes in streamflow represent not only 

tributary inflow and gains and losses to and from the groundwater system, but also the effects of reservoir operations 

and numerous irrigation diversions that were not measured. 

Inflows from several tributaries were estimated using upstream 

and downstream main-stem measurements during this exercise. Because of these data limitations, discussions in this 

section are in terms of net increase or decrease of streamflow 

rather than gains or losses through the streambed. Fewer sites 

were measured during this synoptic event in comparison to 

the three measurements during periods of limited diversion. 

Therefore, the stream reaches varied slightly (note: lower 

extents of North and South Forks of the Smith River reaches 

were adjusted slightly upstream).

The August 1, 2007 synoptic measurements generally 

resulted in larger net decreases and smaller net increases in 

streamflow in comparison to the similar reaches measured 

before and after the irrigation season. The South Fork Smith 

River had a net increase in streamflow that was less than 

the estimated errors over the 11.9-mi reach (reach 1). The 

South Fork Smith River was almost dry in the upper section 

(between river miles 15.0 and 11.8) and then transitioned to 

a gaining stream along the lower section. Losses in the upper 

Measurement Date 1Reach 1 net gain (ft3/s) 1Reach 2 net loss (ft3/s) 1Reach 3 net gain (ft3/s) 1Reach 4 net gain (ft3/s) 1Reach 5 net gain (ft3/s)

 3/22/2007 9.33±0.85 -2.23±0.92 2.90±1.98 25.69±7.92 23.2±19.0

10/16/2007 2.44±0.43 -8.49±0.62 4.09±0.94 20.67±3.55 15.3±8.56

 4/10/2008 6.86±1.05 -4.04±0.86 5.31±1.73 24.11±4.47 8.89±6.61

1

River reach shown in figure 6.

2

Calculated gain is less than associated error.

Table 4. Summary of gains and losses calculated from synoptic streamflow measurements during periods of limited diversions, upper 

Smith River watershed, Montana, 2007–2008.

[Abbreviations: ft3/s, cubic feet per second.]
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 25

Figure 12. Generalized potentiometric surface, groundwater-flow direction, and delineation of gaining and losing stream 

reaches during periods of limited diversions, upper Smith River watershed, Montana, 2007–2008. (Based on synoptic 

measurements during March 2007, October 2007, and April 2008).

N:\Jeff\den12_cmra00_0091_sir_caldwell\figures\figure_12.ai

Base modified from U.S. Geological Survey digital National

Elevation Dataset, 30 meter, 2006

U.S. Census Bureau TIGER data, 1:100,000, 2000

Lambert Conformal Conic Projection

Standard parallels 45° and 49°, central meridian -109° 30"

North American Datum of 1983 (NAD83).

0 1 2 3 4 5 MILES

0 1 2 3 4 5 KILOMETERS

R.3 E. R.4 E. R.5 E. R.6 E. R.7 E. R.8 E.

T.7 N.

T.8 N.

T.9 N.

T.10 N.

T.11 N.

T.12 N.

T.13 N.

Upper Smith River Watershed boundary

Eagle Creek

South

Side

Canal

Spring Creek

Fourmile

Creek

North Fork

Smith River

South Fork

Smith River

Smith River

Newlan Creek

Big Birch Creek

Sheep Creek

Camas Creek

Beaver Creek

111°10'

46°50'

Newlan Creek

Reservoir

Gaining Reach Potentiometric contour—Shows altitude at which water would 

 have stood in tightly cased wells generalized from March 2007, 

 October 2007, and April 2008 measurements. Contour intervals

 10 and 50 feet. Datum is North American Vertical Datum of 1988 Extent of stream reach

Unmeasured Reach

General groundwater-flow

 direction

Study well

Losing Reach

EXPLANATION

4,900

4,880

4,860

4,840

4,820

5,000 5,100

4,940

5,150

5,200

5,060

5,100

4,750

4,650

4,700

4,960

4,920

5,200

4,980

5,060

5,050

46°40'

46°30'

111°00' 110°50'

Camp Baker

Fort Logan

White Sulphur

Springs

Willow Creek

89

89

89 12

12

BROADWATER

COUNTY

MEAGHER

COUNTY

5,100

Neutral Reach—Errors larger 

 than calculated gain or loss
Location description Station identification number Time River mile Temp- era- ture (°C) Specific conduc- tance (μS/cm) Main- stem stream- flow (ft3/s) Tributary stream- flow (ft3/s) Streamflow measure- ment rating Estimated measurement error (ft3/s) 

Reach 1 (fig. 6) - South Fork Smith River South Fork Smith River at Birky Road 1.6 miles below Cottonwood Creek 06075775 9:00 15.0 2.5 860 5.28 -- G 0.26 

South Fork Smith River 4.8 miles below Cotton- wood Creek 06075780 8:42 11.8 1.7 814 4.94 -- G 0.25 

Hot Springs Creek at mouth 463057110570301 9:55 4.3 3.0 954 -- 0.88 F 0.07 

Unnamed tributary to South Fork Smith River (number 1) 463107110571401 10:15 3.8 4.2 611 -- 0.43 P 0.04 Unnamed tributary to South Fork Smith River (number 2) 463120110571701 10:50 3.2 3.8 801 -- 0.18 P 0.02 South Fork Smith River near mouth 06075785 11:05 3.1 3.4 747 11.6 -- G 0.58 

South Fork Smith River at mouth 463141110583701 13:30 0.1 6.3 701 16.1 -- G 0.81 

Total (14.9 river miles) Net gain 

Reach 2 (fig. 6) - North Fork Smith River North Fork Smith River above Spring Creek 463327110523701 9:17 8.4 1.3 337 7.06 -- G 0.35 

Spring Creek near mouth 463333110525501 9:50 8.4 4.8 290 -- 9.37 G 0.47 

North Fork Smith River at Highway 360 bridge 463256110545201 11:00 5.3 3.3 330 15.2 -- G 0.76 

North Fork Smith River near mouth 06075700 12:00 2.6 4.3 341 12.8 -- F 1.02 

North Fork Smith River at mouth 463148110583001 12:55 0.3 5.5 337 14.2 -- G 0.71 

Total (8.1 river miles) Net Loss 

Reach 3 (fig. 6) - Upper Smith River below confluence of North and South Forks of Smith River 

South Fork Smith River at mouth 463141110583701 13:30 124.8 6.3 701 16.1 -- G 0.81 North Fork Smith River at mouth 463148110583001 12:55 124.7 5.5 337 14.2 -- G 0.71 Smith River below North Fork Smith River 06075810 14:40 122.2 6.4 549 33.2 -- G 1.66 Total (2.6 river miles) Net gain 

Table 5. Estimated stre

[Station identification numbering: (G) good (less than 5 permens per centimeter at 25 de

amflow gains and losses, upper Smith River Watershed, Montana, March 22, 2007.

, see “Site-Identification Systems” section for explanation; River mile, distance above mouth; Temperature, water temperature in degrees Celsius

cent measurement error), (F) fair (5 to 8 percent measurement error), (P) poor (greater than 8 percent measurement error). Abbreviations: °C, degr

grees Celsius; ft3/s, cubic feet per second. Symbols: --, not applicable or not measured. Note: main-stem values in bold type]
Location description

Station 

identification 

number

Time River mile Temp- erature (°C) Specific conduc- tance (μS/cm) Main- stem stream- flow (ft3/s) Tributary stream- flow (ft3/s) Streamflow measure- ment rating Estimated measurement error (ft3/s) 

Reach 4 (fig. 6) - Smith River between below North Fork Smith River and the USGS Gage 06076560 below Newlan Creek

Smith River below North Fork Smith River 06075810 14:40 122.2 6.4 549 33.2 -- G 1.66 Smith River above unnammed tributary 463241111001801 9:40 120.8 2.6 559 35.2 -- F 2.82 Unnamed tributary at mouth 0.5 miles above Birch 

Creek Road

463240111001501 9:45 120.7 4.2 471 -- 1.25 F 0.10 

Ditch at mouth on south side of Birch Creek Road 463253111002901 9:45 120.3 1.3 470 -- 0.75 F 0.06 Ditch at mouth on north side of Birch Creek Road 463255111002801 9:58 120.2 2.8 439 -- .68 F 0.05 Woods Gulch at mouth 463313111010501 11:15 119.1 4.2 503 -- 1.61 F 0.13 Ditch at mouth below Woods Gulch 463330111011201 12:50 118.4 6.1 480 -- 3.33 F 0.27 Ditch at mouth above Mud Springs Creek (number 1) 463413111014701 14:20 117.1 6.3 515 -- 1.91 F 0.15 Ditch at mouth above Mud Springs Creek (number 2) 463355111013901 14:55 116.3 7.2 495 -- 1.25 F 0.10 Smith River above Mud Springs Creek 06075850 14:00 116.0 5.2 541 46.7 -- F 3.74 1Mud Springs Creek (calculated) -- -- 115.3 -- -- -- 2.10 -- 5.40 Smith River below Mud Springs Creek 463437111021701 15:50 115.2 6.6 536 48.8 -- F 3.90 Smith River above Big Birch Creek 463518111030101 9:20 112.7 2.9 542 51.6 -- F 4.13 Big Birch Creek at mouth 06075900 10:20 112.6 1.9 238 -- 11.1 G 0.56 Newlan Creek at mouth 06076550 11:15 112.4 2.5 481 -- 5.93 G 0.30 Smith River below Newlan Creek 06076560 13:40 112.1 4.1 490 68.8 -- F 5.50 Total (10.1 river miles) 2Net gain 

Reach 5 (fig. 6) - Smith River below Newlan Creek to Smith River below Eagle Creek

Smith River below Newlan Creek 06076560 13:40 112.1 4.1 490 68.8 -- F 5.50 Smith River above Thompson Gulch 463636111050701 15:35 108.2 6.1 487 68.0 -- G 3.40 Thompson Gulch near mouth 463638111051801 11:05 108.1 5.5 345 -- 1.35 F 0.11 Spring Creek at Highway 360 bridge 463743111042701 12:10 106.5 5.1 476 -- 0.65 F 0.05 Smith River above Rock Springs Creek 06076580 12:35 105.1 4.7 473 71.3 -- G 3.57 Smith River below Rock Springs Creek 463911111055501 13:36 103.1 4.8 473 73.8 -- G 3.69 Smith River at Highway 360 bridge 464033111083501 11:00 98.4 3.3 461 76.9 -- F 6.15 

Table 5. Estimated streamflow gains and losses, upper Smith River Watershed, Montana, March 22, 2007.—Continued

[Station identification number, see “Site-Identification Systems” section for explanation; River mile, distance above mouth; Temperature, water temperature in degrees Celsiusing: (G) good (less than 5 percent measurement error), (F) fair (5 to 8 percent measurement error), (P) poor (greater than 8 percent measurement error). Abbreviations: °C, degrmens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second. Symbols: --, not applicable or not measured. Note: main-stem values in bold type]
28 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed Location description Station identification number Time River mile Temp- erature (°C) Specific conduc- tance (μS/cm) Main- stem stream- flow (ft3/s) Tributary stream- flow (ft3/s) Stream- flow measure- ment rating Estimated measurement error (ft3/s) Estimated streamflow gain (+) or loss (-) and associated measurement error (ft3/s) Reach 5 (fig. 6) - Smith River below Newlan Creek to Smith River below Eagle Creek—Continued Unnamed tributary to Smith River at mouth near Fort Logan 464034111092001 12:30 97.8 5.4 404 -- 3.13

G 0.16 --

Unnamed tributary to Smith River from Soldiers 

Lake

464043111100801 11:53 96.8 5.3 331 -- 1.83

G 0.09 --

Smith River above Camas Creek 464218111113501 10:00 94.3 2.8 475 87.2 -- F 6.98 5.34 ± 9.30Camas Creek at mouth 06076600 -- 94.2 -- -- -- -- -- -- --Benton Gulch at mouth 06076650 -- 94.1 -- -- -- -- -- -- --1Camas Creek and Benton Gulch (calculated) -- -- -- -- -- -- 7.30 10.29 --Smith River below Benton Gulch 464222111113201 11:00 94.0 -- 471 94.5 -- F 7.56 --1Beaver Creek and Whitetail Creek (calculated) -- -- -- -- -- -- 15.5 -- 9.35 --Smith River below Beaver Creek 464550111094601 12:55 88.1 4.3 468 110 --

G 5.50 --

Smith River near Fort Logan 06076690 14:15 83.6 4.8 477 115 --

G 5.75 5.00 ± 7.96

Sheep Creek at mouth 464816111110001 16:05 82.7 2.8 202 -- 70.9 F 5.67 --Eagle Creek near mouth 464942111095101 17:05 81.4 2.4 256 -- 11.3 F 0.90 --Smith River below Eagle Creek 06077200 13:52 80.8 4.2 366 204 --

G 10.20 6.80 ± 13.0

Total (31.3 river miles) Net gain 23.2 ± 19.0

Upper Smith River (from Smith River below North Fork Smith River to Smith River below Eagle Creek)

Total (41.4 river miles) Total Tributary inflow 142 Net gain 28.9 ± 19.0

1Tributary value calculated as the difference between upstream and downstream main-stem measurements. 2Calculated gain less than associated measurement errors.

Table 5. Estimated streamflow gains and losses, upper Smith River Watershed, Montana, March 22, 2007.—Continued

[Station identification number, see “Site-Identification Systems” section for explanation; River mile, distance above mouth; Temperature, water temperature in degrees Celsius; Streamflow measurement rating: (G) good (less than 5 percent measurement error), (F) fair (5 to 8 percent measurement error), (P) poor (greater than 8 percent measurement error). Abbreviations: °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second. Symbols: --, not applicable or not measured. Note: main-stem values in bold type]
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 29

Location description

Station 

identification 

number

Time River mile Temperature (°C)

Specific 

conductance 

(μS/cm)

Main-stem 

streamflow (ft3/s)

Tributary 

streamflow 

(ft3/s)

Streamflow 

measurement rating

Estimated 

measurement 

error (ft3/s)

Estimated streamflow 

gain (+) or loss (-) and 

associated measurement error (ft3/s)

Reach 1 (fig. 6) - South Fork Smith River

South Fork Smith River at Birky Road 1.6 miles 

below Cottonwood Creek

 06075775 8:55 15.0 -- -- 3.08 --

G 0.15 --

South Fork Smith River 4.8 miles below Cottonwood Creek 06075780 10:04 11.8 3.0 931 0.16 -- P 0.02 -2.92 ± 0.15Hot Springs Creek at mouth 463057110570301 9:46 4.3 5.9 1,045 -- 1.34 F 0.11 --Unnamed tributary to South Fork Smith River 

(number 1)

463107110571401 10:17 3.8 7.3 612 -- 0.50 F 0.04 --

Unnamed tributary to South Fork Smith River 

(number 2)

463120110571701 11:08 3.2 5.7 892 -- 0.31 P 0.02 --

South Fork Smith River near mouth 06075785 10:53 3.1 5.6 786 5.28 --

G 0.26 2.97 ± 0.29

South Fork Smith River at mouth 463141110583701 15:39 0.1 10.7 670 7.67 --

G 0.38 2.39 ± 0.47

Total (14.9 river miles) Net gain 2.44 ± 0.43

Reach 2 (fig. 6) - North Fork Smith River

North Fork Smith River above Spring Creek 463327110523701 10:15 8.4 6.8 400 2.53 -- F 0.20 --Spring Creek near mouth 463333110525501 11:15 8.4 9.2 265 -- 10.7

G 0.54 --

North Fork Smith River at Highway 360 bridge 463256110545201 12:35 5.3 7.5 320 13.2 --

G 0.66 -0.03 ± 0.87

North Fork Smith River near mouth 06075700 13:40 2.6 8.6 336 5.23 -- F 0.42 -7.97 ± 0.78North Fork Smith River at mouth 463148110583001 14:45 0.3 11.0 392 4.74 --

G 0.24 -0.49 ± 0.48

Total (8.1 river miles) Net loss -8.49 ± 0.62

Reach 3 (fig. 6) - Upper Smith River below confluence of North and South Forks of Smith River 

South Fork Smith River at mouth 463141110583701 15:39 124.8 10.7 670 7.67 --

G 0.38 --

North Fork Smith River at mouth 463148110583001 14:45 124.7 11.0 392 4.74 --

G 0.24 --

Smith River below North Fork Smith River 06075810 12:04 122.2 8.7 590 16.50 --

G 0.83 --

Total (2.6 river miles) Net gain 4.09 ± 0.94

Reach 4 (fig. 6) - Smith River between below North Fork Smith River and at USGS Gage 06076560 below Newlan Creek

Smith River below North Fork Smith River 06075810 12:04 122.2 8.7 590 16.5 --

G 0.83 --

Unnamed tributary at mouth 0.5 miles above Birch 

Creek Road

463240111001501 9:15 120.7 5.6 483 -- 0.94 F 0.08 --

Ditch at mouth on south side of Birch Creek Road 463253111002901 9:02 120.3 -- 527 -- 0.51 P 0.05 --

Table 6. Estimated streamflow gains and losses, upper Smith River Watershed, Montana, October 16, 2007.[Station identification number, see “Site-Identification Systems” section for explanation; River mile, distance above mouth; Temperature, water temperature in degrees Celsius; Streamflow measurement rating: (G) good (less than 5 percent measurement error), (F) fair (5 to 8 percent measurement error), (P) poor (greater than 8 percent measurement error). Abbreviations: °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second. Symbols: --, not applicable or not measured. Note: main-stem values in bold type]
30 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed Location description Station identification number Time River mile Temperature (°C) Specific conduc- tance (μS/cm) Main-stem stream- flow (ft3/s) Tributary stream- flow (ft3/s) Streamflow measure- ment rating Estimated measurement error (ft3/s) Estimated streamflow gain (+) or loss (-) and associated measure- ment error (ft3/s) Reach 4 (fig. 6) - Smith River between below North Fork Smith River and at USGS Gage 06076560 below Newlan Creek—Continued Ditch at mouth on north side of Birch Creek Road 463255111002801 9:25 120.2 -- 489 -- 0.44 P 0.04 -- Woods Gulch at mouth 463313111010501 10:22 119.1 -- 752 -- 0.42 P 0.04 -- Smith River below Woods Gulch 463327111011401 10:20 118.8 5.7 596 20.3 --

G 1.02 1.49 ± 1.31

Ditch at mouth below Woods Gulch 463330111011201 11:35 118.4 7.0 498 -- 2.49 P 0.25 --Ditch at mouth above Mud Springs Creek (number 1) 463413111014701 13:40 117.1 7.6 541 -- 1.76 F 0.14 --Ditch at mouth above Mud Springs Creek (number 2) 463355111013901 13:15 116.3 8.8 501 -- 0.70 F 0.06 --Smith River above Mud Springs Creek 06075850 12:05 116.0 7.0 570 25.5 --

G 1.28 0.25 ± 1.66

1Mud Springs Creek (calculated) -- -- 115.3 -- -- -- 2.60 -- 1.90 --Smith River below Mud Springs Creek 463437111021701 14:45 115.2 9.6 556 28.1 --

G 1.41 --

Big Birch Creek at mouth 06075900 9:45 112.6 3.5 272 -- 5.78

G 0.29 --

Newlan Creek at mouth 06076550 11:00 112.4 -- -- -- 2.69 F 0.22 --Smith River below Newlan Creek 06076560 9:15 112.1 5.0 467 35.5 -- F 2.84 -1.07 ± 3.19Total (10.1 river miles) 2Net gain 0.67 ± 3.55

Reach 5 (fig. 6) - Smith River below Newlan Creek to Smith River below Eagle Creek

Smith River below Newlan Creek 06076560 9:15 112.1 5.0 467 35.5 -- F 2.84 --Thompson Gulch near mouth 463638111051801 13:45 108.1 6.4 359 -- 1.31

G 0.07 --

Spring Creek at Highway 360 bridge 463743111042701 11:18 106.5 -- 503 -- 0.56 P 0.06 --Smith River above Rock Springs Creek 06076580 13:35 105.1 8.0 482 40.5 --

G 2.03 3.13 ± 3.49

Smith River below Rock Springs Creek 463911111055501 12:48 103.1 7.4 490 38.3 --

G 1.92 2.20 ± 2.79

Smith River at Highway 360 bridge 464033111083501 15:25 98.4 9.0 475 38.6 --

G 1.93 0.30 ± 2.72

Unnamed tributary to Smith River at mouth near Fort 

Logan

464034111092001 12:00 97.8 -- 419 -- 4.03 F 0.32 --

Unnamed tributary to Smith River from Soldiers 

Lake

464043111100801 12:28 96.8 -- 342 -- 1.81 P 0.18 --

Smith River above Camas Creek 464218111113501 10:30 94.3 6.2 475 45.7 --

G 2.29 1.26 ± 3.01

!Camas Creek and Benton Gulch (calculated) -- -- -- -- -- -- 12.6 3.70 --Smith River below Benton Gulch 464222111113201 11:30 94.0 7.2 475 58.3 --

G 2.92 --

Table 6. Estimated streamflow gains and losses, upper Smith River Watershed, Montana, October 16, 2007.—Continued

[Station identification number, see “Site-Identification Systems” section for explanation; River mile, distance above mouth; Temperature, water temperature in degrees Celsius; Streamflow measurement 

rating: (G) good (less than 5 percent measurement error), (F) fair (5 to 8 percent measurement error), (P) poor (greater than 8 percent measurement error). Abbreviations: °C, degrees Celsius; μS/cm, 

microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second. Symbols: --, not applicable or not measured. Note: main-stem values in bold type]
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 31 Location description Station identification number Time River mile Temperature (°C) Specific conduc- tance (μS/cm) Main-stem stream- flow (ft3/s) Tributary stream- flow (ft3/s) Streamflow measure- ment rating Estimated measurement error (ft3/s) Estimated streamflow gain (+) or loss (-) and associated measure- ment error (ft3/s) Reach 5 (fig. 6) - Smith River below Newlan Creek to Smith River below Eagle Creek—Continued

1Beaver Creek and Whitetail Creek (calculated) -- -- -- -- -- -- 0.90 -- 4.15 --Smith River below Beaver Creek 464550111094601 13:25 88.1 8.1 485 59.2 --

G 2.96 --

Smith River near Fort Logan (calculated 

from gage)

 06076690 15:00 83.6 -- -- 58.0 --

G 2.90 -1.20 ± 4.14

Sheep Creek at mouth 464816111110001 15:35 82.7 8.0 280 -- 24.7

G 1.24 --

Eagle Creek near mouth 464942111095101 16:40 81.4 7.6 380 -- 3.25

G 0.16 --

Smith River below Eagle Creek (calculated 

from gage)

 06077200 15:00 80.8 -- -- 100 --

G 5.00 14.1 ± 5.91

Total (31.3 river miles) Net gain 15.3 ± 8.56

Upper Smith River (from Smith River below North Fork Smith River to Smith River below Eagle Creek)

Total (41.4 river miles) Total tributary inflow 67.5 Net gain 16.0 ± 7.89

1Tributary value calculated as the difference between upstream and downstream main-stem measurements2Calculated gain less than associated measurement errors.

Table 6. Estimated streamflow gains and losses, upper Smith River Watershed, Montana, October 16, 2007.—Continued[Station identification number, see “Site-Identification Systems” section for explanation; River mile, distance above mouth; Temperature, water temperature in degrees Celsius; Streamflow measurement rating: (G) good (less than 5 percent measurement error), (F) fair (5 to 8 percent measurement error), (P) poor (greater than 8 percent measurement error). Abbreviations: °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second. Symbols: --, not applicable or not measured. Note: main-stem values in bold type]
32 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed Location description Station identification number Time River mile Temperature (°C) Specific conduc- tance (μS/cm) Main-stem streamflow (ft3/s) Tributary stream- flow (ft3/s) Streamflow measure- ment rating Estimated measurement error (ft3/s) Estimated streamflow gain (+) or loss (-) and associated measurement error (ft3/s) Reach 1 (fig. 6) - South Fork Smith River South Fork Smith River at Birky Road 1.6 miles below Cottonwood Creek 06075775 9:00 15.0 3.3 886 4.43 --

G 0.22 -- 

South Fork Smith River 4.8 miles below 

Cottonwood Creek

 06075780 10:00 11.8 1.8 746 5.04 -- F 0.40 0.61 ± 0.46

Hot Springs Creek at mouth 463057110570301 10:15 4.3 2.2 916 -- 0.91 F 0.07 --Unnamed tributary to South Fork Smith 

River (number 1)

463107110571401 11:10 3.8 6.0 627 -- 0.38 P 0.04 --

Unnamed tributary to South Fork Smith 

River (number 2)

463120110571701 11:50 3.2 4.3 829 -- 0.22 P 0.02 --

South Fork Smith River near mouth 06075785 11:15 3.1 3.3 755 10.2 --

G 0.51 3.65 ± 0.66

South Fork Smith River at mouth 463141110583701 12:55 0.1 5.5 694 12.8 -- F 1.02 2.60 ± 1.14Total (14.9 river miles) Net gain 6.86 ± 1.05

Reach 2 (fig. 6) - North Fork Smith River

North Fork Smith River above Spring 

Creek

463327110523701 9:20 8.4 1.0 360 3.88 -- F 0.31 --

Spring Creek near mouth 463333110525501 10:00 8.4 5.2 286 -- 8.55 F 0.68 --North Fork Smith River at Highway 360 

bridge

463256110545201 11:15 5.3 2.5 325 14.2 --

G 0.71 1.77 ± 1.03

North Fork Smith River near mouth 06075700 12:15 2.6 4.0 332 8.87 --

G 0.44 -5.33 ± 0.84

North Fork Smith River at mouth 463148110583001 13:45 0.3 5.7 417 8.39 --

G 0.42 -0.48 ± 0.61

Total (8.1 river miles) Net loss -4.04 ± 0.86

Reach 3 (fig. 6) - Upper Smith River below confluence of North and South Forks of Smith River 

South Fork Smith River near mouth 463141110583701 12:55 124.8 5.5 694 12.8 -- F 1.02 --North Fork Smith River at mouth 463148110583001 13:45 124.7 5.7 417 8.39 --

G 0.42 --

Smith River below North Fork Smith 

River

 06075810 13:20 122.2 4.8 536 26.5 --

G 1.33 --

Total (2.6 river miles) Net gain 5.31 ± 1.73

Reach 4 (fig. 6) - Smith River between below North Fork Smith River and at USGS Gage 06076560 below Newlan Creek

Smith River below North Fork Smith 

River

 06075810 13:20 122.2 4.8 536 26.5 --

G 1.33 --

Table 7. Estimated streamflow gains and losses, upper Smith River watershed, Montana, April 10, 2008.[Station identification number, see “Site-Identification Systems” section for explanation; River mile, distance above mouth; Temperature, water temperature in degrees Celsius; Streamflow measurement rating: (G) good (less than 5 percent measurement error), (F) fair (5 to 8 percent measurement error), (P) poor (greater than 8 percent measurement error). Abbreviations: °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second. Symbols: --, not applicable or not measured. Note: main-stem values in bold type]
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 33

Location description

Station 

identification 

number

Time River mile Temperature (°C)

Specific 

conductance 

(μS/cm)

Main-stem 

streamflow 

(ft3/s)

Tributary 

streamflow (ft3/s)

Streamflow 

measurement rating

Estimated 

measurement 

error (ft3/s)

Estimated streamflow gain 

(+) or loss (-) and associated 

measurement error (ft3/s)

Reach 4 (fig. 6) - Smith River between blw North Fork Smith River and at USGS Gage 06076560 below Newlan Creek—Continued

Unnamed tributary at mouth 0.5 miles above 

Birch Creek Road

463240111001501 10:25 120.7 6.7 470 -- 1.22 P 0.12 --

Ditch at mouth on south side of Birch Creek 

Road

463253111002901 9:15 120.3 1.0 471 -- 0.42 P 0.04 --

Ditch at mouth on north side of Birch Creek 

Road

463255111002801 9:45 120.2 2.7 474 -- 0.62 P 0.06 --

Woods Gulch at mouth 463313111010501 10:50 119.1 3.6 526 -- 1.76 P 0.18 --Smith River below Woods Gulch 463327111011401 9:40 118.8 3.6 528 29.8 --

G 1.49 -0.72 ± 2.01

Ditch at mouth below Woods Gulch 463330111011201 10:20 118.4 5.6 526 -- 2.85 F 0.23 --Ditch at mouth above Mud Springs Creek 

(number 1)

463413111014701 12:10 117.1 6.0 519 -- 2.12 F 0.17 --

Ditch at mouth above Mud Springs Creek 

(number 2)

463355111013901 12:40 116.3 5.9 519 -- 1.42 F 0.11 --

Smith River above Mud Springs Creek 06075850 12:15 116.0 5.3 518 39.9 --

G 2.00 3.71 ± 2.51

Mud Springs Creek (unable to calculate from 

main-stem measurements)

 -- -- 115.3 -- -- -- -- -- -- --

Smith River below Mud Springs Creek 463437111021701 12:55 115.2 5.7 518 -- -- -- -- --Big Birch Creek at mouth 06075900 9:15 112.6 1.5 278 -- 7.04

G 0.35 --

Newlan Creek at mouth 06076550 9:15 112.4 2.0 253 -- 4.74 F 0.38 --Smith River below Newlan Creek 06076560 13:40 112.1 5.5 481 52.8 -- F 4.22 1.12 ± 4.70Total (10.1 river miles) 1Net gain 4.11 ± 4.47

Reach 5 (fig. 6) - Smith River below Newlan Creek to Smith River below Eagle Creek

Smith River below Newlan Creek 06076560 13:40 112.1 5.5 481 52.8 -- F 4.22 --Thompson Gulch near mouth 463638111051801 11:15 108.1 2.5 349 -- 1.12 P 4.22 --Spring Creek at Highway 360 bridge 463743111042701 11:50 106.5 7.8 499 -- 0.33 P 0.03 --Smith River above Rock Springs Creek 06076580 9:05 105.1 2.9 480 54.4 --

G 2.72 0.15 ± 5.03

Smith River below Rock Springs Creek 463911111055501 10:15 103.1 3.4 482 57.1 --

G 2.86 2.70 ± 3.94

Smith River at Highway 360 bridge 464033111083501 11:30 98.4 4.8 483 61.0 --

G 3.05 3.90 ± 4.18

Table 7. Estimated streamflow gains and losses, upper Smith River watershed, Montana, April 10, 2008.—Continued[Station identification number, see “Site-Identification Systems” section for explanation; River mile, distance above mouth; Temperature, water temperature in degrees Celsius; Streamflow measurement rating: (G) good (less than 5 percent measurement error), (F) fair (5 to 8 percent measurement error), (P) poor (greater than 8 percent measurement error). Abbreviations: °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second. Symbols: --, not applicable or not measured. Note: main-stem values in bold type]
34 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed Location description Station identification number Time River mile Temperature (°C) Specific conduc- tance (μS/cm) Main-stem streamflow (ft3/s) Tributary stream- flow (ft3/s) Streamflow measure- ment rating Estimated measurement error (ft3/s) Estimated streamflow gain (+) or loss (-) and associated measurement error (ft3/s) Reach 5 (fig. 6) - Smith River below Newlan Creek to Smith River below Eagle Creek—Continued Unnamed tributary to Smith River at mouth near Fort Logan 464034111092001 13:00 97.8 5.7 414 -- 2.86 F 0.23 -- Unnamed tributary to Smith River from Soldiers Lake 464043111100801 13:45 96.8 7.0 440 -- 1.75 F 0.14 -- Smith River above Camas Creek 464218111113501 10:15 94.3 3.4 465 60.8 --

G 3.04 -4.81 ± 4.31

Camas Creek at mouth 06076600 11:00 94.2 2.7 405 -- 4.19 F 0.34 --Benton Gulch at mouth 06076650 11:40 94.1 5.4 630 -- 3.79 P 0.38 --Smith River below Benton Gulch 464222111113201 12:15 94.0 6.2 470 69.3 --

G 3.47 0.52 ± 4.61

Smith River near Fort Logan 06076690 12:45 83.6 5.5 481 70.1 --

G 3.51 0.80 ± 4.93

Sheep Creek at mouth 464816111110001 14:20 82.7 3.0 255 -- 19.9

G 1.00 --

Eagle Creek near mouth 464942111095101 11:10 81.4 0.7 360 -- 3.27 F 0.26 --Smith River below Eagle Creek 06077200 10:15 80.8 3.0 430 98.9 --

G 4.95 5.63 ± 6.15

Total (31.3 river miles) Net gain 8.89 ± 6.61

Upper Smith River (from Smith River below North Fork Smith River to Smith River below Eagle Creek)

Total (41.4 river miles) Total tributary inflow 59.4 Net gain 13.0 ± 5.291Calculated gain less than associated measurement errors.

Table 7. Estimated streamflow gains and losses, upper Smith River watershed, Montana, April 10, 2008.—Continued[Station identification number, see “Site-Identification Systems” section for explanation; River mile, distance above mouth; Temperature, water temperature in degrees Celsius; Streamflow measurement rating: (G) good (less than 5 percent measurement error), (F) fair (5 to 8 percent measurement error), (P) poor (greater than 8 percent measurement error). Abbreviations: °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second. Symbols: --, not applicable or not measured. Note: main-stem values in bold type]
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 35

Figure 13. Instantaneous streamflow and cumulative tributary inflow of the A, South Fork Smith River; B, North Fork Smith River; 

and C, upper Smith River, Montana, March 22, 2007.

N:\Jeff\den12_cmra00_0091_sir_caldwell\figures\figure_13.ai

0

20

250

15

2

4

6

8

10

12

14

16

18

16 14 12 10 8 6 4 2 0

Streamflow, in cubic feet per second 

River mile above confluence

A. South Fork Smith River

B. North Fork Smith River

C. Upper Smith River

EXPLANATION

10

5

0

200

150

100

50

0

9 8

130 120 110 100 90 80

7 6 5 4 3 2 1 0

Main stem South Fork Smith River

Cumulative tributary inflow

EXPLANATION

Main stem Smith River

Cumulative tributary inflow

EXPLANATION

Main stem North Fork Smith River

Cumulative tributary inflow

Contribution from Spring Creek

North Fork and South

Fork Smith Rivers

Big Birch and

Newlan Creeks

Sheep and

Eagle Creeks

Net Gain

Net Loss
36 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed Location description Station identification number Time River mile Temperature (°C) Specific conduc- tance (μS/cm) Main-stem streamflow (ft3/s) Tributary streamflow (ft3/s) Streamflow measure- ment rating Estimated measurement error (ft3/s) Estimated streamflow gain (+) or loss (-) and associated measurement error (ft3/s) Reach 1 (fig. 6) - South Fork Smith River (note lower extent adjusted upstream compared to figure 6) South Fork Smith River at Birky Road 1.6 miles below Cottonwood Creek 06075775 9:52 15.0 16.1 480 1.59 -- F 0.13 -- South Fork Smith River 4.8 miles below Cottonwood Creek 06075780 11:00 11.8 15.4 449 0.27 -- P 0.03 -1.32 ± 0.13 Hot Springs Creek at mouth 463057110570301 9:58 4.3 16.3 436 -- 1.13 P 0.11 -- Unnamed tributary to South Fork Smith River (number 1) 463107110571401 10:40 3.8 11.5 595 -- 0.20 P 0.02 -- Unnamed tributary to South Fork Smith River (number 2) 463120110571701 9:14 3.2 8.5 759 -- 0.06 P 0.01 -- South Fork Smith River near mouth 06075785 12:20 3.1 15.6 553 3.11 -- P 0.31 1.45 ± 0.33 Total (11.9 river miles) 1Net gain 0.13 ± 0.36 Reach 2 (fig. 6) - North Fork Smith River (note lower extent adjusted upstream compared to figure 6) North Fork Smith River above Spring Creek 463327110523701 9:10 8.4 14.2 363 61.9 --

G 3.10 --

Spring Creek near mouth 463333110525501 10:00 8.4 11.9 307 -- 10.6

G 0.53 --

North Fork Smith River at highway 360 

bridge

463256110545201 11:10 5.3 16.1 351 13.7 -- F 1.10 -58.8 ± 3.33

North Fork Smith River near mouth 06075700 9:15 2.6 15.5 398 4.86 -- F 0.39 -8.84 ± 1.16Total (5.8 river miles) Net loss -67.6 ± 3.16

Reach 3 (fig. 6) - Upper Smith River below confluence of North and South Forks of Smith River (note upper extent adjusted upstream compared to figure 6) 

South Fork Smith River near mouth 06075785 12:20 3.1 15.6 553 3.11 -- P 0.31 --North Fork Smith River near mouth 06075700 9:15 2.6 15.5 398 4.86 -- F 0.39 --Smith River below North Fork Smith 

River

 06075810 11:23 122.2 19.3 452 13.1 --

G 0.66 --

Total (6.9 river miles with includes lower reaches of North Fork Smith River and South Fork Smith River) Net gain 5.13 ± 0.82

Reach 4 (fig. 6)- Smith River between below North Fork Smith River and at USGS Gage 06076560 below Newlan Creek (fig. 6)

Smith River below North Fork Smith 

River

 06075810 11:23 122.2 19.3 452 13.1 --

G 0.66 --

Unnamed tributary at mouth 0.5 miles above 

Birch Creek Road

463240111001501 8:36 120.7 -- -- -- 0.08 F 0.01 --

Table 8. Estimated streamflow gains and losses, upper Smith River watershed, Montana, August 1, 2007.

[Station identification number, see “Site-Identification Systems” section for explanation; River mile, distance above mouth; Temperature, water temperature in degrees Celsius; Streamflow measurement rating: (G) good (less than 5 percent measurement error), (F) fair (5 to 8 percent measurement error), (P) poor (greater than 8 percent measurement error). Abbreviations: °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second. Symbols: --, not applicable or not measured. Note: main-stem values in bold type]
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 37

Location description

Station 

identification 

number

Time River mile Temperature (°C)

Specific 

conductance 

(μS/cm)

Main-stem 

streamflow 

(ft3/s)

Tributary 

streamflow 

(ft3/s)

Streamflow 

measurement rating

Estimated 

measurement 

error (ft3/s)

Estimated streamflow gain 

(+) or loss (-) and associated 

measurement error (ft3/s)

Reach 4 (fig. 6)- Smith River between below North Fork Smith River and at USGS Gage 06076560 below Newlan Creek (fig. 6)—Continued

Ditch at mouth on south side of Birch Creek 

Road

463253111002901 9:00 120.3 14.3 458 -- 0.19 P 0.02 --

Ditch at mouth on north side of Birch Creek 

Road

463255111002801 9:20 120.2 10.1 423 -- 0.20 F 0.02 --

Woods Gulch at mouth 463313111010501 9:57 119.1 12.3 663 -- 0.20 F 0.02 --Smith River below Woods Gulch 463327111011401 11:00 118.8 17.0 479 10.8 --

G 0.54 -2.97 ± 0.85

Ditch at mouth below Woods Gulch 463330111011201 -- 118.4 -- -- -- -- -- -- --Ditch at mouth above Mud Springs Creek 

(number 1)

463413111014701 -- 117.1 -- -- -- -- -- -- --

Ditch at mouth above Mud Springs Creek 

(number 2)

463355111013901 -- 116.3 -- -- -- -- -- -- --

2Tributary inflows (calculated) -- -- -- -- -- 3.50 0.90 --Smith River above Mud Springs Creek 06075850 12:40 116.0 18.4 470 14.3 --

G 0.72 --

2Mud Springs Creek (calculated) -- -- 115.3 -- -- -- 0.30 -- 1.02 --Smith River below Mud Springs Creek 463437111021701 14:05 115.2 20.2 460 14.6 --

G 0.73 --

Big Birch Creek at mouth 06075900 15:55 112.6 24.0 320 -- 0.98 P 0.10 --Newlan Creek at mouth 06076550 15:00 112.4 20.8 439 -- 4.45

G 0.22 --

Smith River below Newlan Creek 

(computed from gage)

 06076560 15:00 112.1 -- -- 21.0 --

G 1.05 0.97 ± 1.30

Total (10.1 river miles) Net loss -2.00 ± 1.26

Reach 5 (fig. 6) - Smith River below Newlan Creek to Smith River below Eagle Creek (fig. 6)

Smith River below Newlan Creek 

(computed from gage)

 06076560 15:00 112.1 -- -- 21.0 --

G 1.05 --

Thompson Gulch near mouth 463638111051801 -- 108.1 -- -- -- -- -- -- --Spring Creek at Highway 360 bridge 463743111042701 -- 106.5 -- -- -- -- -- -- --Note - Unable to calculate tributary inflow 

because main-stem flow declined 

 -- -- -- -- -- -- -- -- --

Smith River above Rock Springs Creek 06076580 13:00 105.1 22.0 394 17.5 --

G 0.88 -3.50 ± 1.37

Smith River at Highway 360 bridge 464033111083501 14:05 98.4 23.5 385 15.0 --

G 0.75 -2.50 ± 1.15

Table 8. Estimated streamflow gains and losses, upper Smith River watershed, Montana, August 1, 2007.—Continued

[Station identification number, see “Site-Identification Systems” section for explanation; River mile, distance above mouth; Temperature, water temperature in degrees Celsius; Streamflow measurement rating: (G) good (less than 5 percent measurement error), (F) fair (5 to 8 percent measurement error), (P) poor (greater than 8 percent measurement error). Abbreviations: °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second. Symbols: --, not applicable or not measured. Note: main-stem values in bold type]
38 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed Location description Station identification number Time River mile Temperature (°C) Specific conduc- tance (μS/cm) Main-stem streamflow (ft3/s) Tributary streamflow (ft3/s) Streamflow measure- ment rating Estimated measurement error (ft3/s) Estimated streamflow gain (+) or loss (-) and associated measurement error (ft3/s) Reach 5 (fig. 6) - Smith River below Newlan Creek to Smith River below Eagle Creek (fig. 6) Unnamed tributary to Smith River at mouth near Fort Logan 464034111092001 -- 97.8 -- -- -- -- -- -- -- Unnamed tributary to Smith River -from Soldiers Lake 464043111100801 -- 96.8 -- -- -- -- -- -- -- Note - Unable to calculate tributary in- flow because main-stem flow declined -- -- -- -- -- -- -- -- -- Smith River above Camas Creek 464218111113501 13:30 94.3 23.1 370 13.2 -- F 1.06 -1.80 ± 1.30 Camas Creek at mouth 06076600 -- 94.2 -- -- -- -- -- -- -- Benton Gulch at mouth 06076650 -- 94.1 -- -- -- -- -- -- --

2Camas Creek and Benton Gulch (calculated) -- -- -- -- -- -- 11.0 -- 2.21 --Smith River below Benton Gulch 464222111113201 14:40 94.0 24.8 415 24.2 -- F 1.94 --Smith River below Beaver Creek 464550111094601 -- 88.1 -- -- -- -- -- -- --Smith River near Fort Logan 

(computed from gage)

 06076690 15:00 83.6 -- -- 24.0 --

G 1.20 -0.20 ± 2.72

Sheep Creek at mouth 464816111110001 -- 82.7 -- -- -- -- -- -- --Eagle Creek near mouth 464942111095101 -- 81.4 -- -- -- -- -- -- --2Sheep Creek and Eagle Creek 

(calculated)

 -- -- -- -- -- -- 33.0 -- 3.09 --

Smith River below Eagle Creek 06077200 15:00 80.8 -- -- 57.0 --

G 2.85 --

Total (31.3 river miles) Net loss -8.00 ± 4.86

Upper Smith River (from Smith River below North Fork Smith River to Smith River below Eagle Creek)

Total (41.4 river miles) Minimum total tributary inflow 54.9 Net loss -10.00 ± 4.91

1Calculated net gain is less than the associated errors.2Tributary value calculated as the difference between upstream and downstream main-stem measurements.

Table 8. Estimated streamflow gains and losses, upper Smith River watershed, Montana, August 1, 2007.—Continued

[Station identification number, see “Site-Identification Systems” section for explanation; River mile, distance above mouth; Temperature, water temperature in degrees Celsius; Streamflow measurement rating: (G) good (less than 5 percent measurement error), (F) fair (5 to 8 percent measurement error), (P) poor (greater than 8 percent measurement error). Abbreviations: °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second. Symbols: --, not applicable or not measured. Note: main-stem values in bold type]
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 39

Figure 14. Generalized potentiometric surface, groundwater-flow direction, and delineation of gaining and 

losing stream reaches during irrigation season conditions, upper Smith River watershed, Montana, August 

2007.

N:\Jeff\den12_cmra00_0091_sir_caldwell\figures\figure_14.ai

Base modified from U.S. Geological Survey digital National

Elevation Dataset, 30 meter, 2006

U.S. Census Bureau TIGER data, 1:100,000, 2000

Lambert Conformal Conic Projection

Standard parallels 45° and 49°, central meridian -109° 30"

North American Datum of 1983 (NAD83).

0 1 2 3 4 5 MILES

0 1 2 3 4 5 KILOMETERS

R.3 E. R.4 E. R.5 E. R.6 E. R.7 E. R.8 E.

T.7 N.

T.8 N.

T.9 N.

T.10 N.

T.11 N.

T.12 N.

T.13 N.

Upper Smith River Watershed boundary

Eagle Creek

South

Side

Canal

Spring Creek

Fourmile

Creek

North Fork

Smith River

South Fork

Smith River

Smith River

Newlan Creek

Big Birch Creek

Sheep Creek

Camas Creek

Beaver Creek

111°10'

46°50'

Newlan Creek

Reservoir

Potentiometric contour—Shows altitude at which water would 

have stood in tightly cased wells generalized from August 2007

measurements. Contour intervals10 and 50 feet. Datum is 

North American Vertical Datum of 1988

Gaining Reach

Neutral Reach—Errors larger 

 than calculated gain or loss Extent of stream reach

Unmeasured Reach

General groundwater-flow

 direction

Study well

Losing Reach

EXPLANATION

4,900

4,880

4,860

4,840

4,820

5,000 5,100

4,940

5,150

5,200

5,060

5,100

4,750

4,650

4,700

4,960

4,920

5,200

4,980

5,060

5,050

46°40'

46°30'

111°00' 110°50'

Camp Baker

Fort Logan

White Sulphur

Springs

Willow Creek

89

89

89

12

BROADWATER

COUNTY

MEAGHER

COUNTY

5,100

Neutral 0.13 +/- 0.36 cfs

Loss - 9.00 +/- 4.86 cfs

Loss - 67.6 +/- 3.16 cfs

Gain 5.13 +/- 0.82 cfs

Loss -2.00 +/- 1.26 cfs

12
40 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

sections are due to a combination of diversions and groundwater levels that are lower than the stream stage supporting 

losing conditions. As you travel downstream near the mouth, 

groundwater levels are higher than the stream stage supporting streamflow gains. The North Fork Smith River had a net 

streamflow decrease of 67.6 ft3/s over the lower 5.8-mi reach 

(reach 2) which is likely due to the effects of several irrigation diversions active during that measurement. A net 5.13 

ft3/s gain was calculated for the area including the confluence of the North and South Forks of the Smith River. There 

were no observed diversions occurring within this area and 

the calculated net gain is similar to gains calculated from the 

non-irrigation season synoptic measurements. Available data 

from the upper 41.4 mi (reaches 4 and 5) of the main stem 

Smith River indicated a net streamflow decrease (either from 

loss to groundwater or diversions) of 11.0 ft3/s, which likely 

underestimates the actual decrease since tributary inflow was 

underrepresented.

 Streamflow profiles constructed from data collected 

August 1, 2007 illustrates conditions during a period of irrigation with large-scale diversions in combination with effects 

due to tributary inflow, inflow from groundwater discharge, 

and losses due to leakage to groundwater (fig. 15). In several 

cases, main-stem streamflow declined downstream even with 

the addition of tributary inflow. The streamflow profile of 

the upper section of the South Fork Smith River illustrates 

the overall net loss in streamflow to a point where the stream 

nearly went dry due to leakage to groundwater and diversions (fig. 15A). At some point downstream from river mile 

11, groundwater discharge caused streamflow to increase. 

An overall net gain in streamflow was measured by the end 

of the reach (fig. 15A). The profile of the North Fork Smith 

River illustrates a 67.6 ft3/s net loss from below Spring Creek 

(river mile 8.4) to river mile 2.6 as main-stem streamflow was 

less than the cumulative tributary inflow (fig. 15B). These 

net losses were primarily due to irrigation diversions and to 

a smaller extent, losses to groundwater. In several cases, net 

losses occurred along reaches even though tributary inflow 

was occurring. The streamflow profile of the Smith River 

representing the 44-mi reach starting above the confluence of 

the North Fork and South Fork Smith Rivers and continuing 

downstream to the streamflow gaging station below Eagle 

Creek shows only slight net gains or losses followed by the 

most dramatic changes in streamflow due to tributary inflow 

from Sheep Creek (fig. 15C).

Estimated Groundwater Discharge and the 

Effects of Irrigation Practices on Streamflow

Streamflow data from several streamflow-gaging stations operated continuously from April 1 through September 

30, 2010 were used to estimate the amount of groundwater 

that discharged to the Smith River and the effects of irrigation practices on streamflow in the upper watershed. The 

computed daily streamflow of the Smith River below Newlan 

Creek streamflow-gaging station (station 06076560) and the 

combined (summed) daily streamflow of the major tributaries above this gage including the North and South Forks of 

the Smith River, Big Birch Creek, and Newlan Creek are 

shown in figure 16. The several small-scale tributaries, drains, 

and springs within this area that were ungaged in 2010 were 

measured during the synoptic events in March and October 

2007, and April 2008,and accounted for an average inflow 

of 11.0 ft3/s (see Generalized Groundwater Flow Direction 

and Streamflow Gains and Losses section). The average daily 

streamflow at the Smith River below Newlan Creek streamflow-gaging station was 27.5 ft3

/s greater than the sum of the 

upstream gaged tributaries in 2010. Assuming an average of 

11 ft3/s of inflow from ungaged tributaries, groundwater inflow 

to the Smith River along this reach may account for an average of about 16 ft3

/s or about 1.6 ft3/s per river mile increase in 

streamflow during the 2010 period of record.

The continuous 2010 streamflow record illustrates the 

effects of irrigation withdrawals on streamflow in the upper 

watershed. Most of the available 2010 continuous record 

(April 1 through May 15 and from July 15 through September 

30) indicated a net difference of about 25 ft3/s between the 

main-stem outflow measured below Newlan Creek and the 

combined inflow of the upstream tributaries (fig. 16). These 

periods represent conditions prior to and after widespread 

flood irrigation withdrawals. Periods of substantial irrigation 

withdrawals were readily apparent in the streamflow record 

(fig.16), especially during a few days near the end of April 

and again during the last two weeks in May; consistent with 

typical periods of irrigation withdrawals for intensive flood 

and sprinkler irrigation. For example, a short-term period of 

intense irrigation withdrawals was observed on 4/30/2010 

when 60 ft3/s more tributary inflow was entering the upper 

watershed than was leaving it at the Smith River streamflowgaging station below Newlan Creek.

The continuous data not only represents the withdrawals 

from the Smith River during the irrigation season, but also the 

timing and magnitude of net irrigation return flows (irrigation 

and conveyance water that is not evaporated or consumed by 

plants that eventually returns to an aquifer or surface water). 

A period of intense irrigation withdrawal during the last two 

weeks in May was followed by a period (early June 2010 to 

mid-July 2010) with the largest net increase (an average of 

71.1 ft3/s) in streamflow at the Smith River streamflow-gaging 

station below Newlan Creek relative to tributary inflow (fig. 

16). This observation is likely due to increased groundwater 

discharge to the Smith River resulting from irrigation return 

flow. By late July, the apparent effects of return flows receded, 

and the net increase in streamflow measured below Newlan 

Creek returned to about 25 ft3/s. 
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 41

N:\Jeff\den12_cmra00_0091_sir_caldwell\figures\figure_15.ai

0

100

80

80

0.5

1.0

1.5

2.0

2.5

3.0

3.5

16 14 12 10 8 6 4 2 0

Streamflow, in cubic feet per second 

River mile above confluence

A. South Fork Smith River

B. North Fork Smith River

C. Upper Smith River

EXPLANATION

60

40

20

0

60

40

20

0

9 8

130 120 110 100 90 80

7 6 5 4 3 2 1 0

Main stem South Fork Smith River

Cumulative tributary inflow

EXPLANATION

Main stem Smith River

Cumulative tributary inflow

EXPLANATION

Main stem North Fork Smith River

Cumulative tributary inflow

Contribution from Spring Creek

North Fork and South

Fork Smith Rivers

Big Birch and

Newlan Creeks

Camas Creek and

Benton Gulch

Sheep and

Eagle Creeks

Net Loss

Net Loss

Figure 15. Instantaneous streamflow and cumulative tributary inflow of the A, South Fork Smith River; B, North Fork Smith River; 

and C, upper Smith River, Montana, August 1, 2007.
42 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Qualitative Interpretation of Temperature and 

Water-Level Data

Water-level and temperature data collected at the 10 

groundwater and surface-water monitoring sites of the North 

and South Forks of the Smith River and the Smith River 

(fig. 8) were qualitative indicators of flow direction and magnitude. The observed data typically collected from late March 

to early November in 2007 and late March to early December 

2008 indicated the presence of both losing and gaining stream 

reaches and dynamic changes in direction and magnitude with 

time.

Water temperatures in area streams typically ranged from 

0 to over 25 degrees Celsius (°C) annually primarily due to 

variations in air temperature. Daily temperatures in stream 

water temperatures varied more than 10°C during 24-hour 

periods at some locations, apparently caused by diel changes 

in air temperature. Although groundwater is generally insulated from the daily air-temperature variation, temperatures 

in some shallow monitoring wells varied more than 5°C in a 

24-hour period and some varied more than 15°C during the 

study period.

Depending on relative temperatures and volumes of 

exchanged water, the effects of groundwater inflow can be 

measureable in the stream temperature record. In the case of a 

gaining stream, groundwater inflow can measurably dampen 

and attenuate the diel temperature cycles in a stream. This 

condition is most apparent at the farthest downstream South 

Fork Smith River groundwater/surface-water monitoring site 

(station 06075785) with comparably dampened stream temperatures throughout the record and typically cooler temperatures than the upstream stations during the summer months 

(fig. 17). Stream temperatures at this site are cooler than the 

air temperature and the temperature measured in the shallow 

monitoring wells at the site, suggesting inflow of cooler, more 

regional groundwater at that location or upstream. Substantial 

groundwater inflows were not apparent in a review of continuous stream temperature data collected at other groundwater and surface-water monitoring sites (fig.8) as the stream 

temperature records followed similar trends to dampened air 

temperature (Nilges and Caldwell, 2012).

The altitudes of the stream stage and the groundwater 

levels at the 10 groundwater and surface-water monitoring 

sites were generally higher in 2008 than in 2007, coincident 

Figure 16. Streamflow at the Smith River below Newlan Creek streamflow-gaging station (station 06076560) and the combined 

streamflow of major tributaries in the upper Smith River watershed, Montana, April 2010 through September 2010.

N:\Jeff\den12_cmra00_0091_sir_caldwell\figures\figure_16.ai

0

200

700

Streamflow, in cubic feet per second

EXPLANATION

Periods of high

diversion rates

Periods of largest net

streamflow increase

from irrigation

return flows

300

400

500

600

100

Smith River below Newlan Creek (06076560)

Sum of South Fork Smith River near mouth (06075785),

 North Fork Smith River near mouth (06075700), Big Birch

 Creek below diversion at 1.7 miles (463357111031801),

 and Newlan Creek at mouth (06076550)

April May

2010

June July August September
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 43

with higher precipitation values in 2008. Groundwater levels 

(Nilges and Caldwell, 2012) at the network sites typically 

were the highest in the late spring to early summer (late May 

through early July), fell during the summer (July to early 

August), and then recovered during the late summer through 

the fall. Many area wells at greater distances from the Smith 

River and its tributaries also showed similar trends (Nilges and 

Caldwell, 2012). 

Increased recharge from snowmelt, local precipitation, 

high streamflow, and local flood irrigation at some locations 

likely caused the higher groundwater levels in the late spring 

or early summer. Summer declines in groundwater levels can 

be associated with reduced precipitation, local and regional 

effects of groundwater withdrawals, evapotranspiration (ET), 

and reduced streamflow and subsequent leakage in some area 

streams. Summer groundwater level declines ended during 

mid-August to mid-September at most sites, likely as a result 

of decreased groundwater use (irrigation), increased flow in 

losing streams, decreased ET, and the onset of local, latesummer flood irrigation which was noted at or near some sites. 

Of note, rising groundwater levels in late summer to early fall 

in near-stream wells corresponded with a decrease in nighttime air temperatures, which likely caused freezing of leaves 

on phreatophytes in the area (a killing frost), and reduced the 

consumption of groundwater by the plants.

Although differences in water levels (groundwater versus 

surface water) were small (0.03 ft or less) and approached 

measurement uncertainty in some instances, most differences 

in groundwater levels and stream stage exceeded measurement 

uncertainty. Gradients between the stream and groundwater 

changed direction during the course of the study at six of the 

groundwater/surface-water monitoring sites. Hydraulic gradients between the groundwater and the stream indicated periods 

of potential streamflow gains (groundwater level higher than 

stream stage) and losses (groundwater level lower than stream 

stage). Groundwater levels in some wells installed in the 

streams were as much as 2 ft higher or lower than stream stage.

The following sections provide descriptions and qualitative interpretation of the water-level and water-temperature 

data collected in 2007 and 2008 at the 10 groundwater/surface-water monitoring sites. Data from all monitoring sites are 

included in Nilges and Caldwell (2012). 

Figure 17. Water temperature at South Fork Smith River temporary streamflow-gaging stations and local air temperature, upper Smith 

River watershed, Montana, May 2007 through October 2007 and May 2008 through November 2008.

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_17.ai

Air at South Fork Smith River near mouth (station 06075785)

Stream at South Fork Smith River at Birky Road (station 06075775)

Stream at South Fork Smith River 4.8 miles below Cottonwood Creek (station 06075780)

Stream at South Fork Smith River near mouth (station 06075785)

-10 Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

0

Temperature, in degrees celsius

EXPLANATION

5

10

15

20

25

30

35

40

-5

2007

Month

2008

Stream temperature dampened by groundwater inflow

at streamflow–gaging station 06075785 compared to

other South Fork Smith River streamflow–gaging stations
44 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

South Fork Smith River at Birky Road 

(Groundwater and Surface-Water Monitoring 

Site 1)

A strong and dynamic connection between groundwater and surface water was observed at the South Fork Smith 

River at Birky Road (1.6 mi below Cottonwood Creek) and a 

single monitoring well (SF0606B) installed in the center of the 

stream (station 06075775, site 1 on fig. 8). Stable to gaining 

conditions were apparent in the spring and fall of both 2007 

and 2008 as groundwater levels were near or above stream 

stage (figs. 18A and B). Losing conditions became apparent as 

groundwater levels fell below stream stage during the summer 

months of both years (figs. 18A and B); groundwater levels 

declined to 0.54 ft below the stream stage during mid-summer 

2007 and declined to 0.37 ft below stream stage in 2008.

Losing conditions during the summer months were also 

identified by using heat as tracer (temperature measured in 

and below the stream). Temperatures measured below the 

streambed resembled dampened stream temperatures (fig. 18C

and D). The infiltration of stream water to a depth of at least 

2.89 ft (the depth of the deepest thermistor) was apparent as 

temperatures measured at that depth closely matched the trend 

of the stream at the shallow thermistor.

South Fork Smith River 4.8 Miles below 

Cottonwood Creek (Groundwater and SurfaceWater Monitoring Site 2)

Dynamic changes between gaining and losing conditions 

were exhibited at the South Fork Smith River 4.8 mi below 

Cottonwood Creek and a single monitoring well (SF0605) 

installed in the center of the stream (station 06075780, site 

2 on fig. 8). Coincident with the timing of local flood irrigation (during the spring of both 2007 and 2008), groundwater 

levels rose to the point where water was flowing out of the 

top of the well with measured groundwater altitudes of up 

to 0.7 ft higher than stream stage (fig. 19A and 19B). During 

the summer months of both years, the gradient reversed and 

groundwater levels dropped below stream stage and at times 

groundwater levels declined to 1.3 ft below the bottom of the 

streambed. Periods where groundwater levels dropped below 

the bottom of the streambed indicate a possible disconnection 

(unsaturated conditions) between the stream and the water 

table. Streamflow was less than 1 ft3/s for most of July and 

August, 2007. This part of the stream went dry during July and 

August of 2008, thus classifying this tributary as intermittent. 

The presence of water in the stream during periods of potentially unsaturated conditions below the stream indicates the 

presence of low permeability streambed sediments at this location. Once disconnected the water table and the stream stage 

can act independently of one another. Groundwater levels 

rebounded late in both summers to levels higher than stream 

stage in 2007 and close to stream stage (typically less than 0.3 

ft below stream stage) in 2008.

The thermal record at this site supports limited exchange 

(flow) between the stream and the underlying aquifer. Losing 

conditions during the summer were consistent with temperatures measured at 1.48 ft below the streambed that followed 

the general trend of temperatures measured in the stream (fig. 

19C). The deeper thermistor (2.98 ft below the stream bottom) was often cooler with very little diel variation (fig. 19D). 

As groundwater levels fell below the streambed (possible 

unsaturated conditions), the diel temperature fluctuations were 

reduced. Therefore, although water levels point to leakage 

from the stream during the summer months, the limited diel 

variation in the thermal signal measured below the stream 

indicated limited connection between the stream and groundwater during losing conditions.

South Fork Smith River near Mouth (Groundwater 

and Surface-Water Monitoring Site 3)

Groundwater discharge to the stream was evidenced by 

both water-level and temperature data throughout the entire 

record at the South Fork Smith River near mouth (station 

06075785; site 3, fig. 8). During both years (2007 and 2008), 

groundwater levels measured in the four monitoring wells 

(fig. 20) were generally 1.0 ft higher than stream stage (Nilges 

and Caldwell, 2012). Groundwater levels were the highest 

during the late spring to early summer periods of high streamflow and flood irrigation (fig. 21A). Although stream stage 

remained relatively constant through the summer and early 

fall, groundwater levels declined during most of the summer. Groundwater levels began rising during mid-August 

to mid-September resulting in increased hydraulic gradients 

from groundwater to surface water (fig 21A and 21B). This 

late summer rise in groundwater levels is likely the result of a 

combination of factors including decreased evapotranspiration 

(Bureau of Reclamation, 2007 and 2008), local recharge from 

late season flood irrigation in the area, and/or reduction in 

groundwater withdrawals for irrigation.

Stream temperatures were dramatically influenced by 

groundwater discharge at this site. Temperature variations 

measured in and below the stream were reduced compared to 

other monitored locations (Nilges and Caldwell, 2012). Stream 

temperatures tracked closely with the temperatures measured 

below the streambed and were dampened compared to air 

temperature (fig. 21C and 21D). This suggests that discharge 

of groundwater of relatively stable temperature (cooler in the 

summer), and possibly following a more regional flow path, 

affected the stream temperature at this station. Temperatures 

also indicate the relative contribution of groundwater inflow 

in relation to the overall streamflow at this location. The 

largest diel variation in stream water temperature, probably 

most affected by air temperature, occurred during periods of 

relatively high streamflow in the spring to early summer in 

both 2007 and 2008. The diel variation was noticeably reduced 

during the remaining record. Groundwater inflow likely influences temperatures to a greater degree during these periods of 
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 45

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_18A.ai

South Fork Smith River (station 06075775)—Manual measurement

SF0606B instream well—Manual measurement

Streambed bottom

Manual measurement

Line of zero difference

Losing Gaining

A

B

Stage or groundwater altitude, in feet above NAVD 1988

EXPLANATION

EXPLANATION

5,040.5

5,040.0

5,041.0

5,041.5

5,042.0

5,042.5

5,043.0

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Difference between groundwater level in Well SF0606B

and stream stage of station 06075775, in feet

-0.8

-1.0

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

1.0

0.8

2007

Month

2008

Figure 18. Data collected at the South Fork Smith River at Birky Road monitoring site (station 06075775). A, Altitude of stream stage 

and groundwater at well SF0606B; B, Difference in head between the groundwater at well SF0606B and stream; C, Hourly temperature 

of stream at station and in monitoring well SF0606B at depths of 1.39 feet and 2.89 feet below the streambed; and D, Diel temperature 

variation in monitoring well SF0606B at depths of 1.39 feet and 2.89 feet below the streambed, May 2007 through November 2007 and 

March 2008 through December 2008.
46 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_18B.ai

Air at station 06075785

South Fork Smith River (station 06075775)

Well SF0606B at 1.39 feet below streambed

Well SF0606B at 2.89 feet below streambed

Well SF0606B at 1.39 feet below streambed

Well SF0606B at 2.89 feet below streambed

Temperature, in degrees celsius

EXPLANATION

EXPLANATION

-15

-20

-10

-5

0

5

10

15

20

25

30

35

0

0.5

1.0

1.5

2.0

2.5

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Diel temperature variation, in degrees celsius

-0.5

2007

Month

2008

C

D

Figure 18. Data collected at the South Fork Smith River at Birky Road monitoring site (station 06075775). A, Altitude of stream stage 

and groundwater at well SF0606B; B, Difference in head between the groundwater at well SF0606B and stream; C, Hourly temperature 

of stream at station and in monitoring well SF0606B at depths of 1.39 feet and 2.89 feet below the streambed; and D, Diel temperature 

variation in monitoring well SF0606B at depths of 1.39 feet and 2.89 feet below the streambed, May 2007 through November 2007 and 

March 2008 through December 2008.—Continued.
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 47

Figure 19. Data collected at the South Fork Smith River monitoring site (station 06075780) 4.8 mi below Cottonwood Creek. A, Altitude of 

stream stage and groundwater at well SF0605; B, Difference in hydraulic head between groundwater and stream; C, Hourly temperature 

measurements of air at station 06075785, in stream at the South Fork Smith River (station 06075780), and in monitoring well SF0605 at 

depths of 1.48 ft and 2.98 ft below the streambed; and D, Diel temperature variation in monitoring well SF0605 at depths of 1.48 ft and 2.98 

ft below the streambed, March 2007 through November 2007 and April 2008 through December 2008.

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_19A.ai

Dry to nearly

dry stream

Dry to nearly

dry stream

Stage or groundwater altitude, in feet above NAVD 1988

4,990.0

4,989.5

4,990.5

4,991.0

4,991.5

4,992.0

4,992.5

4,993.0

4,993.5

4,994.0

4,994.5

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Difference between groundwater level in Well SF0605

and stream stage of station 06075780, in feet

-2.5

-3.0

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

2007

Month

2008

A

B

EXPLANATION

South Fork Smith River (station 06075780)—Manual measurement

SF0605 instream well—Manual measurement

Streambed bottom

South Fork Smith River (station 06075780)—Hourly measurements

SF0605 instream well—Hourly measurements

Losing Gaining

Hourly measurements

Line of zero difference

EXPLANATION

Manual measurement
48 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_19B.ai

Dry to nearly

dry stream

Temperature, in degrees celsius

EXPLANATION

EXPLANATION

-15

-20

-10

-5

0

5

10

15

20

25

30

35

0

0.5

1.0

1.5

2.0

2.5

3.0

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Diel temperature variation, in degrees celsius

-0.5

2007

Month

2008

C

D

Air at station 06075785

South Fork Smith River (station 06075780)

Well SF0605 at 1.48 feet below streambed

Well SF0605 at 2.98 feet below streambed

Well SF0605 at 1.48 feet below streambed

Well SF0605 at 2.98 feet below streambed

Figure 19. Data collected at the South Fork Smith River monitoring site (station 06075780) 4.8 mi below Cottonwood Creek. A, Altitude of 

stream stage and groundwater at well SF0605; B, Difference in hydraulic head between groundwater and stream; C, Hourly temperature 

measurements of air at station 06075785, in stream at the South Fork Smith River (station 06075780), and in monitoring well SF0605 at 

depths of 1.48 ft and 2.98 ft below the streambed; and D, Diel temperature variation in monitoring well SF0605 at depths of 1.48 ft and 2.98 

ft below the streambed, March 2007 through November 2007 and April 2008 through December 2008.—Continued
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 49

Figure 20. Channel geometry, monitoring well network, and thermistor and/or pressure transducer locations at South Fork Smith 

River near mouth monitoring site (station 06075785). Groundwater altitudes and stream stage for May 11, 2007.

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_20.ai Altitude, in feet above North American Vertical Datum of 1988

Distance from left bank, in feet

EXPLANATION

Soil Instrument type

Thermistor

Upper instrumentation in

 monitoring well

Pressure transducer

Monitoring well installation

Lower instrumentation in

 monitoring well

Stream instrumentation

Stream instrumentation

Quaternary alluvium—Shallow

 near-streambed sediments

4,926

4,928

4,914

4,920

4,922

4,924

4,916

4,918

staff gage

Left bank

Right

bank

South Fork Smith River

Well SF0604

Well SF0603

Well SF0601

Well SF0602

Groundwater altitudes May 11, 2007

Stream stage May 11, 2007

0 5 10 15 20 25 30 35 40 45

Well SF0601

Groundwater altitudes—Inferred

 between wells

Monitoring well and identifier—

 Perforated near bottom
50 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Figure 21. Data collected at the South Fork Smith River near mouth monitoring site (station 06075785). A, Altitude of stream stage and 

groundwater at well SF0603; B, Difference in hydraulic head between the groundwater at well SF0603 and stream; C, Hourly temperature 

measurements of air at station 06075785, stream at station 06075785, in monitoring well SF0603 at depths of 1.65 ft and 3.15 ft below the 

streambed; and D, Diel temperature variation in monitoring well SF0603 at depths of 1.65 ft and 3.15 ft below the streambed, March 2007 

through December 2007 and March 2008 through December 2008.

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_21A.ai

Hourly Measurements

Stage or groundwater altitude, in feet above NAVD 1988

EXPLANATION

4,920.5

4,920.0

4,921.0

4,921.5

4,922.0

4,922.5

4,923.0

4,923.5

4,924.0

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Difference between groundwater level in Well SF0603

and stream stage of station 06075785, in feet

0.2

0.0

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2007

Month

2008

Manual measurement

A

B

EXPLANATION

South Fork Smith River (station 06075785)—Manual measurement

SF0603 instream well—Manual measurement

Streambed bottom

South Fork Smith River (station 06075785)—Hourly measurements

SF0603 instream well—Hourly measurements

Gaining
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 51

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_21B.ai Temperature, in degrees celsius

EXPLANATION

EXPLANATION

-15

-20

-10

-5

0

5

10

15

20

25

30

35

0.0

0.5

1.0

1.5

2.0

2.5

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Diel temperature variation, in degrees celsius

-0.5

2007

Month

2008

C

D

Air at station 06075785

South Fork Smith River (station 06075785)

Well SF0603 at 1.65 feet below streambed

Well SF0603 at 3.15 feet below streambed

Well SF0603 at 1.65 feet below streambed

Well SF0603 at 3.15 feet below streambed

Figure 21. Data collected at the South Fork Smith River near mouth monitoring site (station 06075785). A, Altitude of stream stage 

and groundwater at well SF0603; B, Difference in hydraulic head between the groundwater at well SF0603 and stream; C, Hourly 

temperature measurements of air at station 06075785, stream at station 06075785, in monitoring well SF0603 at depths of 1.65 ft and 

3.15 ft below the streambed; and D, Diel temperature variation in monitoring well SF0603 at depths of 1.65 ft and 3.15 ft below the 

streambed, March 2007 through December 2007 and March 2008 through December 2008.—Continued.
52 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

reduced streamflow because groundwater is responsible for a 

larger percentage of total streamflow. This is especially apparent in the mid-summer 2007 for temperatures measured at 

3.15 ft below the stream bottom in well SF0603, which tracks 

very closely with the measured stream temperature (fig. 21C).

North Fork Smith River near Mouth (Groundwater 

and Surface-Water Monitoring Site 4)

Losing conditions were predominant at the North Fork 

Smith River near the mouth (station 06075700, site 4 on 

fig. 8). During the majority of both years, groundwater 

levels measured in the four monitoring wells (fig. 22) were 

below stream stage (Nilges and Caldwell, 2012). During the 

late spring to early summer periods of high streamflow and 

local flood irrigation, groundwater altitudes nearly equaled 

the stream stage (fig. 23A and 23B) (hydraulic gradients 

approached zero). Unsaturated conditions occurred as groundwater levels declined to 1.0 ft or more below the streambed 

during the summer months. However, groundwater levels 

were measured at or near the stream banks, and the hydraulic 

connection between the stream and the groundwater in the 

middle of the cross section was unmeasured. The hydraulic 

gradient from the stream to the groundwater increased during 

the summer months as the groundwater levels declined with 

relatively little variation in stream stage. Although decreased 

stream leakage may contribute to the declining groundwater 

levels during this period, the relatively stable stream stage 

indicates that other factors such as reduced recharge from 

discontinued local flood irrigation, increased groundwater 

withdrawal through wells, and increased ET contributed to the 

declining groundwater levels during the summer. Groundwater 

levels began rising during mid-August to mid-September and 

approached or exceeded stream-stage during the fall of both 

years. Again, stream stage remained relatively constant, an 

indication that other contributing factors in addition to stream 

leakage such as reduced rates of ET and groundwater use 

affected the groundwater levels.

Rapid changes in the water levels illustrated the dynamic 

interaction of groundwater and surface water at this site, 

particularly evident during the late fall of both 2007 and 

2008 (fig. 23A). The North Fork Smith River was temporarily 

diverted upstream from the gage and the stream nearly went 

dry during construction of a downstream bridge in October 

2007 causing groundwater levels to drop 0.3 ft (well NF0602) 

in 13 hours. Groundwater levels rebounded when flow in the 

North Fork Smith River returned. During October 2008, debris 

on a downstream culvert caused backwater and the stream 

stage to increase by 1.6 ft, followed by a sudden release that 

resulted in a rapid 2.0 ft decline in stream stage. Although 

groundwater level altitudes increased with the increasing 

stream stage, the sudden decline in stream stage after the 

debris was removed caused a dramatic gradient reversal (from 

a losing reach to a gaining reach) as the stream stage dropped 

faster than the groundwater level (fig. 23A and 23B). 

Losing conditions were also supported by using heat as 

a tracer as temperatures below the stream (fig. 23C) followed 

a slightly dampened seasonal and diel trend observed in the 

stream (indicative of advective flow of heat from the stream to 

the groundwater). Temperatures measured below the streambed may also be affected by unsaturated conditions at times. 

The infiltration of stream water was apparent, as temperatures measured at depths of nearly 3.0 ft below the streambed 

resembled those of the stream (example; well NF0602, fig. 

23C). Temperatures in the monitoring wells at or near the 

right bank (NF0601 and NF0602) during the late April to late 

August were more dynamic and values resemble the surface 

water more than the left bank wells (NF0603 and NF0604) 

(Nilges and Caldwell, 2012). This greater similarity of the 

right bank monitoring wells to the stream potentially indicates (1) a greater quantity of water moving from the stream 

to the right bank side than to the left bank side or (2) reduced 

thermal conductance near the left bank because of unsaturated 

conditions. 

Smith River below North Fork Smith River 

(Groundwater and Surface-Water Monitoring 

Site 5)

Slightly gaining conditions and the occurrence of local 

recharge from flood irrigation were apparent at the Smith 

River below North Fork Smith River (station 06075810; site 

5 on fig. 8). Groundwater levels from all five wells at this site 

(fig. 9) followed the general trend of the stream stage, but 

were higher than stream stage in nearly all instances (Nilges 

and Caldwell, 2012). Groundwater levels in well SR0616 

ranged from 0.06 to 0.28 ft higher than stream stage with a 

median of 0.11 ft in (fig. 24A and 24B). Groundwater altitudes 

were the highest during the late spring-early summer periods 

of high streamflow and in the early fall. The largest measured 

gradient from groundwater to the stream at well SR0616 

occurred May 24, 2007 (0.25 ft) and June 27, 2008 (0.28 ft). 

Both of these events occurred during periods of local flood 

irrigation, which likely caused a rise in local groundwater 

levels due to increased groundwater recharge.

Consistent with a gaining reach, temperatures measured 

beneath the stream in the four instrumented wells were typically cooler than the stream and showed limited diel fluctuation for most of the record (Nilges and Caldwell, 2012). 

Beginning in August of both years, temperatures beneath the 

streambed tracked more closely to stream temperatures and 

showed more diel fluctuation (fig. 24C and 24D), although 

observed hydraulic head gradients continued to indicate flow 

from the groundwater to the stream. Late season temperatures 

may indicate (1) a period of reduced groundwater discharge 

with temperatures below the streambed becoming more 

affected by the conduction of heat from the stream through the 

streambed or (2) a period of increased groundwater discharge 

of a localized flow system rather than groundwater of a moreregional flow system. Shallow groundwater of a localized flow 
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 53

system (for example, groundwater recharged during local, lateseason flood irrigation) would likely have more temperature 

fluctuation than groundwater of a more regional system.

Smith River at Birch Creek Road and Smith River 

below Woods Gulch (Groundwater and SurfaceWater Monitoring Sites 6 and 7)

Dominant flow to or from the stream was not apparent 

at the single instream well (SR06B) at Smith River at Birch 

Creek Road (site 6 on fig. 8) and two instream wells (SR0612 

and SR0613) at the Smith River below Woods Gulch (site 7 

on fig. 8). Data from the Smith River at Birch Creek Road 

(station 463257111002801) (Nilges and Caldwell, 2012) 

indicated that the site was neither strongly gaining nor losing 

during the period of record as the measured hydraulic gradient 

was oftentimes within measurement uncertainty. Temperatures 

from the single monitoring well tracked very closely to that of 

the stream and showed diel variation consistent with a losing 

reach or conductive heat flow in a slightly gaining reach.

Data from the Smith River below Woods Gulch (station 

463270111011401) (Nilges and Caldwell, 2012) indicated 

that the site was slightly losing during most of the period of 

record. The measured hydraulic gradient consistently showed 

a slight loss with groundwater levels typically less than 0.1 ft 

below the stream stage. Temperature measured in the monitoring wells below the streambed tracked very closely with the 

stream temperature and showed diel variation consistent with 

a losing reach.

Figure 22. Channel geometry, monitoring well network, and thermistor and/or pressure transducer locations at North Fork Smith 

River near mouth monitoring site (station 06075700). Groundwater altitudes and stream stage for May 11, 2007.

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_22.ai

EXPLANATION

Soil Instrument type

Thermistor

Upper instrumentation in

 monitoring well

Pressure transducer

Monitoring well installation

Lower instrumentation in

 monitoring well

Stream instrumentation

Stream instrumentation

Quaternary alluvium—Shallow

 near-streambed sediments

4,956

4,952

4,946

4,954

4,944

4,948

4,942

4,950 staff gage

North Fork Smith River

Right bank Left bank

Well NF0603

Well NF0604

Well NF0602

Well NF0601

Stream stage May 11, 2007

Groundwater altitudes May 11, 2007

Altitude, in feet above North American Vertical Datum of 1988

Distance from left bank, in feet

0 5 10 15 20 25 30 35 40 45 50

Well NF0602

Groundwater altitudes—Inferred

 between wells

Monitoring well and identifier—

 Perforated near bottom
54 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Figure 23. Data collected at the North Fork Smith River near mouth monitoring site (station 06075700). A, Altitude of stream stage 

and groundwater at well NF0602; B, Difference in hydraulic head between the groundwater at well NF0602 and stream; C, Hourly 

temperature measurements of air at station 06075785, stream at station 06075700, and in monitoring well NF0602 at depths of 1.42 ft 

and 2.92 ft below the streambed; and D, Diel temperature variation in monitoring well NF0602 at depths of 1.42 ft and 2.92 ft below the 

streambed, March 2007 through December 2007 and March 2008 through December 2008.

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_23A.ai

Stream stage

affected by debris

on control Stream stage affected by diversion and

extreme cold (river partially froze)

Stage or groundwater altitude, in feet above NAVD 1988

4,947.5

4,947.0

4,948.0

4,948.5

4,949.0

4,949.5

4,950.0

4,950.5

4,951.0

4,951.5

4,952.0

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Difference between groundwater level in Well NF0602

and stream stage of station 06075700, in feet

-1.5

-2.0

-1.0

-0.5

0.0

0.5

1.0

2007

Month

2008

A

B

EXPLANATION

North Fork Smith River (station 06075700)—Manual measurement

NF0602 instream well—Manual measurement

Streambed bottom

North Fork Smith River (station 06075700)—Hourly measurements

NF0602 instream well—Hourly measurements

Losing Gaining

Hourly measurements

Line of zero difference

EXPLANATION

Manual measurement
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 55

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_23B.ai Temperature, in degrees celsius

EXPLANATION

EXPLANATION

-15

-20

-10

-5

0

5

10

15

20

25

30

35

0.0

0.5

1.0

1.5

2.0

2.5

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Diel temperature variation, in degrees celsius

-0.5

2007

Month

2008

C

D

Air at station 06075785

North Fork Smith River (station 06075700)

Well NF0602 at 1.42 feet below streambed

Well NF0602 at 2.92 feet below streambed

Well NF0602 at 1.42 feet below streambed

Well NF0602 at 2.92 feet below streambed

Figure 23. Data collected at the North Fork Smith River near mouth monitoring site (station 06075700). A, Altitude of stream stage 

and groundwater at well NF0602; B, Difference in hydraulic head between the groundwater at well NF0602 and stream; C, Hourly 

temperature measurements of air at station 06075785, stream at station 06075700, and in monitoring well NF0602 at depths of 1.42 ft 

and 2.92 ft below the streambed; and D, Diel temperature variation in monitoring well NF0602 at depths of 1.42 ft and 2.92 ft below the 

streambed, March 2007 through December 2007 and March 2008 through December 2008.—Continued
56 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Figure 24. Data collected at the Smith River below North Fork Smith River monitoring site (station 06075810). A, Altitude of stream 

stage and groundwater at well SR0616; B, Difference in hydraulic head between groundwater at well SR0616 and stream; C, Hourly 

temperature measurements of air at station 06075785, in stream at station 06075810, and in monitoring well SR0616 at depths of 1.72 ft 

and 3.22 ft below the streambed; and D, Diel temperature variation in monitoring well SR0616 at depths of 1.72 ft and 3.22 ft below the 

streambed, March 2007 through November 2007 and March 2008 through December 2008.

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_24A.ai Stage or groundwater altitude, in feet above NAVD 1988

EXPLANATION

EXPLANATION

4,883.0

4,882.5

4,884.0

4,884.5

4,883.5

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Difference between groundwater level in Well SR0616

and stream stage of station 06075810, in feet

0.1

0.0

2007

Month

2008

Smith River (station 06075810)—Manual measurement

SR0616 instream well—Hourly measurement

SR0616 instream well—Manual measurement

Manual measurement Gaining

A

B

Note–Streambed bottom altitude at 4,881.5 feet

0.2

0.3

0.4

0.5
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 57

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_24B.ai Temperature, in degrees celsius

EXPLANATION

EXPLANATION

-15

-20

-10

-5

0

5

10

15

20

25

30

35

0.0

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Diel temperature variation, in degrees celsius

-0.5

2007

Month

2008

C

D

0.5

1.0

1.5

2.0

3.0

2.5

Air at station 06075785

Smith River (station 06075810)

Well SR0616 at 1.72 feet below streambed

Well SR0616 at 3.22 feet below streambed

Well SR0616 at 1.72 feet below streambed

Well SR0616 at 3.22 feet below streambed

Figure 24. Data collected at the Smith River below North Fork Smith River monitoring site (station 06075810). A, Altitude of stream 

stage and groundwater at well SR0616; B, Difference in hydraulic head between groundwater at well SR0616 and stream; C, Hourly 

temperature measurements of air at station 06075785, in stream at station 06075810, and in monitoring well SR0616 at depths of 1.72 ft 

and 3.22 ft below the streambed; and D, Diel temperature variation in monitoring well SR0616 at depths of 1.72 ft and 3.22 ft below the 

streambed, March 2007 through November 2007 and March 2008 through December 2008.—Continued
58 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Smith River above Mud Springs Creek 

(Groundwater and Surface-Water Monitoring 

Site 8)

The effect of local flood irrigation on near-stream hydrology is apparent at the Smith River above Mud Springs Creek 

monitoring site (station 06075850, site 8 on fig. 8). Groundwater levels in all five wells (fig. 25) followed the general trend 

of the stream stage (Nilges and Caldwell, 2012), but was lower 

than stream stage (losing conditions) from March through late 

May of both 2007 and 2008. Starting in late May (most apparent in the 2008 hourly record of well SR0609, fig. 26A and 

26B), groundwater levels rose abruptly and became higher than 

stream stage (gaining conditions). Specifically in well SR0609 

(fig. 26A and 26B), gradients went from having groundwater 

levels approximately 0.1 ft below the stream stage to a reversal 

of groundwater levels up to 0.55 ft above stream stage within 

5 days in May 2008. Groundwater levels declined to below 

stream stage (losing conditions) in late July to early August 

in both years. These periods of reversed gradients from losing to gaining conditions are coincident with periods of flood 

irrigation. Observations suggest flood irrigation contributed to 

increased local groundwater recharge, resulting in the rapid rise 

in groundwater levels and groundwater discharge to the stream.

The dynamic interaction of groundwater and surface 

water was observed in the temperatures at this site (Nilges and 

Caldwell, 2012). Temperatures measured below the streambed 

(example well SR0609 at 1.4 and 2.9 ft below the streambed, 

fig. 26C) followed the general trend of the stream through 

late May of both 2007 and 2008 suggesting an infiltration of 

stream water to a depth of at least 2.9 ft below the streambed. Starting in late May, temperatures below the streambed 

deviated from the stream and were distinctively cooler (fig. 

26C) and relatively dampened (fig. 26D) coincident with the 

gradient shift from slightly losing to strongly gaining conditions (figs. 26A and 26B). Temperatures measured below the 

streambed again followed that of the stream in late July to 

early August in both years, indicative of a return to losing 

conditions supported by the water level data.

Smith River below Newlan Creek (Groundwater 

and Surface-Water Monitoring Site 9)

Interpretation of data collected at three wells just 

upstream from the Smith River gaging station below Newlan 

Creek (station 06076560; site 9 on fig. 8) ranged from somewhat inconclusive to an indication of strongly gaining conditions. Instream well SR06A consistently indicated gaining 

conditions with groundwater levels that ranged up to approximately 0.6 ft above stream stage (Nilges and Caldwell, 2012). 

Indicative of gaining conditions, temperatures in the instream 

well SR06A at a depth of 2.05 ft below the streambed and 

well SR0601 installed in the left bank generally followed the 

trend of the stream, but were typically cooler than the stream 

and showed little diel variation during the summer (Nilges 

and Caldwell, 2012). The other instream well (SR0602) had 

water levels very near that of the stream and were probably 

within measurement uncertainty. A poor seal may have existed 

around the casing of instream well SR0602 as water level and 

temperature data did not indicate strongly gaining conditions.

Smith River above Rock Springs Creek 

(Groundwater and Surface-Water Monitoring 

Site 10)

Variable hydrologic characteristics and effects of local 

flood irrigation and ditch operation are apparent at the Smith 

River above Rock Springs Creek monitoring site (station 

06076580; site 10 on fig. 8). Groundwater levels in all five 

monitoring wells (fig. 27) followed the general trend of the 

stream stage (Nilges and Caldwell, 2012). However, conditions changed from gaining to losing several times during 

the record and interaction between groundwater and surface 

water appeared to vary between the left and right stream bank. 

Local flood irrigation on the right bank side of the stream at 

this location typically occurred two times per season (generally in the last half of June and then again in about early 

August). These irrigation periods are generally consistent with 

the period when groundwater levels rose above stream stage. 

Flood irrigation also occurs in places on the left side of the 

stream, but the timing was not reported.

Groundwater levels in well SR0605 (fig. 28A) (instream 

well near right bank) exhibited alternating gradients to and 

from the stream that were typically less than 0.2 ft in either 

direction and at times within measurement uncertainty (fig. 

28B). In comparison, water level data from well SR0606B 

(instream well near the left bank) exhibited gradients that 

sometimes differed in magnitude and direction from well 

SR0605 (fig. 28B). Most noticeably, measured gradients 

in well SR0606B were near neutral during 2008, whereas 

SR0605 had measured gradients of up to 0.20 ft during the 

same time period.

Temperature data at well SR0605 supports variable gaining and losing conditions. Temperatures below the streambed 

were typically cooler than the stream (fig. 28C) and showed 

little diel variation from June through August (indicative of 

a gaining reach) (fig. 28D), but more closely followed the 

stream trend and exhibited diel variations at other times (fig. 

28D). Temperature measured in the instream well near the 

left bank (SR0606B) followed the diel trend of the stream 

very closely (especially in 2008) throughout the record; the 

greater diel temperature variation and near-neutral hydraulic 

gradients (Nilges and Caldwell, 2012) indicates reduced or 

no groundwater flow to the stream at the left-bank side of the 

cross section.
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 59

Figure 25. Channel geometry, monitoring well network, and thermistor and/or pressure transducer locations at Smith River above 

Mud Springs Creek monitoring site (station 06075850). Groundwater altitudes and stream stage for April 30, 2008.

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_25.ai

Well SR0609

Groundwater altitudes—Inferred

 between wells

Monitoring well and identifier—

 Perforated near bottom

Altitude, in feet above North American Vertical Datum of 1988

Distance from left bank, in feet

EXPLANATION

Soil Instrument type

Thermistor

Upper instrumentation in

 monitoring well

Pressure transducer

Monitoring well installation

Lower instrumentation in

 monitoring well

Stream instrumentation

Stream instrumentation

Quaternary alluvium—Shallow

 near-streambed sediments

staff gage

Left bank

Smith River

Right bank

Well SR0610

 Well

SR0609

Well SR0611 Well SR0608

Well 

SR0609D

Stream stage April 30, 2008

Groundwater altitudes April 30, 2008

4,9180 5 10 15 20 25 30 35 40 45

4,924

4,920

4,926

4,922

4,928

4,930
60 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Figure 26. Data collected at the Smith River above Mud Springs Creek monitoring site (station 06075850). A, Altitude of stream 

stage and groundwater at well SR0609; B, Difference in hydraulic head between groundwater at well SR0609 and stream; C, Hourly 

temperature measurements of air at station 06075785, in stream at station 06075850, and in monitoring well SR0609 at depths of 

1.4 ft and 2.9 ft below the streambed; and D, Diel temperature variation in monitoring well SR0609 at depths of 1.4 ft and 2.9 ft below 

the streambed, March 2007 through December 2007 and March 2008 through December 2008. Stage or groundwater altitude, in feet above North American Vertical Datum 1988

4,828.2

4,828.0

4,830.0

4,828.4

4,828.6

4,828.8

4,829.0

4,829.2

4,829.4

4,829.6

4,829.8

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Difference between groundwater level in Well SR0609

and stream stage of station 06075850, in feet

-0.8

-1.0

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

2007

Month

2008

A

B

EXPLANATION

Smith River (station 06075850)—Manual measurement

SR0609 instream well—Manual measurement

Smith River (station 06075850)—Hourly measurements

SR0609 instream well—Hourly measurements

Losing Gaining

Note–Streambed bottom altitude at 4,827.5 feet

Hourly measurements

Line of zero difference

EXPLANATION

Manual measurement
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 61

Figure 26. Data collected at the Smith River above Mud Springs Creek monitoring site (station 06075850). A, Altitude of stream 

stage and groundwater at well SR0609; B, Difference in hydraulic head between groundwater at well SR0609 and stream; C, Hourly 

temperature measurements of air at station 06075785, in stream at station 06075850, and in monitoring well SR0609 at depths of 

1.4 ft and 2.9 ft below the streambed; and D, Diel temperature variation in monitoring well SR0609 at depths of 1.4 ft and 2.9 ft below 

the streambed, March 2007 through December 2007 and March 2008 through December 2008.—Continued

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_26B.ai

Dampened - indicative

of a gaining period

Temperature, in degrees celsius

EXPLANATION

EXPLANATION

-15

-20

-10

-5

0

5

10

15

20

25

30

35

0.0

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Diel temperature variation, in degrees celsius

-0.5

2007

Month

2008

C

D

0.5

1.0

1.5

2.0

3.0

2.5

Air at station 06075785

Smith River (station 06075850)

Well SR0609 at 1.4 feet below streambed

Well SR0609 at 2.9 feet below streambed

Well SR0609 at 1.4 feet below streambed

Well SR0609 at 2.9 feet below streambed
62 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Figure 27. Channel geometry, monitoring well network, and thermistor and/or pressure transducer locations at Smith River above 

Rock Springs Creek monitoring site (station 06076580). Groundwater altitudes and stream stage for May 9, 2007.

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_27.ai Altitude, in feet above North American Vertical Datum of 1988

Distance from left bank, in feet

EXPLANATION

Soil Instrument type

Thermistor

Upper instrumentation in

 monitoring well

Pressure transducer

Monitoring well installation

Lower instrumentation in

 monitoring well

Stream instrumentation

Stream instrumentation

Quaternary alluvium—Shallow

 near-streambed sediments

4,670

4,672

4,674

4,676

4,678

4,680

4,682

4,684

0 10 20 30 40 50 60 70

Smith River

staff gage

Well SR0605D

Well SR0607

Well SR0606B

Well SR0605

Well SR0604

Left bank

Right bank

Groundwater altitudes May 9, 2007

Stream stage May 9, 2007

Well SR0605

Groundwater altitudes—Inferred

 between wells

Monitoring well and identifier—

 Perforated near bottom
Groundwater and Surface-Water Interaction within the Upper Smith River Watershed 63

Figure 28. Data collected at the Smith River above Rock Springs Creek monitoring site (station 06076580). A, Altitude of stream stage 

and groundwater at well SR0605; B, Difference in hydraulic head between groundwater at wells SR0605 and SR0606B and stream; C, 

Hourly temperature measurements of air at station 06075785, in stream at station 06076580, and in monitoring well SR0605 at depths of 

1.6 ft and 3.1 ft below the streambed; and D, Diel temperature variation in monitoring well SR0605 at depths of 1.6 ft and 3.1 ft below the 

streambed, March 2007 through November 2007 and March 2008 through December, 2008.

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_28A.ai Stage or groundwater altitude, in feet above NAVD 1988

EXPLANATION

4,678.0

4,677.0

4,677.5

4,680.0

4,678.5

4,679.0

4,679.5

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Difference in hydraulic head between groundwater (measured

in SR0605 and SR0606B) and stream, in feet

-0.4

-0.5

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

2007

Month

2008

Well SR0605—Manual measurement

Well SR0605—Hourly measurements

Line of zero difference

Well SR0606B—Manual measurement

A

B

EXPLANATION

Smith River (station 06076580)—Manual measurement

SR0606B instream well—Manual measurement

SR0605 instream well—Manual measurement

Streambed bottom

Smith River (station 06076580)—Hourly measurements

SR0605 instream well—Hourly measurements

Losing Gaining
64 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Figure 28. Data collected at the Smith River above Rock Springs Creek monitoring site (station 06076580). A, Altitude of stream stage 

and groundwater at well SR0605; B, Difference in hydraulic head between groundwater at wells SR0605 and SR0606B and stream; C, 

Hourly temperature measurements of air at station 06075785, in stream at station 06076580, and in monitoring well SR0605 at depths of 

1.6 ft and 3.1 ft below the streambed; and D, Diel temperature variation in monitoring well SR0605 at depths of 1.6 ft and 3.1 ft below the 

streambed, March 2007 through November 2007 and March 2008 through December, 2008.—Continued

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_28B.ai Temperature, in degrees celsius

EXPLANATION

EXPLANATION

-15

-20

-10

-5

0

5

10

15

20

25

30

35

0.0

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Diel temperature variation, in degrees celsius

-0.5

2007

Month

2008

C

D

0.5

1.0

1.5

2.0

2.5

Air at station 06075785

Smith River (station 06076850)

Well SR0605 at 1.6 feet below streambed

Well SR0605 at 3.1 feet below streambed

Well SR0605 at 1.6 feet below streambed

Well SR06Q5 at 3.1 feet below streambed

Dampened - indicative

of a gaining period
Discussion 65

Simulation of Water and Heat Transport

Two-dimensional (2-D) fluid flow and energy (heat) 

transport VS2DH models (Healy, 2008; Healy and Ronan, 

1996; Hsieh and others, 2000) were developed for three stream 

cross sections on the basis of field surveys of channel geometry, stream stage, groundwater level, and temperature data in 

an effort to constrain hydraulic properties of the Quaternary 

alluvium. Detailed descriptions of the selected cross-section 

models constructed for this study, including boundary conditions and results, are included in appendix 2. 

Hydraulic properties selected for the final “best-fit” 

numerical models that most favorably matched observed 

conditions did show some variability among the cross sections 

and are summarized in table 9. While several parameters were 

held constant among the models (hydraulic conductivity of 

soil, dispersivity, and heat capacity), the vertical and horizontal hydraulic conductivity of the Quaternary alluvium ranged 

from 3x10-6 to 4x10-5 ft/s and porosity ranged from 0.30 to 

0.36. Although several ratios of horizontal to vertical hydraulic conductivity were evaluated for each model, it appears that 

a 1 to 1 ratio adequately represented the modeled systems, and 

varying ratios did not appreciably improve simulated results 

(see appendix 4). Three-dimensional groundwater-flow models 

and further refinement of the subsurface hydraulic characteristics would strengthen the understanding of these modeled 

sections.

Simulated Water Fluxes between Groundwater 

and Surface Water

The flow of water (water flux) across the streambed, 

bottom, and side boundaries of the cross-section models was 

calculated using results of the calibrated 2-D water heat and 

solute transport VS2DH models (appendix 3). Water flux 

calculated for each boundary represents the amount of water 

that flowed across the entire length of each boundary over a 

unit (1-ft) width.

The monthly mean flux across the streambed boundary 

for each cross-section was calculated by averaging all daily 

flux values for each day of a given month (table 10). The 

cumulative monthly flux in cubic feet per month (ft3/month) 

was calculated by summing each daily flux value in a given 

month across the entire streambed cross section. Positive flux 

values indicate groundwater flow to the stream, whereas negative flux values indicate flow from the stream to groundwater. 

When compared to seepage run data collected as part of the 

study (see discussion below), the numerical models showed 

reasonable approximations of the streambed and shallow aquifer environment near the stream cross sections, and dynamic 

changes in flux between the stream and the groundwater 

through different model boundaries.

Net gains calculated from the synoptic streamflow data 

at the South Fork Smith River near mouth (station 06075785) 

during periods of limited diversions (tables 5 through 7) 

ranged from 2.97 to 5.17 ft3/s (0.34 to 0.59 ft3/s per river mile) 

over the 8.7-mi length of the South Fork of the Smith River 

(river mile 11.8 to 3.1) that ends at the modeled cross section. Simulated flux values of 2.0 to 3.4 cubic feet per day 

(ft3/d) can be extrapolated to net gains of 0.12 to 0.21 ft3/s per 

river mile, assuming uniform stream width. Although water 

fluxes calculated at the modeled cross section were less than 

the average flux calculated from the synoptic measurements, 

estimates from these two methods are in general agreement, 

especially when taking into account that varying hydraulic 

characteristics, head gradients, and stream width are likely.

The simulated water flux at the North Fork Smith River 

near mouth (station 06075700; table 10) matched the direction 

of flow (losing) but failed to closely match fluxes calculated 

from the synoptic streamflow events (tables 5 through 7) during periods of limited diversion. Net losses calculated from 

synoptic streamflow data ranged from 2.40 to 7.97 ft3/s (0.89 

to 2.95 ft3/s per river mile) over the 2.7-mi length of the North 

Fork of the Smith River (Highway 360 bridge to near mouth) 

that ends at the modeled cross section. Simulated flux values 

ranging from near 0 to about 1.7 ft3/d (appendix 3, fig. 3-2) 

can be extrapolated to net losses of from near 0 to about 0.10 

ft3/s per river mile, assuming a uniform stream width. This 

difference suggests that losses are not uniform and that point 

scale measurements can vary greatly along the reach attributed 

to varying hydraulic characteristics and head gradients. 

A direct comparison of the simulated water flux with 

the synoptic streamflow events (tables 5 through 7) during 

periods of limited irrigation diversion was not possible at the 

Smith River above Mud Springs Creek cross section (station 

06075850; table 10) since modeled dates were not coincident with the synoptic streamflow measurements. Synoptic 

streamflow measurements indicated minimal net gains or gains 

that were less than measurement errors along the stream reach 

that ended at this cross section. Qualitatively, this differs from 

the simulated water flux during the spring and fall of 2008 and 

the corresponding temperature and head data, which indicated 

slightly losing conditions at this location. This difference suggests that water exchange direction and rate are not uniform 

along this reach of the Smith River.

Discussion

Groundwater and surface-water interactions between the 

Smith River, its tributaries, and the underlying aquifers exist 

throughout the entire Smith River watershed varying considerably with season and location. Collectively, data show the 

following: (1) the hydraulic connectedness of groundwater 

and surface water, (2) the presence of both losing and gaining stream reaches, (3) dynamic changes in direction and 

magnitude of water flow between the stream and groundwater 

with time, (4) the effects of flow alteration and irrigation on 

groundwater levels and gradients in the watershed, and (5) 

evidence and timing of irrigation return flows to area streams. 
66 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Hydraulic parameter

South Fork Smith 

River near mouth

(station 06075785)

North Fork Smith 

River near mouth

(station 06075700)

Smith River above 

Mud Springs Creek

(station 06075850)

Porosity 0.36 10.3 10.3

Hydraulic conductivity of near-streambed sediments, horizontal direction (ft/s) 3×10–6 3×10–6 4×10–5

Hydraulic conductivity of near-streambed sediments, vertical direction (ft/s) 3×10–6 3×10–6 4×10–5

Hydraulic conductivity of soil, horizontal and 

vertical directions (ft/s) 3×10–10 3×10–10 3×10–10

Dispersivity (ft) 20.03 20.03 20.03

Heat capacity of saturated sediments (W/ft oC) 20.6 20.6 20.6

Heat capacity of water at 20 oC (J/ft3 oC) 21.2×105 21.2×105 21.2×105

1

Based on Freeze and Cherry, 1979.

2

Based on Niswonger and Prudic, 2003.

Table 9. Summary of hydraulic parameters used in final calibrated VS2DH simulations of selected modeled 

cross sections in the upper Smith River watershed, Montana 

[ft/s, feet per second; ft, feet; oC, degrees Celsius; W/ft oC, Watts per foot degrees Celsius; J/ft3 oC, Joules per cubic foot 

degrees Celsius]

Monthly mean flow (ft3/d) Cumulative monthly flow (ft3/month)

Month

South Fork 

Smith River 

near mouth 

(station 

06075785)

North Fork 

Smith River near 

mouth (station 

06075700)

Smith River above 

Mud Springs 

Creek (station 

06075850)

South Fork 

Smith River 

near mouth 

(station 

06075785)

North Fork 

Smith River near 

mouth (station 

06075700)

Smith River above 

Mud Springs 

Creek (station 

06075850)

2007

May 2.77 –0.42 NM 85.95 –13.32 NM

June 2.74 –0.90 NM 82.19 –27.14 NM

July 2.30 –1.37 NM 71.15 –42.52 NM

August 2.25 –1.51 NM 69.66 –46.87 NM

September 2.66 –1.10 NM 79.71 –33.11 NM

October 2.54 –0.51 NM 78.74 –15.75 NM

November NM NM NM NM NM NM

2008

May 2.82 –0.62 –1.23 87.54 –19.29 –38.20

June 3.19 –0.22 7.41 95.68 –6.64 222.36

July 2.66 –0.61 7.48 82.35 –18.83 232.01

August 2.49 –0.82 –0.48 77.23 –25.50 –14.93

September 3.03 –0.10 –0.60 91.00 –2.93 –17.97

October 2.44 1–0.06 –0.54 75.59 1-1.82 –16.87

November 2.23 NM –0.41 66.84 NM –12.24

1

Based on 29 days.

Table 10. Summary of estimated water flow across streambed boundaries of the South Fork Smith River, North Fork 

Smith River, and Smith River modeled cross sections.

[Abbreviations: ft3/d, cubic feet per day; ft3/month, cubic feet per month; NM, not modeled; negative numbers indicate flow is from surface water to groundwater, positve numbers indicate flow is from groundwater to surface water. Note: flow values represent flow across a 

unit width (1-foot wide) of the modeled streambed]
Discussion 67

The effect of groundwater and surface-water interactions 

is most apparent along the North and South Forks of the Smith 

River where the magnitude of streamflow losses and gains 

can be greater than the magnitude of flow within the stream. 

Groundwater and surface-water interactions occur downstream 

from the confluence of the North and South Forks, but are less 

discernible compared to the overall magnitude of the mainstem streamflow. 

The North Fork Smith River begins in the Little Belt 

Mountains to the northwest of White Sulphur Springs and 

flows for nearly 40 mi to the southwest as it gains flow from 

tributaries originating in both the Little Belt and the Castle 

Mountains before joining the South Fork Smith River. Streamflow in this reach is highly managed at times through regulation at Lake Sutherlin (North Fork Smith River Reservoir) 

in the upper North Fork Smith River drainage and by diversions that supply water for both flood irrigation and sprinkler 

irrigation. During non-irrigation periods, North Fork Smith 

River streamflow measured below Spring Creek (about 8.4 

miles upstream from the confluence with the South Fork Smith 

River) ranged from 12.4 ft3/s to 16.4 ft3/s. Leakage to groundwater and diversions along the 5.8-mile downstream reach 

ranged from 2.23 ft3/s to 8.49 ft3/s during the non-irrigation 

season. Releases from Lake Sutherlin increased during periods 

of irrigation. North Fork Smith River streamflow below Spring 

Creek was 72.5 ft3/s measured during a seepage run in August 

2007. Diversions and leakage to groundwater along the 5.8-

mile downstream reach measured during this time accounted 

for about 67.6 ft3/s of streamflow losses. 

The South Fork Smith River begins in the Castle Mountains and flows to the west and northwest for about 38 mi. 

The South Fork Smith River gains flow from tributaries 

originating from both the Castle and Big Belt Mountains and 

from an unsealed artesian well near its headwaters. Unlike 

the North Fork Smith River, the South Fork Smith River has 

limited reservoir capacity. Streamflow near the mouth was 

typically less than 10 ft3/s for most of the year after the spring 

snowmelt. The lower 15-mile reach of the South Fork Smith 

River showed an overall net gain during the entire study, with 

measured gains in streamflow ranging from 0.13 ft3/s to 9.33 

ft3/s. However, individual sections of the South Fork Smith 

River varied from gaining to losing. Streamflow approached or 

achieved no-flow conditions along a section of the South Fork 

Smith River near river mile 11.8 during the summer irrigation 

seasons as a result of streamflow losses to irrigation withdrawals, evapotranspiration, and infiltration. Flow returned 

downstream primarily due to groundwater discharge (gaining 

conditions) to the river. 

Groundwater discharge occurred along the uppermost 

reach of the Smith River and the lower extents of the North 

Fork Smith River and South Fork Smith River throughout 

the study. Conditions ranged from losing to gaining below 

river mile 122.2 (122.2 miles upstream from the Smith River 

confluence with the Missouri River) until river mile 80.8 at 

the Smith River below Eagle Creek streamflow-gaging station 

(station number 06077200); however, these gains and losses 

were minor (less than about 15 percent) compared to tributary 

inflow and main-stem streamflow. The average annual streamflow measured at Smith River below Eagle Creek streamflowgaging station (station number 06077200) was 244 ft3

/s 

(2005–2010). About 33 percent (81 of 244 ft3/s) of the Smith 

River streamflow measured below Eagle Creek can be attributed to contributions from the drainage area upstream from the 

Smith River below Newlan Creek streamflow-gaging station at 

river mile 112.1 which includes inflow from North and South 

Forks of the Smith River, Birch Creek, and Newlan Creek. 

The drainage area between the Smith River below Newlan 

Creek (station 16076560) and Smith River below Eagle Creek 

(station 06077200) streamflow gaging stations contributed 

about 67 percent (143 ft3/s) of the total streamflow observed at 

the Smith River below Eagle Creek. Sheep Creek accounts for 

much of the 143 ft3/s streamflow increase in the Smith River 

between river miles 112.1 and 80.8.

At about river mile 80.8 (below the mouth of Eagle 

Creek), the Smith River flows through steep-sided canyons 

for nearly 60 mi. This reach is characterized by its natural 

setting and minimal disturbance from human development. 

Streamflow in this reach is supported by the main-stem inflow 

entering the canyon and the natural tributary inflow. The mainstem inflow is dependent upon upstream management whereas 

tributary inflow is predominantly unmanaged. There are 

minimal retention reservoirs or diversions within this part of 

the system. As the least managed reach, variability in streamflow within this reach is primarily dependent upon climate and 

weather conditions. 

Data from the streamflow-gaging stations above (Smith 

River below Eagle Creek - station 06077200, continuous operation) and below (Smith River near Eden -station 06077500, 

seasonal operation) the 60-mi long canyon reach indicate a 

median streamflow increase of 58 ft3/s (23 percent) when both 

streamflow-gaging stations were in operation between March, 

2006 and October, 2010. Although there are several tributaries 

along this 53.8-mi reach of the Smith River, there were periods 

when streamflow remained nearly identical or even decreased 

between the upstream and downstream stations. Travel times 

affect these observations, but streamflow is affected by gains 

and losses along this section of the Smith River as it travels 

through the steep-sided limestone canyon. While there were 

losses from the stream to the underlying aquifers, perennial 

conditions were observed along the entire reach. 

Short time spans occurred between the application of 

diverted water for flood irrigation and the resulting effects to 

the local hydrologic flow system. Wide-spread flood irrigation occurred in May through June, and sometimes occurred 

again in the late-summer to early-fall. Irrigation and conveyance water that is not evaporated or consumed by plants can 

return to the stream as groundwater return flows or through 

drainage ditches downstream from where the water was 

diverted. Hydraulic gradients increased or reversed direction 

(changed from losing to gaining) at several monitoring sites 

coincident with the timing of nearby flood irrigation. Some 

of these hydraulic gradient shifts occurred within days of 
applied irrigation with the timing dependent upon the distance 

between the irrigated fields and the observation wells and 

stream gages. 

The time it takes for the actual applied water to reach 

the stream is dependent upon the length of the groundwater 

flow path, hydraulic gradients, and aquifer characteristics. In 

reality, the actual travel time for the applied water to reach the 

stream could be several days or even months. For example, 

the continuous streamflow record of several tributaries and 

the main stem Smith River at the streamflow-gaging station 

below Newlan Creek (06076560) during the 2010 irrigation 

illustrated the timing and magnitude of net irrigation return 

flows in the area. Tributary inflow upstream from the Smith 

River streamflow-gaging station below Newlan Creek nearly 

matched outflow at this gage during the last two weeks of May 

2010, coincident with the timing of high diversion rates and 

extensive flood irrigation. This was followed by a month-long 

period (early June 2010 through early July 2010) with the 

largest net increase in streamflow at the Smith River streamflow-gaging station below Newlan Creek relative to tributary 

inflow. This observation is the result of groundwater discharge 

to the Smith River due to irrigation return flow. The remaining 

continuous record (April through September 2010) shows a 

nearly stable net increase of flows of about 25 ft3/s. 

Summary

The Smith River watershed encompasses approximately 

2,000 mi2 of the upper Missouri River Basin in Meagher and 

Cascade Counties of west-central Montana. The 125-milong Smith River, a tributary of the Missouri River, is highly 

valued as an important agricultural resource and for its many 

recreational uses. Nearly 35,000 acres of the Smith River 

watershed are irrigated, primarily using water directly withdrawn from the Smith River and its tributaries. During a recent 

drought starting in about 1999, streamflow was not sufficient 

to meet all of the irrigation demands much less maintaining 

instream flow requirements to support viable fish habitat and 

recreational activities. In 2006, the U.S. Geological Survey 

(USGS), in cooperation with the Meagher County Conservation District (MCCD), initiated a multi-year hydrologic 

investigation of the Smith River watershed designed to expand 

the knowledge of the hydrologic system through a systematic 

program of data compilation and collection, research, and 

analysis. Although study efforts included the entire watershed, the majority of data-collection efforts took place in an 

approximately 1,200 mi2 focus area in the upper Smith River 

watershed.

The objective of this component of the Smith River 

watershed hydrologic investigation was to provide an 

increased understanding of the water resources of the Smith 

River watershed, including a detailed description of groundwater and surface-water interactions. Specifically, the description would include the delineation of gaining and losing 

reaches of the Smith River and selected tributaries, quantification of gains and losses during different hydrologic conditions, 

and the relation between groundwater levels and stream stage.

The most productive and developed aquifers in the Smith 

River watershed are the alluvium and Tertiary basin-fill sediments of the valley lowlands and tributary drainages. The alluvial aquifers are generally composed of sand and gravel with 

varying clay layers. The basin-fill aquifers are generally fine 

grained with lower permeability. However, some of the most 

productive wells produce water from the basin-fill sediments. 

Wells within older sedimentary and igneous rocks in the area 

are typically of low yield and are utilized for domestic and 

stock purposes. Potentiometric surface maps were generated 

from water-level measurements of area wells and stream stage 

during March 2007, August 2007, October 2007, and April 

2008. Groundwater-flow direction generally followed landsurface topography from the uplands to the axis of alluvial 

valleys of the Smith River and its tributaries. Flow to and from 

the surface water was apparent, especially at the lower ends of 

the North Fork Smith River and the South Fork Smith River, 

as well as at the upper reach of the main stem of the Smith 

River. Groundwater gradients ranged from approximately 10 

ft/mi to 50 ft/mi in the upper Smith River valley.

Daily streamflow at all four long-term USGS streamflowgaging stations on the Smith River showed similar trends, with 

high flows typically occurring in the spring to early summer 

and more stable, moderate to low flows occurring from midsummer through early spring. Streamflow typically increased 

in downstream order – primarily due to tributary and net 

groundwater inflow. A review of continuous daily streamflow 

records for water years 2005 through 2010 indicated a mean 

annual increase of 163 ft3/s between the uppermost streamflow-gaging station below Newlan Creek (river mile 112.1, 

station 06076560) and the streamflow-gaging station below 

Eagle Creek (river mile 80.8, station 06077200). The upper 

517 mi2 of the watershed, represented by the USGS streamflow-gaging station at the Smith River below Newlan Creek, 

contributed about 33 percent of the total flow observed at the 

Smith River below Eagle Creek streamflow-gaging station.

Three separate single-day, synoptic streamflow measurements (seepage runs) were conducted during periods of 

limited irrigation diversion (March 22, 2007; October 16, 

2007; and April 10, 2008) at up to 45 main stem and tributary 

sites within the upper Smith River watershed. The exchange 

of groundwater and surface water was quantitatively estimated 

by examining the net differences between measured sections 

of the main stem and accounting for tributary inflow and 

diversions. Net gains ranging from 2.44 to 9.33 ft3/s were measured over the lower 14.9 mi of the South Fork Smith River. 

The North Fork Smith River had net losses ranging from 

2.23 to 8.49 ft3/s over the lower 8.1-mi reach. Overall, net 

gains (flow from the groundwater to the surface water) were 

observed over the upper 41.4 river miles of the Smith River 

that ranged from 13.0 to 28.9 ft3/s.

68 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed
References Cited 69

4x10-5 ft/s. The models showed reasonable approximations 

of the streambed and shallow aquifer environment near the 

stream cross sections. Three-dimensional groundwater-flow 

models and further refinement of the subsurface hydraulic 

characteristics would strengthen the understanding of these 

modeled sections.

The use of multiple methods of investigation increased 

the understanding of the flow system and the interaction of 

groundwater and surface water within the upper Smith River 

watershed. Results from this study have shown the following: (1) groundwater and surface are hydraulically connected 

along the Smith River and its tributaries; (2) both losing 

and gaining stream reaches occur throughout the area; (3) 

dynamic changes in the direction and magnitude of water flow 

between the stream and groundwater with time; (4) local flood 

irrigation effects groundwater levels and gradients; and (5) 

local flood irrigation results in irrigation return flows to area 

streams. 

References Cited

Bureau of Reclamation, 2007, AgriMet Weather Data—Great 

Plains cooperative agricultural weather network: Bureau of 

Reclamation, accessed February 8, 2013, at http://www.usbr.

gov/gp/agrimet/station_wssm_whitesulphur.cfm.

Bureau of Reclamation, 2008, AgriMet Weather Data—Great 

Plains cooperative agricultural weather network: Bureau of 

Reclamation, accessed February 8, 2013, at http://www.usbr.

gov/gp/agrimet/station_wssm_whitesulphur.cfm.

Cannon, M.R., and Johnson, D.R., 2004, Estimated water 

use in Montana in 2000: U.S. Geological Survey Scientific 

Investigations Report 2004-5223, 50 p.

Constantz, Jim, 2008, Heat as a tracer to determine stream 

water exchanges: Water Resources Research, v. 44, 

W00D10, doi:10.1029/2008WR006996, 20 p.

Constantz, J., and Stonestrom, D.A., 2003, Heat as a tracer 

of water movement near streams, p. 1-6, in Stonestrom, 

D.A., and Constantz, J., eds,, Heat as a tool for studying the 

movement of ground water near streams: U.S. Geological 

Survey Circular 1260, 96 p.

Eddy-Miller, C.A., Wheeler, J.D., and Essaid, H. I., 2009, 

Characterization of interactions between surface water and 

near-stream groundwater along Fish Creek, Teton County, 

Wyoming, by using heat as a tracer: U.S. Geological Survey 

Scientific Investigations Report 2009-5160, 53 p.

Essaid, H.I., Zamora, C.M., McCarthy, K.A., Vogel, J.R., and 

Wilson, J.T., 2008, Using heat to characterize streambed 

water flux variability in four stream reaches: Journal of 

Environmental Quality, v 37, p. 1010-1023.

Groundwater levels at 10 groundwater/surface-water 

monitoring sites were typically the highest in the late spring 

to early summer (late May through early July), fell during 

the summer (July to early August), and then recovered during the late summer through the fall of both 2007 and 2008. 

High groundwater levels in the near-stream wells in the late 

spring or early summer were affected by increased recharge 

from snowmelt, local precipitation, high stream flows, and 

local flood irrigation at some locations. Summer declines in 

groundwater levels can be associated with reduced recharge 

from less precipitation and local flood irrigation, local and 

regional effects of groundwater withdrawals, increased ET, 

and reduced streamflow and subsequent leakage in some area 

streams. Groundwater levels rebounded during mid-August 

to mid-September at most sites as a result of decreases in 

groundwater use (irrigation), increased flow in losing streams, 

decreased ET, and the onset of local flood irrigation at some 

sites. Head gradients at six of the monitored sites reversed 

direction at times during the course of the study. Many sites 

showed gradients from one stream bank to the other.

The groundwater/surface-water monitoring network sites 

exhibited variable gaining and losing conditions during the 

study. Two sites along the South Fork Smith River ranged 

from gaining at times to losing as groundwater levels declined 

during the summer months. Groundwater levels rebounded in 

the late summer to early fall. Groundwater levels fell below 

the streambed during the summer months at one South Fork 

Smith River site and the stream became dry for a short period 

in 2008. Near its mouth, the South Fork Smith River demonstrated strongly gaining conditions, with head gradients toward 

the stream and stream temperature dampened by the inflow 

of cooler groundwater during the summer. A site on the lower 

North Fork Smith River demonstrated losing conditions over 

most of the record, with groundwater levels well below stream 

stage and groundwater temperatures that closely matched 

those of the stream (indicative of advective flow of heat from 

the stream to the groundwater).

Hydrologic responses to local groundwater recharge 

from local flood irrigation occurred at several groundwater/

surface-water monitoring network sites. Groundwater levels 

increased at these sites coincident with the timing of local 

flood irrigation. Also coincident with observed local flood 

irrigation, water temperatures measured in the monitoring 

wells at depth below the streams went from closely following 

stream temperatures to diverging from the surface-water trend 

as groundwater discharge increased to the stream. Gradients 

at one Smith River cross section went from having groundwater levels approximately 0.1 ft below the stream stage to a 

reversal of groundwater levels up to 0.6 ft above stream stage 

within 5 days.

Two-dimensional heat and solute transport VS2DH 

models constructed for selected stream cross sections focused 

on sites with observed distinctions between temperature and 

head data in an effort to constrain hydraulic properties of the 

Quaternary alluvium. Hydraulic conductivity of the Quaternary alluvium of the modeled sections ranged from 3x10-6 to 
70 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Farnes, Phil, 2007, 1971–2000 Average Annual Precipitation, 

Meagher County, Montana: Montana State Library Natural 

Resource Information System, Map Request 07NRCS0020, 

map scale 1:250,000, 1 sheet.

Fenneman, N.M., and Johnson, D.W., 1946, Physical divisions of the United States: U.S. Geological Survey, scale 

1:7,000,000, 1 sheet.

Freeze, R.A., and Cherry, J.A., 1979, Groundwater: Englewood, N.J., Prentice Hall, Inc., 604 p.

Groff, S.L., 1965, Reconnaissance groundwater and geological studies, western Meagher County, Montana: Montana 

Bureau of Mines and Geology, Special Publication 35, 

Ground-Water Report 3, 23 p.

Healy, R.W., 2008, Simulating water, solute, and heat transport 

in the subsurface with the VS2DI Software Package: Vadose 

Zone Journal, v. 7, no. 2, p. 632–639.

Healy, R.W., and Ronan, A.D., 1996, Documentation of computer program VS2DH for simulation of energy transport 

variably saturated porous media—Modification of the 

U.S. Geological Survey’s computer program VS2DT: U.S. 

Geological Survey Water-Resources Investigations Report 

96-4230, 36 p.

Heath, R.C., 1983, Basic ground-water hydrology: U.S. Geological Survey Water-Supply Paper 2220, 84 p.

Hsieh, P.A., Wingle, W.L., and Healy, R.W., 2000, VS2DI—

A graphical software package for simulating fluid flow 

and solute or energy transport in variably saturated porous 

media: U.S. Geological Survey Water-Resources Investigations Report 99–4130, 16 p.

Lohman, S.W., 1979, Ground-water hydraulics: U.S. Geological Survey Professional Paper 708, 70 p.

Montana Bureau of Mines and Geology, 2011, Groundwater 

Information Center (GWIC) database, accessed February 

15, 2011, at http://mgmggwic.mtech.edu/. 

Montana Department of Natural Resources and Conservation , 2003, Smith River basin permit and change applications supplemental environmental assessment: Montana 

Department of Natural Resources and Conservation, Water 

Resources Division, Helena, MT, 78 p.

Montana Natural Resource Information System, 2010, 

Digital Atlas of Montana, accessed September 21, 2010, 

at http://maps2.nris.mt.gov/mapper/.

National Climatic Data Center, 2011, Annual Climatological 

Summary, accessed November 17, 2011 at http://cdo.ncdc.

noaa.gov/ancsum/ACS?coban=248930.

Nilges, H.L. and Caldwell, R.R., 2012, Hydrologic data for the 

Smith River watershed, Montana, through water year 2010: 

U.S. Geological Survey Open-File Report 2012–1134, 41 p.

Niswonger, R.G., and Prudic, D.E., 2003, Modeling heat 

as a tracer to estimated streambed seepage and hydraulic 

conductivity, in Stonestrom, D.A. and Constantz, J., eds., 

Heat as a tool for studying movement in ground water near 

streams: U.S. Geological Survey Circular 1260, p. 81–89.

Nolan, K.M. and Shields, R.R., 2000, Measurement of stream 

discharge by wading: U.S. Geological Survey WaterResources Investigations Report 00-4036, on CD-ROM.

Oregon State University PRISM Group, 2006, United States 

Average or Annual Precipitation, 1971–2000: Corvallis, 

Oregon State University, accessed March 31, 2009 at 

http://www.prism.oregonstate.edu/.

Rantz, S.E., and others, 1982, Measurement and computation 

of streamflow: U.S. Geological Survey Water-Supply Paper 

2175, 2 v. 631 p.

Ross, C.P., Andrews, D.A., and Witkind, J.A., compilers, 

1955, Geologic map of Montana: U.S. Geological Survey, 

2 sheets, scale 1:500,000.

Runkel, A.C., 1986, Geology and vertebrate paleontology of 

the Smith River basin, Montana: Unpublished Master’s 

thesis, University of Montana, 80 p.

Sauer, V.B., and Meyer, R.W., 1992, Determination of error in 

individual discharge measurements: U.S. Geological Survey 

Open-File Report 92–144, 21 p.

Turnipseed, D.P., and Sauer, V.B., 2010, Discharge measurements of gaging stations: U.S. Geological Survey Techniques and Methods, book 3, chap. A8, 87 p.

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accessed January 17, 2012 at 

http://maps2.nris.mt.gov/mapper/MapWindow.asp?Profile=

2006737&Cmd=Build+Reports.

U.S. Geological Survey (USGS), 2000, National Land Cover 

Data for Montana, Vector Format, accessed 3/16/2009 at 

http://nris.mt.gov/nsdi/nris/nlcd/nlcdvector.asp.

U.S. Geological Survey (USGS), 2010. National Hydrography 

Dataset, accessed September 22, 2010 at http://nhd.usgs.

gov/index.html.
Appendixes
Groundwater sites (wells) are assigned a 15-digit site 

identification number; these numbers represent the approximate latitude and longitude of the site (first 13 digits) plus a 

sequence number (last 2 digits). Wells used for this study were 

also assigned a station name based on their geographic position within the rectangular grid system used for the subdivision of public lands (fig. 1-1). The station name consists of 

14 characters. The first three characters specify the township 

and its position north (N) of the baseline in Montana (for 

example, 09N). The next three characters specify the range 

and its position east (E) of the principal meridian in Montana 

(for example, 05E). The next two numbers represent the section number. The next four characters sequentially designate 

the quarter (160-acre tract), quarter-quarter (40-acre tract), 

quarter-quarter-quarter (10-acre tract), and the quarter-quarterquarter-quarter (2 1⁄2-acre tract) of the section in which the well 

lies. The quarter subdivisions within a section are designated 

A, B, C, and D in a counterclockwise direction, beginning in 

the northeast quadrant. The final two characters of the station 

name are a sequence number assigned to differentiate multiple 

wells within a single quarter-quarter-quarter-quarter section. 

For example, as shown in figure 1-1, 09N05E18BBAC01 was 

the first well inventoried in the SW1/4 of the NE1/4 of the 

NW1/4 of the NW1/4 of sec. 18, T. 09N., R. 05E. 

Streamflow-gaging stations are typically assigned an 

eight-digit station identification number that represents the 

standard USGS numbering system for streamflow-gaging 

stations. Miscellaneous surface-water measurement sites are 

assigned a fifteen-digit station identification number similar to 

the site identification number of the groundwater sites. These 

numbers represent the approximate latitude and longitude of 

the site (first 13 digits), plus a sequence number (last 2 digits). 

Streamflow-gaging stations and miscellaneous surface-water 

measurement sites were also assigned a station name based on 

their geographic position relative to landmarks.

Appendix 1. Site-Identification Systems

Figure 1-1. Location-numbering system for wells.

WELL 09N05E18BBAC01

9

1S

1N

2

3

4

5

6

7

8

9

10

8 7 6 5

36

35

34

33

32

31

25

26

27

28

29

30

24

23

22

21

20

13

14

15

16

19

17

12

11

10 9 8 7

1 2 3 4 5 6

D C

D

A B

D C

A

A

D

B

C

B

A B

D C

C

A B

5 6 4 4 3 3 2 2 1E 1W

RANGE

RANGE 5 EAST

SECTION 18

TOWNSHIP 9 NORTH

TOWNSHIP

Principal

Meridian

Base

Line

72 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed
Appendx 2 73

Each two-dimensional fluid flow and energy (heat) 

transport VS2DH model for this study was constructed in a 

simplistic manner with consistent methodology for specifying 

boundary conditions. The grid system and boundary conditions representing the stream banks and stream bottom were 

similar among the models. All model grids were specified as 

uniform, 100 by 100 cell systems. Cell dimensions were 0.1 ft 

vertically and 0.3 to 0.4 ft horizontally. Average air temperature was used as the specified-temperature boundary representing the effects of soil temperature on groundwater and was 

applied to the area representing the stream banks (fig. 2-1) 

labeled soil. Streambeds were represented as specified-head 

and specified-temperature boundaries using measured water 

levels and stream temperature. 

The side and bottom boundaries of each cross-sectional 

model are not hydrologic or flow-system boundaries. Boundaries on the left and right sides of the models were represented 

as specified head and specified-temperature boundaries using 

data from the monitoring wells located on each stream bank. 

Bottom boundaries were represented as specified-head and 

specified-temperature. The geometry of the bottom boundaries 

were based on a line that connected the lower-most data points 

(for example, the depth of the monitoring wells on each stream 

bank). The hydraulic properties of the Quaternary alluvium 

(for example, the vertical hydraulic conductivity, horizontal 

hydraulic conductivity, and porosity) were spatially uniform 

within the modeled area.

Appendix 2. Cross-Sectional Model Descriptions and Results

Figure 2-1. Boundary conditions and observation points for the VS2DH model, South Fork Smith River near mouth (station 06075785) 

monitoring site cross section.

Well SF0602

Well SF0604

Well SF0601

Well SF0603

SF0601-4.15 feet

SF0603-3.15 feet

SF0601-4.15 feet

South Fork Smith River

∆Z =0.1 feet

∆Z

∆X =0.4 feet

∆X

SF0601 and SF0603 average 

water level and temperature at 

lower thermistors

SF0603-1.65 feet

Air

SF0602-2.67 feet

SF0604-3.18

feet

SF0604-4.68

feet

SF0601- 2.67 feet

Air

SF0602-4.15 feet

42 feet

5.8 feet

1.5 feet

0.6 feet

4.4 feet

EXPLANATION

Soil—general soil hydraulic properties

 (table 9)

Specified-head and specified

 temperature boundary

Quaternary alluvium—Near-

 streambed sediments (table 9)

Horizontal discretization

Vertical discretization

Model observation point

Model boundary end point

Specified-temperature boundary

No specified head or temperature

 at boundary

Well SF0601

Monitoring well and identifier

Observation well and approximate thermistor

 depth below streambed or land surface-data

 used for boundary input and model observation
74 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

South Fork Smith River near Mouth

The South Fork Smith River near mouth (station 

06075785) modeled cross section (site 3, fig. 8; fig. 2-1) is 

located on a gaining reach of the stream as apparent from 

the synoptic streamflow, water level, and temperature data. A 

2-D model of the cross section was developed for the period 

of April 30 to November 30, 2008. The model configuration 

that most closely matched the simulated versus observed data 

was then run using data collected from April 21 to November 

7, 2007 to determine if the selected parameters would yield 

acceptable data for a year with different hydrologic events.

The physical design of the VS2DH model is shown in 

figure 2-1. Temperature and water-level data from the stream 

bank wells (SF0604 and SF0602) were used for the specifiedhead and specified-temperature at the far left and right boundaries (fig. 2-1). The bottom boundary was divided into five 

segments. The far left and right segments (half the distance 

between the bank wells and the instream wells) were represented by using water level data from the left and right stream 

bank wells and temperature data from the deep thermistors 

(SF0604-4.68 ft and SF0602-4.15 ft) which were located about 

3.0 ft below the stream bottom. The remaining three segments 

of the bottom boundary were represented by using water level 

and temperature data from the instream wells near the left 

(SF0603-3.15 ft) and near the right (SF0602-4.15 ft) banks. 

The central segment was represented by using the average of 

the water level and temperature data from the deeper thermistors of the two instream wells. Daily temperature values from 

SF0602-4.15 ft were substituted for missing (September 11, 

2008 through November 30, 2008) data from SF0601-4.15 ft. 

The SF0602-4.15 ft data appear to be a reasonable replacement for the missing SF0601-4.15 ft data since measured differences between the two sites were less than 0.4oC between 

April 30 and September 10, 2008.

Calibration of South Fork Smith River near mouth (station 06075785) cross sectional model proved difficult using 

a simple homogeneous characterization of the Quaternary 

alluvium. Of the cross sections simulated, results from this 

site had the poorest fit between the observed and simulated 

data. The best matches between the observed 2008 data and 

simulated values occurred with saturated hydraulic conductivity values of 3x10-6 ft/s in both the horizontal and vertical 

directions (table 9, fig. 2-2).

Relatively cool 2007 summertime stream temperatures 

(cooler than average air temperature and streambed sediment measured in the monitoring wells) at this cross section 

indicated a component of the flow system that could not 

be represented accurately with the VS2DH model and the 

available data. The cool summertime stream temperatures 

were an indication of either the discharge of cool groundwater upstream from the cross section or an inflow of cooler 

groundwater that discharged into the stream through the 

unmonitored central part of the streambed. Temperatures near 

the stream banks, measured about 1.5 ft below the streambed, 

were warmer than stream temperatures, whereas temperatures 

in the deeper thermistors (about 3.0 ft below the streambed) at 

those wells were near that of the stream. Potentially, temperatures measured at the shallow near-bank thermistors (about 

1.5 ft below the streambed) indicate a component of shallow 

groundwater discharge to the stream (possibly local return 

flow from irrigation) that generally follows the trend of the 

local air temperature. A plausible explanation for the observed 

data would be that cooler groundwater at similar temperatures 

to the deeper thermistors (about 3.0 ft below the streambed) 

was upwelling under the central part of the stream. A monitoring well under the central part of the stream would have aided 

in this interpretation.

North Fork Smith River near Mouth

The North Fork Smith River near the mouth (station 

06075700) cross section (site 4, figs. 8 and 2-3) is on a primarily losing reach of the stream as apparent from water level, 

temperature, and synoptic streamflow data. A 2-D model of 

the cross section was developed for the period of April 26 to 

November 6, 2007. Groundwater levels at and near the stream 

banks indicated that unsaturated conditions between the 

streambed and the groundwater may occur at times, especially 

during 2007 (Nilges and Caldwell, 2012). The hydrologic 

conditions (saturated or unsaturated) near the center of the 

stream were unmeasured; therefore, it is possible that the 

saturated conditions did occur near the center of the stream but 

not along the banks. Unsaturated conditions affect the thermal conductivity of the sediment underlying the stream. The 

cross section was simulated as though saturated conditions 

existed. Differences in the observed versus simulated temperature values may be a result of the periods of unsaturated 

conditions (see below). The model configuration that most 

closely matched the simulated versus observed data was then 

run using data from a second season (April 30 to November 

6, 2008) to determine if the selected parameters would yield 

acceptable data for a year with different hydrologic events.

The physical design of the VS2DH cross-sectional model 

of the North Fork Smith River near mouth is shown in figure 

2-3. The uppermost specified-head and specified-temperature 

on the far left and right boundaries used temperature and 

water-level data from the stream bank wells. The bottom 

boundary was split into three segments. The entire bottom 

boundary utilized temperature data from a nearby stock well 

at a depth 10 ft below land surface. The bottom-boundary 

segments near the left and right sides were represented by the 

specified-head data from wells on the left (NF0604) and right 

(NF0601) banks. The middle third of the bottom specifiedhead boundary was set equal to the average of the stream bank 

wells. The temperature boundary conditions at the lower left 

and right boundaries (depths deeper than thermistors in the 

NF0601 and NF0604 wells) were calculated by averaging 

the temperatures of the stock well and the lower thermistors 

(depths of about 3 ft below the streambed) in the bank wells 

(NF0601 and NF0604).
Appendix 2 75

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_31.ai

EXPLANATION

EXPLANATION

EXPLANATION

EXPLANATION

2

4

6

8

10

12

14

South Fork Smith River

Well SF0601—2.67 feet below streambed, observed

Well SF0601—2.67 feet below streambed, simulated

2 Apr. May June July Aug. 2007 Sept. Oct. Nov.

4

6

8

10

12

14

Temperature, in degrees celsius 

South Fork Smith River

Well SF0603—1.65 feet below streambed, observed

Well SF0603—1.65 feet below streambed, simulated

2

4

6

8

10

12

14

South Fork Smith River

Well SF0601—2.67 feet below streambed, observed

Well SF0601—2.67 feet below streambed, simulated

2 Apr. May June July Aug.

2008

Sept. Oct. Nov.

4

6

8

10

12

14

Temperature, in degrees celsius 

South Fork Smith River

Well SF0603—1.65 feet below streambed, observed

Well SF0603—1.65 feet below streambed, simulated

Figure 2-2. Observed and simulated temperature for the South Fork Smith River near mouth monitoring site (station 06075785), 2007 

and 2008. (Horizontal and vertical hydraulic conductivities were set at 3x10-6 feet per second.)
76 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Comparisons between the simulated and measured 

temperatures at the observation points for different hydraulic 

conductivities determined the best matches for both the 2007 

and 2008 data occurred with saturated hydraulic conductivity 

equal to 3x10-6 ft/s in both the horizontal and vertical direction (table 9, fig. 2-4). In most simulations, the right bank side 

(observation points NF0602-1.42ft and NF0602-2.92 ft) had 

observed temperatures closer to the simulated temperatures 

than on the left bank side. The greatest differences between 

observed and simulated temperatures occurred when groundwater levels fell below the streambed, especially for the 

temperature observations from the well near the left stream 

bank in 2007. The close match of observed and simulated 

temperatures on the right bank side indicates that flow from 

the stream to the groundwater is primarily within or parallel to 

the 2-D cross section and likely indicates (1) that conditions 

remained saturated or nearly saturated at that side, and (2) a 

greater quantity of water moved from the stream to the right 

bank side than from the stream to the left bank side. Water 

temperatures in the left bank well were typically cooler and 

the least dynamic (Nilges and Caldwell, 2012) which is likely 

associated with less leakage from the stream at that location.

Smith River above Mud Springs Creek

The Smith River above Mud Springs Creek (station 

06075850) cross section (site 8, figs. 8 and 2-5) is on a reach 

of the stream that varied between losing and gaining conditions as indicated by the water level and temperature data. A 

2-D model of the cross section was developed for the period 

of May 1 to November 30, 2008. The 2007 period was not 

simulated due to the lack of continuous stream stage data. The 

physical design of the VS2DH model is shown in figure 2–5. 

The specified-head and specified-temperature on the far left 

and right boundaries used temperature and water-level data 

Figure 2-3. Boundary conditions and observation points for the VS2DH model, North Fork Smith River near mouth (station 06075700) 

monitoring site cross section.

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_32.ai

Well NF0603

Well NF0603

Well NF0604

Well NF0601

Well NF0602

North Fork Smith River

NF0603-1.60 feet

Air

NF0602-1.42 feet

Air

North Fork Smith River

NF0604 water level -

temperature average

of NF0604 -4.39 feet and 

stock well at 10.0 feet

NF0604 - 2.89 feet

NF0604 - 4.39 feet

NF0601 - 2.75 feet

NF0601- 4.25 feet

1.0 feet

NF0603-3.10 feet

9.0 feet

0.5 feet

NF0602-2.92 feet

NF0601 water level -

temperature average

of NF0601 -4.25 feet and

stock well at 10.0 feet

Air

9.0 feet

NF0604 water level -

temperature from

stock well at 10.0 feet

NFO601 and NF0604 average water level - 

temperature from stock well at 10.0 feet

NF0601 water level -

temperature from

stock well at 10.0 feet

NF0601-4.25 feet

∆Z =0.1 feet

∆Z

∆X =0.4 feet

∆X

37 feet

EXPLANATION

General soil hydraulic properties

 (table 9)

Specified-head and specified

 temperature boundary

Monitoring well and identifier

Quaternary alluvium—Near-

 streambed sediments (table 9)

Horizontal discretization

Vertical discretization

Model observation point

Model boundary end point

Observation well and approximate thermistor

 depth below streambed or land surface-data

 used for boundary input and model observation

Specified-temperature boundary

No specified head or temperature

 at boundary
Appendix 2 77

Figure 2-4. Observed and simulated temperature for the North Fork Smith River near mouth monitoring site (station 06075700), 2007 

and 2008. (Horizontal and vertical hydraulic conductivities were set at 3x10-6 feet per second.)

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_33.ai

0

5

25

North Fork Smith River

Well NF0602—1.42 feet below

 streambed, observed

Well NF0602—1.42 feet below

 streambed, simulated

Well NF0602—2.92 feet below

 streambed, observed

Well NF0602—2.92 feet below

 streambed, simulated

North Fork Smith River

Well NF0603—1.60 feet below

 streambed, observed

Well NF0603—1.60 feet below

 streambed, simulated

Well NF0603—3.10 feet below

 streambed, observed

Well NF0603—3.10 feet below

 streambed, simulated

Apr. May June July Aug.

2007

Sept. Oct. Nov.

Temperature, in degrees celsius 15

20

10

0

5

25

15

20

10

EXPLANATION

EXPLANATION

0

5

25

North Fork Smith River

Well NF0602—1.42 feet below

 streambed, observed

Well NF0602—1.42 feet below

 streambed, simulated

Well NF0602—2.92 feet below

 streambed, observed

Well NF0602—2.92 feet below

 streambed, simulated

North Fork Smith River

Well NF0603—1.60 feet below

 streambed, observed

Well NF0603—1.60 feet below

 streambed, simulated

Well NF0603—3.10 feet below

 streambed, observed

Well NF0603—3.10 feet below

 streambed, simulated

Apr. May June July Aug.

2008

Sept. Oct. Nov.

Temperature, in degrees celsius 15

20

10

0

5

25

15

20

10

EXPLANATION

EXPLANATION
78 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

from the stream bank wells (SR0608 and SR0611). The lower 

model boundary was represented with a combination of head 

data from both bank wells (SR0608 on right bank and SR0611 

on left bank) and instream (SR0609 and SR0610) wells and 

temperature from the lower thermistors (SR0608-4.53 ft, 

SR0609-2.90 ft, SR0610-2.99 ft, and SR0611-4.45 ft) in those 

wells at about 3 ft below the stream bottom. The central part 

of the lower boundary was represented by average water levels 

and temperatures of the instream wells (SR0609-2.90 ft and 

SR0610-2.99 ft). 

Comparisons between the simulated and measured 

temperatures at the observation points for different hydraulic 

conductivities determined that the best matches for the 

2008 data occured with saturated hydraulic conductivity 

equal to 4×10–5 ft/s (roughly equivalent to a standard sandy 

loam) in both the horizontal and vertical directions (table 9, 

fig. 2-6). Simulated temperatures at both the right bank side 

(observation point SR0609-1.4 ft) and left bank side (observation point SR0610-1.49 ft) closely matched the observed 

temperatures.

Figure 2-5. Boundary conditions and observation points for the VS2DH model, Smith River above Mud Springs Creek (station 06075850) 

monitoring site cross section.

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_34.ai

EXPLANATION

General soil hydraulic properties

 (table 9)

Specified-head and specified

 temperature boundary

Quaternary alluvium—Near-

 streambed sediments (table 9)

Horizontal discretization

Vertical discretization

Model observation point

Model boundary end point

Specified-temperature boundary

No specified head or temperature

 at boundary

Well SR0609

Monitoring well and identifier

Observation well and approximate thermistor

 depth below streambed or land surface-data

 used for boundary input and model observation

SR0609-2.90 feet

∆Z

∆X

33 feet

5.45 feet 0.70 feet

Well SR0611 Well SR0609 Well SR0610 Well SR0608

SR0609 and SR0610 average water level 

and temperature at lower thermistors

SR0609 -2.90 feet

SR0610-2.99 feet

Smith River

SR0611- 4.45 feet

0.50 feet

Air

SR0608 - 4.53 feet 

SR0610-1.49 feet

SR0611-2.95 feet

SR0609 -1.40 feet

SR0608 - 3.03 feet

Air

5.15 feet

∆Z =0.1 feet

∆X =0.4 feet
Appendix 2 79

Figure 2-6. Observed and simulated temperatures for the Smith River above Mud Springs Creek monitoring site (station 06075850), 

2008. (Horizontal and vertical hydraulic conductivities were set at 4x10-5 feet per second.)

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_35.ai

-5

0

25

Smith River

Well SR0609—1.40 feet below streambed, observed

Well SR0609—1.40 feet below streambed, simulated

5

10

15

20

-5

0

25

5

10

15

20

Apr. May June July Aug.

2008

Sept. Oct. Nov. Dec.

Temperature, in degrees celsius 

Smith River

Well SR0610—1.49 feet below streambed, observed

Well SR0610—1.49 feet below streambed, simulated

EXPLANATION

EXPLANATION
80 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

The flow of water (water flux) across the streambed, bottom, and side boundaries of the models was calculated using 

the hydraulic characteristics determined from the calibrated 

2-D heat and solute transport VS2DH models. Water flux 

calculated for each boundary represents the amount of water 

that flowed across the entire length of each boundary over 

a unit (1-ft) width. Flux values for the streambed boundary 

(blue lines, figs. 3-1–3-3) are shown as positive when water is 

moving from the groundwater to the stream and negative when 

water is moving from the stream to the groundwater. Flux 

estimates for the bottom and side boundaries (black, red, and 

purple lines, figs. 3-1–3-3) are positive when water is moving 

into the surrounding aquifer system and negative when the 

water is moving past the boundary into the stream.

South Fork Smith River near Mouth

The estimated daily flux of groundwater discharge to 

the stream across the streambed boundary was very similar 

in 2007 and 2008 at the South Fork Smith River near mouth 

(station 06075785; table 10; fig. 3-1) cross section; daily 

water-flux from the groundwater to the stream (noted as a 

positive values on fig. 3-1, blue line) ranged from a low of 

about 2.0 ft3/d in both years to highs of about 3.1 ft3/d (2007) 

and 3.4 ft3/d (2008). The majority of the flux of groundwater 

to the stream (fig. 3-1B and 3-1C) appeared to flow across the 

bottom boundary (black line), followed by the left and right 

boundaries (red and purple lines, respectively). Temperature 

distributions within the model domain as well as the magnitude and direction of water flow for three selected dates are 

illustrated in figure 3-1D.

North Fork Smith River near Mouth

The estimated daily flux of stream water infiltrating to the 

groundwater at the North Fork Smith River near mouth cross 

section (station 06075700) was greater in 2007 than in 2008 

(table 10; fig. 3-2). In 2007, water flux ranged from near zero 

(during a brief period of gaining groundwater in the stream) 

to near -1.7 ft3/d (noted as negative values, as the stream was 

losing water on fig. 3-2). In 2008, water flux ranged from short 

periods of groundwater discharged to the stream during early 

summer and fall, to about -1.0 ft3/d when water was flowing 

from the stream to the groundwater. Temperature distributions within the model domain as well as the magnitude and 

direction of water flow for three selected dates are illustrated 

in figure 3-2D.

The majority of the water appeared to exit the modeled 

system through the bottom boundary (black line; fig. 3-2B and 

3-2C). Water-flux rates through the left and right boundaries 

were very similar (red and purple lines, respectively; fig. 3-2B

and 3-2C). Water flux from the stream to the groundwater 

increased incrementally from mid-May through early September in 2007 (fig. 3-2B). Flux from the stream to the groundwater was more variable in 2008, with the highest flux rates 

occurring in May and early August (fig. 3-2C).

Smith River above Mud Springs Creek

The direction and magnitude of daily flux of water 

changed dramatically during the period of record coincident 

with the occurrence of local flood irrigation at the Smith River 

above Mud Springs Creek cross section (station 06075850; 

table 10; fig. 3-3). Estimated daily flux of water ranged from 

about -2.7 ft3/d in the spring, during the highest rates of flow 

from the stream to the groundwater, to 9.8 ft3/d during the 

summer when groundwater discharged to the stream (fig. 

3-3B). Temperature distributions within the model domain as 

well as the magnitude and direction of water flow for three 

selected dates are illustrated in figure 3-3C.

Appendix 3. Water Flux Calculations of Cross-Section Models
Appendix 3 81

Figure 3-1. Water-flux information, in cubic feet per day (ft3/d), for the South Fork Smith River near mouth (station 06075785) modeled 

cross section. A, Location of model boundaries; B, Daily flux across model boundaries, 2007; C, Daily flux across model boundaries, 

2008; and D, Simulated temperature distributions inside the model domain on three selected dates (arrows indicate direction and 

magnitude of water flux). Flux estimates for the streambed boundary (blue lines) are shown as positive when water is moving from the 

groundwater system to the stream and negative when moving from the stream to the groundwater system. Flux estimates from the 

bottom and side boundaries (black, red, and purple lines) are positive when the water flux is into the surrounding groundwater system 

and negative when the water flux past the boundary is into the stream. N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_36A.ai

-4

Apr. May June July

2007

Flux across boundary, in cubic feet per day

Aug. Sept. Oct.

Apr. May June July

2008

Aug. Sept. Oct.

-3

4

-2

-1

0

1

2

3

-4

-3

4

-2

-1

0

1

2

3

EXPLANATION

Streambed

Bottom

Right

Left

A

Model domain

B

C

Model domain boundaries

Streambed

Bottom

Right

Left
82 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Figure 3-1. Water-flux information, in cubic feet per day (ft3/d), for the South Fork Smith River near mouth (station 

06075785) modeled cross section. A, Location of model boundaries; B, Daily flux across model boundaries, 2007; C, 

Daily flux across model boundaries, 2008; and D, Simulated temperature distributions inside the model domain on three 

selected dates (arrows indicate direction and magnitude of water flux). Flux estimates for the streambed boundary (blue 

lines) are shown as positive when water is moving from the groundwater system to the stream and negative when moving 

from the stream to the groundwater system. Flux estimates from the bottom and side boundaries (black, red, and purple 

lines) are positive when the water flux is into the surrounding groundwater system and negative when the water flux past 

the boundary is into the stream.—Continued

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_36B.ai 7 feet 7 feet 7 feet

42 feet

Temperature—In

 degrees celsius Model domain boundaries

May 15, 2008

June 15, 2008

August 15, 2008

25

20

15

10

5

0

Streambed

Bottom

Right

Left

EXPLANATION

D

0.15 cubic feet per day

0.17 cubic feet per day

0.12 cubic feet per day

2.94 cubic feet per day

2.49 cubic feet per day

2.70 cubic feet per day

3.20 cubic feet per day

2.32 cubic feet per day

1.97 cubic feet per day

1.97 cubic feet per day

0.30 cubic feet per day

0.23 cubic feet per day

0.33 cubic feet per day
Appendix 3 83

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_37A.ai

-2

Apr. May June July

2007

Flux across boundary, in cubic feet per day

Aug. Sept. Oct. Nov.

2008

-1

2

0

1

-2

Apr. May June July Aug. Sept. Oct. Nov.

-1

2

0

1

EXPLANATION

Streambed

Bottom

Right

Left

A

Model domain

B

C

Model domain boundaries

Streambed

Bottom

Right

Left

B

Figure 3-2. Water-flux information, in cubic feet per day (ft3/d), for the North Fork Smith River near mouth (station 06075700) 

modeled cross section. A, Location of model boundaries; B, Daily flux across model boundaries, 2007; C, Daily flux across model 

boundaries, 2008; and D, Simulated temperature distributions inside the model domain on three selected dates (arrows indicate 

direction of water flux). Flux estimates for the streambed boundary (blue lines) are shown as positive when water is moving from 

the groundwater system to the stream and negative when moving from the stream to the groundwater system. Flux estimates for 

the bottom and side boundaries (black, red, and purple lines) are positive when the water flux is into the surrounding groundwater 

system and negative when the water flux past the boundary is into the stream.
84 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_37B.ai 10 feet 10 feet 10 feet

37 feet

Temperature—In

 degrees celsius Model domain boundaries

May 15, 2008

June 15, 2008

August 15, 2008

25

20

15

10

5

0

Streambed

Bottom

Right

Left

EXPLANATION

D

0.20 cubic feet per day

0.80 cubic feet per day

0.63 cubic feet per day

0.52 cubic feet per day

0.31 cubic feet per day

0.87 cubic feet per day

0.55 cubic feet per day

0.17 cubic feet per day

0.09 cubic feet per day 0.11 cubic feet per day

0.15 cubic feet per day 0.19 cubic feet per day

Figure 3-2. Water-flux information, in cubic feet per day (ft3/d), for the North Fork Smith River near 

mouth (station 06075700) modeled cross section. A, Location of model boundaries; B, Daily flux across 

model boundaries, 2007; C, Daily flux across model boundaries, 2008; and D, Simulated temperature 

distributions inside the model domain on three selected dates (arrows indicate direction of water 

flux). Flux estimates for the streambed boundary (blue lines) are shown as positive when water is 

moving from the groundwater system to the stream and negative when moving from the stream to the 

groundwater system. Flux estimates for the bottom and side boundaries (black, red, and purple lines) 

are positive when the water flux is into the surrounding groundwater system and negative when the 

water flux past the boundary is into the stream.—Continued
Appendix 3 85

Figure 3-3. Water-flux information, in cubic feet per day (ft3/d), for the Smith River above Mud Springs Creek (station 06075850) 

modeled cross section. A, Location of model boundaries; B, Daily flux across model boundaries, 2008; and C, Simulated temperature 

distributions inside the model domain on three selected dates (arrows indicate direction of water flux). Flux estimates for the 

streambed boundary (blue lines) are shown as positive when water is moving from the groundwater system to the stream and negative 

when moving from the stream to the groundwater system. Flux estimates for the bottom and side boundaries (black, red, and purple 

lines) are positive when the water flux is into the surrounding groundwater system and negative when the water flux past the boundary 

is into the stream.

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_38A.ai

-10 Apr. May June July

2008

Flux across boundary, in cubic feet per day

Aug. Sept. Oct. Nov. Dec.

-8

10

-6

-4

-2

0

2

4

6

8

EXPLANATION

Streambed

Bottom

Right

Left

A

Model domain

B

Model domain boundaries

Streambed

Bottom

Right

Left
86 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

Figure 3-3. Water-flux information, in cubic feet per day (ft3/d), for the Smith River above Mud Springs Creek (station 06075850) 

modeled cross section. A, Location of model boundaries; B, Daily flux across model boundaries, 2008; and C, Simulated 

temperature distributions inside the model domain on three selected dates (arrows indicate direction of water flux). Flux 

estimates for the streambed boundary (blue lines) are shown as positive when water is moving from the groundwater system 

to the stream and negative when moving from the stream to the groundwater system. Flux estimates for the bottom and side 

boundaries (black, red, and purple lines) are positive when the water flux is into the surrounding groundwater system and 

negative when the water flux past the boundary is into the stream.—Continued

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_38B.ai

0.12 cubic feet per day

0.64 cubic feet per day

2.43 cubic feet per day

2.00 cubic feet per day

7.08 cubic feet per day

5.96 cubic feet per day

0.65 cubic feet per day

0.57 cubic feet per day

0.28 cubic feet per day

0.47 cubic feet per day

0.00 cubic feet per day 0.06 cubic feet per day

10 feet 10 feet 10 feet

33 feet

May 15, 2008

June 15, 2008

August 15, 2008

Streambed

Bottom

Right

Left

EXPLANATION

C

Temperature—In

 degrees celsius Model domain boundaries

25

20

15

10

5

0
Appendix 4 87

The cross-sectional models developed for this study 

clearly have uncertainty and error. Numerical models of 

groundwater flow are limited in their representation of the 

physical system because they contain simplifications and 

assumptions of uncertain validity. Results from groundwaterflow models have a degree of uncertainty because detailed 

distributions of aquifer parameters are rarely available. Limitations in the numerical models that may cause errors in the 

results can be caused by (1) invalid assumptions or approach 

implemented by the numerical simulation code, and (2) inaccurate conceptual model, aquifer parameters, boundary conditions, or initial conditions. Sensitivity to (2) was evaluated as 

part of this analysis.

Modifications to the calibrated models selected for each 

cross section were conducted in order to examine model 

sensitivity and uncertainty to variations in aquifer characteristics. Aquifer characteristics of selected calibrated models were 

modified by (1) adjusting hydraulic conductivity (in both the 

horizontal and vertical directions) an order of magnitude lower 

and higher and (2) adjusting the ratio of vertical to horizontal 

hydraulic conductivity. In addition, water-flux values were 

calculated for each modeled section to examine the sensitivity 

of water-flux values to changes in model parameters. Simulated temperatures were sensitive to changes in hydraulic 

conductivity and the ratios of vertical to horizontal hydraulic 

conductivity at each of the modeled sections. The spatial 

variation of hydraulic characteristics within cross sections 

were not examined as part of the sensitivity analysis, but were 

examined during model calibration (see Model—South Fork 

Smith River near mouth). Better agreements between observed 

versus simulated temperatures could be achieved by spatially 

adjusting hydraulic properties in the model (for example, 

higher hydraulic conductivity values on one side and lower on 

the other), but this was not implemented because of the lack of 

subsurface data.

The models were sensitive to changes in hydraulic conductivity and ratios of vertical to horizontal hydraulic conductivity. As an example, figure 4-1 illustrates the measured temperatures at the observation points of the Smith River above 

Mud Springs Creek cross section and the simulated temperatures for the calibrated model (hydraulic conductivity 4x10-5

ft/s) and simulated temperatures after adjusting the overall 

hydraulic conductivity and the ratio of horizontal to vertical 

hydraulic conductivity. During periods of small hydraulic 

gradients, the simulated and observed temperatures remained 

relatively similar for the models in which the overall hydraulic 

conductivity was adjusted. As hydraulic gradients increased 

during the gaining periods, simulated temperatures differed 

from observed temperatures by up to 4°C. The lower hydraulic conductivity resulted in increased simulated temperatures 

relative to the observed temperatures during the gaining period 

and higher conductivity values resulted in lower observed temperatures during the gaining period. Adjustment of the vertical 

to horizontal hydraulic conductivity ratio from 1:1 to 1:2 and 

1:5 generally overestimated temperatures by up to 3°C during 

the gaining periods.

Adjustments to the hydraulic conductivity of the calibrated or best-fit models resulted in substantial changes in 

water-flux values at the modeled cross sections. For example, 

reducing or increasing the overall hydraulic conductivity of 

the models by an order of magnitude resulted in an overall 

increase or decrease of the flux values by an order of magnitude, respectively. Adjusting ratios of vertical to horizontal 

hydraulic conductivity from 1:1 to 1:2 and 1:5 reduced calculated monthly mean flux rates by about 50 to 70 percent. As 

suggested by the sensitivity analysis of these models to variations in aquifer characteristics, additional analysis of aquifer 

characteristics at these modeled sections would increase the 

confidence in the model results.

Appendix 4. Cross-Sectional Model Sensitivity Analysis
88 Groundwater and Surface-Water Interaction in the Upper Smith River Watershed

N:\Jeff\den12_cmrs00_0091_sir_caldwell\figures\figure_39.ai

5

0

Well SR0609—1.40 feet below

 streambed, observed

Well SR0609—1.40 feet below

 streambed, simulated–calibrated;

 Kv and Kh = 4x10-5 feet per second

 Well SR0609—1.40 feet below

 streambed, simulated–Kv and Kh =

 4x10-6 feet per second

Well SR0609—1.40 feet below

 streambed, simulated–Kv and Kh =

 4x10-4 feet per second

EXPLANATION

Well SR0610—1.49 feet below

 streambed, observed

Well SR0610—1.49 feet below

 streambed, simulated–calibrated;

 Kv and Kh = 4x10-5 feet per second

 Well SR0610—1.49 feet below

 streambed, simulated–Kv and Kh =

 4x10-6 feet per second

Well SR0610—1.49 feet below

 streambed, simulated–Kv and Kh =

 4x10-4 feet per second

EXPLANATION

Well SR0609—1.40 feet below

 streambed, observed

Well SR0609—1.40 feet below

 streambed, simulated–calibrated;

 Kv and Kh = 4x10-5 feet per second

 Well SR0609—1.40 feet below

 streambed, simulated–Kv = 2x10-5

 feet per second, Kh = 4x10-5 feet per

 second

Well SR0609—1.40 feet below

 streambed, simulated–Kv = 8x10-6

 feet per second, Kh = 4x10-5 feet per

 second

EXPLANATION

Well SR0610—1.49 feet below

 streambed, observed

Well SR0610—1.49 feet below

 streambed, simulated–calibrated;

 Kv and Kh = 4x10-5 feet per second

 Well SR0610—1.49 feet below

 streambed, simulated–Kv = 2x10-5

 feet per second, Kh = 4x10-5 feet per

 second

Well SR0610—1.49 feet below

 streambed, simulated–Kv = 8x10-6

 feet per second, Kh = 4x10-5 feet per

 second

EXPLANATION

10

15

20

Apr. May June July Aug.

2008

Sept. Oct. Nov. Dec.

Temperature, in degrees celsius 

5

0

10

15

20

5

0

10

15

20

5

0

10

15

20

Figure 4-1. Observed and simulated temperatures with varied hydraulic conductivity values and ratios of vertical (Kv) to horizontal 

(Kh) hydraulic conductivity of the VS2DH 2-dimensional model of the Smith River above Mud Springs Creek monitoring site (station 

06075850), 2008.
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U.S. Geological Survey

3162 Bozeman Ave.

Helena, Montana 59601

(406) 457-5900

Or visit the Montana Water Science Center Web site at:

http://mt.water.usgs.gov/

Caldwell and Eddy-Miller— Groundwater and Surface-Water Interaction within the Upper Smith River Watershed—Scientific Investigations Report 2013–5051

Printed on recycled paper

ISSN 2328-031X (print)

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20135051