U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2004 – 5170

Version 1.0

Prepared in cooperation with

Idaho Department of Water Resources 

Instream piezometer equipped with thermistors that 

continually monitor surface- and ground-water 

relations, Portneuf River, Idaho

Surface- and Ground-Water Relations on the Portneuf 

River, and Temporal Changes in Ground-Water Levels in 

the Portneuf Valley, Caribou and Bannock Counties, Idaho, 

2001 – 02
Surface- and Ground-Water Relations on 

the Portneuf River, and Temporal Changes 

in Ground-Water Levels in the Portneuf 

Valley, Caribou and Bannock Counties, 

Idaho, 2001 – 02

By Gary J. Barton

Scientific Investigations Report 2004 – 5170

Version 1.0

U.S. Department of the Interior

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

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2004

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

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

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

endorsement by the U.S. Government.

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

reproduce any copyrighted materials contained within this report.

Barton, G.J., 2004, Surface- and ground-water relations on the Portneuf River, and temporal changes in ground-water 

levels in the Portneuf Valley, Caribou and Bannock Counties, Idaho, 2001 – 02: U.S. Geological Survey Scientific 

Investigations Report 2004-5170, 50 p.
Contents iii

Contents

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

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

Purpose and Scope ............................................................................................................................... 3

Acknowledgments................................................................................................................................. 3

Description of Study Area .................................................................................................................... 3

Surface-Water Conditions .................................................................................................................... 6

Ground-Water Conditions ..................................................................................................................... 7

Methods of Investigations ................................................................................. 8

Numbering and Location of Measurement Stations ........................................................................ 8

Timing of Seepage Studies ................................................................................................................... 9

Measuring Differences in Hydraulic Head Between Surface-Water Stages and 

Ground-Water Levels ............................................................................................................... 10

Measuring Water Quality .................................................................................................................... 12

Using Heat as a Tracer to Monitor Surface- and Ground-Water Relations ................................ 12

Concepts......................................................................................................................................... 12

Instrumentation ............................................................................................................................. 14

Measuring Streamflow ......................................................................................................................... 15

Measuring Ground-Water Levels ........................................................................................................ 15

Quality Assurance.................................................................................................................................. 15

Seasonality of Surface- and Ground-Water Relations on the Portneuf River ........................ 19

Spring Regulated High Flows at the Start of the Irrigation Season ............................................. 19

Mid-Summer Regulated High Flows During the Irrigation Season ............................................... 21

Surface- and Ground-Water Relations Based on Specific Conductance and 

Temperature ..................................................................................................................... 24

Surface- and Ground-Water Relations Based on Continuous Temperature Data 

From Thermistor Arrays ................................................................................................. 26

Late-Summer Base Flows During the Irrigation Season ................................................................. 26

Early-Fall Regulated Low Flows at the End of the Irrigation Season ............................................. 26

Mid-Fall Regulated Low Flows During the Post-Irrigation Season ............................................... 28

Streamflow Depletion ........................................................................................................................... 28

Temporal Changes in Ground-Water Levels in the Portneuf Valley .................................... 29

Hydrologic Conditions .......................................................................................................................... 29

Annual Fluctuations, 2001– 02 .............................................................................................................. 32

Long-Term Fluctuations, 1968 – 2001 ................................................................................................... 32

Summary and Conclusions ................................................................................. 32

References Cited ............................................................................................. 34

Appendix 1. Water levels in selected wells in the Portneuf Valley, Idaho,

1968 – 69 and 2001– 02 .............................................................................. 35

Appendix 2. Continuous record of surface- and ground-water temperatures at 

measurement stations on the Portneuf River, Idaho, August 2001 through

January 2002 ....................................................................................... 45
iv Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

Figures

1. Location of Portneuf River study area, Idaho ................................................................... 2

2. Location of measurement stations and surface-water diversions on the 

Portneuf River between Chesterfield Reservoir and Pebble, Idaho ............................. 4

3. Location of measurement stations and surface-water diversions on the

Portneuf River between Pebble and Topaz, Idaho ........................................................... 5

0 4. Mean monthly streamflow in the Portneuf River near Pebble and at 

Topaz, Idaho, 1968 – 2001 ....................................................................................................... 6

5. Spring located about 0.3 mile upstream from measurement station 8SP 

and 200 feet east of the Portneuf River in the southwestern part of the 

Portneuf Valley, Idaho, July 2001 ........................................................................................ 7

0 6. Water levels in irrigation well 07S-39E-10CCD1 and water-equivalent 

snowpack during April at Pebble Creek station, 1968 – 2002 .......................................... 8

0 7. Growth in allocated ground-water withdrawals in the Portneuf Valley, 

Idaho, 1990 – 2000 .................................................................................................................... 9

08. Instream piezometer used to continuously monitor the temperature of 

the Portneuf River and of ground water and to measure hydraulic head 

of surface and ground water at measurement station 3SPT in the 

Portneuf River Valley reach, Idaho, July 2001 ................................................................... 10

0 9. Daily and monthly precipitation at Pocatello regional airport, Idaho, 

2001 – 02..................................................................................................................................... 11

10. Schematic of instream piezometer and manometer board ............................................ 12

11. Surface- and ground-water relations and thermal response during summer 

and early fall in streams with (A) gaining reaches and (B) losing reaches ................. 14

12. Variability in streamflow at measurement stations in the Portneuf 

River Valley reach, Idaho, July 16 – 17, 2001 ...................................................................... 15

13. Streamflow adjusted for diversions at measurement stations and

location of gaining and losing reaches in the Portneuf River Valley 

reach, Idaho, 2001 – 02 .......................................................................................................... 18

14. Differences in hydraulic head between river stages and ground-water 

levels at measurement stations and location of potential gaining and 

losing reaches in the Portneuf River Valley reach, Idaho, 2001 – 02. ............................ 20

15. Location of gaining, neutral, and losing reaches in the Portneuf River 

Valley reach, Idaho, based on integrated analysis of streamflow, hydraulic 

head, specific conductance, and temperature, 2001 – 02. .............................................. 21

16. Streamflow and location of gaining and losing reaches in the PebbleTopaz reach, Idaho, 2001–02. ............................................................................................... 22

17. Specific conductance and temperature at measurement stations in the 

Portneuf River Valley reach, Idaho, July 10–12, 2001 ...................................................... 23

18. Specific conductance and temperature profiles across the Portneuf River, 

Idaho, at measurement station 8SP, July 11, 2001. ........................................................... 24

19. Continuous record of surface- and ground-water temperatures at measurement stations 2SPT and 3SPT showing cool ground water discharging to 

the Portneuf River, Idaho, July 2001. .................................................................................. 25
Contents v

20. Continuous record of surface- and ground-water temperatures at 

measurement stations 6SPT and 7SPT showing warm stream water 

infiltrating down through the streambed in the Portneuf River, Idaho, 

July 2001.................................................................................................................................. 27

21. Annual fluctuations in ground-water levels in the Portneuf Valley, Idaho, 

July 2001 through July 2002. ................................................................................................ 30

22. Long-term fluctuations in ground-water levels in the Portneuf Valley, Idaho, 

September and October 1968 and 2001. ............................................................................. 31

Tables

1. Description of measurement stations and construction information for instream 

piezometers at measurement stations on the Portneuf River, Idaho ............................ 13

 2. Streamflow, surface-water diversions, and calculated gains and losses in streamflow between measurement stations on the Portneuf River, Idaho, 2001–02 .............. 16

Conversion Factors and Datums

Multiply By To obtain

acre 4,047 square meter (m2)

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

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

foot (ft) 0.3048 meter (m)

inch (in.) 2.54 centimeter (cm)

mile (mi) 1.609 kilometer (km)

square mile (mi2) 2.590 square kilometer (km2)

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

 ̊ F = (1.8 x  ̊C) + 32

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD of 1929).

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

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25  ̊C).
vi Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

T.1S.

12 11 10 9 8

6 5 4 3

40 41 42

39

37 36 35 34 33 R.1E.

1 2

4 3

5

12 11

9 10

8 7

28

14

16 15

17 18

24 23

21 22

20 19

25 26 27

29 30

36 35

33 34

32 31

6

A

B

A

D C

C

C

C

A

B

A

B

D

C

D

C

A

B

A

B

D

7

38

T. 7 S.

R. 38 E.

13

D

D

7S-38E-13DDB1

Section 13

The well-numbering 

system used by the USGS 

in Idaho indicates the location of a well or spring 

according to the official 

rectangular subdivisions of 

the public lands. The first 

two segments of the number 

designate the township and 

range. The third segment 

designates the section 

number and is followed by 

three letters and a numeral, 

which designate, respectively, the quarter section, 

the 40-acre tract, the 10-acre 

tract, and the serial number 

of the well or spring within 

the tract. Quarter sections 

are lettered A, B, C, and D, 

in a counterclockwise order 

from the northeast quarter 

of each section. Within the 

quarter sections, 40-acre and 

10-acre tracts are lettered in 

the same manner. Thus, well 

07S-38E-13DDB1 is in the 

NW1/4SE1/4SE1/4 sec. 13, 

T. 07 S., R. 38 E., and was 

the first well inventoried in 

that 10-acre tract.

Caption
Abstract

The State of Idaho and local water users are concerned 

that streamflow depletion in the Portneuf River in Caribou and 

Bannock Counties is linked to ground-water withdrawals for 

irrigated agriculture. A year-long field study during 2001– 02 

that focused on monitoring surface- and ground-water relations was conducted, in cooperation with the Idaho Department of Water Resources, to address some of the water-user 

concerns. The study area comprised a 10.2-mile reach of the 

Portneuf River downstream from the Chesterfield Reservoir in 

the broad Portneuf Valley (Portneuf River Valley reach) and a 

20-mile reach of the Portneuf River in a narrow valley downstream from the Portneuf Valley (Pebble-Topaz reach). 

During the field study, the surface- and ground-water 

relations were dynamic. A losing river reach was delineated 

in the middle of the Portneuf River Valley reach, centered 

approximately 7.2 miles downstream from Chesterfield Reservoir. Two seepage studies conducted in the Portneuf Valley 

during regulated high flows showed that the length of the 

losing river reach increased from 2.6 to nearly 6 miles as the 

irrigation season progressed.

Surface- and ground-water relations in the Portneuf Valley also were characterized from an analysis of specific conductance and temperature measurements. In a gaining reach, 

stratification of specific conductance and temperature across 

the channel of the Portneuf River was an indicator of ground 

water seeping into the river.

An evolving method of using heat as a tracer to monitor 

surface- and ground-water relations was successfully conducted with thermistor arrays at four locations. Heat tracing 

monitored a gaining reach, where ground water was seeping 

into the river, and monitored a losing reach, where surface 

water was seeping down through the riverbed (also referred to 

as a conveyance loss), at two locations.

Conveyance losses in the Portneuf River Valley reach 

were greatest, about 20 cubic feet per second, during the 

mid-summer regulated high flows. Conveyance losses in the 

Pebble-Topaz reach were greatest, about 283 cubic feet per 

second, during the spring regulated high flows and were attributed to a hydroelectric project.

Comparison of water levels in 30 wells in the Portneuf 

Valley during September and October 1968 and 2001 indicated 

long-term declines since 1968; the median decline was 3.4 

feet. September and October were selected for characterizing 

long-term ground-water-level fluctuations because declines 

associated with irrigation reach a maximum at the end of the 

irrigation season. The average annual snowpack in the study 

area has declined significantly; 1945– 85 average annual snowpack was 16.1 inches, whereas 1986 through 2002 average 

annual snowpack was 11.6 inches. Water-level declines during 

1998 – 2002 may be partially attributable to the extended dry 

climatic conditions. It is unclear whether the declines could 

be partially attributed to increases in ground-water withdrawals. Between 1968 and 1980, water rights for ground-water 

withdrawals nearly doubled from 23,500 to 46,000 acre-feet 

per year. During this period, ground-water levels were relatively constant and did not exhibit a declining trend that could 

be related to increased ground-water withdrawal rights. However, ground-water withdrawals are not measured in the valley; 

thus, the amount of water pumped is not known. 

Since the 1990s, there have been several years when the 

Chesterfield Reservoir has not completely refilled, and the 

water in storage behind the reservoir has been depleted by the 

middle of the irrigation season. In this situation, surface-water 

diversions for irrigation were terminated before the end of 

the irrigation season, and irrigators, who were relying in part 

on diversions from the Portneuf River, had to rely solely on 

ground water as an alternate supply. Smaller volumes of water 

in the Chesterfield Reservoir since the 1990s indicate a growing demand for ground-water supplies.

Introduction

The State of Idaho and local water users are concerned 

that streamflow depletion in the Portneuf River is linked 

to ground-water withdrawals for irrigated agriculture. In 

Surface- and Ground-Water Relations on the Portneuf 

River, and Temporal Changes in Ground-Water Levels in 

the Portneuf Valley, Caribou and Bannock Counties, Idaho, 

2001– 02

By Gary J. Barton
2 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001 – 02

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Introduction 3

addition, the State and local water users are concerned about 

temporal changes in ground-water levels, specifically, declining water levels. For these reasons, the Idaho Department of 

Water Resources (IDWR) requested that the U.S. Geological 

Survey (USGS) conduct a hydrologic study that focused on 

surface- and ground-water relations on the Portneuf River. In 

a USGS reconnaissance study, Norvitch and Larson (1970) 

estimated gains to and losses from the river and concluded that 

additional work was needed to help characterize the surfaceand ground-water relations and the effects of pumping wells 

on ground-water levels and streamflow.

A decree on water rights for use of water in the Chesterfield Reservoir states that releases from the reservoir shall suffer no conveyance losses (Robert Sutter, Idaho Department of 

Water Resources, written commun., 2001). Conveyance losses 

include surface water seeping down through the riverbed, 

which can be the result of natural surface- and ground-water 

relations. However, ground-water withdrawals for irrigated 

agriculture may increase ground-water-level declines and, 

therefore, increase conveyance losses. The Portneuf River 

Basin is presently under preliminary water rights adjudication.

Purpose and Scope

The purpose of this report is to (1) characterize the 

surface- and ground-water relations along a 30.2-mi reach of 

the Portneuf River downstream from Chesterfield Reservoir 

in Caribou and Bannock Counties, Idaho, and (2) describe 

temporal changes in ground-water levels in the Portneuf Valley 

from 1968 through 2002. Specifically, this report documents 

the seasonality of gaining and losing reaches in the Portneuf 

River. The gaining and losing river reaches are identified 

by means of seepage studies, including a new technique that 

utilizes water temperature as a tracer. Some insight into 

streamflow depletion during high flows during the irrigation 

season is provided. Estimation of long-term fluctuations in 

ground-water levels since 1968 is limited to an analysis of 

32 wells completed in the water-table aquifer in the Portneuf 

Valley.

Acknowledgments

Thanks are extended to the people of the Portneuf Valley 

study area for their willing assistance and for allowing the 

USGS access to their property and wells in order to collect 

data. The IDWR provided the USGS with data on water use 

in the Portneuf Valley. Steve Hebdon, District Watermaster of 

the Portneuf River Marsh Valley Canal, provided the USGS 

with data on surface-water diversions and much information about the history of development in the Portneuf Valley. 

Dave Clark, ground-water discipline specialist for the USGS 

in Boise, Idaho, developed the project proposal and provided 

technical input on collecting and analyzing data for the project. Sabrina Conti, USGS scientist in Boise, Idaho, and Kim 

Trask, student intern with the USGS in Tacoma, Washington, 

assisted in gathering and analyzing the data. Hydrologic technicians in the Idaho Falls Field Office worked long hours to 

measure streamflow, hydraulic gradients at instream piezometers, and water levels in irrigation wells.

Description of Study Area

The study area encompasses about 65 mi2 of the broad 

Portneuf Valley and includes 7.8 mi of channelized river 

downstream from Chesterfield Reservoir, the Portneuf Marsh 

Valley Canal, and a 2.4-mi reach of the Portneuf River downstream from the Portneuf Marsh Valley Canal (figs. 1– 3). 

The Portneuf Marsh Valley Canal is referred to locally as the 

Downey Canal. Water released from the Chesterfield Reservoir regulates flow in the total 10.2-mi reach. The reservoir 

has a capacity of 24,000 acre-ft. When the river was channelized (during 1908 –12), about 2 mi of the relic Portneuf River 

remained directly downstream from the Chesterfield Reservoir 

but was separated from the Portneuf Marsh Valley Canal. 

Water in the relic stream channel is a fraction of its previous 

flow and is diverted primarily for irrigation during the growing 

season; hence, the relic river is dry part of the year. 

For the purpose of this report, the Portneuf River in the 

Portneuf Valley is defined to include the Portneuf Marsh Valley Canal and is referred to as the Portneuf River Valley reach. 

The study area also includes a 20-mi reach of the Portneuf 

River that is located downstream from the Portneuf River Valley reach and upstream from Topaz (figs. 1 and 3). This 20-mi 

reach cuts through the Portneuf Range and forms a narrow valley. The channel gradient is appreciably greater downstream 

from the Portneuf River Valley reach. For the purpose of 

this report, the 20-mi reach is referred to as the Pebble-Topaz 

reach.

Physiographically, the study area is located in the northeastern-most extension of the Basin and Range province of the 

Intermontane Plateau (Fenneman, 1931, pl. 1). The study area 

is in the Great Basin section of the province and is characterized by isolated mountain ranges separated by aggraded desert 

plains. Sediments in the Portneuf Valley consist of loess, 

silty alluvial deposits, and volcanic ash, which form a broad, 

alluvial plain. The agricultural area lies within this plain and 

consists of dryland farming, pasture, and grazing. The Portneuf Valley is bounded on the east by the Chesterfield Range 

and on the west by the Portneuf Range.

Norvitch and Larson (1970) described climatic conditions 

in the Portneuf Valley as variable, primarily because of the 

large topographic relief (altitudes of 5,200 to 9,271 ft above 

sea level) within the valley. Annual average precipitation 

ranges from less than 10 in. on the valley floor to more than 30 

in. near the summit of Haystack Mountain (altitude 9,033 ft) 

in the Portneuf Range. Summer precipitation is generally low 

and afternoon temperatures are high; arid conditions can exist 

seasonally in the lower valley areas.
4 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001 – 02

T.

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R. 39 E.

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R. 38 E.

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Ground-water-level measurement station and identification number—Water levels were measured in wells during approx-

 imately eight visits per site. Graphs of water levels provided in appendix 1. Water levels have been monitored quarterly

 and sometimes weekly in well 10CCD1 since 1968

Seepage measurement station and identification number—"S" indicates that streamflow was measured; "P" indicates that

 an instream piezometer was installed in riverbed and the hydraulic head between river stage and the ground-water level was

 measured with a manometer board and field water-quality parameters were measured; "T" indicates that a second instream

 piezometer equipped with thermistors that monitor stream temperature and ground-water temperature at 20 and 40 inches

 below the riverbed was installed. Information for instream piezometers is provided in table 1. Eight-digit number is

 identification number for discontinued U.S. Geological Survey gaging station

Surface-water diversion site and identification

Spring—Tail indicates direction of flow

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Figure 2. Location of measurement stations and surface-water diversions on the Portneuf River between Chesterfield Reservoir 

and Pebble, Idaho.
Introduction 5

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Hydroelectric

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CARIBOU COUNTY

BANNOCK COUNTY

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Seepage measurement station and identification number—"S" indicates that

 streamflow was measured. Information for instream piezometers is provided

 in table 1. Eight-digit number is identification number for discontinued U.S.

 Geological Survey gaging station

Surface-water diversion site and identification

Natural Resources Conservation Service snowpack measurement station

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Figure 3. Location of measurement stations and surface-water diversions on the Portneuf River between Pebble and Topaz, 

Idaho.
6 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001 – 02

Surface-Water Conditions

The Portneuf Marsh Valley Canal was constructed in 

conjunction with the Chesterfield Reservoir during 1908 – 12 

to provide a dependable source of water to areas downstream 

from Lava Hot Springs. This unlined canal carries nearly all 

the water formerly carried by the Portneuf River (U.S. Department of Agriculture, 1993). Water rights decree the cessation 

of all streamflow releases from the Chesterfield Reservoir 

during September 15 to April 15 on an annual basis for the 

purpose of reservoir refilling. The water in storage is released 

the following spring and summer and the water rights decree 

that this water shall suffer no conveyance losses. During 

April 15 to September 15, water rights decree that the natural 

streamflow entering the Chesterfield Reservoir be diverted 

downstream. This natural streamflow can be diverted for irrigation in the Portneuf Valley. 

During 1912– 13 and 1968 – 77, the period of record for 

USGS stream-gaging station 13072000 near Pebble, Idaho, 

which measures drainage from 260 mi2 (fig. 2), the Portneuf 

River typically flowed between 200 and 400 ft3/s during the 

April through June snowmelt-runoff period (fig. 4). Following 

snowmelt runoff and prior to September 15, streamflow generally ranged from about 80 to 150 ft3

/s. After the annual cessation of all streamflow from the reservoir to the Portneuf River 

on September 15, flows in the river declined to a base flow 

of about 45 to 75 ft3/s during the fall, winter, and early spring 

months. The minimum daily mean flow during the period of 

record was 21 ft3/s on December 30, 1968. The maximum 

daily mean flows during the period of record were 537 ft3/s on 

April 1, 1913, and 536 ft3/s on April 9, 1976. Farther downstream at USGS stream-gaging station 13073000 at Topaz 

(fig. 3, measures drainage from 570 mi2), the Portneuf River 

during 1968 – 2001 typically flowed between 500 and 800 ft3/s 

during the April through June snowmelt-runoff period (fig. 4). 

During the rest of the year, streamflow generally ranged from 

about 110 to 180 ft3/s. The minimum daily mean flow during 

the period of record was 63 ft3/s on September 23, 2002. The 

maximum daily mean flow during the period of record was 

1,320 ft3/s on May 22, 1984.

Prior to large-scale dryland farming in the Portneuf Valley, mountain tributaries Twentyfour Mile Creek, Eighteenmile 

Creek, King Creek, and Toponce Creek provided significant 

discharge to the Portneuf River. These creeks are now diverted 

for other uses and do not provide flow to the Portneuf River. 

During the post-irrigation season, water from Toponce Creek 

is diverted into the Chesterfield Reservoir for storage. It is 

estimated that Toponce Creek supplies at least half the water 

in storage in the Chesterfield Reservoir (Steve Hebdon, District Watermaster for the Portneuf River Marsh Valley Canal, 

Idaho, oral commun., 2002). 

During this study, releases from the Chesterfield Reservoir to the Portneuf River were stopped prematurely on July 

22 during the 2001 irrigation season and on July 20 during 

the 2002 irrigation season because of a lack of water in storage in the reservoir. Prior to the drought that began in 1999 

and continues to the present (2002), there were many years 

when Chesterfield Reservoir would completely refill prior 

to the irrigation season, and releases from the dam would 

continue throughout the growing season into mid-September. 

The premature cessation of releases from the Chesterfield 

Reservoir to the Portneuf River during the middle of summer 

MEAN MONTHLY STREAMFLOW,

IN CUBIC FEET PER SECOND

WATER YEAR

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13072000—U.S. Geological Survey gaging

 station near Pebble, Idaho (Discontinued)

13073000—U.S. Geological Survey

 gaging station at Topaz, Idaho

Figure 4. Mean monthly streamflow in the Portneuf River near Pebble and at Topaz, Idaho, 1968 – 2001.
Introduction 7

has been more frequent since the early 1990s as a result of 

drought conditions (Steve Hebdon, District Watermaster for 

the Portneuf River Marsh Valley Canal, oral commun., 2002). 

Between the end of streamflow releases and September 15, 

2001, streamflow (1 to 3 ft3/s) entering Chesterfield Reservoir 

was passed on downstream.

Ground-Water Conditions

In general, ground-water movement in the Portneuf 

Valley is from the uplands to the center of the valley, then 

southward downgradient in the direction of streamflow in the 

Portneuf River. Some ground water moves vertically upward 

through leaky confining strata where water-table aquifers are 

underlain by artesian aquifers (Norvitch and Larson, 1970). 

The water table is at or near the land surface near Grim 

Springs (fig. 2) in the south-central part of the valley. Numerous springs are located about 2 mi upstream from Pebble in 

the southwestern part of the Portneuf Valley (fig. 5). Supply 

wells and irrigation wells in the study area are completed principally in alluvial and colluvial deposits of Quaternary age. 

These deposits are composed of soil, clay, silt, sand, gravel, 

and boulders. A few irrigation wells are completed in basalt 

of Quaternary age (Norvitch and Larson, 1970; Lewis and 

Peterson, 1921). 

The water-table aquifer is recharged by (1) snowmelt 

runoff from the adjacent mountains, (2) streams that flow out 

of the mountains onto the alluvial plain and lose their entire 

discharge to the water-table aquifer or are diverted for irrigation, (3) precipitation that falls on the valley floor and percolates to the water table, (4) leakage from irrigation canals and 

ditches, (5) recharge from irrigated fields, and (6) possibly 

leakage from the southern part of the Chesterfield Reservoir 

(Norvitch and Larson, 1970). During periods of increased 

mountain snowpack, water levels in irrigation well 07S 39E 

10CCD1 (period of record is 1968 to present) tend to rise (fig. 

6). During periods of decreased mountain snowpack, water 

levels in this well tend to decline. Hence, aquifer recharge 

from snowmelt runoff from the adjacent mountains is significant and perhaps the dominant source of water to the valley 

aquifer system. Ground water discharges from the water-table 

aquifer by (1) seepage up through the riverbed of the Portneuf 

River, (2) spring flow or seeps along the banks of the stream 

channels, (3) evapotranspiration at places where the water 

Figure 5. Spring located about 0.3 mile upstream from measurement station 8SP and 200 feet east of the Portneuf River in 

the southwestern part of the Portneuf Valley, Idaho, July 2001.
8 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001 – 02

table is near land surface and within reach of phreatophytes, 

and (4) withdrawals from irrigation wells (Norvitch and Larson, 1970).

Ground-water allocations for irrigation increased more 

than a thousandfold in the valley from 1951 to 1978 when 

dryland farming expanded considerably. However, because 

ground-water withdrawals are not measured in the valley, 

the amount of water pumped on an annual basis since the 

1950s is not known. Water-rights (decreed, statutory claim, 

and licensed) data are used as surrogate data to provide some 

generalizations about ground-water usage. Between 1951 

and 1978, the number of ground-water withdrawal rights in 

the valley increased from 12 to 157. The allocated amount 

of withdrawals for all wells combined increased at nearly a 

constant rate (fig. 7). A moratorium has been placed on new 

water rights, with a few minor exceptions, since the late 1970s. 

Beginning in the 1980s to present, the combined water rights 

for ground-water withdrawals in the valley have been constant 

at about 46,000 acre-ft per year. 

Methods of Investigations

Fieldwork was conducted during July 2001 through July 

2002. Seepage studies provided the foundation of the field 

approach and were used to understand the relations between 

streamflow and adjacent ground-water movement. Seepage studies in the Portneuf River Valley reach consisted of 

measurements of (1) streamflow; (2) differences in hydraulic 

head between the surface-water stages and ground-water levels 

measured at instream piezometers; (3) water quality measured at instream piezometers and at selected springs; and (4) 

continuous water temperature. Seepage studies in the PebbleTopaz reach consisted of direct measurements of streamflow. 

Each of these methods is described in following sections of the 

report.

Numbering and Location of Measurement 

Stations

Eight measurement stations, 1S through 8SP, were 

located along the 10.2-mi-long Portneuf River Valley reach 

(fig. 2), and six measurement stations, 9S through 13S, were 

located along the 20-mi-long Pebble-Topaz reach (fig. 3). 

Station 8SP is on the border shared by both the Portneuf River 

Valley and Pebble-Topaz reaches. Locations of the measurement stations were selected on the basis of accessibility, safety, 

ease of measurement, and availability of a bridge from which 

to measure streamflow. An attempt was made to establish 

measurement stations downstream from known seeps.

Measurement stations were numbered using a 15-digit 

site identifier (SID) consisting of the latitude and longitude, 

followed by a two-digit sequence number beginning “01,” and 

Figure 6. Water levels in irrigation well 07S-39E-10CCD1 and water-equivalent snowpack during April at Pebble Creek station, 

1968 – 2002. (Water-equivalent snowpack data from Natural Resources Conservation Service, 1993) WATER-EQUIVALENT SNOWPACK, IN INCHES

YEAR

WATER LEVEL BELOW LAND SURFACE, IN FEET

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Water level

Snowpack
Methods of Investigations 9

were assigned a measurement station name. Information for 

each measurement station is stored under the SID and station name in the USGS National Water Information System 

data base. A local identifier was established for measurement stations, consisting of a single number increasing in the 

downstream direction. The suffix “S” on the local identifier 

indicates that streamflow was measured, “P” indicates that 

an instream piezometer was installed, and “T” indicates that 

a second instream piezometer equipped with thermistors was 

installed.

Timing of Seepage Studies

Seepage studies in the Portneuf River Valley reach were 

conducted over a range of hydrologic conditions to characterize the seasonality of surface- and ground-water relations: (1) 

spring regulated high flows at the start of the irrigation season 

on May 29, 2002; (2) mid-summer regulated high flows during 

the irrigation season during July 16 – 17, 2001; (3) late-summer base flows during the irrigation season on August 13, 

2001; (4) early-fall regulated low flows at the end of the irrigation season on September 17, 2001; and (5) mid-fall regulated 

low flows during the post-irrigation season on October 18, 

2001. Seepage studies in the Pebble-Topaz reach were conducted only during hydrologic conditions (1), (4), and (5).

High-flow conditions during seepage studies (1) and (2) 

on the Portneuf River are controlled by the release of water 

from storage in the Chesterfield Reservoir and herein are 

referred to as regulated high-flow conditions. Seepage study 

(3) was conducted when only the natural streamflow entering the Chesterfield Reservoir was diverted downstream and 

herein is referred to as base-flow conditions. Seepage studies 

(4) and (5) were conducted when the release of all flow from 

Chesterfield Dam was stopped and herein are referred to as 

regulated low-flow conditions.

During seepage study (2), consecutive streamflow 

measurements were averaged and used as the mid-summer 

regulated high-flow measurements. During July 10 – 12, 2001, 

a few days prior to the streamflow measurements, instream 

piezometers were installed at eight measurement stations (fig. 

8). Immediately after the installation of an instream piezometer, hydraulic head and water-quality properties were measured. During the same period, water quality was measured at 

mid-depth across the river at station 8SP and at nearby springs. 

During this period, four instream piezometers equipped with 

multiple thermistors were installed and began monitoring the 

temperature of the streamflow and riverbed.

Daily precipitation data were used to indicate the stability of streamflow conditions during each seepage study. The 

most complete record of daily precipitation near the study area 

was obtained at the weather station at the Pocatello (39 mi 

west of the study area) regional airport (National Oceanic and 

Atmospheric Administration, http://lwf.ncdc.noaa.gov/oa/

ncdc.html). These data (fig. 9) provide a general indication of 

ALLOCATED WITHDRAWALS, IN ACRE FEET PER YEAR

YEAR

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Figure 7. Growth in allocated ground-water withdrawals in the Portneuf Valley, Idaho, 1900 – 2000. (Data from Idaho 

Department of Water Resources, 1993)
10 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

precipitation in the study area because precipitation in intermontane basins is highly dependent upon altitude and general 

topography. Apparently, no significant precipitation fell 

prior to the seepage studies except during the May 29, 2002, 

study. During these studies, the dry soils could readily absorb 

the small amount of precipitation that fell and any effect on 

streamflow would be negligible. However, 6 days prior to the 

May 29, 2002, study, about 1 in. of rain fell during a 48-hour 

period. Because of the 6-day lapse between the rainfall and the 

seepage run, storm-related inflows downstream from Chesterfield Reservoir would have receded and streamflow in the 

Portneuf River would have stabilized.

Measuring Differences in Hydraulic Head 

Between Surface-Water Stages and GroundWater Levels

The differences in hydraulic head were measured at 

instream piezometers by means of a manometer board. 

Piezometers consisted of a 1/

2

-in. (inside diameter) steel pipe 

with a pointed bottom. Twenty-four 1/

8

-in.-diameter openings 

in the lower 6 in. of the piezometer served as a well screen 

(fig. 10). The piezometers were driven into the riverbed with 

a portable safety hammer to depths ranging from 2.0 to 7.7 

ft below the riverbed. To ensure that the piezometers were in 

good hydraulic connection with the surrounding aquifer, a 

portable peristaltic pump was used to inject water into or withdraw water from the piezometers. This pumping forced water 

through the 1/

8

-in. openings of the piezometers and removed 

the fine-grained sediments that clogged the openings during 

installation. Piezometer installations were considered complete 

when the pumping action was halted and water levels inside 

the piezometer equilibrated rapidly with water levels in the 

surrounding aquifer. Location and construction information 

for piezometers is given in table 1.

A calibrated manometer board was used to measure the 

difference in hydraulic head between the surface-water stage 

in the river outside the piezometer and the ground-water level 

in the piezometer. The manometer’s accuracy was 1 mm (0.04 

in.). Measurement precision—consecutive water-level measurements over a brief period—varied depending on the extent 

of wave action on the river surface. Typically, measurement 

precision was roughly 3 mm (0.12 in.). To mute the effects 

Figure 8. Instream piezometer used to continuously monitor the temperature of the Portneuf River and of ground water and 

to measure hydraulic head of surface and ground water at measurement station 3SPT in the Portneuf River Valley reach, 

Idaho, July 2001.

Instream piezometer
Methods of Investigations 11

of waves and flowing water on measurement precision, the 

manometer’s surface-water line was inserted through a small 

opening in a 2-in.-diameter cylinder (stilling well) that was 

attached to the piezometer. Detailed descriptions of the use of 

manometers and instream piezometers are provided in a report 

by Winter and others (1983) and, in relation to work in Idaho, 

are described in a report by Barton (2002).

Manometer measurements were used to identify zones of 

upward gradient (ground-water levels higher than river stage), 

downward gradient (river stage higher than ground-water levels), and no gradient (ground-water levels equal to river stage). 

Water moves from zones of high hydraulic head to zones of 

low hydraulic head; thus, an upward gradient indicates potential seepage of ground water to the river (gaining river reach); 

a downward gradient indicates potential seepage of river water 

to ground water (losing river reach); no gradient indicates no 

movement of water across the riverbed (Winter and others, 

1983). Because the piezometers completed in the sandy riverbed of the Portneuf River easily yielded water, there is a good 

hydraulic connection between the river and the underlying 

aquifer, and an upward or downward hydraulic head gradient 

will readily force water through the riverbed.

DAILY PRECIPITATION, IN INCHES

2001 2002

MONTHLY PRECIPITATION, IN INCHES

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Figure 9. Daily and monthly precipitation at Pocatello regional airport, Idaho, 2001 – 02. (Data from National Oceanic and 

Atmospheric Administration, National Climatic Data Center, 1993)
12 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

Measuring Water Quality 

During July 10 – 12, 2001, pH, dissolved oxygen, 

specific conductance, and temperature of surface and ground 

water were measured onsite using a Hydrolab Minisonde 

4-A multiparameter probe. For ground-water measurements, 

piezometers were purged until water-quality properties were 

stable prior to recording a measurement. For surface-water 

measurements, the Hydrolab Minisonde was dipped into 

the river to mid-depth and measurements were made in a 

flow-through chamber attached to the Minisonde. To ensure 

accurate measurements, the Minisonde was calibrated at the 

beginning of each day. Probes were submerged in a standard 

solution prior to all measurements, and the meters were recalibrated on an as-needed basis.

Using Heat as a Tracer to Monitor Surface- and 

Ground-Water Relations 

Concepts

Temperature gradients between a stream and adjacent 

ground water are controlled by the movement of water 

through the riverbed. Heat flows continuously between 

surface water and adjacent ground water and, hence, can be 

used as a tracer of water movement between the surface and 

subsurface. The use of heat as a tracer relies on the measurement of temperature fluctuations in the surface water 

and within the upper several feet of the riverbed sediments. 

Heat is transferred down into and up through the riverbed as 

a result of several mechanisms. Heat conduction occurs as 

solar radiation is absorbed by the riverbed surface and surface water. This is the dominant mechanism for heating a dry 

riverbed but is only a small component of heat transfer to the 

riverbed beneath a flowing stream. Conductive heat transfer 

occurs by the diffusive molecular transfer of heat by direct 

contact between two materials of dissimilar temperatures. 

Convective heat transfer occurs by the movement of water as 

it flows over riverbed sediments of dissimilar temperature. 

Similarly, advective heat transport occurs as water infiltrates 

in a downward or upward direction through the riverbed 

sediments. More detailed descriptions of these processes are 

given in a report by Constantz and Stonestrom (2003).

The idealized hydraulic and thermal responses within 

a cross section of a gaining stream and a losing stream are 

shown in figure 11. The thermal response depicts conditions 

during the summer and early fall when the surface water is 

relatively warmer than ground water. 

Three valves for flushing air from

manometer water lines and adjusting

water level in manometer board tubes

Manometer board with scale

for reading difference between

hydraulic head of ground-water

level and surface-water stage

Peristaltic pump for pumping

ground water and surface water

into the manometer board

8-inch-diameter cylinder for

muting the degrading effects that

ripple action and flowing water

have on measurement precision

1/2-inch-diameter steel pipe (minipiezometer) with

twenty-four 1/8-inch-diameter openings near the

drive point. Openings serve as a well screen.

Pipe driven into subsurface with safety hammer

Figure 10. Schematic of instream piezometer and manometer board.
Table 1. Descrip tion of measurement stations and construction information for instream piezometers at measurement stations on the Portneuf River, [Locations shown in figures 2 and 3; S, streamflow measured; P, instream piezometer installed; T, second instream piezometer equipped with thermistors installed; —, not applic

Measurement 

station local 

identifier

USGS Ground Water Site Inventory data base USGS Surface Water Data System

Latitude Longitude

Dep

Site identifier Station name 

Site

identifier Station name

Top 

ope

inte

1S —

Portneuf River #8 in relic 

channel 13071010

Downey Canal Portneuf River #8 

in relic channel

1SP 1 425209111555901 Portneuf River Piezo D-LB 13070505

Downey Canal Portneuf River 

#7 at site D 42°52’08.9” 111°55’58.5” 5

2SPT 425205111560101 Portneuf River Piezo G-LB 13070505

Downey Canal Portneuf River 

#7 at site G 42°52’04.8” 111°56’01.1” 4

2SPT 2 425205111560102 Portneuf River Piezo GT-LB 42°52’04.8” 111°56’01.1” 43SPT 425109111560101 Portneuf River Piezo E-LB 13071600 Portneuf River #6 at site E 42°51’09.2” 111°56’00.5” 53SPT 2 425108111555901 Portneuf River Piezo ET-LB 42°51’08.2” 111°52’59.0” 44P 425016111560301 Portneuf River Piezo H-LB 42°50’15.9” 111°56’03.2” 55SP 424921111560201 Portneuf River Piezo C-LB 13071700 Portneuf River #5 at site C 42°49’21.4” 111°56’02.3” 56SPT 424809111565501 Portneuf River Piezo B-LB 13071800 Portneuf River #4 at site B 42°48’09.0” 111°56’54.7” 76SPT 2,3 424809111565401 Portneuf River Piezo BT-RB 42°48’09.4” 111°56’54.3” 37SPT 424714111584401 Portneuf River Piezo A-LB 13072000 Portneuf River #3 at site A 42°47’13.6” 111°58’44.2” 37SPT 2 424715111584201 Portneuf River Piezo AT-RB 42°47’14.8” 111°58’42.3” 38SP 424623111592901 Portneuf River Piezo F-LB 13072040 Portneuf River #2 at site F 42°46’23.3” 111°59’28.6” 19S 13072400

Portneuf River #1 at Mike’s 

Place

10S 13072550

Portneuf River at Symmons 

Road

11S 13072600

Portneuf River above Lava Hot 

Springs

12S 13072810

Portneuf River below Lava Hot 

Springs

13S 13073000 Portneuf River at Topaz14S 13072500 Pebble Creek near Pebble15S 13072790

Fish Creek above Lava Hot 

Springs

1 Instream piezometer located near the left bank of the Portneuf River when facing downstream.2 Thermistors suspended inside piezometer at depths of 20 and 40 inches below riverbed. A thermistor also strapped to outside of piezometer near the river bottom.3 Instream piezometer located near the right bank of the Portneuf River when facing downstream.
14 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

In a gaining stream reach, the hydraulic gradient of water 

through the riverbed is upward as indicated by the flow lines in 

the riverbed on figure 11A. The thermal response graph shows 

a large diurnal variation in stream water temperature but only a 

slight diurnal variation in riverbed temperature resulting from 

the continuous inflow of ground water to the stream. Ground 

water is generally of constant temperature throughout the day. 

Furthermore, ground water seeping into a stream can reduce 

temperature fluctuations in the river if the volume of seepage 

is sufficient. During the summer and early fall, surface water is 

relatively warmer than ground water. Hence, the temperature 

of the riverbed in a gaining reach is a reflection of advective 

heat transport as ground water moves up through the riverbed 

and discharges into the stream. Under these conditions, the 

riverbed temperature will be lower than that of surface water. 

In a losing stream reach, the hydraulic gradient of water 

through the riverbed is downward, as indicated by the flow 

lines in figure 11B. Thus, the downward flow transports heat 

from the stream into the riverbed. The combined convective 

and advective heat transport causes diurnal fluctuations in the 

riverbed temperature. Furthermore, since ground water is not 

flowing into the stream, stream temperature variations in losing streams are generally larger than those in gaining streams 

(Constantz and Stonestrom, 2003). The magnitude of diurnal temperature fluctuations in the shallow sediments of the 

riverbed is affected by the rate of downward flow, the thermal 

conductivity of the sediment, and other factors.

Instrumentation

At measurement stations 2SPT, 3SPT, 6SPT, and 7SPT 

(table 1), an array of three thermistors was used to monitor 

the temperature of the stream and riverbed. At these stations, a 1.25-in.-diameter steel piezometer was hand driven 

and developed by using a surge block and pumping with a 

peristaltic pump. Onset Optic StowAway thermistors were 

suspended on a nylon line at 20 and 40 in. below the riverbed 

inside the piezometer. An Onset StowAway Tidbit thermistor 

was strapped to the outside of the piezometer casing near the 

riverbed to monitor surface-water temperature. The datarecording interval was 30 or 60 minutes. The accuracy of 

Optic StowAway and StowAway Tidbit thermistors is ±0.8o 

and ±0.9oF at 70oF (±17.2o and ±17.3oC at 21oC), respectively. 

The temperature measurement ranges of the Optic StowAway 

and StowAway Tidbit thermistors are -4o to +122oF (-15.6o to 

+50oC) and -32o to +167oF (-36o to +75oC), respectively.

Thermistor strapped to outside of piezometer in water column and thermal response

Thermistor inside piezometer at 20 inches below riverbed and thermal response

Thermistor inside piezometer at 40 inches below riverbed and thermal response

Flow direction Flow direction

Unsaturated zone

Water table

Shallow aquifer

Piezometer

Unsaturated zone

Water table

Piezometer

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Direction of

water movement

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Direction of

water movement

Time

Temperature

Time

Temperature

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Figure 11. Surface- and ground-water relations and thermal response during summer and early fall in streams with (A) gaining reaches and (B) losing reaches. (Modified from Winter and others, 1998, figs. 8 and 9)
Methods of Investigations 15

Measuring Streamflow

Streamflow was measured at seven measurement stations in the Portneuf River Valley reach during a single day, 

referred to as a seepage run. In addition, streamflow was 

measured at seven measurement stations in the Pebble-Topaz 

reach (table 2) during a single day. Seepage runs were used to 

delineate gaining or losing river reaches and indicate areas of 

streamflow depletion. Streamflow was measured using PriceAA current meters. All measurements were rated subjectively 

for accuracy on the basis of flow and cross-section conditions 

(within 2 percent, excellent; 5 percent, good; 8 percent, fair; 

greater than 8 percent, poor). The amount of nonmeasurable 

flow (for example, nonchannelized overland flow) was estimated visually. The variance in fluctuating streamflow within 

each study reach was monitored during repeat seepage runs 

over a 2-day period in July 2001.

Diversion of surface water for irrigation during seepage 

runs was monitored and reported by the District Watermaster 

of the Portneuf River Marsh Valley Canal (table 2). A headgate, located between measurement stations 2SPT and 3SPT 

on the Portneuf River, operated by a landowner, provided 

some level of control over streamflow and could have caused 

some variance in streamflow. No inflows, besides springs, 

were observed in the Portneuf River Valley reach.

Measuring Ground-Water Levels

To determine the temporal changes in ground-water levels 

in the Portneuf Valley since 1968, a monitoring well network 

was established for measuring ground-water levels. For this 

study, all wells in the area with previous water-level data were 

inventoried and water levels were measured.

The Portneuf Valley ground-water-level monitoring network consisted of 33 wells; 5 were unused observation wells 

and 28 were irrigation wells (fig. 2). These wells were also 

part of the monitoring network used in the previous USGS 

study (Norvitch and Larson, 1970). The network included 

wells located near the Portneuf River and in areas of large 

ground-water withdrawals. Well depths ranged from 31.9 to 

367 ft below land surface, and the median well depth was 131 

ft below land surface. Each well’s top of open interval ranged 

from 0 to 90 ft below land surface, and the bottom of the open 

interval ranged from 34 to 272 ft below land surface. Eight 

wells lacked this construction information. Water levels were 

measured several times between July 2001 and July 2002. 

Hydrographs showing water-level measurements are provided 

in appendix 1 (back of report). 

Quality Assurance

Good quality-assurance practices help to maintain the 

accuracy and precision of measurements, ensure that field 

STREAMFLOW, IN CUBIC FEET PER SECOND

2SPT 3SPT 5SP 6SPT 7SPT 8SP

1SP

RIVER MILE DOWNSTREAM FROM CHESTERFIELD RESERVOIR

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4.7 cubic feet per second removed at

Perkins diversion during July 16–17

(Data from Idaho Department of

Water Resources, 1993)

Grim

Springs Several

unnamed springs

July 16, 2001, streamflow measurement

July 17, 2001, streamflow measurement

Mean

Five percent error bar

5SP Measurement station and identifier

Headgate

Figure 12. Variability in streamflow at measurement stations in the Portneuf River Valley reach, Idaho, July 16 – 17, 2001. 

(Headgate is privately operated and provides some level of control over streamflow, resulting in variability between 

consecutive seepage runs)
Table 2. Streamflow, surface-water diversions, and calculated gains and losses in streamflow between measurement stations on the Portneuf River, [Station locations shown in figures 2 and 3; station descriptions shown in table 1; ft3/s, cubic feet per second; —, no data] Measurement stations, diversions1, and tributaries

River miles downstream from Chesterfield Dam7/16-17/2001 2 Irrigating fields, mid-summer regulated high flows 8/13/2001 Irrigating fields, late-summer base flows 9/17-18/2001 Irrigating fields, early-fall regulated base flows 3 10/17-18/2001 No irrigation, mid-fall regulated flows3 

Reach quantified for gains and losses resulting from seepage Reach quantified for gains and losses resulting from seepage Reach quantified for gains and losses resulting from seepage Reach quantified for gains and losses resulting from seepage 

Streamflow, in ft

3

/s

Upstream station

Downstream station

Gain or loss4, in ft

3

/s 

Streamflow, in ft

3

/s

Upstream station

Downstream station

Gain or loss4, in ft

3

/s 

Streamflow, in ft

3

/s

Upstream station

Downstream station

Gain or loss4, in ft

3

/s 

Streamflow, in ft

3

/s

Upstream station

Downstream station

Gain or loss4, in ft

3

/s 

Chesterfield Dam 5 0 115 — — — 5 — — — 0 — — — 0 — — — Perkins diversion 6 4.7 — — — 3 — — — 0 — — — 0 — — — 1S (relic river below dam) 0.6 — — — — 4 — — — 1.0 — — — — — — — 2SPT 5 0.9 105 dam 2SPT -5.8 4 1SP 2SPT 2 1.0 dam 2SPT 0 0.8 dam 2SPT — Perkins-Crandall diversion 2.1 0 — — — 0 — — — 0 — — — 0 — — — 3SPT 2.2 116 2SPT 3SPT 11.5 3 2SPT 3SPT -1 0 — — — 0.9 2SPT 3SPT 0.1 Crandall diversion 2.5 0 — — — 0 — — — 0 — — — 0 — — — 5SP 4.3 114 3SPT 5SP -2.1 1.5 3SPT 5SP -1.5 0.8 2SPT 5SPT -0.2 1.7 3SPT 5SP 0.8 Carl Phillips diversion 5.2 0 — — — 0 — — — 0 — — — 0 — — — 6SPT 6.2 99.9 5SP 6SPT -14.8 2.0 5SP 6SPT 0.5 — — — — 0.9 5SP 6SPT -0.8 7SPT 8.6 96.8 6SPT 7SPT -3.1 2.5 6SPT 7SPT 0.46 0.6 5SPT 7SPT -0.2 3.2 6SPT 7SPT 2.3 8SP 10.2 98.4 7SPT 8SP 1.6 2.9 7SPT 8SP 0.42 1.3 7SPT 8SP 0.7 5.7 7SPT 8SP 2.5 9S 12.2 — — — — — — — — 48.1 8SP 9S 46.8 44.7 8SP 9S 39.0 Pebble Creek 13 — — — — — — — — 5.6 — — — 5.5 — — — Dempsey-Topaz Ditch 17 — — — — — — — — 0 — — — 0 — — — 10S 19.0 — — — — — — — — 72.8 9S 10S 19.1 65.0 9S 10S 14.8 Shane Irick Ditch 19.3 — — — — — — — — 0 — — — 0 — — — Indian Falls diversion 20.7 — — — — — — — — 0 — — — 0 — — — Christiansen Ditch 21 — — — — — — — — 0 — — — 0 — — — Lava Irrigation Ditch 21.2 — — — — — — — — 0 — — — 0 — — — 
Table 2. Streamflow, surface-water diversions, and calculated gains and losses in streamflow between measurement stations on the Portneuf River, I[Station locations shown in figures 2 and 3; station descriptions shown in table 1; ft3/s, cubic feet per second; —, no data] 

Measurement stations,

diversions1, and tributaries

River miles downstream from Chesterfield Dam7/16–17/2001 2 Irrigating fields, mid-summer regulated high flows 8/13/2001 Irrigating fields, late-summer base flows 9/17–18/2001 Irrigating fields, early-fall regulated base flows 3 10/17–18/2001 No irrigation, mid-fall regulated flows3 

Reach quantified for gains and losses resulting from seepage Reach quantified for gains and losses resulting from seepage Reach quantified for gains and losses resulting from seepage Reach quantified for gains and losses resulting from seepage 

Streamflow, in ft

3

/s

Upstream station

Downstream station

Gain or loss4, in ft

3

/s 

Streamflow, in ft

3

/s

Upstream station

Downstream station

Gain or loss4, in ft

3

/s 

Streamflow, in ft

3

/s

Upstream station

Downstream station

Gain or loss4, in ft

3

/s 

Streamflow, in ft

3

/s

Upstream station

Downstream station

Gain or loss4, in ft

3

/s 

Fish Creek 24.1 — — — — — — — — 0.14 — — — 1.0 — — — 11S 24.2 — — — — — — — — 16.2 10S 11S -56.7 45.7 10S 11S -20.3 12S 27.0 — — — — — — — — 52.3 11S 12S 36.1 58.4 11S 12S 12.7 13S 30.2 — — — — — — — — 72.1 12S 13S 19.8 62.4 12S 13S 4.0 Streamflow depletion in the Portneuf River Valley reach 

resulting from surface water seeping down through the riverbed, excluding reach between dam and station 2SPT, in ft3/s -19.2 -2.5 -0.4 -0.8 

Streamflow depletion in the Pebble-Topaz reach resulting 

from surface water seeping down through the riverbed, in ft3/s 7 — — — — 

1Approximate river miles downstream from Chesterfield Dam.2 Mean streamflow for July 16-17, 2001.3 Streamflow measurements on September 18, 2001, October 17, 2001, and May 30, 2002, conducted in the Pebble-Topaz reach. Streamflow measurements on September 17, 

May 29, 2002, conducted in the Portneuf River Valley reach.

4 Gains and losses in streamflow between measurement stations resulting from water seeping through the riverbed, calculated as streamflow minus tributary inflow plus surfac5 Idaho Department of Water Resources reported flow from Chesterfield Reservoir to be 115 and 112 ft3/s during July 16–17, 2001, respectively. These measurements may be 

between the dam and station 2SPT appeared to be losing 5.8 ft3/s, adjusted for diversions, on July 16, 2001. During May 29–30, 2002, flow from the dam may be biased high, reft3/s. All other field data collected indicate this is a gaining reach; for example, manometer measurements at instream piezometers at stations 1SP and 2SPT showed that ground-surface-water stages. The loss in streamflow cannot be explained with the existing data.

6 Streamflow measurementmade by the U.S. Geological Survey; the Idaho Department of Water Resources reported a flow of 3.5 ft3/s on July 16, 2001.7 Streamflow depletion could not be computed between measurement stations 10S and 12S because flow data for the hydroelectric project located within this reach were not p

Survey.
18 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02 STREAMFLOW PLUS DIVERSIONS, IN CUBIC FEET PER SECOND

2SPT 3SPT 5SP 6SPT 7SPT 8SP

RIVER MILE DOWNSTREAM FROM CHESTERFIELD RESERVOIR

1SP

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Springs

1.0 cubic foot per second

measured at SP1 near Perkins

diversion on September 17, 2002

Several

unnamed springs

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Gaining reach

Neutral reach

Losing reach

August 13, 2001—dam not releasing water, farmers irrigating fields

September 17, 2001—dam not releasing water, farmers irrigating fields

October 18, 2001—dam not releasing water, no irrigation

July 16–17, 2001 (Mean)—dam releasing water (115 and 112 cubic feet

 per second each day, respectively), farmers irrigating fields, water not

 being diverted from river

May 29, 2002—dam releasing water (99 cubic feet per second), farmers

 irrigating fields

Five percent error bar

Perkins diversion—4.7 cubic feet per second removed during July 16–17,

 2001; 4.3 cubic feet per second removed on May 29, 2002

Crandall diversion—7.5 cubic feet per second removed on May 29, 2002

Carl Phillips diversion—1.5 cubic feet per second removed on May 29, 2002

5SP Measurement station and identifier

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Figure 13. Streamflow adjusted for diversions at measurement stations and location of gaining and losing reaches in the 

Portneuf River Valley reach, Idaho, 2001 – 02. (Diversion data from Idaho Department of Water Resources, 1993)
Seasonality of Surface- and Ground-Water Relations on the Portneuf River 19

measurements reflect actual conditions being monitored, and 

provide reliable data for many uses. During seepage runs, the 

streamflow measurements, computation of streamflow, and 

quality-assurance procedures followed standardized USGS 

methods described by Rantz and others (1982). Manometer 

operation and quality-assurance procedures followed methods 

described by Barton (2002). Ground-water-level measurements and quality-assurance procedures followed standardized 

methods outlined in the USGS Idaho District’s Ground Water 

Quality Assurance Plan.

The principal source of error in characterizing and delineating gaining and losing river reaches during regulated highflow conditions is associated with the variability in streamflow 

and diversions during seepage runs. The variability in 

streamflow at measurement stations was documented during 

consecutive seepage runs during July 16 – 17, 2001 (fig. 12). 

Releases from Chesterfield Reservoir during consecutive seepage runs were constant as measured at station 2SPT, less than 

1 mi downstream from the reservoir. However, streamflow 

during consecutive seepage runs at measurement station 5SP 

increased from 98.7 ft3/s on July 16 to 129 ft3/s on July 17. 

This variability is in excess of measurement error and is the 

result of changes at a headgate located between measurement 

stations 2SPT and 3SPT on the Portneuf River, which provides 

some level of control over streamflow. 

Seasonality of Surface- and GroundWater Relations on the Portneuf River

During the 10-month-long seepage studies on the Portneuf River, surface- and ground-water relations were dynamic. 

Significant elements of surface- and ground-water relations 

in the Portneuf River are a losing reach in the middle of the 

Portneuf River Valley reach and a gaining reach in the southern part of the valley extending downstream to station 10S. 

Results of the seepage studies from a seasonal perspective, 

beginning with spring and ending with mid-fall, are presented 

in the following paragraphs.

Gaining and losing river reaches in the Portneuf River 

Valley reach were delineated using analyses of streamflow 

measurements (fig. 13) and manometer measurements of 

hydraulic heads at instream piezometers (fig. 14). These 

delineations showed spatial variability between analyses based 

on streamflow measurements and analyses based on manometer measurements. Some of the variability is caused by the 

scale of investigation; a seepage run measurement integrates 

the suface- and ground-water relations between measurement stations, whereas a manometer measurement represents 

the surface- and ground-water relations at a specific location in the river. The ±5-percent error rating for streamflow 

measurements made during the seepage studies is a source 

of uncertainty in the analysis of surface- and ground-water 

relations. Because of the spatial variability inherent in the two 

field methods, and because of the ±5-percent error, delineation of gaining and losing reaches in the Portneuf River Valley 

reach was based on an integrated analysis (hereafter referred 

to as integrated measurements) of streamflow, hydraulic head, 

specific conductance, and temperature (fig. 15).

Spring Regulated High Flows at the Start of the 

Irrigation Season 

A seepage run was conducted in the Portneuf River 

Valley reach (fig. 2) on May 29, 2002, during regulated high 

flows at the start of the irrigation season. Streamflow ranged 

from 92.7 to 116 ft3/s at seven measurement stations (table 

2). During the spring high flows in the Portneuf River, a large 

percentage of flow in the river is water released from storage in the Chesterfield Reservoir (fig. 13). The Chesterfield 

Reservoir was releasing about 99 ft3/s at the time of this seepage study (Steve Hebdon, Watermaster for the Portneuf River 

Marsh Valley Canal, oral commun., 2002). A 6.3-ft3/s loss in 

streamflow was measured between the dam and measurement 

station 2SPT; 4.3 ft3/s of this loss is attributed to surface-water 

diversion, and the remaining 2.0 ft3/s of loss may be attributed 

to measurement error. Manometer measurements at stations 

1SP and 2SPT showed that the hydraulic head of ground water 

was greater than surface-water stage, which indicates that 

ground water was seeping up through the riverbed. 

Integrated measurements of streamflow and hydraulic 

head in the Portneuf River Valley reach showed (1) a 4.9-milong gaining reach that extended from the dam to about 0.8 mi 

downstream from measurement station 6SPT; (2) a 2.6-milong losing reach in the middle of the valley (fig. 15), the 

center of which was near station 6SPT; and (3) a 2.8-mi-long 

gaining reach in the southern part of the valley. Manometer 

measurements at station 6SPT showed that the hydraulic head 

of ground water beneath the streambed was 105 mm (4 in.) 

below the surface-water stage (fig. 14), indicating that surface 

water was seeping down through the riverbed. Manometer 

measurements at all other stations showed that the hydraulic 

head of ground water beneath the streambed was greater than 

the surface-water stage, indicating that ground water was seeping up through the riverbed. Between stations 6SPT and 7SPT 

and between 7SPT and 8SP, ground water was seeping into the 

Portneuf River at about 12 and 10 ft3/s, respectively. Portneuf 

River streamflow not originating from the Chesterfield Reservoir is principally from springs and ground water seeping into 

the river between stations 6SPT and 8SP.

A seepage run was conducted in the Pebble-Topaz reach 

(fig. 3) on May 30, 2002. Streamflow in the Portneuf River 

ranged from 19 to 315 ft3/s at six measurement stations (fig. 

16), and the total diversion of streamflow was 42.2 ft3/s. 

Tributary inflows from Pebble and Fish Creeks were about 

89 and 2.5 ft3/s, respectively. A 136-ft3/s gain in streamflow 

along the 8.8-mi reach between stations 8SP and 10S is 

attributed to ground water seeping up through the riverbed. A 

283-ft3/s loss in streamflow along the 5.2-mi reach between 

stations 10S and 11S (table 2) may be the result of a hydro-
20 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

Figure 14. Differences in hydraulic head between river stages and ground-water levels at measurement stations and location 

of potential gaining and losing reaches in the Portneuf River Valley reach, Idaho, 2001 – 02. DIFFERENCE IN HYDRAULIC HEAD (GROUND-WATER LEVEL MINUS SURFACE-WATER STAGE), IN MILLIMETERS

3SPT 8SP

1SP

2SPT 5SP 6SPT 7SPT

RIVER MILE DOWNSTREAM FROM CHESTERFIELD RESERVOIR

4P

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Value for station 2SPT

on September 17, 2001,

is the average for

August 13, 2001, and

October 18, 2001 

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Gaining reach

Losing reach

August 13, 2001—dam not releasing water, farmers irrigating fields

September 17, 2001—dam not releasing water, farmers irrigating fields

October 18, 2001—dam not releasing water, no irrigation

July 16–17, 2001 (Mean)—dam releasing water, farmers irrigating fields

May 29, 2002—dam releasing water, farmers irrigating fields

5SP Measurement station and identifier

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Seasonality of Surface- and Ground-Water Relations on the Portneuf River 21

electric project located between these stations that stores 

water behind a cement impoundment structure. A 207-ft3/s 

gain in streamflow was measured along the 2.8-mi reach 

between stations 11S and 12S. This gain may be a result of 

the hydroelectric project returning water to the river between 

those stations during power generation. Flow data for this 

hydroelectric project during the seepage run was not available 

to the USGS; therefore, any withdrawal or release of water by 

this hydroelectric project could not be quantified. Because of 

this data gap, the surface- and ground-water relations between 

stations 10S and 12S could not be quantified. A 19-ft3/s gain 

in streamflow was measured along the 3.2-mi reach between 

stations 12S and 13S. Up to 2 ft3/s of this gain may be 

attributable to unmeasured tributary inflow; the remainder is 

attributed to ground water seeping up through the riverbed. 

Mid-Summer Regulated High Flows During the 

Irrigation Season

Seepage runs were conducted in the Portneuf River Valley reach (fig. 2) during July 16 – 17, 2001, during regulated 

high flows in the middle of the irrigation season. The Chesterfield Reservoir was releasing about 115 and 112 ft3

/s on July 

16 and 17, respectively (Tim Luke, Idaho Department of Water 

Resources, written commun., 2003). Streamflow ranged from 

97 to 116 ft3/s (2-day average) at seven measurement stations 

(fig. 12, table 2). During the summer high flows, a large percentage of flow in the river is water released from storage in 

the Chesterfield Reservoir. A 5.8-ft3/s loss in streamflow was 

measured between the dam and station 2SPT; 4.7 ft3/s of this 

loss is attributed to surface-water diversion, and the remaining 1.1 ft3

/s of loss cannot be explained. All other field data 

indicate that this is a gaining reach; for example, the manometer measurements at stations 1SP and 2SPT showed that the 

hydraulic head of ground water beneath the streambed was 

greater than the surface-water stage, indicating that ground 

water was seeping up through the riverbed (fig. 14).

The losing reach identified in the middle of the Portneuf River Valley reach near station 6SPT during the spring 

seepage study increased in length from 2.6 mi to nearly 6 

mi during the mid-summer seepage study (fig. 15). Manometer measurements showed that the losing reach expanded to 

include stations 5SP and 7SPT. Manometer measurements at 

stations 5SP, 6SPT, and 7SPT showed that ground-water heads 

ranged from 110 to 320 mm (4 to 13 in.) below the surfacewater stages (fig. 14), indicating that surface water is infiltrating down through the riverbed.

Figure 15. Location of gaining, neutral, and losing reaches in the Portneuf River Valley reach, Idaho, based on integrated 

analysis of streamflow, hydraulic head, specific conductance, and temperature, 2001 – 02.

3SPT 8SP

1SP

2SPT 5SP 6SPT 7SPT

RIVER MILE DOWNSTREAM FROM CHESTERFIELD RESERVOIR

4P

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unnamed springs

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Gaining reach

Neutral reach

Losing reach

August 13, 2001—dam not releasing water, farmers irrigating fields

September 17, 2001—dam not releasing water, farmers irrigating fields

October 18, 2001—dam not releasing water, no irrigation

July 16–17, 2001 (Mean)—dam releasing water, farmers irrigating fields

May 29, 2002—dam releasing water, farmers irrigating fields

5SP Measurement station and identifier

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22 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

Figure 16. Streamflow and location of gaining and losing reaches in the Pebble-Topaz reach, Idaho, 2001–02. ����������������������������������������������������

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Seasonality of Surface- and Ground-Water Relations on the Portneuf River 23

SPECIFIC CONDUCTANCE, IN

MICROSIEMENS PER CENTIMETER

TEMPERATURE,

IN DEGREES CELSIUS

3SPT 8SP

1P

2SPT 5SP 6SPT 7SPT

RIVER MILE DOWNSTREAM FROM CHESTERFIELD RESERVOIR

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Gaining reach—Location based on specific conductance

 and temperature of ground and surface water

Losing reach—Location based on specific conductance

 and temperature of ground and surface water

Surface water

Ground water

Measurement station and identifier—Instream piezometer

 installed to monitor ground- and surface-water levels and

 water quality

5SP

Gaining river is stratified,

specific conductance ranged

from 402 to 931 microsiemens

per centimeter at instream piezometer

Figure 17. Specific conductance and temperature at measurement stations in the Portneuf River Valley reach, Idaho, 

July 10–12, 2001. (Mid-summer regulated high flows and farmers irrigating fields)
24 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

Surface- and Ground-Water Relations Based on 

Specific Conductance and Temperature

A perspective on surface- and ground-water relations in 

the Portneuf River Valley reach was obtained from an analysis 

of specific conductance and temperature measured at instream 

piezometers during July 10 – 12, 2001. Specific conductance 

and temperature data showed that ground water was seeping 

into the river just downstream from Chesterfield Reservoir at 

stations 1SP, 2SPT, 3SPT, and 4P, and at station 8SP where the 

valley narrows upstream from the Pebble-Topaz reach. Specific conductance was about twice that of the river water, and 

ground water was several degrees cooler than river water in 

the gaining reach between stations 1SP and 4P (fig. 17). More 

dilute and warmer surface water infiltrated the riverbed in the 

losing reach between stations 5SP and 7SPT. Infiltration of 

relatively dilute surface water through the riverbed lowered the 

specific conductance of the ground water so that surface- and 

ground-water specific conductance were nearly equivalent. 

Infiltration of the warm surface water through the riverbed also 

increased ground-water temperatures to the extent that surfaceand ground-water temperatures were nearly equivalent. 

Stratification of specific conductance and temperature 

across the Portneuf River at measurement station 8SP is also 

an indicator of ground water seeping into the river. On July 11, 

2001, the water column of the Portneuf River was highly stratified from bank to bank (fig. 18). Instream water-quality measurements showed a ground-water signature near the left bank 

(facing downstream) and a surface-water signature between 

the river’s mid-section and the right bank. The specific conductance and temperature profile across the river—left bank 

to right bank—ranged from 931 to 402 μS/cm and from 10.6°

to 22.8°C, respectively (fig. 18). As a point of reference, at 

station 7SPT upstream from station 8SP, specific conductance 

of the surface water was 400 μS/cm. Sources of ground-water 

input at station 8SP are springs near the river’s left bank and 

ground water seeping through the riverbed. Specific conductance at a spring about 1,000 ft upstream from station 7SPT 

was 1,000 μS/cm and temperature was 9.6°C. The gaining 

reach at station 8SP most likely extends less than 2,100 ft 

TEMPERATURE, IN DEGREES CELSIUS

DISTANCE FROM LEFT BANK, IN PERCENT OF RIVER WIDTH

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER

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Temperature

Specific conductance

Location of

instream

piezometer

Ground-water

signature

Surface-water

signature

Figure 18. Specific conductance and temperature profiles across the Portneuf River, Idaho, at measurement station 8SP, July 

11, 2001.
Seasonality of Surface- and Ground-Water Relations on the Portneuf River 25

TEMPERATURE, IN DEGREES CELSIUS

JULY

MEASUREMENT STATION 2SPT

MEASUREMENT STATION 3SPT

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Surface-water temperature

Ground-water temperature at 20 inches

 below riverbed

Ground-water temperature at 40 inches

 below riverbed

Gates closed on Chesterfield Reservoir

 and flow ceases

Figure 19. Continuous record of surface- and ground-water temperatures at measurement stations 2SPT and 3SPT showing 

cool ground water discharging to the Portneuf River, Idaho, July 2001.
26 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

upstream from the station, because there are no springs, which 

are an indication of a gaining reach, located more than 2,100 

ft upstream from this station. A “dry” piezometer 2,100 ft 

upstream from station 8SP could not produce water because it 

encountered a very dense clay layer at 2 ft below the riverbed 

and was abandoned. The lateral extent of this nearly impermeable clay layer is not known but, where present, it would 

behave as a boundary to ground-water seepage through the 

riverbed.

Surface- and Ground-Water Relations Based on 

Continuous Temperature Data From Thermistor 

Arrays

During July 2001, continuous temperature data were collected by thermistor arrays at instream piezometers at stations 

2SPT and 3SPT. Thermographs for stations 2SPT and 3SPT 

(fig. 19) showed that (1) the riverbed was 2° to 6°C cooler than 

the surface water, and (2) no diurnal ground-water temperature 

fluctuations mimicking the diurnal surface-water temperature 

fluctuations were discernible. Conditions (1) and (2) indicate 

this is a gaining river reach where cooler ground water is 

seeping up through the riverbed. After Chesterfield Reservoir 

ceased releasing water on July 22, 2001, the surface-water 

temperature at stations 2SPT and 3SPT increased dramatically 

because the thermistors were exposed.

Thermographs for stations 6SPT and 7SPT (fig. 20) 

showed that (1) the riverbed and surface water were nearly 

the same temperature, and (2) the shallowest thermistor at 

20 in. below the riverbed recorded small diurnal fluctuations 

that mimicked the diurnal surface-water temperature fluctuations. The similarity between surface- and ground-water 

temperatures and diurnal fluctuations in the ground water is 

a result of surface water infiltrating the riverbed in this losing 

reach. After Chesterfield Reservoir ceased releasing water 

from storage on July 22, 2001, the surface-water temperature 

at station 6SPT increased dramatically because the thermistor 

was exposed. During the same period, diurnal fluctuations in 

surface-water temperatures at station 7SPT decreased. This 

decrease occurred because a small amount of ground water 

began seeping into the river, resulting in streamflow at station 

7SPT, which kept the thermistor submerged in flowing water. 

The source of this ground-water seepage may have been Grim 

Springs, upstream from station 7SPT.

Late-Summer Base Flows During the Irrigation 

Season

A seepage run was conducted in the Portneuf River 

Valley reach (fig. 2) on August 13 during late-summer base 

flow in the irrigation season. The Chesterfield Reservoir was 

releasing about 5 ft3/s on August 13, 2001 (Tim Luke, Idaho 

Department of Water Resources, written commun., 2003). At 

this time, the small amount of water in storage in the reservoir 

was not being released. The natural flow of water through the 

Chesterfield Reservoir provided flow to the Portneuf River 

(Steve Hebdon, Watermaster for the Portneuf River Marsh Valley Canal, oral commun., 2002). Flows in the Portneuf River 

during this seepage study (table 2) ranged from none to 4 ft3/s. 

Ground-water seepage in the reach between the reservoir and 

station 2SPT contributed about 2 ft3/s of flow. However, the 

streamflow measured farther downstream at station 5SP was 

less than 50 percent of that measured at the upstream station 2SPT. This streamflow loss indicates a losing river reach 

where surface water infiltrates down through the riverbed into 

the water-table aquifer because no surface water is diverted 

between these two stations. The losing reach in the middle of 

the Portneuf Valley near measurement station 6SPT is about 

6 mi long and similar in length to that measured during the 

mid-summer seepage study (fig. 15). Streamflow increased 

by about 1.4 ft3/s between stations 5SP and 8SP. Manometer 

measurements showed a losing reach between stations 4P and 

7SPT (fig. 14). Manometer measurements at stations 5SP and 

6SPT showed that the hydraulic heads of ground-water levels 

were 284 to 240 mm (11 to 9 in.) below the surface-water 

stages, respectively, indicating that surface water is seeping 

down through the riverbed.

Early-Fall Regulated Low Flows at the End of the 

Irrigation Season

A seepage run was conducted in the Portneuf River Valley reach (fig. 2) on September 17, 2001, during early-fall 

regulated low flows at the end of the irrigation season. No 

water was being released from the Chesterfield Reservoir to 

the Portneuf River. The lowest streamflows during this study 

were measured during the September seepage run. September 

streamflows at all stations (table 2) ranged from none to 1.3 

ft3/s. These minimum streamflows reflect conditions at the 

end of the irrigation season when climate and ground-water 

withdrawals can have the greatest impact on ground-waterlevel declines. These conditions are reflected strongly by 

manometer measurements (fig. 14) at station 5SP, where 

hydraulic heads declined substantially. The gaining reach 

upstream from station 8SP contributed about 0.7 ft3/s of water, 

which corresponds to manometer measurements at stations 

7SPT and 8SP, where hydraulic heads were rising.

A seepage run was conducted in the Pebble-Topaz reach 

(fig. 3) on September 18, 2001. Streamflow ranged from 1.3 

to 72.8 ft3/s at six stations (fig. 16, table 2), and no streamflow 

was being diverted. Tributary inflows from Pebble and Fish 

Creeks were 5.6 and 0.14 ft3/s, respectively. A 65.9-ft3/s gain 

in streamflow along the 8.8-mi reach between stations 8SP and 

10S is attributed to ground water seeping up through the riverbed; about two-thirds of the gain occurred between stations 8S 

and 9S. Along the 5.2-mi reach between stations 10S and 11S, 

the Portneuf River lost about 57 ft3/s of streamflow. This loss 

of streamflow may be the result of the hydroelectric project 

located between these stations. A 36-ft3/s gain in streamflow 
Seasonality of Surface- and Ground-Water Relations on the Portneuf River 27

TEMPERATURE, IN DEGREES CELSIUS

JULY

MEASUREMENT STATION 6SPT

MEASUREMENT STATION 7SPT

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Surface-water temperature

Ground-water temperature at 20 inches

 below riverbed

Ground-water temperature at 40 inches

 below riverbed

Gates closed on Chesterfield Reservoir

 and flow ceases

Approximated temperature of ground

water in gaining stream reach at

piezometers 2SPT and 3SPT

Figure 20. Continuous record of surface- and ground-water temperatures at measurement stations 6SPT and 7SPT showing 

warm stream water infiltrating down through the streambed in the Portneuf River, Idaho, July 2001.
28 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

was measured along the 2.8-mi reach between stations 11S 

and 12S. This gain may be a result of the hydroelectric project 

returning water to the river between those stations during 

power generation. Flow data for this hydroelectric project 

during the seepage run were not available to the USGS; therefore, any withdrawal or release of water by this hydroelectric 

project could not be quantified. Because of this data gap, the 

surface- and ground-water relations between stations 10S and 

12S could not be quantified. A 20-ft3/s gain in streamflow was 

measured along the 3.2-mi reach between stations 12S and 

13S. About 1 ft3/s of this gain may be attributable to unmeasured tributary inflow; the remainder is attributed to ground 

water seeping up through the riverbed. 

Mid-Fall Regulated Low Flows During the PostIrrigation Season

A seepage run was conducted in the Portneuf River Valley reach (fig. 2) on October 18, 2001, during regulated low 

flows after the irrigation season. No water was being released 

from the Chesterfield Reservoir. During the October seepage 

run, water was flowing at all measurement stations, in contrast 

to no-flow conditions observed at some measurement stations 

during the prior September seepage run (table 2). October 

flow decreased between stations 5SP and 6SPT, and manometer measurements at these stations showed that hydraulic 

heads of ground water were below the surface-water stages 

(fig. 14), indicating a losing reach about 5 mi in length (fig. 

15). Between stations 6SPT and 8SP, streamflow increased 

about sixfold to 5 ft3/s as a result of ground-water seepage 

up through the riverbed and spring discharge. Ground-water 

seepage measured during the early fall seepage run probably increased in response to the cessation of withdrawals by 

irrigation wells. During this period there was no measurable 

precipitation to cause such a response (fig. 9). Manometer 

measurements at station 7SPT showed that the hydraulic heads 

of ground water were greater than the surface-water stages 

(fig. 14), indicating gaining stream conditions in this area. 

Manometer measurements at station 6SPT showed that the 

hydraulic heads of ground-water levels were well below the 

surface-water stages, indicating losing stream conditions in 

this area. These manometer measurements indicate that the 

gaining reach may have extended about 0.7 mi upstream from 

station 7SPT.

During the seepage run in the Pebble-Topaz reach (fig. 

3) on October 17, 2001, streamflow ranged from 46 to 65 ft3/s 

at six stations (fig. 16, table 2), and no streamflow was being 

diverted. Tributary inflows from Pebble and Fish Creeks were 

5.5 and 1.0 ft3/s, respectively. The lowest streamflows in the 

Pebble-Topaz reach during this study were measured during 

the October seepage run. A 54-ft3/s gain in streamflow along 

the 8.8-mi reach between stations 8SP and 10S is attributed 

to ground water seeping up through the riverbed; about twothirds of the gain occurred between stations 8S and 9S. Along 

the 5.2-mi reach between stations 10S and 11S, the Portneuf 

River lost 20 ft3/s of streamflow. This loss of streamflow may 

be the result of the hydroelectric project located between these 

stations. A 13-ft3/s gain in streamflow was measured along 

the 2.8-mi reach between measurement stations 11S and 12S. 

This gain may be a result of the hydroelectric project returning water to the river between those stations during power 

generation. Flow data for this hydroelectric project during the 

seepage run were not available to the USGS; therefore, any 

withdrawal or release of water by this hydroelectric project 

could not be quantified. Because of this data gap, the surfaceand ground-water relations between stations 10S and 12S 

could not be quantified. A 4-ft3/s gain in streamflow was measured along the 3.2-mi reach between stations 12S and 13S. 

This gain is attributed to ground water seeping up through the 

riverbed. 

Streamflow Depletion

Streamflow depletion in the Portneuf River is related to 

the seasonality of water regulation, climatic conditions, and 

water usage. The two primary elements of streamflow depletion are: (1) losses resulting from surface water seeping down 

into the riverbed, and (2) losses resulting from surface-water 

diversions.

The river is hydraulically connected to the water-table 

aquifer, which is replenished partially by spring snowmelt 

runoff. Water in the aquifer attains its maximum level in the 

spring prior to the irrigation season, then declines during the 

summer and fall when recharge to the aquifer is minimal and 

ground-water withdrawals are maximum. Declines in water 

levels in the aquifer can, over a period of time, cause gaining 

river reaches to become losing reaches as surface water seeps 

down into the riverbed. It is not known whether the Portneuf 

River Valley reach had a losing reach prior to development of 

the Portneuf Valley. However, ground-water withdrawals for 

irrigation, evapotranspiration, and drought conditions increase 

the rate of water-level declines in the aquifer. Withdrawals of 

ground water for irrigation lengthen losing reaches and intensify the magnitude of streamflow depletion in losing reaches. 

No data are available to determine whether the Pebble-Topaz 

reach had a losing reach prior to regulation of streamflow; 

however, given the magnitude of the measured losses between 

stations 10S and 11S, existence of a losing reach in the 

Pebble-Topaz reach is probable.

Seepage studies indicated that streamflow depletion from 

surface water seeping down through the riverbed in the losing 

reach of the Portneuf River Valley reach ranged from 4.3 to 

20 ft3/s during the period of regulated high flows (table 2). 

This calculation does not include surface water seeping down 

through the riverbed between Chesterfield Dam and station 

2SPT. Measured streamflow at station 2SPT is less than flow 

at Chesterfield Dam minus the Perkins diversion. These measurements erroneously indicate that surface water is seeping 

down through the riverbed between the dam and station 2SPT; 

however, this indication of a losing reach is attributed to inac-
Temporal Changes in Ground-Water Levels in the Portneuf Valley 29

curate flow data for the Perkins diversion and the Chesterfield 

Dam. Manometer measurements at stations 1SP and 2SPT 

actually identify this as a gaining reach during regulated high 

flows. 

During the July 16 – 17, 2001, seepage study, there were 

no streamflow losses in the Portneuf River Valley reach 

associated with pumped surface-water diversions because 

irrigators participated in a power buyback program, except 

between Chesterfield Dam and measurement station 1SP. During the May 29, 2002, seepage study, a 13.3-ft3

/s streamflow 

loss from pumped surface-water diversions was measured 

between Chesterfield Dam and station 6SPT (Steve Luke, 

Idaho Department of Water Resources, written commun., 

2002). The length of the losing river reach was nearly 3 times 

longer during July 16 – 17, 2001, in the middle of the irrigation 

season, than on May 29, 2002, early in the irrigation season 

(fig. 15). The seepage run on May 29, 2002, several days 

after the beginning of regulated high flows and the start of 

the irrigation season, showed that surface water was seeping 

through the riverbed in the losing reach between stations 6SPT 

and 7SPT at a rate of 4.3 ft3/s (table 2). This loss is less than 

the ±5-percent accuracy for streamflow measurements; thus, 

the reach between 5SP and 6SPT is reported as a neutral reach 

(fig. 13). Integrated analysis of streamflow and manometer 

measurements at instream piezometers report a losing reach 

between 5SP and 6SPT (fig. 15.) The loss from surface water 

seeping through the riverbed was much larger at the end of the 

regulated high flows, about 19 ft3/s during July 16 – 17, 2001, 

between stations 3SPT and 7SPT. 

Manometer measurements at instream piezometers in the 

Portneuf River Valley reach indicate streamflow depletion. 

Manometer measurements at station 6SPT, near the center of 

the losing reach, showed a continually negative hydraulic head 

between the surface-water stages and ground-water levels during 2001– 02. At this station, surface water infiltrating through 

the riverbed probably is common. Infiltration is dependent on 

the hydraulic head and on the riverbed hydraulic conductivity. Manometer measurements at station 6SPT showed that 

the hydraulic head was –100 mm (– 4 in.) during May 2002 

early in the irrigation season and – 325 mm (–14.6 in.) during 

July 2001 later in the irrigation season. These hydraulic head 

declines show that ground-water levels were declining relative 

to the surface-water stage and that additional surface water 

was being induced to flow through the riverbed and into the 

aquifer. These ground-water-level declines and the resulting 

streamflow losses probably result from withdrawal of ground 

water by irrigation wells. These negative hydraulic heads could 

not be produced by increases in surface-water diversions.

Seepage studies indicated a possibility of large 

streamflow losses from surface water seeping through the 

riverbed in the Pebble-Topaz reach between stations 10S and 

11S. The 283-ft3/s loss in streamflow between these stations 

on May 29, 2002, may be a result of the hydroelectric project 

located between these stations. Flow data for this hydroelectric project during the seepage run was not available to the 

USGS; therefore, any withdrawal or release of water by this 

hydroelectric project could not be quantified. Because of this 

data gap, the surface- and ground-water relations between stations 10S and 11S could not be quantified. 

Conclusions about streamflow conveyance losses in the 

Portneuf River Valley reach and the Pebble-Topaz reach resulting from infiltration during regulated high-flow conditions in 

the irrigation season are based on two seepage runs. Conveyance losses in the Portneuf River Valley reach (about 19 ft3

/s) 

were greatest during the mid-summer regulated high flows. 

Conveyance losses in the Pebble-Topaz reach were about 283 

ft3/s during the spring regulated high flows. The percentage 

of this loss that is associated with the nearby hydroelectric 

project is not known. Although these measurements provide a rough estimate of the magnitude of conveyance losses 

resulting from infiltration, additional seepage studies, along 

with monitoring of streamflow diversions and ground-water 

pumping, are needed to quantify streamflow depletion more 

accurately. These additional data also can help quantify 

streamflow depletion associated with (1) diversion of surface 

water for irrigation and (2) pumping irrigation wells that lower 

the water table and induce surface-water seepage through the 

riverbed. Ground-water-flow modeling would provide a more 

thorough evaluation of the effects of ground-water withdrawals on streamflow depletion.

Temporal Changes in Ground-Water 

Levels in the Portneuf Valley

Hydrologic Conditions 

Drought conditions prevailed along the Portneuf River 

before and during this study. Hydrologic conditions are based 

on (1) records of local maximum water-equivalent snowpack 

measurements from 1945, (2) records of discrete water-level 

measurements for well 07S 39E 10CCD1 dating from 1968 

(fig. 6), and (3) daily precipitation data measured at the 

Pocatello regional airport. The maximum water-equivalent 

snowpack data based on April snowpack measurements were 

obtained from the Natural Resources Conservation Service 

(NRCS) station at Pebble Creek, located about 1,000 ft 

above the floor of the Portneuf Valley (fig. 3). The average 

annual maximum water-equivalent snowpack for the period 

1945– 2002 was 15.0 in. and ranged from 3.2 in. in 1992 to 

27.3 in. in 1952. For the sake of brevity, the average annual 

maximum water-equivalent snowpack hereafter is referred to 

as annual snowpack.

The annual minimum water level in well 07S-39E10CCD1 (period of record 1968 to present) declined steeply 

during drought conditions in 1987– 93 and 1998 – 2002 (fig. 

6). During March 1, 1987, to May 15, 1993, ground-water 

levels declined at a rate of 2.7 ft per year; concomitantly, 

the annual snowpack at the Pebble Creek station was 6.3 in. 

below average. By 1997, the annual minimum ground-water 
30 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

T.

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R. 38 E.

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Nonpumping well—Number is water-level fluctuation, in feet. Well

 identification number provided in figure 2

Nonpumping well/pumping well—Numbers are water-level fluctuation,

 in feet. Well identification number provided in figure 2

Water levels have been monitored since 1968—Monitored on at least a

 quarterly basis, sometimes on a weekly basis. Annual water-level

 fluctuations frequently exceeded 20 feet

Dry during eight site visits in 2001-02—Contained water during 1968

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Figure 21. Annual fluctuations in ground-water levels in the Portneuf Valley, Idaho, July 2001 through July 2002.
Temporal Changes in Ground-Water Levels in the Portneuf Valley 31

T.

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Figure 22. Long-term fluctuations in ground-water levels in the Portneuf Valley, Idaho, September and October 1968 and 2001.
32 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

levels had recovered to their pre-1987 levels. This recovery 

also is reflected in increases in the annual snowpack. Between 

December 31, 1998, and July 25, 2002, ground-water levels 

declined at a rate of 3.4 ft per year; concomitantly, annual 

snowpack was 2.9 in. below average. At the end of the 

1999 – 2001 period, the annual snowpack reached a minimum 

of 8.6 in. below average. Between July 25, 2001, and the final 

measurement for this study on July 26, 2002, ground-water 

levels appeared to have stopped declining, at least for this 

1-year period, and were stable, perhaps owing, in part, to the 

2002 snowpack, which was only 2.6 in. below average. 

During this study, water levels in monitoring well 07S 

39E 10CCD1 (fig. 6) were at their lowest since the 1987– 93 

drought. However, the rate of ground-water-level declines during the 1998 – 2002 drought was about 125 percent the rate of 

declines during the previous drought. Such an increase in rate 

of ground-water-level declines is the result of decreased precipitation and increased ground-water withdrawals. The annual 

snowpack in the mountains that border the Portneuf Valley has 

declined significantly; the 1945– 85 annual snowpack was 16.1 

in., whereas the 1986 to present annual snowpack was 11.6 

in. Extended dry climatic conditions since 1987 are partially 

responsible for the 1998 – 2002 water-level declines. These 

declines also are attributed partially to increases in groundwater withdrawals since 1950 (fig. 7). Since the 1990s, there 

have been several years when the Chesterfield Reservoir has 

not completely refilled, and the water in storage behind the 

reservoir has been depleted by the middle of the irrigation 

season. In this situation, surface-water diversions for irrigation were terminated before the end of the irrigation season, 

and irrigators, who were relying in part on diversions from the 

Portneuf River, had to rely solely on ground water for an alternate supply. Although there are no water-use records, there is 

strong evidence that, in the dry 1990s, ground-water withdrawals increased and impacted ground-water levels. During the 

remainder of the irrigation season, flows from the reservoir 

were reduced to natural streamflow, which typically ranges 

from 1 to 4 ft3/s (Steve Hebdon, District Watermaster for the 

Portneuf River Marsh Valley Canal, oral commun., 2002).

Annual Fluctuations, 2001– 02

Annual ground-water-level fluctuations in the Portneuf 

Valley were based on measurements made about every 2 

months during July 2001 through July 2002 in 32 wells composing the Portneuf Valley monitoring network (fig. 2). Waterlevel fluctuations in these wells ranged from 1.6 to 19.7 ft; the 

median fluctuation was 3.6 ft. Pumping water levels also were 

measured in 9 of the wells. Water-level fluctuations in these 

wells ranged from 3.4 to 54.6 ft; the median was 25.4 ft (fig. 

21). Water levels rose during the fall and spring and declined 

during the summer. Wells with large annual water-level fluctuations appeared to be uniformly distributed throughout the 

Portneuf Valley. Wells with large water-level fluctuations and 

large declines can be the result of aquifer stress, poor aquifer 

water-yielding characteristics in some locations, proximity to 

flow-limiting boundaries, or poor well construction.

Long-Term Fluctuations, 1968 – 2001

Long-term fluctuations in ground-water levels in the 

Portneuf Valley were evaluated on the basis of measurements 

made during September and October 1968 and 2001 in 32 

wells composing the monitoring network. September and 

October were selected for characterizing long-term fluctuations because declines associated with irrigation reach a maximum at the end of the irrigation season. Water levels declined 

in 30 of the 32 wells during the 34-year period 1968 – 2001; 

the median decline was 3.4 ft (fig. 22). The maximum decline 

was 11.0 ft in well 07S 39E 10ACB. This declining trend is 

concomitant with a long-term decrease in annual snowpack 

as measured at the NRCS Pebble Creek station. Water levels 

declined in all wells except 07S 38E 11ACC1 and 06S 39E 

29CDA1; water levels in these wells rose 10.8 and 2.5 ft, 

respectively.

The 2001– 02 median annual water-level fluctuation of 

3.6 ft in wells in the Portneuf Valley monitoring network is 

nearly equal to the median long-term fluctuation of 3.4 ft in 

water levels over the past 34 years. Hence, annual water-level 

fluctuations conceivably could mask long-term fluctuations. 

However, the consistent water-level decline over the 34-year 

period suggests that the long-term declines are real. In addition, the discrete water-level measurements in well 07S 39E 

10CCD1 indicate a long-term decline with intervening periods 

of higher water levels.

Long-term fluctuations in ground-water levels in the 

Portneuf Valley were investigated in relation to the history of 

ground-water withdrawal rights since 1900. Long-term water 

levels in well 07S 39E 10CCD1 declined substantially after 

1986 and remained low through 1995 (fig. 6). Between 1968 

and 1980, water rights for ground-water withdrawals nearly 

doubled from 23,500 to 46,000 acre-ft per year (fig. 7). However, during this period, ground-water levels were relatively 

constant and did not exhibit a declining trend (fig. 6) that 

could be related to the increased ground-water rights. During 

1987– 96, when the permitted amount of withdrawals for all 

ground-water rights combined remained constant, the median 

ground-water level was about 9 ft lower than during 1968 – 82. 

This decline in ground-water levels during a period of no 

increase in ground-water withdrawal rights could be accounted 

for by declining snowpack or by increased pumping from irrigation wells to help crops during the drier climatic conditions. 

If ground-water withdrawals increased during this dry period, 

this increase may have contributed to water-level declines. 

Summary and Conclusions

The State of Idaho and local water users are concerned 

that streamflow depletion in the Portneuf River in Caribou 
Summary and Conclusions 33

and Bannock Counties is linked to ground-water withdrawals 

for irrigated agriculture. A year-long field study that focused 

on surface- and ground-water relations was conducted, in 

cooperation with the Idaho Department of Water Resources, 

to begin addressing some of the water-user concerns. The 

study area comprised a 30.2-mile reach of the Portneuf River 

downstream from the Chesterfield Reservoir. During the field 

study, the surface- and ground-water relations were dynamic. 

A losing reach was delineated in the middle of the Portneuf 

River Valley reach about 5.5 miles downstream from the Chesterfield Reservoir. Seepage studies indicated the possibility 

of large streamflow losses from surface water seeping through 

the riverbed in the Pebble-Topaz reach about 19 to 24.2 miles 

downstream from the Chesterfield Reservoir. However, 

streamflow data for the hydroelectric project in this reach were 

not available to the U.S. Geological Survey (USGS); because 

of this data gap, streamflow losses could not be quantified.

Thermistor arrays set up in four instream piezometers 

traced the movement of heat through the riverbed of the 

Portneuf River. These data provided continuous information 

about surface- and ground-water relations in a gaining reach 

and a losing reach. Broadening the use of heat as a tracer to 

monitor surface- and ground-water relations on the Portneuf 

River would greatly enhance the understanding of the evolution—timing, location, and magnitude—of losing and gaining 

reaches during the irrigation season. Instream piezometers 

with thermistor arrays are relatively inexpensive, require little 

maintenance, and continuously monitor conditions.

Manometer measurements of hydraulic head at instream 

piezometers in the losing reach in the Portneuf River Valley 

reach showed that the ground-water levels were as much as 

393 millimeters (15.5 inches) below the surface-water stages, 

which indicated that surface water was infiltrating down 

through the riverbed of the Portneuf River. Manometer measurements in the gaining reach showed that the ground-water 

levels were 18 to 190 millimeters (0.7 to 7.5 inches) above the 

surface-water stages, which indicated that ground water was 

seeping up into the river. Installing instream piezometers in 

the Pebble-Topaz reach and measuring hydraulic heads, temperature, and specific conductance would improve the understanding of surface- and ground-water relations in this reach.

A regional perspective on surface- and ground-water relations in the Portneuf Valley was obtained from analysis of specific conductance and temperature in the Portneuf River Valley 

reach. Specific conductance and temperature data showed 

that ground water was seeping into the river just downstream 

from the Chesterfield Reservoir and where the valley narrows 

upstream from Pebble. Specific conductance was about two 

times higher and temperature was several degrees cooler in 

ground water than in the river in the gaining reach. The more 

dilute and warmer surface water infiltrated the riverbed in the 

losing reach in the middle of the study area. Infiltration of 

relatively dilute surface water through the riverbed lowered the 

specific conductance of the ground water so that surface- and 

ground-water specific conductance were nearly equivalent. 

Infiltration of the warm surface water through the riverbed also 

increased ground-water temperatures to the extent that surfaceand ground-water temperatures were nearly equivalent. Stratification of water quality across the Portneuf River was another 

indicator of ground water seeping into the river.

Seepage studies indicated that streamflow losses from 

surface water seeping through the riverbed in the losing reach 

of the Portneuf River Valley reach ranged from 4.3 to 20

cubic feet per second (ft3/s) during the period of regulated 

high flows. During the July 16 – 17, 2001, seepage studies, 

no streamflow losses in the Portneuf River Valley reach were 

associated with pumped surface-water diversions because 

irrigators participated in a power buyback program, except 

between Chesterfield Dam and measurement station 1SP. During the May 29, 2002, seepage study, streamflow losses from 

pumped surface-water diversions between Chesterfield Dam 

and measurement station 6SPT were 13.3 ft3/s. The length of 

the losing river reach was nearly 3 times longer during July 

16 – 17, 2001, in the middle of the irrigation season, than on 

May 29, 2002, early in the irrigation season. A seepage run 

conducted on May 29, 2002, several days after the beginning 

of regulated high flows and the start of the irrigation season, 

showed that surface water was seeping through the riverbed at 

a rate of 4.3 ft3/s. The loss from surface water seeping through 

the riverbed was much larger at the end of the regulated high 

flows, about 19 ft3/s during July 16 – 17, 2001. Even though 

apparent losses from surface water seeping through the riverbed were measured between Chesterfield Dam and station 

2SPT during regulated high flows, these losses were attributed 

to inaccurate diversion data or inaccurate flow data for the 

dam.

Seepage studies indicated that streamflow losses along 

the Pebble-Topaz reach occurred between measurement stations 10S and 11S. During the May 30, 2002, regulated high 

flows, the streamflow losses were about 283 ft3/s, compared 

with 57 and 20 ft3/s during the September 18 and October 

17, 2001, regulated low flows. During the September 18 and 

October 17, 2001, seepage runs, no streamflow was being 

diverted for irrigation. During the September, October, and 

May seepage runs, most of the streamflow losses between 

stations 10S and 11S were offset by gains of 55.9, 16.7, and 

226 ft3/s farther downstream between stations 11S and 13S. 

A hydroelectric project located between stations 10S and 11S 

stores water behind a cement impoundment structure. As 

much as 300 ft3/s of water can be diverted from this project 

and returned to the river farther downstream between stations 

11S and 12S. Flow data for this hydroelectric project during 

the seepage run were not available to the USGS; therefore, any 

withdrawal or release of water by this hydroelectric project 

could not be quantified. Because of this data gap, the surfaceand ground-water relations between stations 10S and 12S 

could not be quantified. 

Long-term fluctuations in ground-water levels in the 

Portneuf Valley were evaluated by comparing measurements 

during September and October 1968 and 2001 in 32 wells 

composing the monitoring network. During this 34-year 

period, water levels declined in all but two wells. The median 
34 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

water-level decline in 30 of the 32 wells was 3.4 feet. This 

temporal trend is concomitant with a long-term decrease in 

average annual snowpack. Long-term ground-water-level 

declines could not be related to a long-term increase in 

ground-water withdrawal rights. However, water-use data, 

rather than ground-water withdrawal rights, would provide a 

more accurate analysis of long-term trends in ground-waterlevel declines as they relate to ground-water withdrawals. A 

historical perspective of ground-water usage in the Portneuf 

Valley could be established by developing a relation between 

power consumption and irrigation well pumping rates, obtaining historical power consumption data for the various irrigators, and then using this information to compute historical 

water usage. This method of computing water usage also 

could be done on a yearly basis.

References Cited 

Barton, G.J., 2002, Dissolved cadmium, zinc, and lead loads 

from ground-water seepage into the South Fork Coeur 

d’Alene River system, northern Idaho, 1999: U.S. Geological Survey Water-Resources Investigations Report 01– 4274, 

130 p.

Constantz, J., and Stonestrom, D.A., 2003, Heat as a tracer 

of water movement near streams, in Stonestrom, D.A., ed., 

Heat as a tool for studying the movement of ground water 

near streams: U.S. Geological Survey Circular 1260, 

p. 1– 6. 

Fenneman, N.M., 1931, Physiography of western United 

States: New York, McGraw-Hill Book Co., 534 p.

Lewis, H.G., and Peterson, P.P., 1921, Soils survey of the Portneuf area, Idaho: U.S. Department of Agriculture, Report on 

Bureau of Soils, 52 p., 2 pl.

Norvitch, R.F., and Larson, A.L., 1970, A reconnaissance 

of the water resources in the Portneuf River Basin, Idaho: 

Idaho Department of Reclamation Water Information 

Bulletin no. 16, 58 p.

Rantz, S.E., and others, 1982, Measurement and computation 

of streamflow, Volume 1, Measurement of stage and discharge: U.S. Geological Survey Water-Supply Paper 2175, 

284 p.

U.S. Department of Agriculture, 1993, Upper Portneuf River 

channel State Agricultural Water-Quality Program Project, final planning report and environmental assessment, 

Caribou County, Idaho: Natural Resources Conservation 

Service report, [variously paged].

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

1998, Ground water and surface water, a single resource: 

U.S. Geological Survey Circular 1139, 79 p.

Winter, T.C., LaBaugh, J.W., and Rosenberry, D.O., 1983, 

Direct measurement of differences in hydraulic head 

between ground water and surface water using a hydraulic 

potentiomanometer: Limnology and Oceanography, v. 33, 

no. 5, p. 1209–1214.
APPENDIX 1. Water levels in selectd wells in the 

Portneuf Valley, Idaho, 1968–69 and 2001–02
36 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

[This page intentionally left blank]
Appendix 1 37

WATER LEVEL, IN FEET BELOW LAND SURFACE

MONTH

Well 6S-39E-29CDA1

Well 6S-39E-33CAC1

Well 6S-39E-33DDB1

Well 6S-39E-34BBB1

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2001–02 water level

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Water levels in selected wells in the Portneuf Valley, Idaho, 1968 – 69 and 2001 – 02.
38 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02 WATER LEVEL, IN FEET BELOW LAND SURFACE

MONTH

Well 7S-38E-11ACC1

Well 7S-38E-13DDB1

Well 7S-38E-24BDD2

Well 7S-38E-25ABB1

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2001–02 water level

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Water levels in selected wells in the Portneuf Valley, Idaho, 1968 – 69 and 2001 – 02.
Appendix 1 39

WATER LEVEL, IN FEET BELOW LAND SURFACE

MONTH

Well 7S-38E-25ABB2

Well 7S-38E-25DAC1

Well 7S-38E-26ADD1

Well 7S-38E-26DDD1

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Water levels in selected wells in the Portneuf Valley, Idaho, 1968 – 69 and 2001 – 02.
40 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02 WATER LEVEL, IN FEET BELOW LAND SURFACE

MONTH

Well 7S-38E-27ADC1

Well 7S-39E-3DCC1

Well 7S-39E-7DCD1

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Dry Dry

Well 7S-38E-35BAD1

Water levels in selected wells in the Portneuf Valley, Idaho, 1968 – 69 and 2001 – 02.
Appendix 1 41

WATER LEVEL, IN FEET BELOW LAND SURFACE

MONTH

Well 7S-39E-10ABB1

Well 7S-39E-10ACB1

Well 7S-39E-12DCC1

Well 7S-39E-13DBA1

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Water levels in selected wells in the Portneuf Valley, Idaho, 1968 – 69 and 2001 – 02.
42 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02 WATER LEVEL, IN FEET BELOW LAND SURFACE

MONTH

Well 7S-39E-13DDB1

Well 7S-39E-14DBC1

Well 7S-39E-16BBC1

Well 7S-39E-17ADA1

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Water levels in selected wells in the Portneuf Valley, Idaho, 1968 – 69 and 2001 – 02.
Appendix 1 43

WATER LEVEL, IN FEET BELOW LAND SURFACE

MONTH

Well 7S-39E-20BAA1

Well 7S-39E-20BDD1

Well 7S-39E-24ADD1

Well 7S-39E-30AAB1

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Water levels in selected wells in the Portneuf Valley, Idaho, 1968 – 69 and 2001 – 02.
44 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02 WATER LEVEL, IN FEET BELOW LAND SURFACE

MONTH

YEAR

Well 8S-39E-6DCB1

Well 7S-39E-9DCC1

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2001–02 water level

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Measurement

Pumping

No measurements during this time

Water levels in selected wells in the Portneuf Valley, Idaho, 1968 – 69 and 2001 – 02.
APPENDIX 2. Continuous record of surface- and groundwater temperatures at measurement stations on the 

Portneuf River, Idaho, August 2001 through January 2002
46 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

[This page intentionally left blank]
Appendix 2 47

TEMPERATURE, IN DEGREES CELSIUS

2001

MEASUREMENT STATION 2SPT

2002

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Surface-water temperature

Ground-water temperature at 20 inches

 below riverbed

Ground-water temperature at 40 inches

 below riverbed

Gates closed on dam at Chesterfield

 Reservoir on July 22, 2001, and did

 not open until May 2002. The river

 channel at site 2SPT was nearly dry

 during this period

Continuous record of surface- and ground-water temperatures at measurement station 2SPT, Portneuf River, Idaho, during 

August 2001 through January 2002.
48 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02 TEMPERATURE, IN DEGREES CELSIUS

2001

MEASUREMENT STATION 3SPT

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Surface-water temperature at measure-

 ment station 2SPT

Ground-water temperature at 20 inches

 below riverbed

Ground-water temperature at 40 inches

 below riverbed

Gates closed on dam at Chesterfield

 Reservoir on July 22, 2001, and did

 not open until May 2002. The river

 channel at site 3SPT was nearly dry

 during this period

Continuous record of surface- and ground-water temperatures at measurement station 3SPT, Portneuf River, Idaho, during 

August 2001 through October 3, 2001. (Surface-water temperature at measurement station 2SPT is used because the surface-water thermistor failed at measurement station 3SPT)
Appendix 2 49

TEMPERATURE, IN DEGREES CELSIUS

2001

MEASUREMENT STATION 6SPT

2002

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Surface-water temperature

Ground-water temperature at 40 inches

 below riverbed

Gates closed on dam at Chesterfield

 Reservoir on July 22, 2001, and did

 not open until May 2002. The river

 channel at site 6SPT was nearly dry

 during this period

Continuous record of surface- and ground-water temperatures at measurement station 6SPT, Portneuf River, Idaho, during 

August 2001 through January 2002.
50 Surface- and Ground-Water Relations, Portneuf River, Idaho, 2001– 02

Continuous record of surface- and ground-water temperatures at measurement station 7SPT, Portneuf River, Idaho, during 

August 2001 through January 2002. (Surface-water temperature at measurement station 6SPT is used because the surfacewater thermistor failed at measurement station 7SPT) TEMPERATURE, IN DEGREES CELSIUS

2001

MEASUREMENT STATION 7SPT

2002

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Surface-water temperature at measure-

 ment station 6SPT

Ground-water temperature at 20 inches

 below riverbed

Gates closed on dam at Chesterfield

 Reservoir on July 22, 2001, and did

 not open until May 2002. The river

 channel at site 7SPT was nearly dry

 during this period
Manuscript approved for publication, August 27, 2004.

Prepared by U.S. Geological Survey Publishing staff, Idaho District, 

Boise, Idaho:

Launa H. Allen

Linda Buckmaster

Richard L. Helton

Barbara N. Kemp

For more information concerning the research in this report, contact

Idaho District Chief

U.S. Geological Survey

230 Collins Road

Boise, Idaho 83702-4520

http://id.water.usgs.gov

Released online, November 2004.
Valley, Caribou and Bannock Counties, Idaho, 2001–02—Scientific Investigations Report 2004–5178

Barton, G.J.—Surface- and Ground-Water Relations on the Portneuf River, and Temporal Changes in Ground-Water Levels in the Portneuf