Prepared in cooperation with the Bureau of Indian Affairs and the

Washington State Department of Ecology

Hydrogeologic Framework, Groundwater and Surface-Water 

Systems, Land Use, Pumpage, and Water Budget of the 

Chamokane Creek Basin, Stevens County, Washington

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2010–5165
Cover: Photograph of Chamokane Falls. (Photograph taken by Sue Kahle, U.S. 

Geological Survey, June 26, 2008.)
Hydrogeologic Framework, Groundwater and 

Surface-Water Systems, Land Use, Pumpage, and 

Water Budget of the Chamokane Creek Basin, 

Stevens County, Washington

By Sue C. Kahle, William A. Taylor, Sonja Lin, Steven S. Sumioka, and 

Theresa D. Olsen

Prepared in cooperation with the Bureau of Indian Affairs and the 

Washington State Department of Ecology

Scientific Investigations Report 2010–5165

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Kahle, S.C., Taylor, W.A., Lin, Sonja, Sumioka, S.S., and Olsen, T.D., 2010, Hydrogeologic framework, groundwater 

and surface-water systems, land use, pumpage, and water budget of the Chamokane Creek basin, Stevens County, 

Washington: U.S. Geological Survey Scientific Investigations Report 2010-5165, 60 p.
iii

Contents

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

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

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

Description of Study Area ...................................................................................................................4

Previous Investigations.................................................................................................................................4

Methods of Investigation..............................................................................................................................6

Well Data................................................................................................................................................6

Geology.................................................................................................................................................11

Hydrogeology.......................................................................................................................................11

Meteorological Data...........................................................................................................................11

Geology and Geologic Setting ...................................................................................................................11

Hydrogeologic Framework.........................................................................................................................16

Hydrogeologic Units...........................................................................................................................21

Horizontal Hydraulic Conductivity....................................................................................................22

Yield and Specific Capacity...............................................................................................................23

Occurrence and Movement of Groundwater..........................................................................................24

Recharge..............................................................................................................................................24

Groundwater Flow Directions...........................................................................................................24

Groundwater Discharge ...................................................................................................................27

Seasonal Variations in Groundwater Levels ..................................................................................27

Surface-Water System ...............................................................................................................................29

Historical Streamflow.........................................................................................................................29

Springs..................................................................................................................................................29

Streamflow Gains and Losses .........................................................................................................31

Interactions Between Groundwaterand Surface Water......................................................................36

Land Use and Land Cover Change Analysis............................................................................................36

Groundwater Pumpage and Use...............................................................................................................39

Basin Water Budget....................................................................................................................................43

Data Needs ...................................................................................................................................................43

Summary........................................................................................................................................................44

Acknowledgments.......................................................................................................................................45

References Cited..........................................................................................................................................45

Appendix A. Land Use and Land Cover Change Analysis...................................................................49
iv

Plates

[In pocket]

Plate 1. Map showing location of project wells, streamflow measurement sites, and 

AgriMet station and graphs showing water-level altitudes in selected 

wells, precipitation measured at the AgriMet station, and discharge from 

streamflow-gaging station 12433200, Chamokane Creek basin, Stevens County 

Washington

Plate 2. Geologic map and cross sections showing hydrogeologic units in the Chamokane 

Creek basin, Stevens County, Washington

Figures

Figure 1. Map showing location of the Chamokane Creek basin, Stevens County, 

Washington ................................................................................. 3

Figure 2. Map showing average annual (1971–2000) precipitation in the Chamokane 

Creek basin study area, Stevens County, Washington ................................. 5

Figure 3. Map showing physiographic regions of Washington ................................. 12

Figure 4. Map showing extent of glacial ice and glacial lakes in northern Washington, 

Idaho, and parts of Montana ............................................................... 15

Figure 5. Lithologic and hydrologic characteristics of the hydrogeologic units in the 

Chamokane Creek basin, Stevens County, Washington .............................. 17

Figure 6. Map showing surficial extent of the hydrogeologic units in the Chamokane 

Creek basin, Stevens County, Washington ............................................. 18

Figure 7. Map showing thickness and areal extent of the Upper outwash aquifer in 

the Chamokane Creek basin, Stevens County, Washington ........................... 19

Figure 8. Map showing thickness and areal extent of the Valley confining unit in the 

Chamokane Creek basin, Stevens County, Washington .............................. 20

Figure 9. Map showing areal extent, water-level altitudes, and inferred directions of 

groundwater flow in the Upper outwash aquifer in the Chamokane Creek 

basin, Stevens County, Washington ...................................................... 25

Figure 10. Map showing areal extent, water-level altitudes, and inferred directions 

of groundwater flow in the Lower aquifer in the Chamokane Creek basin, 

Stevens County, Washington............................................................... 26

Figure 11. Graph showing long-term groundwater-level altitudes in Chamokane 

Creek basin and precipitation for Wellpinit, Washington station ..................... 28

Figure 12. Graph showing mean daily discharge for the period of record (1972–2009) 

for U.S. Geological Survey streamflow-gaging station 12433200, Chamokane 

Creek below Falls near Long Lake, Stevens County, Washington ..................... 30

Figure 13. Maps showing generalized land use and land cover classifications, 

Chamokane Creek basin, Stevens County, Washington, 1987 and 2009............... 38

Figure 14. Map showing distribution of Census blocks and 2000 population, 

Chamokane Creek basin, Stevens County, Washington .............................. 41

Figure 15. Map showing distribution of estimated pumpage in 2000 for self-supplied 

domestic use and public supply, Chamokane Creek basin, Stevens County, 

Washington ................................................................................. 42
v

Conversion Factors, Datums, Abbreviations and Acronyms, 

and Well- and Spring-Numbering System

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

square mile (mi2) 2.590 square kilometer (km2)

Volume

gallon (gal) 3.785 liter (L)

gallon (gal) 0.003785 cubic meter (m3)

million gallons (Mgal) 3,785 cubic meter (m3)

cubic mile (mi3) 4.168 cubic kilometer (km3)

Flow rate

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

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

cubic foot per day (ft3/d) 0.02832 cubic meter per day (m3/d)

gallon per minute (gal/min) 0.06309 liter per second (L/s)

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

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

Tables

Table 1. Selected physical and hydrologic data for the project wells in the Chamokane

Creek basin, Stevens County, Washington ............................................. 7

Table 2. Geologic timescale with simplified geologic units of the Chamokane Creek 

basin study area, Stevens County, Washington.......................................... 13

Table 3. Summary of yield and specific capacity for hydrogeologic units in the 

Chamokane Creek basin, Stevens County, Washington .............................. 23

Table 4. Annual peak discharge for U.S. Geological Survey streamflow-gaging station 

12433200, Chamokane Creek below Falls near Long Lake, Stevens County, 

Washington ................................................................................. 29

Table 5. Seepage investigation, Chamokane Creek, Spokane River basin, Stevens 

County, Washington, September 18–October 11, 2007 ................................. 32

Table 6. High-flow investigation, Chamokane Creek, Spokane River basin, Stevens 

County, Washington, April 14–17, 2008 ................................................... 33

Table 7. Seepage investigation, Chamokane Creek, Spokane River basin, Stevens

County, Washington, August 25–September 2, 2008 .................................... 35

Table 8. Annual groundwater pumpage for Chamokane Creek basin, Stevens 

County, Washington ........................................................................ 40
vi

Multiply By To obtain

Length

meter (m) 3.281 foot (ft) 

Area

square meter (m2) 0.0002471 acre 

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

°F=(1.8×°C)+32

*Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times 

foot of aquifer thickness [(ft3/d)/ft2]ft. In this report, the mathematically reduced form, foot 

squared per day (ft2/d), is used for convenience.

Datums

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

(NAVD 88).

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

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

Conversion Factors, Datums, Abbreviations and Acronyms and 

Well- and Spring-Numbering System—Continued

Inch/Pound to SI—Continued

Multiply By To obtain

million gallons per year (Mgal/yr) 3,785 cubic meter per year (m3/yr)

Specific capacity

gallon per minute per foot [(gal/min)/ft] 0.2070 liter per second per meter [(L/s)/m]

Hydraulic conductivity

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

Hydraulic gradient

foot per mile (ft/mi) 0.1894 meter per kilometer

Transmissivity*

square foot per day (ft2/d) 0.09290 square meter per day (m2/d)

SI to Inch/Pound
vii

Abbreviations and Acronyms

ANUDEM Australian National University Digital Elevation Model

BIA Bureau of Indian Affairs

BR Bedrock unit

BT Basalt unit

DEM digital elevation model

EROS Earth Resources Observation and Science Center

ET evapotranspiration

GIS Geographic Information System

LA Lower aquifer

LU Landslide unit

LULC land use and land cover

Mb Miocene basalts

MSS multispectral scanner

NOAA National Oceanic and Atmospheric Administration

NED National Elevation Dataset

NWIS National Water Information System

TM thematic mapper

UA Upper outwash aquifer

USDA U.S. Department of Agriculture

USGS U.S. Geological Survey

VC Valley confining unit
viii

Well- and Spring-Numbering System

In Washington, wells and springs are assigned numbers that identify their location in a 

township, range, section, and 40-acre tract. For example, well number 29N/40E-23M06 indicates 

that the well is in township 29 north of the Willamette Base Line, and range 40 east of the 

Willamette Meridian. The numbers immediately following the hyphen indicate the section (23) 

in the township, and the letter following the section (M) gives the 40-acre tract of the section. 

The two-digit sequence number (06) following the letter indicates that the well was the sixth 

one inventoried by project personnel in that 40-acre tract. A "D" following the sequence number 

indicates that the well has been deepened. An “S” following the sequence number indicates 

that the site is a spring. In the illustrations of this report, wells and springs are identified 

individually using only the section and 40-acre tract, such as 23M06. The townships and ranges 

are shown on the map borders.

Willamette Meridian

W A S H I N G T O N

Study area

SECTION 23

TOWNSHIP

Well 29N/40E-23M06

D C B A

E F G H

M L K J

N P Q R

R. 40 E.

T.

29

6 5 4 3 2 1

7 12

13

19 24

25

31 32 33 34 35 36

N. 30

18

Willamette Base Line

Diagram showing well numbering system in Washington
Hydrogeologic Framework, Groundwater and SurfaceWater Systems, Land Use, Pumpage, and Water Budget of 

the Chamokane Creek Basin, Stevens County, Washington

By Sue C. Kahle, William A. Taylor, Sonja Lin, Steven S. Sumioka, and Theresa D. Olsen

Abstract

A study of the water resources of the unconsolidated 

groundwater system of the Chamokane Creek basin was 

conducted to determine the hydrogeologic framework, 

interactions of shallow and deep parts of the groundwater 

system with each other and the surface-water system, 

changes in land use and land cover, and water-use estimates. 

Chamokane Creek basin is a 179 mi2 area that borders and 

partially overlaps the Spokane Indian Reservation in southern 

Stevens County in northeastern Washington State. Aquifers 

within the Chamokane Creek basin are part of a sequence of 

glaciofluvial and glaciolacustrine sediment that may reach 

total thicknesses of about 600 ft. In 1979, most of the water 

rights in the Chamokane Creek basin were adjudicated by 

the United States District Court requiring regulation in favor 

of the Spokane Tribe of Indians’ senior water right. The 

Spokane Tribe, the State of Washington, and the United States 

are concerned about the effects of additional groundwater 

development within the basin on Chamokane Creek. 

Information provided by this study will be used to evaluate the 

effects of potential increases in groundwater withdrawals on 

groundwater and surface-water resources within the basin.

The hydrogeologic framework consists of six 

hydrogeologic units: The Upper outwash aquifer, the 

Landslide Unit, the Valley Confining Unit, the Lower Aquifer, 

the Basalt Unit, and the Bedrock Unit. The Upper outwash 

aquifer occurs along the valley floors of the study area and 

consists of sand, gravel, cobbles, boulders, with minor silt and 

(or) clay interbeds in places. The Lower aquifer is a confined 

aquifer consisting of sand and gravel that occurs at depth 

below the Valley confining unit. Median horizontal hydraulic 

conductivity values for the Upper outwash aquifer, Valley 

confining unit, Lower aquifer, and Basalt unit were estimated 

to be 540, 10, 19, and 3.7 ft/d, respectively.

Many low-flow stream discharge measurements at 

sites on Chamokane Creek and its tributaries were at or near 

zero flow. The most notable exception is where Chamokane 

Creek is supported by discharge of large springs from the 

Upper outwash aquifer in the southern part of the basin. 

Most high-flow measurements indicated gains in streamflow 

(groundwater discharging to the stream). Large streamflow 

losses, however, were recorded near the north end of Walkers 

Prairie where streamflow directly recharges the Upper outwash 

aquifer. The similarity in seasonal water-level fluctuations in 

the Upper outwash aquifer and the Lower aquifer indicate that 

these systems may be fairly well connected.

Land use and land cover change analysis indicates that 

Chamokane Creek basin has been dominated by forests with 

some pasture and agricultural lands with sparse residential 

development from the 1980s to present. Loss in forest cover 

represents the largest change in land cover in the basin 

between 1987 and 2009. This appears to be mostly due to 

forestry activities, especially in the northern part of the basin. 

Since 1987, more than 18,000 acres of evergreen forest have 

been logged and are at various stages of regrowth.

Estimated average annual total groundwater pumpage 

in the basin increased from 224 million gallons per year 

(Mgal/yr) in 1980 to 1,330 Mgal/yr in 2007. The largest 

withdrawals during 2007 were to supply two fish hatcheries, 

with a combined total annual pumpage of about 1,150 Mgal. 

Annual groundwater pumpage values from 1980 through 2007 

for the study area ranged from 21.1 to 28.9 Mgal/yr for 

domestic wells and 0.38 to 23.7 Mgal/yr for public supply. An 

approximate water budget for a typical year in the Chamokane 

Creek basin indicates that 19.6 in. of precipitation are 

balanced by 4.7 in. of streamflow discharge from the basin, 

and 14.9 in. of evapotranspiration.

Introduction

Chamokane Creek basin is a 179 mi2 area that borders 

and partially overlaps the Spokane Indian Reservation in 

southern Stevens County in northeastern Washington State 

(fig. 1). It is a roughly boot-shaped, northwest-to-southtrending basin about 28 mi long and 7 mi wide. Chamokane 

Creek flows toward the east through the Camas Valley to 

near the town of Springdale, Washington, where the creek 

turns southeast and then flows generally south through the 

Chamokane Valley and Walkers Prairie toward the town of 
2 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

Ford, Washington. Mean September streamflow in Chamokane 

Creek at Chamokane Falls, as recorded at U.S. Geological 

Survey (USGS) streamflow-gaging station 12433200 (fig. 1), 

for 1971–2008 was 27 ft3/s. Aquifers in the Chamokane 

Creek basin are part of a sequence of glaciofluvial and 

glaciolacustrine sediment that may reach total thicknesses 

of about 600 ft. Most wells within the basin are completed 

in an upper unconfined aquifer or in a confined aquifer that 

occurs at depth beneath the Camas and Chamokane Valleys. 

The two aquifers are separated by a silt and clay unit that can 

be more than 300 ft thick and appears laterally continuous. 

Basalt or bedrock, consisting mostly of granite and (or) 

meta-sedimentary rocks, underlies the sediment at generally 

unknown depths.

In 1979, most of the water rights in the Chamokane 

Creek basin were adjudicated by the United States District 

Court. Since the 1979 adjudication, the District Court has 

issued various amendments and orders that affect water users 

in the basin. The Chamokane Creek Adjudication requires 

that junior water right holders on Chamokane Creek, and its 

tributaries, be regulated in favor of the more senior water right 

of the Spokane Tribe. This senior water right was granted 

as a reserved water right for irrigation and protection of the 

Spokane Tribe’s Ancestral Fishing Rights in Chamokane 

Creek. A court-appointed Water Master regulates junior 

water rights when the mean daily 7-day low flow becomes 

less than 24 ft3/s (27 ft3/s for rights issued after December 

1988) at Chamokane Falls, as recorded at U.S. Geological 

Survey (USGS) streamflow-gaging station 12433200 (fig. 1). 

Regulation has been necessary in 3 recent years (2001, 2005, 

and 2008). The non-Reservation areas of the basin are closed 

to any additional groundwater or surface-water appropriation, 

with the exception of “permit exempt” uses of groundwater. 

These exempt uses in Washington State do not require a water 

right and include stock watering, lawn or non-commercial 

garden watering, single or group domestic uses of as much as 

5,000 gal/d, and small-scale industrial use not to exceed 5,000 

gal/d (Washington State Department of Ecology, 2006). 

The 1979 District Court Judgment contends that 

groundwater withdrawals in the Upper Chamokane region 

had no effect on the flow of Chamokane Creek because 

groundwater in the upper region was considered to be part 

of a separate aquifer from that in the Chamokane Valley. 

Despite the ruling, there are concerns about the effects of 

future groundwater development that may occur in the 

upstream end of the basin, particularly outside the reservation 

boundary. The relation between the upper (Camas Valley 

and Chamokane Creek headwaters) and lower (Chamokane 

Valley) Chamokane Creek basin groundwater systems has 

not been directly studied. With increasing population and 

residential development, permit exempt groundwater use is 

expected to continue and the potential effects of this growth on 

Chamokane Creek are unknown.

Finally, although the upper aquifer within the Chamokane 

Valley has been fairly well characterized (Wozniewicz, 1989), 

the hydrogeologic framework of the entire basin, as well as the 

nature and extent of the lower aquifer, is poorly understood. 

An assessment of the hydrogeologic framework of the entire 

basin was needed prior to an assessment of the effects of 

groundwater use on the surface-water system.

To evaluate these concerns and uncertainties, the USGS 

began a study in 2007 with the primary goals of describing 

the groundwater and surface-water system of the valley-fill 

deposits of the basin and assessing the effects of potential 

increases in groundwater withdrawals on groundwater and 

surface-water resources. The study includes an evaluation of 

the 1979 judgment contending that groundwater withdrawals 

in the upper Chamokane Creek basin do not affect Chamokane 

Creek. 

This report describes the results from Phase 1 of a 

two‐part study. The objectives of Phase 1 were to characterize 

the hydrogeologic setting and groundwater and surface‐water 

interactions within the basin, and to obtain selected hydrologic 

data sets to support construction and calibration of a coupled 

groundwater and surface-water flow model in Phase 2. Phase 1 

data collection efforts were focused on the area within and 

adjacent to the drainage basin boundary shown in figure 1 .

Phase 2 is currently (2010) ongoing and will build on 

the findings of Phase 1. Regional model boundaries will 

be described in Phase 2 including rationale for where the 

model boundaries differ from the drainage basin boundary. 

The objectives of Phase 2 are to build and apply a coupled 

groundwater and surface-water flow model using GSFLOW 

(Markstrom and others, 2008) to evaluate the possible regional 

effects of different groundwater-use scenarios on the surfacewater system. The GSFLOW model also will be used to 

provide an estimate of recharge and a comprehensive water 

budget for the groundwater system. Additionally, the model 

will be used to further describe groundwater and surface-water 

interactions in the basin. Specific study objectives include:

Phase 1

1. Characterize the hydrogeologic framework of the 

Chamokane Creek basin;

2. Describe the groundwater and surface-water flow 

system within the basin; and

3. Estimate water use within the basin at the time of 

adjudication (1979) and present for permit exempt 

and non-exempt uses of groundwater and surface 

water. 

Phase 2

1. Evaluate the contention that groundwater 

withdrawals in the Upper Chamokane region have 

no affect on flow in Chamokane Creek; and

2. Evaluate hydrologic system responses to various 

stresses using a coupled groundwater and surfacewater flow model.
Introduction 3

watac10-0434_fig 01

S p o k ane In dian R e s er va t io n

118°15' 118° 117°45'

48°10'48°47°50'

0 5 15 MILES 100 10 5 15 KILOMETERS

MILL

CANYON

SNOOK CANYON

TAMARACK CANYON

Falls Creek

Coyote Creek

eJ r er d

er C ek

Wilmont

Creek

Nez Perce Creek

Sixmile Creek

Welsh Creek

Harvey

Creek

F. N k.

Hunters Creek

Alder Creek

N. Fk. Chamokane Creek

Sw amp Cr.

S. Fk. Chamokane

Creek

Middle

Fork

B ul

e Creek

Sand

Creek

Little

Chamokane

Creek

e W l pl ni it Creek

Spring Creek

mahC

nako e

keer C

Deer Creek

No. Fk. Deer Creek

Indian Creek

Hawk Creek

Columbia

revi R

Co

ul mb ai

revi R

nar F l k ni . D ooR

es

velt Lake

Spokane River STEVENS

FERRY

LINCOLN SPOKANE

COUNTY

COUNTY

COUNTY COUNTY

Wellpinit Ford

Springdale

WALKERS 

PRAIRIE

ICE BOX

CANYON

HUCKLEBERRY MOUNTAINS

oC

vl il R el revi

OC LVIL EL

Y ELL AV

Grouse

Creek

Spokane River

CH MA O AK

LL AV E N

YE

USGS gaging

station 12433200

Figure location

WASHINGTON

EXPLANATION

Spokane Indian Reservation

Drainage basin boundary

Base from U.S. Geological Survey digital data, 1983, 1:100,000Universal Transverse Mercator projection, Zone 11Horizontal Datum: North American Datum of 1983 (NAD 83)

VALLEY CAMAS

Figure 1. Location of the Chamokane Creek basin, Stevens County, Washington.
4 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

Purpose and Scope 

This report presents the results of the Phase 1 study 

of the groundwater and surface-water systems in the 

Chamokane Creek basin. It describes the hydrogeologic 

framework of the basin, including the extent and thickness 

of significant hydrogeologic units, discusses groundwater 

interactions between hydrogeologic units and with the 

surface-water system, describes land- and water-use types, 

and discusses additional data needs. The scope of the report 

includes a description of the regional and local geologic 

history, the surficial geology of the basin, the physical 

characteristics of the hydrogeologic units, and groundwater 

levels and generalized flow directions. Also described are 

the characteristics of the streamflow network, a description 

of land-use types and changes over time, summaries of 

groundwater withdrawals within the basin, and an approximate 

water budget for the basin.

Description of Study Area

Chamokane Creek has its headwaters in the Huckleberry 

Mountains that attain elevations of about 4,600 ft. The creek 

flows east from its headwaters into Camas Valley, a southwestnortheast oriented valley about 6.5 mi long (fig. 1). From 

Camas Valley, Chamokane Creek flows through Ice Box 

Canyon and then southeast about 4 mi where it is slightly 

entrenched in a system of outwash terraces. The creek 

continues southeast to a bedrock outcrop where it changes 

course and flows southwest into Walkers Prairie where flows 

are intermittent. On the southern end of Walkers Prairie, a 

series of large springs discharge from an east-west oriented 

bluff west of Ford (pl. 1). Discharge from these springs and 

outflow from two hatcheries provides most of the perennial 

flow in Chamokane Creek from near Ford to the confluence 

with the Spokane River. Chamokane Falls is about 1.5 mi 

upstream of the confluence where Chamokane Creek flows 

over a bedrock outcrop (pl. 1).

A low elevation drainage divide near Springdale, 

Washington, between the north-flowing Colville River and 

the south-flowing Chamokane Creek is underlain by glacial 

outwash and till associated with the Colville sublobe of the 

Cordilleran ice sheet and, at greater depths, by thick clay 

and silt deposited in large Pleistocene lakes (Kahle and 

others, 2003). These unconsolidated deposits form a shallow 

surface-drainage divide in an otherwise broad and continuous 

Colville‐Chamokane Valley. A pre-glacial Columbia River 

may have flowed southward through the present-day Colville 

and Chamokane Valley, resulting in the long and wide valley 

that is visible today (Willis, 1887; Carrara and others, 1996).

Most mountainous areas in the basin are covered with 

pine, fir, and larch forests that are the basis for the historical 

and current (2009) lumber industry in the area. In the lowland 

areas of the basin, agricultural land use is widespread, 

including grazing and hay production, along with scattered 

developed areas, including the town of Ford, Washington. 

About 34 mi2 of the Spokane Indian Reservation lies within 

Chamokane Creek basin with Chamokane Creek’s east bank 

forming the eastern border of the Reservation from just north 

of 48 degrees latitude to the confluence of Chamokane Creek 

and the Spokane River (fig. 1). Two fish hatcheries, one 

operated by the State and one by the Spokane Tribe, are on 

the north side of Chamokane Creek west of Ford (pl. 1). An 

inactive uranium ore processing site, owned by Dawn Mining 

Company, is on 820 acres south of Ford (pl. 1). Ore was 

processed at the site from 1956 to 1982; cleanup at the site 

continues with oversight provided by the Washington State 

Department of Health (http://www.doh.wa.gov/ehp/rp/waste/

dmchm.htm, accessed January 5, 2010). 

The climate in the study area varies from subhumid to 

semiarid and is characterized by warm, dry summers and 

cool, moist winters (Molenaar, 1988). The mean annual 

(1923–2007) precipitation value for the nearest long-term 

weather station in Wellpinit, Wash. is 18.95 in. (http://www.

wrcc.dri.edu/cgi-bin/cliMAIN.pl?wa9058, accessed January 6, 

2010). Historically, most precipitation falls as snow during 

the 5-month period from November through March. Average 

annual precipitation for 1971–2000 varies from a minimum 

of about 14 in. at the southern edge to more than 25 in. in 

the northernmost headwaters of the basin (Western Regional 

Climate Center, 2010) (fig. 2).

Previous Investigations

Previous investigations that have contributed to the 

understanding of the water resources in the Chamokane 

Creek basin generally fall in one of three categories. The 

first category includes small-scale investigations of the 

groundwater resources in all or part of the lower Chamokane 

Valley, the second includes multi-basin studies relating to 

the water resources of the entire Spokane Indian Reservation 

(Reservation), and the third includes basin-wide studies 

focused on the surface-water system of Chamokane Creek and 

its tributaries. 

Detailed analysis of the upper aquifer within the 

Chamokane Valley is described by Buchanan and others 

(1988) and by Wozniewicz (1989). Numerous small-scale 

hydrogeologic and water-quality studies related to the closure 

of Dawn Mining Company’s millsite are summarized by 

Washington Department of Health (1991). A geophysical 

seismic reflection survey was conducted to estimate the 

thickness of aquifer material near Ford by King and others 

(1996).
Previous Investigations 5

Figure 2. Average annual (1971–2000) precipitation in the Chamokane Creek basin study area, Stevens County, Washington.

watac10-0434_fig 02

EXPLANATION

Average annual

 precipitation, in inches

6 to 14

14.1 to 16

16.1 to 18

18.1 to 20

20.1 to 22

22.1 to 25

25.1 to 30

Drainage basin

 boundary

48°

47°

50'

118° 117°45'

Washington Average Annual Precipitation, 1971- 2000

PRISM model, NRCS Water and Climate Center,

Oregon State University

UTM10 projection, NAD83, 800 meter resolution

T.

30

N.

T.

29

N.

T.

28

N.

T.

27

N.

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

0 5 10 MILES

0 5 10 KILOMETERS

N. Fk. Chamokane Creek

S. Fk. Chamokane Creek

Middle Fork

Sand Creek

Ch

a

m

okane

Creek

Spokane

River

N. Fk. Chamokane Creek

S. Fk. Chamokane Creek

Middle Fork

Sand Creek

Ch

a

m

okane

Creek

Ford

Springdale

WALKERS 

PRAIRIE

HUCKLEBERRY MOUNTAINS

Spokane

River

CHAMOKANE

VALLEY

CAMAS VALLEY

Colville

R.
6 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

Water resources of parts of the Spokane Indian 

Reservation are described in several documents. Lukas 

(1981) conducted a hydrogeologic study and described 

groundwater potential for domestic supply on the Reservation. 

Aquifer systems of the Reservation are described in Matt and 

Buchanan (1993a) and hydrology and geomorphology are 

described in Matt and Buchanan (1993b). These topics also are 

described in their entirety by Matt (1994). Peone and others 

(1993) produced an inventory of surface and groundwater 

resources on the Reservation including identification of 

factors that may affect water quality. Embry and others (1997) 

described the hydrogeologic units and groundwater quality of 

the eastern Reservation area including part of Walkers Prairie. 

The Chamokane Creek Watershed Management Planning 

project addresses the improvement, maintenance, and 

protection of surface-water quality in the basin. The Watershed 

Management Plan (Kessler, 2000a) was developed to be used 

as a tool to guide local efforts to protect and (or) improve 

the surface-water quality on and off the Reservation. Kessler 

(2000b) reported surface-water quality and quantity measured 

in the basin from November 1997 through April 1999. In the 

Chamokane Creek Watershed Needs Assessment, Kessler 

(2008) described causes and sources of pollution, alternate 

management practices, and a water-quality monitoring plan.

Methods of Investigation

Collecting the basic data required to characterize the 

hydrogeologic framework and analyze the direction of 

groundwater movement in the Chamokane Creek basin 

involved a field inventory of wells, measurement of water 

levels in wells, and construction of hydrogeologic sections, 

hydrogeologic unit maps, and water-level maps. Methods used 

to collect and interpret these hydrogeologic data are presented 

in this section. Methods used to describe the land use and land 

change characterization and the water use of the study area are 

presented with those respective sections later in this report.

Well Data

Between September and November 2007, 102 wells 

throughout the study area were field located to acquire 

lithologic data and to measure the depth to water in wells. 

Criteria for site selection included availability of a driller’s 

report and lithologic information (obtained from well records 

at the USGS Washington Water Science Center and the 

Washington Department of Ecology), location and depth of 

the well, and the ease of access to the well. The intent was 

to collect data from wells evenly distributed throughout 

the unconsolidated deposits of the study area, including the 

Camas and Chamokane Valley floors and tributary valleys. 

This was not possible in all areas, however, because of lack 

of development in much of the basin or lack of permission to 

access some wells. 

An additional 41 wells, field-located during previous 

USGS projects (Embrey and others, 1997; Kahle and others, 

2003) were added to the Chamokane project data set to aid in 

describing the hydrogeologic framework of the study area. To 

further augment the project data set, 15 non-field-located wells 

were assigned approximate locations (latitude and longitude 

coordinates) using public land survey locations (township, 

range, section, and quarter-quarter section), well addresses, 

and (or) parcel number for each well included on drillers’ 

logs. To the extent possible, paper maps (USGS 7 1⁄2-minute 

quadrangles and City or County road maps) and on-line 

maps (Stevens County Assessor, 2010; National Geographic 

TOPO!, 2007; and GoogleTMEarth, 2010) were used to verify 

drillers’ locations and to estimate latitude and longitude for the 

15 non‐field-located wells. Locations of all 158 project wells 

are shown on plate 1, and selected physical and hydrologic 

data for the wells are provided in table 1.

Information gathered at field-located wells included site 

location and well-construction details. Depth to water (water 

level) was measured in most wells using a calibrated electric 

tape or graduated steel tape, both with accuracy to 0.01 ft. In 

some cases, water levels were not measured because a well 

was difficult to access. Two inventoried wells, 28N/39E24K01 and 29N/39E-02J01, were observed as flowing, 

meaning the water level was above the land surface elevation. 

Latitude and longitude were obtained for field-located wells 

using a Global Positioning System (GPS) receiver with a 

horizontal accuracy of one-tenth of a second (about 10 ft). 

Land-surface altitude for each project well was obtained from 

a digital elevation model with 10-m square cells using the 

latitude and longitude for each well. 

In addition to the water levels measured during the 

inventory phase of this study, synoptic water levels were 

measured in most of the field-inventoried wells during two 

2-week periods, March 24–April 1, 2008, and August 25–

September 4, 2008. Water levels also were measured 

monthly in a network of 25 wells during March 2008 

through December 2009. Due to unusually heavy snow and 

inaccessibility of well heads, water-level measurements were 

not made in December 2008 and January 2009. Six wells in 

the monthly network also were instrumented with transducers 

for recording hourly water-level measurements from May 

2008 through April 2010. 

All water-level measurements were made by USGS 

personnel according to standardized techniques of the USGS 

(Drost, 2005). Information for all project wells was entered 

into the USGS National Water Information System (NWIS) 

database. Graphs of water-level altitude for selected wells are 

shown on plate 1. 
Methods of Investigation 7

Table 1. Selected physical and hydrologic data for the project wells in the Chamokane Creek basin, Stevens 

County, Washington. 

[Site No.: See well- and spring-numbering system diagram for explanation of well- and spring-numbering system. Depth of hole: na, not 

applicable. Land-surface altitude: Referenced to the North American Vertical Datum of 1988 (NAVD 88). Latitude and longitude: In 

degrees, minutes, seconds referenced to the North American Datum of 1983 (NAD 83). Location: F, field located; N, not field located. 

Hydrogeologic unit of open interval: UA, Upper outwash aquifer; LU, Landslide unit; VC, Valley confining unit; LA, Lower aquifer; 

BT, Basalt unit; BR, Bedrock unit; other, unconsolidated deposits along the Spokane River. Network: M, manual monthly water-level 

measurements; T, transducer hourly water-level measurements; –, not part of network]

Site No.

Depth of hole

(feet below 

land surface)

Landsurface 

altitude

(feet)

Latitude Longitude Location

Hydrogeologic 

unit of open 

interval

Network

27N/39E-01E01 544 1,732 475216 1175021 N BR –

27N/39E-10L01 150 1,442 475106 1175245 F other –

27N/39E-11L01 361 1,549 475115 1175125 N other –

27N/39E-15A01 157 1,398 475045 1175156 N other –

27N/40E-18F01 340 1,742 475033 1174840 N other –

28N/39E-02Q01 278 2,424 475703 1175115 F BT –

28N/39E-02Q02 unknown 2,425 475702 1175114 F BT –

28N/39E-12R01 96 1,838 475610 1174939 F LU –

28N/39E-13B02 103 1,814 475552 1174945 F LU –

28N/39E-13B03 100 1,814 475555 1174941 F LU –

28N/39E-13C01 99 1,809 475547 1174960 F LU –

28N/39E-19R03 380 1,841 475416 1175559 F BR –

28N/39E-20P01 89 1,826 475420 1175523 F LU –

28N/39E-22Q01 100 1,822 475426 1175220 F LU –

28N/39E-22R02 565 1,784 475428 1175203 F LU,BT –

28N/39E-23E01 262 1,819 475446 1175154 F LU,BT –

28N/39E-23J01 160 1,683 475437 1175037 F LA M

28N/39E-23M01 218 1,804 475432 1175137 F VC M

28N/39E-23P01 247 1,691 475426 1175124 F LA –

28N/39E-23P02 255 1,697 475425 1175126 F LA –

28N/39E-24C02 326 1,790 475503 1175014 F LA –

28N/39E-24F01 358 1,762 475451 1174959 F LA –

28N/39E-24G03D1 280 1,746 475450 1174944 F VC –

28N/39E-24G04 380 1,727 475446 1174945 F LA –

28N/39E-24K01 256 1,685 475433 1174945 F VC –

28N/39E-24R01 75 1,764 475421 1174932 F VC –

28N/39E-26E01 350 1,759 475350 1175151 F LA M

28N/39E-26G01 115 1,619 475353 1175102 F VC –

28N/39E-27H01 359 1,760 475350 1175157 F LA –

28N/39E-27H02 220 1,760 475350 1175156 F LA –

28N/39E-27H03 385 1,761 475351 1175157 F LA –

28N/39E-27J01 327 1,749 475338 1175158 F LA –

28N/39E-27Q01 220 1,744 475324 1175216 F LA –

28N/39E-28A01 340 1,857 475405 1175326 F VC,BR –

28N/39E-28D01 320 1,837 475409 1175429 F VC –

28N/39E-29D01 178 1,831 475410 1175543 F BR –

28N/39E-34A01 280 1,744 475322 1175159 F LA –

28N/39E-34B01 187 1,734 475320 1175219 F LA –

28N/39E-34B02 180 1,736 475322 1175222 F LA –

28N/39E-35L01 131 1,719 475257 1175119 F LA –

28N/39E-35R01 400 1,721 475240 1175046 N BR –
8 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

Site No.

Depth of hole

(feet below 

land surface)

Landsurface 

altitude

(feet)

Latitude Longitude Location

Hydrogeologic 

unit of open 

interval

Network

28N/39E-36D01 303 1,855 475313 1175017 N BR –

28N/39E-36D02 302 1,852 475317 1175022 N BT –

28N/40E-03M01 60 1,855 475708 1174517 F UA M

28N/40E-05A01 80 1,834 475737 1174703 F UA M

28N/40E-05A02 261 1,833 475741 1174647 F LA M

28N/40E-05A03 320 1,833 475741 1174647 F BR –

28N/40E-05H01 40 1,833 475730 1174656 F UA –

28N/40E-05Q01 60 1,836 475657 1174713 F UA –

28N/40E-06R01 283 1,864 475656 1174811 F LA M

28N/40E-07N02 115 1,815 475602 1174919 F UA –

28N/40E-08H02 43 1,820 475629 1174649 F UA T

28N/40E-08K01 80 1,824 475624 1174704 F UA –

28N/40E-09A01 89 1,865 475648 1174532 F UA –

28N/40E-09A02 140 1,835 475646 1174540 F BR –

28N/40E-11H02 120 2,118 475636 1174304 F BR M

28N/40E-17C01 380 1,817 475558 1174734 F LA T

28N/40E-17F01 121 1,810 475539 1174723 F LA –

28N/40E-17F02 155 1,810 475539 1174724 F LA –

28N/40E-17J01 20 1,793 475525 1174655 F UA T

28N/40E-17K01 47 1,793 475532 1174719 F UA T

28N/40E-17L01 41 1,807 475533 1174727 F UA –

28N/40E-18Q01 440 1,796 475514 1174838 F LA –

28N/40E-18Q02 58 1,777 475510 1174840 F UA –

28N/40E-18Q03 58 1,787 475512 1174837 F UA –

28N/40E-18Q04 22 1,776 475510 1174840 F UA T

28N/40E-19D01 42 1,774 475508 1174906 F UA –

28N/40E-19E01S na 1,725 475444 1174920 F UA –

28N/40E-19J02 158 1,779 475437 1174819 F BT –

28N/40E-30D01 367 1,767 475406 1174914 F LA M

28N/40E-30D02 120 1,775 475415 1174900 F BR –

28N/40E-30D03 200 1,766 475408 1174912 F LA –

28N/40E-31D01 264 1,874 475316 1174914 F VC –

29N/38E-02R01R1 100 2,536 480205 1175817 F BR –

29N/38E-11A01 120 2,531 480153 1175819 F BR –

29N/38E-36M01 100 2,504 475804 1175825 F BT –

29N/39E-01C01 52 2,156 480254 1175019 F UA,VC –

29N/39E-02J01 258 2,151 480223 1175058 F LA –

29N/39E-02R01 14 2,156 480209 1175056 F UA M

29N/39E-03J01 40 2,185 480230 1175203 F BT –

29N/39E-03J02 210 2,177 480227 1175203 F BR –

Table 1. Selected physical and hydrologic data for the project wells in the Chamokane Creek basin, Stevens 

County, Washington.—Continued

[Site No.: See well- and spring-numbering system diagram for explanation of well- and spring-numbering system. Depth of hole: na, not 

applicable. Land-surface altitude: Referenced to the North American Vertical Datum of 1988 (NAVD 88). Latitude and longitude: In 

degrees, minutes, seconds referenced to the North American Datum of 1983 (NAD 83). Location: F, field located; N, not field located. 

Hydrogeologic unit of open interval: UA, Upper outwash aquifer; LU, Landslide unit; VC, Valley confining unit; LA, Lower aquifer; 

BT, Basalt unit; BR, Bedrock unit; other, unconsolidated deposits along the Spokane River. Network: M, manual monthly water-level 

measurements; T, transducer hourly water-level measurements; –, not part of network]
Methods of Investigation 9

Table 1. Selected physical and hydrologic data for the project wells in the Chamokane Creek basin, Stevens 

County, Washington.—Continued

[Site No.: See well- and spring-numbering system diagram for explanation of well- and spring-numbering system. Depth of hole: na, not 

applicable. Land-surface altitude: Referenced to the North American Vertical Datum of 1988 (NAVD 88). Latitude and longitude: In 

degrees, minutes, seconds referenced to the North American Datum of 1983 (NAD 83). Location: F, field located; N, not field located. 

Hydrogeologic unit of open interval: UA, Upper outwash aquifer; LU, Landslide unit; VC, Valley confining unit; LA, Lower aquifer; 

BT, Basalt unit; BR, Bedrock unit; other, unconsolidated deposits along the Spokane River. Network: M, manual monthly water-level 

measurements; T, transducer hourly water-level measurements; –, not part of network]

Site No.

Depth of hole

(feet below 

land surface)

Landsurface 

altitude

(feet)

Latitude Longitude Location

Hydrogeologic 

unit of open 

interval

Network

29N/39E-10G01 100 2,177 480145 1175226 F BR –

29N/39E-16F01 200 2,184 480058 1175356 F VC M

29N/40E-03C02 242 2,090 480252 1174450 F VC –

29N/40E-04C01 300 2,170 480255 1174623 N BT –

29N/40E-04K02 138 2,044 480219 1174554 F UA –

29N/40E-04K03 100 2,034 480227 1174555 F UA –

29N/40E-05A02 108 2,147 480254 1174653 F BT –

29N/40E-05P01 500 2,526 480207 1174730 F BT,BR –

29N/40E-05P02 500 2,544 480209 1174727 F BT –

29N/40E-06C01 324 2,137 480254 1174904 N UA –

29N/40E-06D01 358 2,143 480254 1174920 F LA M

29N/40E-09G01 65 1,971 480150 1174554 F UA –

29N/40E-09G02 336 1,971 480138 1174548 F LA –

29N/40E-09G03 73 1,968 480143 1174552 F UA M

29N/40E-09G04 165 1,970 480148 1174553 F VC –

29N/40E-09L01 400 2,008 480125 1174609 N BR –

29N/40E-10D01 100 1,993 480154 1174508 F UA –

29N/40E-10F01R1 240 1,974 480143 1174458 F UA –

29N/40E-10K01 41 1,958 480136 1174445 F UA –

29N/40E-10L01 58 1,952 480136 1174455 F UA –

29N/40E-12E01 147 2,035 480147 1174251 F BR –

29N/40E-14D01 280 2,006 480101 1174356 F UA –

29N/40E-15J02 60 1,915 480035 1174423 F UA –

29N/40E-15J03 105 1,912 480035 1174425 F UA –

29N/40E-15K02 340 1,927 480036 1174442 N UA –

29N/40E-15Q02 460 1,942 480019 1174429 F LA M

29N/40E-15R02 120 1,899 480028 1174416 F UA M

29N/40E-22E01 163 1,934 480004 1174514 F BT –

29N/40E-22J02 60 1,878 475943 1174427 F UA M

29N/40E-22P01 110 1,867 475937 1174502 F LU M

29N/40E-22Q01 61 1,868 475937 1174445 F UA –

29N/40E-23C01 69 1,886 480012 1174335 F UA –

29N/40E-23M02 96 1,891 475950 1174407 F UA –

29N/40E-23M03 80 1,888 475948 1174407 F UA –

29N/40E-23M04 80 1,888 475949 1174411 F UA –

29N/40E-23M05 140 1,888 475948 1174407 F UA –

29N/40E-23M06 80 1,885 475944 1174351 F UA M

29N/40E-26C02 225 1,948 475914 1174346 F BR –
10 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

Table 1. Selected physical and hydrologic data for the project wells in the Chamokane Creek basin, Stevens 

County, Washington.—Continued

[Site No.: See well- and spring-numbering system diagram for explanation of well- and spring-numbering system. Depth of hole: na, not 

applicable. Land-surface altitude: Referenced to the North American Vertical Datum of 1988 (NAVD 88). Latitude and longitude: In 

degrees, minutes, seconds referenced to the North American Datum of 1983 (NAD 83). Location: F, field located; N, not field located. 

Hydrogeologic unit of open interval: UA, Upper outwash aquifer; LU, Landslide unit; VC, Valley confining unit; LA, Lower aquifer; 

BT, Basalt unit; BR, Bedrock unit; other, unconsolidated deposits along the Spokane River. Network: M, manual monthly water-level 

measurements; T, transducer hourly water-level measurements; –, not part of network]

Site No.

Depth of hole

(feet below 

land surface)

Landsurface 

altitude

(feet)

Latitude Longitude Location

Hydrogeologic 

unit of open 

interval

Network

29N/40E-26C03 150 1,982 475914 1174330 F UA –

29N/40E-26D01 160 1,957 475915 1174405 F UA –

29N/40E-26D02 215 1,955 475918 1174356 F UA –

29N/40E-26E01 150 1,944 475901 1174355 F UA –

29N/40E-28J01 60 1,854 475858 1174536 F LU –

29N/40E-28P01 48 1,855 475836 1174607 N UA T

29N/40E-33C01 80 1,851 475824 1174612 F UA –

29N/40E-33E01 55 1,895 475822 1174637 F LU –

29N/40E-33M01 149 1,845 475760 1174634 F VC –

29N/40E-33M02 53 1,845 475760 1174634 F UA –

29N/40E-33M03 50 1,844 475758 1174634 F UA –

29N/40E-34F02 100 1,893 475812 1174450 F UA –

29N/40E-34H02 140 1,924 475818 1174418 F UA –

29N/40E-34H03 140 1,924 475815 1174421 F UA –

29N/40E-34J01 100 1,915 475807 1174425 F UA –

30N/39E-25Q02 107 2,213 480358 1174946 F UA M

30N/39E-25Q03 200 2,210 480358 1174955 F BT –

30N/39E-29A01 325 2,737 480423 1175430 F BR –

30N/39E-30B01 380 2,487 480430 1175615 F BT –

30N/39E-36L02 500 2,168 480315 1175007 N VC –

30N/40E-21H01 240.5 1,901 480514 1174533 F LA –

30N/40E-28A01D1 240 1,947 480433 1174541 F LA –

30N/40E-30K01D1 520 2,367 480410 1174839 N BR –

30N/40E-31M01 60 2,145 480314 1174911 F VC –

30N/40E-31N01 120 2,142 480301 1174915 F VC –

30N/40E-31P01D1 289 2,197 480309 1174859 N BT –

30N/40E-31Q04 340 2,135 480302 1174811 F BT –

30N/40E-32C01D1 170 2,141 480336 1174733 F BT –

30N/40E-32F01 140 2,183 480326 1174734 F BT –

30N/40E-32F03 121 2,145 480335 1174733 F BT –

30N/40E-32G02 62 2,107 480334 1174719 F UA –

30N/40E-32L01 70 2,210 480319 1174732 F BT –

30N/40E-32P01 75 2,124 480302 1174744 F UA –

30N/40E-33L01 154 2,064 480320 1174615 F UA –

30N/40E-33M01 80 2,077 480312 1174633 F UA –

30N/40E-33N01 360 2,138 480309 1174627 F BR –

30N/40E-33R01R1 190 2,026 480302 1174537 F VC –

30N/40E-33R02 340 1,990 480257 1174534 F VC –

30N/40E-33R03 46 1,982 480306 1174533 F UA –
Geology and Geologic Setting 11

Geology

The geologic map of the study area (pl. 2) was compiled 

and simplified from several sources, including previously 

unpublished surficial geologic mapping of the Ford and Tum 

Tum, Washington 7 1⁄2-minute quadrangles (Dr. Eugene Kiver, 

Eastern Washington University Emeritus, written commun., 

October 2007), the surficial geologic map of the Chewelah 

1:100,000 quadrangle (Carrara and others, 1995), the digital 

geologic map database (1:100,000 scale) for Washington 

(Washington Division of Geology and Earth Resources, 

2005), and detailed streambed mapping between Ford and 

Chamokane Falls (Howard and others, 1989 and Howard, 

1990). In some areas, modifications were made to existing 

maps based on field visits or stratigraphic evidence obtained 

during this investigation, primarily from drillers’ logs for fieldlocated water wells.

Hydrogeology

Lithologic data from the field-inventoried wells were 

entered into the Rockworks 2006® software, a stratigraphic 

analysis package. Sixteen hydrogeologic sections were 

constructed using Rockworks to identify and correlate 

hydrogeologic units, primarily on the basis of grain size 

and stratigraphic position. To avoid redundancy, nine 

representative sections of the original 16 are published in this 

report. Thickness and extent-of-unit maps were manually 

drawn for two units using information from the hydrogeologic 

sections and data from the remaining project wells. 

The altitude of the top and extent of hydrogeologic units 

described in this report were used to create digital elevation 

model (DEM) surfaces with 30 ft square cells in a Geographic 

Information System (GIS) database. These surfaces provide 

the digital framework for the GSFLOW model being 

developed for Phase 2 of this project. The interpolation 

method for creating each hydrogeologic unit surface in GIS 

was based on the Australian National University Digital 

Elevation Model (ANUDEM) procedure developed by 

Hutchinson (1989), using top-of-unit altitudes at wells and 

extent maps. Each hydrogeologic unit surface was constrained 

to the National Elevation Dataset (NED) 30 ft DEM for land 

surface where the unit outcropped.

In developing the digital hydrogeologic framework, the 

original data interpretations were honored as much as possible. 

The interpolated hydrogeologic unit surfaces and thicknesses 

were compared to the original hydrogeologic unit maps, 

hydrogeologic sections, and well interpretations in order to 

make adjustments that more accurately reflect the original 

interpretations. Uncertainties are greatest in areas where 

the surficial geology changes abruptly or gaps exist in the 

lithologic data provided by the project wells.

Meteorological Data

Data from an automated agricultural weather station 

(AgriMet station) installed and operated by the Bureau of 

Reclamation (http://www.usbr.gov/pn/agrimet/) was used to 

estimate evapotranspiration (ET) in the Chamokane Creek 

basin. The AgriMet station was installed in the north-central 

part of the study area in November 2007 and will be operated 

continuously through December 2010. AgriMet uses the 1982 

Kimberly-Penman equation, adapted by the U.S. Department 

of Agriculture (USDA) Agricultural Research Service (Jensen 

and others, 1990), for computing reference ET. This procedure 

requires several meteorological input parameters for modeling 

ET, including maximum and minimum daily air temperatures, 

relative humidity, daily solar radiation, and daily wind run, all 

of which are collected by the AgriMet system (Peter Palmer, 

Bureau of Reclamation, written commun., September 12, 

2006). Data collected by this station are available on-line at 

http://www.usbr.gov/pn/agrimet/agrimetmap/chawda.html.

Geology and Geologic Setting

Chamokane Creek basin is in the eastern part of the 

Okanogan Highlands, a physiographic region east of the 

Columbia River and Franklin D. Roosevelt Lake and north 

of the Columbia Plateau (fig. 3). This area is characterized by 

north-south trending mountain ranges reaching altitudes of 

8,000 ft separated by valleys including the Colville River and 

Chamokane Creek Valleys. The Okanogan Highlands contain 

the oldest sedimentary and metamorphic rocks in Washington 

State (Lasmanis, 1991; table 2). Precambrian metasedimentary 

rocks including argillite, dolomite, gneiss, schist, slate, 

and quartzite extend from British Columbia south to near 

the Spokane River (Stoffel and others, 1991). Precambrian 

metasedimentary rocks are overlain by younger marine 

sedimentary rocks that represent each of the geologic-time 

periods in the Paleozoic Era (table 2) and include quartzite, 

shale, and limestone (Lasmanis, 1991). Cretaceous Period 

and Eocene Epoch granites that intruded the older rocks are 

exposed at land surface throughout the Okanogan Highlands 

including much of the western part of the Spokane Indian 

Reservation. 

During the Miocene Epoch, basalt flows spread northeast 

from the Columbia Plateau mantling much of the pre-existing 

landscape and filling in low-lying areas, including part of 

the area within the Chamokane Creek basin. A basalt capped 

mesa is located on the eastern part of the Spokane Indian 

Reservation extending from near Wellpinit to Lyons Hill and 

forms the western edge of Walkers Prairie (pl. 2). 
12 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington watac10_0434_fig 03

0 50 100 MILES

50 100 KILOMETERS 0

Co

ul m

bia

River

Co

ul m

bia

River

Co

ul mbia River

b mul oC

ai

R vi

er

mul o C

i b a

River

Frank lin D. oo R

eves L tl

ka e

Spokane

River

Blue

Moutains

Olympic

Moutains

Cascades North

Cascades South

Willapa

Hills

Okanogan

Highlands

West Okanogan Highlands

East

Puget

Lowlands

Blue

Moutains

Olympic

Moutains

Columbia Plateau

Cascades North

Cascades South

Portland

Basin

Willapa

Hills

Okanogan

Highlands

West Okanogan Highlands

East

Puget

Lowlands

124° 122° 120° 118°

49°

48°

47°

46°

Chamokane

Creek Basin

Figure 3. Physiographic regions of Washington. (Modified from Lasmanis, 1991.)
Geology and Geologic Setting 13

Geologic Time Simplified geologic unit

Phanerozoic Eon 

(544 mya to present)

Cenozoic Era

(65 mya to present)

Quaternary Period

(1.8 mya to present) 

Holocene Epoch

(8,000 ya to present) Recent non-glacial sediment

Pleistocene Epoch

(1.8 mya to 8,000 ya)

Glacial deposits and 

catastrophic flood deposits

Tertiary Period

(65 to 1.8 mya)

Pliocene Epoch

(5.3 to 1.8 mya) –

Miocene Epoch

(23.8 to 5.3 mya) Basalt and older sediments

Oligocene Epoch

(33.7 to 23.8 mya) –

Eocene Epoch

(55.5 to 33.7 mya)

Intrusive igneous rocks

(granite)

Paleocene Epoch

(65 to 55.5 mya)

Mesozoic Era

(248 to 65 mya)

Cretaceous Period

(145 to 65 mya) 

Jurassic Period

(213 to 145 mya) – Triassic Period

(248 to 213 mya)

Paleozoic Era

(544 to 248 mya)

Permian Period

(286 to 248 mya) 

Marine sedimentary rocks

Carboniferous Period

(360 to 286 mya) 

Devonian Period

(410 to 360 mya)

Silurian Period

(440 to 410 mya)

Ordovician Period

(505 to 440 mya)

Cambrian Period

(544 to 505 mya)

Precambrian Time

(4,500 to 544 mya)

Proterozoic

(2,500 to 544 mya) Metasedimentary rocks

Archean

(3,800 to 2,500 mya) – Hadean

(4,500 to 3,800 mya)

Table 2. Geologic timescale with simplified geologic units of the Chamokane Creek basin study area, Stevens County, Washington.

[Modified from Kahle and Bartolino, 2007. Abbreviations: ya, years ago; mya, million years ago; –, indicates a gap in the geologic record resulting from 

erosion and (or) nondeposition]
14 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

During the Pleistocene Epoch, the study area was 

subjected repeatedly to the erosional and depositional 

processes associated with glacial and interglacial periods 

(Kiver and Stradling, 1982 and Kiver and others, 1989). This 

resulted in an assemblage of unconsolidated sediment that 

overlies much of the bedrock in the study area and is thickest 

along the valley floors. 

At the maximum extent of the most recent Pleistocene 

glaciation (about 15,000 years before present), much of 

northern Washington, Idaho, and westernmost Montana was 

covered by lobes of the Cordilleran ice sheet (fig. 4). The 

large ice sheet formed in the mountains of British Columbia 

and flowed south, filling valleys and overriding low mountain 

ranges in the northern parts of Washington, Idaho, and 

Montana. For thousands of years, the Okanogan, Columbia 

River, and Purcell Trench lobes of the Cordilleran ice sheet 

covered much of northeastern Washington and northern 

Idaho. The Okanogan lobe to the west of the combined 

Colville‐Chamokane Valley was the largest of the lobes 

and covered what is now the northern part of the Waterville 

Plateau. The Okanogan and Columbia River lobes affected 

the study area by blocking westward drainage of the ancestral 

Columbia and Spokane Rivers and creating vast ice-age 

lakes (Waitt and Thorson, 1983). A sublobe of the Columbia 

River lobe moved into the Colville Valley and reached its 

southernmost extent near Springdale, Wash.. Ice thickness in 

the Colville Valley was at least 2,300 ft (Carrara and others, 

1995).

When the Purcell Trench lobe in northern Idaho blocked 

the drainage of the ancestral Clark Fork in northwestern 

Montana, Glacial Lake Missoula was created (fig. 4). Although 

much of the unconsolidated deposits in the study area are 

the result of glacial processes involving the Okanogan and 

Columbia lobes and the Colville sublobe, the Purcell Trench 

lobe, in what is now northern Idaho, also contributed directly 

to sedimentation in the Chamokane Creek basin. Glacial Lake 

Missoula, dammed behind the Purcell Trench lobe (fig. 4), was 

about 600 mi3 in volume and reached a maximum depth of 

2,200 ft (Waitt, 1980). Enormous catastrophic floods occurred 

over a 2,000-year period when the ice dam of the Purcell 

Trench lobe periodically failed, sending floodwaters west 

and southwest. Floodwater crossed parts of Montana, Idaho, 

Washington, and Oregon before reaching the Pacific Ocean 

(fig. 4). The continuous southward flow of ice repeatedly 

blocked the Clark Fork allowing Lake Missoula to refill 

multiple times. The largest of the Missoula floods, many of 

which probably occurred relatively early in the lake-filling 

and flooding cycle, overwhelmed local drainages and topped 

the 2,400-ft divide west of Spokane, spilling south towards 

Cheney and beyond and creating the Channeled Scablands 

(fig. 4). Some of the Missoula floods, following one of the 

more northern floodways, left behind giant current dunes north 

of Loon Lake before exiting westward through the Sheep 

Creek spillway into the Colville Valley near Springdale and 

then southward through the Chamokane Valley (pl. 2; Carrara 

and others, 1995). 

Glacial Lake Columbia, impounded by the Okanogan 

lobe, was the largest glacial lake in the path of the Missoula 

floods (fig. 4). This lake was long-lived (2,000–3,000 years) 

and had a typical surface altitude of 1,640 ft; however, the 

altitude reached 2,350 ft during maximum blockage by 

the Okanogan lobe and rose as high as 2,460 ft during the 

Missoula floods (Atwater, 1986). The higher level of Glacial 

Lake Columbia probably occurred early, whereas the lower 

and more typical level of the lake occurred in later glacial time 

(Richmond and others, 1965; Waitt and Thorson, 1983; and 

Atwater, 1986). At the lower level (1,640 ft), Glacial Lake 

Columbia extended into the Chamokane Valley to near Ford 

and east to the Spokane area, where clayey lake sediment is 

intercalated with Missoula flood sediment. At the higher level 

of Glacial Lake Columbia (2,350 ft), the glacial lake would 

have flooded the entire combined Colville-Chamokane Valley 

nearly reaching the top of the basalt bluffs on the western edge 

of Walkers Prairie (pl. 2). 

As the Colville sublobe advanced southward through 

the Colville Valley, till was deposited beneath the ice and 

fine-grained sediments were deposited as the lobe advanced 

into glacial Lake Columbia (Waitt and Thorson, 1983). The 

southernmost limit of the Colville sublobe is marked by a 

well-developed moraine near the town of Springdale (Carrara 

and others, 1996), where hummocky topography resulted 

from the deposition of material pushed along the ice front 

and from melting of sediment laden ice. This well-developed 

terminal moraine (pl. 2) is referred to as the Springdale 

moraine (Flint, 1936; Carrara and others, 1996). The outflow 

of glacial meltwater draining Camas Valley was pushed 

southward presumably by the front of the ice sublobe and the 

morainal material causing it to incise a narrow channel, Ice 

Box Canyon, (pl. 1) through a northern limb of Lyons Hill 

(McLucas, 1980). 

Along the margins of the sublobe, glacial meltwater 

deposited large areas of outwash sands and gravels. Melt 

water from the Colville sublobe created a large outwash plain 

and series of gravel terraces extending from near Springdale 

to south of Ford. This meltwater deposited vast quantities of 

sediment and reworked early Lake Missoula flood deposits. 

Just beyond the southern limit of the sublobe are former 

glacial meltwater channels now occupied by Swamp Creek 

(fig. 1; pls. 1 and 2). Melt water from the diverted Deer Creek 

drainage contributed to the deposition of a terrace on the 

north wall of Camas Valley including the foot of Craney Hill 

(pl. 2; McLucas, 1980). These coarse-grained deposits overlie 

fine-grained sediment (clay and silt) that are presumed to be 

associated with Glacial Lake Columbia.
Geology and Geologic Setting 15

watac10_0434_fig 04

124°

124°

122°

122°

120°

120°

118°

118° 116°

116°

114°

114°

45°

45°

47°

47°

49°

49°

IDAHO

OREGON

CANADA

UNITED STATES.

MONTANA

Glacial LakeColumbia

GlacialLake Missoula

Columbia

River

Lobe

Colville

Sublobe

Okanogan

Lobe

C O R D I L L E R A N I C E S H E E T

WASHINGTON

Puget

Lobe

BRITISH COLUMBIA

PurcellTrench Lobe

ALBERTA

River

Snake

Columbia

River

Co ul

mb ai

evi R r

R

ai b mul oC iver

Fork

Clark

Pacific Ocean

0 100 150 50 200 KILOMETERS

0 50 100 150 200 MILES

Glacial iceGlacial lakesArea inundated by glacial Lake Missoula floodsExtent of Chamokane Creek basinMajor riversInternational boundaryState boundary

EXPLANATION

ChanneledScablands

Waterville

Plateau

Spokane

Cheney

Ford

Figure 4. Extent of glacial ice and glacial lakes in northern Washington, Idaho, and parts of Montana. (Modified from Allen and Burns, 1986, and Atwater, 1986.)
16 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

The surficial geology of the study area consists of 

10 geologic units that are described below and shown on 

plate 2. 

Alluvial deposits (Qal): This unit includes channel 

and overbank deposits of Chamokane and Swamp Creeks 

and alluvial-fan deposits at the mouths of streams tributary 

to Chamokane Creek. The unit consists mostly of stratified 

silt and sand with some gravel and minor amounts of clay 

deposited by flowing water and generally is from 1 to 30 ft 

thick.

Glacial outburst flood deposits (Qf): This unit includes 

glacial-outburst flood deposits that consist of sand with sparse 

pebbles, cobbles, and boulders deposited by catastrophic 

draining of Glacial Lake Missoula into lower energy 

environments along the margins of the floods. These deposits 

are mapped in the southern part of basin. This unit is as much 

as 100 ft thick within the Chamokane Creek basin.

Glaciofluvial deposits (Qgf): This unit includes mostly 

stratified and well-sorted sand, gravel, and cobble outwash 

deposited by glacial meltwater from the Colville sublobe. 

It also includes outwash deposits along the northern part of 

the Camas Valley and outwash and reworked outburst flood 

deposits along the Chamokane Valley floor and Walkers 

Prairie. Although most of the Qgf is coarse-grained outwash, 

lenses of silt, clay, and till occur locally. The thickness of the 

unit generally is from 20 to 200 ft.

Glacial deposits, undifferentiated (Qgu): This unit 

includes a heterogeneous mixture of silt, sand, gravel, and clay 

that may include loess deposits and older glacial till. The unit 

mantles the upland areas in the west central part of the study 

area and generally is from 5 to 20 ft thick.

Glacial till (Qti): This unit includes mostly unsorted 

and unstratified clay, silt, sand, and gravel deposited by the 

Colville sublobe. Near Springdale, the unit includes the 

terminal moraine of the Colville sublobe. Locally, the unit 

contains stratified sand and gravel and generally, is from 10 to 

80 ft thick. 

Glaciolacustrine deposits (Qla): This unit includes 

mostly clay and silt lake sediments deposited in ice-marginal 

lakes. The unit underlies the Chamokane Creek Valley and is 

overlain by younger deposits within the basin. Just north of the 

Chamokane Creek basin, about 2 mi northeast of Springdale, 

the unit occurs at land surface in the Colville Valley floor. The 

unit includes thin and discontinuous beds of sand and gravel in 

places. Along the axis of the Chamokane Valley, the thickness 

of the unit is commonly about 300 ft.

Loess (Qlo): This unit includes silt and fine sand, and 

minor amounts of clay, deposited by winds. The unit forms 

an extensive blanket on the basalt upland of the Lyons Hill 

area and has a limited extent to the east of Happy Hill in the 

southeast part of the study area. Thickness of the unit typically 

ranges from 1 to 15 ft.

Mass-wasting deposits (Qmw): Includes poorly sorted 

angular rock fragments deposited as talus at the base of steep 

slopes and heterogeneous mixtures of unconsolidated surficial 

material and rock fragments deposited by landslides. The 

largest surface exposures of this unit are along the basalt bluff 

on the western edge of Walkers Prairie and on the west side of 

Happy Hill near Ford. Thickness of the unit varies, but may 

exceed 200 ft in places.

Basalt (Miocene) (Mb): Includes the Grande Ronde 

Basalt of the Columbia River Basalt Group, a dense, dark 

basalt with fine to coarse interbeds. Interbeds may be part of 

the Latah Formation, which was deposited along the margins 

of the basalt flows in eastern Washington. Thickness of the 

unit in the study area is uncertain, but may be more than 

500 ft.

Bedrock (Tertiary to Middle Proterozoic) (Tybr): 

Includes sedimentary, metasedimentary, and intrusive and 

extrusive igneous rocks. Specific rock types include shale, 

conglomerate, dolomite, limestone, argillite, gneiss, schist, 

slate, quartzite, and granite. The unit is exposed in much of 

the high-altitude areas of the basin. The depth to bedrock in 

the Chamokane Creek Valley beneath the unconsolidated 

sediments is largely unknown and likely varies considerably. 

Based on information from wells used in this study, the depth 

to bedrock along most of the central part of the Chamokane 

Creek Valley may be as much as 600 ft. 

Hydrogeologic Framework

The geologic units described previously were grouped 

into six hydrogeologic units based on similar lithologic 

characteristics and large-scale hydrologic properties. The six 

hydrogeologic units described in this report include the Upper 

outwash aquifer, the Landslide unit, the Valley confining 

unit, the Lower aquifer, the Basalt unit, and the Bedrock 

unit. Lithologic and hydrologic characteristics of these units 

are summarized in figure 5. The surficial extent of the units 

is shown in figure 6 and the subsurface extent of the units is 

shown on the hydrogeologic sections (pl. 2) and in figures 7

and 8, for the Upper outwash aquifer and Valley confining 

unit, respectively. Project well locations are shown on plate 1 

and are color coded based on the hydrogeologic unit that the 

wells are open to. Wells that are open to more than one unit 

are shown as black dots on plate 1.
Hydrogeologic Framework 17

Hydrogeologic unit Unit 

label

Range of 

thickness

[estimated 

average 

thickness]

(feet)

Lithologic and hydrologic characteristics

Number 

of project 

wells 

open to 

unit

Upper outwash 

aquifer UA 2 –280

[80]

Unconfined aquifer consisting of gravel, cobbles, boulders, and sand with minor

silt and or clay interbeds. Unit occurs in the Chamokane Valley from Swamp

Creek southward throughout Walkers Prairie. UA occurs in Camas Valley, but is

thinner and less productive. Includes geologic units Qgf, Qf, and Qal. Near

Springdale, UA includes till (Qti), a lower-permeability deposit that includes

compacted and poorly-sorted silt, sand, gravel, and cobbles with lenses of

moderately sorted sand and gravel.

57

Landslide unit LU 0 –205

[150]

Poorly sorted deposits of broken basalt and sedimentary interbeds of the

Columbia River Basalt Group, covered in places by glacial deposits. Unit occurs

along the eastern slopes of the basalt mesa on the eastern uplands of the

Spokane Indian Reservation and on the western flanks of Happy Hill near Ford.

Unit likely is in hydraulic connnection with the UA in Walker’s Prairie. Locally an

aquifer with variable yields. Includes geologic unit Qmw.

9

Valley confining unit VC 4 –480

[170]

Low-permeability unit consisting mostly of glaciolacustrine silt and clay. Unit

occurs at depth throughout the Camas and Chamokane Valleys and is

continuous northward into the Colville Valley. Discontinuous lenses of aquifer

material within the unit contributes usable quantities of water to some wells, 

particularly in the southern part of the basin where Missoula flood deposits are 

interbedded with the glaciolacustrine deposits.

16

Lower aquifer LA 3 –170

Confined aquifer consisting of sand and some gravel. Unit occurs at depth in the

Camas and Chamokane Valleys below the Valley confining unit and is continuous

northward into the Colville Valley. Thickness of unit is not well known.

30

Basalt unit BT 40 –500

Unit is composed of Columbia River Basalt, a dense, dark basalt with generally

fine grained interbeds. Coarse-grained interbeds occur near Springdale. Water

is contained in cracks and fractures and from zones between lava flows. Occurs 

in the eastern uplands of the Spokane Indian Reservation and on Lyons Hill.

Includes geologic unit Mb and thin and discontinuous Qlo and Qgu.

18

Bedrock unit BR Not

applicable

Unit includes argillite, conglomerate, dolomite, gneiss, schist, slate, quartzite,

shale, limestone, and granite. Yields are generally small; numerous abandoned

wells. Includes geologic unit Tybr and thin and discontinuous Qal, Qlo, and Qgf.

19

Figure 5. Lithologic and hydrologic characteristics of the hydrogeologic units in the Chamokane Creek basin, Stevens County, 

Washington.
18 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

watac10-0434_fig 06

EXPLANATION

Surfical extent of hydrogeologic units

 

Drainage basin

 boundary

UA- Upper outwash aquifer

LU- Landslide unit

BT- Basalt

BR- Bedrock

48°

47°

50'

118°

T.

30

N.

T.

29

N.

T.

28

N.

T.

27

N.

117°45'

R. 38 E. R. 39 E. R. 40 E. R. 41 E.

0 5 10 MILES

0 5 10 KILOMETERS

Chamokane

Valley

Camas Valley

Base from U.S. Geological Survey digital data, 1983, 1:100,000

Universal Transverse Mercator projection, Zone 11

Horizontal Datum: North American Datum of 1983 (NAD 83)

Figure 6. Surficial extent of the hydrogeologic units in the Chamokane Creek basin, Stevens County, Washington.
Hydrogeologic Framework 19

watac10-0434_fig 07

EXPLANATION

Thickness and areal extent of

 the Upper outwash aquifer

 

Drainage basin

 boundary

Well used to

 determine unit

 thickness

Less than 50

51 to 100

101 to 150

Greater than 150

118°

T.

30

N.

T.

29

N.

T.

28

N.

T.

27

N.

117°45'

R. 39 E. R. 40 E. R. 41 E.

0 5 10 MILES

0 5 10 KILOMETERS

48°

47°

50'

R. 38 E.

5

Chamokane

Valley

Ahren

Meadow

Craney

Hill

Camas

Valley

Base from U.S. Geological Survey digital data, 1983, 1:100,000

Universal Transverse Mercator projection, Zone 11

Horizontal Datum: North American Datum of 1983 (NAD 83)

Figure 7. Thickness and areal extent of the Upper outwash aquifer in the Chamokane Creek basin, Stevens County, 

Washington.
20 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

watac10-0434_fig 08

EXPLANATION

Thickness and areal extent of

 the Valley confining unit

 

Drainage basin

 boundary

Well used to

 determine unit

 thickness

Less than 150

151 to 300

Greater than 300

48°

47°

50'

118°

T.

30

N.

T.

29

N.

T.

28

N.

T.

27

N.

117°45'

R. 38 E. R. 39 E. R. 40 E. R. 41 E.

0 5 10 MILES

0 5 10 KILOMETERS

Chamokane

Valley

Camas

Valley

Base from U.S. Geological Survey digital data, 1983, 1:100,000

Universal Transverse Mercator projection, Zone 11

Horizontal Datum: North American Datum of 1983 (NAD 83)

Figure 8. Thickness and areal extent of the Valley confining unit in the Chamokane Creek basin, Stevens County, Washington.
Hydrogeologic Framework 21

Hydrogeologic Units

The Upper outwash aquifer (UA) of the Chamokane 

Creek basin is an unconfined aquifer consisting of sand, 

gravel, cobbles, and boulders, with minor silt and (or) 

clay interbeds. Previously described geologic units that 

comprise the bulk of this aquifer include glaciofluvial 

deposits (outwash), glacial outburst flood deposits, and 

alluvial deposits. Near Springdale, the aquifer includes till, 

a lower‐permeability deposit comprised of compacted and 

poorly-sorted silt, sand, gravel, and cobbles with lenses of 

moderately sorted sand and gravel. 

The Upper outwash aquifer occurs along the length of 

the Chamokane and Camas Valleys (fig. 6; pl. 1); 57 project 

wells are completed in this aquifer. Although the Upper 

outwash aquifer exists over much of the valley floors, some 

places within the aquifer are not sufficiently saturated to yield 

sustainable quantities of water to wells. Wells are drilled into 

deeper units in these areas. For example, most wells south 

of Ford are drilled into the Lower aquifer because the Upper 

aquifer in those areas yields insufficient quantities of water.

Thickness of the aquifer ranges from less than 50 ft 

along the margins of the unit to more than 150 ft where glacial 

terraces comprise the unit including the south side of Craney 

Hill and at the mouth of Ahren Meadow (fig. 7; pl. 2, sections 

B–B′ and C–C′). From the Swamp Creek area southward 

through Walkers Prairie to near the mouth of the basin, the 

unit is extremely coarse-grained in most of the upper 20–30 ft 

where cobbles, boulders, and gravel are common. The lower 

part of the aquifer generally is composed of gravel and sand 

with few cobbles or boulders. 

In the Camas Valley, where the Upper outwash aquifer 

is composed mostly of recent alluvial deposits along stream 

courses, it contains more sand and clay, and is therefore 

less productive than along Walkers Prairie. As illustrated on 

section A–A′ (pl. 2), the aquifer is about 15–30 ft thick over 

much of the Camas Valley, but thickens to about 80 ft near the 

outlet of the valley near well 30N/40E-32P01. Although thick 

coarse-grained outwash deposits occur on the northern slopes 

of Camas Valley (fig. 7), they are not fully saturated; therefore, 

unreliable amounts of water generally are produced. For 

example, drillers noted nearly 300 ft of dry gravel and sand 

in well 30N/40E-30K01D1 before drilling into deeper more 

saturated material (pl. 2, section B–B′).

The Landslide unit (LU) is composed of poorly sorted 

deposits of broken basalt and sedimentary interbeds of the 

Columbia River Basalt Group, covered in places by glacial 

deposits. Locally, the Landslide unit is an aquifer with variable 

yields and supplies water to nine of the project wells. The 

unit occurs along the eastern slopes of the basalt mesa on the 

eastern uplands of the Spokane Indian Reservation and on 

the western flanks of Happy Hill near Ford. The extent of this 

hydrogeologic unit at land surface corresponds to the geologic 

unit Qmw shown on plate 2. The approximate extent of this 

unit below land surface is shown on hydrogeologic sections 

D–D′ through I–I′ (pl. 2). As illustrated on the sections, the 

Landslide unit likely is in hydraulic connection with the Upper 

outwash aquifer along Walkers Prairie. 

The Valley confining unit (VC) consists mostly of 

low-permeability glaciolacustrine silt and clay (Qla). The 

unit occurs at depth throughout the Camas and Chamokane 

Valleys and is continuous northward into the Colville Valley 

(fig. 8; pl. 2, section I–I′). Discontinuous lenses of sand or 

gravel within the unit contribute usable quantities of water to 

some wells; 16 of the project wells are completed in this unit 

(pl. 1; table 1). Coarse-grained lenses within the VC appear 

to be more common in the southern part of the basin where 

Missoula flood deposits following the Spokane River drainage 

are interbedded with the glaciolacustrine deposits (pl. 2, 

section G–G′). Thickness of the VC commonly is 150–300 ft 

along the Camas and Chamokane Valleys and exceeds 300 ft 

in the central Camas Valley, Swamp Creek area, and near Ford 

(fig. 8).

The Lower aquifer (LA) is a confined aquifer consisting 

of sand and some gravel that occurs at depth in the Camas and 

Chamokane Valleys below the Valley confining unit (pl. 2, 

sections A–A′ through I–I′). Thirty of the project wells are 

completed in this unit (table 1, pl. 1). The Lower aquifer is 

continuous northward into the Colville Valley (pl. 2, section 

I–I′). The approximate southern extent of the Lower aquier 

is shown as being truncated near Chamokane Falls based on 

surficial outcrop of bedrock in that vicinity and well records 

that indicate the absence of a lower aquifer (pl. 2, southern 

end of I–I′; fig. 10). The Chamokane basin Lower aquifer does 

not appear to be connnected with similar deposits along the 

Spokane River. The thickness of LA is not well known. Only 

two project wells, 28N/39E-23P01 (pl. 2, section I–I′) and 

28N/40E-17C01 (pl. 2, sections F–F’ and I–I’), fully penetrate 

the Lower aquifer and reach the underlying Bedrock unit. 

At these two wells, the thickness of the Lower aquifer was 

interpreted to be 125 ft and 138 ft, respectively. 

The Basalt unit (BT) is composed of Columbia River 

Basalt, a dense, dark basalt with generally fine-grained 

interbeds. Locally, coarse-grained interbeds occur in the 

unit west of Springdale. Water from cracks and fractures in 

the basalt and from zones between lava flows supplied 18 

of the project wells (table 1, pl. 1). The Basalt unit occurs 

at land surface in the eastern uplands of the Spokane Indian 

Reservation and on Lyons Hill and Craney Hill (pl. 2). This 

hydrogeologic unit includes Miocene basalt (Mb) overlain 

by thin and discontinuous Quaternary loess (Qlo) and glacial 

deposits (Qgu). The thickness of the unit in the Chamokane 

Creek basin is largely unknown. One project well, 28N/39E36D01, penetrated 253 ft of basalt before reaching the 

underlying granite (pl. 2, section H–H′).
22 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

The Bedrock unit (BR) includes argillite, conglomerate, 

dolomite, gneiss, schist, slate, quartzite, shale, limestone, 

and granite. The unit locally yields usable quantities of water 

where rocks are fractured. Nineteen project wells obtain their 

water from this unit. Yields generally are small and numerous 

abandoned wells are in the unit. The Bedrock hydrogeologic 

unit includes geologic unit Tybr and thin and discontinuous 

Qal, Qlo, and Qgf that overly the bedrock.

Horizontal Hydraulic Conductivity

Hydraulic conductivity is a measure of a material’s ability 

to transmit water. In unconsolidated sediment, it is dependent 

on the size, shape, distribution, and packing of the particles. 

These characteristics vary within each hydrogeologic unit and 

hydraulic conductivity values vary correspondingly.

Horizontal hydraulic conductivity was estimated for the 

hydrogeologic units using the drawdown/discharge relation 

reported on drillers’ logs that reported pump testing wells for 

1– 6.5 hours. Only data from those wells with a driller’s log 

containing discharge rate, duration of pumping, drawdown, 

static water level, well-construction data, and lithologic log 

were used.

Two methods were used to estimate hydraulic 

conductivity, depending on well construction. For data from 

wells with a screened or perforated interval, the modified 

Theis equation (Ferris and others, 1962) was first used to 

estimate transmissivity of the pumped interval. Transmissivity 

is the product of horizontal hydraulic conductivity and 

thickness of the hydrogeologic unit supplying water to the 

well. 

The modified equation is

2

2.25 ln

4

where

= drawdown in the well, in feet;

discharge, or pumping rate, of the well,

 in cubic feet per day;

transmissivity of the hydrogeologic unit,

 in square feet per day;

length o

Q Tt s

T r S

s

Q

T

t

= π

=

=

= f time the well was pumped, in days;

radius of the well, in feet; and

storage coefficient, a dimensionless number,

 assumed to be 0.0001 for confined units

 and 0.1 for unconfined units.

r

S

=

=

(1)

Assumptions for using equation 1 are that aquifers are 

homogeneous, isotropic, and infinite in extent; wells are 

fully penetrating; flow to the well is horizontal; and water 

is released from storage instantaneously. Additionally, for 

unconfined aquifers, drawdown is assumed to be small in 

relation to the saturated thickness of the aquifer. Although 

many of the assumptions are not precisely met, the field 

conditions in the study area approximate most of the 

assumptions.

A computer program was used to solve equation 1 for 

transmissivity (T) using Newton’s iterative method (Carnahan 

and others, 1969). The calculated transmissivity values 

were not sensitive to assumed storage coefficient values; the 

difference in computed transmissivity between using 0.1 and 

0.0001 for the storage coeffecient is a factor of only about 2. 

The following equation was used to calculate horizontal 

hydraulic conductivity from the calculated transmissivity:

where

horizontal hydraulic conductivity of 

the geologic material near the well 

opening, in feet per day; and

thickness, in feet, approximated using the 

 length of the open interval as report

h

h

T K

b

K

b

=

=

=

ed in

 the driller's report.

(2)

The use of the length of a well’s open interval for b

overestimates values of Kh because the equations assume that 

all the water flows horizontally within a layer of this thickness. 

Although some of the flow will be outside this interval, the 

amount may be relatively small because in most sedimentary 

deposits, vertical flow is inhibited by layering.

For data from wells having only an open ended casing 

(no perforations), a second equation was used to estimate 

hydraulic conductivities. Bear (1979) provides an equation 

for hemispherical flow to an open-ended well just penetrating 

a hydrogeologic unit. When modified for spherical flow to an 

open-ended well within a unit, the equation becomes

4 h

Q K

sr = π

(3)

Equation 3 is based on the assumption that horizontal and 

vertical hydraulic conductivities are equal, which is not likely 

for the deposits in the study area. The result of violating this 

assumption is underestimating Kh by an unknown amount.

Hydraulic conductivity data are summarized by 

hydrogeologic unit in the following table. Data were 

unavailable for the Landslide and Bedrock units. The median 

values of estimated hydraulic conductivities for the aquifers 

are similar in magnitude to values reported by Freeze and 

Cherry (1979) for similar materials: Upper outwash aquifer, 

540 ft/d and Lower aquifer, 19 ft/d. The medians of estimated 

hydraulic conductivities for the Valley confining unit (10 ft/d), 

and the Basalt unit (3.7 ft/d) are higher than is typical for most 

of the material in these units because the data for confining 

units usually are from zones where lenses of coarse material 

exist and, in the case of the Basalt unit, where fractures or 
Hydrogeologic Framework 23

sedimentary interbeds exist. As a result, the data are biased 

toward the more productive zones in these units and are not 

representative of the entire unit. The minimum hydraulic 

conductivities for the hydrogeologic units illustrate that 

there are zones of low hydraulic conductivity in most units. 

Additionally, the range of hydraulic conductivities is at least 

three orders of magnitude for most units, indicating substantial 

heterogeneity and inherent uncertainty in estimating hydraulic 

conductivity.

Hydrogeologic

unit

Estimated hydraulic conductivity 

(feet per day)

Minimum Median Maximum Number 

of values

Upper outwash aquifer 15 540 7,900 10

Valley confining unit 2 10 860 4

Lower aquifer 4 19 3,000 8

Basalt unit .93 3.7 6.5 2

Estimates of horizontal hydraulic conductivity reported 

in several other investigations provide useful comparisons 

to the values estimated during this investigation. Buchanan 

and others (1988) reported an average horizontal hydraulic 

conductivity of 2,664 ft/d for the Upper outwash aquifer 

of Walkers Prairie based on a long-term pump test with 

multiple observation wells. On the Dawn millsite south of 

Ford, the horizontal hydraulic conductivity of the Upper 

outwash aquifer was estimated to be 14–140 ft/d based on 

pump test data (Washington Department of Health, 1991). 

Golder Associates, Inc. (2008) reported an average horizontal 

hydraulic conductivity of 331 ft/d for the Lower aquifer near 

the southern end of Chamokane Creek basin based on specific 

capacity data. Horizontal hydraulic conductivity of the 

Lower aquifer near Galbraith Springs is approximately 

1,300 ft/day, based on a pump test conducted by 

Rittenhouse‐Zeman and Associates, Inc. (1989). Whiteman 

and others (1994) estimated the median hydraulic conductivity 

of the Grande Ronde Basalt over the Columbia Plateau as 

4.9ft/d based on specific capacity data. 

Although many uncertainties are in the estimated values 

of hydraulic conductivity, these estimates provide an initial 

assessment of the relative differences in hydraulic conductivity 

between the different hydrogeologic units. These relative 

differences provide the basis for an initial conceptual model 

of hydraulic conductivity values to be used in the GSFLOW 

model; these values will be refined during model calibration. 

Yield and Specific Capacity

A summary of well yields, as reported on drillers’ 

logs used during this investigation, is shown in table 3 by 

hydrogeologic unit. Well-yield testing is done to determine 

if an adequate and sustainable yield is available from a well. 

Driller-reported well yields are not only dependent on the 

productivity of the unit to which the well is open, but also 

is a function of the design and purpose of the well. During 

well-yield testing, a well intended for municipal purposes 

likely would be pumped at a higher rate and have a larger 

diameter casing and a longer open interval than one intended 

for single-family use, thereby having an apparent higher yield 

than that for the single-family well. Despite the fact that yields 

often are estimates, they are useful in comparing the general 

productivity of hydrogeologic units; they also illustrate the 

variability within a single unit. Based on the data set used for 

this study, the median yields for the Upper outwash aquifer, 

the Landslide unit, the Valley confining unit, the Lower 

aquifer, the Basalt unit, and the Bedrock unit are 25, 45, 10, 

55, 11, and 3 gal/min, respectively. 

A summary of specific capacity information, derived 

from driller-reported yield divided by the drawdown measured 

in the well during pumping, is shown in the table below, by 

hydrogeologic unit. Specific capacity often is used to describe 

the productivity of a hydrogeologic unit. Based on the data set 

used for this study, the median specific capacity for the Upper 

outwash aquifer, the Valley confining unit, the Lower aquifer, 

and the Basalt unit are 7.6, 1.7, 0.62, and 0.18 (gal/min)/ft, 

respectively. Specific capacity is expected to be smaller for 

confined aquifers than unconfined aquifers (Freeze and Cherry, 

1979).

Table 3. Summary of yield and specific capacity for hydrogeologic units in the Chamokane Creek basin, Stevens County, Washington.

[0 indicates dry well. Abbreviations: gal/min, gallon per minute; (gal/min)/ft, gallon per minute per foot; –, no data]

Hydrogeologic unit

Yield

(gal/min)

Specific capacity

([gal/min]/ft)

Minimum Median Maximum Number of 

values Minimum Median Maximum Number of values

Upper outwash aquifer 0 25 2,000 49 0.7 7.6 190 8

Landslide unit 15 45 100 9 – – – –

Valley confining unit 0 10 38 14 .07 1.7 15 4

Lower aquifer 2 55 400 32 .12 .62 4.1 7

Basalt unit 2 11 40 16 .15 .18 .21 2

Bedrock unit .25 3 20 18 – – – –
24 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

Occurrence and Movement of 

Groundwater

Recharge

Direct precipitation recharges the Upper outwash aquifer 

over its extent and streamflow recharges the aquifer where 

losing stream reaches directly overlie the aquifer. Significant 

mountain-front recharge also may occur along the perimeter 

of the aquifer where it is in contact with Landslide unit 

deposits or productive zones within the Basalt or Bedrock 

hydrogeologic units. Recharge to the Upper outwash aquifer 

from streams is discussed in detail later in this report. 

Recharge from precipitation and other sources will be 

estimated in Phase 2 of this investigation.

Recharge to the Lower aquifer likely occurs in several 

areas. Water-level data indicate that recharge occurs from near 

Springdale through the Swamp Creek area where vertical head 

gradients between the Upper and Lower aquifers generally 

are downward. Localized recharge also occurs along the walls 

of the Camas Valley and Walkers Prairie where coarse talus 

slopes and landslide deposits along basalt bluffs or glacial 

outwash fans overlie and interfinger with the otherwise 

continuous Valley confining unit. 

Groundwater Flow Directions

 To estimate directions of horizontal groundwater 

flow, water-level maps were drawn for the Upper outwash 

aquifer and the Lower aquifer. Contours of equal waterlevel altitudes were manually drawn at convenient intervals, 

using approximate linear interpretation between point 

measurements, topographic map contours, and streamsurface altitudes where appropriate. The directions of flow 

were inferred to be from higher to lower water levels and 

perpendicular to water‐level contours where data were 

sufficient to draw contours. Groundwater levels measured 

during the well inventory (autumn 2007) were used to 

construct the water-level maps.

Horizontal groundwater flow in the Upper outwash 

aquifer generally mimics the surface-water drainage pattern of 

the basin. Groundwater flow moves from the topographically 

high tributary-basin areas toward the topographically lower 

valley floors (fig. 9). Over the entire basin, water-level 

altitudes in the Upper outwash aquifer range from 2,150 ft 

in the Camas Valley to 1,760 ft near Ford. The general 

distribution of horizontal gradients was about 13–50 ft/mi in 

the Camas Valley, about 80 ft/mi where Chamokane Creek 

exits Icebox Canyon to near its confluence with Swamp Creek, 

20–30 ft/mi from south of Springdale through the Swamp 

Creek area, and 12–16 ft/mi along Walkers Prairie. The 

smallest gradient in the Upper outwash aquifer, about 12 ft/mi, 

was measured along Walkers Prairie. 

Horizontal groundwater flow in the Lower aquifer is 

south to southwest from near Springdale to south of Ford 

(fig. 10). Along the Chamokane Valley floor, water-level 

altitudes within the Lower aquifer range from 1,885 ft near 

Swamp Creek to 1,600 ft near the lower end of the basin. 

Horizontal gradients are about 20 ft/mi along Walkers Prairie 

but increase to between 80 and 200 ft/mi from near Ford 

to the southern extent of the Lower aquifer where the unit 

thins or pinches out (fig. 10). In the Camas Valley, horizontal 

groundwater flow is to the east and water-level altitudes 

range from about 2,150 to less than 2,050 ft with a horizontal 

gradient of about 100 ft/mi. 

The location of the groundwater divide for the Lower 

aquifer is near the surface-water divide for the basin, near 

Springdale, Wash. (fig. 10). Its location was determined by 

measuring water levels in Lower aquifer wells north and 

south of the surface-water divide in the Colville River and 

Chamokane Creek basins, respectively. The groundwater 

divide is approximately mid-way between two 1,885 ft 

waterlevel altitude contours, one in the Colville River basin 

and one in the Chamokane Creek basin (fig. 10). 

Directions of vertical flow were inferred from water-level 

altitudes in the Upper outwash aquifer and the Lower aquifer 

where the units overlie one another. Water-level altitudes in 

closely spaced wells also were reviewed to assess if vertical 

gradients could be determined. In wells 29N/40E-09G03 

and 09G02 downstream of Icebox Canyon and upstream of 

Swamp Creek (pl. 1), the difference in water levels was almost 

60 ft, with a downward gradient from the Upper outwash 

aquifer to the underlying Lower aquifer. Conversely, in wells 

29N/40E-15R02 and 15Q02 about 2 m farther downgradient, 

the difference in water levels was about 20 ft, with an upward 

gradient from the Lower aquifer to the overlying Upper 

outwash aquifer. In wells 28N/40E-05A01 and 05A02 (pl. 1), 

the difference in water levels was about 4 ft, again with an 

upward gradient from the Lower aquifer to the overlying 

Upper outwash aquifer. Based on available water-level 

data, vertical flow in the basin generally is downward in the 

high-altitude areas of the side basins and near Swamp Creek. 

Vertical flow along Walkers Prairie generally is upward. In 

the Camas Valley, an upward vertical head gradient exists at 

flowing well 29N/39E-02J01, but at wells 30N/40E-31N01 

and 29N/40E-06D01, the difference in water levels was about 

90 ft, with a downward gradient from the Valley confining unit 

to the Lower aquifer. Flowing well 28N/39E-24K01, near the 

mouth of the Chamokane Creek basin, indicates upward flow 

from the Valley confining unit to the overlying Upper outwash 

aquifer.
Occurrence and Movement of Groundwater 25

watac10-0434_fig 09

EXPLANATION

Areal extent of the

 Upper outwash aquifer

 

Inferred direction of

 groundwater flow

 

Line of equal water-level

 altitude, in feet above NAVD88

1760

2140

1800

1780

1760

1820

1940

1860

2150

1840

1920

2060

2100

1980

1960

1960

2060

2140

48°

47°

50'

118°

T.

30

N.

T.

29

N.

T.

28

N.

T.

27

N.

117°45'

R. 38 E. R. 39 E. R. 40 E. R. 41 E.

Base from U.S. Geological Survey digital data, 1983, 1:100,000

Universal Transverse Mercator projection, Zone 11

Horizontal Datum: North American Datum of 1983 (NAD 83)

0 5 10 MILES

0 5 10 KILOMETERS

Chamokane

Valley

Craney

Hill

Camas

Valley

Swamp

Creek

Walkers

Prairie

Ice Box

Canyon

Springdale

Ford

Creek

Ch

a

m

okane

Colville

R.

Figure 9. Areal extent, water-level altitudes, and inferred directions of groundwater flow in the Upper outwash aquifer in the 

Chamokane Creek basin, Stevens County, Washington.
26 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

Figure 10. Areal extent, water-level altitudes, and inferred directions of groundwater flow in the Lower aquifer in the 

Chamokane Creek basin, Stevens County, Washington.

watac10-0434_fig 10

EXPLANATION

Areal extent of the

 Lower aquifer

 

Inferred direction of

 groundwater flow

 

1800 Line of equal water-level

 altitude, in feet above NAVD88

1860

2050

2150

1885

1885

1880

1840

1800

1600

1650

48°

47°

50'

118°

T.

30

N.

T.

29

N.

T.

28

N.

T.

27

N.

117°45'

R. 38 E. R. 39 E. R. 40 E. R. 41 E.

Base from U.S. Geological Survey digital data, 1983, 1:100,000

Universal Transverse Mercator projection, Zone 11

Horizontal Datum: North American Datum of 1983 (NAD 83)

0 5 10 MILES

0 5 10 KILOMETERS

1700

Chamokane

Valley

Swamp

Creek

Walkers

Prairie

Ice Box

Canyon

Springdale

Camas

Valley

Ford

Creek

Chamoka ne

Colville

R.
Occurrence and Movement of Groundwater 27

Groundwater Discharge 

Discharge from the Upper outwash aquifer occurs 

mostly as pumping from wells and at springs and seeps. A 

line of springs and seeps along an arcuate bluff west of Ford 

represents the major discharge zone of the Upper outwash 

aquifer (pl. 1). Outflow from this region supports year‐round 

flow in Chamokane Creek downstream of Ford. Springs 

discharging from the Upper outwash aquifer along Swamp 

Creek and between Icebox Canyon and the confluence of 

Chamokane and Swamp Creeks (pl. 1) support streamflow in 

those stream reaches. Just downstream, however, surface‐flow 

in the stream disappears during much of the year near the 

northeast corner of the Spokane Indian Reservation. Discharge 

from the Lower aquifer occurs as pumping from wells and, 

in areas of upward flow gradients, as discharge to overlying 

hydrogeologic units. In Camas Valley, one flowing well, 

29N/39E-02J01, discharges at land surface. At the east end 

of Camas Valley, groundwater flow likely discharges into 

overlying sediments and Chamokane Creek near the head of 

Icebox Canyon. Similarly, discharge at the lower end of the 

basin, south of Ford, may be upward through overlying units 

and ultimately into Chamokane Creek. 

Seasonal Variations in Groundwater Levels

Median water-level altitudes measured during the 

synoptic measurements in spring 2008 (March 24–April 1, 

2008) generally were slightly higher than those measured 

during the synoptic measurements in autumn 2007. The 

following table summarizes the differences in water levels 

between autumn 2007 and spring 2008 by hydrogeologic unit.

Hydrogeologic

unit

Difference in water level altitude

(feet)

Minimum Median Maximum Number 

of values

Upper outwash aquifer -1.5 0.15 7.57 29

Landslide unit -2.58 .20 15.05 6

Valley confining unit -.79 .90 3.24 4

Lower aquifer -1.94 .04 5.94 15

Basalt unit -.3 2.37 5.28 6

Bedrock unit -1.83 -.61 2.85 5

Due to higher than usual snow fall and continued freezing 

temperatures in early 2008, however, the spring 2008 

synoptic measurements were made before water-level 

altitudes reached their spring maximums based on subsequent 

monthly measurements. Therefore, the maximum seasonal 

variation in water-level altitudes was better documented by 

the monitoring-well network where monthly depth-to-water 

measurements were made from March 2008 to December 

2009. 

The first rise on the hydrographs (generally from 

autumn 2007 or winter 2008 through June 2008) shows that 

in the Upper outwash aquifer, water level altitudes commonly 

rose from about 2 to nearly 10 ft (see hydrographs for wells 

28N/40E-17J01, 28N/40E-05A01, 29N/40E-15R02, and 

29N/40E-23M06; pl. 1). The highest water-level altitudes in the 

Upper outwash aquifer occurred about 5–6 months after peak 

winter precipitation (snowfall reported as water equivalent) 

was measured at the AgriMet station in December 2007, and 

1–3 months after peak discharge was recorded downstream of 

Chamokane Falls (pl. 1). The second rise on the hydrographs 

generally was several feet less than the first, corresponding 

to less precipitation in December 2008 through January 2009 

compared to the previous year (pl. 1). The combined data set 

for this study indicate that peak snowfall occurred in December; 

snowmelt and, therefore, stream discharge peaked in April and 

groundwater levels in the Upper outwash aquifer then peaked 

about 1–3 months later after streamflow infiltration passed 

through the unsaturated zone and recharged the shallow aquifer.

Water-level altitudes in the Lower aquifer rose about 3–4 ft 

in the first season (see hydrographs for wells 28N/39E-26E01, 

28N/40E-17C01, and 28N/40E-05A02; pl. 1) and slightly less 

the second season. Similar to water levels in the Upper outwash 

aquifer, the highest water-level altitudes in the Lower aquifer 

occurred about 5–6 months after the highest precipitation. 

The paired hydrographs for closely spaced wells, one 

completed in the Upper outwash aquifer and one completed 

in the Lower aquifer, indicate nearly identical timing of the 

seasonal rise and falls in water levels (wells 28N/40E-05A01 

and 05A02, 28N/40E-17J01 and 17C01, and 29N/40E-15R02 

and 15Q02; pl. 1). The Upper aquifer water levels exhibited 

a slightly greater seasonal fluctuation, particularly in well 

28N/40E-17J01, than the Lower aquifer water levels. This was 

expected given the unconfined nature of the Upper aquifer 

and its close proximity to recharge from losing stream reaches 

and from precipitation. The overall similarity of fluctuations 

in water levels in the Upper outwash aquifer and the Lower 

aquifer indicates that these aquifers may be well connected 

despite the apparently continuous Valley confining unit that 

separates them. 

Long term (1959–2007) water-level and precipitation 

records indicate similar relations between groundwater 

levels and precipitation as those measured during this study 

(2007–09). Figure 11 shows long term water-level elevations 

for three wells (28N/40E-17J01, 28N/40E-08H02, and 

28N/40E-28P01) and long term precipitation for the Wellpinit, 

Washington station, the closest long term weather station 

to the basin. Water levels have been measured in six wells, 

including the three listed above, by Chamokane Water Masters 

from 1971 to present (2010) (James Lyerla, Chamokane Water 

Master, written commun., 2007). Additionally, water levels 

were measured in well 28N/40E-17J01 bimonthly from 1957 

to1980 by the U.S. Geological Survey. Precipitation has been 

measured at the Wellpinit station from1923 to present (2010) 

and monthly totals for 1923–2007 are available through the 

Western Regional Climate Center (2010). The long-term trends 

of water‐level altitudes follow climatic variability well without 

apparent long-term changes in water-levels (fig. 11). 
28 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

watac10-0434_fig 11

0691

4691

8691

2791

6791

0891

4891

8891

2991

6991

0002

4002

8002

1750176017701780179018001810182018301840

1850 10

987654321

0

GROUNDWATER ALTITUDE, IN FEET ABOVE NGVD 1929

MONTHLY PRECIPITATION, IN INCHES

28N / 40E- 17K01

28N / 40E- 08H02

28N / 40E- 17J01

28N / 40E- 28P01

Figure 11. Long-term groundwater-level altitudes in Chamokane Creek basin and precipitation for Wellpinit, Washington station.
Surface-Water System 29

Surface-Water System

Historical Streamflow

Historical streamflow records are available for one active 

USGS gaging station, Chamokane Creek below Falls near 

Long Lake (12433200) and one discontinued gaging station 

Chamokane Creek near Springdale(12433100). Mean annual 

discharge near the mouth of the basin at Chamokane Creek 

below Falls near Long Lake was 62.5 ft3/s for the 28 years 

when a complete record was available (1972–1978 and 

1988–2008). 

Snowmelt is the primary source of runoff in the 

watershed; rainfall is the secondary source of runoff and 

occasionally contributes to peak flows as rain-on-snow events. 

Mountain altitudes, even in the Huckleberry Mountains where 

the Chamokane Creek headwaters originate, are less than 

5,000 ft and the annual snowpack normally is entirely melted 

by mid-June. Peak flows from snowmelt commonly occur 

from March to mid-April; 20 of 28 recorded annual peak flows 

at Chamokane Creek below Falls near Long Lake occurred 

in March or April (table 4). The mean daily discharge at the 

gaging station typically reaches its low point by late July 

and remains low into October (fig. 12). Flows increase only 

slightly in October and early November due to autumn rains, 

but can increase significantly in December with the arrival of 

winter storms and greater precipitation.

The three headwater branches, the North Fork 

Chamokane Creek, the Middle Fork Chamokane Creek, and 

the South Fork Chamokane Creek, which form the main 

stem of Chamokane Creek are all intermittent in their upper 

reaches. Chamokane Creek becomes perennial most years 

in Camas Valley and remains so until it reaches the Walkers 

Prairie area where it again becomes intermittent due to 

seasonal infiltration losses through the channel bed. 

Springs

Springs are an important component of the Chamokane 

surface-water system and sustain much of the flow during 

the usually dry months of July to November. Groundwater 

discharges at a series of large springs at the southern end of 

Walkers Prairie along an east–west oriented bluff beginning 

just west of the town of Ford. Much of this hillside seeps water 

in places causing the stream channel to have swampy reaches. 

Larger outflows occur at the Dawn Mining Company spring, 

the Washington Department of Fish and Wildlife spring, the 

Water year Peak discharge

(ft3/s) Date

1972 332 02-29-72

1973 353 03-02-73

1974 1,430 01-16-74

1975 2,200 04-25-75

1976 316 04-09-76

1977 44 11-21-76

1978 326 03-24-78

1988 165 04-03-88

1989 435 03-14-89

1990 210 06-02-90

1991 250 04-06-91

1992 164 01-29-92

1993 661 03-24-93

1994 133 03-19-94

1995 1,140 03-12-95

1996 873 04-24-96

1997 1,810 03-20-97

1998 555 03-24-98

1999 1,110 02-26-99

2000 753 03-05-00

2001 90 03-20-01

2002 743 01-09-02

2003 992 03-16-03

2004 115 03-19-04

2005 401 03-28-05

2006 1,240 01-11-06

2007 712 03-13-07

2008 625 04-15-08

Table 4. Annual peak discharge for U.S. Geological Survey 

streamflow-gaging station 12433200, Chamokane Creek below 

Falls near Long Lake, Stevens County, Washington.

[Abbreviation: ft3/s, cubic feet per second]

Spokane Tribal Woodworks site, and the Galbraith Springs by 

the Spokane Tribal Fish Hatchery (pl. 1). Chamokane Creek is 

perennial downstream of these spring discharges and remains 

so, gaining water from the aquifer, for the rest of its course 

until its confluence with the Spokane River. 
30 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

Measuring the discharge of these springs is difficult 

because they are mostly in an area with widespread seepage 

and lack distinct boundaries. Total outflows from the 

Washington Department of Fish and Wildlife (WDFW) and 

the Tribal Fish Hatchery include some groundwater pumped 

from wells to supplement natural spring water used at these 

sites, which then becomes return water. Outflow at Galbraith 

Springs (12433187) and the outflow downstream of the 

Tribal Fish Hatchery (12433190), which includes Galbraith 

Springs and all return flow from the hatchery, were measured 

concurrently during three synoptic measurement sets as 

part of this study (tables 5–7). Measured discharge from the 

Tribal Fish Hatchery was 7.76 ft3/s on October 11, 2007, and 

9.87 ft3/s on April 17, 2008. The Stevens County Conservation 

District measured total outflow at the WDFW and the 

Spokane Fish Hatchery 27 times between November 1997 and 

March 1999. At the State hatchery, measurements ranged from 

a low of 6.1 ft3/s on January 5, 1998, to a high of 16.3 ft3/s 

on March 16, 1998. Measurements at the tribal hatchery 

ranged from a low of 3.0 ft3/s on January 5, 1998, to a high 

of 15.3 ft3/s on March 29, 1999 (C. Kessler, Stevens County 

Conservation District, written commun., 2009). 

The most complete attempt to measure the springs 

discharge was in 1987 (Wozniewicz, 1989). Measuring 

stations were established at the north (upgradient) end of the 

springs region downstream of the Ford bridge (near station 24; 

pl. 1), and at the south (downgradient) end just downstream 

of the confluence between Galbraith Springs and Chamokane 

Creek. Measurements were made at these stations and at all 

the major springs between stations during the low flow period 

from late July 1987 to late October 1987. The average total 

discharge of springs and seeps between the north and south 

measuring stations was 20.9 ft3/s and an additional average 

discharge of 2.0 ft3/s was calculated for springs and seeps 

between the south station and the USGS gaging station at 

Chamokane Creek below Falls near Long Lake (Wozniewicz, 

1989).

watac10-0434_fig 12

0

50

100

150

200

250

OCT NOV DEC JAN FEB MAR APR MAY JUNE JULY AUG SEP

MEAN DAILY DISCHARGE, IN CUBIC FEET PER SECOND

1972–2009

WATER YEARS

USGS STREAMFLOW-GAGING STATION 12433200

Figure 12. Mean daily discharge for the period of record (1972–2009) for U.S. Geological Survey 

streamflow-gaging station 12433200, Chamokane Creek below Falls near Long Lake, Stevens 

County, Washington.
Surface-Water System 31

Swamp Creek is the only tributary to Chamokane Creek 

that is perennial; all other tributaries are intermittent. Swamp 

Creek differs from the other tributaries in that it does not 

originate in the highlands. Swamp Creek is spring fed and 

begins in a swampy area just west of the town of Springdale. 

Thomas Creek also is spring fed and flows southeast out of 

the hills at the western edge of Walkers Prairie (pl. 1), but 

terminates in a pond on the floodplain that appears to have 

no surface-water outlet. Tributaries other than Swamp Creek 

reach Chamokane Creek as surface flow only during the spring 

snowmelt season and for short periods after significant rainfall 

events. 

Streamflow Gains and Losses 

Three sets of synoptic discharge measurements were 

made at 28 sites along Chamokane Creek and its tributaries 

during this study (pl. 1) to identify gaining and losing reaches 

and to describe how surface water moves through the basin 

during high- and low-flow conditions. A gaining reach is 

where streamflow increases due to inflow of groundwater. A 

losing reach is where streamflow decreases due to outflow 

of water through the streambed into the ground. Two lowflow measurements were made during late summer or early 

autumn of 2007 and 2008, and are referred to as seepage runs 

that represent approximately steady-flow conditions. One 

set of high-flow synoptic discharge measurements was made 

in April 2008. For simplicity, the surface-water measuring 

sites are referred to by sequential map numbers (1–28) in the 

following text and on pl. 1 (tables 5–7 list full station names 

and eight-digit USGS gaging station numbers).

Tributaries in the Chamokane Creek basin are known 

to be intermittent with little if any surface flow reaching 

Chamokane Creek during the summer and autumn lowflow period. Therefore, tributary measuring sites were 

selected closer to their headwaters than the confluence with 

Chamokane Creek to minimize the number of dry channel 

locations. Because of their upstream locations, streamflow 

gain and loss data from many tributary measuring sites may 

not be representative of gains or losses along the main stem 

of Chamokane Creek. Additionally, although none were 

reported or observed, atypical activities occurring during a 

measurement, such as exceptionally high, short-term pumping 

from a near-stream well could affect the measurements. 

Furthermore, gains or losses of streamflow, as described in this 

report, refer to the cumulative or net gain or loss in streamflow 

between two measurement sites. It was beyond the scope of 

this study to locate and measure every tributary and surfacewater diversion and return, so the reported losses and gains in 

streamflow may be due to processes other than groundwater/

surface-water interactions. 

The first seepage run was completed in late September 

and early October 2007 to characterize low-flow streamflow 

conditions (table 5). Discharge was measured at most of the 

same sites during subsequent measurements made in 2008. 

Selected sites were not revisited. Site 12433060 (Unnamed 

Tributary Site 1 off Mickelson Road near Springdale) had no 

flow when visited on October 5, 2007, and was discontinued 

after better measuring conditions were determined at nearby 

site 12433062 (Unnamed Tributary Site 2 off Mickelson 

Road) on the same day. Site 12433048 (Unnamed Tributary 

at Bowler Road near Springdale) had no flow during the 2007 

and 2008 seepage runs and was not included in the April 2008 

high-flow measurement set. 

A review of long-term data for the Chamokane Creek 

below Falls gaging station indicates that the long term 

(1970–2008) daily mean flows are 27 and 29 ft3/s for 

September and October, respectively. This is nearly identical 

to the daily mean values of 27 and 28 ft3/s for September and 

October 2007. The similarity of long term mean flow and flow 

during the synoptic low-flow period implies that conditions at 

the time of the measurements were representative of typical 

conditions. 

Results of the 2007 seepage run indicate that no flow 

(or little flow) was observed throughout the upper reaches 

of Chamokane Creek, including the headwaters and Camas 

Valley sections. The only tributary in this section where 

any significant flow was measured was at site 12433067 

(Unnamed Tributary above Drum Road near Springdale) 

where flow was 0.18 ft3/s. Flow measured at site 12433075 

(Chamokane Creek above Swamp Creek near Springdale) 

was 1.02 ft3/s. No flow or minimal flow was measured in the 

Walkers Prairie area with no flow observed at site 12433100 

(Chamokane Creek near Springdale). Measured discharge at 

Chamokane Creek at Ford-Wellpinit Road (site 12433175) 

was 1.26 ft3/s on September 20, 2007. On the same date, 

discharge at Chamokane Creek below Falls near Long Lake 

(site 12433200) was 28 ft3/s (table 5).
32 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

Table 5. Seepage investigation, Chamokane Creek, Spokane River basin, Stevens County, Washington, September 18–October 11, 

2007.

[Map No. shown on plate 1. A series of discharge measurements were made September 18–October 11, 2007, on Chamokane Creek and some of its tributaries 

to study gains and losses (modified from U.S. Geological Survey, 2007). The reach covered 30.7 miles. River mile 31.8 is the confluence of Little Chamokane 

Creek and Spokane River; river mile 32.5 is the confluence of Chamokane Creek and Spokane River. Site name and location: Site names in bold are on the 

main stem of Chamokane Creek. Indented sites are tributary to the next listed site. Abbreviations: ft3/s, cubic foot per second; °C, degrees Celsius; –, no data] 

Map 

No.

Site name and 

location 

Measured 

discharge 

(ft3/s)

Date 

Net gain 

or loss

(ft3/s) 

Water 

temperature 

(°C)

1 Middle Fork Chamokane Creek near Springdale (12433020) 0 09-18-07 – –

2 South Fork Chamokane Creek near Springdale (12433030) 0 09-18-07 – –

3 Chamokane Creek below Forks, near Springdale (12433035) 0 09-18-07 – –

4 Unnamed Tributary at Rose Hill Road, near Springdale (12433040) 0 09-18-07 – –

5 Unnamed Tributary at Springdale-Hunters Highway, near Springdale 

(12433043)

0 09-18-07 – –

6 Unnamed Tributary at Bowler Road, near Springdale (12433048) 0 09-20-07 – –

7 Chamokane Creek at West Lyons Hill Road, near Springdale 

(12433055)

0 09-20-07 – –

8 Unnamed Tributary Site 1 off Mickelson Road, near Springdale (12433060) 0 10-05-07 – –

9 Unnamed Tributary Site 2 off Mickelson Road, near Springdale (12433062) .02 10-05-07 – 7.7

10 Unnamed Tributary above Drum Road, near Springdale (12433067) .18 10-11-07 – 7.5

11 Chamokane Creek at East Lyons Hill Road, near Springdale 

(12433070)

.01 09-19-07 1-0.19 7.6

12 Chamokane Creek above Swamp Creek, near Springdale (12433075) 1.02 09-19-07 +1.01 11.5

13 Swamp Creek at Cemetery Road, near Springdale (12433078) .84 09-19-07 – 10.4

14 Swamp Creek off Canfield Road, near Springdale (12433085) 1.09 09-25-07 – 11.5

15 Unnamed Tributary off Hidden Road, near Springdale (12433090) .09 09-20-07 – 6.2

16 Unnamed Tributary at Hidden Road, near Springdale (12433094) 0 09-19-07 – –

17 Chamokane Creek near Springdale (12433100) 0 09-18-07 -2.11 –

18 Unnamed Tributary at Fortymile Canyon Road, near Springdale (12433105) 0 09-25-07 – –

19 Unnamed Tributary at Fortymile Canyon, near Springdale (12433110) 0 09-25-07 – –

20 Unnamed Tributary off Reservation Road, near Ford (12433135) .06 09-21-07 – 8.4

21 Rail Creek below Bartlett Creek, near Ford (12433145) .18 09-25-07 – 8.7

22 Thomas Creek near Ford (12433155) .32 09-27-07 – 9.7

23 Negro Creek near Ford (12433170) .04 09-27-07 – 10.3

24 Chamokane Creek at Ford-Wellpinit Road, near Ford (12433175) 1.26 09-20-07 10.66 10.3

25 Moses Creek near Ford (12433180) .03 09-27-07 – 10.6

26 Galbraith Springs outflow near Ford (12433187) 4.18 10-11-07 – 11.5

27 Tribal hatchery outflow near Ford (12433190) 7.76 10-11-07 – 11.3

28 Chamokane Creek below Falls near Long Lake (12433200) 228 09-20-07 1+19 –

1

Value may not be representative of actual gain or loss along the mainstem of Chamokane Creek because discharge from tributary streams was measured 

closer to the headwaters of the tributaries than to their confluence with Chamokane Creek. 

2

Discharge calculated from gage height.
Surface-Water System 33

Table 6. High-flow investigation, Chamokane Creek, Spokane River basin, Stevens County, Washington, April 14–17, 2008.

[Map No. shown on plate 1. A series of discharge measurements were made April 14–17, 2008, on Chamokane Creek and some of its tributaries to study nearpeak discharge (modifed from U.S. Geological Survey, 2008). The reach covered 30.7 miles. River mile 31.8 is the confluence of Little Chamokane Creek and 

Spokane River; river mile 32.5 is the confluence of Chamokane Creek and Spokane River. Site name and location: Site names in bold are located on the main 

stem of Chamokane Creek. Indented sites are tributary to the next listed site. Abbreviations: ft3/s, cubic foot per second; °C, degrees Celsius; –, no data]

Map 

No. Site name and location

Measured 

discharge 

(ft3/s)

Date

Net gain 

or loss

(ft3/s)

Water 

temperature 

( ̊C)

1 Middle Fork Chamokane Creek near Springdale (12433020) 206 04-14-08 – 3.7

2 South Fork Chamokane Creek near Springdale (12433030) 159 04-15-08 – 2.9

3 Chamokane Creek below Forks near Springdale (12433035) 333 04-15-08 -32.0 2.9

4 Unnamed Tributary at Rose Hill Road, near Springdale (12433040) 11.1 04-14-08 – 3.8

5 Unnamed Tributary at Springdale-Hunters Highway, near Springdale 

(12433043)

37.6 04-14-08 – 4.5

7 Chamokane Creek at West Lyons Hill Road, near Springdale 

(12433055)

425 04-15-08 +54.4 5.0

9 Unnamed Tributary Site 2 off Mickelson Road, near Springdale 

(12433062)

6.23 04-14-08 – 4.5

10 Unnamed Tributary above Drum Road, near Springdale (12433067) 3.66 04-17-08 – 7.6

11 Chamokane Creek at East Lyons Hill Road, near Springdale 

(12433070)

522 04-15-08 1+87.1 2.7

12 Chamokane Creek above Swamp Creek, near Springdale (12433075) 502 04-15-08 2-20.0 4.0

13 Swamp Creek at Cemetery Road, near Springdale (12433078) 2.87 04-14-08 – 12.6

14 Swamp Creek off Canfield Road, near Springdale (12433085) 2.10 04-15-08 – 10.5

15 Unnamed Tributary off Hidden Road, near Springdale (12433090) 1.44 04-14-08 – –

16 Unnamed Tributary at Hidden Road, near Springdale (12433094) 1.46 04-14-08 – –

17 Chamokane Creek near Springdale (12433100) 348 04-16-08 3-159 5.9

18 Unnamed Tributary at Fortymile Canyon Road, near Springdale 

(12433105)

6.50 04-14-08 – –

19 Unnamed Tributary at Fortymile Canyon, near Springdale (12433110) 6.78 04-14-08 – –

20 Unnamed Tributary off Reservation Road, near Ford (12433135) 1.09 04-15-08 – 4.5

21 Rail Creek below Bartlett Creek, near Ford (12433145) 15.9 04-14-08 – 4.9

22 Thomas Creek near Ford (12433155) 1.14 04-15-08 – 8.3

23 Negro Creek near Ford (12433170) 8.08 04-14-08 – 5.1

24 Chamokane Creek at Ford-Wellpinit Road, near Ford (12433175) 420 04-16-08 1+32.5 6.0

25 Moses Creek near Ford (12433180) 3.57 04-15-08 – 4.3

26 Galbraith Springs outflow near Ford (12433187) 7.23 04-17-08 – 12.6

27 Tribal hatchery outflow near Ford (12433190) 9.87 04-17-08 – 11.7

28 Chamokane Creek below Falls, near Long Lake (12433200) 422 04-16-08 -11.4 –

1

Value may not be representative of actual gain or loss along the main stem of Chamokane Creek because discharge from tributary streams was measured 

closer to the headwaters of the tributaries than to their confluence with Chamokane Creek.

2

Calculated difference may be less than measurement accuracy.

3

Part of this apparent loss may be due to overall drop in flows from April 15 to April 16, 2008.
34 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

 The second set of synoptic discharge measurements 

was completed between April 14 and 17, 2008 (table 6) 

to characterize high streamflow conditions. It was not 

possible to determine how close to the actual peak discharge 

these individual measurements were, but the timing of the 

measurements overlapped with the 2008 water year peak 

discharge (625 ft3/s) for Chamokane Creek below Falls on 

April 15. Spring runoff flows can increase and decrease 

rapidly making it difficult to collect complete comparison 

data between sites when it is not possible to complete all 

measurements at the same time. This problem is clearly 

illustrated at site 12433055 (Chamokane Creek at West Lyons 

Hill Road) where two measurements were made one day 

apart during the high flow period. Measured discharge at 

site 12433055 was 425 ft3/s on April 15, 2008 (table 6), but 

had decreased to 315 ft3/s when a follow up measurement 

was made the next day. This decrease of 110 ft3/s, just 

over 25 percent, is not unusual during a runoff event. The 

measurement results were supported by high water marks 

observed on April 16 that indicated the stream had already 

decreased about 2 ft from its recent peak. 

The April 2008 high-flow measurements indicate that 

Chamokane Creek generally gained flow in its headwaters and 

along the length of Camas Valley until it achieved its greatest 

measured discharge (522 ft3/s) at site 12433070 (Chamokane 

Creek at East Lyons Hill Road near Springdale) close to the 

eastern edge of Camas Valley. The creek then began losing 

flow steadily downstream toward the Walkers Prairie area. 

Measured discharge was only 348 ft3/s at the gaging station 

(12433100). Farther downstream, discharge increased due 

to tributary input as the creek continued southward across 

Walkers Prairie. The most significant tributary contribution 

in this section was from Rail Creek where 15.9 ft3/s was 

measured at site 12433145 (Rail Creek below Bartlett 

Creek near Ford). No significant difference in discharge 

was measured between the south end of Walkers Prairie at 

site 12433175 (Chamokane Creek at Ford-Wellpinit Road 

near Ford; 420 ft3/s) and at Chamokane Creek below Falls 

(422 ft3/s). 

The final seepage run was done in late August 2008 

using the same measurement locations (table 7) except site 

12433187 (Galbraith Springs outflow near Ford) and site 

12433190 (Tribal hatchery outflow near Ford), which were 

measured on September 2, 2008. This was an opportune time 

frame for this final set of seepage run measurements because 

the monthly mean discharge for August 2008 for Chamokane 

Creek below Falls was equal to the long term monthly mean 

of 27 ft3/s at the same station for the period of record. Data 

from the 2008 seepage run showed similar low-flow trends to 

those determined in the initial 2007 seepage run. Conditions 

can differ substantially at low-flow from one year to another 

due to seasonal weather variations and annual flow magnitude. 

It should not be assumed that they are representative of other 

periods even though results of the 2007 and 2008 seepage 

runs follow each other closely. No flow (or little flow) was 

measured throughout the upper reaches of Chamokane Creek, 

including the headwaters and Camas Valley sections in 

2007 and 2008. The only tributary in this section where any 

significant flow was measured was at site 12433067 (Unnamed 

Tributary above Drum Road near Springdale) where 

0.18 ft3/s was measured both years. Flows for site 12433075 

(Chamokane Creek above Swamp Creek near Springdale) 

were nearly the same both years. Measured streamflow for 

Swamp Creek were slightly higher in 2008, but those small 

differences may be because the 2008 measurements were 

made about 1 month earlier in the year. No flow or minimal 

flow was measured in the Walkers Prairie area both years with 

no flow observed at Chamokane Creek near Springdale during 

both seepage runs. No flow was observed in the creek on 

July 29, 1 month prior to the 2008 seepage run at this site.

Flow becomes intermittent early in the low flow season 

at many reaches in the Walkers Prairie area and dry channel 

reaches have been observed as early as May 27 in 2009. 

Measured discharge at Chamokane Creek at Ford-Wellpinit 

Road (1243317) was 1.26 ft3/s on September 20, 2007, 

and 1.65 ft3/s on August 28, 2008. The most noteworthy 

characteristic of Chamokane Creek streamflow is that nearly 

all of the total flow measured at Chamokane Creek below Falls 

during the low flow time of year is provided by groundwater 

discharge, mostly from large springs and numerous seeps 

in the section downstream of Ford and from outflow from 

hatcheries which is a combination of water from wells and 

springs.
Surface-Water System 35

Table 7. Seepage investigation, Chamokane Creek, Spokane River basin, Stevens County, Washington, August 25–September 2, 2008.

[Map No. shown on plate 1. A series of discharge measurements were made August 25–September 2, 2008, on Chamokane Creek and some of its tributaries 

to study gains and losses (modified from U.S. Geological Survey, 2008). The reach covered 30.7 miles. River mile 31.8 is the confluence of Little Chamokane 

Creek and Spokane River; river mile 32.5 is the confluence of Chamokane Creek and Spokane River. Site name and location: Site names in bold are located 

on the main stem of Chamokane Creek. Indented sites are tributary to the next listed site. Abbreviations: ft3/s, cubic foot per second; °C, degrees Celsius; –, no 

data]

Map 

No. Site name and location

Measured 

discharge 

(ft3/s)

Date

Gain or 

loss

(ft3/s)

Water 

temperature 

( ̊C)

1 Middle Fork Chamokane Creek near Springdale (12433020) 0 08-25-08 – 15.7

2 South Fork Chamokane Creek near Springdale (12433030) .08 08-25-08 – 13.7

3 Chamokane Creek below Forks, near Springdale (12433035) 0 08-25-08 – 14.6

4 Unnamed Tributary at Rose Hill Road, near Springdale (12433040) 0 08-25-08 – –

5 Unnamed Tributary at Springdale-Hunters Highway, near Springdale 

(12433043)

0 08-25-08 – –

6 Unnamed Tributary at Bowler Road, near Springdale (12433048) 0 08-26-08 – 12.4

7 Chamokane Creek at West Lyons Hill Road, near Springdale 

(12433055)

0 08-26-08 – 16.2

9 Unnamed Tributary Site 2 off Mickelson Road, near Springdale (12433062) .02 08-25-08 – 8.5

10 Unnamed Tributary above Drum Road, near Springdale (12433067) .18 08-26-08 – 13.4

11 Chamokane Creek at East Lyons Hill Road, near Springdale 

(12433070)

.04 08-26-08 1-0.16 19.6

12 Chamokane Creek above Swamp Creek, near Springdale (12433075) 1.00 08-29-08 +.96 13.1

13 Swamp Creek at Cemetery Road, near Springdale (12433078) 1.00 08-28-08 – 14.2

14 Swamp Creek off Canfield Road, near Springdale (12433085) 1.43 08-28-08 – 14.5

15 Unnamed Tributary off Hidden Road, near Springdale (12433090) 0 08-28-08 – –

16 Unnamed Tributary at Hidden Road, near Springdale (12433094) 0 08-28-08 – –

17 Chamokane Creek near Springdale (12433100) 0 08-28-08 -2.43 14.4

18 Unnamed Tributary at Fortymile Canyon Road, near Springdale (12433105) .02 08-27-08 – 11.9

19 Unnamed Tributary at Fortymile Canyon, near Springdale (12433110) 0 08-27-08 – –

20 Unnamed Tributary off Reservation Road, near Ford (12433135) .05 08-27-08 – 13.7

21 Rail Creek below Bartlett Creek, near Ford (12433145) .35 08-29-08 – 12.4

22 Thomas Creek near Ford (12433155) .30 08-28-08 – 10.6

23 Negro Creek near Ford (12433170) .02 08-29-08 – 13.9

24 Chamokane Creek at Ford-Wellpinit Road, near Ford (12433175) 1.65 08-28-08 1+.91 13.7

25 Moses Creek near Ford (12433180) .04 08-28-08 – 12.7

26 Galbraith Springs outflow near Ford (12433187) 1.98 09-02-08 – 12.0

27 Tribal hatchery outflow near Ford (12433190) 7.95 09-02-08 – 12.8

28 Chamokane Creek below Falls, near Long Lake (12433200) 29.6 08-29-08 1+20.0 –

1

Value may not be representative of actual gain or loss along the main stem of Chamokane Creek because discharge from tributary streams was measured 

closer to the headwaters of the tributaries than to their confluence with Chamokane Creek.
36 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

Interactions Between Groundwaterand 

Surface Water

The data presented on the surface-water system indicates 

that there is considerable interaction between the near-surface 

hydrogeologic units and the surface water of the basin. 

Streamflow gains and losses along many reaches vary from 

month to month and from year to year. Exceptions to this 

were determined at the stream reaches with flow supported by 

perennial springs, most notably downstream of Ford where 

large springs discharge from the Upper outwash aquifer. Other 

spring-supported areas include Swamp Creek and Chamokane 

Creek between Ice Box Canyon and its confluence with 

Swamp Creek (Kessler, 2008). 

During the high-flow measurements made for this 

investigation, gains in streamflow occurred throughout 

the Camas Valley with the largest high-flow measurement 

(522 ft3/s) made at the mouth of Ice Box Canyon after 

Chamokane Creek exits Camas Valley. From the mouth of 

Ice Box Canyon to the northern end of Walkers Prairie large 

streamflow losses were recorded indicating that Chamokane 

Creek loses flow directly to the Upper outwash aquifer in 

that reach. Modest gains occurred along Chamokane Creek 

through Walkers Prairie, apparently due to inputs from 

tributary streams rather than groundwater discharge to the 

creek. An overall small loss of flow was measured downstream 

of Ford to the gaging station downstream of Chamokane Falls 

indicating modest recharge to the Upper outwash aquifer in 

the lower end of the basin.

In contrast, under low-flow conditions, only two 

reaches along Chamokane Creek show any significant gains 

in flow and both are due to springs discharging from the 

Upper outwash aquifer. The first area is between the outlet 

of Ice Box Canyon and just upstream of the confluence of 

Chamokane and Swamp Creeks where gains of about 1 ft3/s 

were measured in each of the low-flow measurements in 2007 

and 2008. The second area is downstream of Ford to near 

the gaging station at Chamokane Falls, where gains of about 

20 ft3/s were measured during both low-flow measurements. 

The largest loss in flow during both low-flow measurements, 

slightly more than 2 ft3/s, was measured between Chamokane 

Creek just upstream of its confluence with Swamp Creek and 

the northeast end of Walkers Prairie.

Additional comparisons of gain/loss patterns for specific 

reaches between low-flow and high-flow is valuable and 

has important implications for groundwater/surface-water 

interaction. For example, a small loss was measured during 

low flow, but a large gain was measured during high flow in 

the reach upstream of the outlet of Ice Box Canyon. The reach 

between the outlet of Ice Box Canyon and the confluence of 

Chamokane and Swamp Creeks gained during low flow and 

lost during high flow. These examples illustrate changes in the 

direction of groundwater/surface water fluxes as a function of 

hydrologic conditions.

Land Use and Land Cover 

Change Analysis

A land use and land cover (LULC) change analysis was 

done to supplement the understanding of the Chamokane 

Creek basin groundwater and surface-water system. Changes 

in land use and land cover can result in changes in recharge 

to the groundwater system and changes in how water is used 

in the basin. The overall goal of the analysis was to document 

LULC types near the time of the adjudication (1979) and 

currently (2009), and compare LULC changes between those 

two periods. A combination of satellite imagery classification 

using geospatial software, inspection of historical areal photos, 

and field verification of current LULC classes was used for 

this analysis. The complete LULC analysis is presented in 

appendix A, including data acquisition, image classification, 

accuracy assessment, and limitations. LULC data will be 

incorporated into the GSFLOW model that will be completed 

during Phase 2 of this project. A summary of the LULC 

analysis detailed in appendix A is provided below.

The LULC change analysis was done using images from 

clear days, unobstructed by cloud cover, on October 11, 1987, 

and July 3, 2009. Although data at the time of adjudication 

would have been ideal for this analysis, high quality satellite 

images were not available until October 1987. 

Seven LULC classes were identified in the classification 

process. 

Evergreen forest – Areas dominated by evergreen trees 

greater than 5 m tall.

Open forest – Areas of open, low-density evergreen trees 

that are greater than 5 m tall. These areas may be naturally 

open ponderosa pine forests or low-density forests 

resulting from harvesting activities. 

Shrub – Areas dominated by shrubs less than 5 m tall. 

These areas include true shrubs and young trees in an 

early successional stage. 

Grassland – Areas covered by grasses and other 

herbaceous vegetation. These areas are not subject to 

intensive management activities but may be used for 

grazing. 

Agriculture – Land that is used for the production of 

crops and is being actively tilled. Also includes pastures 

planted for livestock grazing. 

Developed/sparsely vegetated – Areas where there 

is little vegetation due to the presence of constructed 

materials, impervious surfaces, bare/barren land, or 

clearcuts. 

Water – Areas of open water. 
Land Use and Land Cover Change Analysis 37

The area distribution for LULC classes in 1987 and 

2009 is shown in figure 13. Forest cover is the dominant 

land cover type in the Chamokane Creek basin in 1987 and 

2009. Between 1987 and 2009, however, evergreen forest 

cover decreased by nearly 11,000 acres, or 14.5 percent of the 

original forest cover. Much of this decrease was a result of 

a change in classification of 9,800 acres of evergreen forest 

to open forest. Additionally, 5,300 acres of evergreen forest 

became shrub, 2,300 acres became grassland and 1,300 acres 

became developed/sparsely vegetated. Major changes in land 

cover to the evergreen forest category include 1,800 acres of 

grassland, 4,900 acres of shrub, and 740 acres of open forest. 

Therefore, the net changes of evergreen forest to shrub and 

evergreen forest to grassland were relatively small (less than 

about 500 acres). 

Open forest cover increased from 6.97 to 17.4 percent of 

the total basin area (an increase of more than 12,000 acres). 

As mentioned previously, this increase is predominantly 

due to a change in classification of about 9,800 acres of 

evergreen forest to open forest. Other major changes include 

about 1,800 acres of grassland, 1,600 acres of shrub, and 

1,800 acres of agriculture becoming open forest in 2009. 

About 1,800 acres of open forest changed in classification to 

grassland so the net change between open forest and grassland 

was minor. About 740 acres of open forest changed to 

evergreen forest. 

Chamokane Creek basin currently (2009) is an area 

dominated by forests with some pasture and agricultural 

lands. Development is still relatively sparse. Loss in forest 

cover represents the largest change in land cover in the basin 

between 1987 and 2009. This appears to be mostly due to 

forestry activities, especially in the northern part of the basin. 

Some of the loss in forest cover north of Ford may have been 

due to a 5,300-acre fire (less than half of which was originally 

in forest cover) that occurred in 1991. Since 1987, more than 

18,000 acres of evergreen forest have been logged and are at 

various stages of regrowth.

Recently, 1,300 of these acres were harvested, falling 

under the classification of “developed/sparsely vegetated.” 

Between 1987 and 2009, more than 7,000 acres of shrub, 

grassland and open forest changed in classification to 

evergreen forest, indicating previously logged areas that have 

now regenerated. 

Much of the increase in the open forest classification 

from 1987 to 2009 also is due to harvesting practices. 

Areas likely are being converted from evergreen forest to 

low‐density, open forests from logging activities. Although to 

a lesser extent, changes from evergreen forest to open forest 

also may be due to development activities, especially between 

the towns of Ford and Springdale. Development in the basin 

is at such a small scale relative to the pixel size of the satellite 

sensors (30 m2) that some development in this heavily 

forested area may be picked up only as open forest rather than 

developed/sparsely vegetated. 

Changes in shrub cover mainly occurred on lands where 

forestry activities took place. Changes from shrub cover, 

specifically of young evergreen trees, to forest cover likely are 

a result of regeneration, although changes from forest cover to 

shrub are due to recent logging activities, where regeneration 

is still ongoing. 

Changes that involve deciduous shrub cover, grasslands, 

and agricultural lands are difficult to analyze because the 1987 

image was taken in autumn and the 2009 image was taken 

in summer. The difference in seasons of the two images may 

influence the LULC classifications, with deciduous plants 

looking vastly different between the summer and autumn, 

herbaceous plants dying back at the end of the growing season, 

and crops drying and being harvested at various points in time. 

Furthermore, although it appears that a substantial decrease in 

the amount of agricultural lands and an increase in the amount 

of grasslands in the basin occurred, further investigation 

is necessary to make this determination. Pastureland also 

may have been classified as agriculture in some areas and 

as grassland in other areas. Although agriculture may have 

decreased in the basin, it is unlikely to have decreased to the 

extent shown by this analysis. 

This analysis highlighted major changes that occurred 

in the Chamokane Creek basin between 1987 and 2009, 

specifically regarding evergreen forest cover. The analysis also 

will provide more specific LULC data for the GSFLOW model 

compared to the generalized LULC products that currently 

are available. Additional studies would be needed to answer 

questions regarding changes in agriculture and specific crop 

types as well as changes in developed land area.
38 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washingtonwatac10-0434_fig.13 Modified from Landsat TM image, October 11, 1987 UTM11, WGS84, 30 meter resolution 48° 47° 50' 118° T. 30N. T. 29N. T. 28N. T. 27N. 117°45' R. 41 E. R. 40 E. R. 39 E. 118° T. 30N. T. 29N. T. 28N. T. 27N. 117°45' R. 41 E. R. 40 E. R. 39 E. 48° 47° 50' R. 38 E. R. 38 E.

0 5 10 MILES0 5 10 KILOMETERS

Evergreen forestOpen forestShrubGrasslandAgricultureDeveloped/sparsely vegetatedWater

Drainage basin boundary

EXPLANATION

Generalized land use-land cover classification, 2009

Evergreen forestOpen forestShrubGrasslandAgricultureDeveloped/sparsely vegetatedWater

Drainage basin boundary

EXPLANATION

Generalized land use-land cover classification, 1987

Modified from Landsat TM image, July 3, 2009UTM11, WGS84, 30 meter resolution

Ford

Springdale

Ford

Springdale

Figure 13. Generalized land use and land cover classifications, Chamokane Creek basin, Stevens County, Washington, 1987 and 2009.
Groundwater Pumpage and Use 39

Groundwater Pumpage and Use

Groundwater pumpage was estimated so water use within 

the basin could be estimated near the time of adjudication 

through present (2009) for permit exempt and non-exempt 

uses of groundwater. Annual groundwater pumpage estimates 

for 1980 through 2007 in the Chamokane Creek basin are 

shown in table 8.

The major uses of water in the Chamokane Creek 

basin are for domestic purposes (single-family drinking and 

household use, lawns, and small gardens), public water supply, 

fish-hatchery operations, irrigation, and commercial and 

industrial uses. Some surface water may be withdrawn from 

Chamokane Creek for these purposes, but the primary source 

of water is groundwater. Based on water rights on file with the 

State of Washington and reported by the Lower Spokane Basin 

Watershed Planning website, less than 100,000 gal/yr of water 

are removed from the creek (Tetra Tech/KLM, 2007, accessed 

March 23, 2009, at http://www.spokanecounty.org/wqmp/

project54/ASP/P2L1TechAssmnt_index.asp).

Annual groundwater pumpage in the Chamokane Creek 

basin was estimated and compared from 1980 through 2007 

for five major categories: self-supplied domestic, public water 

supply, aquaculture, irrigation, and commercial/industrial 

(table 8). Self-supplied domestic and public-supply estimates 

were based on U.S. Census Bureau population data and a 

per-person water use estimate derived from data presented in a 

report on the water resources of the Colville River Watershed 

(Kahle and others, 2003). U.S. Census Bureau population 

data, in the form of a geographic information system (GIS) 

data layer, were obtained from the Washington State Office 

of Financial Management (accessed August 2007 at http://

www.ofm.wa.gov/pop/geographic/00tiger.asp). The data layer 

contained the distribution of population by census block, the 

smallest area for which the Census Bureau tabulates census 

data. Water use of 210 gal/d per person was computed from 

population and estimated water-use data compiled by the 

Water-Resource Inventory Area (WRIA) 59 Colville River 

Watershed Planning team (Kahle and others, 2003). The 

population and per-person water use data were combined to 

estimate domestic and public-supply water use in the study 

area. Pumpage estimates for the other uses were compiled 

from Spokane Tribal water managers, public-water system 

managers and records, agencies of the State of Washington 

(Departments of Health, Ecology, Fish and Wildlife, and 

Agriculture), and from private citizens. 

Annual groundwater pumpage values from 1980 through 

2007 for the study area range from 21.1 to 28.9 Mgal/yr for 

domestic wells and 0.38 to 23.7 Mgal/yr for public supply 

wells (table 8). A sharp increase in public-supply pumpage 

(from 0.38 Mgal in 1987 to 9.4 Mgal in 1988) reflects the 

addition of several public supply systems in the basin. 

Pumpage estimates for years after the 2000 census are based 

on Census Bureau interdecadal population estimates.

Population distribution during 2000 in the study area 

indicates that the highest concentration of people is in 

the areas west and south of Springdale, Wash. (fig. 14). 

Self‐supplied domestic well pumpage during 2000 reflects 

the population distribution with the highest annual pumpage 

west and south of Springdale (fig. 15). Service areas for the 

public‐supply wells were considered to be the quarter-quarter 

section in the legal description for the well. The distribution of 

public-supply pumpage also is presented in figure 15.

Groundwater pumpage for the hatcheries is presented 

in table 8. The combined total of water pumped for the two 

hatcheries for aquaculture for 2007 was about 1.15 billion 

gallons. Ground-water pumpage by the hatcheries increased 

by about a factor of 5 from 1997 to 2007 as the Tribal hatchery 

increased usage in 2003 and with the drilling of a production 

well and subsequent use of groundwater at the WDFW 

hatchery in 2005. No pre-adjudication pumpage estimates for 

aquaculture were computed because the Tribal hatchery and 

the WDFW hatchery relied on spring water until 1990 and 

2005, respectively.

Little commercial or industrial activity currently (2009) 

occurs in the study area. Excluding the water used by the Ford 

Trading Post, which is included in the public-supply estimate, 

the only other commercial/industrial user is the Dawn Mining 

Company millsite at Ford, Wash. From 1970 to 1982, the mill 

used about 105 Mgal of water per year for ore processing. 

From 1983 through 1991, mining and milling operations were 

suspended and an unknown, but small, amount of water was 

used. The mill was re-opened in 1992 to process sludge from a 

water-treatment plant at the mine site and water use was about 

0.34 Mgal/yr. Sludge processing continued intermittently until 

2001. From 2001 through 2007, continuous maintenance at the 

mill used about 26.3 Mgal/yr. Some return flow to Chamokane 

Creek resulted from the maintenance operations, but the 

amount is unknown (Robert Nelson, Dawn Mining Company, 

oral commun., 2010). 

Of about 4,400 acres of land within the study area 

classified as agricultural land, only about 160 acres was 

irrigated with groundwater in 2007. In 1987, the first year 

when reliable agricultural acreage was calculated, the area 

irrigated was about 150 acres. Water use by crop type was 

obtained from the AgriMet station maintained by the Bureau 

of Reclamation in the study area (Bureau of Reclamation, 

AgriMet, accessed October 14, 2009, at http://www.usbr.

gov/pn/agrimet/wa_charts.html). The area and location of 

each crop type were obtained from GIS data layers that were 

derived from satellite imagery of the study area (see Land use 

and land cover change analysis and appendix A). The amount 

of water used by each crop type and the acreage of each crop 

type were combined to compute agricultural water use. 
40 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington Table 8. Annual groundwater pumpage for Chamokane Creek basin, Stevens County, Washington. [Pumpage is in millions of gallons; E, estimated value; –, data not available] 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 Domestic 21.1 21.2 21.4 21.5 21.7 21.6 21.2 21.1 20.7 20.4 20.2 20.5 21.4 22.0 Public supply 0.38 0.38 0.38 0.38 0.38 0.38 0.38 0.38 9.4 9.8 11.0 11.6 12.1 12.9 Aquaculture

–

–

–

–

–

–

–

–

–

– 191 192 192 192

Commercial/Industrial 105 105 105

–

–

–

–

–

–

–

–

– 0.34 0.34

Agriculture 98E 98E 98E 98E 98E 98E 98E 97.9 98.1 98.3 98.5 98.7 98.9 99.1Total annual pumpage 224 225 225 120 120 120 120 119 128 128 321 323 325 326

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Average 

annual 

pumpage

Domestic 23.1 24.2 25.2 26.3 26.6 27.0 28.4 28.2 27.9 27.7 27.4 27.5 28.2 28.9 24.0

Public supply 13.5 14.1 14.9 15.5 16.1 16.8 17.6 18.3 19.1 19.9 20.9 21.7 22.7 23.7 11.6Aquaculture 192 192 192 220 250 250 250 250 250 630 885 956 1,060 1,150 416Commercial/Industrial 0.34 0.34 0.34 0.34 0.34 0.34 0.34 26.3 26.3 26.3 26.3 26.3 26.3 26.3 26Agriculture 99.3 99.5 99.7 99.9 100 100 100 101 101 102 102 102 103 103 100Total annual pumpage 328 330 332 362 393 394 396 424 424 806 1,060 1,130 1,240 1,330 420
Groundwater Pumpage and Use 41

watac10-0434_fig 14

EXPLANATION

Population per census

 block in 2000

 

Drainage basin

 boundary

0 to 4

5 to 15

16 to 35

36 to 60

61 to 132

48°

47°

50'

118°

T.

30

N.

T.

29

N.

T.

28

N.

T.

27

N.

117°45'

R. 38 E. R. 39 E. R. 40 E.

Washington State Office of Financial Management,

Census TIGER/Line File Extracts, 2000, accessed August 2007 at

http://www.ofm.wa.gov/pop/geographic/00tiger.asp

0 5 10 MILES

0 5 10 KILOMETERS

R. 41 E.

Ford

Springdale

Figure 14. Distribution of Census blocks and 2000 population, Chamokane Creek basin, Stevens County, Washington. Census 

blocks were obtained from Washington State Office of Financial Management, Census TIGER/Line File Extracts, 2000, accessed 

August 2007 at http://www.ofm.wa.gov/pop/geographic/00tiger.asp.
42 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

Figure 15. Distribution of estimated pumpage in 2000 for self-supplied domestic use and public supply, Chamokane Creek 

basin, Stevens County, Washington.

watac10-0434_fig 15

N. Fk. Chamokane Creek

S. Fk. Chamokane Creek

Middle Fork

Little Chamokane

Creek

Wellpinit Creek

Cham

okane

Creek

Deer Creek

Colville

River

Grouse Cr.

Spokane

River

Sheep Creek

Long Lake

48°

47°

50'

118°

T.

30

N.

T.

29

N.

T.

28

N.

T.

27

N.

117°45'

R. 38 E. R. 39 E. R. 40 E. R. 41 E.

Washington State Office of Financial Management,

Census TIGER/Line File Extracts, 2000, accessed August 2007 at

http://www.ofm.wa.gov/pop/geographic/00tiger.asp

0 5 10 MILES

0 5 10 KILOMETERS

Spokane Indian Reser va t ion

Ford

Springdale

WALKERS 

PRAIRIE

HUCKLEBERRY MOUNTAINS

CHAMOKANE

VALLEY

CAMAS VALLEY

EXPLANATION

Estimated pumpage in 2000,

 in millions of gallons

 

Drainage basin boundary

Less than 0.500

0.501 to 1.000

1.001 to 2.000

2.001 to 3.000

3.001 to 5.000

5.001 to 13.000

Less than 0.230

0.231 to 0.380

0.381 to 0.770

0.771 to 3.340

3.341 to 12.300

Self-supplied domestic use

Public supply
Data Needs 43

In 1987, about 97.9 Mgal of groundwater was pumped 

to irrigate crops in the study area. In 2007, about 103 Mgal 

of groundwater was pumped. Estimates of agricultural land 

were not determined for years between 1987 and 2007, 

however, assuming that the amount of irrigated agricultural 

land from 1987 to 2007 increased uniformly from 150 acres 

(the 1987 value) to 160 acres (the 2007 value), estimates of 

pumpage for agricultural use can be computed using the same 

rate of change, about 5 percent per year. Pumpage from 1987 

to 2007 pumpage then was estimated to increase by about 

0.2 Mgal/yr. Due to a lack of agricultural acrage data prior 

to 1987, an estimate of 98 Mgal/yr was used for 1980–86 

(table 8).

Basin Water Budget

On a long-term basis, a hydrologic system is usually in 

a state of dynamic equilibrium; that is, inflow to the system 

is equal to outflow from the system and there is little or no 

change in the quantity of water stored within the system. 

Based on long-term groundwater levels shown in figure 11, 

this appears to be the case for the Chamokane Creek basin 

where long-term mining or mounding of the aquifer system 

is not apparent. An estimated water budget, or distribution of 

precipitation, for a typical year in the Chamokane Creek basin 

includes estimates of component values, and illustrates the 

fate of precipitation (inflow) by approximating the distribution 

of water in the hydrologic system of the basin: precipitation 

(inflow) and evapotranspiration, streamflow, and groundwater 

discharge (outflow). It is assumed that, in the long term, inflow 

to the basin equals outflow and little or no change is expected 

in the amount of water stored within the basin. This relation is 

shown as:

Precipitation Evapotranspiration 

 Streamflow at outlet 

 Groundwater discharge at outlet; and 

for the study area :

=

+

+

(4)

19.6 in. = 14.9 in. + 4.7 in. + 0 in. (5)

Equation 4 shows the water-budget components and 

equation 5 shows the estimated value for each component, in 

inches, derived for the study area. 

A statistical-topographic model for mapping 

climatological precipitation over mountainous terrain, 

PRISM (Daly and others, 1994), was used to derive an 

area‐weighted average precipitation of 19.6 in. for the 

Chamokane Creek basin. The distribution of average annual 

precipitation (1971–2000) for the basin, contoured using data 

from NOAA weather stations and USDA-Natural Resource 

Conservation Service snow-measurement stations, is shown in 

figure 2. Averaging the ranges of precipitation over the basin 

yielded the area-weighted average of 19.6 in. Discharge from 

Chamokane Creek near the outlet of the basin (4.7 in.) was 

based on the long-term average flow (62.5 ft3/s) at gaging 

station 12433200 for the 28 years when a complete record was 

available (1972–78 and 1988–2008). Groundwater discharge 

near the outlet of the basin is assumed to be zero. The value 

for evapotranspiration (14.9 in.) is a residual; that is, it 

represents the quantity that remains after Chamokane Creek 

discharge is subtracted from precipitation. 

The predominant fate of precipitation in the basin 

(76 percent) is loss from the basin through evapotranspiration, 

a combination of evaporation from open bodies of water, 

evaporation from soil surfaces, and transpiration from the 

soil by plants. Evapotranspiration commonly accounts for the 

greatest loss from basins with similar hydrologic conditions. 

For comparison, evapotranspiration losses were 78 percent 

of precipitation in the Colville River basin (Ely and Kahle, 

2004).

Streamflow leaving the basin, as measured downstream 

of Chamokane Falls, is 24 percent of precipitation. Total 

groundwater use for 2007, is an estimated 1,330 Mgal/

yr (table 8). Of that total, 1,150 Mgal/yr is pumped for the 

fish hatcheries, and nearly all of that gets discharged to 

Chamokane Creek and ‘counted’ as streamflow past the gage. 

Therefore, actual groundwater use in the basin (2007) is 

approximately 180 Mgal/yr, or only about .3 percent of total 

precipitation. This simple comparison indicates that actual 

groundwater use is relatively small when compared to total 

precipitation.

Data Needs

Additional information about the thickness of the Lower 

aquifer is needed to understand better the deepest parts of 

the groundwater system in the Chamokane Creek basin. The 

thickness of the Lower aquifer could be better determined by 

drilling into underlying basalt or older bedrock. Deep drilling 

at several locations along the axis of the Chamokane Valley 

from the Swamp Creek area to near Ford would provide these 

two important pieces of information. 

Independent data on return flows or consumptive use 

of pumpage would be helpful to gain a more complete 

understanding of water use within the basin. Although the 

GSFLOW model being used in Phase 2 of this study may 

provide some insights, independent data would provide a more 

complete understanding of water use. The greatest pumpage 

in the basin is associated with activities such as aquaculture 

and in the past, industry, that tend to have significant return 

flows. Data on domestic consumptive use or septic returns also 

would be helpful to better quantify timing and magnitude of 

effects on streamflow.
44 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

A water budget for the groundwater system is more 

difficult to estimate than the basin water budget because of 

limited knowledge of component values. During Phase 2 

of this study, the GSFLOW model will be used to provide 

estimates of recharge to the groundwater system as well as 

a comprehensive water budget. The calibrated model will 

provide a more refined depiction of the groundwater and 

surface-water flow system where current observational data 

are lacking. 

Summary

Chamokane Creek basin is a 179 mi2 area that borders 

and partially overlaps the Spokane Indian Reservation in 

southern Stevens County in northeastern Washington State. 

Aquifers in the Chamokane Creek basin are part of a sequence 

of glaciofluvial and glaciolacustrine sediment that may 

reach a total thickness of about 600 ft. In 1979, most of the 

water rights in the Chamokane Creek basin were adjudicated 

by the United States District Court requiring regulation in 

favor of the Spokane Tribe of Indian’s senior water right. A 

court-appointed Water Master regulates junior water rights 

when the mean daily 7-day low flow becomes less than 

24 ft3/s (27 ft3/s for rights issued after December 1988) at 

Chamokane Falls, as recorded at U.S. Geological Survey 

(USGS) streamflow‐gaging station 12433200; regulation 

has been necessary in 3 recent years (2001, 2005, and 2008). 

Additionally, the non-Reservation areas of the basin are closed 

to additional groundwater or surface-water appropriations, 

with the exception of permit exempt uses of groundwater. 

Data from 158 wells were used to characterize the 

hydrogeologic framework and analyze the direction of 

groundwater movement in the Chamokane Creek basin. 

Water levels were measured in wells during three study 

periods: autumn 2007, spring 2008, and late summer 2008. 

Additionally, a monthly water-level network of 25 wells 

was monitored from March 2008 through December 2009. 

Six wells in the monthly network were instrumented 

with transducers for the collection of hourly water-level 

measurements.

Six hydrogeologic units described in this report include 

the Upper outwash aquifer, the Landslide unit, the Valley 

confining unit, the Lower aquifer, the Basalt unit and the 

Bedrock unit. The Upper outwash aquifer is an unconfined 

aquifer that occurs along the valley floors of the study area. 

It consists of sand, gravel, cobbles, and boulders, with 

minor silt and (or) clay interbeds in places. Thickness of 

the aquifer ranges from less than 50 ft along the margins of 

the unit to more than 150 ft where the unit is comprised of 

glacial terraces. The Landslide unit is composed of poorly 

sorted deposits of broken basalt and sedimentary interbeds 

along the basalt bluffs bounding Walkers Prairie. The Valley 

confining unit is a mostly low-permeability unit consisting of 

glaciolacustrine silt and clay that occurs at depth throughout 

the valley bottoms of the study area and extends northward 

into the Colville Valley. The thickness of the Valley confining 

unit commonly is 150–300 ft. The Lower aquifer is a confined 

aquifer consisting of sand and gravel that occurs at depth 

below the Valley confining unit; it too extends northward 

into the Colville Valley. Thickness of the unit is not well 

known throughout its extent, but thicknesses of two wells 

that fully penetrated the unit were 125 and 138 ft. The Basalt 

unit is composed of Columbia River Basalt and sedimentary 

interbeds. Water is contained in cracks and fractures and from 

zones between lava flows. The Bedrock unit includes rocks 

older than the Columbia River Basalt and commonly includes 

granite and quartzite with small and often unreliable yields. 

Median horizontal hydraulic conductivity values for the Upper 

outwash aquifer, Valley confining unit, Lower aquifer, and 

Basalt unit were estimated to be 540, 10, 19, and 3.7 ft/d, 

respectively. 

Horizontal groundwater flow in the Upper outwash 

aquifer moves from the topographically high tributary-basin 

areas toward the topographically lower valley floors. Waterlevel altitudes in the Upper outwash aquifer range from 

2,150 ft in the Camas Valley to 1,760 ft near Ford. The general 

distribution of horizontal gradients was about 13–50 ft/mi in 

the Camas Valley, about 80 ft/mi where Chamokane Creek 

exits Icebox Canyon to near its confluence with Swamp Creek, 

20–30 ft/mi from south of Springdale through the Swamp 

Creek area, and 12–16 ft/mi along Walkers Prairie. The 

smallest gradient in the Upper outwash aquifer, about 12 ft/mi, 

was along Walkers Prairie. 

Horizontal groundwater flow in the Lower aquifer is 

south to southwest from near Springdale to south of Ford. 

In the Camas Valley, horizontal groundwater flow is east to 

near the end of the valley where flow likely discharges into 

overlying sediments and Chamokane Creek near the end of the 

valley at the head of Icebox Canyon. Along the Chamokane 

Valley floor, water-level altitudes within the Lower aquifer 

range from 1,885 ft near Swamp Creek to 1,600 ft near 

the lower end of the basin. Horizontal gradients are about 

20 ft/mi along Walkers Prairie, but become much greater and 

range from 80 to 200 ft/mi from near Ford to the southern 

extent of the Lower aquifer. In Camas Valley, water-level 

altitudes within the Lower aquifer range from about 2,150 to 

less than 2,050 ft. The horizontal gradient in Camas Valley is 

about 100 ft/mi. 

Paired hydrographs for closely spaced wells completed 

in the Upper outwash aquifer and the Lower aquifer indicate 

a nearly identical timing of the seasonal rise and falls in 

water levels with similar, but slightly greater magnitude in 

the fluctuations in the Upper outwash aquifer. The overall 

similarity of fluctuations in water levels indicates that these 

systems may be fairly well connected. 
References Cited 45

Three sets of synoptic discharge measurements were 

made at 28 sites along Chamokane Creek and its tributaries 

during this study to identify gaining and losing reaches 

during high- and low-flow conditions. Two sets of low-flow 

measurements were made at these sites in late September‐early 

October 2007 and in August 2008. One set of high-flow 

measurements was made in mid-April 2008. During the 

low-flow measurements many sites were at or near zero 

flow. Exceptions to this include stream sections supported by 

spring flow, most notably downstream of Ford where large 

springs discharge from the Upper outwash aquifer. During 

the high‐flow measurements, gains in streamflow occurred 

throughout the Camas Valley with the largest high‐flow 

measurement (522 ft3/s) made at the mouth of Ice Box 

Canyon. Downstream of Camas Valley, large streamflow 

losses were recorded that indicate that Chamokane Creek loses 

flow directly to the Upper outwash aquifer near the north end 

of Walkers Prairie. 

A land use and land cover change analysis indicates 

that Chamokane Creek basin currently (2009) is an area 

dominated by forests with some pasture and agricultural 

lands. Development is relatively sparse. Loss in forest cover 

represents the largest change in land cover in the basin 

between 1987 and 2009. This appears to be mostly due to 

forestry activities, especially in the northern part of the basin. 

Since 1987, more than 18,000 acres of evergreen forest have 

been logged and are at various stages of regrowth.

Estimated average annual total groundwater pumpage 

in the basin increased from 224 Mgal/yr in 1980 to 

1,330 Mgal/yr in 2007. In 2007, the largest withdrawals were 

to supply two fish hatcheries, with a combined total annual 

pumpage of about 1,150 Mgal. Annual groundwater pumpage 

values from 1980 through 2007 for the study area range 

from 21.1 to 28.9 Mgal/yr for domestic wells and 0.38 to 

23.7 Mgal/yr for public supply. 

An approximate water budget, or distribution of 

precipitation, for a typical year in the Chamokane Creek 

basin shows that 19.6 in. of precipitation are balanced by 

4.7 in. of streamflow discharge from the basin, and 14.9 in. of 

evapotranspiration.

Acknowledgments

The authors of this report gratefully acknowledge the 

landowners who shared their knowledge and concerns about 

water-resources in the Chamokane Creek basin and allowed 

access to their property for data collection. Without their 

consent, it would have been impossible to collect most of 

the data required for this study. Steven Andrews, former 

Spokane Tribe Utilities manager, provided information 

concerning tribal public supply wells. Lam Chan, GIS 

Manager for the Spokane Tribe, provided digital data sets. 

Brian Crossley, Spokane Tribe Natural Resources, responded 

to numerous inquiries for data, references, and contact 

information pertaining to water-resources on the Spokane 

Reservation. Charlie Kessler, Stevens County Conservation 

District, provided insights on the surface-water system of the 

basin as well as detailed information collected as part of his 

Chamokane Creek Watershed Management work. Eugene 

Kiver, Eastern Washington University (retired), loaned 

original field maps of surficial geology for the Ford and Tum 

Tum 7 1⁄2-minute quadrangles. Miles Logsdon, University of 

Washington, provided guidance and technical support on the 

land use classification and change analysis process. James 

Lylera, Chamokane Creek Water Master, provided long-term 

water-level data and water-use information for the basin. 

William Matt, Sr., Spokane Tribe Natural Resources, provided 

assistance in locating wells on the Reservation. Robert Nelson, 

Dawn Mining Company, provided water-use data for the 

Ford mill. Tim Peone and Ace Trump provided water-use 

information for the Tribal and Washington Department of 

Fish and Wildlife fish hatcheries, respectively. Donna Smith, 

Bureau of Indian Affairs, provided information on wells and 

population estimates for the Reservation.

References Cited

Allen, J.E., and Burns, Marjorie, 1986, Cataclysms on the 

Columbia: Portland, Oregon, Timber Press, Inc., 213 p.

Atwater, B.F., 1986, Pleistocene glacial-lake deposits of 

the Sanpoil River Valley, northeastern Washington: U.S. 

Geological Survey Bulletin 1661, 39 p.

Bear, Jacob, 1979, Hydraulics of groundwater: New York, 

McGraw-Hill, 569 p.

Buchanan, J.P., Wozniewicz, J.V., and Lambeth, R.H., 1988, 

Hydrogeology of the Chamokane Valley aquifer system: 

Upper Columbia United Tribes Fisheries Center, Eastern 

Washington University, Fisheries Technical Report No. 20, 

69 p.

Bureau of Reclamation, 2009, AgriMet, The Pacific Northwest 

Cooperative Agricultural Weather Network: Bureau of 

Reclamation website accessed October 14, 2009, at http://

www.usbr.gov/pn/agrimet/wa_charts.html.

Carnahan, B., Luther, H.A., and Wilkes, J.O., 1969, Applied 

numerical methods: New York, John Wiley and Sons, Inc., 

604 p.

Carrara, P.E., Kiver, E.P., and Stradling, D.F., 1995, Surficial 

geologic map of the Chewelah 30’ × 60’ quadrangle, 

Washington and Idaho: U.S. Geological Survey 

Miscellaneous Investigations Series Map I-2472, 1 sheet, 

scale 1:100,000. 
46 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

Carrara, P.E., Kiver, E.P., and Stradling, D.F., 1996, The 

southern limit of Cordilleran ice in the Colville and Pend 

Oreille valleys of northeastern Washington during the late 

Wisconsin glaciation: Canadian Journal of Earth Sciences, 

v. 33, no. 5, p. 769–778. 

Daly, Chris, Neilson, R.P., and Phillips, D.L., 1994, A 

statistical-topographic model for mapping climatological 

precipitation over mountainous terrain: Journal of Applied 

Meteorology, v. 33, p. 140-158. 

Drost, B.W., comp., 2005, Quality-assurance plan for groundwater activities, U.S. Geological Survey, Washington 

Water Science Center: U.S. Geological Survey Open-File 

Report 20051126, 27 p. (Available at http://pubs.usgs.gov/

of/2005/1126/.)

Ely, D.M., and Kahle, S.C., 2004, Conceptual model and 

numerical simulation of the ground-water flow system in the 

unconsolidated deposits of the Colville River Watershed, 

Stevens County, Washington: U.S. Geological Survey 

Scientific Investigations Report 2004-5237, 72 p.

Embrey, S.S., Hansen, A.J., and Cline, D.R., 1997, Groundwater resources of three areas on the Spokane and Kalispel 

Indian Reservations, northeastern Washington: U.S. 

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Appendix A 49

A land use and land cover (LULC) change analysis was 

done to supplement the understanding of the groundwater and 

surface-water system of the Chamokane Creek basin. Changes 

in land use and land cover can result in changes in recharge to 

the groundwater system and changes in how water is used in 

the basin. The term land cover refers to the physical attributes 

present on the surface of the Earth, and the term land use

describes how a specific piece of land is used by humans 

(Lillesand and others, 2008). For some classes, these concepts 

are directly related. LULC change in the Chamokane Creek 

basin was assessed using satellite imagery. 

Satellite images commonly are used to analyze LULC 

changes because they can provide extensive information for a 

specific period in a cost-effective method (Güler and others, 

2007). Furthermore, satellites provide global and frequent 

coverage of the Earth and the data are readily accessible 

online. Images often are available in user-ready digital 

formats, which allow for quick access to time series data. 

Although LULC data covering the Chamokane Creek 

basin study area are available (for example, Landscape Fire 

and Resource Management Planning Tools Project and the 

National Land Cover Database (Multi-Resolution Land 

Characteristics Consortium, 2008)), these generalized, national 

land cover products provide data only for select periods 

and usually are limited to recent years. It was not possible, 

therefore, to use currently available classification products for 

the LULC change analysis. Classifications specific to, or close 

to, the dates of interest (prior to the 1979 Adjudication and 

current (2009)) were needed. Furthermore, the classifications 

done specifically for this study are at a finer resolution than 

many of the National land cover products.

Methods

Data Acquisition

Landsat Thematic Mapper (TM) data were used for 

this study due to the availability of historical and continuous 

imagery. TM sensors on Landsat satellites have been 

collecting data since 1982. The TM sensor collects data in 

seven wavelength bands (six in the visible through midinfrared regions of the electromagnetic spectrum and one 

thermal band) (Lillesand and others, 2008). TM data have a 

pixel size of 30 m (120 m for the thermal band). Landsat TM 

data were acquired from the U.S. Geological Survey Earth 

Resources Observation and Science Center (EROS, http://

glovis.usgs.gov/). 

The Chamokane Creek basin study area is in path 43 and 

row 27 of the Worldwide Reference System-2, a cataloging 

system for Landsat data (fig. A1). The final dates selected for 

the LULC change analysis were October 11, 1987, and July 3, 

2009. Landsat TM data from EROS generally is available for 

this location every 16 days. Some images were unusable due 

to heavy cloud cover. High quality images with minimal cloud 

cover were not available until July 1984. Orthophotos for 

the entire Chamokane Creek basin, however, were available 

starting in 1987. Orthophotos are aerial photographs that have 

been georectified and do not contain the distortions present 

in normal aerial photographs. Therefore, distances, angles, 

and areas may be measured directly from the photographs 

(Lillesand and others, 2008). Orthophotos of the study area 

were needed to conduct an accuracy assessment of the 1987 

LULC classification. Although using data from the same 

season is often desirable in a LULC change analysis, high 

quality satellite images were not available until October 1987. 

Data prior to adjudication (1979) would have been ideal 

for this analysis. However, the only satellite sensor dating 

back far enough is the Multispectral Scanner (MSS). Although 

MSS data are available as of 1972, images are of relatively 

low resolution (80 m) and are available only until 1992. 

Image Classification and Change Analysis

A common approach to analyzing LULC data is to 

independently classify images from different periods and 

compare the images after classification to determine where 

changes on the landscape have occurred (Güler and others, 

2006; Muñoz-Villers and López-Blanco, 2008). 

To classify LULC for the historical (1987) and current 

(2009) images, a hybrid approach to image classification 

using ERDAS IMAGINE software was used. The hybrid 

approach incorporates two types of classifications: (1) 

unsupervised classification (program groups together pixels 

that are spectrally similar without any input from the user) 

and (2) supervised classification (user inputs a spectral 

signature file that the program uses to classify pixels). Prior to 

classification, selected images for each date were preprocessed 

by EROS with the Standard Terrain Correction (Level 1T), 

which provides systematic radiometric as well as geometric 

accuracy using ground control points and a DEM (U.S. 

Geological Survey, 2009). 

Appendix A. Land Use and Land Cover Change Analysis
50 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

Figure A1. Landsat Thematic Mapper image, July 3, 2009, (path 43, row 27), Chamokane Creek basin, Stevens County, Washington.

watac10-0434_fig A1

Satellite image in 2009

EXPLANATION

RGB

Red: Band_4

Green: Band_2

Blue: Band_1 0 10 20 30 40 50 60 70 KILOMETERS

0 10 20 30 40 50 60 70 MILES

WASHINGTON

Chamokane

Creek basin

IDAHO MONTANA

119° 118° 117° 116°

48°

47°

Path 43

Row 26

Row 27

Path 44

Landsat TM image, July 3, 2009
Appendix A 51

Landsat TM data for the two dates were independently 

classified. For each image, three main “image blocks” were 

created to represent the three major thematic materials in the 

scene; this method best captures the spectral variation within 

each theme. In this case, the selected themes were “forest,” 

“agriculture,” and “developed.” Using an unsupervised 

classification, the program sorts pixels into a specific number 

of clusters based on their spectral signatures. The algorithm 

determines a mean signature for each cluster. Each cluster 

class is given a name based on reflectance values, known 

features, and other external information. These names and 

their corresponding signatures then were saved in a signature 

file. An unsupervised classification was carried out for each 

image block.

If more accurate data regarding land cover were 

available, these data were used to create training areas to 

assign a spectral signature to a known land cover type in 

the image. Supervised training areas were created from 

pixels of obvious or known features such as roads, water, 

and forest, from training data collected in the field, or from 

outside information such as the Washington State Department 

of Agriculture Crop Geodatabases. For each image block 

previously mentioned, the signature file from the unsupervised 

classification was edited to include spectral signatures of these 

known surface materials.

Once a spectral signature file for each image block 

was edited, all three image block files were merged into 

one master signature file. This file then was used to do a 

supervised classification on the entire image. In the supervised 

classification, each pixel was assigned to one of the signatures 

from the master signature file based on a maximum likelihood 

classifier algorithm. The classified images were smoothed with 

a majority filter using a 3×3 pixel moving window to reduce 

the number of misclassified pixels (Lillesand and others, 

2008).

Once both images were classified, a pixel-by-pixel 

overlay procedure (Muñoz-Villers and López-Blanco, 2008) 

was carried out using ArcGIS to examine changes between the 

1987 and 2009 LULC. A change map was created to examine 

the nature of the changes that occurred during this period. 

Accuracy Assessment

To assess the accuracy of the 1987 classified image, 

250 reference points were selected from historical 1987 

orthophotos at a scale of 1:63,360 obtained from the 

Washington Department of Natural Resources. These points 

were selected based on a stratified random sampling design 

(except for water, which occurred only once in the classified 

image and, therefore, was only sampled once). To assess the 

accuracy of the 2009 classified image, 129 ground points 

in the study area were visited at the end of July 2009 (after 

the satellite image was taken). Due to limited access to 

privately‐owned lands, however, a random sampling method 

for selecting reference points was not possible for the 2009 

image. Instead, reference points were taken systematically 

(every few miles) along as many roads as possible throughout 

the basin. 

Classification accuracy was then evaluated using 

error matrices. The overall accuracy and the Khat statistic 

(KAPPA analysis) were computed to describe the accuracy 

of each classification. Differences in these two values were 

expected as the overall accuracy is simply the total number 

of correctly classified pixels divided by the total number of 

reference pixels, whereas the Khat statistic includes the errors 

of commission and omission, thereby indicating the extent 

to which the percentage of correct values in an error matrix 

are due to “true” versus “chance” agreement (Lillesand and 

others, 2008). The accuracies of users and producers also were 

calculated. User accuracy refers to the probability that a pixel 

is correctly classified by the user (or in historical orthophotos) 

and is a measure of commission error. Producer accuracy 

refers to the probability that reference pixels were correctly 

classified and is a measure of omission error. 

Results

Land Use and Land Cover Classes

Seven LULC classes were identified in the classification 

process. Many of the classifications used were based on 

categories from the National Land Cover Database.

Evergreen forest – Areas dominated by evergreen trees 

greater than 5 m tall.

Open forest – Areas of open, low-density evergreen trees 

greater than 5 m tall. These areas may be naturally open 

ponderosa pine forests or low-density forests resulting 

from harvesting activities. 

Shrub – Areas dominated by shrubs less than 5 m tall. 

Includes true shrubs as well as young trees in an early 

successional stage. 

Grassland – Areas covered by grasses and other 

herbaceous vegetation. These areas are not subject to 

intensive management activities, but may be used for 

grazing. 

Agriculture – Land that is used for the production of 

crops and is being actively tilled. Also includes pastures 

planted for livestock grazing. 

Developed/Sparsely vegetated – Areas where there 

is little vegetation due to the presence of constructed 

materials, impervious surfaces, bare/barren land or 

clearcuts. 

Water – Areas of open water. 
52 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

Accuracy of Multispectral Analysis

The 1987 LULC map (fig. A2) has an overall accuracy 

of 86.5 percent and a Kappa index of agreement of 0.83. 

The error matrix containing user and producer accuracies for 

1987 is shown in table A1. The accuracy of producers was 

greater than 80 percent for all classes except “developed/

sparsely vegetated.” Only 63.0 percent of areas that are 

developed/sparsely vegetated were correctly identified. 

However, 85.0 percent of areas classified as developed/

sparsely vegetated were in this class. It appears that some 

developed/sparsely vegetated areas were classified incorrectly 

as either grassland or agriculture. The accuracy of users was 

greater than 80 percent for all classes except “open forest” and 

“grassland.” Although 90.6 percent of areas with open forest 

cover were correctly identified by producers as open forest, 

only 78.4 percent of areas classified by users as open forest 

actually were in that category. Some areas with evergreen 

forest cover, shrub cover, or grassland cover were classified 

as open forest. Similarly, although 81.3 percent of grasslands 

were correctly identified by producers, only 66.7 percent of 

areas classified by users as grasslands are actually in that 

category. This is mainly because developed/sparsely vegetated 

areas were misclassified as grassland. Some agricultural and 

open forest areas also were misclassified as grassland. 

The 2009 LULC map (fig. A3) has an overall accuracy 

of 90.7 percent with a Kappa index of agreement of 0.89. The 

accuracy was greater than 80 percent for all classes except 

developed/sparsely vegetated (table A2). Only 73.3 percent of 

developed/sparsely vegetated areas were correctly identified 

by producers . However, 84.6 percent of areas identified as 

developed/sparsely vegetated by users actually were in this 

class. Some developed/sparsely vegetated areas are being 

classified incorrectly as agriculture or water. The accuracy of 

the users was greater than 80 percent for all classes except 

open forest and water. Although 100 percent of areas with 

open forest cover were correctly identified as such, only 

78.9 percent of areas classified as open forest were actually 

in that category. Areas covered in shrubs, grassland, or 

agriculture also were included in the open forest category. 

Land Use and Land Cover Change Analysis

Forest cover is the dominant land cover type in the 

Chamokane Creek basin. The area distribution for classes in 

1987 and 2009 as well as the change in area of each class is 

presented in table A3. Areas that have changed in classification 

during this period and which classifications they changed to 

are shown in figures A4 and A5.

In 1987, evergreen forests covered 65.4 percent of 

the area in the basin. This does not include ponderosa pine 

forests, however, which are in the southern part of the basin. 

Ponderosa pine forests are naturally open, park-like forests 

that are spectrally similar to forests with a low density of 

trees from logging activities. Therefore, these two forest types 

were identified as a single class “open forest.” It is reasonable 

to assume that areas classified as “open forest” in the upper 

part of the basin are due to logging activities, whereas areas 

classified as “open forest” in the lower part of the basin are 

naturally open ponderosa pine forests. In 2009, evergreen 

forest covered 55.9 percent of the basin. Once again, this 

does not include ponderosa pine forests and likely is an 

underestimate of total natural forest cover in the basin. 

Between 1987 and 2009, evergreen forest cover 

decreased by nearly 11,000 acres, or 14.5 percent of the 

original forest cover. Much of this decrease was a result of 

a change in classification of 9,800 acres of evergreen forest 

to open forest. Additionally, 5,300 acres of evergreen forest 

became shrub, 2,300 acres became grassland and 1,300 acres 

became developed/sparsely vegetated. Major changes in land 

cover to the evergreen forest category include 1,800 acres 

of grassland, 4,900 acres of shrub, and 740 acres of open 

forest. Therefore, net changes of evergreen forest to shrub and 

evergreen forest to grassland were relatively small (less than 

about 500 acres). 

Open forest cover increased from 6.97 to 17.4 percent of 

the total basin area (an increase of more than 12,000 acres). 

Other major changes include about 1,800 acres of grassland, 

1,600 acres of shrub, and 1,800 acres of agriculture becoming 

open forest in 2009. About 1,800 acres of open forest changed 

in classification to grassland so the net change between open 

forest and grassland was minor. About 740 acres of open forest 

changed to evergreen forest. 

Although the overall area of shrub cover has remained 

relatively stable (about 8 percent of total land area), various 

spatial changes from and to this category occurred. About 

4,900 acres changed in classification from shrub to evergreen 

forest, 1,600 acres changed from shrub to open forest, and 

1,100 acres changed from shrub to grassland. Additionally, 

about 5,300 acres changed from evergreen forest to shrub and 

1,000 acres changed from agriculture to shrub. 

Between 1987 and 2009, areas classified as grassland 

increased from 6.56 percent of the total basin area (about 

7,600 acres) to 10.3 percent (about 12,000 acres). The greatest 

change in this category came from 3,900 acres of agriculture 

becoming grassland, in addition to the changes to grassland 

mentioned previously. This change from agriculture to 

grassland has largely effected the total amount of agriculture 

in the basin, which has decreased by approximately one-half, 

from 10.9 to 5.3 percent of the total basin area. Changes in 

classification from agriculture to shrub and open forest also 

have noticeably decreased the amount of land classified as 

agriculture.

Developed/sparsely vegetated areas make up a small 

percentage of the total basin. Only 1.71 percent of the 

total basin area (almost 2,000 acres) was classified under 

this category in 1987, increasing to 2.8 percent (almost 

3,300 acres) in 2009. This increase came from areas 

previously classified as evergreen forest. Finally, areas 

classified as water increased by a magnitude of 10, although 

water was less than 0.5 percent of the total basin area.
Appendix A 53

watac10-0434_fig A2

Modified from Landsat TM image, October 11, 1987

UTM11, WGS84, 30 meter resolution

48°

47°

50'

118°

T.

30

N.

T.

29

N.

T.

28

N.

T.

27

N.

117°45'

R. 38 E. R. 39 E. R. 40 E. R. 41 E.

0 5 10 MILES

0 5 10 KILOMETERS

Open forest

 

Water

 

Grassland

 

Evergreen forest

 

Developed/sparsely vegetated

 

Agriculture

 

Shrub

Drainage basin boundary

EXPLANATION

Generalized land use-land cover

 classification, 1987

 

Springdale

N. Fk. Chamokane Creek

S. Fk. Chamokane Creek

Middle Fork

N. Fk. Chamokane Creek

Sw amp

Cr.

Sw amp

Cr.

S. Fk. Chamokane Creek

Middle Fork

Little

Chamokane Creek

Cha

m

okane

Creek

Deer Creek

Colville

Grouse Cr.

Spokane

River

Ford

Springdale

River

Figure A2. Map showing generalized land use and land cover classification for 1987, Chamokane Creek basin, Stevens 

County, Washington.
54 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

watac10-0434_fig. A3

118°

T.

30

N.

T.

29

N.

T.

28

N.

T.

27

N.

117°45'

R. 39 E. R. 40 E. R. 41 E.

48°

47°

50'

R. 38 E.

Modified from Landsat TM image, July 3, 2009

UTM11, WGS84, 30 meter resolution

Open forest

 

Water

 

Grassland

 

Evergreen forest

 

Developed/sparsely vegetated

 

Agriculture

 

Shrub

Drainage basin boundary

EXPLANATION

Generalized land use-land cover

 classification, 2009

 

0 5 10 MILES

0 5 10 KILOMETERS

Springdale

N. Fk. Chamokane Creek

S. Fk. Chamokane Creek

Middle Fork

N. Fk. Chamokane Creek

Sw amp

Cr.

Sw amp

Cr.

S. Fk. Chamokane Creek

Middle Fork

Little

Chamokane Creek

Cha

m

okane

Creek

Deer Creek

Colville

Grouse Cr.

Spokane

River

Ford

Springdale

River

Figure A3. Map showing generalized land use and land cover classification for 2009, Chamokane Creek basin, Stevens County, 

Washington.
Appendix A 55

Table A2. Error matrix for 2009 Landsat Thematic Mapper classified image of Chamokane Creek basin, Stevens County, Washington.

2009 Landsat TM 

classified data 

2009 Ground reference data

Evergreen 

forest

Open forest

Shrub

Grassland

AgricultureDeveloped/

sparsely 

vegetated

Water

Row total

User 

accuracy 

(percent)

Evergreen forest 26 26 100.0

Open forest 15 1 1 2 19 78.9

Shrub 10 10 100.0

Grassland 26 1 27 96.3

Agriculture 1 26 3 30 86.7

Developed/sparsely vegetated 1 1 11 13 84.6

Water 1 3 4 75.0

Column total 26 15 11 29 30 15 3 129

Producer's accuracy (percent) 100.0 100.0 90.9 89.7 86.7 73.3 100.0

Table A3. Comparison of acreages by class for land use and land cover classifications and change in acreage 

between 1987 and 2009, Chamokane Creek basin, Stevens County, Washington.

Class

1987 2009 1987–2009

Area Area Change in area

Acres Percent Acres Percent Acres

Evergreen forest 75,809.7 65.4 64,824.5 55.9 -10,985.2

Open forest 8,077.2 6.97 20,195.4 17.4 12,118.3

Shrub 9,738.9 8.41 9,317.7 8.0 -421.2

Grassland 7,601.9 6.56 11,948.2 10.3 4,346.3

Agriculture 12,631.8 10.9 6,115.9 5.3 -6,515.9

Developed/sparsely vegetated 1,986.4 1.71 3,281.4 2.8 1,295.0

Water 18.0 0.02 180.8 0.2 162.8

Total 115,863.9 100 115,863.9 100

Table A1. Error matrix for 1987 Landsat Thematic Mapper classified image of Chamokane Creek basin, Stevens County, Washington.

1987 Landsat TM 

classified data 

1987 Orthophoto reference data

Evergreen 

forest

Open forest

Shrub

Grassland

AgricultureDeveloped/

sparsely 

vegetated

Water

Row total

User 

accuracy 

(percent)

Evergreen forest 82 82 100.0

Open forest 4 29 2 2 37 78.4

Shrub 2 31 1 34 91.2

Grassland 3 1 26 3 6 39 66.7

Agriculture 1 2 31 4 38 81.6

Developed/sparsely vegetated 1 2 17 20 85.0

Water 1 1 100.0

Column total 89 32 34 32 36 27 1 251

Producer's accuracy (percent) 92.1 90.6 91.2 81.3 86.1 63.0 100.0
56    Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

watac10-0434_fig A4

R. 39 E. R. 40 E. R. 41 E.

48°

47°

50'

118°

T.

30

N.

T.

29

N.

T.

28

N.

T.

27

N.

117°45'

R. 38 E.

Open forest

 

Water

 

Grassland

 

Evergreen forest

 

Developed/sparsely vegetated

 

Agriculture

 

Shrub

Drainage basin boundary

Springdale

N. Fk. Chamokane Creek

S. Fk. Chamokane Creek

Middle Fork

N. Fk. Chamokane Creek

Sw amp

Cr.

Sw amp

Cr.

S. Fk. Chamokane Creek

Middle Fork

Little

Chamokane Creek

Cha

m

okane

Creek

Deer Creek

Colville

Grouse Cr.

Spokane

River

Ford

Springdale

River

EXPLANATION

Area of land use-land cover change

 (1987 to 2009), shown in 1987

 classifications 

 

No change

 

0 5 10 MILES

0 5 10 KILOMETERS

Modified from Landsat TM image, October 11, 1987

UTM11, WGS84, 30 meter resolution

Figure A4.  Map showing land use and land cover classification changes from 1987 to 2009, (1987 classifications that

changed), Chamokane Creek basin, Stevens County, Washington.
Appendix A    57

Figure A5.  Map showing land use and land cover classification changes from 1987 to 2009, (2009 area classifications that

changed), Chamokane Creek basin, Stevens County, Washington.

watac-0434_fig A5

Modified from Landsat TM image, July 3, 2009

UTM11, WGS84, 30 meter resolution

Open forest

 

Water

 

Grassland

 

Evergreen forest

 

Developed / sparsely vegetated

 

Agriculture

 

Shrub

Drainage basin boundary

Springdale

N. Fk. Chamokane Creek

S. Fk. Chamokane Creek

Middle Fork

N. Fk. Chamokane Creek

Sw amp

Cr.

Sw amp

Cr.

S. Fk. Chamokane Creek

Middle Fork

Little

Chamokane Creek

Cha

m

okane

Creek

Deer Creek

Colville

Grouse Cr.

Spokane

River

Ford

Springdale

River

EXPLANATION

No change

 

Area of land use-land cover change

 (1987 to 2009), shown in 2009

 classifications

0 5 10 MILES

0 5 10 KILOMETERS

48°

47°

50'

118°

T.

30

N.

T.

29

N.

T.

28

N.

T.

27

N.

117°45'

R. 38 E. R. 39 E. R. 40 E. R. 41 E.
58 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

Discussion

Chamokane Creek basin currently (2009) is an area 

dominated by forests with some pasture and agricultural 

lands. Development is relatively sparse. Loss in forest cover 

represents the largest change in land cover in the basin 

between 1987 and 2009. This appears to be mostly due to 

forestry activities, especially in the northern part of the basin. 

Since 1987, more than 18,000 acres of evergreen forest 

have been logged and are at various stages of regrowth. 

Recently, 1,300 of these acres were harvested, falling under 

the classification of “developed/sparsely vegetated.” Between 

1987 and 2009, more than 7,000 acres of shrub, grassland and 

open forest have changed in classification to evergreen forest, 

indicating previously logged areas that have now regenerated. 

Much of the increase in the open forest classification 

from 1987 to 2009 also is a result of harvesting practices. 

Areas likely are being converted from evergreen forest to 

low‐density, open forests from logging activities. Although to 

a lesser extent, changes from evergreen forest to open forest 

also may be the result of development activities, especially 

in the corridor along State Route 231 that connects the towns 

of Ford and Springdale. Development occurs at such a small 

scale in the basin relative to the pixel size of the satellite 

sensors (30 m2) that some development in this heavily forested 

area may be picked up as open forest rather than developed/

sparsely vegetated. The accuracy of the developed/sparsely 

vegetated classification generally was not as high as in 

other classes. Similar issues occurred with the accuracy of 

classifying water due to the small scale and low number of 

water bodies in the basin. 

According to the 2009 accuracy assessment, areas 

determined to be grassland, shrub, or agriculture were 

mistakenly classified as open forest. This may be due to 

confusion between spectral signatures. Areas that are mostly 

covered in grassland, shrub, or agriculture (pasture), but that 

also have some trees, may at times appear like open forestland. 

Therefore, some of the changes from these categories in 1987 

to the open forest category may not represent actual changes. 

Similarly, changes from the open forest category to the 

grassland or evergreen forest category also may be inaccurate, 

because there was some error in classifying these land cover 

types as open forest in the 1987 image. 

Changes in shrub cover mainly occurred on lands where 

forestry activities took place. Changes from shrub cover, 

specifically of young evergreen trees, to forest cover likely 

are a result of regeneration, and changes from forest cover 

to shrub are due to more recent logging activities, where 

regeneration is ongoing. 

Changes that involve deciduous shrub cover, grasslands, 

and agricultural lands are difficult to analyze because the 1987 

image was taken in autumn and the 2009 image was taken 

in summer. The difference in seasons of the two images may 

influence the LULC classifications, with deciduous plants 

looking vastly different between the summer and autumn, 

herbaceous plants dying back at the end of the growing 

season, and crops drying and being harvested at various 

points in time. Furthermore, although it appears that there 

has been a substantial decrease in the amount of agricultural 

lands and increase in the amount of grasslands in the basin, 

this could be a hasty conclusion and additional investigation 

is necessary to make this determination. The agriculture class 

includes a diverse group of land cover types, which is not 

ideal for a spectral signature. In addition to various crop types, 

some areas (though not many) are irrigated, certain crops 

are cut multiple times and have variable densities, and some 

fields are fallow or have been recently harvested. Pastureland 

also may have been classified as agriculture in some areas 

and as grassland in other areas. Therefore, overlap between 

these two classes probably exists. Although agriculture may 

have decreased in the basin, it is not likely to have been to 

the extent shown by this analysis. It is especially difficult to 

differentiate between classes such as agriculture and grassland 

from orthophotos. Changes in LULC often can occur rapidly 

due to harvesting activities; what was captured by the satellite 

image may be different from what is seen in orthophotos or on 

the ground. 

This analysis highlighted major changes that occurred 

in the Chamokane Creek basin between 1987 and 2009, 

specifically regarding evergreen forest cover. The analysis also 

will provide more specific LULC data for GSFLOW model 

compared to the generalized LULC products that currently 

are available. Additional studies would be needed to answer 

questions regarding changes in agriculture and specific crop 

types as well as changes in developed land area. Newer 

satellite sensors can show much more detail about present-day 

LULC; however, information regarding historical LULC will 

remain quite coarse. Further processing of the images and 

more advanced classification programs (for example, featurebased) also could help refine the LULC classifications for 

Chamokane Creek basin.
Appendix A 59

References Cited in Appendix A

Güler, Mustafa, Yomralioğlu Tahsin, and Reis, Selçuk 2007, 

Using landsat data to determine land use/land cover 

changes in Samsun, Turkey: Environmental Monitoring and 

Assessment, v. 127, no. 1–3, p. 113.

Lillesand, T. M., Kiefer, R.W., and W. Chipman, J.W., 2008, 

Remote sensing and image interpretation: Hoboken, N.J., 

John Wiley & Sons, 736 p.

Muñoz-Villers, L.E., and López-Blanco, J., 2008, Land use/

cover changes using Landsat TM/ETM images in a tropical 

and biodiverse mountainous area of central-eastern Mexico:

International Journal of Remote Sensing, v. 29, no. 1, 71-93.

Multi-Resolution Land Characteristics Consortium, 2008, 

NLCD 2001 Land Cover Class Definitions, National Land 

Cover Database, accessed May 27, 2010, at http://www.

mrlc.gov/nlcd_definitions.php.

U.S. Geological Survey, 2009, Earth Resources and Science 

(EROS) Center Thematic Mapper (TM), Products and Data: 

U.S. Geological Survey database, available at http://eros.

usgs.gov/#/Find_Data/Products_and_Data_Available/TM.
60 Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Stevens County, Washington

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Kahle and others— Hydrogeologic Framework and Groundwater and Surface-Water Systems, Chamokane Creek Basin, Washington—Scientific Investigations Report 2010–5165