Environmental and Hydrologic Overview of t

Yukon River Basin, Alaska and CanadaWater-Resources Investigations Report 99-4204U.S. Department of the InteriorU.S. Geological Survey
Cover: Digital elevation model of the Yukon River Basin
Environmental and Hydrologic Overview of the Yukon River Bas

Alaska and CanadaBy Timothy P. Brabets, Bronwen Wang, and Robert H. Meade_________________________________________________________________________________U.S. GEOLOGICAL SURVEYWater-Resources Investigations Report 99-4204

 Anchorage, Alaska

2000
U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, SecretaryU.S. GEOLOGICAL SURVEYCHARLES G. GROAT, DirectorCONTRIBUTING U.S. GEOLOGICAL SURVEY STAFFEditorial, Graphics, and Text PreparationE.F. Snyder, Technical EditorL-L. Harris, Cartographic TechnicianFor additional information: Copies of this report may be purcDistrict Chief U.S. Geological SurveyU.S. Geological Survey Branch of Information Services4230 University Drive, Suite 201 Box 25286Anchorage, AK 99508-4664 Denver, CO 80225-0286http://ak.water.usgs.gov
CONTENTS

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Description and History of the Yukon River Basin . . . . . . . . . . . . . . . . . . 7

The Yukon River and its Major Tributaries. . . . . . . . . . . . . . . . . . . . . 7Exploration of the Yukon River Basin . . . . . . . . . . . . . . . . . . . . . . . . 11People and Land. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Economic Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Environmental Characteristics of the Yukon River Basin . . . . . . . . . . . . . 16

Physiography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Climate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Land Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Permafrost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Ecoregions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Hydrologic Characteristics of the Yukon River Basin . . . . . . . . . . . . . . . . 48

Surface Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Snow and Ice. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50Streamflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50Floods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60Droughts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

Sediment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Sources of Sediment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65Suspended-Sediment Concentrations . . . . . . . . . . . . . . . . . . . . . . 66Relation Between Suspended-Sediment Concentration and Water Discharge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68Suspended-Sediment Discharge . . . . . . . . . . . . . . . . . . . . . . . . . 72Storage of Sediment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75Bedload. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Water Quality. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

Yukon River Main Stem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84Temporal Variations in Water Quality . . . . . . . . . . . . . . . . . . . . . 94Spatial Variations in Water Quality . . . . . . . . . . . . . . . . . . . . . . . 97Anthropogenic Effects on Water Quality . . . . . . . . . . . . . . . . . . . 102

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103References Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

FIGURES

1. Map showing location of the Yukon River B

and Alaska . . . . . . . . . . . . . . . . . . . . . . . . . . 

2. Map showing digital elevation model of the Y3. Graph showing number of growing days for 

Yukon River Basin, 1991-99 . . . . . . . . . . . . 

4. Map showing observed trends of Arctic annu

temperatures from 1961-90 . . . . . . . . . . . . . 

5. A. Map showing rivers, lakes, and glaciers o

River Basin . . . . . . . . . . . . . . . . . . . . . . 

B. Map showing roads and towns in the Yuk

6. Cross sections of the Yukon River above Fra

Territory, to Pilot Station, Alaska . . . . . . . . 

7-18. Maps showing:

7. Land ownership of the Yukon River Basi8. Physiographic regions of the Yukon Rive9. Precipitation regions of the Yukon River 10. Geology of the Yukon River Basin . . . . 11. Land cover classes of the Yukon River B12. Soils of the Yukon River Basin . . . . . . . 13. Permafrost regions of the Yukon River B14. Wetland areas of the Yukon River Basin 15. Areas of forest fires in the Yukon River B16. Ecoregions of the Yukon River Basin . . 17. Major drainage basins in the Yukon Rive18. Location of streamflow-gaging stations w

years of record in the Yukon River Basin 

19-22. Graphs showing: 

19. Flow statistics of three rivers near the hea

Yukon River . . . . . . . . . . . . . . . . . . . . . . 

20. Flow statistics of nine major rivers of the 21. Average discharge of the Yukon River at 22. Percent contributions of area and flow of 

basins of the Yukon River Basin . . . . . . 

23. Map showing percentage of major river outfl

seas of the Arctic Ocean . . . . . . . . . . . . . 
24-25. Graphs showing:

24. Flow statistics of the Salcha River near Salchaket, Alaska . . . . 6125. Departure from average discharge for several long-term 

streamflow-gaging stations in the Yukon River Basin . . . . . . . 63

26. Boxplots of suspended-sediment concentration at 14 sites in 

the Yukon River Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

27-34. Graphs showing:

27. Water discharge and suspended-sediment concentrations for 

Chena River at Fairbanks, Alaska and Nenana River near Healy, Alaska for 1964-66 runoff seasons. . . . . . . . . . . . . . . . . 69

28. Instantaneous discharge and suspended-sediment concentrations for different particle sizes for Tanana River near 

Tanacross, Alaska and Tanana River at Fairbanks, Alaska. . . . 70

29. Average daily water discharge and suspended-sediment

concentration for Tanana River near Tanacross, Alaska andYukon River at Eagle, Alaska during 1963 runoff season . . . . 71

30. Seasonal distribution of suspended-sediment discharge for

three rivers in the Yukon River Basin . . . . . . . . . . . . . . . . . . . . 72

31. Differences in water discharge and suspended-sediment 

load during water years 1964-66 for Nenana River nearHealy, Alaska and Chena River at Fairbanks, Alaska . . . . . . . . 73

32. Changing proportions of suspended-sediment discharge 

during 1954 runoff season in Tanana River nearTanacross, Alaska . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

33. Annual suspended-sediment loads for 14 sites located in the 

Yukon River Basin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

34. Suspended-sediment and bedload discharge measured in the 

Tanana River at Fairbanks, Alaska, 1977-82. . . . . . . . . . . . . . . 77

35. Map showing location of water-quality sampling stations where 

one or more samples have been collected in the Yukon River Basin. . 79

36. Map showing location of water-quality sampling stations where 

10 or more samples have been collected in the Yukon River Basin . . 80

37. Boxplots of specific conductance from samples taken during open 

water and under ice cover on the Yukon River . . . . . . . . . . . . . . . . 95

TABLES

1. Comparison of salmon harvests for various ti

River Basin, Alaska . . . . . . . . . . . . . . . . . . . 

2. Watersheds where mining has occurred in th

Basin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

3. Types and areas of land cover in the Yukon R4. Areas of ecoregions in the Yukon River Basi5. Major drainage basins in the Yukon River Ba6. Streamflow-gaging stations in the Yukon Riv

10 or more years of record . . . . . . . . . . . . . . 

7. Flow contributions of major drainage basins 

Basin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

8. Suspended-sediment stations in the Yukon R9. Mean grain-size composition of suspended s

in the Yukon River Basin . . . . . . . . . . . . . . . 

10. Estimated annual suspended-sediment loads 

the Yukon River Basin . . . . . . . . . . . . . . . . . 

11. Water-quality stations in the Yukon River Ba

more years of record. . . . . . . . . . . . . . . . . . . 

12. Summary statistics for selected properties an

surface-water samples from stations along th

13. Summary statistics for selected properties an

surface-water samples from tributaries of the 

14. Comparison of samples taken during open w

ice cover, Yukon River at Pilot Station . . . . 

15.Summary statistics for selected properties 

surface-water samples by ecoregion
CONVERSION FACTORS, ABBREVIATED UNITS, AND VERTICAL DATUM

Multiply by To obtain

inch (in.) 25.4 millimeter 

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

square foot (ft2) 0.09290 square meter

square mile (mi2) 2.590 square kilometer

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

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

inch per year (in/yr) 25.4 millimeter per year

ton 0.9072 megagram

ton per day (ton/d) 0.9072 megagram per day

ton per year (ton/d) 0.9072 megagram per year

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

In this report, temperature is reported in degrees Fahrenheit (°F), which can be converted to degrees Celsius (°C)by the following equation:

°C = (°F-32)/1.8

OTHER ABBREVIATED UNITSmg/L, milligram per literμg/L, microgram per literμS/cm, microsiemen per centimeter at 25 degrees Celsius

mm, millimeterVERTICAL DATUMSea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929—A geodetic datum derifrom a general adjustment of the first-order level nets of the United States and Canada, formerly called Sea LeveDatum of 1929.

ABSTRACT

The Yukon River, located in northwestern Canada and central Alaska, drains an area of more than 330,000 square miles,

making it the fourth largest drainage basin in North America.Approximately 126,000 people live in this basin and 10 percent ofthese people maintain a subsistence lifestyle, depending on thebasin’s fish and game resources. Twenty ecoregions compose theYukon River Basin, which indicates the large diversity of naturalfeatures of the watershed, such as climate, soils, permafrost, andgeology.

Although the annual mean discharge of the Yukon River near

its mouth is more than 200,000 cubic feet per second, most of theflow occurs in the summer months from snowmelt, rainfall, andglacial melt. Eight major rivers flow into the Yukon River. Two ofthese rivers, the Tanana River and the White River, are glacier-fedrivers and together account for 29 percent of the total water flowof the Yukon. Two others, the Porcupine River and the KoyukukRiver, are underlain by continuous permafrost and drain largerareas than the Tanana and the White, but together contribute only22 percent of the total water flow in the Yukon.

At its mouth, the Yukon River transports about 60 million

tons of suspended sediment annually into the Bering Sea. However, an estimated 20 million tons annually is deposited on flood

plains and in braided reaches of the river. Tstem of the Yukon River and its tributaries cium magnesium bicarbonate waters with generally less than 400 microsiemens per city of the Yukon River Basin varies tempoand winter. Water quality also varies spatialINTRODUCTION

Few rivers have the intrinsic allure o

history, people, and mystique have innate atransportation corridor in a vast area of roaspecies migrate the entire length of the river a staple of the subsistence lifestyle of rural towns obtain water for drinking from the rivfers. Recreational activities abound for both However, the river is not benign: flooding ato people, buildings, roads, and airfields.

The Yukon River Basin (figs. 1 and 

western Canada and central Alaska, and is ami2 in area. The basin represents one of 

diverse ecosystems in North America. Despperceived invulnerability, the Yukon River example, from 1991 to 1999, the numbe

Environmental and Hydrologic Overview of the Yukon River BAlaska and CanadaBy Timothy P. Brabets, Bronwen Wang and Robert H. Meade
2 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Arctic Ocean

Cana

Alaska

Yukon River Basin

Northwes

168o 160o 152o 144o 136o 128o 176o 180o 176o 120o 

72o 160o 168o

68o64o

60o

56o

Russia

Bering Sea

7

Yukon 

Territory

Figure 1. Location of the Yukon River Basin in Canada and Alaska.

0

0

100

100

200

200 300 KILOMETERS

300 MILES
DIGITAL ELEVATION MODEL 

Figure 2. Digital elevation model of the Yukon River Basin.
4 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Alaska for four ecoregions has ranged from 130 to 194 days (fig.3). Air temperature records from 1961-90 indicate a warmingtrend on the order of 1.4 °F (0.75 °C) per decade at latitudes where

the Yukon River is located (fig. 4) (Chapman and Walsh, 1993). Ifthis warming trend continues, the growing season will likelyincrease. Climate changes will also influence the permafrost distribution, glacial runoff, and biogeochemic

from the basin (BESIS, 1997). The Yukon Rital to the Bering Sea ecosystem (fig. 1), proviwater runoff, sediments, and dissolved solutof the sea (Lisitsysn, 1969). Thus, processYukon River could in turn influence the Beri

1990 1992 1994 1996 1998 2000

120200140160180

NUMBER OF GROWING DAYS

Figure 3. Number of growing days for four ecoregions of the Yukon River Basin, 1991-99 (dataprovided by Carl Markon, USGS, 1999; see figure 16 for location of ecoregions).

YEAR

Yukon PlaInterior HInterior BInterior Fo

EXPLANA
Purpose and Sco

This report sum

mental, flow, and wistics of the Yukopurpose of this sumgain a more completcurrently known surquality characteristiand (2) to provide baneeded to design a sampling program foof this study incluRiver Basin. Only used in this compilawater is an importanYukon River Basin, report only in generAcknowledgmen

The authors g

the efforts of the Wada/Environment streamflow and watfor use in this repovided discharge and data and Andrea Rythe web to waterMarkon (USGS) pgrowing seasons in the land cover charaand Alaska data semap of the entire ba
6 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Marshall Russian Mission

Four villages along the lower Yukon River that were flooded from ice jams in 1988. Many villages located along the ban

and its major tributaries are subject to flooding during ice breakup. (photographs courtesy of Larry Rundquist, National 

Pitkas Point 

M
Description and History 

DESCRIPTION AND HISTORY OF THE YUKON RIVER BASINThe Yukon River and its Major Tributaries

The Yukon River Basin is the fourth largest basin in North

America and the fifth largest in terms of average discharge(Schumm and Winkley, 1994). Although no universal agreementexists as to the source of the Yukon River, it is believed to originatefrom the Llewellyn Glacier, near Atlin Lake, in northwestern British Columbia (Parfit, 1998) (fig. 5A). From this point, the riverflows for more than 2,000 mi in a broad arc through the Yukon Territory of Canada and central Alaska, emptying into the Bering Sea.

From its headwaters, the Yukon River generally flows northwestward to the Canada/Alaska boundary. Near the outlet of Lake

Laberge (fig. 5A) above Frank Creek, the river is approximately300 ft wide (fig. 6A), but downstream from the junction of the Teslin River at Carmacks, the width increases to about 600 ft (fig. 6B).Below Carmacks, the Dawson Range lies on the west and the Ogilvie and Pelly Mountains lie on the east. The Pelly and Stewart Rivers (fig. 5A), whose sources are along the Yukon Territory/Northwest Territories border, drain about 38,000 mi2. The White

River (fig. 5A) drains about 18,000 mi2, and includes the extensive

snowfields and glaciers of the Wrangell

–St. Elias Mountains. The

inflow from these three large rivers increases the width of theYukon to approximately 1,000 ft at Dawson (fig. 6C).

At Fortymile, in Canada, about 60 river miles upstream from

Eagle (fig. 5B), the Yukon River flows between bluffs of theTanana Uplands on the south and the Ogilvie Mountains on thenorth. At Eagle, the width of the Yukon has increased to about1,500 ft (fig. 6D). From Eagle, the Yukon flows for about 150 mithrough the Yukon-Charley Rivers National Preserve to Circle(fig. 5B). This national park encompasses parts of the valley on

both sides of the Yukon and all of the draRiver, a designated National Wild and Sceand Kandik Rivers, entering from the norttributaries between Eagle and Circle.

At Circle, the altitude of the Yukon R

600 ft above sea level and yet the river is stinland. Circle marks the beginning of the Yuland area crisscrossed by meandering river stantly shifting. Much of the lowland is paNational Wildlife Refuge. The landscape iterrain and is encircled by mountains, whiccold. This feature results in extreme air temmer (as high as 100 oF) and winter (as low 

Approximately 60 mi downstream fro

of Fort Yukon (fig. 5B), where the PorcuYukon River from the northeast (fig. 5A). drains about 45,000 mi2 of the northeast pa

Basin and is about 500 mi long. Downstream Chandalar River, which drains the Brooks Rfrom the north. The Yukon River reaches its the Arctic Circle at this location, and begins southward to the Bering Sea.

Stevens Village (fig. 5B) marks the a

Yukon Flats. The Yukon River flows in a sometimes referred to as Rampart Canyon. is approximately 2,000 ft wide (fig. 6E) and the trans-Alaska oil pipeline crosses the rivmi downstream from Stevens Village, the TYukon from the southeast (fig. 5A). The Ttributary to the Yukon and drains approx

Included in the Tanana drainage is the noRange, an extensively glaciated area.
8 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

0

0 100

100

200

200

300 KILOMETERS

300 MILES

RIVERS, LAKES AND GLACIERS

Andreafsky R.

Innoko R.

Melozitna R.

Koyukuk R.

South Fork 

Kanuti R. Koyukuk R.

Nowitna R.

Tozitna R.

Tanana R.

Dall 

R.

Hodzana 

 R.

Chandalar 

 R.

Old Crow 

 R.

Porcupine R.

Tanana R.

Nenana R.

Chena R.

Salcha R.

Goodpaster R.

Charley

 R.

Kandik R.

Nation R.

Klondike R.

Stewart R.

Pelly R.

White R. Kluane R.Frank Cr. Lake Laber

YUKON RIVER

YUKON RIVER

YUKON RIVER

YUKON RIVER

YUKON RIVER

YUKON 

 RIVER

Fan

BERING 

 SEA

Alaska Range

Wrangell-St.Elias Mt

Figure 5A. Rivers, lakes and glaciers of the Yukon River Basin.
Description and History 

Figure 5B. Roads and towns in the Yukon River Basin.

ALASKA

HIGHWAY

ROADS & TOWNS

0

0 100

100

200

200

300 KILOMETERS

300 MILES

Newtok

Saint Marys Pilot Station

Russian Mission

Holy Cross

Grayling

Shageluk

Kaltag

Koyukuk Ruby

Huslia

Hughes

Alatna

Bettles

Anaktuvuk Pass

Wiseman

Tanana

Rampart

Minto Fairbanks

Nenana

Cantwell

Healy

Delta Junction

Dot Lake

Eagle

Dawson

Northway Junction

Beaver Creek

Destruction Bay

Stewart Cro

Pelly Cross

Carmac

Mayo

Central

Circle

Birch Creek

Fort Yukon

Venetie

Arctic Village Old Crow

HooperBay

Chevak

Anvik

Kotlik

Alakanuk

Galena

Nulato

Allakaket

Beaver

StevensVillage

Livengood

Manley HotSprings

North Pole

Two Rivers

Big Delta

Tok

Boundary

Burwash Landing

Ohogamiut

MountainVillage

Tanacross

Fortymile
10 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Discharge = 22,900 ft3/s Width = 302 ft

Area = 3,540 ft2 Velocity = 6.47 ft/s

Discharge = 23,000 ft3/s

Width = 597 ftArea = 5,000 ft2

Velocity = 4.60 ft/s

Discharge = 108,000 ft3/s

Area = 23,600 ft2

Velocity = 4.58 ft/s

ARBITRARY GAGE HEIGHT, IN FEET

0

2010

0

2010

0

4020

0 50 100 150 200 250 300 350

A. YUKON RIVER ABOVE FRANK CREEK, AUGUST 6, 1991

0 200 400 600 800

B. YUKON RIVER AT CARMACKS, MAY 20, 1992

0 200 400 600 800 1000 1200

C. YUKON RIVER AT DAWSON, OCTOBER 9, 1991

Width = 1,000 ft

Figure 6. Cross sections of the Yukon River above Territory, to Pilot Station, Alaska.

-20

40

0

20

0 500 1000 1500 2000

D. YUKON RIVER AT EAGLE, AUGUST 1, 1997

Discharge = 229,000 ft3/s

Width = 1550 ftArea = 33,800 ft2

Velocity = 6.78 ft/s

DISTANCE, IN FEET FROM LEFT BANK

0

40102030

0 500 1000 1500 

E. YUKON RIVER NEAR STEVENS VILLAGE, 

SEPTEMBER 21, 1995

Disc

Wid

Area 

Velo

0 1000 2000 

F. YUKON RIVER AT RUBY, JULY 15, 1976

-40

20

-20

0

500 1000 1500 2000 

G. YUKON RIVER AT PILOT STATION, JUNE 26, 1996

-60

20

-40-20

0

ARBITRARY GAGE HEIGHT, IN FEET Disch

Width Area 

Veloc

Discharge = 415,000 ft3/s

Width = 2850 ftArea = 131,000 ft2

Velocity = 3.17 ft/s

DISTANCE, IN FEET FROM LEFT B

0
Description and History o

Past the Tanana River, the Nowitna National Wildlife Refuge

is located on the south side of the Yukon River for approximately70 mi. The Nowitna River, a National Wild and Scenic River,enters the Yukon from the southeast. Past the wildlife refuge is thevillage of Ruby, where the Melozitna River enters from the north(fig. 5A). The width of the Yukon is approximately 2,500 ft atRuby (fig. 6F). Galena, a village located about 50 mi downstreamfrom Ruby is the largest community in this part of the Yukon RiverBasin.

Downstream from Galena, the Koyukuk River, a major tributary of the Yukon River, enters the Yukon from the north. The

Koyukuk, which drains much of the north-central part of theYukon River Basin, has a drainage area of about 35,000 mi2 and is

about 400 mi in length. At this point, the Yukon changes direction,flowing almost due south for about 160 mi. The Innoko NationalWildlife Refuge is located on the east side of the river and near theend of this stretch of the Yukon, the Innoko River enters the Yukonnear the village of Holy Cross. The Innoko River drains much ofthe area between the Yukon and Kuskokwim Rivers and flows ina broad S for about 500 mi.

Holy Cross is located about 280 mi upstream from the mouth

of the Yukon. Several miles downstream from this village, theYukon River begins to flow to the west, between hills and bluffsapproximately 2,000 ft high. At Ohogamiut, an abandoned fishingvillage, the river turns northward. As the Yukon passes Pilot Station, the channel is about 3,000 ft wide (fig. 6G). Near SaintMarys, the Andreafsky River enters. The Andreafsky River is relatively small but has been designated a National Wild and Scenicriver. From Saint Marys, the Yukon River flows through manychannels in a large wetland area and then to the Bering Sea.

Exploration of the Yukon River Basin

The following history of the Yukon R

rized from publications by the Alaska Geog1990, and 1991). The aboriginal people of tmay be among the oldest known residents of crossing Beringia, the land bridge that once ica, these early people occupied Alaska and Yukon Territory. Those who did not trade wof southeastern Alaska remained free of inftures until the 19th century.

Interest in furs, not gold, lured the 

Yukon. One of the earliest explorations oEuropeans was undertaken by Robert CamBay Company. In 1840, Campbell explored 1848 established an outpost at the junction oRivers. John Bell, also of the Hudson’s Bathe Porcupine River in 1844 and establishYukon. 

Beginning in the 1870’s, Leroy McQu

and Alfred Mayo, established a number of down the Yukon River. The threesome spenmer and fall prospecting and began to realizwealth of the Yukon. Foreseeing the passinthe rise of the prospector, they gradually chthe needs of Natives and fur traders to equipminers. In 1885, miners found placer gold and in 1886, gold was discovered on the Ftional discoveries were made in the Circle 1893. However, these first paying strikes in were only a trickle compared to the tidal would come with the Klondike discoveries 
12 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Between 1897 and 1900, people from virtually every corner

of the world and from every conceivable background headedtoward the Klondike. At its peak, Dawson was home to as many as25,000 people. Although only a few “struck it rich,” the 1897 gold

rush to the Klondike in the Yukon Territory, more than any otherevent, led to commercial mining in the Yukon River Basin. Manyprospectors who arrived too late began to explore all through theYukon River Basin, setting off mini-stampedes to areas reportingnew gold strikes.

The construction of the Alaska Highway (fig. 5B) in 1942, to

provide a road link from the Lower 48 to Alaska as a defense measure during World War II, signaled an end to a way of life in theYukon. Commercial river traffic ended a few years later. Gradually, a network of roads was constructed that today links many ofthe communities.People and Land

Approximately 126,000 people live in the Yukon River

Basin and 10 percent of these people maintain a subsistence lifestyle, depending on the basin’s fish and game resources. In the

Canadian part of the Yukon River Basin, Whitehorse (fig. 5B) isthe center of population with just over 23,000 residents in 1998(Environment Canada, 1999). The towns of Dawson and Farohave just over 2,000 and 1,000 residents respectively. The remaining towns have populations ranging from 100 to 500 residents. InAlaska, the greater Fairbanks area (Fairbanks and North Pole) isthe center of population and had approximately 84,000 residents in1996 (Alaska Department of Labor, 1999). About 12,000 otherresidents are located in 43 villages scattered across the YukonRiver Basin from the Canadian border to the mouth of the YukonRiver. Village populations range from approximately 30 to 800people, with typical villages having fewer than 300 residents. Two

major ethnic groups historically occupied ththe Yupik Eskimos who live along the Berinup the river approximately 250 mi, and thwho occupy the remainder of the basin.

The Canada segment of the Yukon 

parts of two Canadian National Parks, Vuntin addition to several Habitat Protection APark is located near the headwaters of the lands compose about 9 percent of the land Yukon. In the Alaska part of the Yukon Rivecent of the land is owned by the Federal govparks cover 10 percent of the area, 8 wildlife cent of the area, and Bureau of Land Mancovers 22 percent (fig. 7). The U.S. militartions each own approximately 1 percent of 

The Yukon River at Dawson, Yukon Territriver is 1,000 feet wide. Today, the popuabout 2,000, but at the height of the Klonpopulation was 25,000.
Description and History o

Figure 7. Land ownership of the Yukon River Basin.

0

0 100

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200

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300 MILES

Vuntut 

Arctic NWR National Park

Yukon Flats NWR

Gates of the Arctic 

National Park and Preserve

Kanuti NWR

Koyukuk NWR

Nowitna NWR

Innoko NWR

Yukon Delta NWR Denali

National Park andPreserve

Yukon-Charley Rivers National Preserve

Teslin NWR

Wrangell-St.Elias National Park an

Kluane National Park

National and Provincial Parks and Preserves

National Wildlife Refuges (NWR)

BLM/Habitat Protection Area

Military

Native Patent

Native Selected

LAND OWNERSHIP 
14 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Economic Activity

To a large extent in Alaska, and to a smaller extent in Canada, nearly all the people who reside in the Yukon River Basin villages are dependent to varying degrees on fish and game resources

for their livelihood (Holder and Senecal-Albrecht, 1998). Subsistence salmon fishing is commonly undertaken by extended familygroups of two or more households cooperating to harvest, cut, preserve, and store salmon for personal use. Many people who fish forsubsistence salmon also fish commercially. The development ofthe commercial export salmon fishery has enabled many area residents to obtain a cash income. In many cases, the cash incomeprovides a means for fishermen to maintain a subsistence lifestyle. Income from commercial fishing is commonly used toobtain hunting and fishing gear used for subsistence activities.Thus, in many of these villages, the commercial and subsistencesectors of the economy are complementary and mutually supported. Households have been required to convert to a cash-oriented economy because payments for mortgages, water, sewer,electric, telephone, and groceries require cash. Yet, even the mostmodern villages have remained subsistence-based because of theintrinsic value of subsistence activities and because local renewable resources form the most reliable base of the economy fromyear to year.

Two commercial fishing seasons in the Yukon River Basin

are the summer season, which targets chinook and summer chumsalmon, and the fall season, which targets fall chum salmon withan incidental harvest of coho salmon. Yukon River salmon stockshave generally remained healthy, primarily because their spawning, rearing, and migration habitat remain undisturbed. However,in 1997 and 1998, runs of the chum salmon in the Yukon RiverBasin declined sharply (table 1) and many of the villages sufferedfrom the effects. Not only have commercial fisherman taken huge

Table 1. Comparison of salmon harvests for vaYukon River Basin, Alaska[Data from Holder and Senecal-Albrecht, 1998; --, data not ava

Year Subsistence Commercial 

Chinook salmon

1961-86 average 24,452 109,401 1987-91 average 49,634 109,302 1992-96 average 51,669 110,276 1997 66,278 121,732 1998 53,733 43,699 

Summer chum salmon

1961-86 average 192,003 466,459 1987-91 average 155,754 978,726 1992-96 average 117,529 491,610 1997 97,109 230,842 1998 86,004 28,798 

Fall chum salmon

1961-86 average 106,897 182,251 1987-91 average 210,392 173,539 1992-96 average 113,673 84,408 1997 102,937 67,122 1998 62,867 0 

Coho salmon

1961-86 average 17,199 21,292 1987-91 average 55,517 68,399 1992-96 average 34,288 23,724 1997 24,593 35,820 1998 12,904 0 
Description and History o

losses (with a corresponding effect on local businesses), but manyvillages that depend on salmon as a main staple of their diet nowfind them in short supply.

Mining activity was, and remains, an important economic

industry within the basin (table 2). Most historical mining activityoccurred on localized, discrete, headwater streams using manuallabor which helped to minimize impacts on salmon spawning habitat. Mining operations have to cope with short operating seasons,difficult transportation conditions, and high freight and laborcosts. Both small and large mining operations exist today. Rigidenforcement of environmental regulations since the mid-1980’s

has resulted in mining operations that are less detrimental to fishhabitat than in the past. In 1999, two large hard-rock mines wereoperating: the Illinois Creek mine in the Upper Innoko drainagenear Galena and the Fort Knox mine near Fairbanks. A third site,the Pogo Mine, was being assessed for development in the Goodpaster River Basin (fig. 5A) near Big Delta.

Another natural resource activity in the Yukon River Basin is

logging. Although not as large an industry as fishing or mining,logging could increase as large tracts of Federal land are transferred into Native corporations and State ownership, and bothlocal and export timber demands increase. Primary areas of logging are the Tanana River Basin (Alaska) and the southeastern partof the Yukon Territory near Teslin. 

Other economic activities complement the natural resource

activities in the Yukon River Basin. These include tourism in bothAlaska and Canada, government, and service industries. The U.S.military also has a strong presence in Alaska with two Army reservations and one Air Force base. During the Cold War, the military also operated several radar sites along the Yukon River at FortYukon and Galena.

Table 2. Watersheds where mining has Yukon River Basin

Watershed Neare

American Creek TananBeaver Creek Fort YBirch Creek Fort YChatanika River FairbaChena River FairbaCoal Creek CircleEureka Creek NenanFortymile River EagleGoldstream Creek FairbaHogatza River AlatnaIditarod River ShageInnoko River ShageLivengood Creek LivenMiddle Fork Koyukuk River WisemMinook Creek RampNome Creek LivenSouth Fork Koyukuk River WisemSulatna Creek RubyWoodchopper Creek Circle
16 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

ENVIRONMENTAL CHARACTERISTICS OF THE YUKON RIVER BASINPhysiography

The purpose of physiographic classification is to divide an

area into smaller regions that are topographically distinct from surrounding regions. Thus, the boundaries of the physiographicregions are typically drawn where the topography changes in character. Physiographic divisions of the Yukon River Basin forAlaska were classified by Wahrhaftig (1965) and for Canada byBostock (1970). Five general physiographic regions are present inthe Yukon River Basin (fig. 8): (1) rolling topography and gentleslopes, 37 percent; (2) low mountains, generally rolling, 24 percent; (3) plains and lowlands, 20 percent; (4) moderately high rugged mountains, 17 percent; and (5) extremely high ruggedmountains, 2 percent. The following specific descriptions aremodified from Wahrhaftig (1965) and can be inferred from thedigital elevation map of the Yukon River Basin (fig. 2).

Alaska Range (Central and Eastern Part)

—The central

and eastern part of the Alaska Range consists of two or three parallel rugged glaciated ridges, 6,000-9,000 ft in altitude, surmounted by groups of extremely rugged snow-capped mountainsmore than 9,500 ft in altitude. Mount McKinley, 20,320 ft high andthe highest mountain in North America, is located in this part ofthe Alaska Range. Most of the rivers and streams flow into theTanana River. Rivers are swift and braided, and most rivers headin glaciers. The high mountains are sheathed in ice, and valley glaciers as much as 40 mi long and 5 mi wide radiate from them.

Central and Eastern Brooks Range

—The Central and

Eastern Brooks Range is a wilderness of rugged glaciated easttrending ridges that rise to summits 7,000-8,000 ft in altitude in the

northern part and 4,000-6,000 ft in altitudThe eastern part of the range has belts of harand volcanic rocks. The mountains have ccharacteristic of glacially eroded bedded rosouthward to the Yukon and Koyukuk Riverated valleys ranging from 0.5 to 2 mi in wiciers are common in the higher parts of the 

Indian River Uplands

—This region 

low gentle ridges having rounded accorda2,000 ft altitude interspersed with irregulaflat divides. A few mountains rise to 4,0Koyukuk and Kanuti Rivers cross the uplanfew hundred feet deep. Most of the regiKoyukuk River and its tributaries. Numeroulowlands, valleys, and broad passes. Althociers, the entire land area is underlain by pe

Innoko Lowlands

—The Innoko Low

flat flood plains, dendritic in pattern, whosgenerally steep banks cut into the surrounRiver and a large tributary, the Innoko RivThe main part of the lowlands has a compleof meandering sloughs of these two streamsscroll lakes are abundant in recently abandpartly silted sloughs. Thaw lakes also abouand on gentle silt-covered slopes.

Kokrine-Hodzana Highlands

—Th

even-topped rounded ridges rising to 2,000-mounted by isolated areas of more rugged compact highland in the northeastern part ha4,500 and 5,700 ft in altitude. The irregbetween the Yukon River and its large trRiver, passes through these highlands. D
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Figure 8. Physiographic regions of the Yukon River Basin (modified from Wahrhaftig, 1965 and Bostock, 1970).

Rolling topography and gentle slopesLow mountains, generally rollingPlains and lowlandsModerately high rugged mountainsExtremely high rugged mountains Central & Eastern Brooks Range Porcupine Plateau

Ogilvie Mountains

Wrangell-St.Elias Mou

Northern Foothills-Alaska Range

Alaska Range

Yukon-Tanana Upland

Yukon Flats Kokrine-Hodzana Highlands Indian River Uplands Tanana-Kuskokwim Lowland Nowitna Lowland Tozitna-Melozitna Lowland

InnokoLowlands

Yukon-KuskokwimCoastal Lowland

Nulato Hills

Koyukuk Flats

PHYSIOGRAPHIC REGIONS
18 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

River is by way of the Hodzana, Tozitna, Melozitna, and Dall Rivers and many shorter streams. Drainage to the Koyukuk River isby the Kanuti River and the South Fork Koyukuk River.

Koyukuk Flats

—The Koyukuk Flats form an extensive

lowland of irregular outline at the junction of the Yukon andKoyukuk Rivers. The central part of the Koyukuk Flats are flatplains 5-20 mi wide, along the major rivers. The parts immediatelyadjacent to the rivers are meander belts 5-10 mi wide and the partsfarther away are dotted by thaw lakes. Broad rolling silt plainsstand 100-200 ft above these central plains and merge with the surrounding uplands. The Flats are drained by the Yukon River.

Northern Foothills of the Alaska Range

—The topography

of this region consists of flat-topped east-trending ridges 2,000-4,500 ft in altitude, 3-7 mi wide, and 5-20 mi long that are separated by rolling lowlands 700-1,500 ft in altitude and 2-10 miwide. All rivers and streams in this region flow into the TananaRiver. No glaciers are present in this region.

Nowitna Lowland

—The Nowitna Lowland is a rolling siltcovered tableland ranging from 250-900 ft in altitude and having

a local relief of 50-250 ft and slopes of 100-150 ft/mi into whichflat flood plains of the major rivers have been incised 150-300 ft.The entire lowland is drained by the Yukon River, which followsthe northern boundary. The confluence of the Yukon River withthe Tanana River is in the eastern part of the lowland. The southernpart of the lowland is drained by the Nowitna River, a tributary ofthe Yukon River. 

Nulato Hills

—The Nulato Hills consist of northeast-trending even-crested ridges, 1,000-2,000 ft in altitude, having gentle

slopes. Valleys are narrow and have flat floors that are generallytrenched in their upstream parts to depths of about 30 ft. Streamsflow to the Yukon River.

Ogilvie Mountains

—The Ogilvie M

slopes and deep narrow valleys. Mountain paltitude, and local relief is as much as 4,000 connected and passes are few. The narrow by gorges where rivers cross cliff-forminmajor river drainages are the Kandik, Natioers, all tributaries of the Yukon River. No gmost of this region is underlain by permafro

Porcupine Plateau

—The Porcupine 

by low ridges having gentle slopes and ro1,500-2,500 ft in altitude. A few mountains floors are broad and valley patterns are irreSheenjek, and Coleen Rivers rise in the Brsouthward across the plateau in broad valleand outwash terraces. The Porcupine River a narrow cliff-lined canyon 50-500 ft deepBlack Rivers, which drain the southeastern der through broad irregular flats. The Porcglaciers, but the entire area is underlain by c

Tanana-Kuskokwim Lowland

—Th

depression bordering the Alaska Range on and eastern parts of the lowland are drained Braided glacial streams rising in the Alaska across the lowland. Thaw lakes are presenvium and the entire area consists of permaf

Tozitna-Melozitna Lowland

—This 

plain, 5-10 mi wide, is drained by the Toziters. These two rivers flow southward from gorges across the Kokrine-Hodzana HighlanThe lowland contains numerous thaw and oxuous areas of permafrost are present.
Wrangell–St. Elias Mountains—The Wrangell Mountains

are an oval group of shield and composite volcanoes that riseabove a low plain on the north and west and above heavily glaciated cliffed and castellated ridges on the south and east. About 25percent of the region drains into the Tanana River by way of theNabesna and Chisana Rivers and into the Yukon River by way ofthe White River. The St. Elias Mountains are probably the mostspectacular mountains of North America. Massive isolated blocklike mountains 14,000-19,000 ft in altitude rise at intervals of 5-30mi from a network of narrow ridges and sharp peaks. The averagealtitude of icefields in the interconnected valley system is 3,000-7,000 ft. Local relief is extreme and jagged cliffs abound. 

Yukon Flats—The Yukon Flats region consists of marshy

lake-dotted flats rising from 300 ft in altitude on the west to 600-900 ft on the north and east. The northern part of the flats is madeup of gently sloping outwash fans of the Chandalar, Christian, andSheenjek Rivers. The southeastern part of the flats is the broadgentle outwash fan of the Yukon River. Other areas are flat floodplains. Rolling silt and gravel-covered marginal terraces havingsharp escarpments 150-600 ft high rise above the flats and slopegradually up to altitudes of about 1,500 ft at the base of surrounding uplands and mountains. The region is drained by the YukonRiver, which has a braided course southeast of the bend at FortYukon and a meandering course, containing many sloughs, southwest of the bend at Fort Yukon. Most tributaries rise in surrounding uplands and mountains and have meandering courses throughthe flats.

Yukon-Kuskokwim Coastal Low

Kuskokwim Coastal Lowland is a triangulplain rising from sea level on its west margeast end. Low beach ridges, marked by lialong part of the west coast. The lowland is cstreams of extremely low gradient, many of former channels of the Yukon River. The Yuthe base of hills on the north side of the lowdelta into the Bering Sea. This region is dothaw lakes, many of them 10 or more miles percent of the lowland is lake surface.

Yukon-Tanana Upland—The Yuk

characterized by rounded even-topped ridgethese rounded ridges trend northwestward altitudes of 1,500-3,000 ft. The ridges are surugged mountains 4,000-5,000 ft in altitudepart have no preferred direction, are 3,000-5rise 1,500-3,000 ft above adjacent valleys. part are generally flat, alluvium floored, and within a few miles of headwaters. Streams drain to the Yukon River flow in narrow V

yons. Streams flow southward to the Tanana the Yukon River. No glaciers are in the regtion is underlain by discontinuous permafro
20 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Climate

The Yukon River Basin has a variable climate because of its

large size and range in altitude of the land surface. Climate zoneshave been broadly defined primarily by variations in precipitationand temperature (Searby, 1968; Hartman and Johnson, 1978).With the exception of the Yukon River Delta, the Yukon RiverBasin lies in the continental zone. Temperature extremes aregreater in this zone than in the other climatic zones. Air temperatures average about 22 °F. The Yukon Delta is located in the transition zone. Temperature in this zone averages about 27 °F, slightlyhigher than that in the continental zone.

Precipitation in the Yukon River Basin ranges from 10 to 130

in. annually (fig. 9). Averaged over the entire basin, the annual precipitation is approximately 19 in. The amount of precipitation isdirectly related to topography: high rugged mountains receive thegreatest amounts of precipitation and lowland areas receive theleast. About half of the precipitation falls as snow from Novemberthrough March. Snow may fall year-round in the high mountains,where much of it is stored for long periods in glaciers and icefields.

The climate in the Yukon River basin has been undergoing

significant long-term change. Tree-ring studies and 20th century

weather records indicate that the temperatures at Fairbanks and inthe surrounding area of Interior Alaska have been warmingsteadily since about 1840, with a brief interruption of this trendfrom about the mid 1940’s to the mid 1970’s (Juday and others,1998). During the period 1949

–96, the rate of warming has been

about 0.4 °F per 100 years. This warming also manifests itself asan increase in the length of the growing season and in earlier onsetof snowmelt and “break up” of the ice cover on the rivers. Precipitation at Fairbanks has been generally dec

years from 1906

–96 at a rate of about 1 in. p

are receding as a result of both warmer temdecreased precipitation. The 30-year record the Alaska Range indicates that ablation htion for 27 out of the past 32 years. Althrecords are not available for the Yukon Rivecier is commonly thought to be representatithe basin.

View of a valley glacier. Extensive systemare present in the Alaska Range and the Mountains. Although glaciers compose othe Yukon River Basin, they have signifrunoff characteristics.
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Figure 9. Precipitation regions in the Yukon River Basin (from Jones and Fahl, 1994).

Less than 10 inches per year10-1515-2020-3030-50Greater than 50

PRECIPITATION REGIONS

Newtok

Saint Marys Pilot Station

Russian Mission

Holy Cross

Grayling

Shageluk

Kaltag

Koyukuk Ruby

Huslia

Hughes

Alatna

Bettles

Anaktuvuk Pass

Wiseman

Tanana

Rampart Minto

Fairbanks

Nenana

Cantwell

Healy

Delta Junction

Dot Lake

Eagle

Dawson

Northway Junction

Beaver Creek

Destructi

Stew

Pel

M

Central

Circle

Birch Creek

Fort Yukon

Venetie

Arctic Village Old Crow

HooperBay

Chevak

Anvik

Kotlik

Alakanuk

Galena

Nulato

Allakaket

Beaver

StevensVillage

Livengood

Manley HotSprings

North Pole

Two Rivers

Big Delta

Tok

Boundary

Burwash L

MountainVillage

Tanacross

Fortymile

Ohogamiut
22 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Geology

Water-quality characteristics of surface water and ground

water are strongly affected by surficial and bedrock geology. Thegeology of the Yukon River Basin is complex and the interpretation of the geology is based on the concept that the Yukon RiverBasin is a mosaic of geologic terranes (Silberling and others, 1994;Gordey and Makepeace, 1999). A terrane is a body of rock ofregional extent that is bounded by faults, and whose geologic history is different from that of adjacent terranes. The terranes in theYukon River Basin represent blocks of the Earth’s crust that have

moved large or small distances relative to each other. The patternof terranes in the Yukon River Basin reflects the interactions ofoceanic crustal plates with the North American plate; large-scalelateral and rotational movements, rifting, and volcanic activityresult from these interactions.

Because of the size of the Yukon River Basin and the complexity of its geology, the following description is limited to the

rock type. The rocks range in age from Precambrian to Holoceneand consist of both unconsolidated deposits and consolidatedrocks (fig. 10). Major deposits are described in the following section (see figure 8 for locations of physiographic regions).

Cenozoic unconsolidated deposits are present in lowland

areas of the Yukon River Basin. The most prominent areas are theupper Porcupine River, the Yukon Flats, the Tanana-KuskokwimLowland, the Nowitna Lowland, the Tozitna-Melozitna Lowland,the Innoko Lowlands, and the Yukon Delta. The deposits are considered thick accumulations and consist pri

also include glacial deposits and locally incdeposits. In the Yukon Delta area, deltaic aQuaternary age are included in this map cat

Cenozoic sedimentary rocks are fou

the Alaska Range and near Eagle. These romarily of sandstone, siltstone, and shale, mudstone, and conglomerate. Cenozoic volcanic rocks ranging in colite to basalt are found in the foothills of t

Mountains, in the lower part of the Yukon Rand in scattered locations in the Koyukuk R

Cenozoic intrusive rocks ranging 

granite to quartz are found in the southeastRiver Basin near the base of the Wrangell

–S

the Coast Mountains.

Mesozoic sedimentary rocks are foun

eastern part of the Yukon River Basin, the uBasin, the Indian River Upland, and the Nuare mostly shale, siltstone, and sandstone, bustone and large deposits of coal.

Mesozoic volcanic rocks crop out in 

Yukon River Basin. Most of these rocks arpart of the basin near the Yukon Flats and Ksition of the rocks ranges from andesite to b
GEOLOGY

Figure 10. Geology of the Yukon River Basin (modified from Silbering and others, 1994; Gordey and Makepeace, 1999). 

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GlaciersWaterCenozoic unconsolidatedCenozoic sedimentaryCenozoic volcanicCenozoic intrusiveMesozoic sedimentaryMesozoic volcanicMesozoic intrusivePaleozoic sedimentary

Paleozoic metamorphic

Paleozoic volcanicPaleozoic intrusive

Precambrian
24 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Mesozoic intrusive rocks are present primarily in the southern part of the Yukon River Basin in British Columbia, the YukonTanana Upland, and the Kokrine-Hodzana Highlands. These rocks

are mostly in upland and mountainous areas and range in composition from granite to gabbro.

Paleozoic sedimentary rocks are present throughout the

Yukon River Basin. These rocks are found in the eastern part of thebasin in the Selwyn Mountains, along the northern flanks of theBrooks Range, in the eastern part of the Porcupine River Basin,and in the Innoko Lowlands. Composition of the rocks is mostlylimestone, shale, siltstone, and sandstone, but can include beds ofconglomerate, dolomite, and chert.

Paleozoic metamorphic rocks are prominent in the YukonTanana Upland. These rocks are primarily gneiss, schist, phyllite,

and quartzite, but locally include argillite, marble, and severalkinds of metasedimentary rocks.

Paleozoic volcanic rocks are scat

Yukon River Basin in small isolated areas nborder. Larger areas are found in the southeaThese volcanic rocks consist of sandstonechert.

Paleozoic intrusive rocks are foun

River near the Alaska/Canada border. These are faulted against lower Paleozoic and Precrocks. 

Precambrian rocks are found prima

central part of the Yukon River Basin. Rocslate, and siltstone.
Land Cover

Land cover influences a number of hydrologic factors, such

as snow accumulation, soil moisture depletion, surface runoff,infiltration, and erosion. These factors, in turn, can affect the waterquality of a particular stream or river. For example, certain typesof vegetation can prevent erosion, thus reducing the quantity ofsediment that enters a stream. Also, the composition of certaintypes of vegetation will in turn affect the chemistry of the waterquality.

Land cover also has a direct influence on the permafrost

because of the thermal properties that determine the quantity ofheat entering and leaving the underlying ground in which the permafrost exists. Vegetation exerts an indirect influence on permafrost by affecting climatic and other terrain features, which in turnhave a direct influence on the permafrost. These direct and indirectinfluences vary with time and space. 

A land classification system developed by the Alaska

Geospatial Data Clearinghouse (1998), describes eight types ofland cover, six of which compose about 90 percent of the YukonRiver Basin (table 3; fig. 11): needleleaf forest, tall and low shrublands, broadleaf forest, lichens, barren, and wet herbaceous. Theother two, dwarf shrublands and dry herbaceous, compose about 7percent of the basin. The remaining land cover is mainly ice, snow,and water. Specific descriptions of these land covers are takenfrom Talbot and Markon (1988).

Needleleaf forest (53.5 percent)

—

posed of two subclasses, closed needleleaf fleaf forest. Closed needleleaf forests are spruce on well-drained sites and along draion lowland sites. The tree canopy ranges frOpen needleleaf forests are similar to the cexcept that the tree canopy ranges from 25 

Table 3. Types and areas of land coveYukon River Basin[Data from Alaska Geospatial Data Clearinghouse

Type of land cover

(fig. 11)

Ar

Square miles 

Needleleaf forest 176,970 Tall and low shrublands 29,004 Broadleaf forest 28,627 Lichens 20,923 Barren 20,452 Wet herbaceous 19,960 Dwarf shrublands 12,875 Dry herbaceous 10,517 Ice and snow 9,211 Water 1,498 Other 765 

Total 331,000 
26 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

0

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Needleleaf ForestTall & Low ShrublandsBroadleaf ForestLichensBarrenWet HerbaceousDwarf ShrublandsDry HerbaceousIce/SnowRivers, streams & lakes

Figure 11. Land cover classes of the Yukon River Basin (from Alaska Geospatial Data Clearinghouse, 1998).

LAND COVER
Tall and low shrubland (8.8 percent)—These areas are

composed of two subclasses, closed and open. Closed tall and lowshrubland occurs primarily on upper hillslopes; mid-mountainslopes; or along rivers, streams, and small wet or waterloggedbasins. It may also be found on mid- to higher altitude slopes. Theshrub canopy is 75 percent or greater with heights ranging from 8to 59 in. Alders and willows are the more common species present.Open tall and low shrubland is similar to the closed tall and lowshrubland except that the shrub cover is generally less than 75 percent. Stands of open alder or small clumps of willow may be foundon a variety of mountains and altitudes, on upper slopes of roundedhills, and on steep mid-slopes of hills.

Broadleaf forest (8.6 percent)—Similar to needleleaf forests and to tall and low shrubland, the two subclasses of broadleaf

forest are closed and open. Closed broadleaf forests have tree canopies ranging from 60 to 100 percent. The primary tree species arewhite birch found on both hillsides and alluvial sites, and balsamfound only on alluvial sites. Open broadleaf forests have tree canopies ranging from 25 to 59 percent and are composed of the sametree species as the closed broadleaf forests. 

Lichens (6.3 percent)—These areas are common in the

Yukon River Basin, some of which cover extensive areas, and

most of which are associated with a numshrubs. 

Barren (6.2 percent)—These areas 

sand, gravel, rocks, and boulders of various with active flood plains, hill summits, and mplant cover is normally less than 5 perceamounts of lichens may be present.

Wet herbaceous (6.0 percent)—The

grasslands but are generally found in areas cmoist to saturated throughout the season. Thin low basins, tidal areas, and tundra areas impounded.

Dwarf Shrublands (3.9 percent)—

have few plants greater than 8 in. high and abirch. Lichens may also be present in mouareas. 

Dry Herbaceous (3.2 percent)—The

by sedges, normally with greater than 60 perhave other grass or grass-like plants as weMosses and lichens may also be present in v
28 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Soils

The formation of soils depends primarily on five factors:

type of parent material, climate, relief or topography, living organisms, and time (Singer and Munns, 1987). The type of soil dependson which factor is the most dominant. In the Yukon River Basin,type of material, climate, and relief have been the most dominantfactors in the development of soils. Soil type can affect water quality as precipitation infiltrates the soil, reacts with the minerals thatare present, and then discharges into a stream. Soil type and distribution are also factors that affect the amount of soil erosion.

In the soil taxonomy of the U.S. Department of Agriculture

(1975), soils are grouped at six levels or categories. The twobroadest categories are the order, followed by the more narrowlydefined category, the suborder. Of a possible 12 soil orders, 5 soilorders are found in the Yukon River Basin: Entisols, Gelisols,Inceptisols, Mollisols, and Spodosols (fig. 12). Gelisols are arecently developed new classification for permafrost soils (JoeMoore, National Resources Conservation Service, 1999). In addition, one other area, rough mountainous lands, is not classifiedas an order because it is largely unvegetated (Rieger and others,1979).

Entisols

—These are recently formed soils with little soil

horizon development and are found in areas of glacial outwash oralluvium. Suborders and soils of Entisols found in the Yukon RiverBasin are:

• Orthents Suborder

Lithic Cryorthents

—Soils with tex

fine sand. There is no stratification ois less than 20 in. from the top of the Typic Cryorthents

—Soils that are th

bedrock and have a mean annual teming. They have a wide range in textudominantly gray. The parent materithe braided beds of rivers that have a Pergelic Cryorthents

—Soils with m

tures below freezing and with no bedsoil is gravelly and has rapid internal frost is commonly many feet deep.Pergelic Ruptic-Histic Cryorthents—subject to frost-stirring processes to tthe surface is barren or covered only tundra plants. Commonly, these soilface patterns and thick organic mats

• Fluvents Suborder

Typic Cryofluvents

—Soils with alte

and silt loam. Many are underlain water and sand. Color is typically gr

Gelisols

—These are soils that have pe

40 in. of the soil surface and (or) have gelic 40 in. of the soil surface and have permafroGelic materials are mineral or organic soil mdence of frost churning in the active layer and (or) in the upper part of the permafrosare:
Entisols (Regosols)Gelisols (Cryosols)Inceptisols (Brunisols)Inceptisols/GelisolsMollisolsSpodosols (Podzols)

SOILS

Figure 12. Soils of the Yukon River Basin.

Rough Mountainous Land

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30 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

• Histels Suborder

Pergelic Cryofibrists

—Organic soils that have mean

annual soil temperatures below freezing. The permafrosttable is commonly less than 30 in. deep in these soils. Thesoils are composed of peat and the thickness of the peatranges from 16 in. to more than 10 ft.Histic Pergelic Cryaquepts

—These soils have thick accumulations of organic matter on the soil surface, commonly

in the form of a mat of slightly or partly decomposedmosses, sedges, and associated plants. Because the mat iseffective insulation against summer heat, the permafrosttable in these soils is normally very shallow. The upper partof the soils that thaws each summer and refreezes duringthe winter, known as the active layer, is almost constantlysaturated during the thaw period.Pergelic Cryochrepts

—Soils with mean annual temperatures below freezing, and a deep permafrost table. These

soils are gravelly.Pergelic Cryaquepts

—Soils that have many characteristics

in common with the Histic Pergelic Cryaquepts, but theynormally have somewhat longer periods during which thesoil is not completely saturated. They are commonly foundon alluvial plains, glacial moraines, or outcrops of coarsegrained rocks.

Inceptisols

—These are recently formed soils but, in contrast

to Entisols, have a greater degree of soil horizon development thanthe Entisols. At the present time, some Inceptisols (Andic Cryochrepts, Typic Cryochrepts) have some characteristics of Gelisols

and are classified as “Inceptisols/Gelisols.” Predominant suborders and soils are:

• Ochrepts Suborder

Aquic Cryochrepts

—Poorly draine

non-permafrost soils. Commonly, thonly during spring breakup, when smeltwater near the soil surface.Typic Cryochrepts

—Soils that are n

have the capacity to hold mineral elsoils have silt loam or loam texture alelly.

• Aquepts Suborder

Pergelic Cryaquepts

—Soils that hav

depth, but do not have thick peaty surface.Typic Cryaquepts

—Gray or olive-g

water table during most or all of the wide variety of texture, but are neveof sand or gravelly sand and are not 

• Umbrepts Suborder

Pergelic Cryumbrepts

—Soils that h

peratures below freezing. These sowith good surface drainage, in areas Typic Cryumbrepts

— Well-drained 

zons and mean annual temperatures soils will support low shrubby veget

Mollisols

—These are primarily thick, 

soils. In the Yukon River Basin, they occur derived from limestone or other basic rock, ders of Mollisols that are present are the Borsoil is Typic Cryoborolls which is a bro

drained soil formed in nonacid material. Thsoil is found in the Yukon River Basin is juFlats.
Spodosols—These soils have light-colored surface horizons, and organic and aluminum-rich subsurface horizons. Suborders of Spodosols that are present are the Orthods. The

predominant soil is Typic Cryorthods, which have moderate accumulations of organic carbon in the horizon and no permafrost.

Aluminum and iron are also present in the soil.

The Canadian soil classification system is similar, though

not identical to the U.S. soil classification system. In the Canadiansystem, an order is followed by the more narrowly defined category, the great group (Agriculture Canada, 1976). Of a possiblenine orders, four are present in the Canadian part of the YukonRiver Basin (similar U.S. classification in parenthesis):

Regosols (Entisols)—These soils either have no horizon

development or have soil horizon development insufficient to beclassified in any of the other orders.

Cryosols (Gelisols)—These mineral or organic soils have

perennially frozen material within 3 ft of the surface in some partof the soil body. The mean annual soil temperature is less than32 °F. Their maximum development occurs in organic and poorlydrained, fine textured materials. Three great groups are associatedwith this order and are all found in the Yukon River Basin.

Turbic Cryosols—Generally composed of mineral soils

that display marked frost action such as frost heaving, andgenerally occurring on patterned ground.Static Cryosols—Mineral soils without noticeable frostaction.Organo Cryosols—Organic soils.

Brunisols (Inceptisols)—These soils have horizons that are

sufficiently developed to be excluded from the Regosolic order butare not sufficiently developed to be classified in other orders. Two

great groups are found in the Yukon R

Brunisols, which are soils with horizons lessisting of organic matter and minerals, awhich are soils similar to Dystric Brunisols 

Podzols (Spodosols)—These soils h

consisting of organic matter, iron, and alumgroups, Humo-Ferric Podzolic, is found in tThe upper 4 in. of this soil contains betworganic carbon and 0.6 percent or more extriron.

View of the Interior Bottomlands ecoregposed of flat to nearly flat bottomlands athe Yukon River Basin. These bottomlathaw and oxbow lakes.
32 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Permafrost

Permafrost is defined exclusively on the basis of temperature, not on the presence of ice. A mass of material is considered

to be permafrost if it has a temperature continually at or below 32°F for 2 or more years (Ferrians, 1965). Permafrost is present to alarge extent in the Yukon River Basin (fig. 13). Ferrians (1965) andBrown and others (1997), designated six regions of permafrost inthe Yukon River Basin (fig. 13): (1) generally underlain by continuous permafrost

—16 percent, (2) generally underlain by discontinuous permafrost

—40 percent, (3) generally underlain by

moderately thick to thin permafrost (50 to 600 ft)

—24 percent, (4)

underlain by discontinuous permafrost—6 percent, (5) generallyunderlain by numerous isolated masses of permafrost—5 percent,and (6) sporadic masses of permafrost—9 percent. Because thermal data for permafrost regions in Alaska and Canada are limited,some of the regions are combined into one.

Permafrost has a very low permeability and commonly acts

as a barrier to infiltration and as a confining layer to aquifers.Because it is a barrier to infiltration, permafrost increases the likelihood of flash floods in streams draining permafrost areas. Thistendency for rapid runoff is partly offset by the common presenceof an organic mat, which can retard runoff briefly. Once theorganic mat is saturated, however, floods occur very quickly.

Even in the zone of continuous permafrost, ground water can

find paths through "taliks," or unfrozen zones in the permafrost.Taliks commonly occur under large lakes, under large rivers, andin areas where warm summer streamflow infiltrates into coarsealluvium. Taliks can also advect large amounts of heat into anaquifer.

If permafrost melts, the upper layers o

well aerated. Even if permafrost remains as the shallow soils that thaw and freeze each thaw more deeply and develop a thicker umicrobes increasingly oxidize the organic the soils. This increased respiration releases dissolved carbon, into a stream and the atmdissolved organic carbon (DOC) could affecmunities at all trophic levels that rely on DO

The melting of the permafrost may inc

fers, thus increasing base flow in streams. Brecharge, melting of permafrost will also dflows. Wetlands, which occupy about 30 River Basin (fig. 14), could be affected anfowl habitat in the Yukon Flats and Yukon are lands transitional between terrestrial awhere the water table usually is at or near tland is covered by shallow water (Cowardin 

Another natural factor that can affe

Wildfires disturb thousands of acres of lanBasin each year (fig. 15). Foote (1976) has fire cycle range from 70 to 130 years. Aftesurface conditions results in soil warming depths. The soil may become well drained aa perched water table. Thus, the hydrology were once wetlands become completely dra
Newtok

Saint Marys Pilot Station

Russian Mission

Holy Cross

Grayling

Shageluk

Kaltag

Koyukuk Ruby

Huslia

Hughes

Alatna

Bettles

Anaktuvuk Pass

Wiseman

Tanana

Rampart Minto

Fairbanks

Nenana

Cantwell

Healy

Delta Junction

Dot Lake

Eagle

Dawson

Northway Junction

Beaver Creek

Destructio

Stewa

Pell

C

Ma

Central

Circle

Birch Creek

Fort Yukon

Venetie

Arctic Village Old Crow

HooperBay

Chevak

Anvik

Kotlik

Alakanuk

Galena

Nulato

Allakaket

Beaver

StevensVillage

Livengood

Manley HotSprings

North Pole

Two Rivers

Big Delta

Tok

Boundary

Burwash L

Figure 13. Permafrost regions of the Yukon River Basin (modified from Ferrians and others, 1965, and Brown and others, 1

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Generally underlain by continuous permafrostGenerally underlain by discontinuous permafrostGenerally underlain by moderately thick to thin permafrostUnderlain by discontinuous permafrostGenerally underlain by numerous isolated masses of permafrostSporadic masses of permafrost

PERMAFROST REGIONS

Ohogamiut

MountainVillage

Tanacross

Fortymile
34 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

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WetlandsLakes, rivers and streams

WETLANDS

Figure 14. Wetland areas of the Yukon River Basin (modified from Fretwell and others, 1996).
Figure 15. Areas of forest fires in the Yukon River Basin (from T. Hammond, Bureau of Land Management, 1999, written commAffairs Canada, 1999).

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1950-1959

1960-1969

1970-1979

1980-1989

1990-1998

FOREST FIRES
36 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Ecoregions

Ecoregions are areas with common ecological settings that

have relatively homogeneous features such as natural vegetation,geology, mineral availability from soils, physiography, and landuse and land cover (Omernik, 1995). The Yukon River Basin hasbeen classified into 20 ecoregions (Gallant and others, 1995; Ecological Stratification Working Group, 1995) (table 4; fig. 16). TheInterior Forested Lowlands and Uplands ecoregion and the Interior Highlands ecoregion are the most dominant ecoregions in thebasin. Descriptions of the ecoregions follow and are taken fromGallant and others and the Ecological Stratification WorkingGroup.

Alaska Range

—The mountains of south-central Alaska, the

Alaska Range, are very high and steep. This ecoregion is coveredby rocky slopes, icefields, and glaciers. Much of the area is barrenof vegetation. The Alaska Range has a continental climate, butbecause of the extreme height of many of the ridges and peaks,annual precipitation at higher altitudes is similar to that measuredfor some ecoregions having maritime climate.

Climate is influenced by the mountains. Weather data for the

region indicate that winter daily low temperatures average about -12 °F and daily high temperatures about 27 °F at lower altitudes.Summer daily low temperatures average about 36 °F and dailyhigh temperatures about 64 °F. Mean annual precipitation in lowlands is approximately 15 in. and snowfall ranges from 59 to 120

in. Average annual precipitation for the mountain peaks is estimated at 80 in. and snowfall is estimated at 400 in.

The terrain of the ecoregion consists of steep, rugged mountain ridges separated by broad valleys. Altitudes are 2,000 ft in the

lower valleys and commonly rise to greater than 13,000 ft onmountain peaks. Slope gradients, which are almost always greater

Table 4. Areas of ecoregions in the Yukon R

Ecoregion

(fig. 16)

Square m

Alaska Range 12,Boreal Mountains and Plateaus 5,Brooks Range 21,Eagle Plains 6,Interior Bottomlands 32,Interior Forested Lowlands & Uplands 70,Interior Highlands 55,Mackenzie Mountains 5,Ogilvie Mountains 12,Old Crow Flats 2,Pelly Mountains 8,Ruby Ranges 5,Selwyn Mountains 9,Subarctic Coastal Plains 11,Wrangell Mountains 9,Yukon Flats 12,Yukon Plateau Central 10,Yukon Plateau North 21,Yukon Southern Lakes 12,Yukon Stikine Highlands 3,Other 

Total 330,
Figure 16. Ecoregions of the Yukon River Basin (modified from Gallant and others, 1995 and Ecological Stratification Working 

Alaska RangeBoreal Mountains and PlateausBrooks RangeEagle PlainsInterior BottomlandsInterior Forested Lowlands & UplandsInterior HighlandsMackenzie MountainsOgilvie MountainsOld Crow Flats

Pelly RubSelwSubWraYukoYukoYukoYukoYukoOthe

ECOREGIONS

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38 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

than 5 degrees on hillslopes, exceed 25 degrees on some mountains. The part of the ecoregion contained in the Yukon RiverBasin is part of a broad syncline having Cretaceous rocks in thecenter and Paleozoic and Precambrian rocks on the flanks. Anextensive system of valley glaciers still exist. Permafrost is discontinuous in this ecoregion; however, its full extent is unknown.Streams are swift and braided, and most headwaters are in glaciers. 

Much of the ecoregion consists of rocky slopes, icefields,

and glaciers. Where soil development has occurred, principal soilsare Lithic Cryorthents, Pergelic Cryaquepts, Pergelic Ruptic-Histic Cryorthents, Typic Cryaquepts, Pergelic Cryumbrepts, andTypic Cryumbrepts. Most soils are stony and shallow over bedrock, or bouldery colluvial, or glacial deposits. Soils on lowerslopes and in valleys are typically poorly drained, and have a shallow permafrost table. Most of the region is barren of vegetation.Dwarf scrub communities are most common where vegetationdoes occur, growing on well-drained, windswept sites. More protected slopes provide moist to mesic sites that support low or tallscrub communities. Open needleleaf forests and woodlands occuron well-drained sites in some valleys and on lower hillslopes.

Boreal Mountains and Plateaus

—This ecoregion covers

most of northwestern British Columbia and a small area in theextreme southwestern part of the Yukon Territory. The ecoregionis composed of a complex of rugged mountains, high plateaus, andlowlands. Temperature and precipitation vary with altitude. Theclimate tends to be more moderate in the western half of the ecoregion and becomes more continental towards the eastern part. Thetypical mean annual temperature for the area is approximately 28°F with a summer mean of 50 °F and a winter mean of 5 °F. The

mean annual precipitation ranges from 16 to 28 in. 

The vegetation is a complex mosaic, ranging from alpine

vegetation and bare bedrock at higher mountain altitudes to alpine

fir with some white spruce and deciduous salpine forests at middle altitudes in the southern Omineca Mountains. Closed canopied pine, and white and black spruce dominate tStikine and Yukon Plateaus. The most comFerric Podzolic soils on upland sites in suGray Luvisolic with Dystric Brunisolic soiregions. Permafrost with low ice content occnorthern part of the ecoregion and is confinin the southwest.

Brooks Range

—The Brooks Range 

several groups of rugged deeply dissected muplifted sedimentary rock. Altitudes of the from 2,600 to 7,900 ft. An arctic climate regslopes maintain a sparse cover of dwarf scruout the mountains. The ecoregion is influenA weather station located at Anaktuvuk Pa2,500 ft. Winter temperatures average a dai

and a daily maximum of -8 °F, whereas 

average a daily minimum of 37 °F and a daiMean annual precipitation at Anaktuvuk Pasnowfall is 63 in.

Continuous thick permafrost underli

principal soils of the Brooks Range are Pergelic Cryumbrepts, and Lithic Cryortwere formed from local colluvium, whereas erally developed from glacial till. Soils throtypically have poor drainage because of the mafrost. Because of highly erodible hillslosoils, high winds, and harsh climate in this cover is sparse and generally limited to valopes. Drier sites support dwarf scrub comm
Eagle Plains

—This ecoregion is almost an entirely unglaciated rolling plateau; it includes the Eagle Plain, Bell Basin, and

part of the Porcupine Plateau. The mean annual temperature forthe area is 20 °F with a summer mean of 50 °F and a winter meanof -10 °F. Mean annual precipitation ranges from 16 to 18 in. Thevegetative cover of this ecoregion is typical subarctic forest. Open,very stunted stands of black spruce and tamarack with secondarystands of white spruce and ground cover of dwarf birch, willow,heath shrubs, cottongrass, lichen, and moss are predominant. 

On the southern part of the ecoregion, long, even-topped

ridges along the Porcupine Plateau have broad, gently roundedsummits typical of unglaciated terrain. Relief is low; altituderanges from 1,000 to 2,000 ft and the highest peak is 3,000 ft. Theplain is underlain by Cretaceous and older sandstone and shale. Adiscontinuous veneer of eolian material covers much of the morestable upper slopes in the region. Permafrost is continuous. Highice content permafrost in the form of ice wedges is common inbasin areas. Turbic Cryosols on loamy, inclined, and dissected colluvial material are most common. Regosols on gravelly alluvialmaterial and Dystric Brunisols on sandy colluvium occur on nonpermafrost sites. Characteristic wetlands covering 25 to 50 percentof the land area consist of peat plateau bogs, palsa bogs, and ribbedand horizontal fens.

Interior Bottomlands

—This ecoregion is composed of flat

to nearly flat bottomlands along large rivers of interior Alaska.The bottomlands are dotted with thaw and oxbow lakes. Soils arepoorly drained and shallow, commonly over permafrost. Predominant vegetation communities include forests dominated by spruceand hardwood species, tall scrub thickets, and wetlands. Theecoregion is characterized by a continental climate. The bottomlands in the west receive more annual precipitation than those inthe east. Annual precipitation ranges from 11 to 16 in., and annual

snowfall ranges from 37 to 80 in. Average datures in winter range from -27° F to -15 °F

mum winter temperatures range from -8 

temperatures have lows of about 45 °F and 

The terrain of the ecoregion is typifie

bottomlands, with some inclusions of local bottomlands have a slope gradient of less thrange from 1,400 ft in the west to 2,000 ft ieolian deposits of mixed origin cover most wash gravel and morainal deposits are in sostreams and side sloughs are prevalent and lakes are numerous.

Principal soils are Histic Pergelic 

Cryaquepts, Aquic Cryochrepts, Typic CrCryofluvents. On flat areas away from the soils are shallow over permafrost, poorly always wet. On the slightly higher levees, and permafrost is deep or absent. Soils witsusceptible to alteration upon disturbancNeedleleaf, broadleaf, and mixed forest staof sites in the Interior Bottomlands ecoregionities form thickets on flood plains. The wvariety of wetland communities, such as graminoid herbaceous meadows, and wmarshes and meadows.

Interior Forested Lowlands and U

gion has a continental climate, with short wavery cold winters. Because this ecoregion iand precipitation vary widely from west to efall and snowfall generally increase with while affected by altitude, is also influenceocean; maximum summer temperatures incr
40 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

and minimum winter temperatures decrease in the same pattern.Mean annual precipitation over most of the region ranges from 10to 22 in. with contributions from snowfall ranging from 49 to 81in. Most precipitation occurs during summer, mainly as a result ofconvective storms. Average minimum winter temperatures rangefrom 0 °F in the west to -31 °F in the east; average maximum winter temperatures range from 12 °F in the west to -8 °F in the east.

Summer temperatures, ranging from 46 to 72 °F with daily fluctuations of 15 to 20 °F, have less regional variation than winter temperatures. 

The terrain of the ecoregion consists of rolling lowlands, dissected plateaus, and rounded low to high hills. Most of the region

lies between altitudes ranging from sea level to 1,600 ft, but somehills rise more than 2,300 ft. Slope gradients are generally from 0to 5 degrees. The predominant geologic formations are derivedfrom Mesozoic and Paleozoic sedimentary rocks, but extensiveareas of volcanic deposits also occur. The region is surficiallymantled by undifferentiated alluvium and slope deposits. Streamsoriginating from within this ecoregion tend to be short, whereaslarger and longer streams originate from adjacent glaciated mountainous regions. Although thaw lakes and oxbow lakes occurthroughout the ecoregion, lakes are not a predominant landscapefeature. The western part of the ecoregion is underlain by thin tomoderately thick permafrost, and the eastern part has a discontinuous distribution of permafrost.

Dominant soils are Histic Pergelic Cryaquepts, Pergelic

Cryaquepts, Aquic Cryochrepts, Pergelic Cryochrepts, TypicCryochrepts, Typic Cryorthents, and Pergelic Cryumbrepts. Theinterrelationships among permafrost, surface water, fire, hillslopeaspect, and soil characteristics result in a finely textured, complexpattern of vegetation across the ecoregion. Soil temperatures maydiffer greatly from air temperature, so patterns in vegetation may

not correspond with expected site conditioleaf, and mixed forests occur over a variety shrub communities grow in areas of newly eas flood plains, streambanks, drainagewaysburned or otherwise disturbed areas, and scrub communities occur in moist areas slopes. The wettest sites support tall scrubogs, or scrub-graminoid communities. Recplay a succession of recovery stages that incceous communities, mesic graminoid herbscrub communities, and broadleaf, needlele

Interior Highlands

—This ecoreg

rounded, low mountains, often surmounAlthough no long-term weather data are avalizations can be made regarding temperatFirst, an orographic effect on precipitation creceive more precipitation than the surrouareas. Second, summer temperatures probatude.

Altitudes range from 1,600 ft in the 

4,900 ft on the peaks. Slope gradients comm15 degrees. The mountains have much more the surrounding hills of the Interior ForUplands ecoregion. Geologic formations coPrecambrian metamorphic rocks, felsic volsive rocks. The northern part of the ecoregiotinuous permafrost.

Dominant soils are Histic Pergelic Cr

chrepts, Pergelic Cryumbrepts, Lithic Cryororthods. Most soils are shallow, formed in material weathered from local rock. The pelow and soils are poorly drained; however, 
shallow over bedrock for ground ice to form. Soils with permafrostare very susceptible to alteration upon disturbance of the organicmat because of the relatively warm (more than 29 °F) permafrost

temperature. Organic mat disturbance, such as from wildfires, canresult in warmer soil temperatures, lowered permafrost tables, andsignificant changes in soil physical properties and hydrology. Thehighest altitudes are barren of vegetation. Dwarf scrub communities, dominated by species of mountain avens, ericads, and willow,are widespread in sites exposed to wind. Lower altitudes are generally more protected from wind and have a denser vegetationcover that can include open needleleaf forests and woodlands.Areas of poor soil drainage support mesic graminoid herbaceouscommunities.

Mackenzie Mountains

—This extremely rugged heterogeneous ecoregion spans the Yukon Territory/Northwest Territories

border from Alaska to the Mackenzie Valley. It includes the Ogilvie and Wernecke Mountains in its westernmost section, the Backbone Ranges in its interior, and the Canyon Ranges to the east. Theeastern ranges of the Mackenzie Mountains that lie in the rainshadow of the higher Selwyn Mountains to the west are alsoincluded. The ecoregion shows evidence of localized alpine andvalley glaciation. The mean annual temperature for the area isapproximately 23 °F with a summer mean of 48 °F and a wintermean of -2 °F. Mean annual precipitation is highly variable withthe highest amounts, greater than 24 in., occurring in the southwestern part of the ecoregion. Moving westward towards Alaskaand the southern Ogilvies, precipitation decreases to approximately 16 in. 

The region is characterized by alpine tundra at higher altitudes and subalpine open woodland vegetation at lower altitudes.

Alpine vegetation consists of lichens, mountain avens, intermediate to dwarf heath shrubs, sedge, and cottongrass in wetter sites.

Barren talus slopes are common. Subalpine discontinuous open stands of stunted white alpine fir in a matrix of willow and dwarf bitinuous and of low ice content in most of ecoregion. Turbic Cryosols with some DRegosols occur on steeply sloping colluvium

Ogilvie Mountains

—The Ogilvie M

located along the eastern edge of the Yukon of flat-topped hills eroded from a former plaslopes built up from mountains that are muformer stature. Karst topography is commonherbaceous communities and tall scrub cospread throughout the region.

The ecoregion has a continental cl

weather stations are located in this region and temperature characteristics are interporegion. These interpolations indicate that aabout 20 in. in the hills to about 26 in. in Annual snowfall ranges from 51 to 81 in. acwinter temperatures range from lows of -2

and daily summer temperatures range from 

The terrain of the region consists o

topped hills eroded from a former plain. Peing across broad valleys to the foothills of mountains, are characteristics of the plateausedimentary rock occur in many localities. Wexposed at higher altitudes, and talus and rumountainsides. Altitudes range from 2,900 fand slope gradients are generally less than 5 composed of metamorphic and sedimentary mite, phyllite, argillite, limestone, shale, 
42 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

conglomerate. Karst topography is common and most of theregion is underlain by permafrost.

Principal soils of the Ogilvie Mountains ecoregion are Histic

Pergelic Cryaquepts, Typic Cryochrepts, and Pergelic Cryorthents. Soils were formed in gravelly or stony material weatheredfrom local rock. Soils in valleys were formed from deep, loamy,alluvial sediments from the surrounding uplands. Vegetation isdominated by mesic graminoid herbaceous communities and tussock-forming sedges. Needleleaf, broadleaf, and mixed forestcommunities occupy lower hillslopes and valleys. Tall scrub communities occur extensively at lower altitudes and can extend abovethe timberline.

Old Crow Flats

—Old Crow Flats is the largest wetland

complex in the Yukon Territory. Located on the Old Crow Riversystem north of the Arctic Circle, the Flats contain more than2,000 ponds and marshes ranging in size from 100 ft2 to 18 mi2

.

The area is an important breeding and molting ground for 500,000water birds. Waterfowl, muskrats, and other wildlife of the Flatsare of great importance to the Native residents.

The ecoregion is unglaciated and incorporates the area of

wetlands and lakes that occupy a glaciolacustrine plain that makesup the lowest part of the Old Crow River Basin. This level, lowrelief ecoregion, locally referred to as “The Flats” lies at about1,000 ft. The climate is strongly continental. Mean monthly airtemperature ranges are as extreme as anywhere in North America.Short warm summers contrast with long very cold winters. Themean annual temperature for the area is approximately 14 °F witha summer mean of 46 °F and a winter mean of -17 °F. Mean annualprecipitation ranges from 8 to 10 in. 

Wetlands, which cover most of the ecoregion, are made up of

polygonal peat plateau bogs with basin fens and locally occurring

shore fens. Organic Cryosols are the most cBetter drained parts of the land support opeof black spruce and tamarack with minor sand ground cover of dwarf birch, willow, cmoss. Static Cryosols on sandy alluvial matsols on loamy, ice-rich lacustrine material soils of the ecoregion. Permafrost is conticontent in the form of ice wedges and mass

Pelly Mountains

—This ecoregion e

and northern Cassiar Mountains spanninbia/Yukon Territory border. The mean annuarea is approximately 37 °F with a summewinter mean of -1 °F. Mean annual precipvarying with altitude. Boreal forests of whitlodgepole pine, and aspen cover the lower aMuch of the ecoregion lies above the treelinby alpine tundra communities of lichensbirch, and willows. Grasses, sedges, cottongoccupy wet sites. Open-growing black aalpine fir are prevalent in the subalpine regi

The Pelly and Cassiar Mountains, co

Mesozoic and Paleozoic strata, are of modering from about 4,900 ft to the highest peak greater in the Pelly Mountains than in the Cmafrost is sporadically distributed. Dystric are codominant in the ecoregion. Dystric Brwith coarse igneous rocks at higher altitudsandy loam morainal parent materials are Brunisols. Turbic Cryosolic soils are found some poorly drained areas.
Ruby Ranges

—This ecoregion covers the Kluane

River–Kluane Plateau. The climate is characterized by short coolsummers and long cold winters. Winter temperature inversions arecommon, giving milder temperatures at higher altitude. Maritimeair from the Gulf of Alaska periodically invades the ecoregion during the winter to produce mild spells with near-thawing temperatures. The mean annual temperature for the area is approximately27 °F with a summer mean of 50 °F and a winter mean of 2 °F.

Mean annual precipitation ranges from 10 to 12 in.

Northern boreal forests occupy lower slopes and valley bottoms. Open white and black spruce occur in a matrix of dwarf willow, birch, heath shrubs, and some lodgepole pine. Black spruce,

scrub willow, birch, and mosses are found on poorly drained sites.Alpine fir and lodgepole pine occur in higher subalpine sections,whereas the highest altitudes consist of sparsely vegetated alpinecommunities of mountain avens, dwarf willow, birch, shrubs andmosses. The terrain consists of rolling to undulating hills above2,900 ft and the highest peak is 7,560 ft.

The most common soils in this ecoregion are Eutric

Brunisols on sandy loam morainal or colluvial materials. Regosolic soils are associated with active deposition of gravelly fluvioglacial outwash materials on braided flood plains. Volcanic ash fromthe 1,300-year-old White River eruption is up to 40 in. thick onlower slopes. In these cases, the soils are classified as either Regosols or Regosolic Turbic Cryosols, depending on the presence orabsence of permafrost. Permafrost is extensive and discontinuousover most of the ecoregion decreasing to sporadic along the western side of the ecoregion.

Selwyn Mountains

—This ecoregion is located in the Selwyn and southern Mackenzie Mountains that span the Yukon Territory/Northwest Territories border. For the most part, this is a

rugged mountain wilderness, a northern extension of the Rocky

Mountains. Climate conditions vary witannual temperature for major valley system°F with a summer mean of 49 °F and a winteannual precipitation is highly variable rangialtitudes on the perimeter of the ecoregion utudes. 

The ecoregion is characterized by al

altitudes and by subalpine open vegetatiAlpine vegetation consists of crusoe lichdwarf willow, and heath shrubs. Sedge and ated with wetter sites. Barren talus slopes avegetation consists of discontinuous open sspruce, and occasional alpine fir and lodgepwillow and dwarf birch. Sedge, cottongrasswet sites. The Selwyn Mountains, which hglaciated, are composed of Paleozoic anintruded by granite stocks. They are divided broad, northwesterly trending valleys. Some and valley glaciers. Permafrost is extensivthe western part and continuous with low ice part of the ecoregion. Dystric and Eutric Bruvioglacial, and morainal veneers and blankeregion. Static and Turbic Cryosols with Dyssols are developed on higher altitude, steep

Subarctic Coastal Plains

—This ec

Yukon River Delta area. Flat, lake-dotted cdeltas are characteristics of the region. Strand serpentine meanders. Soils are wet and shallow, providing conditions for wet gramimunities, the predominant vegetation type.

Climate in this ecoregion is transitio

and continental influences. In general, the 
44 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

region has warmer temperatures and receives more precipitationthan the northern part. Average annual precipitation is about 20 in.and annual snowfall is about 59 in. Temperatures in winter rangefrom average daily minimums of -13 °F to average daily maximums of 14 °F. Average daily temperatures in summer range from

a minimum of 43 °F to a maximum of 55 °F.

The terrain of this ecoregion consists primarily of flat poorly

drained coastal plains with shallow permafrost tables. Low hills ofbasalt surmounted by cinder cones and broad shallow volcaniccraters occur in some locations, creating a range in regional altitude from sea level to more than 400 ft. Slopes in the plains aregenerally less than 1 degree. The region is predominantly coveredby older coastal deposits of interstratified alluvial and marine sediments.

Predominant soils are Histic Pergelic Cryaquepts and

Pergelic Cryofibrists. Soils are shallow over permafrost and areconstantly wet. Soils have formed from stratified silty and sandyalluvial deposits that, in many areas, have additionally incorporated deposits of volcanic ash and loess. Standing water is almostalways present in the ecoregion and wet graminoid herbaceouscommunities, such as wet meadows and bogs, predominate in saturated soils. Peat mounds, barren sand dunes, and volcanic soilssupport dwarf scrub communities dominated by ericaceous species.

Wrangell Mountains

—The Wrangell Mountains ecoregion

consists of steep, rugged mountains of volcanic origin that areextensively covered by ice fields and glaciers. Most slopes are barren of vegetation. Dwarf scrub tundra communities, consisting ofmats of low shrubs, grasses, and lichens, predominate where vegetation does occur.

Climate is primarily affected by contin

ter low temperatures average -29 °F, and w°F. Mean summer low temperature is 37 °high is 72 °F. Average annual precipitatioannual snowfall is about 69 in. Higher altituof precipitation annually, including 100 in. 

The Wrangell Mountains ecoregion re

of shield and composite volcanoes of Cenonic formations lie over Paleozoic and Mesovolcanic rocks. The terrain is steep and rugents exceed 7 degrees and many surpass 15 dat 2,000 ft, most of the largest peaks are 13several peaks exceed 16,000 ft. Extensive permafrost is discontinuous. 

Much of the landscape consists of st

fields, and glaciers. Soil development has soils that are shallow over bedrock or bousoils have formed in very stony and graveSoils in valleys and on footslopes have forma thin mantle of volcanic ash or loess in ssoils are Lithic Cryorthents, Typic Cryortchrepts, and Pergelic Cryumbrepts. Most slare barren of vegetation. Dwarf scrub cowhere vegetation does occur, growing on sites. Tall scrub communities occur along dplains. Broad ridges, valleys, and hilly morasupport needleleaf forests dominated by whiforests dominated by paper birch or aspen.

Yukon Flats

—The Yukon Flats ecore

marshy basin floor in east-central Alaska braided and meandering streams, numerlakes, and meander scars. In many ways, th
to the Interior Bottomlands region except that the Yukon Flatsecoregion differs in climatic characteristics. Forests dominated byspruce and hardwood species, tall scrub communities, and wetgraminoid herbaceous communities are the predominant vegetation type.

The Yukon Flats ecoregion has a continental climate. The

mountains surrounding the ecoregion isolate it from the weathersystems affecting the neighboring regions. Consequently, summertemperatures tend to be higher than at other places of comparablelatitude and winter temperatures tend to be colder. Average dailytemperatures in winter range from lows of about -29 °F to highs of

about -11 °F. Average daily temperatures in summer range fromlows of just about freezing to highs of about 72 °F. Annual precipitation is low, averaging 6.5 in. and average snowfall is 45 in.(water content of about 4 in.). Local precipitation is not sufficientto maintain water levels in many lakes. Levels are primarily maintained by the yearly flooding of the region by the Yukon River thataccompanies spring breakup of ice (Gallant and others, 1995).

The central part of the ecoregion is flat, whereas the edges of

the region range from 300 ft to more than 600 ft. Slope gradient isgenerally less than 1 degree in the center and 1 to 2 degrees at theedges. The region is mantled by Quaternary-age alluvial deposits.The Yukon River drains the ecoregion, assisted by numerousmeandering and braided tributaries and side sloughs. Permafrost ispresent in most areas, except beneath rivers and large thaw lakes.Thaw lakes and oxbow lakes are abundant. 

Principal soils are Histic Pergelic Cryaquepts, Pergelic

Cryaquepts, Aquic Cryochrepts, and Pergelic Cryochrepts. Mostsoils were formed from silty alluvium and loess from the floodplains of the Yukon River. On flat areas away from the main riverchannels, soils are poorly drained, are commonly overlain by peat,and have a shallow permafrost table. Soils on natural levees are

better drained and consist of silty and sandleaf, broadleaf, and mixed forests are widesrepresenting an array of soil drainage charthickets occur on alluvial deposits subject Tall scrub swamps and wet graminoid heroccupy the wettest sites.

Yukon Plateau Central

—This ecor

ward from Lake Laberge to the lower StewYukon. The Yukon Plateau Central ecoregioeral groups of rolling hills and plateaus sepbroad valleys. The climate is cold and semitemperature for the area is approximately 

mean of 54 °F and a winter mean of -2 °F. M

tion ranges from 10 in. in the southern areain. at higher altitudes in the north and east. 

White and black spruce form the most 

Black spruce is usually dominant in wetter commonly invades burnt-over areas and vplaces, alpine fir forms the treeline but is associated with white spruce and occasionSedge tussocks and sphagnum are commobirch and willow occur in subalpine sectiontreeline. A significant vegetative feature opresence of extensive grasslands on all lowslopes. The forests suffer frequently from such that series of ecological communities 

Altitudes are above 3,300 ft, except f

which lie below 2,000 ft in the northwestertains reach heights of 4,900 ft. Eutric Brunion steeply sloping, ridged-to-hummocky, sandy fluvioglacial material, are dominant iof the ecoregion is covered by a veneer of 
46 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

12 in. thick. Permafrost is discontinuous to sporadic with high icecontent associated with fine-textured valley deposits. Turbic Cryosols are confined to wet depressions and beneath mature forestson lower, north-facing slopes. 

Yukon Plateau North

—This ecoregion lies within the

Stewart, Macmillan, and Pelly Plateaus and the southern foothillsof the Selwyn Mountains. The terrain includes rolling uplands,small mountain groups, and nearly level tablelands dissected bydeeply cut, generally broad, 

U-shaped valleys. The Tintina Trench,

a straight, steep-sided valley 3-12 mi wide, traverses the ecoregions from southeast to northwest. The mean annual temperaturefor the area is approximately 25 °F with a summer mean of 51 °F

and a winter mean of -4 °F. Mean annual precipitation ranges from12 in. in the major valleys up to 24 in. in the mountains to thenortheast. 

Northern boreal forests exist at altitudes up to 4,900 ft. White

spruce in a matrix of dwarf willow, birch, heath shrubs, and occasionally lodgepole pine, form extensive open forests, particularlyin the northwestern part of the ecoregion. Black spruce, scrub willow, birch, and mosses are found on poorly drained sites. Alpinefir and lodgepole pine occur in higher subalpine sections. Extensive discontinuous permafrost with a medium ice content is widespread, decreasing to sporadic discontinuous permafrost along thesouthwestern edge of the region. Turbic Cryosolic and EutricBrunisolic soils predominate, and occasional pockets of DystricBrunisols occur on coarse-textured morainal and fluvioglacialmaterials.

Yukon Southern Lakes

—This ecoregion extends from

Lake Laberge south to the boundary with British Columbia. Theclimate is cold and semiarid. In major valleys, the mean annualtemperature is about 28 °F with a summer mean of 50 °F and awinter mean of 2 °F. Lying within the rain shadow of the St. Elias

Mountains, mean annual precipitation rangthe major valleys. 

Boreal forests are composed of open w

pole pine intermixed with aspen. South-factude are occupied by grassland communitieabove 4,000 ft support open forest communispruce, and some lodgepole pine. Most of t4,900 ft in altitude, but a few peaks are Underlain by Mesozoic sedimentary strata morphic slates and schists, the topography isected plateaus and rolling hills. Eutric Bruloam and rolling morainal to steep colluvial Low ice content permafrost occurs in a sppattern. Cryosolic soils are scattered througsome poorly drained areas and on north-fac

Yukon Stikine Highlands

—This ecor

climate transition from coastal to interior coern British Columbia and southern Yukonwithin the rain shadow of the Coast Moudecreases moving inland, and temperathroughout the year by the influence of mamean annual temperature for the area is appa summer mean of 50 °F and a winter mean 

precipitation ranges from 20 to 24 in. The eof a combination of three distinct vegetatiodominated by low-growing heather, dwarf and lichen; subalpine forests of alpine fir, occasional Engelmann spruce; and closed band white spruce. Permafrost is discontinugenerally low ice content. Soils range from solic with some Cryosolic soils in alpine rEutric Brunisols in subalpine and boreal sec
View of the Interior Forested Lowlands and Uplandsecoregion, which composes 21 percent of the YukonRiver Basin. The terrain consists of rolling lowlands, dissected plateaus, and rounded low to high hills. Climateis characterized by short warm summers and long coldwinters.View of the Interior Highlands ecoregion, which is thesecond largest ecoregion of the Yukon River Basin.Rounded mountains, often surmounted by ruggedpeaks, are typical of the ecoregion. Vegetation communities consist of alpine tundra and open spruce stands.
48 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

HYDROLOGIC CHARACTERISTICS OF THE YUKON RIVER BASINSurface Water

Streamflow quantity and variability have considerable influence on the quality of surface water. The quantity of water in a

stream or river influences its ability to support aquatic communities, to assimilate or dilute waste discharges, and to carry suspended sediment and geochemical weathering products. Temporalvariability of streamflow may, in turn, cause temporal variability

of water quality. Thus, knowledge of streaunderstand the water-quality and ecologicashed.

The Yukon River is composed of ma

Utilizing the Alaska Hydrologic Unit ClassGeological Survey, 1987) and a somewhat system for Canada, the Yukon River Basin major basins (table 5; fig. 17). These basimajor tributaries to the Yukon River and ththat drain directly into the Yukon River.

Table 5. Major drainage basins in the Yukon River Basin

Basin

(fig. 17)

Area

Comments Square 

miles Percent

Yukon Headwatersa

aBasin contained active gaging station in 1999

13,000 4.0 Drains an extensive lake system in the headwaters of the basin. Glaciers are present above th

Teslin River 13,100 4.1 East of the Yukon Headwaters subbasin. Most runoff is from snowmelt. Teslin Lake is near t

Pelly Rivera 18,600 5.8 Drains the most eastern part of the Yukon River Basin

Stewart Rivera 19,800 6.2 North of the Pelly River watershed and drains the eastern part of the Yukon River BasinWhite Rivera 18,100 5.6 Most significant feature is presence of glaciers in the upper part of the basin. Drains part of th

Upper Yukona 28,200 8.8 Primarily drains low-lying streams and rivers

Porcupine River 45,000 14.0 Drains the northeastern part of the Yukon River Basin. Most of the basin is underlain by con

Chandalar River 13,700 4.3 Drains the south side of the Brooks Range. Underlain by continuous permafrostEast Central Yukona 27,300 8.5 Drains low-lying streams. Main tributaries are the Porcupine and Chandalar Rivers

Tanana Rivera 44,300 13.7 Primarily drains the north side of the Alaska Range. Glaciers are present in the basinKoyukuk River 35,000 10.9 Drains part of the Brooks Range and is underlain by continuous permafrostWest Central Yukon 20,900 6.5 Drains low-lying streams along the main stem of the Yukon River. Main tributaries are the T

Lower Yukon 24,500 7.6 Drains low-lying streams. Main tributary is the Innoko River. Much of this area consists of w

Total 321,500 100
Figure 17. Major drainage basins in the Yukon River Basin. (See table 5 for more information.)

Yukon HeadwatersTeslin RiverPelly RiverStewart RiverWhite RiverUpper YukonPorcupine RiverChandalar RiverEast Central YukonTanana RiverKoyukuk RiverWest Central YukonLower Yukon

MAJOR DRAINAGE BASINS

0

0 100

100

200

200

300 KILOMETERS

300 MILES

Newtok

Saint Marys Pilot Station

Russian Mission

Holy Cross

Grayling

Shageluk

Kaltag

Koyukuk Ruby

Huslia

Hughes

Alatna

Bettles

Anaktuvuk Pass

Wiseman

Tanana

Rampart Minto

Fairbanks

Nenana

Cantwell

Healy

Delta Junction

Dot Lake

Eagle

Dawson

Northway Junction

Beaver Creek

Destruction Bay

Stewart Cro

Pelly Cros

Carma

Mayo

Central

Circle

Birch Creek

Fort Yukon

Venetie

Arctic Village Old Crow

HooperBay

Chevak

Anvik

Kotlik

Alakanuk

Galena

Nulato

Allakaket

Beaver

StevensVillage

Livengood

Manley HotSprings

North Pole

Two Rivers

Big Delta

Tok

Boundary

Burwash Landing

Ohogamiut

MountainVillage

Tanacross

Fortymile
50 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Snow and Ice

In the high mountain ranges that surround the Yukon River

Basin, most of the precipitation is in the form of snow. Approximately 1 percent of the Yukon River Basin consists of perennialsnowfields. When the quantity of annual snowfall exceeds averageannual snowmelt, the snow begins to change into ice or glaciers.The transformation of snow to ice is a process that is commonlylong and complex (Paterson, 1994). Temperature is an importantfactor because snow will develop into ice much more rapidly onglaciers where periods of melting alternate with periods of freezing (Paterson, 1994).

Approximately 3,500 mi2, or 1 percent of the Yukon River

Basin, is covered by glaciers. Glaciers are presently found in theAlaska Range and Wrangell

–St. Elias Mountains. These glaciers

are classified as temperate glaciers because they have a year-roundice temperature close to 32 °F. The importance of these glaciers to

the basin hydrology cannot be emphasized enough. Glaciers storean enormous quantity of water in the form of ice. This featurealone makes any drainage basin containing glaciers both uniqueand complex. The release of this water is highly dependent on theenergy supplied by solar radiation and air temperature (Meier,1969). Hot summers will cause rapid melting and high runoff,whereas a cool summer will have low runoff.

Streamflow

Generally, most stream-gaging stations in the Yukon River

Basin are located on rivers that drain areas larger than 1,000 mi2

.

Sixty-eight stream-gaging stations operated by the USGS inAlaska and the Water Survey of Canada in the Yukon Territory andBritish Columbia have 10 or more years of record (fig. 18; table6). Stream-gaging stations have been located on most of the maintributaries to the Yukon River. In 1999, 26 stream-gaging stationswere active in the Yukon River Basin: 17 in Canada and 9 in

Alaska (fig. 18). Active stream-gaging staseven of the 13 major basins (4 in Canada, 

Three basic patterns of runoff are exh

Yukon River Basin: lake runoff, snowmelt roff. Generally, beginning in October and emid-May, runoff is minimal and streamflow Most runoff occurs from May to Septembeof runoff in the rivers is different, dependbasin characteristics. 

Discharge hydrographs of three river

the Yukon River Basin (fig. 19) represent theterns. Lake or “combined” runoff: The Atli

lake system in the headwaters of the Yukothe runoff season, the lakes fill from snowmelt. Once filled, the lakes begin to empty charges occurring in August and Septemb

The Swift River drains an undisturbed arpresent. Most of the runoff occurs in June tional runoff may occur in late summer frorunoff: The Fantail River is a glacier-fed rJune primarily from snowmelt (such as the Stained throughout most of the summer from 

Discharge hydrographs for the head

River and its major tributaries (fig. 20) exhiterns of runoff. The Yukon River above Fraand the Teslin River near Teslin exhibit thThe Pelly and Stewart Rivers exhibit the snoAlthough the Porcupine, Chandalar, and exhibit the snowmelt pattern, the basefapproach zero flow during the winter. This lis likely due to the presence of continuous pwaters of the Yukon River Basin which acts water inflow. Finally, the White and Tanana cier-runoff pattern of sustained flow throug
43

65

41 40

38

39

42

62

50-54

37

36

48

49 55 56 35 33 34 29 2

30 

24 19 

18 

26

32 31

25

47

46

45

61 5960

58 57

67

63

64

66

68

44

27

Discontinued StationActive Station

STREAMFLOW-GAGING STATIONS (10 OR MORE YEARS OF RECORD)

Figure 18. Location of streamflow-gaging stations with 10 or more years of record in the Yukon River Basin. (See table 6 for stat

0

0 100

100

200

200

300 KILOMETERS

300 MILES
52 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Map 

No.

(fig. 

18)

USGS

station 

No.

Name

Drainage 

area

(square 

miles)

Period of record

1 15304520 Lubbock River near Atlin, BC 683 1960-932 15304600 Atlin River near Atlin, BC 2,630 1950-3 15304650 Wann River near Atlin, BC 104 1958-944 15304700 Fantail River at outlet of Fantail Lake 

near Atlin, BC

277 1957-94

5 15304750 Tutshi River at outlet of Tutshi Lake 

near Atlin, BC

320 1958-

6 15304800 Lindeman River near Bennett, BC 92.7 1955-947 15304850 Wheaton River near Carcross, YT 338 1958-8 15304950 Maclintock River near Whitehorse, YT 656 1956-949 15305000 Yukon River at Whitehorse, YT 7,490 1944-

10 15305030 Takhini River at Kusawa Lake at 

Whitehorse, YT

1,570 1953-86

11 15305050 Takhini River near Whitehorse, YT 2,700 1949-

12 15305100 Yukon River above Frank Creek, YT 11,900 1955-9413 15305150 Swift River near Swift River, BC 1,280 1958-14 15305200 Gladys River at outlet of Gladys Lake 

near Atlin, BC

737 1958-93

15 15305250 Teslin River near Teslin, YT 11,700 1948-9416 15305260 Teslin River near Whitehorse, YT 14,100 1956-7317 15305300 Big Salmon River near Carmacks, YT 2,610 1955-9518 15305350 Yukon River at Carmacks, YT 31,600 1965-9519 15305360 Big Creek near mouth near Minto, YT 676 1976-20 15305390 Ross River at Ross River, YT 2,800 1962-21 15305400 Pelly River at Ross River, YT 7,100 1955-74

22 15305406 Pelly River at Faro, YT 23 15305412 South MacMillan River at Canol Road 

near Ross River, YT

24 15305420 Pelly River at Pelly Crossing, YT 25 15305450 Yukon River above White River near 

Dawson, YT

26 15305500 Kluane River at outlet of Kluane 

Lake, YT

27 15305540 White River at Alaska Highway near 

Koidern, YT

28 15305582 Stewart River above Fraser Falls near 

Mayo, YT

29 15305590 Stewart River at Mayo, YT 30 15305620 Stewart River at Stewart Crossing, YT 31 15305650 Stewart River at mouth, YT 32 15305670 Yukon River at Stewart, YT 33 15305695 North Klondike River near mouth near 

Dawson, YT

34 15305698 Klondike River above Bonanza Creek 

near Dawson, YT

35 15305700 Yukon River at Dawson, YT 136 15348000 Fortymile River near Steele Creek, AK 37 15356000 Yukon River at Eagle, AK 38 15388950 Porcupine River at Old Crow, YT 39 15388960 Porcupine River near International 

Boundary, YT

Map 

No.

(fig. 

18)

USGS

station 

No.

Name

D

Table 6. Streamflow-gaging stations in the Yukon River Basin with 10 or more years of record
40 15389000 Porcupine River near Fort Yukon, AK 29,500 1965-7941 15389500 Chandalar River near Venetie, AK 9,330 1964-7342 15439800 Boulder Creek near Central, AK 31.3 1966-82, 1984-8643 15453500 Yukon River near Stevens Village, AK 196,300 1976-44 15468000 Yukon River at Rampart, AK 199,400 1956-6745 15470000 Chisana River at Northway 

Junction, AK

3,280 1950-71

46 15476000 Tanana River near Tanacross, AK 8,550 1953-9047 15476300 Berry Creek near Dot Lake, AK 65.1 1971-8148 15478000 Tanana River at Big Delta, AK 13,500 1949-5749 15484000 Salcha River near Salchaket, AK 2,170 1909-10, 1949-50 15485500 Tanana River at Fairbanks, AK (a) 1973-51 15493000 Chena River near Two Rivers, AK 941 1967-52 15493500 Chena River near North Pole, AK 1,440 1972-8053 15511000 Little Chena River near Fairbanks, AK 372 1967-54 15514000 Chena River at Fairbanks, AK 1,980 1947-

Map 

No.

(fig. 

18)

USGS

station 

No.

Name

Drainage 

area

(square 

miles)

Period of record

55 15514500 Wood River near Fairbanks, AK 56 15515500 Tanana River at Nenana, AK 57 15515800 Seattle Creek near Cantwell, AK 58 15516000 Nenana River near Windy, AK 59 15518000 Nenana River near Healy, AK 60 15518080 Lignite Creek above mouth near 

Healy, AK

61 15518350 Teklanika River near Lignite, AK 62 15535000 Caribou Creek near Chatanika, AK 63 15564600 Melozitna River near Ruby, AK 64 15564800 Yukon River at Ruby, AK 265 15564875 Middle Fork Koyukuk River near 

Wiseman, AK

66 15564900 Koyukuk River at Hughes, AK 67 15565200 Yukon River near Kaltag, AK 268 15565447 Yukon River at Pilot Station, AK 3

Map 

No.

(fig. 

18)

USGS

station 

No.

Name

D

aUndefined: part of the river flows through Salchaket Slough and is not gaged.

Table 6. Streamflow-gaging stations in the Yukon River Basin with 10 or more years of record--Continued
54 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

0

15,000

5,000

10,000

0

20,00010,000

0

15,000

5000

10,000

Figure 19. Flow statistics of three rivers near the headwaters of the Yukon River. (See figure 18 for site locat

MINIMUMMEANMAXIMUM

J FMAM J J A SOND

ATLIN RIVER NEAR ATLIN, BC (1950-96) (Map No. 2)

J FMAM J J A 

SWIFT RIVER NEAR SWIFT RIVER, BC (

J FMAM J J A SOND

FANTAIL RIVER AT OUTLET OF FANTAIL LAKE NEAR ATLIN, BC (1957-94) (Map No. 4)

MINIMUMMEANMAXIMUM

MINIMUMMEANMAXIMUM

AVERAGE DISCHARGE, 

IN CUBIC FEET PER SECOND

AVERAGE DISCHARGE, 

IN CUBIC FEET PER SECOND

(Lake or "combined" runoff) 

(Glacier runoff)
EXPLANATION

MINIMUMMEANMAXIMUM

0

80,00020,00040,00060,000

0

30,00010,00020,000

AVERAGE DISCHARGE, IN CUBIC FEET PER SECOND 0 200,000 100,000

J FMAM J J A SOND

YUKON RIVER ABOVE FRANK CREEK NEAR CARMACKS, YT (1955-94)(No. 12)

J FMAM J J A SOND

TESLIN RIVER NEAR TESLIN, YT (1948-94) (No. 15)

J FMAM J J A SOND

PELLY RIVER AT PELLY CROSSING, YT (1953-96) (No. 24)

Figure 20. Flow statistics of nine major rivers of (See figure 18 for site location.)

J FMAM J J A SOND

0

300,000100,000200,000

J FMAM J J A SOND

0

300,000100,000200,000

STEWART RIVER AT MOUTH, YT (1964-96) (No. 31)

PORCUPINE RIVER NEAR FORT YUKON, AK (1965-79)(No. 40)

J FMAM J J A SO

0

80,00020,00040,00060,000

CHANDALAR RIVER NEAR VENETIE, AK (1964-73)(No. 41)

AVERAGE DISCHARGE, IN CUBIC FEET PER SECOND

J FMAM J J A SO

0

100,000

50,000

J FMAM J J A SO

0

300,000100,000200,000

TANANA RIVER AT NENANA, AK (1962-98)(No. 56)

KOYUKUK RIVER AT HUGHES, AK (1961-82) (No. 66)

J FMAM J J A SO

0

60,00020,00040,000

WHITE RIVER AT ALASKA HIGHWAY NEAR KOIDERN, YT (1975-96)(No. 27)

(Lake)(Lake)(Snowmelt)(Snowmelt)(Snowmelt)
56 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

The discharge hydrographs of several stream-gaging stations

located along the main stem of the Yukon River (fig. 21) indicatethe contributions of the various rivers to the Yukon River. Most ofthe increase in flow of the Yukon River between Carmacks andDawson is primarily from input from the White River and theStewart River. Between Eagle and Stevens Village, flow increasesfrom input from the Porcupine and Chandalar Rivers. The YukonRiver at Ruby includes input from the Tanana River, and theYukon River at Kaltag includes the inflow from the KoyukukRiver. Between Kaltag and Pilot Station, some of the flow of theYukon River goes into storage during June. Most of the areabetween Kaltag and Pilot Station is low-lying wetlands.

The average discharge for the Yukon River at Pilot Station is

227,000 ft3/s, based on the period of record, 1976-96. Using the

discharge records for the main tributaries of the Yukon, the relativecontribution of discharge for each of the major drainage basinswas computed (table 7; fig. 22). The percentage of flow from thetwo glacier basins, the Tanana and White, was higher than the percentage of their respective drainage areas (fig. 22). Conversely, thepercentage of flow from the Porcupine and Chandalar Rivers (nonglacier basins) was less than the percentage of their drainage areas.

The waters of the Yukon River enter the Bering Sea and

move northward to the Arctic Ocean. Of the 10 largest inputs intothe Arctic Ocean, the Yukon River ranks fifth behind the Yenisei,Ob, and Lena Rivers of Russia, and the Mackenzie River of Canada, and contributes 8 percent of the total discharge to the ArcticOcean (fig. 23) (Aagaard and Carmack, 1989). Thus, the YukonRiver is a major contributor of water and solutes to the ArcticOcean and the Bering Sea ecosystems. Changes in the YukonRiver—either in flow or water quality

—could influence these ecosystems.

Table 7. Flow contributions of major drato the Yukon River Basin

Basin

Flow

(cubic feet per 

second)

Yukon Headwaters 11,500 Teslin River 11,800 Pelly River 14,000 Stewart River 16,400 White River 21,000 Upper Yukon 9,700 Porcupine River 22,000 Chandalar River 7,400 East Central Yukon 14,800 Tanana River 44,600 Koyukuk River 27,200 West Central Yukon 15,600 Lower Yukon 11,100 

Total 227,000 
0

800,000100,000200,000300,000400,000500,000600,000700,000

AVERAGE DISCHARGE, IN CUBIC FEET PER SECOND

J FMAM J J A S O

Figure 21. Average discharge of the Yukon River at eight locations (see figure 18 for locations).

EXPLANATION

Yukon River at Carmacks (No. 18)Yukon River above White River (No. 25)Yukon River at Dawson (No. 35)Yukon River at Eagle (No. 37)Yukon River near Stevens Village (No. 43)Yukon River at Ruby (No. 64)Yukon River near Kaltag (No. 67)Yukon River at Pilot Station (No. 68)
58 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Headwaters Teslin Pelly Stewart White Upper Porcupine Chandalar ECentral Tanana Koyukuk WCentral L

MAJOR DRAINAGE BASIN

25

5

101520

PERCENT 

EXPLANATION

Percent AreaPercent Flow

0

Figure 22. Percent contributions of area and flow of the major drainage basins of the Yukon RivBasin.

60 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Floods

Floods, as extreme hydrologic events, can affect water quality. The largest loads of many constituents from nonpoint sources

occur during flooding. Floodwaters may scour gravels and depositfine-grained sediment, damaging spawning beds for some fishspecies. Floods also wash young juvenile fish out of the river. 

In the Yukon River Basin, annual high flows for most of the

major rivers occur during the summer rainy season. However, onthe main stem of the Yukon, flooding commonly occurs from icejams in the spring. Although levees have been built at Dawson toprevent flooding from ice jams, villages located along the lowerpart of the Yukon River are still subject to flooding each spring.

The history of flooding in the Yukon River Basin is virtually

unknown before the establishment of a network of streamflowgaging stations in the late 1940’s and early 1950’s. A few identified historical floods in the upper Porcupine and Yukon Rivers

during the Pleistocene era were caused by the sudden release ofwater from glacial lakes in the Yukon Territory (Thorson andDixon, 1983). In addition, a flood history of the Chena River atFairbanks began with a major flood in 1905. Since 1949, threemajor floods have occurred in the Yukon River Basin: in 1964,1967, and 1994. These floods covered large areas of the basin andcaused considerable property damage.

Flood of June and July 1964

—Large snowpacks located in

the Yukon River Basin caused several streams to reach peak discharges of record. The floods were caused by rapid snowmelt fromthese large snowpacks and, in some places, by rain on water-saturated snow. Flooding occurred mainly in sparsely populated areasof the upper Yukon (in Alaska) and the Koyukuk River Basin. In

many small streams, peak discharges were conditions of snow cover were right, peak largest of record. The dates of the peak diearly June to early July, depending on thaspect and altitude of the contributing basinstantial rainfall. 

Flood of August 12-18, 1967

—Beg

1967, a series of widespread general rains oand lower Tanana River Basin near Fairbankfall totaled 10 in., which is nearly the averagfor the area. Floods of the Salcha River anFairbanks were extremely large, and the mthe Salcha River was almost twice that of a 100-year recurrence interval (fig. 24). Abobanks was under water (Childers and otwhich is downstream from Fairbanks on twas inundated. This flood caused about $85 

Flood of August 1994

—Beginning 

severe storms began in western Alaska aFlooding occurred in the Koyukuk River Bain. of rain fell in the upper part of the basin ond storm on August 24-27, with an additioccurred in the upper part of the Koyukcaused major flooding at Wiseman, washed way in three places, and forced the evaculocated along the Koyukuk River: AllakakeThese villages were declared disaster areas amillion was needed to relocate Allakaket ground. The peak discharge of the Koyukuto have a recurrence interval of 100 years.
1967 Flood

MINIMUM DISCHARGEMEAN DISCHARGEMAXIMUM DISCHARGE

J FMAM J J A S O

0

100,000

10,00020,00030,00040,00050,00060,00070,00080,00090,000

DISCHARGE IN CUBIC FEET PER SECOND

Figure 24. Flow statistics of the Salcha River near Salchaket, Alaska (1949-98).
62 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Droughts

Like floods, droughts are also extreme hydrologic events

that affect water quality. Droughts or deficit streamflows in theYukon River Basin primarily affect anadromous fish, which maynot have sufficient streamflow to migrate upstream to spawn, oraffect the eggs after spawning, which may not survive if they areexposed as stream levels decline. During low flows, water temperatures of streams tend to increase and concentrations of dissolvedoxygen tend to decrease. Long periods of deficit rainfall commonly lead to declines in ground-water levels, which, in turn,decrease baseflow of streams, decrease available supply fromsmall-yield wells, and lower water levels in lakes.

In the Yukon River Basin, annual low flow occurs during the

winter when there is no surface runoff and inflow is primarily fromground water. During the runoff season, discharge is higher than inthe winter period even if snowfall and rainfall are below average.In addition, glacier-fed streams add icemelt as input to a stream.Thus, assigning a time period as a drought is somewhat subjective.An approach used by Lamke (1991), which analyzes the departureof the annual discharge from the long-term mean, provides a goodindication of the trend of streamflow. By analyzing the streamflowat eight long-term gaging stations (fig. 25), four droughts or periods of deficit flow were identified in the Yukon River Basin since1949.

Drought of 1950-57

—Most of the upper Yukon River Basin

and the upper Tanana River Basin were affected during this period.The drought was less severe farther west along the Alaska Range.

On the main stem of the Yukon River, defic1950 at Eagle (fig. 25A). The cumulative years of drought was equivalent to about 1 

Drought of 1969-70

—This period of 

marily the Alaska part of the Yukon River Bicit flow for the period of record occurred at Hughes (fig. 25B). Deficit flow was also River (fig. 25C) and the lower part of the (fig. 25D).

Drought of 1973-80

—This period is 

most severe low flow period in terms of dSimilar to the 1969-70 period, only the AlaRiver Basin was affected (the records from (fig. 25E, F, A) do not indicate any trendTanana Rivers (fig. 25B, C) and the lower pwere most affected.

Drought of 1996 to present

—In th

snowfall was significantly less than normaYukon River Basin. Relatively large deficit the Yukon River above the White River, at Elage, and at Pilot Station (fig. 25F, A, G, River (fig. 25C). For three stations where f(the Yukon River at Eagle and near StevTanana River at Nenana, figs. 25A, G, Coccurred in 1998, which may signal anothe
Figure 25. Departure from average discharge for several long-term streamflow-gaging stations in the Yukon Rivefor locations).

G

D

Yukon River near Stevens Village

Koyukuk River at Hughes Yuk

Yu

1940

-40,000

40,000

-20,000

0

20,000

1940

-10,000

10,000

-5,000

0

5,000

1960 1980 2000

YEAR

1940 

-40,000

80,000

-20,000

0

20,00040,00060,000

1940

-60,000

40,000

-40,000-20,000

0

20,000

1960 1980 2000

YEAR

B

H

1940

-4000

4000

-2000

0

2000

DEPARTURE FROM MEAN, IN CUBIC FEET PER SECOND -40,000

40,000

-20,000

20,000

10,000

Yukon River at Whitehorse Yukon River above White River

Yukon River at Eagle

E F

A C

1940

-15,000

20,000

-10,000

-5000

0

5000

10,00015,000

1960 1980 2000

YEAR

1960 1980 2000

YEAR

1940 2000 1960 1980

YEAR

1940 2000 1960 1980

YEAR

-10,000

-5000

5000

0 0

Tanana River at Nenana
64 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Sediment

Sediment is an important water-quality constituent. Particle

size determines to a large extent whether a stream carries the sediment as suspended load or as bedload. Elevated suspended-sediment concentrations can adversely affect aquatic life by clogginggills, covering fish spawning sites, or by altering habitat of benthicorganisms (U.S. Environmental Protection Agency, 1977). Metalsand organic contaminants also commonly adsorb on suspendedsediment (U.S. Environmental Protection Agency, 1977).

Collection of suspended-sediment sam

part of the Yukon River Basin began in 1970 ada as part of a basic monitoring program (Rment Canada, written commun., 1998). collected during various years at six sites (the major basins in the Canadian part of the three suspended-sediment samples were cduring the open-water season. Currently, collected at four sites each year.

Map 

No. 

(fig. 

18)

USGS 

Station 

No.

Name

Period

of

record

Canada

9 15305000 Yukon River at Whitehorse, YT 1970-77

24 15305420 Pelly River at Pelly Crossing, YT 1970-25 15305450 Yukon River above White River near Dawson, YT 1977-27 15305540 White River at Alaska Highway near Koidern, YT 1975-31 15305650 Stewart River at mouth, YT 1968-35 15305700 Yukon River at Dawson, YT 1971-79

Alaska

37 15356000 Yukon River at Eagle, AK 1954-7940 15389000 Porcupine River near Fort Yukon, AK 1967-7541 15389500 Chandalar River near Venetie, AK 1967-7544 15468000 Yukon River at Rampart, AK 1954-6745 15470000 Chisana River at Northway Junction, AK 1953-6746 15476000 Tanana River near Tanacross, AK 1953-7548 15478000 Tanana River at Big Delta, AK 1971

Map 

No. 

(fig. 

18)

USGS 

Station 

No.

Name

Alaska--Continued

49 15484000 Salcha River near Salchaket, AK 50 15485500 Tanana River at Fairbanks, AK 51 15493000 Chena River near Two Rivers, AK 52 15493500 Chena River near North Pole, AK 54 15514000 Chena River at Fairbanks, AK 55 15514500 Wood River near Fairbanks, AK 56 15515500 Tanana River at Nenana, AK 59 15518000 Nenana River near Healy, AK 63 15564600 Melozitna River near Ruby, AK 64 15564800 Yukon River at Ruby, AK 65 15564875 Middle Fork Koyukuk River near W66 15564900 Koyukuk River at Hughes, AK 68 15565447 Yukon River at Pilot Station, AK 

Table 8. Suspended-sediment stations in the Yukon River Basin
Collection of suspended-sediment data in the Yukon River

Basin in Alaska began in 1953 (table 8). For the next decade, mostof the sediment data-collection effort focused on two rivers, theTanana River near Tanacross and the Nenana River near Healy. Atthese two sites, daily suspended-sediment samples were collectedduring the 4 to 5 months of the runoff season, May to September.In 1962, daily suspended-sediment sample collection also began attwo more stations, Yukon River at Eagle and Chena River at Fairbanks. For the next 5 years, daily sediment samples were collectedthrough most of the runoff seasons at all four stations. Samplingwas discontinued at three of the stations at the end of the 1966water year. At the remaining station, Chena River at Fairbanks,daily sampling continued until 1971. Since 1971, no daily suspended-sediment sampling programs have been undertaken.

In 1967, the focus of sediment sampling in the Alaskan part

of the Yukon basin shifted from daily samplings at a few selectedstations to sporadic samplings at a larger number of stations (table8). This program consisted of collecting three to five sedimentsamples (ideally, one per month) through the runoff season atabout 12 stations in the Alaskan part of the Yukon River Basin.This program lasted only a few years and essentially ended by theend of 1975.

The most recent phase of sediment data collection, from the

late 1970’s until 1996, has centered on two stations supported bythe USGS National Stream Quality Accounting Network(NASQAN) program, the Tanana River at Nenana and the YukonRiver at Pilot Station. Although only a few samples were collectedeach year, the length and consistency of these sampling effortsgive added value to the sediment data. Also, from 1977-82, bedload data were collected along a reach of the Tanana River nearFairbanks 

Records of all the suspended-sedime

available in USGS publications (U.S. Geolo1971, 1976, 1972-75, 1976-96). Data are alformat in the USGS National Water InformBedload data for the Tanana River are availrows (1980), Burrows and others (1979, 19rold (1983), Emmett and others (1978), and (1983). Data from the Canadian Yukon are “Sediment Data: Canadian Rivers,” issued bCanada and are also available in electronic fwide web (http://www.ec.gc.ca/water/indexSources of Sediment

Sediment in streams and rivers is the 

sion, a process that can be accelerated by lsuch as mining. In the Yukon River Basin, tsequent erosion of sediment are due primaHowever, distinctions can be made dependinular river is non-glacier fed or glacier fed.

Non-glacier-fed tributaries of the Yu

composed of sand, gravel, and cobbles. Tfound in the upper reaches of these rivers anthe lower reaches. Banks consist of poorgravel in the steep upper reaches, but changthe lower reaches. River channels are braidebut become less pronounced as the river bsediment is deposited in the lower reaches. ally sorted and rounded progressively downgravel and cobbles in the thalweg and grave
66 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Glacier-fed rivers in the Yukon River Basin have vast quantities of unconsolidated material downstream from the glacier termini. These rivers have wide flood plains cut with braided

channels. Boulders, cobbles, gravel, sand, and large quantities offine silt make up the streambank and bed, and provide a readysource of sediment. Streambanks are barren with little vegetationand have large boulders rounded from the previous advances of theglacier. Steep reaches create high stream velocity, which transportsgravel and cobble-size material downstream as bedload, and sandand silt in suspension. Braiding is pronounced and extends fardownstream because of high sediment loads.

As in non-glacier-fed streams, material is sorted downriver

in the main channels of glacier-fed rivers as the slope of the riverdecreases. When flows are low enough for bars to be visible, mostbars are covered with silt and fine sand, deposited on recessionfrom higher flows. The fine sediment in suspension from the glacier basins may be transported even at low flows, but the withinchannel deposits augment the sediment load at higher flows.Except where constrained by bedrock walls, broad alluvial plainsleft from the last glacial retreat characterize the valleys downstream from the montane regions. In the Yukon River Basin, theseareas are large wetlands that are cut by numerous old channels andsloughs, and covered with tussocks, brush, willows, aspen, birch,and spruce trees.

In areas of the Yukon River Basin where permafrost is discontinuous, riverbanks may be perennially frozen at depth and

overlain with a seasonally frozen layer of organic material andvegetation. This condition creates an additional source of sedimentin the summer when the permafrost is thermally eroded by flowingwater. The result is undercut banks, overhanging vegetation, and

finally failure of the upper bank, causing tment to fall into the river.Suspended-Sediment Concentrations

Suspended-sediment concentration 

most of the major tributaries to the Yukon sites along the Yukon River itself. These dgraphically by the use of boxplots (fig. 26)ited number of samples have been collected observations can still be made.

Most of the measured suspended-sed

for the main stem of the Yukon River were The two major glacier-fed rivers, the Whitthe highest concentrations. Concentrations Whitehorse, the farthest upstream site, were Going downstream, the median sediment Yukon River at Dawson and at Eagle were input of the White River. From Eagle to changes in median concentration seemed apthis site, the median concentration was highfrom the Tanana River. From Ruby to Piloconcentration decreased slightly.

A number of analyses show that virtu

cles carried in suspension in the Yukon Riveies are finer than 0.5 mm. Within the susitself, 90 percent is finer than 0.25 mm

—t

and 0.25 mm in nominal diameter. For socomplete particle-size analyses indicate thpredominantly of silt and clay (table 9).
Whitehorse Pelly Above

White

White Stewart Dawson Eagle Porcupine Chandalar Rampart Tanana Ruby H

1

10,000

25

102050

100200500

100020005000

SUSPENDED-SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER (10) (44) (12)

(48)

(28)

(14)

(31)

(14)

(15) (8)

(104)

(22) (

Figure 26. Boxplots of suspended-sediment concentrations at 14 sites in the Yukon Rive

Number of observations 75th percentile

Median

25th percentile

Outlier data value less than or equal to 3 and more than1.5 times the interquartile range outside the quartile

Data value less than or equal to 1.5 times tinterquartile range outside the quartile

Pilot Station name designation 

(74)

EXPLANATION
68 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Relation Between Suspended-Sediment Concentration and Water Discharge

Suspended-sediment concentrations in the Yukon River and

most of its tributaries generally increase with increasing water discharge, although a high correlation does not always exist (fig. 27).Much of the scatter of points is related to the well-known “clockwise-looped” relation (Meade and others, 1990, p. 257), in whichsediment concentrations measured while a river is rising are usually higher than those measured at the same water discharges asthe river is falling. The clockwise-looped relation is usuallyexplained as showing a depletion effect: fine-grained sediment,

which is stored on the bed or along the banking low-water periods, is in plentiful supply rise, but the stored material is soon resuspenbecomes depleted as (or before) the river discharge. Additionally, the particle-size dpended sediment may influence the correcharge (fig. 28). For example, concentratioare less correlated with water discharge than pended silt and clay.

In rivers that directly drain the montan

River Basin, the concentrations and dischcoupled closely with water discharge. For eRiver near Tanacross (fig. 29A), each pulse charge is accompanied by an increase in sedThe closeness of this correlation suggests eiwater and sediment are identical (melting gllarge quantities of excess sediment are storing to be mobilized by each pulse of water 

Farther from the montane sources, the 

daily water discharges and sediment coweaker. The Yukon River at Eagle (fig. poorer relation with water discharge thaTanana River near Tanacross. Sediment conally highest between mid-July and mid-Auafter the greatest discharge of water. At this main stem, the most likely source of large pended sediment is the White River and itthe Wrangell

–St. Elias Mountains.

Table 9. Mean grain-size composition of suspended sediment forstations in the Yukon River Basin

Map 

No.

(fig. 

18)

USGS

Station 

No.

Name

No. of 

samples

Percentage

Clay Silt Sand

24 15305420 Pelly River at Pelly Crossing, YT 30 18 48 3425 15305450 Yukon River above White River 

near Dawson, YT

9 35 51 14

27 15305540 White River at Alaska Highway 

near Koidern, YT

141 28 46 26

31 15305590 Stewart River at mouth, YT 19 21 57 2237 15355600 Yukon River at Eagle, AK 8 34 50 1644 15468000 Yukon River at Rampart, AK 7 26 50 2468 15565447 Yukon River at Pilot Station, AK 5 26 53 21
100 1000 10,000 100,000

1

10,000

10

100

1000

100 1000 10,000 100,000

WATER DISCHARGE, IN CUBIC FEET PER SECOND

1

10,000

10

100

1000

Chena River at Fairbanks

Figure 27. Water discharge and suspended-sediment concentrations for Chena River atFairbanks, Alaska, and Nenana River near Healy, Alaska, for 1964-66 runoff seasons.

Nenana River near Healy

SUSPENDED-SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER
70 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

1000 100,000 10,000

10

10,000

2050

100200500

100020005000

SUSPENDED-SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER 1000 100,000 10,000

TANANA RIVER NEAR TANACROSS, 1954

1000 

10

EXPLANATION

Clay

10

10,000

2050

100200500

10002000

5000

EXPLANATION

Silt

10

10,000

2050

100200500

100020005000 EXPLANATION

Sand

10,000 100,000 20,000 50,000

10

10,000

2050

100200500

100020005000

10,000 100,000 20,000 50,000 10,000 

20,000 

10

10,000

2050

100200500

100020005000

10

10,000

2050

100200500

100020005000

EXPLANATION

Clay

INSTANTANEOUS DISCHARGE, IN CUBIC FEET PER SECOND

EXPLANATION

Silt

EXPLANATION

Sand

Figure 28. Instantaneous discharge and suspended-sediment concentrations for different particle sizes for TaTanacross, Alaska, and Tanana River at Fairbanks, Alaska.

TANANA RIVER AT FAIRBANKS, 1975, 1977-78
Discharge

Suspended sediment

0

40,00010,00020,00030,000

0

300,000100,000200,000

WATER DISCHARGE, IN CUBIC FEET PER SECOND 0

5,0001,0002,0003,0004,000

SUSPENDED-SEDIMENT CONCENTRATION, IN MILIGRAMS PER LITER May June July Aug Sept

05,0001,0002,0003,0004,000 Discharge

Suspended sediment

B. Yukon River at Eagle

May June July Aug Sept

Figure 29. Average daily water discharge and suspended-sediment 

concentration for Tanana River near Tanacross, Alaska, and Yukon River at Eagle, Alaska, during 1963 runoff season.

A. Tanana River near Tanacross
72 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Suspended-Sediment Discharge

The most striking characteristic of sediment discharge in the

Yukon River Basin is its seasonality. More than 95 percent of allthe sediment discharged during an average year is moved duringthe months of May through September (fig. 30). In someinstances, more than half of the suspended-sediment load may betransported in 10 percent of the year during high flows (Burrowsand others, 1981) As conveyors of sediment, the rivers are virtually dormant during the other seven month

April. In its annual cycle of warm-season flfreeze-up, the entire river system shuts down age mode in autumn, to be reactivated and spring or early summer. Although some degtypical of most large rivers elsewhere, in tempical regions, it is especially pronounced in the rivers.

Chena River at Fairbanks 

(1964-66)

Nenana Ri

(1

Tanana River near Tanacross

(1954, 1964-66)

0

5010203040

0

5010203040

PERCENT OF ANNUAL

 SUSPENDED-SEDIMENT DISCHARGE

0

5010203040

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Se

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Figure 30. Seasonal distributions of suspdischarge for three rivers in the Tanana R

PERCENT OF ANNUAL

 SUSPENDED-SEDIMENT DISCHARGE
Differences in sediment discharge

from the rivers in the Yukon River Basindepend on the type of watershed. A quantitative comparison of montane (glacier) versuslowland (non-glacier) sediment loads is provided by the extensive records collected inthe Nenana River near Healy and the ChenaRiver at Fairbanks. Especially useful are theyear-long records of daily sediment discharge measured (and partially estimated) atboth stations during three consecutive wateryears, 1964-66 (U.S. Geological Survey,1970-71a). Although the daily values for theseven coldest months (October to April)were mostly estimated, the estimation procedures entailed only a small error overallbecause cold-weather discharge constitutessuch a small proportion of the totals for theyear.

Contrasts in water discharge and sediment load shown by the two records are

striking (fig. 31). Although the drainageareas above the two gaging stations differ byonly 4 percent, the water discharge from themontane area (Nenana River) was 2.5 timesgreater than that from the lowland area(Chena River). Furthermore, sediment loadfrom the Nenana River Basin was 30 timesthe sediment load from the Chena RiverBasin. Reasons for the greater water discharges from montane areas are most likelythe greater precipitation that falls at higheraltitudes, and the partial but significant coverage of the drainage area by glaciers thatcontribute a steady flow of meltwater during

0

14,000

2000400060008000

10,00012,000

AVERAGE MONTHLY DISCHARGE,

IN CUBIC FEET PER SECOND

EXPLANATION

Nenana River (1,910 square miles)Chena River (1,980 square miles)

Jan Feb Mar Apr May Jun Jul Aug Se

0

1,500,000

500,000

1,000,000

MONTHLY SUSPENDED-SEDIMENT LOAD,

IN TONS

EXPLANATION

Nenana River (1,910 square miles)Chena River (1,980 square miles)

Jan Feb Mar Apr May Jun Jul Aug Se

MONTH

Figure 31. Differences in water discharge and suspendedwater years 1964-66 for Nenana River near Healy, Alaska Fairbanks, Alaska.
74 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

warmer months. Reasons for the greater sediment discharges arethe more intensive tectonism in the montane areas, producing suchfeatures as over-steepened slopes on fractured bedrock, and morecoverage by glaciers, whose basal grindings greatly increase therates of mechanical erosion.

The particle-size distribution of the sediment load varies during the runoff season. Sand may compose half or more of the sediment in suspension in some river reaches during the early and

later months of the runoff season when overall concentrations arelower (fig. 32). However, it composes only one-third to one-quarter (considerably less, at times) of the sediment in suspension in

mid-season when total suspended concentraest. 

Using the available suspended-sedim

ment loads were determined for most of the of the Yukon River. A method described by Cto compute the annual suspended-sediment This method requires defining a relation bsediment discharge and water discharge and to daily discharge. Also, it was assumed that resent today’s conditions, and that no interi

land use, and other factors have significa

0

300,000100,000200,000

SUSPENDED-SEDIMENT DISCHARGE,

 IN TONS PER DAY

3-25 6-1 6-16 7-1 7-7 7-13 7-19 7-25 8-1 8-11 8-21 9-1 9-16

MONTH AND DAY

Figure 32. Changing proportions of suspended-sediment discharge during1954 runoff season in Tanana River near Tanacross, Alaska.

EXPLANATION

Silt and ClaySand
yields during the last several decades. The sediment loads are considered to be subject to large errors since they are based mostly onlimited data. However, they provide some insight on the suspended-sediment characteristics of the Yukon River Basin.

Approximately 60 million tons of suspended sediment are

transported annually by the Yukon River at Pilot Station near itsmouth (table 10; fig. 33). The overwhelming importance of sourceareas in the Alaska Range drained by tributaries of the TananaRiver, and of the Wrangell

–St. Elias Mountains drained by the

White River and its tributaries is clearly shown. All other tributaries flowing from the Brooks Range and the more lowland areas ofthe Yukon Basin contribute fairly minor quantities of sediment.Thus, the Yukon River functions mainly as a conveyance systemthat gathers sediment from the high mountain ranges and transports it hundreds, even thousands, of miles to the Bering Sea.Storage of Sediment

At Ruby, about 450 mi upstream from Pilot Station, the

Yukon River transports about 66 million tons of suspended sediment per year, about 6 million tons more than at Pilot Station (table10). The Koyukuk River adds 2 million tons to the Yukon belowRuby (table 10). Some of the sediment load is probably depositedon the flood plains and delta plains that lie along the Yukonbetween Ruby and Pilot Station. Deposition of sediment isexpected because part of the water discharge of the Yukon Rivergoes into storage during the runoff season.

A similar calculation can be made for the approximately

200-mile-long reach of the Yukon between Rampart and Ruby.The river transports about 33 million tons of sediment past Rampart during an average year. About 68 mi below Rampart, theTanana River adds another 38 million tons, bringing the total to 71million tons annually. Comparing this total to the 66 million tonsmeasured at Ruby suggests that a quantity of about 5 million tonsof sediment is being deposited out of the channel each year, most

likely in the flood plain that fringes the soutbelow its confluence with the Tanana River

The segment of the Yukon River betw

also a significant reach for sediment storament loads at Eagle and Rampart are virtuatons despite two intervening tributaries, the Rivers, that annually contribute another 9 between the two main stem stations. In addthe Yukon increases about 75 percent. Tincludes Yukon Flats, an enormous tectonithat can easily accept and store sediment.

Table 10. Estimated annual suspended-sediselected sites in the Yukon River Basin

Map 

No.

(fig. 

18)

USGS

Station No. Name 

9 15305000 Yukon River at Whitehorse, YT 

24 15305420 Pelly River at Pelly Crossing, YT 25 15305450 Yukon River above White River n27 15305540 White River at Alaska Highway n31 15305590 Stewart River at the mouth, YT 35 15305700 Yukon River at Dawson, YT 37 15356000 Yukon River at Eagle, AK 40 15389000 Porcupine River at Fort Yukon, A41 15389500 Chandalar River near Venetie, AK 44 15468000 Yukon River at Rampart, AK 56 15515500 Tanana River at Nenana, AK 64 15564800 Yukon River at Ruby, AK 66 15564900 Koyukuk River at Hughes, AK 68 15565447 Yukon River at Pilot Station, AK 
76 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

In summary, the Yukon River system is depositing and storing an average annual net quantity of about 20 million tons of sediment between the principal montane sources and the sea, most

likely on fringing flood plains and in braided reaches of the river.This net quantity represents a minimum because riverbank erosionis not included in the sediment budget. If bank erosion is, in fact,

a significant contributor of sediment to the Yother large rivers (Dunne and others, 1998balanced budget would require even greater to be leaving the river channel and being stoand meander bars.

70102030405060

ANNUAL SUSPENDED-SEDIMENT LOAD, IN MILLIONS OF TONSEXPLANATION Yukon River station Major tributary to Yukon River

0

Whitehorse Pelly Above

White

White Stewart Dawson Eagle Porcupine Chandalar Rampart Tanana Ruby Koyuku

STATION

Figure 33. Annual suspended-sediment loads for 14 sites located in the Yukon River Basin.
Although the sediment load numbers are approximate and

subject to large errors (they are based mostly on limited data), it isevident that a large proportion of the total sediment being transported out of the principal (mostly montane) source areas is notreaching the sea within the same year, decade, or even century. Atleast one-quarter, perhaps one-third, of the sediment is beingdeposited along the way, mostly as overbank sediment on theextensive flood plains that fringe large reaches of the Yukon River.Implications of this factor are enormous for the sequestration oforganic carbon, contaminants, and other materials that areabsorbed onto, or otherwise associated with, alluvial sediments.

Bedload

The only known area in the Yukon R

load transport has been measured intensiveat Fairbanks. This site represents one of the world where bedload has been measured rather than computed by standard formulas. equivalent to one or two percent of suspendproportion is well within the error of suspenand therefore is not usually included in ansediment transport. Although bedload movthe formation and stability of river channelpart of the overall sediment load.

100

1,000,000

1000

10,000

100,000

SUSPENDED-SEDIMENT AND BEDLOAD DISCHARGE,

IN TONS PER DAY

EXPLANATION

Suspended-SedimentBedload

1000 2000 5000 10,000 20,000 50,000 100,000

WATER DISCHARGE, IN CUBIC FEET PER SECOND

Figure 34. Suspended-sediment and bedload discharges measured in the Tanana Riverat Fairbanks, Alaska, 1977-82 (data from Burrows, 1981; Burrows and Harrold, 1983).
78 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Water Quality

The water quality of the Yukon River Basin is important for

many reasons. Residents who live along the main stem of theYukon or its tributaries use the surface water for drinking. Salmonand other fish species require adequate water quality for their survival as does the abundant wildlife present in the basin.

Water-quality samples have been collected at more than 400

sites in the Yukon River Basin (fig. 35). In the Canadian part of theYukon, Environment Canada began collecting water-quality datain 1980. Water chemistry samples were generally analyzed fornutrients and major ions. Some samples were analyzed for organiccarbon and trace elements. Common field properties (water temperature, specific conductance, pH, and dissolved oxygen) wereusually collected at the time of sampling. Currently, EnvironmentCanada is not collecting water-quality samples in the Yukon RiverBasin.

In the Alaska part of the Yukon River Basin, water-quality

sampling began in the 1950’s. Many of the sites were sampled onlyonce and some of the samples were collected by other Federalagencies or residents of a village who provided the results to theUSGS. Before and during the construction of the trans-Alaska oilpipeline in the 1970’s, water-quality samples were collected atmany sites along the route of the pipeline (fig. 35). In the mid tolate 1970’s, when the USGS implemented the NASQAN program,three sites were established in the Yukon River Basin: the YukonRiver at Eagle, the Tanana River at Nenana, and the Yukon Riverat Pilot Station. The site at Eagle was operated from 1978-79,

whereas the sites at Pilot Station and Nenan1976-96. Currently, no water-quality samptinely by the USGS in the Yukon River Bas

To gain a basic understanding of the w

istics of streams in the Yukon River Basin, thity data were analyzed. Before the interpretibegan, efforts were made to assess the qualiThe water-quality data were not obtained ution techniques at all sites. Laboratory animproved in recent years, resulting in lowsome analytes. In addition, the distribution site density is greater in the eastern and soutRiver Basin than in the northern and westeset of chemical determinations was not unperiod of record differs for each site, and thdistributed over the entire hydrologic cyclesubjective, only sites that had 10 or more saanalysis (fig. 36; table 11). Despite these limvide an interesting description of both the mRiver and some its major tributaries.

Similar to the suspended-sediment dat

quality measurements are available in USGeological Survey 1954-62, 1971, 1976, 19are also stored in electronic format in the Information System (NWIS). Water-quality dian Yukon are available in electronic formaweb (http://www.ec.gc.ca/water/index.htm)
WATER QUALITY SITES (AT LEAST 1 SAMPLE)

Figure 35. Location of water-quality sampling stations where one or more samples have been collected in the Yukon River Bas

TRANS-ALASKA PIPELINE

0

0 100

100

200

200

300 KILOMETERS

300 MILES
80 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Figure 36. Location of water-quality sampling stations where 10 or more samples have been collected in the Yukon River Basin (see t

Alaska RangeBoreal Mountains and PlateausBrooks RangeEagle PlainsInterior BottomlandsInterior Forested Lowlands & UplandsInterior HighlandsMackenzie MountainsOgilvie MountainsOld Crow Flats

Pelly Ruby SelwySubarWrangYukon Yukon Yukon Yukon Yukon 

70

69

6768

66

64-65

27 26

63

24

25

23

22 62

48-51

54 46-47 53

56-61

21 20

52 39,40,44,45

35-38

55

32 29 33 28 34 31

30

41

43

42

18

19

16

15

6 

WATER QUALITY SITES (10 SAMPLES OR MORE) AND ECOREGIONS

Other

0

0 100

100

200

200

300 KILOMETERS

300 MILES
Table 11. Water-quality stations in the Yukon River Basin with 10 or more years of record[--, watershed drains more than two ecoregions]

Map No.

(fig. 36)

USGS

station No. or 

latitude/longitude

Station name Primary ecoregions d

by watershed

1 15304850 Wheaton River near Carcross, YT Yukon Stikine Highlands2 6016421350156 Wheaton River at Annie Lake Road, YT Yukon Stikine Highlands3 6025001345300 Watson River at Annie Lake Road, YT Yukon Southern Lakes4 15305000 Yukon River at Whitehorse, YT --5 6036231345646 Wolf Creek at Alaska Highway near Whitehorse, YT Yukon Southern Lakes6 15305050 Takhini River near Whitehorse, YT Yukon Southern Lakes7 6050301351103 Takhini River at Klondike Highway, YT Yukon Southern Lakes8 15305100 Yukon River above Frank Creek, YT --9 6106151351730 Fox Creek at Klondike Highway, YT Yukon Southern Lakes

10 6104001351300 Deep Creek at Klondike Highway, YT Yukon Southern Lakes

11 6058451351030 Horse Creek at Klondike Highway, YT Yukon Southern Lakes

12 15305150 Swift River near Swift River, BC Boreal Mountains and Plateaus13 15305250 Teslin River near Teslin, YT Boreal Mountains and Plateaus14 5958181311439 Partridge Creek at mile 734 Alaska Highway, YT Boreal Mountains and Plateaus/Pelly M15 15305350 Yukon River at Carmacks, YT --16 15305420 Pelly River at Pelly Crossing, YT Yukon Plateau North/ Selwyn Mounta17 6211111331108 Blind Creek at Faro, YT Yukon Plateau North/Pelly Mountains18 6339281355530 Mayo River at Power Dam, YT Yukon Plateau North/Pelly Mountains19 15305620 Stewart River at Stewart Crossing, YT Yukon Plateau North/ Selwyn Mounta

Mountains

20 15305698 Klondike River above Bonanza Creek near Dawson, YT Yukon Plateau North/Mackenzie Mou21 15348000 Fortymile River near Steele Creek, AK Interior Highlands22 15356000 Yukon River at Eagle, AK --23 15388950 Porcupine River at Old Crow, YT Eagle Plains/Old Crow Flats/Oglivie M
82 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

24 15389500 Chandalar River near Venetie, AK Brooks Range25 15439800 Boulder Creek near Central, AK Interior Highlands26 15457800 Hess Creek near Livengood, AK Interior Forest Lowlands and Uplands27 15468000 Yukon River at Rampart, AK --28 15470000 Chisana River at Northway Junction, AK Wrangell Mountains/Interior Bottomla29 15472000 Tanana River near Tok Junction, AK Wrangell Mountains/Interior Bottomla30 15473500 Little Tok River near Tok Junction, AK Alaska Range31 15473900 Tok River on Slana Tok Highway near Tok Junction, AK Alaska Range32 15474000 Tok River near Tok Junction, AK Alaska Range/ Interior Forest Lowlan33 15476000 Tanana River near Tanacross, AK Wrangell Mountains/ Interior Bottoml34 15476100 Robertson River near Tanacross, AK Alaska Range35 15476300 Berry Creek near Dot Lake, AK Alaska Range36 15476500 Johnson River near Dot Lake, AK Alaska Range37 15476600 Little Gerstle River near Big Delta, AK Alaska Range38 15476700 Gerstle River near Big Delta, AK Alaska Range39 15477500 Clearwater Creek near Delta Junction, AK Interior Bottomlands40 15478000 Tanana River at Big Delta, AK --41 15478100 Delta River at Black Rapids, AK Alaska Range42 6312441453813 Phelan Creek at Richardson Highway near Paxson, AK Alaska Range43 6324121454355 Castner Creek near Black Rapids, AK Alaska Range44 6401251454325 Jarvis Creek near Delta Junction, AK Alaska Range/Interior Bottomlands45 6407351455000 Delta River near Big Delta, AK Alaska Range/Interior Bottomlands46 15484000 Salcha River near Salchaket, AK Interior Highlands47 6429101463900 Salcha River 8 mile above gage near Salchaket, AK Interior Highlands

Table 11. Water-quality stations in the Yukon River Basin with 10 or more years of record--Continued[--, watershed drains more than two ecoregions]

Map No.

(fig. 36)

USGS

station No. or 

latitude/longitude

Station name Primary ecoregions d

by watershed
48 15493500 Chena River near North Pole, AK Interior Highlands49 15511000 Little Chena River near Fairbanks, AK Interior Highlands/Interior Forest Low50 15514000 Chena River at Fairbanks, AK Interior Highlands/Interior Forest Low51 6450001473430 Chena River at Fort Wainwright, AK Interior Highlands/Interior Forest Low52 15479500 Shaw Creek near Delta Junction, AK Interior Highlands/Interior Bottomlan53 15514500 Wood River near Fairbanks, AK Alaska Range54 15515500 Tanana River at Nenana, AK Alaska Range55 15515800 Seattle Creek near Cantwell, AK Alaska Range56 15518000 Nenana River near Healy, AK Alaska Range57 15518040 Nenana River at Healy, AK Alaska Range58 15518350 Teklanika River near Lignite, AK Alaska Range59 6351061485322 Healy Creek below Moody Creek near Healy, AK Alaska Range60 6351291485659 Nenana River at Power Plant Intake near Healy, AK Alaska Range61 6351321485658 Nenana River 300 feet below Power Plant Intake near Healy, AK Alaska Range62 15535000 Caribou Creek near Chatanika, AK Interior Highlands63 15564877 Wiseman Creek at Wiseman, AK Brooks Range64 15564600 Melozitna River near Ruby, AK Interior Forest Lowlands and Uplands65 15564800 Yukon River at Ruby, AK --66 15564900 Koyukuk River at Hughes, AK Brooks Range/Interior Forest Lowland67 6239301601120 Yukon River at Anvik, AK --68 15565300 Innoko River at Shageluk, AK Interior Bottomlands69 15565447 Yukon River at Pilot Station, AK --70 6205051634345 Yukon River at Mountain Village, AK --

Table 11. Water-quality stations in the Yukon River Basin with 10 or more years of record--Continued[--, watershed drains more than two ecoregions]

Map No.

(fig. 36)

USGS

station No. or 

latitude/longitude

Station name Primary ecoregions d

by watershed
84 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Yukon River Main Stem

Ten or more water-quality samples have been collected at 70

sites in the Yukon River Basin (fig. 36; table 11). Twenty-one sitesare located in Canada and 49 in Alaska. Eight sites are locatedalong the main stem of the Yukon River between Whitehorse,Yukon Territory, and Mountain Village, Alaska. Eleven sites arelocated along rivers that discharge directly into the Yukon River,although these sites are not necessarily located at the mouth. TheYukon River at Pilot Station has been the longest continuouslymonitored site on the main stem of the Yukon River.

The water of the main stem of the Yukon River has relatively

low specific conductance ranging from about 60 to 257 

μS/cm

(table 12). The conductance increases downstream betweenWhitehorse, Yukon Territory and Rampart, Alaska, and decreasesslightly from Rampart to Mountain Village. Conductanceincreases of about 50 percent between Carmacks, Yukon Territoryand Eagle, Alaska, are most likely due to the input of dissolvedsolutes from three major tributaries between Carmacks and Eagle:the Pelly, White, and Stewart Rivers.

Specific conductance can also be used as a general measure

of the dissolved ion concentration and the same pattern is reflectedin both the major ion concentrations and the dissolved solids concentrations. Calcium and magnesium are the primary cations(table 12) with calcium accounting for about 70 percent of the cationic charge. Bicarbonate (calculated from alkalinity) and sulfateare the dominant anions, with bicarbonate accounting for about 80percent of the anionic charge.

Nutrient concentrations in the Yukon River are generally low

(less than 0.5 mg/L) throughout the river (table 12). Dissolvednitrate generally increases downstream with the highest concentrations measured at Pilot Station. Concentrations for total phosphorus were also relatively low (less than 0.5 mg/L). The highest

concentrations and greatest variability for measured at Eagle. 

Total organic carbon concentrations 

the course of the lower Yukon, nearly doublicentration of 2.3 mg/L at Yukon River at CaEagle and doubling again between Eagle a12). Dissolved organic carbon (DOC) data the Yukon River at Pilot Station. DOC conclower than TOC concentrations at Pilot Statconcentration of 6.4 mg/L. 

Total iron concentrations increase dow

River, from a median of 46 

μg/L at Whiteh

Pilot Station (table 12). The increase is greatand Eagle where the median concentration of magnitude from 280 to 2,200 

μg/L. Di

available only for the Yukon River at Pilot centration is an order-of-magnitude less t(table 12), indicating that the most iron is trment.

Total manganese concentrations in the 

about fourfold between Whitehorse and FrFrom this point, the concentration increases iron, the dissolved manganese concentratiomagnitude less than the total concentration, the manganese is transported either in the mform (table 12) with sediment.

Additional trace elements that show 

barium, total strontium, total arsenic, and tof total barium and total strontium nearly macks and Eagle (table 12). Total arsenidownstream from a median concentrations horse to 3 

μg/L at Pilot Station. Total alumi

Carmacks are three times higher than those 
Map

No. 

(fig. 

36)

Yukon River 

station name

Number 

of 

analyses

Mean

Percentile values 

calculated from the data

25 50 75

Specific conductance, microsiemens per centimeter at 25 degrees Celsius

4 At Whitehorse, YT 1155 79 60 88 948 Above Frank Creek, YT 21 100 96 100 103

15 At Carmacks, YT 1208 144 125 140 15322 At Eagle, AK (Canadian) 202 214 188 213 23522 At Eagle, AK (USGS) 81 213 187 204 23127 At Rampart, AK 120 230 207 234 25765 At Ruby, AK 106 216 189 217 23669 At Pilot Station, AK 111 209 173 202 22070 At Mountain Village, AK 18 198 108 198 203

Dissolved solids, residue on evaporation at 180 degrees Celsius, milligrams per liter

4 At Whitehorse, YT 144 78 58 67 878 Above Frank Creek, YT 17 62 60 60 60

15 At Carmacks, YT 553 104 84 96 11322 At Eagle, AK (Canadian) 144 153 133 151 17022 At Eagle, AK (USGS) 69 130 113 143 14327 At Rampart, AK 118 136 123 138 15365 At Ruby, AK 107 126 108 127 13869 At Pilot Station, AK 105 123 102 119 13070 At Mountain Village, AK 17 113 104 112 118

pH, standard units

4 At Whitehorse, YT 1160 7.6 8 Above Frank Creek, YT 17 7.8 

15 At Carmacks, YT 113 7.9 22 At Eagle, AK (Canadian) 46 7.9 22 At Eagle, AK (USGS) 75 7.6 27 At Rampart, AK 115 7.5 65 At Ruby, AK 103 7.7 69 At Pilot Station, AK 106 7.5 70 At Mountain Village, AK 17 7.1 

Water temperature, degrees C

4 At Whitehorse, YT 1080 12.5 8 Above Frank Creek, YT 18 6.2 

15 At Carmacks, YT 1055 12.5 22 At Eagle, AK (Canadian) 292 11.9 22 At Eagle, AK (USGS) 49 9.6 27 At Rampart, AK 25 6.9 65 At Ruby, AK 39 7.8 69 At Pilot Station, AK 91 9.1 70 At Mountain Village, AK -- -- 

Map

No. 

(fig. 

36)

Yukon River 

station name

Number 

of 

analyses

Mean

Table 12. Summary statistics for selected properties and constituents of surface-water samples from stations along the Yu[--, no data]
86 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Dissolved-oxygen concentration, milligrams per liter

4 At Whitehorse, YT -- -- -- -- --8 Above Frank Creek, YT -- -- -- -- --

15 At Carmacks, YT -- -- -- -- --22 At Eagle, AK (Canadian) -- -- -- -- --22 At Eagle, AK (USGS) -- -- -- -- --27 At Rampart, AK -- -- -- -- --65 At Ruby, AK -- -- -- -- --69 At Pilot Station, AK 68 8.1 7.7 9.1 10.170 At Mountain Village, AK -- -- -- -- --

Calcium concentration, milligrams per liter

4 At Whitehorse, YT 459 13.8 13.3 13.9 14.38 Above Frank Creek, YT -- -- -- -- --

15 At Carmacks, YT 412 19.7 18.1 19.6 21.122 At Eagle, AK (Canadian) 106 31 28 30 3322 At Eagle, AK (USGS) 69 31 26 28 3427 At Rampart, AK 118 31 28 32 3565 At Ruby, AK 107 32 27 32 3669 At Pilot Station, AK 109 31 25 29 3270 At Mountain Village, AK 17 28 25 28 30

Map

No. 

(fig. 

36)

Yukon River 

station name

Number 

of 

analyses

Mean

Percentile values 

calculated from the data

25 50 75

Magnesium concentration, milligram

4 At Whitehorse, YT 100 2.4 8 Above Frank Creek, YT -- -- 

15 At Carmacks, YT 79 4.3 22 At Eagle, AK (Canadian) 106 7.8 22 At Eagle, AK (USGS) 69 8.0 27 At Rampart, AK 118 8.8 65 At Ruby, AK 108 6.2 69 At Pilot Station, AK 109 6.7 70 At Mountain Village, AK 17 5.5 

Sodium concentration, milligrams 

4 At Whitehorse, YT 460 1.1 8 Above Frank Creek, YT -- -- 

15 At Carmacks, YT 412 1.6 22 At Eagle, AK (Canadian) 110 2.6 22 At Eagle, AK (USGS) 53 2.6 27 At Rampart, AK 118 3.3 65 At Ruby, AK 108 2.6 69 At Pilot Station, AK 109 2.5 70 At Mountain Village, AK 18 3.3 

Map

No. 

(fig. 

36)

Yukon River 

station name

Number 

of 

analyses

Mean

Table 12. Summary statistics for selected properties and constituents of surface-water samples from stations along the Yu[--, no data]
Potassium concentration, milligrams per liter

4 At Whitehorse, YT 460 0.6 0.6 0.6 0.78 Above Frank Creek, YT -- -- -- -- --

15 At Carmacks, YT 412 0.8 0.6 0.7 0.822 At Eagle, AK (Canadian) 108 1.3 0.97 1.1 1.322 At Eagle, AK (USGS) 52 1.4 0.95 1.2 1.727 At Rampart, AK 118 1.1 1.0 1.1 1.365 At Ruby, AK 108 1.2 1.1 1.2 1.469 At Pilot Station, AK 109 1.3 1.0 1.2 1.470 At Mountain Village, AK 18 1.0 0.7 0.95 1.3

Total alkalinity, as CaCO3, milligrams per liter

4 At Whitehorse, YT 633 40 37 41 428 Above Frank Creek, YT 18 43 41 42 43

15 At Carmacks, YT 648 62 57 62 6622 At Eagle, AK (Canadian) 197 93 79 88 10222 At Eagle, AK (USGS) 73 89 75 82 9927 At Rampart, AK 108 88 79 89 9665 At Ruby, AK 116 91 77 91 10169 At Pilot Station, AK 87 83 64 76 8470 At Mountain Village, AK 18 76 66 76 83

Map

No. 

(fig. 

36)

Yukon River 

station name

Number 

of 

analyses

Mean

Percentile values 

calculated from the data

25 50 75

Sulfate concentration, milligrams 

4 At Whitehorse, YT 634 5.8 8 Above Frank Creek, YT 18 5.6 

15 At Carmacks, YT 648 8.1 22 At Eagle, AK (Canadian) 197 25 22 At Eagle, AK (USGS) 70 26 27 At Rampart, AK 118 29 65 At Ruby, AK 116 20 69 At Pilot Station, AK 107 22 70 At Mountain Village, AK 18 20 

Chloride concentration, milligram

4 At Whitehorse, YT 634 0.3 8 Above Frank Creek, YT 18 0.3 

15 At Carmacks, YT 648 0.5 22 At Eagle, AK (Canadian) 197 0.9 22 At Eagle, AK (USGS) 69 1.1 27 At Rampart, AK 101 1.2 65 At Ruby, AK -- -- 69 At Pilot Station, AK 110 1.1 70 At Mountain Village, AK 18 1.2 

Map

No. 

(fig. 

36)

Yukon River 

station name

Number 

of 

analyses

Mean

Table 12. Summary statistics for selected properties and constituents of surface-water samples from stations along the Yu[--, no data]
88 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Dissolved silica concentration, milligrams per liter

4 At Whitehorse, YT 160 1.5 1.4 1.4 1.68 Above Frank Creek, YT 18 1.7 1.6 1.7 1.8

15 At Carmacks, YT 215 2.8 2.6 2.8 3.0422 At Eagle, AK (Canadian) 197 3.6 3.3 3.6 4.022 At Eagle, AK (USGS) 69 7.3 6.2 7.2 8.127 At Rampart, AK 118 6.6 5.8 6.5 7.665 At Ruby, AK 108 7.1 6.1 7.1 8.169 At Pilot Station, AK 109 7.5 5.9 6.9 8.170 At Mountain Village, AK 17 7.4 6.8 7.0 7.5

Dissolved nitrate plus nitrite concentration, as nitrogen, milligrams per liter

4 At Whitehorse, YT 2074 0.08 0.006 0.017 0.0318 Above Frank Creek, YT 47 0.019 0.006 0.022 0.031

15 At Carmacks, YT 2070 0.06 0.024 0.05 0.0722 At Eagle, AK (Canadian) 661 0.21 0.046 0.093 0.1722 At Eagle, AK (USGS) -- -- -- -- --27 At Rampart, AK -- -- -- -- --65 At Ruby, AK -- -- -- -- --69 At Pilot Station, AK 62 0.15 0.10 0.10 0.2070 At Mountain Village, AK -- -- -- -- --

Map

No. 

(fig. 

36)

Yukon River 

station name

Number 

of 

analyses

Mean

Percentile values 

calculated from the data

25 50 75

Total phosphorus concentration, as phosphoru

4 At Whitehorse, YT 1991 0.008 8 Above Frank Creek, YT 50 0.019 

15 At Carmacks, YT 1984 0.03 22 At Eagle, AK (Canadian) 596 0.28 22 At Eagle, AK (USGS) -- -- 27 At Rampart, AK -- -- 65 At Ruby, AK -- -- 69 At Pilot Station, AK 84 0.02 70 At Mountain Village, AK -- -- 

Total organic carbon, as carbon, millig

4 At Whitehorse, YT 515 1.9 8 Above Frank Creek, YT 17 1.7 

15 At Carmacks, YT 531 3.0 22 At Eagle, AK (Canadian) 154 5.4 22 At Eagle, AK (USGS) -- -- 27 At Rampart, AK -- -- 65 At Ruby, AK -- -- 69 At Pilot Station, AK 15 10.5 70 At Mountain Village, AK -- -- 

Map

No. 

(fig. 

36)

Yukon River 

station name

Number 

of 

analyses

Mean

Table 12. Summary statistics for selected properties and constituents of surface-water samples from stations along the Yu[--, no data]
Total iron concentration, as iron, micrograms per liter

4 At Whitehorse, YT 428 102 25 46 1008 Above Frank Creek, YT 17 54 28 42 48

15 At Carmacks, YT 449 646 116 280 71222 At Eagle, AK (Canadian) 141 6812 100 2200 962022 At Eagle, AK (USGS) -- -- -- -- --27 At Rampart, AK -- -- -- -- --65 At Ruby, AK -- -- -- -- --69 At Pilot Station, AK 27 7620 1600 5900 1100070 At Mountain Village, AK -- -- -- -- --

Total manganese, as manganese, micrograms per liter

4 At Whitehorse, YT 428 6.5 2 4 9.28 Above Frank Creek, YT 17 2.1 1.2 1.7 2.7

15 At Carmacks, YT 449 19 5 10 2222 At Eagle, AK (Canadian) 141 155 5 69 24022 At Eagle, AK (USGS) -- -- -- -- --27 At Rampart, AK -- -- -- -- --65 At Ruby, AK -- -- -- -- --69 At Pilot Station, AK 27 206 120 160 28070 At Mountain Village, AK -- -- -- -- --

Map

No. 

(fig. 

36)

Yukon River 

station name

Number 

of 

analyses

Mean

Percentile values 

calculated from the data

25 50 75

Dissolved iron, as iron, microgram

4 At Whitehorse, YT -- -- 8 Above Frank Creek, YT -- -- 

15 At Carmacks, YT -- -- 22 At Eagle, AK (Canadian) -- -- 22 At Eagle, AK (USGS) -- -- 27 At Rampart, AK -- -- 65 At Ruby, AK -- -- 69 At Pilot Station, AK 76 238 70 At Mountain Village, AK -- -- 

Dissolved manganese, as manganese, micr

4 At Whitehorse, YT -- -- 8 Above Frank Creek, YT -- -- 

15 At Carmacks, YT -- -- 22 At Eagle, AK (Canadian) -- -- 22 At Eagle, AK (USGS) -- -- 27 At Rampart, AK -- -- 65 At Ruby, AK -- -- 69 At Pilot Station, AK 76 46 70 At Mountain Village, AK -- -- 

Map

No. 

(fig. 

36)

Yukon River 

station name

Number 

of 

analyses

Mean

Table 12. Summary statistics for selected properties and constituents of surface-water samples from stations along the Yu[--, no data]
90 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Total barium, as barium, micrograms per liter

4 At Whitehorse, YT 175 27 26 27 288 Above Frank Creek, YT 17 26 24 26 26

15 At Carmacks, YT 238 38 33 35 3822 At Eagle, AK (Canadian) 80 104 57 86 13322 At Eagle, AK (USGS) -- -- -- -- --27 At Rampart, AK -- -- -- -- --65 At Ruby, AK -- -- -- -- --69 At Pilot Station, AK -- -- -- -- --70 At Mountain Village, AK -- -- -- -- --

Total strontium, as strontium, micrograms per liter

4 At Whitehorse, YT 175 74 73 74 778 Above Frank Creek, YT 17 79 76 79 81

15 At Carmacks, YT 238 95 87 96 10322 At Eagle, AK (Canadian) 141 168 152 167 19422 At Eagle, AK (USGS) -- -- -- -- --27 At Rampart, AK -- -- -- -- --65 At Ruby, AK -- -- -- -- --69 At Pilot Station, AK -- -- -- -- --70 At Mountain Village, AK -- -- -- -- --

Map

No. 

(fig. 

36)

Yukon River 

station name

Number 

of 

analyses

Mean

Percentile values 

calculated from the data

25 50 75

Total arsenic, as arsenic, microgram

4 At Whitehorse, YT 374 0.4 8 Above Frank Creek, YT 17 0.3 

15 At Carmacks, YT 398 0.4 22 At Eagle, AK (Canadian) 144 2.6 22 At Eagle, AK (USGS) -- -- 27 At Rampart, AK -- -- 65 At Ruby, AK -- -- 69 At Pilot Station, AK 27 4 70 At Mountain Village, AK -- -- 

Total aluminum, as aluminum, microgr

4 At Whitehorse, YT 175 67 8 Above Frank Creek, YT 17 51 

15 At Carmacks, YT 238 408 22 At Eagle, AK (Canadian) 80 4458 22 At Eagle, AK (USGS) -- -- 27 At Rampart, AK -- -- 65 At Ruby, AK -- -- 69 At Pilot Station, AK -- -- 70 At Mountain Village, AK -- -- 

Map

No. 

(fig. 

36)

Yukon River 

station name

Number 

of 

analyses

Mean

Table 12. Summary statistics for selected properties and constituents of surface-water samples from stations along the Yu[--, no data]
Map 

No. 

(fig. 

36)

Stream-gaging station

No. of 

analyses Mean

Percentile values 

calculated from 

the data

25 50 75

Specific conductance, microsiemens per centimeter at 25 degrees Celsius

13 Teslin River near Teslin, YT 124 127 123 129 13616 Pelly River at Pelly Crossing, YT 46 274 237 288 36119 Stewart River at Stewart Crossing, YT 59 306 277 322 37020 Klondike River above Bonanza Creek 

near Dawson, YT

86 253 201 245 295

21 Fortymile River near Steele Creek, AK 13 145 119 149 16623 Porcupine River at Old Crow, YT 89 262 191 276 37324 Chandalar River near Venetie, AK 28 221 189 225 25254 Tanana River at Nenana, AK 213 243 211 235 28464 Melozitna River near Ruby, AK 28 86 54 72 12766 Koyukuk River at Hughes, AK 43 213 171 215 25868 Innoko River at Shageluk, AK 16 101 80 97 139

Calcium concentration, milligrams 

13 Teslin River near Teslin, YT 86 16 Pelly River at Pelly Crossing, YT 46 19 Stewart River at Stewart Crossing, YT 59 20 Klondike River above Bonanza Creek 

near Dawson, YT

85 

21 Fortymile River near Steele Creek, AK 11 23 Porcupine River at Old Crow, YT 89 24 Chandalar River near Venetie, AK 16 54 Tanana River at Nenana, AK 151 64 Melozitna River near Ruby, AK 18 66 Koyukuk River at Hughes, AK 23 68 Innoko River at Shageluk, AK 16 

Map 

No. 

(fig. 

36)

Stream-gaging station

No. of 

analyses Mea

The chemistry of the Yukon River reflects the chemical

inputs from its major tributaries. The waters of the tributaries tothe Yukon are predominantly calcium magnesium bicarbonatewaters with specific conductance ranging from 54 to 373 μS/cm(table 13). Of the 11 tributaries with water-quality data, 6 siteshave data for constituents other than the major ions. These limiteddata show that nitrate concentrations are highest in the Tanana andPorcupine Rivers (table 13). The Tanana River also has the highest

total-phosphorus concentrations with a me0.17 mg/L phosphorous. Median TOC con1.2 mg/L for the Stewart and Klondike RivPorcupine River (table 13). Concentrations total manganese, with median concentratiμg/L respectively (table 13), are highest in haps reflecting the presence of glaciers. 

Table 13. Summary statistics for selected properties and constituents of surface-water samples from tributaries of the Yuk[--, no data]
92 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Magnesium concentration, milligrams per liter

13 Teslin River near Teslin, YT 63 4.6 4.6 4.8 4.916 Pelly River at Pelly Crossing, YT 46 12 10 12 1519 Stewart River at Stewart Crossing, YT 59 13 12 15 1620 Klondike River above Bonanza Creek 

near Dawson, YT

85 11 7.9 9.9 13

21 Fortymile River near Steele Creek, AK 11 5.8 4.8 5.5 6.723 Porcupine River at Old Crow, YT 89 8.6 6.3 9.3 1124 Chandalar River near Venetie, AK 16 5.8 4.8 6.2 7.154 Tanana River at Nenana, AK 151 7.4 6.0 7.2 9.064 Melozitna River near Ruby, AK 18 3.4 2.2 2.6 4.966 Koyukuk River at Hughes, AK 23 7.7 6.2 7.4 9.068 Innoko River at Shageluk, AK 16 3.5 2.6 3.7 4.3

Total alkalinity, as CaCO3, milligrams per liter

13 Teslin River near Teslin, YT 119 59 55 58 5916 Pelly River at Pelly Crossing, YT 46 99 79 104 11719 Stewart River at Stewart Crossing, YT 59 100 81 98 12920 Klondike River above Bonanza Creek 

near Dawson, YT

85 82 66 79 95

21 Fortymile River near Steele Creek, AK 13 50 43 52 5623 Porcupine River at Old Crow, YT 89 98 51 82 15624 Chandalar River near Venetie, AK 16 107 90 105 12854 Tanana River at Nenana, AK 139 96 81 92 11864 Melozitna River near Ruby, AK 19 36 21 29 5766 Koyukuk River at Hughes, AK 24 86 57 78 7968 Innoko River at Shageluk, AK 15 41 31 41 55

Map 

No. 

(fig. 

36)

Stream-gaging station

No. of 

analyses Mean

Percentile values 

calculated from 

the data

25 50 75

Sulfate concentration, milligram

13 Teslin River near Teslin, YT 33 6.2 16 Pelly River at Pelly Crossing, YT 46 41 19 Stewart River at Stewart Crossing, YT 59 58 20 Klondike River above Bonanza Creek

near Dawson, YT

85 47 

21 Fortymile River near Steele Creek, AK 11 24 23 Porcupine River at Old Crow, YT 89 32 24 Chandalar River near Venetie, AK 16 16 54 Tanana River at Nenana, AK 155 29 64 Melozitna River near Ruby, AK 18 7.8 66 Koyukuk River at Hughes, AK 23 26 68 Innoko River at Shageluk, AK 15 7.4 

Dissolved nitrate plus nitrate concentration, as nit

13 Teslin River near Teslin, YT 427 0.016 Pelly River at Pelly Crossing, YT 77 0.019 Stewart River at Stewart Crossing, YT 91 0.020 Klondike River above Bonanza Creek 

near Dawson, YT

84 0.1

21 Fortymile River near Steele Creek, AK -- -- 23 Porcupine River at Old Crow, YT 109 0.124 Chandalar River near Venetie, AK -- -- 54 Tanana River at Nenana, AK 39 0.164 Melozitna River near Ruby, AK -- -- 66 Koyukuk River at Hughes, AK -- -- 68 Innoko River at Shageluk, AK -- -- 

Map 

No. 

(fig. 

36)

Stream-gaging station

No. of 

analyses Me

Table 13. Summary statistics for selected properties and constituents of surface-water samples from tributaries of the Yuko[--, no data]
Total phosphorus concentration, as phosphorus, milligrams per liter 

13 Teslin River near Teslin, YT 420 0.013 0.006 0.008 0.01316 Pelly River at Pelly Crossing, YT 100 0.114 0.009 0.022 0.05019 Stewart River at Stewart Crossing, YT 115 0.111 0.005 0.020 0.07620 Klondike River above Bonanza Creek 

near Dawson, YT

151 0.034 0.003 0.005 0.015

21 Fortymile River near Steele Creek, AK -- -- -- -- --23 Porcupine River at Old Crow, YT 166 0.017 0.002 0.007 0.01824 Chandalar River near Venetie, AK -- -- -- -- --54 Tanana River at Nenana, AK 80 0.240 0.12 0.17 0.264 Melozitna River near Ruby, AK -- -- -- -- --66 Koyukuk River at Hughes, AK -- -- -- -- --68 Innoko River at Shageluk, AK -- -- -- -- --

Total organic carbon, as carbon, milligrams per liter

13 Teslin River near Teslin, YT 15 4.68 3.3 4.1 4.716 Pelly River at Pelly Crossing, YT 44 4.5 1.7 3.2 4.919 Stewart River at Stewart Crossing, YT 59 2.1 0.5 1.2 220 Klondike River above Bonanza Creek 

near Dawson, YT

84 3.3 0.5 1.2 2.3

21 Fortymile River near Steele Creek, AK -- -- -- -- --23 Porcupine River at Old Crow, YT 85 6.3 0.5 5.5 10.924 Chandalar River near Venetie, AK -- -- -- -- --54 Tanana River at Nenana, AK 14 5.8 2.8 5.3 7.564 Melozitna River near Ruby, AK -- -- -- -- --66 Koyukuk River at Hughes, AK -- -- -- -- --68 Innoko River at Shageluk, AK -- -- -- -- --

Map 

No. 

(fig. 

36)

Stream-gaging station

No. of 

analyses Mean

Percentile values 

calculated from 

the data

25 50 75

Total iron concentration, as iron, m

13 Teslin River near Teslin, YT 109 16 Pelly River at Pelly Crossing, YT 46 219 Stewart River at Stewart Crossing, YT 59 120 Klondike River above Bonanza Creek 

near Dawson, YT

97 

21 Fortymile River near Steele Creek, AK -- 23 Porcupine River at Old Crow, YT 86 24 Chandalar River near Venetie, AK -- 54 Tanana River at Nenana, AK 19 1364 Melozitna River near Ruby, AK -- 66 Koyukuk River at Hughes, AK -- 68 Innoko River at Shageluk, AK -- 

Total manganese, as manganese, m

13 Teslin River near Teslin, YT 86 5.0 16 Pelly River at Pelly Crossing, YT 109 72 19 Stewart River at Stewart Crossing, YT 59 60 20 Klondike River above Bonanza Creek 

near Dawson, YT

97 24 

21 Fortymile River near Steele Creek, AK -- -- 23 Porcupine River at Old Crow, YT 86 14 24 Chandalar River near Venetie, AK -- -- 54 Tanana River at Nenana, AK 19 362 64 Melozitna River near Ruby, AK -- -- 66 Koyukuk River at Hughes, AK -- -- 68 Innoko River at Shageluk, AK -- -- 

Map 

No. 

(fig. 

36)

Stream-gaging station

No. of 

analyses Me

Table 13. Summary statistics for selected properties and constituents of surface-water samples from tributaries of the Yuko[--, no data]
94 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Temporal Variations in Water Quality

The rivers of the Yukon Basin are generally ice covered from

mid-to-late October to mid-to-late May. During this period of lowflow, glacial and surface runoff is minimal to non-existent andbaseflow predominates. Comparing the water-quality data collected during periods of ice cover with the water-quality data collected during open-water periods indicated a slight basinwideincrease in median specific conductance under ice compared tothat in the open water (fig. 37). Specific conductance increasesdown the Yukon River from Whitehorse to Pilot Station duringboth the open-water and ice-covered periods (fig. 37). 

Substantial differences are found between the two seasons at

the Yukon River at Pilot Station (table 14). Concentrations of calcium, magnesium, silica, and bicarbonate are almost twice as highduring ice cover than during open water (probably due to ionexclusion under freezing conditions). However, sulfate concentrations do not increase significantly. Dissolved oxygen decreasessignificantly between the two seasons with a median open-waterand under-ice dissolved oxygen concentrations of 9.3 and 2.7mg/L, respectively. The median DOC concentration also decreasesunder ice from 7.5 to 4.3 mg/L. The trace elements total iron, dissolved iron, and total arsenic decreased under ice conditions, butconcentrations of the trace elements dissolved manganese and dissolved strontium increased under ice (table 14). 

View of the water-worked basin of the Yukowhich is covered by numerous thaw and oxprecipitation is insufficient to maintain manreplenished by yearly flooding of the Yuflowing from east to west).
(117) (85)

0

500

100200300400

EXPLANATION

25th percentileMedian75th percentileinterquartile range outside the quartile Data value less than or equal to 1.5 times theinterquartile range outside the quartileand more than 1.5 times the Outlier data value less than or equal to 3interquartile range outside the quartileOutlier data value more than 3 times the

(117) Number of observations

Eagle (318) (306)

0

500

100200300400

(315) (328)

0

500

100200300400

(114) (14)

open ice 0

500

100200300400

(103) 

0

500

100200300400

Whitehorse Carmacks 

(318) (56)

0

500

100200300400

Ruby Pilot

SPECIFIC CONDUCTANCE, 

IN MICROSIEMENS PER CENTIMETER AT 25 DEGREES CELSIUS

Figure 37. Boxplots of specific conductance from samples taken during open water and under ice cover on t

open ice

open ice

open ice open ice open 
96 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Property or 

constituent 

(unit)

Season No. sam- ples Mean Median aQ1 bQ3 c

p

Suspended sediment (mg/L)

Ice 19 5.8 5 4 7 0.0001

Open 48 309 279 201 386

Specific conductance (μS/cm)

Ice 24 299 299 289 305 0.0001

Open 87 184 190.6 163.5 210

pH Ice 23 7.1 7.1 7.0 7.3 0.0001

Open 83 7.6 7.7 7.5 7.8

Dissolved oxygen (mg/L)

Ice 17 3.4 2.7 2.4 3.6 0.0001

Open 51 9.6 9.3 8.7 10.3

Alkalinity (mg/L as CaCO3) 

Ice 17 139 140 134 144 0.0001

Open 70 70 73.5 61 82

Calcium (mg/L as Ca)

Ice 23 45.4 46 45 47 0.0001

Open 86 26.9 27 24 30

Magnesium (mg/L as Mg)

Ice 23 10.1 10 9.9 11 0.0001

Open 86 5.8 6.1 4.4 6.8

Sulfate (mg/L as SO4) 

Ice 22 21.8 21.2 20.5 24 0.3999

Open 85 23.1 23 18 27

Silica (mg/L as SiO2) 

Ice 23 12 12 12 13 0.0001

Open 86 6.3 6.7 5.6 7.1

Arsenic, total (μg/L as As) 

Ice 7 1.6 2 1 2 0.0011

Open 20 4.7 4 3 6

Iron, total (μg/L as Fe)

Ice 7 1419 1500 

Open 20 9791 8332 

Iron, dissolved(μg/L as Fe)

Ice 19 201 90 

Open 57 250 220 

Manganese, total(μg/L as Mn)

Ice 7 138.6 130 

Open 20 230 200 

Manganese, dissolved (μg/L as Mn)

Ice 19 133 130 

Open 57 17.8 10 

Strontium, dissolved (μg/L as Sr)

Ice 13 189 190 

Open 37 106.8 110 

Nitrate + nitrite, dissolved (mg/L as N)

Ice 17 0.21 0.21 

Open 45 0.12 0.1 

Phosphorus, total (mg/L as P)

Ice 24 0.02 0.02 

Open 60 0.21 0.18 

Dissolved organic carbon (mg/L as C)

Ice 4 4.4 4.3 

Open 15 9.46 7.5 

a25th percentile b75th percentile cThe attained significance level of the data

Property or 

constituent 

(unit)

Season No. sam- ples Mean Median 

Table 14. Comparison of samples taken during open water and under ice cover, Yukon River at Pilot Station (map No. 69, [mg/L, milligram per liter; μg/L, microgram per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius]
Spatial Variations in Water Quality

In the Yukon River Basin, most, if not all, of the chemical

composition of the water is influenced by natural features such asgeology, soils, and climate. One of the central concepts of ecoregions is to define areas that have these same natural features. As ameans of describing the water quality of the Yukon River Basin,both spatially and in relation to the natural features, the existingwater-quality data were grouped and analyzed within the ecoregions of the Yukon River Basin. Although there is not sufficientdata for statistical analysis, some general observations can bemade.

The primary ecoregions composing the watershed area of the

rivers in the Yukon River Basin (fig. 16) where water-quality dataare available were determined (table 11). Drainage basins for 42sites reside in only one ecoregion. Watershed areas for the remaining 29 sites reside in two or more ecoregions. Water-quality datafor these 29 sites were not used in this analysis. Of the 42 sites having drainage basins in only one ecoregion, 8 of the 20 ecoregionsof the Yukon River Basin are represented: Yukon Stikine Highlands, Yukon Southern Lakes, Boreal Mountains and Plateaus,Interior Highlands, Interior Bottomlands, Brooks Range, AlaskaRange, and Interior Forested Lowlands and Uplands. Nineteensites received drainage from the Alaska Range, seven from theYukon Southern Lakes, six from the Interior Highlands, and twoeach from the other five ecoregions.

Calcium is the dominant cation in waters from all ecoregions

and bicarbonate is the dominant anion in all ecoregions except theBoreal Mountains and Plateaus ecoregion, where sulfate is themain anion (table 15). The major ion composition for eight ecoregions is consistent with the dissolution of carbonate minerals, suchas calcite and dolomite, with a greater contribution from sulfatecontaining minerals, such as gypsum, in the Boreal Mountains andPlateaus ecoregion.

Nutrient concentrations were low in al

for the Yukon River Basin. Dissolved nitrhigher in the Interior Bottomlands, InterioAlaska Range ecoregions than in the Yukon Yukon Southern Lakes, and the Boreal Mecoregions of the upper basin (table 15). Totrations were lower in the Yukon Stikine Hiother ecoregions. 

The TOC concentrations were higher 

lands and the Boreal Mountains and Plateathe Yukon Stikine Highlands, the Yukon Alaska Range ecoregions. One possibility concentrations of TOC is the fact that thedominated by organic soils. The only ecoreavailable are the Interior Highlands and thDOC concentrations are highest in the Integion, most likely reflecting the presence of o

Iron is an essential trace element for b

and concentrations in water are strongly depoxidation intensity of the water. Total irowidely between the ecoregions, with an inning from 14 to 126 

μg/L for the Yukon Stiki

11,000 

μg/L for the Alaska Range (table 15

of the Yukon River Basin are generally welneutral, the total iron concentrations most concentration transported as mineral matedroxide. Concentration data for both total available only for the Brooks Range and the gions. The dissolved concentrations for the order-of-magnitude to several orders-of-mtheir total iron concentrations (table 15). 
98 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Ecoregion

(fig. 36)

No. of 

analyses Mean

Percentile values 

calculated from the data

25 50 75

Specific conductance, microsiemens per centimeter at 25 degrees Celsius

Yukon Stikine Highlands 139 105 72 108 140Yukon Southern Lakes 641 195 108 185 288Boreal Mountains and Plateaus 163 115 100 125 133Interior Highlands 177 116 83 122 150Interior Bottomlands 31 203 97 153 312Brooks Range 37 245 194 233 291Alaska Range 1044 241 200 234 282Interior Forested Lowlands & Uplands 50 153 72 154 225

Dissolved solids, residue on evaporation at 180 degrees Celsius, milligrams per liter

Yukon Stikine Highlands 94 71 58 70 90Yukon Southern Lakes 593 141 100 130 200Boreal Mountains and Plateaus 53 84 70 90 94Interior Highlands 114 71 52 75 91Interior Bottomlands 25 106 51 79 179Brooks Range 23 148 115 137 174Alaska Range 966 148 121 142 173Interior Forested Lowlands & Uplands 34 91 46 88 128

pH, standard units

Yukon Stikine Highlands 222 7.6 7.5 7.7 7.8Yukon Southern Lakes 751 7.9 7.6 7.8 8.0Boreal Mountains and Plateaus 174 7.6 7.2 7.8 8.0Interior Highlands 137 7.2 7.0 7.3 7.5Interior Bottomlands 29 7.2 7.0 7.3 7.6Brooks Range 28 7.9 7.8 7.9 8.1Alaska Range 994 7.6 7.4 7.6 7.8Interior Forested Lowlands & Uplands 36 7.4 7.0 7.5 7.9

Water temperature, degrees Ce

Yukon Stikine Highlands 159 5.9 Yukon Southern Lakes 394 6.0 Boreal Mountains and Plateaus 174 5.3 Interior Highlands 157 5.5 Interior Bottomlands 16 3.8 Brooks Range 34 6.8 Alaska Range 516 5.8 Interior Forested Lowlands & Uplands 37 6.7 

Dissolved-oxygen concentration, milligr

Yukon Stikine Highlands -- -- Yukon Southern Lakes -- -- Boreal Mountains and Plateaus -- -- Interior Highlands 49 10.3 Interior Bottomlands -- -- Brooks Range 3 12.4 Alaska Range 138 11 Interior Forested Lowlands & Uplands -- -- 

Calcium concentration, milligrams 

Yukon Stikine Highlands 12 11.7 Yukon Southern Lakes 499 34.5 Boreal Mountains and Plateaus 115 16.6 Interior Highlands 117 15.2 Interior Bottomlands 26 24.7 Brooks Range 23 41 Alaska Range 968 33.9 Interior Forested Lowlands & Uplands 34 24 

Ecoregion

(fig. 36)

No. of 

analyses Mean

Table 15. Summary statistics for selected properties and constituents of surface-water samples by ecoregion[--, no data]
Magnesium concentration, milligrams per liter

Yukon Stikine Highlands 12 1.1 0.9 1.0 1.4Yukon Southern Lakes 499 8.9 5.8 7.9 11.9Boreal Mountains and Plateaus 78 4.2 3.9 4.7 4.9Interior Highlands 117 3.9 2.6 4.3 5.2Interior Bottomlands 26 5.4 3.4 4.6 8.5Brooks Range 23 7.5 5.1 6.7 8.1Alaska Range 969 8.2 5.7 7.3 9.3Interior Forested Lowlands & Uplands 34 4.4 2.5 4.7 6.7

Sodium concentration, milligrams per liter

Yukon Stikine Highlands 12 1.4 1.1 1.4 1.7Yukon Southern Lakes -- -- -- -- --Boreal Mountains and Plateaus 115 1.3 1.3 1.4 1.5Interior Highlands 107 1.7 1.2 1.6 1.9Interior Bottomlands 26 2.7 1.8 2.3 3.7Brooks Range 23 1.0 0.7 0.8 1.2Alaska Range 846 3.9 2.4 3.8 5.1Interior Forested Lowlands & Uplands 34 1.8 0.8 1.3 2

Potassium concentration, milligrams per liter

Yukon Stikine Highlands 12 0.5 0.5 0.6 0.6Yukon Southern Lakes 201 1.2 0.9 1 1.3Boreal Mountains and Plateaus 115 0.5 0.5 0.6 0.6Interior Highlands 107 0.9 0.7 0.9 1Interior Bottomlands 26 1.3 0.8 1 2.1Brooks Range 23 0.70 0.4 0.6 1Alaska Range 846 1.7 1.3 1.7 2.1Interior Forested Lowlands & Uplands 34 0.6 0.3 0.5 0.9

Ecoregion

(fig. 36)

No. of 

analyses Mean

Percentile values 

calculated from the data

25 50 75

Total alkalinity, as CaCO3, milligram

Yukon Stikine Highlands 149 40 Yukon Southern Lakes 676 87 Boreal Mountains and Plateaus 163 53 Interior Highlands 136 41.5 Interior Bottomlands 28 79 Brooks Range 27 100 Alaska Range 981 88 Interior Forested Lowlands & Uplands 35 68 

Sulfate concentration, milligrams p

Yukon Stikine Highlands 149 13 Yukon Southern Lakes 674 16 Boreal Mountains and Plateaus 163 5.7 Interior Highlands 117 15 Interior Bottomlands 25 18 Brooks Range 23 32 Alaska Range 983 36 Interior Forested Lowlands & Uplands 34 12 

Chloride concentration, milligram 

Yukon Stikine Highlands 149 0.3 Yukon Southern Lakes 675 0.6 Boreal Mountains and Plateaus 163 0.3 Interior Highlands 117 0.8 Interior Bottomlands 26 0.6 Brooks Range 23 0.7 Alaska Range 979 1.9 Interior Forested Lowlands & Uplands 34 1.1 

Ecoregion

(fig. 36)

No. of 

analyses Mean

Table 15. Summary statistics for selected properties and constituents of surface-water samples by ecoregion--Continued[--, no data]
100 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Dissolved-silica concentration, milligrams per liter

Yukon Stikine Highlands 123 2.9 2.6 3 3.4Yukon Southern Lakes 429 4.1 3.0 3.9 5.2Boreal Mountains and Plateaus 116 3.5 3.4 3.5 3.8Interior Highlands 119 7.2 5.8 7.3 8.3Interior Bottomlands 20 10.6 6.35 12 14Brooks Range 23 2.9 2.4 2.8 3.3Alaska Range 974 9.0 6.1 8.8 11Interior Forested Lowlands & Uplands 34 5.3 2.7 4.9 7.3

Dissolved nitrate plus nitrate concentration, as nitrogen, milligrams per liter

Yukon Stikine Highlands 299 0.09 0.04 0.08 0.13Yukon Southern Lakes 532 0.04 0.01 0.03 0.06Boreal Mountains and Plateaus 588 0.06 0.01 0.04 0.06Interior Highlands 21 0.19 0.1 0.16 0.26Interior Bottomlands 10 0.25 0.18 0.24 0.27Brooks Range -- -- -- -- --Alaska Range 139 0.18 0.1 0.17 0.2Interior Forested Lowlands & Uplands -- -- -- -- --

Total phosphorus concentration, as phosphorus, milligrams per liter

Yukon Stikine Highlands 114 0.01 0.002 0.003 0.008Yukon Southern Lakes 1063 0.05 0.008 0.02 0.10Boreal Mountains and Plateaus 572 0.13 0.006 0.008 0.014Interior Highlands 37 0.08 0.01 0.03 0.07Interior Bottomlands -- -- -- -- --Brooks Range -- -- -- -- --Alaska Range 102 0.23 0.02 0.08 0.3Interior Forested Lowlands & Uplands -- -- -- -- --

Ecoregion

(fig. 36)

No. of 

analyses Mean

Percentile values 

calculated from the data

25 50 75

Total organic carbon, as carbon, milligr

Yukon Stikine Highlands 145 1.4 Yukon Southern Lakes 180 1.3 Boreal Mountains and Plateaus 15 4.9 Interior Highlands 8 10.5 Interior Bottomlands -- -Brooks Range -- -Alaska Range 30 1.7 Interior Forested Lowlands & Uplands -- -

Dissolved organic carbon, as carbon, milli

Yukon Stikine Highlands -- -- Yukon Southern Lakes -- -- Boreal Mountains and Plateaus -- -- Interior Highlands 4 4.5 Interior Bottomlands -- -- Brooks Range -- -- Alaska Range 26 1.4 Interior Forested Lowlands & Uplands -- -- 

Total iron concentration, as iron, microg

Yukon Stikine Highlands 154 169 Yukon Southern Lakes 692 699 Boreal Mountains and Plateaus 151 136 Interior Highlands 16 225 Interior Bottomlands -- -Brooks Range 4 127 Alaska Range 71 6740 Interior Forested Lowlands & Uplands -- -

Ecoregion

(fig. 36)

No. of 

analyses Mean

Table 15. Summary statistics for selected properties and constituents of surface-water samples by ecoregion--Continued[--, no data]
Dissolved iron concentration, as iron, micrograms per liter

Yukon Stikine Highlands -- -- -- -- --Yukon Southern Lakes -- -- -- -- --Boreal Mountains and Plateaus -- -- -- -- --Interior Highlands 40 216 115 210 285Interior Bottomlands 10 62 10 10 50Brooks Range 5 18 0 10 30Alaska Range 119 73 10 30 72Interior Forested Lowlands & Uplands -- -- -- -- --

Total manganese, as manganese, micrograms per liter

Yukon Stikine Highlands 154 5 0.5 1.5 4.0Yukon Southern Lakes 692 31 10 18 34Boreal Mountains and Plateaus 151 7 2.2 5 10Interior Highlands 16 27.5 0 25 45Interior Bottomlands -- -- -- -- --Brooks Range -- -- -- -- --Alaska Range 71 171 20 60 220Interior Forested Lowlands & Uplands -- -- -- -- --

Total barium, as barium, micrograms per liter

Yukon Stikine Highlands 142 41 33 44 50Yukon Southern Lakes 691 43 22 35 56Boreal Mountains and Plateaus 48 25 18 29 30Interior Highlands -- -- -- -- --Interior Bottomlands -- -- -- -- --Brooks Range -- -- -- -- --Alaska Range 86 46 39 45 54Interior Forested Lowlands & Uplands -- -- -- -- --

Ecoregion

(fig. 36)

No. of 

analyses Mean

Percentile values 

calculated from the data

25 50 75

Total strontium, as strontium, microgra

Yukon Stikine Highlands 142 127 Yukon Southern Lakes 692 240 Boreal Mountains and Plateaus 48 62 Interior Highlands -- -Interior Bottomlands -- -Brooks Range -- -Alaska Range 85 216 Interior Forested Lowlands & Uplands -- -

Total arsenic, as arsenic, microgram

Yukon Stikine Highlands 99 0.8 Yukon Southern Lakes -- (<25 per

Boreal Mountains and Plateaus 148 0.5 Interior Highlands -- -- Interior Bottomlands -- -- Brooks Range -- -- Alaska Range 21 7.4 Interior Forested Lowlands & Uplands -- -- 

Total lithium, as lithium, microgram

Yukon Stikine Highlands 141 1.0 Yukon Southern Lakes 193 1.0 Boreal Mountains and Plateaus 151 0.8 Interior Highlands -- -- Interior Bottomlands -- -- Brooks Range -- -- Alaska Range -- -- Interior Forested Lowlands & Uplands -- -- 

Ecoregion

(fig. 36)

No. of 

analyses Mean

Table 15. Summary statistics for selected properties and constituents of surface-water samples by ecoregion--Continued[--, no data]
102 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

Data for three other trace elements, manganese, barium and

strontium, were also analyzed. Total manganese concentrationsvary widely throughout the basin but are generally highest in theAlaska Range ecoregion and lowest in the Yukon Stikine Highlands ecoregion. Barium and strontium were detected throughoutthe Yukon River Basin. Barium is relatively constant, but strontium varies widely (table 15). The highest concentrations and thegreatest variability of strontium concentrations are in the YukonSouthern Lakes ecoregion, whereas the lowest concentrations andleast variability of strontium were found in the Boreal Mountainsand Plateaus ecoregion. Anthropogenic Effects on Water Quality

Discussions of the water quality of the Yukon River Basin

are based on limited data and indicate that water chemistry differences throughout the basin are due more to natural factors than tohuman-induced factors. However, the basin has been affected byhuman activities, both from within the basin and from outside thebasin. The difficulty arises in determining to what degree humanshave affected the water quality, because a suitable water-qualitydata base does not exist at the present time.

The Yukon River Basin is not subject to the intense application of organic pollution found in some rivers of the lower 48

states. It is, however, more vulnerable to global atmospheric transport. Global transport of pollutants is well recognized. In thenorthern hemisphere, transport occurs primarily in the wintermonths when temperature and pressure gradients are the steepest.Pollutants from mid-latitudes are transported northward, wheregreater precipitation and colder temperature cause deposition froma "warm-cold distillation" effect (Majewski and Capel, 1995).Chlorinated pesticides, such as HCH, HCS, DDT, toxaphene, andchordanes, have been observed in the Arctic and are believed to

have been transported in the atmosphere. Mare lipophilic, concentrating in the fat and fgame animals.

In 1991, elevated levels of toxaphene, 

found in burbot liver, and lake trout and whLaberge near the headwaters of the Yukon Rhart, 1992). Analysis of archived fish tissue centrations similar to those of the 1concentrations in Lake Laberge whitefishigher than those in whitefish from other lakand Lockhart, 1992). Atmospheric transporthe source of the toxaphene and an exceptioserved to concentrate the pollutants in the prothers, 1995). 

Mining activity has, and continues to 

nomic industry in the Yukon River Basin. concern of mining is the possible harm to Although today’s mining practices are high

damage to fish habitat, many old abandonOne example is Coal Creek, located in YNational Preserve. This particular watershsively in the early 1900’s and the mining prahad a severe impact on the watershed. ThSuperfund site by the U.S. Environmental Pcleanup was completed in 1998.

During the Cold War, the military ha

Alaska. In addition to the military bases loand Delta Junction, early warning radar sitevillages along the Yukon River. At the UGalena, 250,000 drums containing potentiacurrently spread out across the tundra as a effect on water quality has yet to be determ
SUMMARY

This report describes the environmental and hydrologic setting of the Yukon River Basin, the fourth largest drainage basin in

North America. The primary environmental and hydrologic features of the Yukon River Basin are as follows:• The population of the Yukon River Basin is approximately

126,000 people. Approximately 10 percent of these peoplehave a subsistence lifestyle and depend on the fish and gameresources of this 330,000-square-mile basin.

• The climate of the Yukon River Basin is variable because of its

large size and range in altitude. Precipitation ranges from 10 to130 in. annually and the mean average air temperature is about22 °F. The upstream part of the basin is rolling topography ormoderately high rugged mountains, whereas the downstreampart of the basin is primarily low mountains, plains, and lowlands. The geology is complex and consists of many types ofconsolidated rocks in the mountain ranges surrounding thebasin and unconsolidated sediments deposited in the lowlandareas.

• Wetlands account for about 30 percent of the Yukon River

Basin. The primary land cover is needleleaf forest and the primary soils are Gelisols. Many of the Gelisols are frozenorganic soil. These soils are located in the northern third of thebasin which is underlain by continuous permafrost.

• The Yukon River Basin consists of 20 ecoregions, distinct areas

delineated by the integration of their natural features. InteriorForested Lowlands and Uplands is the largest ecoregion of thebasin and accounts for 21 percent of the drainage area. TheInterior Highlands ecoregion is the second largest ecoregion ofthe basin and accounts for about 17 percent of the drainagearea.

• Discharge from streams and rivers in th

varies depending on the presence of glactaries that drain glacier areas of the YukRiver and the White River, account for of the Yukon River but only account fothe drainage area. Melting glaciers add rivers and sustain runoff through the average annual discharge of the Yukon R227,000 ft3/s. However, most of the fl

through September.

• Near its mouth, the Yukon River transp

tons of suspended sediment toward the However, each year, about 20 million deposited on flood plains and in braideImplications of this deposition are enormtion of organic carbon, contaminants, anare absorbed onto, or otherwise associatments.

• The waters of the main stem of the Yukon 

ies are predominantly calcium magnesiuwith specific conductance ranging froConcentrations of the nutrients nitrogegenerally less than 0.5 mg/L. Temporal between summer and winter are evident Yukon River. Comparison of water-quagions indicates that total organic carbohighest in ecoregions dominated by orga

• Some anthropogenic effects to water qual

Basin have been documented. These efspheric processes, pre-regulation miningused during the Cold War. The cumuYukon River Basin cannot be made becaquality data.
104 Environmental and Hydrologic Overview of the Yukon River Basin, Alaska and Canada

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