Influence of Stream Characteristics

and Grazing Intensity on Stream

Temperatures in Eastern Oregon

United States

Department of

Agriculture

Forest Service

Pacific Northwest

Research Station

General Technical

Report

PNW-GTR-459

April 1999

S.B. Maloney, A.R. Tiedemann, D.A. Higgins,

T.M. Quigley, and D.B. Marx
Authors S.B. MALONEY is director of operations, Cascade Earth Sciences, P.O. Box 2379,

Pocatello, ID 83206-2379; A.R. TIEDEMANN is scientist emeritus and T.M. QUIGLEY

is a range economist, U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, 1401 Gekeler Lane, La Grande, OR 97850; D.A. HIGGINS is a

hydrologist, Chequamegon National Forest, 157 N. 5th Ave., Park Falls, WI 54552; and

D.B. MARX is professor, Department of Biometry, University of Nebraska, 103 Miller

Hall, Lincoln, NE 68583-0712.
Abstract Maloney, S.B.; Tiedemann, A.R.; Higgins, D.A.; Quigley, T.M.; Marx, D.B. 1999.

Influence of stream characteristics and grazing intensity on stream temperatures in

eastern Oregon. Gen. Tech. Rep. PNW-GTR-459. Portland, OR: U.S. Department

of Agriculture, Forest Service, Pacific Northwest Research Station. 19 p.

Stream temperatures were measured during summer months, 1978 to 1984, at 12

forested watersheds near John Day, Oregon, to determine temperature characteristics

and assess effects of three range management strategies of increasing intensity.

Maximum temperatures in streams of the 12 watersheds ranged from 12.5 to 27.8 oC.

Maximum stream temperatures on four watersheds exceeded 24 oC, the recommended

short-term maximum for rainbow trout (Oncorhynchus mykiss) and chinook salmon (O.

tshawytscha). Streams with greater than 75 percent stream shade maintained acceptable stream temperatures for rainbow trout and chinook salmon. Lowest temperatures

were observed in streams from ungrazed watersheds. Although highest temperatures

were observed in the most intensively managed watersheds (2.8 hectares per animal

unit month), the effect of range management strategy was not definitive. It was confounded by watershed characteristics and about 100 years of grazing use prior to

initiation of this study.

Keywords: Forested watersheds, grazing management strategies, grazing intensity,

fisheries, fish habitat, chinook salmon, steelhead trout, cutthroat trout, Dolly Varden

trout.

Summary Stream temperatures were measured during the summer months from 1978 to 1984

on 12 forested watersheds near John Day, Oregon, to determine the temperature

characteristics of streams in the watersheds and to assess the effects of three range

management strategies. Maximum temperatures in streams of the 12 watersheds

ranged from 12.5 to 27.8 oC. Daily ranges within the streams were as great as 12.8 oC.

Maximum mean weekly temperatures ranged from 10.9 to 17.8 oC. On four of the

watersheds, maximum stream temperatures exceeded 24 oC, the recommended

short-term maximum for rainbow trout (Oncorhynchus mykiss) and chinook salmon

(O. tshawytscha). Percentage of stream shade, week of the year, weekly flow, stream

width, year, travel time, elevation, and aspect explained 67 percent of the variation in

stream temperatures. Streams with greater than 75 percent stream shade maintained

acceptable stream temperatures for rainbow trout and chinook salmon. Streams from

watersheds with range management strategy A (no grazing) had significantly lower

(p < 0.05) maximum temperatures than those from strategy D watersheds (intensively

managed at 2.8 hectares per animal unit month). Temperatures of streams managed at

strategy C (7.7 hectares per animal unit month) were intermediate and not significantly

different from those of either strategy A or D. The effect of range management strategy

in this study was not definitive, however, because it was confounded by watershed

characteristics and about 100 years of grazing use prior to initiation of this study.

The dominant vegetative habitat (ecosystem) on a watershed significantly influenced

stream temperatures. Temperatures were lower with the larch/Douglas-fir (Larix

occidentalis Nutt./Pseudotsuga menziesii (Mirbel) Franco) and fir/spruce (Abies

lasiocarpa (Hook.) Nutt./Picea engelmannii Parry ex Engelm.) ecosystems than with

ponderosa pine (Pinus ponderosa Dougl. ex. Laws.) and mountain meadow ecosystems. Stream temperatures for lodgepole pine (Pinus contorta Dougl. ex Loud.) were

intermediate. A strong first-order autocorrelation was found for stream temperature

measurements within all watersheds. This indicated that the stream temperature of

one time period was significantly related to the temperature of the previous period.

Data were analyzed to account for autocorrelation.
Contents 1 Introduction

2 Location and Characteristics of Watersheds

4 Methods

4 Stream Temperature

4 Determination of Stream Characteristics

4 Intensive Analysis of Temperature Change Along One Stream

5 Data Analysis

5 Results and Discussion

5 Stream Temperature Characteristics

8 Relations of Stream Temperature to Stream Characteristics

11 Stream Temperature Along the Profile of Caribou Creek

13 Effect of Range Management Strategy on Stream Temperatures

14 Comparisons of Maximum Stream Temperatures

and Established Fish Tolerances

15 Conclusions

15 Literature Cited
1

Introduction The headwaters of the John Day River provide spawning and rearing habitat for one

of the few remaining wild runs of chinook salmon (Oncorhyncus tshawytscha) and

steelhead (O. mykiss) in the Columbia River basin (State of Oregon 1986a). These

streams also support resident populations of rainbow trout (O. mykiss), cutthroat trout

(Salmo clarki), and Dolly Varden char (Salvelinus malma). Stream temperature plays

an important role in determining the survival, distribution, and productivity of these

species because salmonids have a low thermal tolerance (Bjornn 1971). Rainbow

trout prefer temperatures between 14 and 18 oC and have an upper lethal temperature

tolerance of about 27 oC (Ames 1977, Bowers and others 1979, Cherry and others

1977, Gariside and Tait 1958). Chinook salmon fry prefer temperatures between 12

and 14 oC and have an upper lethal temperature tolerance of 25 oC (Bjornn 1971).

As stream temperatures increase above the optimum for salmonids, warm water

species compete more effectively with salmonids for available space.

Water quality criteria established to protect aquatic life include two upper limiting

temperatures: a short-term maximum for survival, and a maximum weekly mean for

growth. For both adult and juvenile rainbow trout (including steelhead trout), the shortterm maximum is 24 o

C; the maximum mean weekly is 19 oC (U.S. Environmental

Protection Agency 1986). For embryo rainbow trout during the spawning season,

short-term maximum and maximum mean weekly stream temperatures are 13 and

9 oC, respectively. Oregon State water quality standards (State of Oregon 1986b)

reflect these criteria and the needs of salmonids by establishing permissible limits on

water temperature increases. These criteria indicate that when stream temperature is

20 oC, activities influencing stream temperature will be regulated such that no further

temperature increases occur. In our study, we used hourly maxima and weekly mean

maximum stream temperatures so that comparisons could be made to Oregon State

standards. We also used 20 oC as the threshold for comparison.

Shade provided by riparian vegetation is one of the most important regulators of

temperature in small streams where solar radiation is the predominant energy source.

When riparian vegetation is removed by harvest, grazing, road construction, and

mining, the stream surface is exposed to direct solar radiation, and stream temperatures increase (Gibbons and Salo 1973, Levno and Rothacher 1969, Rishel and others

1982, Swift and Messer 1971). Complete harvest of riparian vegetation increased the

mean monthly maximum temperature as much as 7.8 oC in one Pacific Northwest

stream (Brown 1970). Levno and Rothacher (1969) showed that removal of stream

shade by tree harvesting and slash burning of residues caused an increase of 7.8 o

C

in average maximum stream temperature; however, when buffer strips of riparian

vegetation 15 to 30 meters wide were left adjacent to streams, temperatures did

not increase (Brown 1970).

Elimination of streamside vegetation and removal of overhanging streambanks are

two of the leading causes for decline of native trout in Western streams (Behnke

and Zarn 1976). Domestic livestock such as cattle are one of the major causes of this

problem because they tend to concentrate in riparian zones for the high-quality forage

and readily available water (Bryant 1982, Roath and Krueger 1982). They consume

grasses, forbs, and new growth from many shrubs and small trees (Ames 1977).

Severe alteration of composition, structure, and productivity of vegetation in riparian

zones has been a common result (Kauffman and Krueger 1984). Protracted heavy

grazing use can eventually eliminate shrubs and small trees. Cattle may crush overhanging streambanks and physically disturb the streambed, causing increases in
2

sediment, turbidity, and water temperature (Clary and Webster 1989). Protection of

streams from livestock grazing has resulted in improvement in abundance of riparian

vegetation, stream surface shade, and channel morphology (Platts 1981, Winegar

1977). Improvements in vegetation and stream channel morphology have generally

taken 10 or more years after exclusion of cattle. In some areas, however, past grazing

use has caused sufficient damage that recovery may be a long-term process—even

with reduced grazing (Clary et al. 1996). Although numerous studies have related

grazing to water quality and watershed condition (Blackburn 1984; Gaither and

Buckhouse 1981; Gifford and Hawkins 1978; Meehan and Platts 1978; Moore and

others 1979; Tiedemann and Higgins 1989; Tiedemann and others 1988, 1989),

studies relating grazing systems to water temperature are lacking (Gaither and

Buckhouse 1981, Gifford and Hawkins 1978).

The Oregon Range Evaluation Project (EVAL) was established in 1976 to implement

present understanding of range management techniques and evaluate their effects

on range and associated resources (Quigley and others 1989, Sanderson and others

1988). Water quality was one of the major associated resources studied (Tiedemann

and Higgins 1989).

As part of this project, 12 small watersheds, ranging from 1.2 to 18.1 square kilometers, were established and implemented with three range management strategies; they

provided an opportunity to examine the effects of increasing intensity of management

on stream temperature.

Specific objectives of stream temperature studies on these watersheds were to establish summer stream temperature characteristics for the 12 study watersheds; determine relations among stream characteristics (including the dominant ecosystem) and

summer stream temperatures; determine the influence of increasing intensity of range

management strategy on summertime stream temperature characteristics; characterize changes in stream temperatures along the profile of one stream as shade and

other characteristics change; and compare stream temperatures with criteria established for tolerances of rainbow trout and chinook salmon.

The studies described here were carried out near John Day in Grant County, Oregon.

The EVAL project area encompassed about 140 000 hectares on 19 Forest Service

grazing allotments and 21 private ranches. The 12 study watersheds were in the

northern part of the Malheur National Forest within EVAL grazing allotments. In most

cases, the study watersheds were part of a larger, fenced pasture within a defined

range management strategy. Cattle control was therefore not specific to the riparian

area or watershed, but to a much larger area.

Range management strategies of increasing intensity applied to the 12 watersheds

were:

A. Control—no grazing.

C. Management of grazing to attain uniform livestock distribution throughout a pasture

by using fencing and water developments. Stocking rate averaged 7.7 hectares per

animal unit month for this strategy.

D. Management of grazing to emphasize livestock production with multiple use considerations. Management included practices such as fencing, watering, and salting to

attain uniform livestock distribution. Practices to improve forage production included

Location and

Characteristics

of Watersheds
3

seeding, fertilization, shrub and tree removal, and forest thinning. Stocking rate

was 2.8 hectares per animal unit month for this strategy.

More than one grazing system (i.e., deferred rotation, rest rotation, no use, and season-long use) was used to achieve a given strategy. Strategy A was implemented on

four watersheds; strategy C on five watersheds; and strategy D on three watersheds

(table 1).

Table 1—Range management strategy and characteristics of study watersheds of the Oregon Range

Evaluation Project near John Day, Oregon, 1978-84

Range Stream

management Drainage Drainage 7-day

Watershed strategy Ecosystema area Elevation Aspect Shade Width Travel density low-flow

Km2 Meters Degrees Percent Meters Hours Km•km-2 L•sec-1

•km-2

Big A F/S 5.2 1903 340 67.8 0.82 14.7 2.8 1.54

Blackeye A LA/DF 2.3 1768 265 87.0 .67 3.2 1.5 1.36b

Caribou C PP 6.3 1440 195 54.7 .49 17.1 3.0 .17

East Donaldson C LA/DF 4.1 1403 335 89.7 .55 5.9 2.9 .93

East Little Butte C LA/DF 3.0 1415 360 83.1 .94 6.8 2.4 1.53b

Flood Meadow D LP/MM 18.1 1615 360 35.0 1.00 14.7 3.1 .67

Keeney Meadow D MM/PP 12.7 1655 360 6.1 .52 4.4 2.6 .08

Lake A LA/DF 1.2 1585 155 75.9 .27 3.3 1.4 .33

Little Boulder C LA/DF 6.0 1648 200 79.2 .73 12.5 2.2 1.42

Ragged A LA/DF 8.8 1425 25 87.8 .67 24.4 2.6 .75

Tinker Dc LA/DF 4.4 1615 155 64.0 .52 15.5 4.4 .50

West Donaldson C LA/DF 3.9 1390 360 87.5 .40 12.5 2.7 1.03

a F/S = fir/spruce; LA = larch; MM = mountain meadow; PP = ponderosa pine; LP = lodgepole pine; DF = Douglas-fir.

b Estimated values.

c Strategy D at Tinker was attained in water year 1981; all other strategies were attained in water year 1979.

Because strategies were assigned to watersheds as a consequence of their inclusion

in larger treatment areas, the experimental design was not random. Also, strategy

D watersheds were in areas that were selected for their potential for implementing

practices resulting in sufficient forage production to support grazing at stocking

rates of 2.8 hectares per animal unit month.

A detailed description of the watersheds and hydrologic characteristics is provided by

Higgins and others (1989) and Tiedemann and Higgins (1989). Predominant ecosystems

(vegetative habitats) as described by Garrison and others (1977) were mountain meadow,

western larch/Douglas-fir (Larix occidentalis Nutt./Pseudotsuga menziesii (Mirbel)

Franco), subalpine fir/Engelmann spruce (Abies lasiocarpa (Hook.) Nutt./Picea engelmannii Parry ex Engelm.), ponderosa pine (Pinus ponderosa Dougl. ex. Laws.), and

lodgepole pine (Pinus contorta Dougl. ex Loud.). Each watershed is characterized in

table 1 by the predominant vegetative habitat or ecosystem. Data from Austin, Oregon

(1280 meters elevation), indicates that the study area receives 51 to 127 centimeters

of precipitation, with about 70 percent occurring as snow between November and April

(National Oceanographic and Atmospheric Administration 1984). The mean monthly air
4

temperature at Austin is -6.7 oC in January and 16.7 oC in July, with annual extremes

of -26 to 38 oC common. Summer relative humidities range from 15 to 30 percent

during the daytime. Summer cloud cover averages 3 to 6 percent. The annual hydrograph is dominated by snowmelt runoff that begins at low-elevation watersheds in

March and at high-elevation watersheds in mid-May. Peak discharge ranges from 5.7

to 634 liters per second per square kilometer and occurs from mid-April to early June,

depending on elevation and aspect of the watershed. Flows diminish through the summer with the lowest in August and September. Runoff patterns are similar to those

reported for other watersheds in eastern Oregon and Washington (Fowler and others

1979, Helvey and others 1976).

Methods Stream temperatures were continuously recorded at the mouth of each watershed

during the summers of 1978 through 1984 by using Ryan model “J” and “G” (Ryan

Instruments, Inc., Kirkland, Washington)1 thermographs. Recorders were placed near

the center of the pool behind control structures (weirs) used for measurement of water

yield. Accuracy was + 2 percent for temperature and timing. Charts were digitized

and reduced to 1-hour values. Only complete days from June 21 to September 19

were used in the analysis. All analyses were based on the hourly datum point. Daily

analysis was based on the mean of 24 hourly values. Weekly analysis was based on

the mean of 7 daily means, starting the first week on June 21.

Streams of each watershed were divided into reaches for purposes of determining

stream characteristics. Reaches ranged from 75 to 2590 meters long. Reach length

was determined by uniformity of the measured characteristics, percentage of shade,

azimuth (aspect), and gradient. All stream characteristics were measured at the start

of the study. Stream shade was measured at several systematically spaced points

within each reach by using a Solar Pathfinder. It was used to determine the percentage

of potential solar radiation reaching the measurement point in mid-August. The number

of sample points differed among reaches, depending on the variation in stream shade,

and were selected to produce an estimated mean within 5 percent of the true mean at

the 80-percent confidence level. The mean stream shade for each reach was determined from a simple arithmetic average; means for entire streams were weighted by

reach lengths. Stream widths also were measured at the shade measurement points

and means determined by the same procedure.

Stream gradients and aspects were measured from 7.5-minute topographic maps.

Streamflow travel times were estimated by using tracer dye over short sections of

some reaches during the low-flow period in August 1983. Reach lengths were determined by pacing in the field and verified on topographic maps.

To determine the relations among stream temperature and characteristics of individual

stream reaches, an intensive analysis was conducted for six reaches of Caribou Creek

from July 10 through September 13, 1984. Thermographs were placed at the end of

each of six stream reaches on Caribou Creek. These reaches encompassed all but the

uppermost kilometer of the perennial stream and were the same reaches defined for

analysis of stream characteristics that were used in the broader part of the watershed

study. Analysis of stream temperature was based on daily maximum values. Shade

cover, reach length, aspect, gradient (slope), and elevation were the same values used

in the general watershed study described above. The day with the highest maximum

(July 26, 1984) was used for discussion purposes. Multiple regression analysis with all

Determination

of Stream

Characteristics

Intensive Analysis

of Temperature

Change Along

One Stream

Stream Temperature

1 The use of trade or firm names in this publication is for reader information

and does not imply endorsement by the U.S. Department of Agriculture of

any product or service.
5

observations was used to determine the amount of variation in stream temperature

that was accounted for by stream characteristics, air temperature, and cloud cover.

Estimates of air temperature and cloud cover were determined from air temperature

data from Long Creek, Oregon, and cloud cover data from Meacham, Oregon, by

using procedures of Satterlund (1981).

Data Analysis Cumulative frequency-distribution curves for the percentage of time a stream temperature was exceeded were developed for the period of record for each watershed. To

compensate for missing data, the study period was arbitrarily divided into critical and

noncritical periods selected by examining temperature plots for a 6-week period when

most watersheds reached yearly maxima (table 2). The critical period was July 10 to

August 21, and the noncritical period included June 21 to July 9 and August 22 to

September 19. The percentage of time a temperature was exceeded (actual hours

exceeded divided by hours observed) was weighted by the proportion of possible

hours within the study period that occurred in each period (46.2 percent in critical and

53.8 percent in noncritical). Values for critical and noncritical periods were then added

to form data points for that temperature. This procedure was repeated for each year

and temperature. The annual weighted values were averaged to produce a cumulative

frequency distribution curve for the period of record.

Statistical analyses were performed by using the general linear model procedure of the

Statistical Analysis System (1985). Autocorrelation of weekly means within years and

watersheds was tested by following the procedure of Abraham and Ledolter (1983) for

small sample size. All analyses were conducted after adjustment for observed autocorrelation. Stepwise and multiple regression and correlation procedures were used to

determine significant (p < 0.05) differences among relations of stream temperatures

and stream characteristics. Analysis of variance models, with and without shade as a

covariate, were used to test the significance of range management strategy on mean

weekly stream temperature and the amount of time stream temperature exceeded 20 o

C.

Analysis of variance also was used to test for significance of ecosystem (dominant

vegetative habitat) on mean weekly stream temperature. Flood Creek watershed was

not included in the analysis of time that temperature exceeded 20 oC because of

insufficient data.

Maximum temperatures in streams of the 12 watersheds ranged from 12.5 to 27.8 oC

(table 3). Minimum temperatures (not shown in table) ranged from 3.5 to 5.0 oC and

were similar on all watersheds. Daily ranges (not shown in table) within the streams

were as great as 12.8 o

C. Maximum mean weekly temperatures ranged from 10.9 to

17.8 oC (table 3). Dates of maximum temperatures differed from year to year, but more

than 88 percent of the maximum temperatures were observed during weeks 29 to 33

(July 16 to August 19) (fig. 1).

Autocorrelation analysis showed a strong first-order correlation over time, which was

approximately constant among watersheds (table 4). Significant autocorrelation indicates that the stream temperature of one time period was significantly related to the

temperature of a previous period. Average autocorrelations differed more from year to

year but were relatively strong in all years. The overall average autocorrelation for all

watershed-year combinations was 0.36. The relatively small sample size may explain

some of the large variability in autocorrelation among watersheds and years. Results

suggest that an uncorrelated error model would not be appropriate and that the true

variance of the weekly temperature analyses may have been underestimated by less

than 10 percent.

Results and

Discussion

Stream Temperature

Characteristics
6

Table 2—Percentage of hours of stream temperature data present in the critical

(C) and noncritical (NC) periods of study watersheds of the Oregon Range

Evaluation Project near John Day, Oregon, 1978-84a

 Year

Watershed Period 1978 1979 1980 1981 1982 1983 1984

--------------------------------------Percent--------------------------------------

Big NC 48 9 16 33 33 ID 31

C 41 22 34 19 40 ID 33

Blackeye NC ID 54 23 35 54 ID ID

C ID 32 46 46 46 ID ID

Caribou NC ID 47 49 52 45 ID 53

C ID 23 46 46 37 ID 46

East Donaldson NC ID 33 ID 26 45 54 38

C ID 45 ID 45 46 46 46

East Little Butte NC ID ID 47 45 51 54 ID

C ID ID 46 46 46 43 ID

Flood NC ID ID ID ID ID 33 53

C ID ID ID ID ID 11 46

Keeney NC ID 51 53 33 45 ID 50

C ID 27 46 31 46 ID 24

Lake NC 52 33 53 33 20 54 10

C 42 20 46 30 46 46 44

Little Boulder NC 36 41 37 54 4 33 13

C 37 23 46 46 23 34 24

Ragged NC ID 54 49 45 32 ID 53

C ID 33 46 46 26 ID 46

Tinker NC ID 41 35 46 16 ID 40

C ID 46 12 46 46 ID 37

West Donaldson NC ID 24 53 ID 54 42 53

C ID 46 46 ID 46 13 46

ID = insufficient data (total hours < 650 or critical hours < 240).

a Total possible hours in the noncritical period = 1176 hours (54 percent); total possible hours in the critical

period = 1008 hours (46 percent); and total possible hours in the study period = 2184 hours.
7

Table 3—Stream temperature characteristics for study watersheds of the Oregon

Range Evaluation Project near John Day, Oregon 1978-84

 Maximum mean

Watershed Maximum hourly weekly Rangea Meanb

 o

C

Big 15.7 12.6 7.9 9.0

Blackeye 12.5 10.9 5.5 7.8

Caribou 26.1 17.8 10.5 14.0

East Donaldson 15.2 13.2 5.5 10.3

East Little Butte 18.1 14.1 6.9 10.7

Flood 24.0 16.6 6.6 13.5

Keeney 27.8 17.7 9.1 14.1

Lake 16.6 11.9 6.2 9.2

Little Boulder 18.0 14.2 7.9 10.3

Ragged 19.1 14.4 7.6 11.1

Tinker 25.8 16.8 8.3 13.0

West Donaldson 15.8 13.5 5.9 10.1

a Range = maximum mean weekly - minimum mean weekly.

b Mean = mean of the mean weekly.

Figure 1–Timing of yearly maximum stream temperatures.

26 27 28 29 30 31 32 33 34

20

15

10

5

0

Yearly maximums observed (no.)

Week number
8

Table 4—First-order autocorrelations and sample sizes for study watersheds of

the Oregon Range Evaluation Project near John Day, Oregon, 1978-84

 Year

Watershed 1978 1979 1980 1981 1982 1983 1984 Average

Big 0.602 ID -0.172 -0.076 0.325 ID 0.321 0.274

11 6 6 9 7

Blackeye ID 0.588 0.054 0.561 0.607 ID ID 0.487

10 8 10 13

Caribou ID 0.292 0.236 0.514 0.498 ID 0.454 0.402

8 12 12 9 12

East Donaldson ID 0.111 ID -0.001 0.298 0.712 0.313 0.333

10 7 11 13 10

East Little Butte ID ID -0.563 0.270 0.596 0.711 ID 0.385

6 11 12 12

Flood ID ID ID ID ID ID 0.639 0.639

12

Keeney ID 0.431 0.310 0.115 0.452 ID -0.025 0.271

9 10 8 11 9

Lake ID -0.253 -0.027 0.206 0.336 0.724 -0.332 0.204

6 10 8 7 13 6

Little Boulder -0.154 0.379 0.277 0.525 ID 0.259 ID 0.290

8 8 10 13 8

Ragged ID 0.638 0.518 0.451 -0.024 ID 0.623 0.499

11 12 11 6 13

Tinker ID 0.525 -0.238 0.394 0.172 ID 0.427 0.319

11 6 11 7 9

West Donaldson ID 0.036 0.432 ID 0.591 0.308 0.596 0.431

9 13 13 7 13

Average 0.291 0.344 0.169 0.345 0.431 0.598 0.405 0.363

ID = insufficient data (sample size < 5).

Maximum and mean weekly stream temperatures were regressed against stream

characteristics to help explain stream temperature variation. Our best model from

stepwise regression analysis explained 67 percent of the variation in stream temperatures and contained eight factors in declining order of F-value (shade, week, weekly

flow, width, year, travel time, elevation, and aspect). These variables were significant at

p < 0.001, except for aspect at p < 0.03. Our results were similar to those of Schloss

(1985). Schloss’s critical variables were shade, elevation, and channel length (related

to our variable of travel time).

Relations of Stream

Temperature to Stream

Characteristics
9

Visual examination of cumulative frequency distribution curves of the percentage of

time a temperature was exceeded for individual watersheds revealed that there were

three potential groups. We conducted a cluster analysis to determine if there was a

statistical basis for grouping watersheds. Based on maximum hourly temperatures,

three significantly different (p < 0.05) temperature ranges emerged from this analysis

(fig. 2, table 5). Characteristics of individual watersheds explained some of the variability in stream temperatures within strategies. Group 1 watersheds had the lowest

temperatures, the highest mean percentage of shade, the highest 7-day low flow, the

highest mean elevation, and the shortest mean travel time. Within group 1, Big Creek

watershed had the lowest percentage of shade and the longest travel time; however,

it maintained low stream temperatures because of low air temperatures common at

higher elevations and because about 85 percent of the flow originates in the lower two

reaches where stream shade averages 80 percent. All group 1 watersheds were within

range management strategies A and C. Group 3 watersheds, all in C and D strategies,

had the highest temperatures, the lowest mean percentage of shade, the lowest 7-day

low flow, and the longest mean travel time. Short travel time of Keeney Creek was

more than compensated by a small amount of shade (6.1 percent). Flood Creek had

both relatively long travel time and a small amount of stream shade that resulted in

high temperatures. Caribou and Tinker Creeks had relatively long travel times with

low to moderate amounts of shade. The maximum stream temperatures observed in

group 3 were more than twice as great as the maxima observed by Helvey and others

(1976) and Fowler and others (1979). Group 2 watersheds (A and C range management strategies) were intermediate in temperature response and characteristics to

those of groups 1 and 3.

Figure 2–Cumulative frequency-distribution curves for stream temperature groups.

Group 1

Time exceeded (percent)

0 20 40 60 80 100

30

25

20

15

10

5

0

Temperature (oC)

Group 2 Group 3
10

Table 5—Stream temperature groups of study watersheds of the Oregon Range

Evaluation Project near John Day, Oregon, 1978-84

Mean

Maximum

temperature Travel 7-day low

Groupa range Strategy Elevation time Shade flow

oC Meters Hours Percent L•sec-1

•km-2

1 12.5-15.8 A/C 1616 9.1 83.0 1.22

2 16.6-19.1 A/C 1518 11.8 81.5 1.01

3 24.0-27.8 D/C 1581 12.9 40.0 0.36

a Group 1 contains Big, Blackeye, East and West Donaldson; group 2 contains East Little Butte,

Lake, Little Boulder, and Ragged; and group 3 contains Caribou, Flood, Keeney, and Tinker.

Slopes of cumulative frequency curves were greatest in group 3 and least in group 1

(fig. 2). The steepest slopes are associated with the highest temperatures of group 3,

and the flattest slopes with the lowest temperatures of group 1. The steep slopes of

group 3 indicated responsiveness to sunlight. Group 1 streams, with more protective

shade, were less responsive to sunlight. The higher temperature ranges for each group

were the primary element separating groups from one another, because ranges for

lower temperatures were similar in all three groups.

The dominant ecosystem on a watershed (table 1) had a significant effect (p < 0.05)

on mean weekly stream temperatures (fig. 3). Mean weekly stream temperatures

were significantly greater (p < 0.05) for mountain meadow and ponderosa pine than for

larch/Douglas-fir and fir/spruce ecosystems, but there were no significant differences

between larch/Douglas-fir and fir/spruce or mountain meadow and ponderosa pine.

Stream temperatures for the lodgepole pine ecosystem were not significantly different

from streams of the other ecosystems. Differences among ecosystems can be explained by differences in amount of overstory shade and elevation. Overstory shade

was greatest for larch/Douglas-fir and fir/spruce ecosystems and least for mountain

meadow. Mountain meadow and ponderosa pine were at low elevations; larch/Douglasfir and fir/spruce were at higher elevations.
11

Figure 3–Mean weekly stream temperatures among ecosystems. Ecosystems with the same lower

case letter are not significantly different (p < 0.05). F/S = fir/spruce; LA/DF = western larch/Douglasfir; LP = lodgepole pine; PP = ponderosa pine; MM = mountain meadow.

Stream temperature varied with time of day along all six stream reaches of Caribou

Creek (fig. 4). The maximum daily stream temperature on most reaches occurred at

1300 hours. Reach 6, at the origin of the stream, had the greatest amount of stream

shade (73 percent) and the lowest maximum stream temperatures (16 oC) (table 6).

In reach 5, the next reach downstream, shade decreased to 62 percent and the

maximum temperature increased to 19 oC. Daily maximum stream temperatures

continued to increase downstream as stream shade decreased and exposure of

stream to sun-light increased. There was a slight reduction of maximum stream

temperature (1.5 oC) with increased stream shade (26 to 64 percent) between

reaches 3 and 1.

In a multiple regression analysis, 88 percent of the variation in temperature from reach

to reach could be accounted for by slope, air temperature, length of reach, cloud cover,

shade, elevation, and aspect. Partial r2 values for each factor are shown in table 7.

Slope and air temperature accounted for about 82 percent of the variation in stream

temperatures. A second-order polynomial model explained 85 percent of the variation

along a stream with watershed, climatic, and time variables. Input variables were the

same as those for the long-term watershed study with the addition of climatic variables

(cloud cover, air temperature, and precipitation).

Stream Temperature

Along the Profile

of Caribou Creek

F/S LA/DF LP PP MM

Ecosystem

16

14

12

10

8

6

4

2

Mean weekly stream temperature

 (

0

oC)

a

a

a b b b
12

Figure 4–Stream temperatures along six reaches of Caribou Creek during the day with the highest maximum

(July 26, 1984).

Table 6—Stream reach characteristics of Caribou Creek watershed of the Oregon

Range Evaluation Project near John Day, Oregon, September 1984

 Maximum

Stream reach Shade Length Aspect Gradient temperature

 Percent Meters Degrees Percent o

C

Reach 1 64 400 196 5.4 26.5

Reach 2 35 245 186 4.0 27.0

Reach 3 26 610 224 4.4 28.0

Reach 4 44 1220 197 5.0 26.0

Reach 5 62 580 221 7.1 19.0

Reach 6 73 1465 175 10.6 16.0

Reach 3

Reach 2

Reach 1

Reach 4

Reach 5

Reach 6

0 2 4 6 8 10 12 14 16 18 20 22 24

Hours

29

27

25

23

21

19

17

15

13

11

Temperature (oC)
13

Table 7—Partial r2, cumulative r2, and significance of F-test for relations of

stream reach characteristics and stream temperatures for Caribou Creek watershed of the Oregon Range Evaluation Project near John Day, Oregon, July 10

through September 13, 1984

Variable Partial r2 Cumulative r2 Probability > F

Slope 0.606 0.606 0.0001

Air temperature .213 .819 .0001

Reach length .022 .841 .0001

Cloud cover .018 .859 .0001

Shade .006 .865 .0001

Elevation .014 .879 .0001

Aspect .003 .882 .0009

Maximum hourly and mean weekly temperatures were significantly different (p < 0.05)

among range management strategies (fig. 5). Maximum hourly temperatures and mean

weekly temperatures for streams from strategy D watersheds were significantly greater

than for those from strategy A watersheds; streams from strategy C watersheds were

intermediate and not statistically different from either strategy A or D. Analysis for effect

of the EVAL range management strategy was confounded by watershed characteristics

and pre-EVAL management strategies. The temperature difference was attributable to

differences in stream shade; when shade was used as a covariate, range management

strategy was not significant. Streams from the three strategy D watersheds have open

meadows with little tree or shrub cover. Caribou Creek, strategy C, also has an open

stream channel and stringer meadows that are associated with high stream temperatures. These meadow areas are highly susceptible to temperature increases from grazing

because once streambank vegetation (herbaceous, shrubby, and tree) is removed and

stream banks are rounded, there is nothing to shade the stream. This problem is aggravated by the long travel time for water through the meadows. Nearly 100 years of grazing

use and logging activities likely had a strong influence on stream temperatures of these

watersheds through removal of streamside shrubby vegetation and caving of overhanging

stream banks. Streams from strategy A watersheds, in contrast, were more heavily

forested and had probably received less previous grazing use. Except for Caribou Creek,

strategy C watersheds are more forested than strategy D watersheds and likely have had

less previous gazing use.

Effect of Range

Management

Strategy

on Stream

Temperatures
14

Figure 5–Maximum hourly and mean weekly stream temperatures among range management

strategies. Strategies with the same lower case letter are not significantly different (p < 0.05)

for maximum hourly temperature. Strategies with the same upper case letter are not significantly

different (p < 0.05) for mean weekly stream temperature. Strategy A = no grazing; strategy C =

7.7 hectares per animal unit month; strategy D = 2.8 hectares per animal unit month.

Range management strategy did not have a significant effect on the percentage of

time the temperature was above 20 oC. Keeney Creek was above 20 oC the greatest

amount of time, about 17 percent (fig. 2). Keeney Creek also had the least streamside

shade and has a northern aspect that restricts shading from the streambanks. Again,

the strong influence of watershed characteristics likely masked the effect of range

management strategy.

Maximum hourly stream temperatures on Keeney, Flood, Tinker, and Caribou Creeks

all exceeded the short-term (maximum hourly) standard for rainbow trout of 24 oC

(U.S. Environmental Protection Agency 1986) because shade cover was limited on

these streams. Streams of these watersheds had the lowest percentage of shade,

ranging from 6.1 to 64.0 percent. The principal source of heat for small forest streams

is solar energy striking the stream surface (Brown 1983). A minimum of 75 percent of

the stream surface must be shaded from 1100 to 1600 hours from June to September

to control maximum stream temperatures (Brown 1969). All watersheds with greater

than 75 percent effective stream shade had maximum hourly stream temperatures

within acceptable limits. Big Creek had less than 75 percent effective stream shade

but its high elevation and the contributing flows from shaded reaches resulted in

acceptable stream temperatures.

Comparisons of

Maximum Stream

Temperatures and

Established Fish

Tolerances

Strategy A Strategy C Strategy D

Maximum hourly Mean weekly

30

25

20

15

10

5

0

Stream temperature (oC)

a

A

a b

A B

b

B
15

Although fish populations survive in these streams, they are likely stressed by high

stream temperatures in summer. The trout most likely move to a colder reach of the

stream to help them through these periods. Caribou Creek had the highest density

of age 0 (first year) trout and, yet, had the highest maximum stream temperatures

(Grimes 1980). Caribou and Tinker Creeks had the highest biomass of trout per

square meter, during 1978-80 (Grimes 1980). Age 0 trout correlated positively with

shallow riffles over spawning-size gravel and aquatic vegetation, and negatively with

elevation and water depth (Grimes 1980). Caribou and Tinker Creeks offer all these

stream characteristics. Keeney Creek does not have a trout population because of

a physical barrier, lethal stream temperatures, and ephemeral stream sections. The

trout population of Flood Creek is lower than that of Caribou and Tinker Creeks, but

the trout are larger because Flood Creek lacks spawning-size gravel. Flood Creek,

however, offers some physical cover of logs and streambanks for larger trout.

Conclusions Maximum stream temperatures as high as 28 oC occurred in streams in the study area.

Streams can be classified into temperature groups by watershed and environmental

parameters (elevation, travel time, stream shade, and 7-day low flow). Increasing

intensity of range management strategy did have a significant effect on stream temperature resulting in temperatures that exceeded limits for fish. This was not definitive,

however, and likely was due to the strong influence of watershed characteristics and

effects of prior grazing and management. Ecosystem had a significant (p < 0.05) effect

on mean weekly stream temperature. Larch/Douglas-fir and fir/spruce had similar

mean weekly stream temperatures, but they were significantly lower than those of

ponderosa pine and mountain meadow. Mean weekly temperatures of the lodgepole

pine ecosystem were intermediate between the other ecosystems. Watershed characteristics that had a significant (p < 0.001) effect on stream temperature were shade,

stream elevation, travel time, and flow. A strong first-order autocorrelation was found

on stream temperature measurements within all watersheds.

Streamside vegetation is essential in providing shade that keeps stream temperatures from reaching lethal levels. Watersheds with less than 75 percent surface

stream shade can exceed stream temperature standards for rainbow trout and

chinook salmon. All three strategy D watersheds and one strategy C watershed

exceeded this standard because sufficient streamside shade from vegetation was

lacking within the riparian areas of these watersheds. Once the streamside vegetation was removed, little protective shade remained in the meadow ecosystem.

Revegetation of the streamside areas with shrubs or small trees likely would result

in reduced stream temperatures and an improved environment for rainbow trout and

chinook salmon.

Management practices within the riparian zone could be implemented to reduce

adverse impacts on the streams and their dependent trout populations. Streamside

vegetation is probably the most easily manipulated variable. Maintenance of the

integrity of the riparian zone could be achieved by using buffer strips and by more

stringent control of animal use of riparian areas.
16

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Maloney, S.B.; Tiedemann, A.R.; Higgins, D.A.; Quigley, T.M.; Marx, D.B. 1999.

Influence of stream characteristics and grazing intensity on stream temperatures

in eastern Oregon. Gen. Tech. Rep. PNW-GTR-459. Portland, OR: U.S. Department of

Agriculture, Forest Service, Pacific Northwest Research Station. 19 p.

Stream temperatures were measured during summer months, 1978 to 1984, at 12

forested watersheds near John Day, Oregon, to determine temperature characteristics and to assess effects of three range management strategies of increasing intensity.

Maximum stream temperatures on four watersheds exceeded 24 oC, the recommended

short-term maximum for rainbow trout and chinook salmon. Although highest temperatures were observed in the most intensively managed watersheds, the effect of range

management strategy was not definitive. It was confounded by watershed characteristics and about 100 years of grazing use prior to initiation of this study.

Keywords: Forested watersheds, grazing management strategies, grazing intensity,

fisheries, fish habitat, chinook salmon, steelhead trout, cutthroat trout, Dolly Varden

trout.

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