VOL. 6, NO. 4 WATER RESOURCES RESEARCH AUGUST 1970

Eects o[ Clear-Cuttingon StreamTemperature

GEORGE W. BROWN AND JAMES T. KRYGIER OregonState University, Corvallis,Oregon 97331

Abstract. The principal source of energy for warming streams is the sun. The amount of sunlight reaching the stream may be increasedafter clear-cut logging. Average monthly maximum temperaturesincreased by 14øF and annual maximum temperaturesincreased from 57ø to 85øF one year after clear-cut logging on a small watershedin Oregon'scoast range. In a nearby watershedwhere strips of brush and trees separatedlogging units from the stream, no changesin temperature were observedthat could be attributed to clear- cutting.

INTRODUCTION may cause fish mortality [Brett, 1956]. The growth of fish may be directly affectedby water Timber, water, and sport and commercialfish temperature as demonstrated on juvenile coho are the principal resourcesin the Oregon coast salmon [Brett, 1956]. In short, water tempera- range. The need for delineating the areas of ture is a major determinant of the suitability of conflict between logging and utilization of the water for many uses. other resources led to the establishment of the Research has been limited on temperature AlseaLogging-Aquatic Resources Study in 1958. changesin smallstreams from land use,although The purpose of this broadly interdisciplinary fisherybiologists have long been concernedwith study was to determine the effect of logging on the effects of deforestationon water tempera- the physical,chemical, and biologicalcharacter- ture. Meehan et al. [1969] studied the effectsof istics of small coastal streams. clear-cutting on the salmon habitat of two The purposeof this paper is to describethe southeastern Alaska streams. They noted a long-term effects of two clear-cuttingson the statisticallysignificant increase in mean monthly temperatureregime of two small streams in temperatures after logging. The maximum in- Oregon'scoast range. One watershedcontained crease in average monthly temperature was three small clear-cuts; the edgesof the clear- about 4øF. The increasein maximum tempera- cuts were at least 100 feet from the stream. The ture was about 9øF during July and August. secondwatershed was completelyclear-cut. An During a study of logging and southeastern earlier report [Brown and Krygier, 1967] de- trout streams, Greene [1950] reported that scribedthe first-year effect of clear-cuttingonly maximum weekly temperaturesrecorded during during the loggingoperation on the completely May on a nonforestedstream were 13øF higher clear-cut watershed.This report reviews results than thoserecorded on a nearby forestedstream. from a network of 18 thermograph stations He noticed also that the maximum temperature distributedthrough the watersheds.The obser- dropped from 80ø to 68øF after the nonforested vation period extends from two years before stream meanderedthrough 400 feet of forest and loggingthrough the fourthsummer after logging. brush cover. Temperature is a significantwater quality Levno and Rothacher [1967] reported large parameter.It stronglyinfluences levels of oxy- temperature increases in two experimental gen and solidsdissolved in streams.Tempera- watershedsin Oregon after logging. The shade ture changescan inducealgal bloomswith sub- provided by riparian vegetationin a patch-cut sequentchanges in taste, odor, and color of a watershedwas eliminatedby scouringafter large stream.Warm water is conduciveto the growth floods in 1964. Subsequently, mean monthly and developmentof many speciesof aquatic temperatures increased7ø-12øF from April to bacteria, such as the parasitic columnaris August. Average monthly'maximums increased disease.Increased populations of thesebacteria by 4øF after complete clear-cutting in a second

1133 •'134 BROWN AND KRYGIER

•ER CREEK

FLYNN CREEK

TOLEOO ? TO •CEg HANLAN

ALSEA WATERSHED STUDY NEEDLE BRANCH • I/4 -- I/• MILES

LEGEND

FISH TRAP FOREST SERVICE NO•,D LABORATORY STREAM STREAM GAGE LOGGING UNIT THœRMOGRAPH Po.T TOLEDO

STUDY ARE A

Fig. 1. The watershedsof the AlseaBasin Logging-Aquatic Resources Study. watershed. The smaller increase in the corn- THE STUDY pletelyclear-cut watershed was the resultof Threeexperimental watersheds are included shadefrom the logging debris that accumulated in the Alsea Logging-Aquatic Resources Study in thechannel. (Figure1). Thesewatersheds, which vary in Patric[1969] compared the effectof two sizefrom 175 to 750acres, are locatedin clear-cuttingpatterns on water quality. Tern- Oregon'scoast range about 10 miles from the peratureswere unaffected by clear-cuttingthe PacificOcean. Each stream is an important upperhalf of onewatershed. Clear-cutting the rearingarea for cohosalmon (Oncorhynchus lowerhalf of the secondwatershed increased kisutchWalbam) and coastalcutthroat trout temperaturesup to 7øF. (Salmoclarki clarki Richardson). In its natural Stream Temperature 1135 condition,the study area was denselyforested 100•--•'"•, ! , I •..... ' "'"''' [ i with Douglasfir (Pseudotsugamenziesii [Mirb.] •o1-• -• •• ,o•,.• Franco)and redalder (Alnusrubra Bong). The study streamswere overgrownwith salmon- berry (Rubusspectabilis Pursh.), vine maple 20 (Acer circinatumPursh.), and other species. 0 i Although annual precipitationis about 100 I inches,the summermonths are generallyhot 100•• , , j , , , , [ , and dry. Summerstreamflow regularly drops below 0.20 cubic feet per second(cfs) or 0.17 cubicfeet per secondper squaremile (csm)on DeerCreek, the largest watershed, and to 0.01 20 . i cfs or 0.04 csm on Needle Branch, the smallest 0 ' ' I , i watershed. I0O• i ' I I ' ' ' I ' _ The low summerflows described above may seeminsufficient to supportsalmon. The adults, Lx however,spawn in thesestreams during the highflows of the wintermonths. Salmon finger- 20 lings live in thesestreams during the summer. 0 I [ i The fingerlingsinhabit pools,many of which i

I00•, , , I ' ' ' ' I ' _ becomenearly isolated during the late summer. .oR• k •R,.• •o•,.• In the fall, the yearlingfish migrate to the sea 60

40 E [ I I [ [ I [ ' I ' ' 14 20 0 I , i i 1967 I00• , , , I ' • • ' I ' '"' 80

PATCH CUT •oy •X• ,c•. cut 1968 i , ,'o.... 20'' DIURNAL TEMPERATURE CHANGE, DEGREES F :D 70 Fig. 3. A frequency distribution of diurnal temperature changeson the clear-cut, patch-cut, and uncut control watersheds before (1965), dur- 1969 ing (1966), and after (1967-1989)logging for the 966 summer period, June 1-October 1.

6O when rains again increasestreamflow. Before 1965 logging,the number of yearling fish passing

ß ß ß ß ß ß ß ß ß through the fish trap to the sea ranged from ß ß m ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß 1809 to 3175 in Deer Creek and from 166 to ß ß ß ß ß ß ß ß ß ß 630 in Needle Branch [Hall and Lantz, 1969]. ß...... •'"'•-CONT ROL 1965-1969 The study was designedto permi• comparison 5O of two different logging patterns. One water- , [ I I, I [ [ I [ , shed, Needle Branch (175 acres), was fully 6 12 18 24 HOUR (PST) clear-cut.A secondwatershed, Deer Creek (750 acres), was patch-cut; 25% of this area had Fig. 2. The temperaturepattern on the days several clear-cut units. The remainder of the of the annual maximum recorded on the clear- cut and uncut control watersheds before (1965), watershedwas unlogged.In Deer Creek, strips during(1966), and after (1967-1969)logging. of vegetationwere left alongthe l•eren•ial 1136 BROWN AND KRYGIER streams. A third watershed, Flynn Creek (502 series compared daily maximum temperatures acres), was left unlogged as a control. Two recorded June 1-October 1 of the pretreatment small subwatersheds in Deer Creek also served years with the daily maximums for the same as unlogged controls. periodduring eachtreatment year. The analysis Eighteen 7-day thermographs, accurate to was applied to data from the control as well 0.5øF, were installed in the three watersheds as from the patch-cutwatershed to ascertainthe to evaluate the effect of the cutting (Figure 1). effects of climate. Thermographswere placedbelow eachproposed loggingunit and at the junction of each major Diurnal Temperature Regimes tributary in Deer Creek so that effects within The temperature patterns recorded on the the watershed could be determined. In Needle days of the annual maximum on the clear-cut Branch, thermographswere distributed within watershed from 1965 to 1969 are illustrated in the clear-cutting to evaluate the spatial tem- Figure 2. The valuesfor 1965 and 1966 occurred perature changesoccurring in a fully exposed at the watershed outlet. The values for 1967, stream. Thermographswere installed in March 1968, and 1969 occurredwithin the cutover unit. 1964. Probeswere placedin flowingwater deep A thermographwas installedat 1000 feet above enoughto insure completecoverage throughout the outlet in the spring of 1967, after intensive the year. The years 1964 and 1965 served as samplingshowed that the maximum occurredat control periods, and the years 1966-1969' as this location.This inconsistencyin the tempera- treatment periods. ture pattern was the result of incomplete re- Road building was completed in 1965, but, moval of shade from the lower portion of the becausethe roads were built on ridges, little stream channel after logging and burning. The change occurred that could be interpreted as variation in temperaturesrecorded at the outlet having any influence on water temperature. of the unloggedwatershed for the same days is Logging began in March 1966 in both water- also shown. Minimums recorded on the clear-cut sheds and was completed in August on Needle watershed are about the same as the maximums Branch and in November on Deer Creek. In recordedon the unloggedcontrol. This phenom- October 1966, the stream in the clear-cut enon occurs becausetravel time through the watershed was cleared of logging debris. After clear-cut watershed is greater than 24 hours clearing, a well-distributed burn removed most during the low flow period. Convection and logging debris and streamsidevegetation. Re- nocturnal back radiation are insufficient to cool ported data extendthrough September 1969. the water to the same minimums measured on the control. The maximum diurnal fluctuation RESULTS recorded on the clear-cut watershed was 28øF The data from this study have been analyzed during 1967. The maximumtemperature, 85øF in two ways. The large changesthat occur after during 1967, representsan increaseof 28øF over clear-cutting are presented graphically. The the preloggingmaximum of 57øF for 1965. The small changes that occur after patch-cutting decline of maximum temperaturesafter 1967 required a statistical analysis to ascertain the representsthe rapid return of streamsidevege- significance of these changes. The standard tation in this watershed. statistical technique of regressioncould not be The maximum temperaturesrecorded on the used because of the nonrandom effects of cli- patch-cut watershedwere 60ø and 61.5øF for mate, the lack of independencebetween suc- 1965 and 1967, respectively. The maximum cessive daily maximums, and the potential diurnal fluctuation during both years was 10øF. alteration of the varianceof seasonaltempera- A cumulative frequency distribution of the ture distributionsby logging.A stationarytime diurnal fluctuationsin temperature at the outlet series was developed to circumvent these diffi- of all three streams from June 1 to October 1 culties [Beck, 1968]. Time seriestechniques are for the years 1965-1969 is shown in Figure 3. commonly used for analysis of weather data The temperature stability of natural, forested where similar difficulties abound. Jenkins and streams is illustrated again in this figure. The Watts [1968] describethe application of this maximum fluctuations in temperature before techniqueto several such problems.Our time loggingin 1965 were 6 ø, 8 ø, and 10øF on Flynn Stream Temperature 1137 Creek, Needle Branch, and Deer Creek. These TABLE 1. A Time Series Analysis of the Dif- maximum fluctuations were not exceeded on ference between Daily Maximum Temperatures of Streams before and after Patch-Cutting for the Flynn Creek or at any station within Deer Period of June 1 to October 1 Creek during or after logging. On Needle Branch, the maximum fluctuation of 8øF was Temperature Change, øF exceeded28% of the time in 1966 and 82% of the timein 1967,the year immediatelyfollowing Watershed 1966 1967 1968 burningand streamclearance. This percentage Flynn Creek 0.8 2.3* 0.3 droppedto 46% in 1968and 36% in 1969,again (unlogged) reflectingthe regrowthof streamsidevegetation. Deer Creek 0.4 1.9* -0.4 The outlet stations are representativeof the (patch-cut) changesthat occurred within each watershed. Temperature fluctuations generally decreased * Significant at the 5% level of probability. with distanceupstream in the patch-cutwater- shed.The most remotestation (station 15) in (station 15), the changesrecorded at the outlet the clear-cutwatershed performed similarly to station are representativeof those occurringat the outlet of Deer Creek. the other stations within the clear-cut water- shed. Again the highest temperatures occurred Monthly Maximum Temperatures during 1967, the year after stream clearance Clear-cut. Maximum daily stream tempera- and slashburning. The mean monthly maximum tures averaged by month for one year before for July increased from 57øF in 1965 to 71øF and four years after loggingare shown for the in 1967. The trend toward the preloggingcon- outletsof the clear-cutand unloggedwatersheds dition is shown again in this figure. in Figure 4. Except for the most remote station Patch-cut,. The frequencydiagram illustrates the nearly constantpattern of daily temperature fluctuationrecorded on the patch-cut watershed throughoutthe study (Figure 3). A time series was required to determine whether the small increasesobserved initially were the result of logging or climatic differencesbetween years. The results of the time seriesare presentedin Table 1. Significant changes in the summer maximum temperatureswere observedat the outlets on the control and patch-cut watershed one year after logging. The larger changes observed on the control indicate that climatic factors, and not the patch-cutting, were re- sponsible for this increase. During 1966 and 1968, summer maximums in the stream of the patch-cut were nearly the same as those ob- served before logging. The 10 internal stations exhibited smaller changesin temperature than the outlet station. These data show that patch- cutting, which leavesstreamside strips of brush and trees, did not alter the temperature pat- terns of the adjacent stream. Other inferencesabout the temperature pat- terns may be drawn from these data. Clearly the patternsin summertemperatures of forested Fig. 4. Mean monthly maximum temperatures for the clear-cut and uncut control watersheds streams are relatively constant from year to before (1965), during (1966), and after (1967- year. The small differencesbetween years listed 1969) logging. in Table I and the statistical significanceof a 1138 SROWN AND KRYGIER

2 ø changeillustrate little variability in average streams that must support salmon and trout maximum temperaturefor a summer. during the period of low flow. Can the results of this study be classifiedas typical of western Oregon conditionsor were DISCUSSION they merely causedby unusuallyhot summers? A detailed descriptionof the hydrologicand The maximum temperature of 85øF recorded atmosphericfactors affectingwater temperature for the clear-cut and burned watershed is un- was given earlier [Brown, 1969]. The most im- doubtedly closeto the maximum temperature portant environmental factor governing •em- that could occur for this size of clear-cut water- perature change is solar radiation received at shed and stream. Because of its small size, the the stream surface. stream respondedto each clear day with high Temperature differencesbetween watersheds temperatures, regardlessof the previous day's and all of the temperature anomalieswithin the weather. Even if only one clear hot day had clear-cut watershed can be explained in terms occurred, this temperature would have been of shade differences.The patch-cuts on Deer observed.The records of mean monthly tem- Creek did not produce any significantchanges peratures and the frequenciesof diurnal change in temperature in the main stream. Strips of present data for longer periods. The number of timber 100 feet long were left beside each days of sunshine,overcast, fog, and rain in- perennial stream; the amount of shade on the fluencesuch results. Long-term recordsof sun- stream surface was essentiallyunchanged. On shine are not available for the study area. Needle Branch, little shade remained after the Records at nearby stations, however, indicate clear-cutting and burning were completed.As a that the period of study was not abnormal. result, large changesin annual and daily pat- Duration of temperature effects following terns of temperature were observed. clear-cutting is the subject of continued ob- The principalcause of highwater temperature servation in these experimental streams. Tem- following loggingis stream surface exposureto perature ameliorationis related to shade de- direct insolation and not increasedsoil tempera- velopment.As stream bank vegetationbecomes ture on the clear-cut slopes as suggestedby reestablished,-temperaturesdrop accordingly. Eschner and Larmoyeux [1963]. Satisfactory In many of the watershedsof the Pacific North- predictionsof temperature have been made on west, regrowth occurs very rapidly on moist Deer Creek and Needle Branch with net radia- sites. On the basis of our data, it seemsthat tion as the primary parameter. On these same summer maximums may approach preIogging streams we found that the maximum rate of net levels within six years after logging has com- thermal radiation added to the unshaded stream pletely exposedthe stream if vigorousinvasion in the clear-cut watershed was more than 10 of such moist-site speciesas alder, salmonberry, times that added to the shaded stream in the elderberry, and vine maple occurs.The decline patch-cut watershed.These differencesare re- of high temperaturesnoted in Figures 2, 3, and flected in the postloggingtemperature patterns 4 after the 1967 maximum on Needle Branch of each stream and help explain the tempera- illustrate this recovery. The stream's tempera- ture stability of most forested streams. ture patterns are well on the way to returning For a given level of solar radiation or heat, to the preIoggingcondition. stream temperature is inversely proportional to Our research reported here and a companion volume. As a result the temperature patterns of study [Brown, 1969] have illustrated the effect small, shallow streams typical of headwaters of two patterns of loggingon the temperature regionsmay be increasedsignificantly by any of small coastal streams and the amelioration changesin the solar radiation.Stream discharge of the effect with time. These results, however, in the clear-cut watershed regularly drops to have raised several questionsabout temperature 0.01 cfs during the hot summer months. Thus control in the managementof fishery,forest, and the large changesin temperaturerecorded after water resources.Foremost among them is the the shade was removed from this stream. were effect of high temperatures, such as those re- to be expected.The flow regime of this small corded during 1967 in the clear-cut watershed, stream is typical of many western Oregon on fish. Earlier work [Brett, 1952] indicated Stream Temperature 1139 that at 27.5øC (81.5øF) the time required to problem of determining effects of logging on induce50% mortality in a populationof coho water temperature, M.S. report in statistics, Oregon State University, Corvallis, 1968. salmonfry is only 70 minutes.But no unusual Brett, J. R., Temperature tolerancein young Pa- mortality in cohowas observed during this study cific salmon, genus Oncorhynchus,J. Fish Res. even though stream temperatures were often Board Can., 9, 265-323, 1952. above this limit for 4 to 6 hours. Brett, J. R., Some principles in the thermal re- The study illustrated the benefit of strips of quirements of fishes, Quart. Rev. Biol., 31, 75-81, 1956. vegetationalongside small streamsfor tempera- Brown, G. W., Predicting temperatures of small ture control. The width, density, speciescom- streams, Water Resour. Res., 5(1), 68-75, 1969. position, and costs incurred when planning Brown, G. W., and J. T. Krygier, Changing water streamsidestrips are only a few of the questions temperatures in small mountain streams, J. Soil Water Conserv., 22, 242-244, 1967. posedby forest managers. Eschner, A. R., and J. Larmoyeux, Logging and Finally, this study should encouragewater trout: Four experimental forest practices and resourceagencies to engage in further studies their effect on water quality, Progr. Fish Cult., of the aquatic habitat in small streamsand its 25, 59-67, 1963. Greene, G. E., Land use. and trout streams, J. relation to land use. Although the temperature Soil Water Conserv.,5, 125-126, 1950. changesrecorded are definedas thermal pollu- Hall, James D., and Richard L. Lantz, Effects of tion in Oregon'scurrent water quality standards logging on the habitat of Coho salmon and [Oregon Sanitary Authority, 1967], the effect cutthroat trout in coastal streams, in A Sym- on the cohofishery would suggestthat a more posium on Salmon and Trout in Streams, ed- ited by T. G. Northcote, pp. 353-375, University precisedefinition is required. Such a definition, of British Columbia, Vancouver, 1969. of course,will require a better understandingof Jenkins, G. M., and D. G. Watts, Spectral An. the responseof the aquatic systemto tempera- anlysis and Its Application, ttolden-Day, San tures in the lethal and sublethalranges. l•rancisco, 1968. Levno, A., and J. Rothacher, Increasesin maxi- Acknowledgments. The researchwas sponsored mum stream temperatures after logging in old- by the Federal Water Pollution Control Admin- growth Douglas-fir watersheds,12 pp., U.S. istration under grant WP-423 and by Orgeon Dep. Agr., Forest Serv., Pacific Northwest For- State University. Other cooperators in the Alsea est Range Exp. Sta. Res. Note PNW-65, 1967. Logging-Aquatic Resources study include: De- Meehan, W. R., W. A. •Farr, D. M. Bishop, and partment of Fisheries and Wildlife, Oregon State J. It. Patric, Some effects of clearcutting on University; Oregon Game Commission; U.S. salmon habitat of two southeast Alaska streams, Geological Survey; •Federal Water Pollution U.S. Dep. Agr., Forest Serv., Res. Pap. PNW- Control Administration; Water Resources Re- 82, 1969. search Institute, Oregon State University; OregonSanitary Authority, Standardsof quality Georgia Pacific Corporation; U.S. •Forest Serv- for public watersof Oregonand disposaltherein ice; Stokes Lumber Company; and •F. W. Wil- of sewageand industrial wastes,Admin. Order liamson. The authors are particularly indebted SA 26, June 1, 1967. to L. C. Beck and Dr. •F. L. Ramsey, Department Patric, James H., Changes in streamflow, dura- of Statistics, Oregon State University, for their tion of flow, and water quality on two partially assistance in the time series analysis of a por- clearcut watershedsin West Virginia (abstract), tion of our data. Trans. Amer. Geophys. Union, 50(4), 144, 1969.

REFERENCES Beck, L. C., Basic concepts and theory of sta- (Manuscript received January 5, 1970; tionary time series and their application to the revised April 14, 1970.)