Bulletin ofGlaciologicalResearch22（2005）5761∫7◎JapaneseSocietyofSnowandIce

Effectofwinterwarmingonthestreamwateracidification
Keisuke SUZUKI

DepartmentofEnvironmentalSciences，ShinshuUniversity，Matsumoto3908621，Japan（Received September17，2004；RevisedmanuscriptreceivedOctober29，2004）

Abstract
WestudiedtheannualvariationofthepHofstreamwaterinasnowytemperatearea，Whererain

OrtempOrary Warmingcancausefrequentmeltingatthesurfaceofsnow cover，eVeninmid−Winter
Withitsintermittentsnowfall．Ontheotherhand，inthesnowycoldarea，theairtemperatureseldomrisesabovefreezingpointduringwinter．WereportedtheseasonalvariationofthepHofstreamwaterin a snowy temperate area．The pH value ofstream waterin a snowy temperate area was always

Changeably，decreasingln COldseasonsandincreasinglnWarmSeaSOnS．Thedropln pHduringthe

SnOWmelt season was remarkable．Although the pH drop of stream water was also temporarily

Observedinfl00dingduringwarmseasons，relativelylongpHdropswereobservedincoldseasons．

TheairtemperatureandthesnowdepthinwinterdeterminethepHofstreamwaterinthesnowmelt
SeaSOn．WeexaminetherelationshipbetweenthepHofstreamwaterinthesnowmeltseasonandthe
airtemperatureand thesnowdepthin winter．Themonthlymeantemperaturein Februaryisvery

Closely correlated with the monthly average pH ofstream waterin March．Furthermore，the maxi−

mumsnowdepthisalsocloselycorrelatedwiththemonthlyaveragepHofstream waterinMarch．

withitsintermittent snowfall．On the other hand，in1．lntroduction

thesnowycoldarea，theairtemperatureseldomrises

ThroughoutthelakesofeasternCanadaand Sca−
ndinavia，effectsofacidicpreclpitationon theinland

portedtheseasonalvariationofthequalityofstream
Waterin a snowy temperate area．The pH value ofStream Waterin asnowy temperateareawasalways
Changeably，decreasingincoldseasonsandincreasing
inwarmseasons．ThedroplnpHduringthesnowmeltSeaSOnWaSremarkable．AlthoughthepHdropofstrT
eamwaterwasalsotemporarilyobservedinfl00ding
during warm seasons，relativelylong pH drops were

Water eCOSyStem have been reported（Gorham，1961；
Beamishand Harvey，1972；Johannessen and Henrik−
Sen，1978；Jeffries etal．，1979；Minns，1981）．Geologic
and soilconditionsin the catchment of thoselakes

provide only a weak buffer agalnSt aCidic precipita−tion，and the alkalinity of theinland waterislow．

Furthermore，inthoseareasmostpreclpitationoccurs

assolid precipitation，namelysnowfall，Whichcovers

theground forabout halftheyear．Duringsnowmelt
SeaSOn，the acidic substances which deposited fromthe atmosphere to snow by wet and dry processes，
flowoutfromsnowcoverrelativelyallatonce．Thus
thepHofstreamwaterandlakesdropsrapidlyduring

the snowmelt season．Acidic preclpitationis also ob−
SerVedinJapan，Wherethereisasmuchacidicdeposi−tion asin eastern Canada（LangnerandRodhe，1997）．

Nevertheless，thelargebuffercapacityofthesoiland
the high alkalinity of theinland waterinhibitacidic
precipitationfromdirectlyinfluencingtheinlandwa−
terecosysteminJapan．
Thesnowy temperate areaisdefined asthearea
Wheretemporarywarmingorraincausefrequentmel−

above freezing point during winter．Suzuki（2003）re−Observedin cold seasons．

We present a relationship between the stream

WateraCidificationandthewinterwarming，Which，in
this context，isimportant for atleast two reasons．

First，thewinterwarmingaffectsthedegreeofstream

Water aCidificationin the snowmelt seasons．Second，

the monthly mean air temperature in February canforcastthemonthlymeanpHvalueofstreamwaterin
March．WefocusonthecontinuouspHobservationof
StreamWaterandonitscomparisonwiththeairtem−
peratureandsnowdepthrecords．
2．Methods

The forested stream studiedin this reportislo−

Catedin Fukushima Prefecture，nOrtheasternJapan．

tingatthesurfaceofsnow cover，eVenin mid−Winter The catchmentareais O．14km2at anelevation of745

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︻lFig．1．Thevariationsin daily mean airtemperature（Ta），SnOW depth（HS），pHofthestream water，anddailyrunoff（RO）
in thefivewateryears．

thepHmeter（TOACo．Ltd．，HM−30V）．
to 910m a．s．1．The surface soilof the catchmentis
Theweatherobservationfieldwassetupatabout
Sedimentary rock consisting of tuffsandstone，COn−glomerate，tuffbrecciaandtuffneogene，andthebed− 120meastfromthedischargemeasurementweir，Onaridge at754m a．s．1．In the observation角eld，air tem−rockisexposedonmoststreambedsexceptfordown，Stream．

In order to measure the stream discharge，a900

peraturewasautomaticallymeasuredbyaventilated−

V−nOtChstainlesssteelweir wasinstalled．Apressure
SenSOranddata−logger（KONAsystemCo．Ltd．，KDC−S
lO＆KADEC−US）were employed for the automatic

type temperature sensor（KONA System Co．Ltd．，
KDC−SO2＆KADEC−US），and snow depth by a snowT
depth gauge（KONA System Co．Ltd．，KADEC−S6＆KADEC−UP）．

measurements were used to calculate discharge．Str−3．ResuIts and discussion

measurement of the waterlevelat this weir；theseeam water was periodically sampled with an auto−

Observations are conducted for the 丘ve years
from Decemberl，1991，tO November30，1996．In theinwarmseasons，andrangedbetweenland60hours． CatChmentstudied here，mOnthlyprecIPitationislow−
matic water sampler（ISCO Co．Ltd．，2900）．The sam−plingintervalwassetshortin cold seasons andlong
And the pHofstream waterwas measuredby using

estinApril，yetStreamdischargepeaksatthistimeof

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4
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7Fig．2．Thefluctuation of monthly averages of the stream water runoff（RO）
andpHofthestream waterforthefivewateryears．
1year，Sinceitis the snowmelt season．November has
Inordertoclarifytheseasonalvariationinstream
thesecond，lowestamountofprecipitationbut，unlike WaterpH，themonthlymeanofpHisexaminedbelow．
April，its rate of stream dischargeislow．Henceit
Figure2illustrates the monthly averages of the str−

SeemSreaSOnabletodefineawateryearasbeginningin December．

The variationsin dai1y mean air temperature，eamrunoffandthestreamwaterpHforthefivewatcr

years．Inthisstream，therunoffincreasesinthesnow

meltingperiodofMarchandAprileveryyear，andthe
pHofstreamwaterdecreasesinthesameperiod．The

dailymaximumsnowdepth，pHofstreamwater，and
dailyrunoffduringthe艮vewateryearsareillustrated runoff of stream water alsoincreasesin the warmin Figurel．The snow depthin winter1993is relaT
SeaSOn，namely Bai−u and typhoon periods，but thetivelylow，Withamaximumdepthofsnowcoverof98
Cm．Thedailymeantemperatureinwinter1993isalso
higher thanin other years．The peak value of daily
runoff during the snowmelt seasonin1993is thelowest throughout thefive years．Thesnow depthin
Winter1996is the highest，With a157cm maximum
depthofsnowcover．Thetotalrunoffofthesnowmelt
SeaSOnin1996isthelargestthroughoutthefiveyears．
ThepHofstream watershowsannualvariationsthr−monthlyaveragepHdoesnotshownoticeablechange
at these times．The monthly average pH of stream
Waterishigherinthewarmseason，andthedifference
in monthly average pH between warm season andSOnSandincreasinglnWarmSeaSOnS．Thedecreasing
OfpHvalueintheearlystageofthesnowmeltseason
is remarkable every year．Although the pH drop ofStreamWateristemporarilyobservedalsoinfl00ding
during warm seasons，relativelylong pH drops are

1993，When the snow depth was thelowest and theWinterairtemperaturewashigh，themonthlyaveragefrequentlyinthecoldseasonin1993thaninthecold

Itis assumed that theair temperature and thesnow depth in winter determine the pH of stream

Oughoutfive years，decreasingin the snowmelt sea−

COld seasonis approximately O．2to O．3．ThelowestmonthlyaveragepHduringtheobservationperiodis

5．92inMarch1996．Inthewinterof1996，aSmentioned
before，thesnowdepthwasthelargestintheobserva−

tion period and the winterairtemperature wasrela−

tivelylow．Ontheotherhand，thesnowmeltseasonof

pHofstreamwateronlydecreasedto6．15．Likewise，inthe snowmelt season of1995，When the winter air
temperature was high，the monthly average pH ofObservedin cold seasons．However，pH droppedless Stream Wateralsodecreasedonly to6．15．
SeaSOnSin1992，19940r1996．Thisis considered to betheinfluence of winter warming and oflittle snow

duringwinter1993．Unlessmeltingtakesplace，Chemi−

Calsubstancesdepositedbysnowfallanddrydeposi−tion are preservedin the snow cover（Suzuki，1982）．
However，if meltingoccursfrequently，Chemicalsub−

StanCeS do not accumulatein the snow cover，SO theWaterinthesnowmeltseason．Therefore，WeeXamine

the relationship between the pH of stream water inthesnowmeltseasonandtheairtemperature，andalso
between the snow depthin winter and the air tem−
Perature．The pH of stream wateris represented bythemonthlyaverageofMarch，Whensnowmeltingis

SnOWmeltacidificationmechanismhardlyworks．The− themostactive（Suzuki，2003），andthemonthlymeanrefore，itisassumedthatonlyaslightpHdroplnthe
stream wateris observedin the snowmelt seasonin
1993．

temperatureisrepresentedbythatofFebruary，When
themonthlymeantemperatureisthelowest．Figure3
Shows the relationship between the monthly meanBulletinofGlaciologlCalResearch

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100 120 140 1 0 1別）
HSmax（Cm）

Fig．3．Therelationshipbetweenthemonthly meantemperatureinFebruaryandthemonthlyaveragepHinMarch，andbetweenthemaximumsnowdepthandthemonthlyaveragepHin March．

temperatureinFebruaryandthemonthlyaveragepH
in March，aS Wellas the relationship between themaximumsnowdepthandthemonthlyaveragepHinMarch．ThemonthlymeantemperatureinFebruarylS
VeryCloselycorrelated withthe monthlyaveragepH
in March．Itis clear that when the monthly mean
temperatureofFebruaryishigh，themonthlyaverage
pH ofstream water of Marchis high，and when themonthly mean temperature of Februaryislow，themonthlyaveragepHofstreamwaterofMarchislow．
ItclearlyshowsthattheairtemperatureinFebruary
affectsthe pHofstream waterinMarch，Whensnow

meltinglS the most active．Furthermore，the maxi−

mum snow depth is also closely correlated with themonthly average pHin March．When the maximum

SnOW depthislarge，the monthly average pH ofstr−

eam waterin Marchislow，and when the maximum

SnOW depthis small，the monthly averagepH ofstr−

eamwaterinMarchishigh．Itshowsthatsnowdepth
inwinteraffectsthepHofstreamwaterinthesnow−
melt season．

In the snowy temperate areas，Slightincrease ofairtemperatureinwinterchangessnowfalltorain．Itmeans that evenif the amount of precIPitationin
winteristhesame，higherairtemperaturereducestheamount of snow cover．In other words，the air tem−

peraturein winterdirectlyinfluences the amount ofSnOWCOVerinthesnowytemperateareas．Ithasbeen
reported thatglobalwarmingreducestheamountof
SnOWCOVerinthesnowyregion．Thispaperexamined
the relationship between meteorological conditions
duringwinterandthepHofstreamwaterandfoundthatglobalwarminginfluencesthepHofstreamwa−

terin the snowmelt season．

4．Conclusion
The pH of stream water in a snowy temperate
CatChment wasinvestigated throughoutfive wateryears．In the snowy temperate catchment，melting

OCCurS frequently due to temporary warming or to

rainfalloccurring evenin mid−Winter．In such cases，

thepHofstream waterdropstemporarily．ThepHof
stream water shows annual variations throughout
five years，decreasingln the snowmelt seasons andincreasingln Warm SeaSOnS．The decreasing of pH
Valuein the early stage of the snowmelt seasonis

remarkable every year．The monthly mean tempera−

turein FebruarylS Very Closely correlated with themonthly average pHin March．It clearly shows thatthe air temperature in February affects the pH of
Stream Waterin March，When snow meltinglS themostactive．Themaximumsnowdepthisalsoclosely
COrrelated withthe monthly averagepHin March．It
shows that snow depth in winter affects the pH of
Stream Waterin the snowmelt season．In the snowy

temperate areas，theair temperaturein winter di−

rectlyinfluencesthesnowdepth．Ithasbeenreported
that global warming reduces the amount of snow

COVerinthesnowyregion．Weexaminedtherelation−

ShipbetweenmeteorologlCalconditionsduringwinterand the pH of stream water and found that global
Warminginfluences the pH of stream waterin theSnOWmelt season．

Suzukiliノ

pHinlakesandstreamsincentralOntarioduringsnow−
melt．JournaloftheFisheriesResearchBoardofCanada，36，640▼646，
Johannessen，K．andA．Henriksen（1978）：Chemistryofsnow−
This research was supported by a Grant−inTAid
meltwater：Changesin concentration during melting．
WaterResourcesResearch，14，615−619．
for Scientific Research（03455020＆06453198）of theLangner，］．and H．Rodhe（1997）：Estimates of preindustrial，Japanese Ministry of Education，Culture，Sports，Sci−present，andfuturesulfurdepositionwithaglobalthree
enceandTechnology．
dimensionalmodel．in GlobalAcid Deposition Assess−ment，editedbyD．M．Whelpdale and M．S．Kaiser，WMO
Publication，No．106，225230．
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Acknowledgments

840．

Jeffries，D．S C．M．Cox and P．］．Dillon（1979）：Depression of2810．