[Berg, 1986; Stoddard, 1987]. Acidification of lake .... Melac'k and Stoddard, 1991 ]. Tonnessen [this ...... Dave Clew, Rick Kattelmann, and Kelly. Elder provided ...
WATER RESOURCES RESEARCH, VOL. 27, NO. 7, PAGES 1575-1588,JULY 1991
Solute Chemistry of Snowmelt and Runoff in an Alpine Basin, Sierra Nevada MARK W. WILLIAMS
AND JOHN M. MELACK
CenterJbr Remote Sensingand EnvironmentalOptics, Marine SciencesInstitute, and Departmentof BiologicalSciences, University of' CalO'brnia,Santa Barbara
Snowpack runoff contributionsto the hydrochemistryof an alpine catchmentin the Sierra Nevada were evaluated in 1986 and 1987 by analyzing snowpack, meltwater, and stream water samplesfor major inorganicions, conductance,acid neutralizingcapacity(ANC), and silicate.An ionic pulsein meltwater with initial concentrations twofold to twelvefold greater than the snowpack average, varying with site and with ion, was measuredin lysimeters placed at the base of the snowpack. Maximum concentrations of ions in meltwater were inversely related to the rate of snowmelt; melt-freeze cycles increasedthe concentrationof solutesin meltwater. Hydrogen concentrationin meltwater was buff'eredby ANC producedin part by the dissolutionof particulates.The anionicpulse in meltwater was observed in stream waters during the first 30 days of snowpackrunoff, with NO•concentrationsin stream waters at this time about 1.6-fold greaterthan the averageNO•' concentra-
tionfor the timeperiodof snowpack runoff,CI- about1.5-foldgreaterandSO42-about1.3-fold greater.MaximumH '• concentration duringsnowpack runoff(increase of 170%overwinterconcentrations) occurrednear maximumdischarge.ANC minima occurredat maximumdischargeas a result of dilution, with a decreasefrom winter concentrationsof 70% in 1986and 60% in 1987. Interactions
betweensnowpackrunoffandsoilswereimportantto the chemistryof streamwater.Eightyto ninety
percent oftheH * storedin thesnowpack wasconsumed beforeit reached thebaseofthecatchment. Soilswerea sinkfor NH4t' fromsnowpack meltwater, withlessthanI% of theNHd• released from snowpack storage exported i¾om thebasinasNH,i• . Sulfate concentrations in stream waterswereless
variable thanN(•).• • or CI- concentrations' sorption processes in soilswerea likelycauseforthe regulation of S(),•....... concentrations. Here we report snowpackrunoff contributionsto the hydrochemistry of a headwateralpine catchmentin the
INTRODUCTION
Fieldandlaboratoryexperimentshave demonstrated that Sierra Nevada in 1986 and 1987 and discussfour questions. initialstagesof snowmeltoften have ionic concentrations First, we determine whether the dilute snowpack of the manytimeshigherthanaveragesfor the wholesnowpack,an Sierra Nevada does produce an ionic pulse. Second, we ionicpulse[e.g., Johannessen and Henriksen,1978;Co!investigate the chemicalandphysicalprocesses that deterbeck,1981].Physicalandchemicalprocesses that determine minethe magnitudeandextentof an ionicpulsein a natural theoccurrence,magnitude,and extent of an ionic pulseare snowpack.Third, we determineif the maineffectof snownot sufficientlyunderstoodto predict the ionic concentrapackrunoffisto dilutetheionicconcentrations of streamand tionsof snowpack meltwaterat a pointin time. Researchto lake waters. Fourth, we discussthe hypothesisthat interacdateon the chemistryof snow in the Sierra Nevada has tionsbetweensnowpackrunoffand soilscanbe neglected in shown no evidenceof an ionicpulsein snowpackmeltwater alpinebasins characterized by poorlydeveloped soils. [Berg,1986; Stoddard, 1987]. Acidification of lake and stream waters during spring
snowmelt hasbeenreportedin the United States(e.g., in NewYork by Galloway et al. [1987] and in Michiganby Cadleet al. [1984]), in Canada [JefJ?ieset al., 1979], in Norway [Skartveit and Gjessing, !979], and in Sweden [Dickson,1980].The differentialrelease of ionic solutesin thefirstfractionsof snowpackrunoffis oftenconsidered to be the main cause of the acidification. Interactions between
SITE DESCRIPTION
The Emerald Lake watershed (ELW) is a north-facing
glacialcirque,locatedon the upperMarbleFork of the Kaweah River drainage,in the southernSierraNevada of California(36ø35'49"N,118ø40'30"W). The basinsurfacearea is 120 ha, elevationrangesfrom 2800 m to 3416 m, and
topography is steepandrugged,with a medianslopeof 31ø. Exposedrockscomprise 33%of the surfaceareaof the
snowpackrunoff and soils, which can modify the solute basin,unconsolidated clays,sand,gravels,and talus com-
concentrations of snowpackrunoff,are generallyconsidered priseabout 47%.Bedrock inthebasiniscomposed mainlyof negligible in alpineareasunderlainby graniticbedrock[e.g., graniteandgranodiorite withminormaficintrusions, aplite Dreverand Hurcomb, 1986]. Lakes in the Sierra Nevada dikes,andpegmatite veins[Sisson andMoore,1984;Clow, havethe lowest ionic concentrations in the United States
[Landers et al., 1987],andcatchments in theSierraNevada havea limitedcapacityto neutralizeacids[Melacket aI., 1985; Sickman andMelack, 1989].An important question is howwill snowpack runoffaffectthe hydrochemistry of high-altitude streamand lake watersin the SierraNevada.
Copyright 1991bytheAmerican Geophysical Union. Paper number90WR02774. 0043!397/91/90 WR-02774505.00
1987].Conversion of plagioclase to kaoliniteis thepredominantweatheringreactionin the basin[Clow, 1987].Poorly
developed soilscoverabout20%of thebasin,andtheseare acidicandweaklybuffered[HuntingtonandAkeson,1986; Brownet al., 1990].Theprimaryclaymineralsarekaolinite, illite, and severaltypesof vermicu!ite[Weintraub,1986]. Vegetation is sparse,including only scattered coniferous trees,although lowwoodyshrubs areoftenabundant where soilsoccur [Rundelet al., 1989].
1575
1.576
WII.! IAM%AND MI.[ A( K: (.'!•!F, MI,%IRY ½)F•N()WMI I I AND Rt•N()F!•
3000
3300
EMERALD LAKE BASIN co.•o•. ,..•.•^• • • SEQUOIA NATIONAL PARK
2sM•TERS
•
100200
METERS
I;ig. !. 'l',•>pographic map of the Emerald!.ake watershedand lt'changesin (',, and C•,t0
lO-June
changesin AI ,K during the period of spring runoff'is thrther
Fig, 13. Alkalinity(AI•K = ('t, - Ca), ('t,, andstrongacidanion (Ca) concentrations of inflow2 in 1986.A representative sample water collectedprior to snowpackrunoff'(January7)is comparedto samplescollectedduringe!ewttedanionconcentrations(May 1) and during the dilution period of snowpack runoff' (.lune 101. The decrease in alkalinity on May 1 relative to January 7 was due primarilyto increasesin (', (80%) and secondarily
illustmttcd by comparingAI,K to the ratio of (', to C•, (Figure14).At inflow2 in 1986the decreasein A!.K inearly May was the resultof an increasein the ratk)of 4'. to C•, AI.K
then increased in concentration
due t• a decrease in
the (', to (), ratio. l)uring the remainder ()1'springrunoff, AI..K decreasedas the m•tioof 4', to C), renminedrelatively constantand both (', and ('•, decreasedin concentration. Springprecipitationin 1987resultedin the (', to (), ratio0f P < 0.0001' n = 21) and not significantlycorrelatedwith C,, inflow I increasing through the m•)nth of May as ALK (r2 = 0,10;P = 0.16;n = 21).Dilutionof ANC bysnowpack decreased. The rain events in late May •tnd early June runoff'is consistent with similar findingsby Stoddard [!987] causeda peak in the (', to (), ratio)of ().72, which cc)rre(20%).
at Gem Lake and by i. oran/,er and Brakke [1988] in the Cascades.
However, during the first part of snowmelt, runoff alkalinity declineddue to the increasein concentrationel'strong
spondcdwith the AI..K minimum. AI,K then increasedwith time,as the (',, to (.;t, ratio decreasedtoward presnowpack runoff'concentrations. Alkalinity of the outflow tblloweda similar pattern in N•th years; however, the changesin
Inflow 2, 1986 60-
40-0.4
20-0.2
1
Apr
May
I
June
I
Inflow 1, 1987 -0.8
60-
-0.6
40-0.4 20-
-0.2
0
Mar
I
Apr
•
May
I
June
I .......0
Fig. 14. Atimeseries ininflowing waters ofALK (Cb- Ca)andtheratioof CatoC• during theperiodofsnowpack runoff in 1986and1987.At inflow 2 in 1986thedecrease inALK inearlyMaywasprimarily fromincreases in Ca.At inflow1in 1987thelargeincrease in theCato COratioanddecrease in ALK in lateMayandearlyJunewasassociated with spring precipitation.
WII.I,IAMSAN[) M[:I•AC'K: CIIEMISTRYOF SNOWMELT ANDRUNOFF
Co,andalkalinity of theoutflow at alltimeswerelessthan
!587
Interactions between snowpack runoff and soils were
thatof inflowingwaters. The attentuationof theseconcen- importantto the hydrochemistryof the basin. Soils were an trations in theoutflowwithrespectto theinflowsistheresult apparentsinkfor NH•- in snowpackrunoffand in spring of combining inflowingwaters with differentchemistries, precipitation. Oxidationof NH[ in soilsmay havecontribandwith dittOringlake water chemistry,in the hike outflow. uted to the elevatedNO•- concentrationsin streamwaters. Massbalancecalculations andthe low H • concentrations Sulfate concentrationsin stream waters were apparently
instream watersrelativeto H • concentrations in thesnow- regulatedby soil processes.Eighty to ninety percent of the runoffandspringprecipitation wasneutralpack andin springprecipitation indicate thattheH+ in H + in snowpack snowpack runoffwasneutralized bet•re it reachedEmerald ized before it reached Emerald Lake. Lake. Ion exchange, weathering, adsorption, titration of
HC03-, andprotonation of anionsof weakorganic acidsare
allpossible sources ofH • buffering during snowpack runoff. Discriminationof the various processes that may have
neutralized the H -• in snowpackrunoffis beyondthe scope
ofthispaper.The consumption of H * doesindicatethat interactionsof snowpack runoff with physical and chemical
processes in thebasinarean importantfactorin thechemistryof stream waters. SUMMARY ANI) C()NCI.USIONS
Acknowledgments. Kathy Tonnessenprovided encouragement throughout the study. Dave Clew, Rick Kattelmann, and Kelly Elder provided invaluable humor and strength in many a cold snowpit. Jim Sickman, Mike Williams, and Helen Hardenbergh collected and analyzed water samples, Frank Setare developed our QA and QC protocol for snow chemistry analysis, and De!ores Lucero-Sickman and Frank Setare performed the chemistry analyses. Editing comments by John Stoddard and an anonymous reviewer substantially improved the manuscript. Funding was provided by California Air Resources Board contracts A3-103-32, A6-•47-32, and A3-096-32, and an NSF Pre-doctoral Fellowship.
An ionic pulse in meltwater with initial concentrations twofoldto twelvefold greater than the snowpack average,
REFERENCES
varyingwith site and with ion, was measuredin lysimeters Bales, R., Modeling in-pack chemicaltransformations,in Processes
placed at the baseof the snowpack.The Cm/('t,ratio is comparable to that froin snowpackswhere the initial bulk concentrations were as much as thirtyfold higher than tit the
ELW. This relationshipsuggests that the C.,/C/, ratit>in
o.f Chemical Change in Seasonal Snowcovers,NA TO ASI Set'. C, edited by T. D. Davies, H. G. Jones,and M. Tranter, D. Reidel, Hingham, Mass., in press, 1991. Bales, R. C., R. E. Davis, and D. A. Stanley, Ion elution through shallow homogeneoussnow, Water Reseat. Res., 25, 1869-1878,
meltwatermay be independentof the bulk ionic concentra1989. tionof the snowpack. Berg, N., Snow chemistryin the central SierraNevada, California, Soluteconcentrations in meltwater were higher when the rate of snowmelt decreased. A series of melt-freeze cycles,
which occurred after the initiation of snowpack runoff, increased the concentration of solutes in meltwater relative
Water Air Soil Pollut., 30, 1015-1021, !986.
Brimblecombe, P., M. Tranter, P. W. Abrahams, I. Blackwood, T. D. Davies, and C. E. Vincent, Relocation and preferential elution of acidic solute through the snowpackof a small, remote highaltitude Scottish catchment, Ann. Glaciol., 7, 141-147, 1985. Brown, A.D., L. J. Lund, and M. A. Lueking, Integrated soil
to concentrationsin meltwater prior to the melt-fi'eeze processes studiesat EmeraldLake watershed,final report,Concycles.Hydrogenconcentrationin meltwaterwas buffered byANC producedin part by the dissolutionof particulates. trib. A5-204-32, Calif. Air Resour. Board, Sacramento, 1990. Cadle, S. H., andJ. M. Dasch,Compositionof snowmeltand runoff Ourresultsindicate that tinions were preferentially eluted in northernMichigan,Atmos. Environ., 21,295, 1987. fromthe snowpack,in the order SOg > N O.•....> CI . Cadle, S. H., J. M. Dasch, and N. E. Grossnickle,Retentionand
Sulfateand NO3 concentrations in meltwaterdecreased releaseof chemicalspeciesby a Northern Michigansnowpack, below the initial bulk concentrations atter about 30% of the
snowpack had melted, while CI- concentrationsremained
elevated abovebulk snowpackconcentrations after 30% of thesnowpackhad melted. Solute concentrations in the meltwater of the basin varied
spatia!ly by a factor of 10or moreat a pointin time. The time spanof the ionicpulsein meltwater,at a point, decreasedas the rate of snowmelt increased. At a site with a relatively
Water Air Soil Pol!ut., 22,303-319,
1984.
Cadle, S. H., J. M. Dasch, and R. V. Kopple, Compositionof snowmelt and runoff in northern Michigan, Environ. Sci. Technol., 21,295-299, 1987.
Clew, D., Geologiccontrolson the neutralizationof aciddeposition and on the chemical evolution of surface and ground waters in the Emerald Lake watershed,SequoiaNational Park, California, M.
S. thesis,Dep. of Geol., Calif. State Univ., Fresno, 1987. Colbeck, S.C., A stimulationof the enrichmentof atmospheric
pollutantsin snowcoverrunoff,WaterResour.Res., 17, 1383-
1388, I981. rapidrateof snowmeltthe ionicpulselastedabout2 days;at Preferential a sitewith a relativelyslowrate of snowmeltthe ionicpulse Davies,T. D., C. E. Vincent,and P. Brimblecombe, elutionof strongacidsfrom a Norwegianice cap, Nature, 300, lasted about10 days.Temporaldifferences in the initiation 161-163, 1982. andmagnitudeof snowmeltwithin the ELW causeda spatial Dickson,W., Propertiesof acidifiedwaters,in Proceedings of the
difference in theNO• andSO42-concentration of streams
InternationalConferenceon EcologicalImpact of Acid Precipi-
tation, editedby D. Drablosand A. Tollan, pp. 75-83, SNSF flowing into EmeraldLake. project, Grefslie TrykkeriALS, Mysen,Norway,1980. Theartionicpulsein meltwaterwas observedin stream Dozier,J.,Johs. J. M. Melack,D. Marks,K. Elder,R. Kattelmann, and watersduringthe first 30 days of snowpackrunoff. Strong M. Williams,Snowdeposition,me!t, runoff,andchemistryin a acid artion concentrations then decreased below winter smallalpinewatershed, EmeraldLake Basin,Sequoia National Park,FinalReport,Centrib.A3-106-32, Calif.Air Resour.Board, concentrations in 1986 but remain elevated in 1987 due to Sacramento, 1987. inputs fromspring precipitation. TheANC minimaduring Dozier, J., J. M. Melack,K. Elder,R. Kattelmann, D. Marks,and
snowpack runoff was primarily due to dilution. However,
theincrease in Caof surface watersduringthefirstpartof snowpackrunoff also resulted in a decrease in alkalinity that
wasnot associatedwith a decreasein Co.
M. Williams,Snow,snowmelt,rain, runoff,andchemistry in a SierraNevadawatershed,finalreport,Centrib.A6-147-32,Calif. Air Resour. Board, Sacramento, 1989.
Drever,J. I., andD. R. Hurcomb, Neutralization of atmospheric
15814
WIi. LIAMSANI) Mt:;tA('K: Cttt•MIS'I'RY½)I,SN•)WM!?.I,IANt) Rt•NOF•,
acidity by chemicalweatheringin an airinc basinin the North (;aseaaleMountains,Geology,14, 221-224, I986. Elder, K., J. Dozier, and J. Michaelsen, Snow accumt•lationand
distributionin an alpine watershed,Water Resour. Rc.s.,this issue.
Galloway, J. N., G. R. Hendrey, C. L. Scholield,N, E. Peters,and A. H. Johannes, Processesand causesof lake acidification during spring snowmelt in the west-central Adirondack Mountains, New
York, Can. J. Fixh. Aquat. Sci., 44, 1595-!602. t987. Hornbeck, J. W., G. E. Likens, and J. S. Eaton, Seasonalpatterns
in acidity of precipitationand their implicationsfor foreststream
Rundel,P, W.. 13.tterman,W. Berry,andT. W. St. John, Integrated watershed study:vegetation process studies, vol.3, finalreport.(5'rotrib.A6-081-32, Calif.Air Resour.Board,Sacra. mento, 198•).
Sickman, J. ()., andJ. M. Mehtck,Characterization of year-round sensitivity of Catitbrnia's montane lakesto acidicdeposition, final report, Contrih. A5•203.32,(Yalif. Air Resour. Board,Sacra. mento, 1989.
Sisson,'i'. W., and J. G. Moore, Geologyof the Giant Forest.
Lodgepole area,Sequoia National Park,CA, U. S. Geol.Surv.,
Open t"i!c Rep. 84-254, 1984.
ecosystems, Water Air Soil Pollut., 7, 355-365, 1977. Skartveit,A., and K. •I'. (•jessing,Chemicalbudgetsandchemical Huntington, G. L., and M. Akeson, Pedologicinvestigations in quality(>fsnowandrunoffduringspringsnowmelt, NordHydrol., I0, 141-!54, 1979. supportof acid rain studies,SequoiaNationalPark,CA, technical report, Dep. of Land, Air and Water Resour., Univ. of Calif., Stoddard, J. I•., Alkalinitydynamics in an unaciditied alpinelake, Davis, 1986. SierraNevada,Calitk•rnia, LitnnoI.Oceanogr.,32,825-839,1987. 0f jett?ies, D. S., C. M. Cox, and P. J. Dillon, DepressionofpH in Strickland, J. I)., and T. R. Parsons, A practical handbook seawateranalysis,Bull. t:Zs'hRes. Board Can., 167, 83, 1972. lakes and streams in central Ontario during snowmelt,J. t.'iah. Res. Board Can., 36, 64(•46, 1979. Tonnessen,K., The timeraid l.,ake watershed study: Introduction and site description, W, tt.,rResottr. Rc.v., this issue. Johannessen, M., and A. Henriken, Chemistryof snowmeltwater: (?hangesin concentrationduringmelting, Water Resour.Res., 14, Tranter. M.. P. Brimblecombe,'I'. i). !)avies, C. E. Vincent,P.W. 615419,
I978.
Abrahams,and I. Blackwood,The compositionof snowfall,
Jones, H. (3., and W. Sochanska, The chemical characteristics of
snow cover in a northern boreal R•rest during the springrunoff period, Ann. Ghu'io[., 7, 17•176,
I985.
Kattelmann, R., (}roundwalercontributionsin an alpinehasinin the Sierra Nevada, Proceedingsqf the Headwaterstlydrology Sympoxit.tilt,pp. 361-369, American Water ResourcesAssociation, Bethesda, Md, 1989. l,anders, D. H., eta!., Characteristics of lakes in the western United
snowpeak, and meltwater in lhc Scottish Highlands•Evidence fin' prcl•rential elutkm, Att?lo3'.Etlvirtm., 20, 517-525, i986. '!YahtOt,M., 'I*. D. l)avics, t•. W. Abrahams, i. Blackwood,P. Brimblccombc, and ('. E. Vincent, Spatial wtriability in the chemicalc{•mpositionof sn'{•wc{>ver in tt small, remote,Scottish catchrncnl, Atmt•.,. Environ., 21,853..•862, 1987.
Tsiouris, S., ('. E. Vincent, T. I). !)avies, and P. Brimblecombe, The elution of kms lhrough tield and laboratory snowpacks,Ann.
Gh•citd., 7, i9t•2(11. 1985. States, EPA-600/3-86/O54a,U. S. Environ. Prof. Agency, Washington, I). C., 1987. Wcintraub,J., An a•cssment (ff the susceptibilityof two alpine watersheds to surfi.tce water acidification' Sierra Nevada, Calif0r. I.oranger, T. J., and D. F. Brakke, The extent of snowpack influenceon water chemistry in a north Cascadesi.,ake, Water nia. M.S. thesis, 186 pp., Indiana Univ., Bloonfinglon,1986. Rt,a'ottr. Res., 24, 723-726, 1988. Williams, M. W., and J. M. Melack, !.;tl•ct.sof spatial and temporal Melack, J. M., and J. I.... Stoddard, Sierra Nevada, Calit•>rnia, in variation in sm•w melt •m nitrate and sulfate pulsesin melt waters within an alpine hasin, Aftft. (;hu'iol,, i3,285•.289, 1989. Acidic'Depoxition and Aqttatic Ecosystems,Regional ('use Stttdies, edited by D. F. Charles, Springer-Verlag,New York, 1991. Williams, M. W., atld J. M. Melack, Precipitationchemistryinand kmic l{utdingt• an alpine basin, Sierra Nevada, Water Resour. Melack, J. M., J. !,. Stoddard,and C. A. Ochs, Mttjor ion chemistry Rt,,•., this issue. and sensitivityto acid precipitationof SierraNevadalakes,Water Res(mr. Res,, 21, 27-32, 1985.
Melack, J. M., S.C. Cooper, T. M. Jenkins,Jr., I,. Barmuta,S. Hamilton, K. Kratz, j. Sickman, and C, Soiseth, Chemica! and
biologicalcharacteristicsof Emerald Lake and the streamsin its watershed, and the responseof the lake and streamsto acidic deposition, final report, Contrib. A6-184-32, Calif. Air Resour.
J. M. Melack and M. W. Williams, (?enterfor RemoteSensing and Environmental()pries, [Iniversity of Cali12;n'nia, Santa Barbara,CA 93 t()6.
Board, Sacramento, 1989.
Murphy, A., Effects of insolubleparticulateson meltwater in the snowpackat Mammoth Mountain, Calit•rnia, Discovery,Univ. of Calif,, Santa Barbara, 1990.
I Received February 2, 199()' revised September 1, 1990; accepted December 19, 1990.
