report summary: slave river - environment and … and suspended sediment quality in the...

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The Slave River is a culturally important waterway for Northerners with development activity upstream. This report summarizes 35 years of water quality data from the Slave River. The assessment revealed some long term trends in water quality parameters such as phosphorus and sulphate, as well as some long term trends in flow. The ecological significance of these trends needs to be better understood. This assessment also highlighted the need for site-specific water quality objectives to be able to better assess future water quality conditions of the river. Overall, fewer organic compounds, and at lower levels, were found in the water and suspended sediment samples taken during the Follow-Up Study (2000-2010) than in the earlier Slave River Environmental Quality Monitoring Program (1990-1995).

To ensure the health of the river, monitoring will continue. All partners should work closely together to expand the knowledge and understanding of the Slave River aquatic ecosystem.

The Slave River at Fort Smith

Slave RiverWater and Suspended Sediment Quality in the Transboundary Reach of the Slave River, Northwest Territories

Report Summary:

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Water and Suspended Sediment Quality in the Transboundary Reach of the Slave River

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QS-Y376-000-EE-A1 Catalogue: R3-174/2012E ISBN: 978-1-100-21539-6

© Minister of Aboriginal Affairs and Northern Development, 2012

Cette publication est aussi disponible en français sous le titre : Qualité de l’eau et des sédiments en suspension dans le tronçon transfrontalier de la rivière des Esclaves, dans les Territoires du Nord Ouest

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The Slave River…• isthelargesttransboundaryriverinthe

NorthwestTerritories;

• hasahugewatershedthatincludesthePeaceRiver,AthabascaRiver,LakeAthabascaandtheLowerSlaveRiversub-basins,whicharelocatedintheNorthwestTerritoriesandprovincesofAlberta,BritishColumbiaandSaskatchewan;

• isanimportantcomponentoftheMackenzieRiverBasin,contributingapproximately75%oftheinflowtoGreatSlaveLake;

• hasameanannualflowof3400m3/s,whichmeansthatonaverage3.4millionlitresofwaterpassbythecommunityofFortSmitheachsecond(asacomparison,theHayRiverhasameanannualflowof115m3/s);

• carriesanaverageof30milliontonnesofsuspendedsedimenttoGreatSlaveLakeeachyear,almostallofwhichisdepositedbetweenMayandOctober.Duringthesemonths,thisisequaltoabout4000largedumptruckloadseachday;and,

• supportsawidevarietyoffurbearers,fishandthemostnortherlycolonyofwhitepelicans.

The Slave River at Fort Smith

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Overthelastseveraldecades,resourcedevelopmentintheupstreamportionoftheSlaveRiverwatershedhasincreased.Theseactivitiesmainlyincludeoilandgasdevelopments;oilsandsoperations;pulpandpapermills;coalanduraniummining;agriculture;andforestry(Figure1).Further,theW.A.CBennettDam,ahydroelectricdevelopmentonthePeaceRiverinnorthernBritishColumbia,existsupstreamintheSlaveRiverwatershed.NorthernershaveraisedconcernsthattheseupstreamdevelopmentshaveimpactedthewaterresourcesintheNWT.TheseconcernsareespeciallyrelevantintheNorth,asmanyresidentsmaintainatraditionallifestyleandhaveacloseconnectiontotheland.Inaddition,climatechangehasthepotentialtoinfluencetheSlaveRiver.

Figure 1: Current activities in the Slave River watershed (not including specific oil and gas and oil sands operations)


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Purpose of the ReportAboriginalAffairsandNorthernDevelopmentCanada’s(AANDC)SlaveRiverreportdescribesthewaterandsuspendedsedimentconditionsintheriver.

UsinginformationfromAANDCandEnvironmentCanada,thereportaimsto:

• provideageneraloverviewofthecurrentstateofwaterquality,suspendedsedimentqualityandflowsinthetransboundaryreachoftheSlaveRiver;

• determineifwaterqualityandflowshavechangedovertime;

• helptoaddresscommunityconcernsaboutmetalsandorganiccompoundsintheriver;

• supportthedevelopmentofwaterqualityobjectivesforthetransboundarybilateralagreement;and,

• outlinepotentialareaswheretheexistingAANDCSlaveRivermonitoringprogramcanbeimproved.

Thereportisjustonepieceofthepuzzle.CombiningtheresultsfromthisstudywithinformationgeneratedfromotherSlaveRiverandSlaveRiverDeltamonitoringprogramsandresearchwillhelpnorthernersgainabetterunderstandingofthehealthoftheSlaveRiversystem.

The Slave River, near the Rapids of the Drowned

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Understanding Water QualityWaterqualitynaturallyvariesfromplacetoplace,withchangingseasons,climatevariationsandthetypesofsoilandrockthroughwhichthewatermoves.Watercancarryplantdebris,sand,siltandclay,makingthewatermuddyorcloudy(i.e.,measuredassuspendedsediments).Wateralsocarriesdissolvedmineralsandmetalsfromrocks,anddissolvedsaltssuchascalciumandmagnesium.Nutrientsinwatersuchasphosphorousandnitrogenareimportantforaquaticplants.Ingeneral,thesesubstancesarenotconsideredharmfultohumanoraquaticlife.

Waterqualitydescribesthechemical(e.g.,metalconcentrations),physical(e.g.,temperature)andbiologicalcharacteristics(e.g.,bacterialevels)ofwaterusuallywithrespecttoitssuitabilityforaparticularpurpose.Althoughscientificmeasurementsareusedtodescribethequalityofwater,itisnotasimplethingtosaythat“thiswaterisgood,”or“thiswaterisbad.”Forexample,waterthatisperfectlygoodtodrinkmightnotbegoodenoughforaverysensitivespeciesoffish.Whenapersonasksaboutwaterquality,theylikelywanttoknowifthewaterisgoodenoughtodrinkandswimin,orifthequalityofthewaterissuitableforaquaticplantsandanimals.

Guidelinesareestablishedtoprotectwaterforaquaticlifeordesignatedusessuchasdrinkingandrecreation.ComparingsubstancesfoundinwatertoguidelinesisonewaytodetermineiftheSlaveRiverwaterqualityis“good”.Goodwaterqualitygenerallymeansthatthelevelsofsubstancesarebelowtheguidelinevalues.ThedatafromthisstudywerecomparedtotheHealthCanada’sHealth-BasedGuidelinesforCanadianDrinkingWaterQualityandRecreationalWaterQuality,aswellastotheCanadianCouncilofMinistersoftheEnvironmentGuidelinesfortheprotectionoffreshwateraquaticlife.

Anotherwaytounderstandwaterqualityistocheckwhetherwaterqualityconditionshavechangedovertime.Changescouldbeduetohumanactivitiesand/ornaturaloccurrences.Thisstudylookedatwhetherwaterqualityhaschangedsince1972,whenregularsamplingbeganontheSlaveRiver.

Juanetta Sanderson, Erv Allen and Wayne Starling sampling the Slave River, September 2010.


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What were the Samples Tested for?Over200watersamplesand27suspendedsedimentsampleshavebeencollectedfromtheSlaveRiverandanalyzedforover500differentsubstances.

TounderstandthebasicchemistryofthewaterandsuspendedsedimentqualityoftheSlaveRiver,sampleswereregularlyanalyzedforroutineparameters(i.e.,pH,totaldissolvedsolids,totalsuspendedsolids,alkalinityandorganiccarbon),nutrients(i.e.,phosphorus)andmajorions(i.e.,calciumandmagnesium).

Tohelpaddressconcernsregardingupstreamactivities,waterandsuspendedsedimentsampleswerealsotestedformetalssuchasaluminum,arsenic,copper,lead,vanadiumandzinc,aswellascompoundssuchaschlorophenols,organochlorinepesticides,PCBs,dioxins,furansandhydrocarbons.Someofthesesubstancescanbenatural,butsomeareknowntobeassociatedwithupstreamdevelopment.

Why sample suspended sediments?

Due to the size and organic content of the suspended sediment in the Slave River, metals and organic compounds tend to attach to these particles and can be carried long distances from their source.

What are metals?

Metals, such as copper and lead, occur naturally, and most can be found in the rocks and soil in the NWT. Weathering of the rocks can release metals into rivers and lakes, therefore it is relatively common to find naturally occurring metals in surface waters. Some metals are required for all living things. However, some activities such as mining and other industrial developments, the burning of fossil fuels, land clearing and even forest fires can release higher than natural levels. These can be harmful to aquatic life.

What are chlorinated compounds?

Chlorinated compounds, more commonly known as persistent organic pollutants (POPs), are made by humans. Some are pesticides for killing insects or diseases that attack crops. Certain chlorinated compounds, such as chlorophenols, can be released from pulp and paper mills and municipal facilities. In the past, polychlorinated biphenyls or PCBs were used in electrical equipment. Dioxin and furans, another group of compounds, are released into the environment through combustion and wood pulp that is bleached with chlorine to produce paper products. POPs can cause harm to living things and last a long time in nature. Most POPs in the North arrive through air or water currents from other parts of Canada and the world.

What are hydrocarbons?

Hydrocarbons also referred to as polycyclic aromatic hydrocarbons (PAHs), are chemical compounds that are present in air, water and soil in small amounts virtually everywhere. Natural sources include forest fires, volcanic eruptions and natural petroleum and natural gas deposits. PAHs are also associated with industrial oil sands projects, other industries and urban runoff. These compounds can enter the river through effluent discharge, by air or runoff from the land. Hydrocarbons can cause harm to living things.

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What Data were used in the Report? Waterandsuspendedsedimentqualitydataforthisreportwereobtainedfromthreelong-termsamplingsiteslocatedontheSlaveRiver.Theseinclude:

• TheSlaveRiveratFortSmith(mid-river)samplingsiteledbyAANDC.Thisprogramiscomprisedoftwoparts:theSlaveRiverEnvironmentalQualityMonitoringProgram(SREQMP;1990-1995),andtheFollow-UpStudy(2000-2010).

• TheSlaveRiveratFortSmith(shore)samplingsitewhichhasbeenledbyAANDCsince1982.

• TheSlaveRiveratFitzgeraldsamplingsitewhichhasbeenledbyEnvironmentCanadasince1960.

Flowdatawereobtainedfromthehydrometric(flow)monitoringstationlocatedontheSlaveRiveratFitzgeraldwhichhasbeenoperatedbyEnvironmentCanada(WaterSurveyofCanada)since1960.

ThesefederalgovernmentmonitoringsiteswereestablishedtocharacterizethewaterqualityandquantityconditionsinthesectionoftheSlaveRiverneartheprovincial/territorialboundary.

So how is the Water Quality in the Slave River?TheSlaveRiverhasanaveragepHof7.9whichistypicaloffreshwaters.Therivercontainsmoderateamountsofdissolvedsolidsandisconsidered‘moderatelyhard’.Calciumandmagnesiumdissolvedinwaterarethetwomostcommonmineralsthatmakewater“hard.”Harderwatermeansthatyoumightneedmoresoaptomakealatherwhenwashingdishes.

Phosphorus,anessentialnutrientforthegrowthofaquaticplantsandalgae,playsanimportantroleintheoverallproductivityoffreshwaterecosystems(i.e.,numberoffish,aquaticanimals,etc.).TotalphosphoruslevelsintheSlaveRiverrangefrom0.006to4.67milligramsperlitre(mg/L).Asthemedianvalueoftotalphosphorusis0.1mg/L,theSlaveRiverisconsideredeutrophic(i.e.,highlevelsofnutrientsandplantgrowth,lowwaterclarity).AnalysisofSlaveRiverwaterdatarevealedanincreasingtrendinphosphorussince1974.Continuedsamplingandobservationsareimportanttoassessphosphoruslevelsgiventhatlandusershaveobservedmorealgaeontherocksandinfishingnets,anddenserwillowsandotherplantsaregrowingalongtheshore.

SulphateandsodiumconcentrationshavealsoincreasedintheSlaveRiverovertime,whiletotaldissolvedsolidslevelshavedecreased.Furtherworkisrequiredtodeterminetheecologicalsignificanceofthesetrends.Itisimportanttonotethatguidelinesforallroutineparameterswerenotexceeded.

Slave River shoreline


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TheSlaveRiverhashighlevelsofsuspendedsediment.Thisismainlyduetothefactthatitstwomajortributaries,theAthabascaandPeaceRivers,flowthroughtheInteriorPlains.Thisisanareathatisunderlainwithsedimentaryrocksandsoilsthatareeasilyerodedintolittlebitsthatgetcarriedbytheriver.SuspendedsedimentvaluesintheSlaveRiverrangefrom3to5600mg/L,withanaverageof240mg/L(Figure2).Inthisgraph,thesedimentloadsoftheSlaveRiverarecomparedtotwootherhighlysedimentladenriversintheNWT,thePeelandLiardRivers,aswellasone‘sediment-free’river,theYellowknifeRiver.TheYellowknifeRiverflowsprimarilythroughthebedrockofthePrecambrianShield;riversintheseregionsarerelativelyfreeofsediment.

Sedimentloadaffectsmetallevels.Riversthatcarrylargeamountsofsedimenttendtohavehigherlevelsofmetals.Thisisbecausemetalscanadsorb(i.e.,stick)tosedimentparticles(Figures3and4).ThehighlysedimentladenPeel,LiardandSlaveRivershavehigherlevelsofmetalsthantherelatively‘sediment-free’YellowknifeRiver.

Metalsinwaterexistinanumberofsoluble(i.e.,dissolved)andinsoluble(i.e.,attachedtoclaysororganicmatter)forms,withthedissolvedformbeingmoreavailableforuptakebyaquaticanimalsandfish.

ThedissolvedlevelsofmetalsintheSlaveRiverareconsiderablylowerthanthetotallevels(Figure5).

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Data Sources: Slave (n=210;); Liard(n=201); Peel(n=168) (1980-2010, Environment Canada); Yellowknife(n=228) (1987-2010, AANDC)

Figure 2: Comparing the Average Concentrations of Total Suspended Solids between the Slave, Peel, Liard and Yellowknife Rivers

Same water, one filtered, one not filtered.

Dissolved metal samples are filtered before analysis and include the metals in the water that you cannot see (similar to salt). Total metal samples are not filtered before analysis and include the dissolved metals as well as the metals that are attached to the suspended sediments.

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Data Sources: Slave, Liard, Peel (1980-2010, Environment Canada); Yellowknife (1987-2010, AANDC).Note: number in parentheses represents the total number of samples collected between the dates indicated; red dotted line represents the Guideline for the Protection of Aquatic Life for Total Iron; Total Aluminium currently does not have a guideline.

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Figure 3: Comparing Average Concentrations of Total Aluminum and Total Iron between the Slave, Peel, Liard and Yellowknife Rivers

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Data Sources: Slave, Liard, Peel (1980-2010, Environment Canada); Yellowknife (1987-2010, AANDC). The number in parentheses represents the total number of samples collected between the dates indicated; red dotted line represents the Guidelines for the Protection of Aquatic Life; note that the guidelines for copper and lead are corrected for water hardness (the guidelines were calculated based on average water hardness levels).

(102) (209)(211)(211)(25) (78) (147) (147) (136)(39) (186)(107) (186) (162)(176)(124) (186) (186) (220)(37)

Figure 4: Comparing Average Concentrations of Total Arsenic, Total Chromium, Total Copper, Total Lead and Total Vanadium between the Slave, Peel, Liard and Yellowknife Rivers


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1 Long term trends in metals were assessed for total aluminum, chromium, copper, iron, lead, manganese, molybdenum, nickel, vanadium and zinc, as these had an adequate dataset.

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Figure 5: Average Concentrations of Total and Dissolved Arsenic, Chromium, Lead, Aluminum and Iron from the Slave River at Fitzgerald (2006-2010, n=24)

MostmetalsintheSlaveRiverareattachedtothesuspendedsedimentssuggestingthattheyarelessavailabletoaquaticlife.

MetallevelsintheSlaveRiverwerecomparedtoguidelinesfortheprotectionofaquaticlife.Totalmetalssuchascadmium,chromium,copper,ironandleadwerehigherthantheirrespectiveaquaticlifeguidelinesmorethan25%ofthetime.Othertotalmetals,suchasarsenic,barium,manganese,nickel,selenium,silver,vanadiumandzincexceededtheirrespectiveaquaticlifeguidelineslessfrequently(lessthan25%ofthetime).Todate,totalmetalsincludingantimony,beryllium,cobalt,molybdenum,thalliumanduraniumhavenotexceededtheaquaticlifeguidelines.

Whenaguidelineisexceededitdoesnotnecessarilymeanthatthelevelsofmetalsareaconcernorthatanoutsidefactorisaffectingthewater.TheavailableguidelinestoassesswaterqualityintheNWTaregenericguidelines.Theseguidelinesaredevelopedforawiderangeofwaterqualityconditionsbutarenotnecessarilyspecifictolocalwaterqualityconditions.Forexample,iftheriverisnaturallyhighinmetals,thefishhavelikelyadaptedtothoseconditions.If,however,themetalsarehigherthannaturallevels,fishandaquaticlifecouldbeatrisk.Todetermineifthelevelsofmetalshavechangedovertheyears,thisstudyexaminedlongtermtrendsinmetalsovertime.Ofthe10metals1forwhichtrendswereassessed,onlymolybdenumshowedasignificantdecreasingtrendandonlyinthespring.Furtherstudyisrequiredtounderstandthesignificance,ifany,ofthistrend.

Insomecases,whengenericguidelinesareusedtoassessSlaveRiverwaterquality,theguidelinesareexceededasaresultofhighsedimentloads(e.g.duetometalsattachingtosuspendedsediment).Thisisillustratedwithtotalironlevelswhichrangefrom59to128,000microgramsperlitre(ug/L);over90%ofthevaluesexceedtheaquaticlifeguidelineof300ug/L(Figure6).Asthereisnolongtermtrendintotaliron,itislikelythattheironlevelsare

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normalandthatahigherwaterqualityobjectivemaybemoreappropriatetoassessironlevelsintheSlaveRiver.

However,metallevelsintheSlaveRiveraresometimesmuchlowerthanthegenericguideline.Thisscenarioisshownwithtotalarseniclevelswhichrangefrom0.3to15ug/L;withabout6%ofthevaluesexceedingtheaquaticlifeguidelineof5ug/L(Figure7).Insuchinstances,developmentofalowersite-specificwaterqualityobjectivemaybeappropriate.

Itisimportanttonotethatanalysisofthedataalsoidentifiedafewinstanceswherethedissolvedconcentrationofametalexceededthetotalmetalguideline(e.g.,cadmium,chromium,copperandiron).Itisimportanttokeepmonitoringandassessingthesemetalssinceitisthedissolvedformwhichisgenerallymoreavailabletofish.Toprovideadditionalinsightonthisobservation,trendanalysiswillbeconductedonceenoughdissolvedmetalsdatabecomesavailable.

When generic guidelines are used, they can sometimes be either over-protective or under-protective. This is the reason why site-specific water quality objectives are needed. These objectives would allow for a better assessment of the substances in the Slave River and provide a relevant set of benchmarks against which future data can be compared. Also, where generic guidelines do not currently exist for certain substances of concern (e.g., phosphorus), the development of site-specific water quality objectives would help to fill these gaps.

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Figure 6: Total Iron Concentrations in the Slave River (1980-2010)

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Figure 7: Total Arsenic Concentrations in the Slave River (1982-2010)


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Are there Persistent Organic Pollutants (POPs) in the Water or Suspended Sediments of the Slave River? TheSlaveRivermonitoringprogramsatFitzgeraldandFortSmithincludetheanalysisofwaterandsuspendedsedimentsamplesforhuman-madecontaminantssuchaspesticides,chlorophenols,dioxins,furansandPCBs.

Wherepossible,resultswerecomparedtoCCMEguidelinesfortheprotectionofaquaticlife.Guidelinesdonotexistforsuspendedsediment;thereforecomparisonsweremadetobottomsedimentguidelines.SuspendedsedimentscollectedfromtheSlaveRiverarecomposedmainlyofclayandsilt(fineparticles).Asbottomsedimentsalsocontaincoarseparticles,therearelimitationswhencomparingsuspendedsedimentvaluestobottomsediment.

Ofthe11pesticideswhichweredetectedinwatersamplescollectedfromFitzgerald,nineweredetectedonlyonce,andnonehavebeendetectedsince1986.Allvalueswerebelowguidelines.PesticideswerenotdetectedinthewaterorsuspendedsedimentatFortSmith,however,lowdetectionlimitswerenotalwaysavailable;futuremonitoringwithlowdetectionlimitswillprovideadditionalinsightintosampleresults.

SomechlorophenolcompoundsweredetectedatlowlevelsinboththewaterandsuspendedsedimentsamplescollectedfromtheSlaveRiveratFortSmithduringtheSREQMP(1990-1995).Allchlorophenolvaluesinwaterwerebelowguidelines(Note:therearenosedimentguidelinesforchlorophenols).NoneofthesecompoundsweredetectedintheSlaveRiveratFortSmithduringtheFollow-UpStudy(2000-2010).Thisapparentdecreaseinchlorophenolscouldbeduetothestricterlimitsforthepulpandpaperindustry,whichwereimposedbytheCanadianGovernmentinthe1990s.However,insomecasestheverylowdetectionlimitsobtainedduringtheearlierstudyarenotavailabletoday,sofurthermonitoringisrequiredtoconfirmthesefindings.

Slave River water and suspended sediment samples have been analyzed for contaminants that are known to be associated with upstream development. Overall, fewer organic compounds, and at lower levels, were found in the water and suspended sediment samples during the Follow-Up Study (2000-2010) than in the SREQMP (1990-1995). Monitoring will continue. Setting appropriate detection limits is important for future studies.

Pelicans below Rapids of the Drowned

It should be noted that for some organic parameters, detection limits were higher in the Follow-Up Study than the SREQMP. According to the laboratory used to analyze the organics in the river samples, the rules that govern laboratory reporting have changed. Laboratories must now report values with a much higher level of certainty than what was needed in the past. As such, the very low detection limits achieved during the SREQMP are not available today. In some cases, this makes comparison of results difficult, however, further monitoring will allow for trend analyses to be conducted which will help determine if trends are being observed.

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AfewdioxincompoundswerefoundinthesuspendedsedimentduringboththeSREQMPandFollow-UpStudyatlowlevelsandwellbelowanyavailableguidelines(Note:Dioxinsarenotmeasuredinwater).Levelsweresimilarduringbothstudyperiods.Thepresenceofthesecompoundscouldindicateatmosphericorpointsources.Onecompoundwhichhasbeenlinkedtopulpmilleffluent(2,3,7,8–TCDF)wasdetectedatlowerlevelsandlessfrequently(onlyonetime)duringtheFollow-UpStudy.Thisapparentdecreasecouldalsobelinkedtotheregulationchangesforpulpmills.Monitoringofthesecompoundswillcontinue.

PCBswerenotdetectedinanywatersamplesusingstandardtests.Ononeoccasion,whenverylowdetectionlimitswereused,PCBsweredetectedinthesuspendedsediment.Theobservedvalueswereextremelylow(800Xlessthantheguideline).

Hydrocarbons Hydrocarbonshavebothnaturalandhumanmadesources.PAHshavebeendetectedinboththewaterandsuspendedsedimentsamplescollectedfromtheSlaveRiver.

AllPAHcompoundsdetectedinwaterhavebeenatlevelswhicharelowerthantheaquaticlifeguidelines.SomePAHcompoundsinsuspendedsedimentexceededbottomsedimentguidelines.However,intheFollow-UpStudy,fewerPAHcompoundswereaboveguidelinesandtherangesofvaluesabovedetectionwerelower.Agoodexampleofthisisnaphthalene(Figure8),withconcentrationsrangingfrom10-580nanogramspergram(ng/g)duringtheSREQMPandfrom10-50ng/gduringtheFollow-UpStudy.

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CCME TEL Guideline(34.6 ng/g)

Figure 8: Comparing the Concentrations of Naphthalene in the Suspended Sediments of the Slave River between the SREQMP (1990-1995) and the Follow-Up (2000-2010)

A ng/g is one billionth of a gram or part per billion (ppb). To think of it in a different way, a ppb is like 1 second of about 32 years.


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Naphthaleneisahydrocarbonmadefromcrudeoilorcoaltar.Itisalsoproducedwhenthingsburnandisfoundincigarettesmoke,carexhaust,andsmokefromforestfires.Itisusedasaninsecticideandcanbefoundinmothballs.Whileitisimportanttocontinuetomonitorforparameterssuchasnaphthalene,whichseemtobepresentintheriverallthetime,itisalsoimportanttoensurethatmonitoringeffortsarefocussedonemergingPAHcompounds,suchasalkylatedPAHs,thathavebeenspecificallyassociatedwithupstreamactivities.Thesecompoundswereaddedtothemonitoringprogramin2007;andhavebeendetectedatlowlevelsinthetwosamplescollected.AlthoughtherearecurrentlynoCanadianguidelinesforalkylatedPAHs,theresultsfromthesampleswerewellbelowtheUnitedStatesEnvironmentalProtectionAgency(USEPA)benchmarkestablishedfortheprotectionofbottom-dwellingorganisms(bugs,worms,etc.).

Startingin2001,suspendedsedimentsampleswereanalyzedforanexpandedlistofPAHcompounds,whichallowedforcomparisontototalPAHguidelines2forbottomsediment.TotalPAHlevelsinSlaveRiversuspendedsedimentswerefoundtobeatleasttentimeslowerthanthisguideline,whichwasestablishedfortheprotectionofbottom-dwellingorganisms(Figure9).

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Figure 9: Total PAHs Concentrations in the Slave River Suspended Sediment Samples (2001-2010)

As there is no national guideline available for PAH, a comparison to the Ontario guideline is illustrated here. The levels in the Slave River suspended sediment samples are much lower than the Ontario total PAH bottom sediment guideline of 4000 ng/g established for the protection of bottom-dwelling organisms.

2 In the absence of a national guideline for total PAHs in bottom sediments, the Ontario guideline was used.

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Can I Drink the Water?InCanada,theresponsibilityformakingsuredrinkingwatersuppliesaresafeissharedbetweentheprovincial,territorial,federalandmunicipalgovernments.Theday-to-dayresponsibilityofprovidingsafedrinkingwatertothepublicgenerallyrestswiththeprovincesandterritories,whilemunicipalitiesusuallyoverseetheoperationsofthetreatmentfacilities.

Inconjunctionwiththeprovincesandterritories,HealthCanadadevelopedthe“Guidelines for Canadian Drinking Water Quality.”TheseguidelinesareusedbyeveryjurisdictioninCanadaandarethebasisforestablishingdrinkingwaterqualityrequirementsforallCanadians.

However,theseguidelinesareintendedtobeappliedtotreatedtapwater–notsourcewatersuchastheSlaveRiver.Since“CanIdrinkthewater?”isacommonandimportantquestion,theresultsoftheSlaveRiversurfacewatersamplingwerecomparedtoCanadiandrinkingwaterguidelinesasageneralassessmentofthiswaterfordrinking.Asexpected,duetothehighsedimentloadsoftheSlaveRiver,totalmetalsdidnotalwaysmeettheguidelines.However,whenthemetalconcentrationsinthefilteredwatersample(dissolvedmetals)werecompared,thedrinkingwaterqualityguidelineswerealwaysmet.

AlthoughwatersintheCanadianoutdoorsaregenerallyofexcellentquality,peopleshouldalwaysbepreparedtoboilordisinfectalldrinkingwater.

Itisveryimportanttonotethatnosurfacewatercanbeguaranteedtobesafefordrinkingwithouttreatment.HealthCanadaandtheGovernmentoftheNorthwestTerritoriesrecommendheatastheoldest,safestandmosteffectivemethodofpurifyingwater.Bringthewatertoarollingboilforatleastoneminutetoremovebacteria.Ifthewateriscloudy,likeitisintheSlaveRiversometimes,itshouldbefilteredbeforeboiling.Filtrationofsourcewaterpriortodisinfectionwillprovideadditionalprotection.

The surface water of the Slave River is safe for drinking* and swimming.

* After filtering and boiling the water for at least one complete minute. Additional information on drinking water in the Canadian outdoors and/or information on drinking water sources in the NWT can be found at: http://www.hc-sc.gc.ca/ewh-semt/pubs/water-eau/outdoor-plein_air-eng.php and http://www.maca.gov.nt.ca/operations/water/homepage.asp.


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Slave River Flows

FlowintheSlaveRiverisgreatlyinfluencedbythePeaceRiver,whichcontributesabout60%oftheSlaveRiverflowvolume.BeforetheW.A.C.BennettDamwasbuilt,flowsintheSlaveRiverbegantodecreaseinthefall,reachedaminimuminthewinterundericeandthenpeakedinthespringduringandjustafterbreakup(Figure10).Whilethispatternisstillobserved,followingconstructionofthedam,thehydrographhasbeendampened,inthatthewinterflowsarehigherandpeakflowsarelower(Figure10).Infact,sinceflowregulation,flowsinthewinterhavebeenincreasedby75%,andflowsinthespringhavebeenreducedby20%.ItisimportanttonotethatthetotalamountofwaterflowingintotheNorthwestTerritorieshasnotchanged,justthetimingofwhenthewaterarrives.

OtherchangesintheflowoftheSlaveRiverhavebeenobserved.Forexample,highfreshetpeaksweregenerallyexperiencedinJunebeforedamconstruction,butarenowofteninMay(Figure11).Atrendtowardmorefrequentpeaksontheannualhydrographshasalsobeenidentifiedandsecondarypeaksnowappearinsomeyearsduringwinter.Thesechangesmaybeduetoflowregulation,oranincreaseinclimaticvariabilityinthewatershed.

In2010,recordlowwaterlevelswereexperiencedontheSlaveRiver,onGreatSlaveLakeandintheupperMackenzieRiver.ManyofthetributariestotheWillistonLakeReservoirbehindtheW.A.C.BennettDamalsoexperiencedrecordlowsthatyear.ThissuggeststhatthelowwaterlevelsintheNWTthatyearwerelikelyduetolowsnowpackandrainfallintheupperportionoftheSlaveRiverwatershed.

Thisreportalsoexaminedlongtermtrendsinflow.Inadditiontolookingatannualtrendsovertime,eachseasonwasexaminedseparately.Nosignificanttrendswerefoundduringthespringorovertheentireyear(Figure12aandb).However,significantdecreasingtrendswere

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Figure 10: Mean annual hydrographs of the Slave River at Fitzgerald for pre-dam (1960-1967) and post-dam (1972-2010) years (Water Survey of Canada – 07NB001). Adapted from MRBB, 2003.

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foundinthesummerandfallflows,andasignificantincreasingtrendwasfoundinwinterflows(Figure12c,dande).Inotherwords,itseemsasthoughtheamountofwaterduringthesummerandfallflows,andasignificantincreasingtrendwasfoundinwinterflows(Figure12).Inotherwords,itseemsasthoughtheamountofwaterduringthesummerandfallaregettingprogressivelylowereachyear.Additionally,theamountofwaterinthewinterappearstobeincreasingeachyear.Thesetrendsmaybeduetoflowregulation,butmayalsobeduetoclimatechangeinthewatershed.Furtherstudyisrequiredtounderstandtheecologicalsignificanceofthesetrends.

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Figure 11: Examples of annual hydrographs of the Slave River at Fitzgerald for a pre-dam (1967) and a post-dam (2007) year (Water Survey of Canada – 07NB001).

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Figure 12a: Medians of 1972-2010 annual and seasonal Slave River daily flows at Fitzgerald (WSC Hydat, 2010). Solid lines indicate 95% confidence in the trend; dashed lines indicate trends with less than 95% confidence.


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Figure 12b: Medians of 1972-2010 annual and seasonal Slave River daily flows at Fitzgerald (WSC Hydat, 2010). Solid lines indicate 95% confidence in the trend; dashed lines indicate trends with less than 95% confidence.

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Figure 12c: Medians of 1972-2010 annual and seasonal Slave River daily flows at Fitzgerald (WSC Hydat, 2010). Solid lines indicate 95% confidence in the trend; dashed lines indicate trends with less than 95% confidence.

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Figure 12d: Medians of 1972-2010 annual and seasonal Slave River daily flows at Fitzgerald (WSC Hydat, 2010). Solid lines indicate 95% confidence in the trend; dashed lines indicate trends with less than 95% confidence.

Figure 12e: Medians of 1972-2010 annual and seasonal Slave River daily flows at Fitzgerald (WSC Hydat, 2010). Solid lines indicate 95% confidence in the trend; dashed lines indicate trends with less than 95% confidence.


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Changes in Water Quality due to Changes in FlowWaterqualityandquantityareverycloselylinked.Innaturalunregulatedrivers,dissolvedsubstancesaretypicallyhigherduringthewinterbecausealargerpercentageofwatercomesfromgroundwaterinflows.IntheSlaveRiver,however,thispatternisnotobserved.Manyofthedissolvedsubstances(totaldissolvedsolids,potassium,sulphate,fluoride,dissolvedorganiccarbon,phosphorus)havehigherconcentrationsinthespringandsummer,thaninthewinter.AnexampleisshowninFigure13.Forotherdissolvedsubstances(specificconductance,alkalinity,calcium,magnesium,sodium,hardness,ammonia),concentrationsintheSlaveRiverweresimilaramongseasons.AnexampleisshowninFigure14.ThesechangesmaybelinkedtothealteredflowregimeoftheSlaveRiverduetoupstreamflowregulationofthePeaceRiver;higherobservedwinterflows,themixingeffectsofLakeAthabascaandWillistonLake;and/orthepotentialinfluenceofclimatechange.

Fortotaldissolvedsolids,alkalinityandhardness,thisseasonalpatternofhigherlevelsinthespringandsummerascomparedtothewinterappearstobeoccurringasfardownstreamasthemouthoftheSlaveRiver(i.e.justupstreamofGreatSlaveLake).

Furtherstudyisberequiredtodetermineiftheseseasonalchangesinwaterquality,whichcanbelinkedtochangesinquantity,arehavinganyecologicaleffectsontheSlaveRiveraquaticecosystem.

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For the purposes of this illustration, lows flows constitute the TDS values reported for the months of January and February, whereas high flows constitute the months of May and June (Data Source: 1993-2010; Environment Canada).

Box and Whisker Plot: upper /lower whisker = maximum/minimum values; coloured section of boxes represents 50% of the data; the median value is represented by the horizontal lline and the average is represented by the asterisk.

Figure 13: Comparing the Levels of Dissolving Solids during Periods of High Flow and Low Flow between the Slave, Peel and Liard Rivers

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Slave River upstream of Fitzgerald


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Comparing Alkalinity Levels during Periods of High Flow and Low Flow between the Slave, Peel and Liard Rivers

For the purposes of this illustration, lows flows constitute the alkalinity values reported for the months of January and February, w hereas high flows constitute the months of May and June (Data Source: 1980-2010; Environment Canada).

Box and Whisker Plot: upper /lower whisker = maximum/minimum values; coloured section of boxes represents 50% of the data; the median value is represented by the horizontal lline and the average is represented by the asterisk.

Figure 14: Comparing Alkalinity Levels during Periods of High Flow and Low Flow between the Slave, Peel and Liard Rivers

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What happens next? InconjunctionwiththeEnvironmentCanadamonitoringprogramsatFitzgerald,theAANDCmonitoringprogramatFortSmithprovidesalargeamountofdatafromtheSlaveRiver.Theseprogramsarecriticaltobetterunderstandchangesintheaquaticenvironmentandformthebasisofmanydifferentresearchandmonitoringinitiatives.

AANDCiscontinuingtocarryouttheSlaveRivermonitoringprogramthroughthecollectionofwaterandsuspendedsedimentsamples.TheDepartmentwillworkwithEnvironmentCanadatoassessSlaveRiverwaterqualityandquantitydatawhennewdatabecomeavailable.

TheDepartmentwillalsocontinuetobeactivewithinotherregionalmonitoringinitiatives,suchastheSlaveRiverandDeltaPartnership.Thispartnership,consistingofmembersfromAboriginal,federalandterritorialgovernments,AuroraCollegeandcommunitiesalongtheSlaveRiver,hasresultedinseveralinitiatives.Theseincludecommunity-basedmonitoringworkshops,SlaveRiverDeltasedimentsamplingandtheSlaveRiverfishsamplingprogram.Underthisinitiative,passivesamplershavebeenrecentlydeployed

intheSlave,AthabascaandPeaceRivers.Thesesamplersremainintheriverforuptoonemonthandwillbeanalyzedforpersistentorganicpollutantsandmetals.Inadditiontotheseefforts,Environment

CanadahasimplementedanexpandedoilsandsmonitoringprogramthatincludestheSlaveRiverandSlaveRiverDelta.Collaboratively,theseresearchandmonitoringinitiativeswillsupporteachothertoexpandtheknowledgeandunderstandingoftheSlaveRiveraquaticecosystem.

Overall,theSlaveRiverreportprovidesanoverviewofthedatacollectedinpastyears.Monitoringwillcontinueand,wherepossible,improvementstothemonitoringprogramwillbemade.IncorporatingadditionaldataandinformationwillhelpassessanyenvironmentalchangeintheSlaveRiverovertime.Itisimportantthatallmonitoringprogramsattempttocollectdatainaconsistentmanner.Consistentdatacollectionandsharing,includingacrossjurisdictions,canbeextremelyusefulasitwillallowformorethoroughwaterqualityassessmentsandprovideabetterunderstandingofchangeinthewatershed.

Fort Smith Community Workshop, March 2011

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Formoreinformation,pleasecontactJuanettaSanderson(867-669-2653)orAndreaCzarnecki(867-669-2509)withtheWaterResourcesDivisionof

AboriginalAffairsandNorthernDevelopmentCanada.

http://www.aandc.gc.ca/eng/1100100022930/1100100022931

November2012

Continued monitoring by water partners is important to ensure the health of the Slave River

in the Northwest Territories.

report summary: slave river - environment and … and suspended sediment quality in the...

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