2017-01-17 goomig-knox surface water management report 2016

Goomig-Knox

SurfaceWaterManagementReport2016

January2017

Goomig-Knox Surface Water Management Report 2016 2

SUMMARYANDKEYPOINTS 3

1.0 OVERVIEW 4

2.0 IRRIGATIONSEASON2016 4

2.1 WATERTOGOOMIG 42.2 ON-FARMWATERUSE 42.3 IRRIGATIONSYSTEMEFFICIENCY 5

3.0 SURFACEANDTAILWATERMONITORING 6

3.1 TAILWATERQUALITY2016 63.1.2ATRAZINE 73.1.3NITROGENANDPHOSPHORUS 83.1.4ECANDPH 93.2 DW1GAUGINGSTATION 93.3 BORDERCREEKGAUGINGSTATION 113.4 KEEPRIVERGAUGINGSTATION 12

4.0 FIRSTFLUSHANALYSIS 13

5.0 CONCLUSIONS 15

REFERENCES 16

Table1-WatersuppliedtoGoomig2016......................................................................................................................................4Table2-M2channels:expectedannualevaporationlosses.........................................................................................................5Table3-Distributionsummary.......................................................................................................................................................6Table4-DW1GSwaterquality2016............................................................................................................................................11Table5-DW1,BorderCreekandKeepRiverDilution1/9/2015-31/1/2016..............................................................................12Figure1-Atrazinedetectionintailwater2015..............................................................................................................................7Figure2-Atrazinedetectionintailwater2016..............................................................................................................................7Figure3-Nitrogenandphosphorusintailwater2015-2016.........................................................................................................8Figure4-BorderCreekFlowDataApril2016–January2017.....................................................................................................12Figure5-KeepRiverflowApril2016toJanuary2017.................................................................................................................13Figure6-Earlywetseason(firstflush)flowvolumes2016.........................................................................................................13Figure7-Nitrogenandphosphorusloadestimatesearlywetseason2016...............................................................................14Plate1-DW1GS.29September2016.........................................................................................................................................10Plate2-UpstreamviewofBorderCreekfromDW1GS.29September2016............................................................................10Plate3-'LakeChivers'-DW1/DW4intersection,upstreamofDW1GS.29September2016...................................................10


SummaryandkeypointsThis paper tabulates irrigation water use, tailwater management on the Goomig (Weaber Plain)farmlands,andKeepRiversurfacewatermonitoringundertakeninthedryseasonof2016.Itoutlinestheseasonalconditions,watermonitoringprogramresults (includingstoredtailwaterandtheKeepRiver),associatedriskassessmentsandmanagementresponses.Forannualreportingpurposes,thedocument includes reference to the monitoring requirements of the Knox Creek Plain approvals,howeverthedevelopmentoftheKnoxareahasnotyetcommenced.The results and analysis contained in this report cannot be statistically validated given the limitedsampledata.Nonetheless,thedataarebeingaccumulatedtoinformtheriskassessmentandongoingmanagementandmonitoringrequirements.Review of the actual and estimated data for Goomig tailwater, the Keep River and Border Creekindicatesthefollowing:

Ø FirstflowsthroughtheDW1gaugingstationinmid-November2016wereM2water,resultingfromchannelmaintenance(ie,nottailwaterorstormwater).

Ø ‘Firstflush’oftailwatercanbeconsideredtohaveoccurredonandafter22November2016.Ø Atrazineconcentrations inGoomigwaterwerenota risk toaquatic faunaafter July/August

2016,dilutedorotherwise,withlevelsbelowthe99%ANZECCtrigger(0.7ug/L).Ø N&PloadsinstormwateroriginatingfromtheGoomigfarmlandsareproportionatelyhigher

thanthoseoriginatingonpastoralland,andwillcontinuetobemonitored.Ø RemotemonitoringofflowsintheDW1drain,throughtheDW1gaugingstation,andremote

sampling,continuestoberestrictedbytelecommunicationsissues.Ø Collationof actual data from theGoomig farmlands and theKeepRiverpools continues to

informmanagementresponses.Ø Turbidityanalysisistobefurtherconsideredforwetseasonflows,basedonanincreasingset

ofdata(whenaccessispossible).


1.0 OverviewThis paper summarises irrigationwater use, tailwatermanagement on the Goomig (Weaber Plain)farmlands,andKeepRiversurfacewatermonitoringundertakeninthedryseasonof2016.Itoutlinestheseasonalconditions,watermonitoringprogramresults (includingstoredtailwaterandtheKeepRiver),associatedriskassessmentsandmanagementresponses.Forannualreportingpurposes,thedocument includes reference to the monitoring requirements of the Knox Creek Plain approvals,howeverthedevelopmentoftheKnoxareahasnotyetcommenced.Thesurfacewatermanagementandmonitoringrequirementsassociatedwiththefollowingapprovalsareaddressedherewith:

• WesternAustralianEnvironmentalProtectionAct1986(EPAct)approvalknownasStatement938,relatingtotheGoomig(WeaberPlain)andKnoxCreekPlainareas.

• Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)approvals2010/5491relatingtotheGoomigdevelopment,and2014/7143fortheKnoxCreekPlain.

• Western Australian Rights in Water and Irrigation Act 1914 (RiWI Act) water licenceSWL179228,notingthatKimberleyAgriculturalInvestment(KAI)doesnotyethavetenureforthe Goomig farmlands, and thus is not able to obtain irrigation water under this licence.Instead,KAI ispurchasingwater fromOrdStage1until tenurecanberesolvedandKAIcanirrigateunderitsownlicence.Nonetheless,theannualreportingrequirementsofSWL179228areincludedinthispaper.

2.0 IrrigationSeason2016The2016irrigationseasoncommencedontheGoomigfarmlandsinApril2016.Combinedlots3/5and14/17/18wereirrigatedduringtheseason,withoperationaltailwaterreturnfacilitiesestablishedforeach.

2.1 WatertoGoomigSuppliedvolumestotheGoomig farmlands,asmeasuredbyOrd IrrigationCooperative (OIC)at theM2C3structure(neartheD4drain)wereasfollows:Table1-WatersuppliedtoGoomig2016

MONTH(2016)

MEGALITRESSUPPLIED

NOTES

April 1,441 May 2,817 June 2,324 July 3,413 August 3,046 September 364 October 173 November 746 (includes539.6MLWaterCorporationchannelre-fill,November2016) 14,324 TotalsuppliedbyOICthroughM2C3forGoomigirrigation

Source:OIC,December2016

2.2 On-farmwateruseAtotalof8,248.8ML(~8.25GL)wereappliedtolots3,5,14,17and18overtheperiod1April2016to30September2016. Thisequates to58%ofwatersuppliedbyOIC (excludingWaterCorporation’s


channelre-fillinNovember).UnderSWL179228,thetargetdistributionefficiency,onceallfarmsareirrigated,is90%.

2.3 IrrigationsystemefficiencyOperational losseswhichaffect theefficiencyof the irrigation systemaremadeupof anumberofcomponents:

Ø EvaporationlossesØ SeepagelossesØ MeteringinaccuracyØ ChanneldraininglossesØ OverflowsfromshutdowneventsØ Channeloperationaloverflows

(Sunwater,2011)The distribution efficiency is defined in the SWL179228 Goomig Operating Strategy as the ratiobetweenthevolumepassingthroughtheM2C3structure,andthecollectivemeteredflowontofarms–which,asdescribedabove,was58%duringthe2016irrigationseason.The42%distributionlossescanbelargelyattributedtothefactthatapproximatelyonethirdoftheGoomigfarmareawasirrigated.However,theseepageandevaporationlossesoccurringwithinthesupplyinfrastructure(ie,thechannels)willberelativelyconstantacrossallseasons,regardlessofthearea irrigated. This consequently affects thedistribution efficiency, as the ratio of evaporation andseepagelosseswilldeclineastheareaofirrigatedcropsincreases.ThisissuewasnotedintheoriginalPhase2(Goomig)designconsiderations(Sunwater,2011).Evaporationlosses,assumingthechannelisfull,wereestimatedduringtheengineeringdesignprogramasfollows:Table2-M2channels:expectedannualevaporationlosses

ChannelSection SurfaceArea(ha) EvaporationLoss(ML)

M2channel(M2C3toM2S1) 31 930M2Schannel 26 780M2Nchannel 18 540 TOTAL 2,250

Source:Sunwater2011

SeepagelossesfortheGoomigchannelsareestimatedat2mm/dayoratotalof1,100MLperannum,TheconstructionofchannelssizedforthefullM2development–includingtheKnoxCreekPlainandtheKeepRiverPlain–hasresultedinhigherthannormalchannelevaporationandseepageratesforadevelopmentthesizeofGoomig.Thisalsocontributestotheseeminglylow58%distributionefficiencyatcurrentscale. Assuch, thedistributionefficiencywill improvewith increasedareaof landunderirrigation.Furtherlossescanbeattributedtometeringaccuracy,calculatedat+/-2%(atotalofapproximately164ML),539.6MLforWaterCorporationinNovember,andupto500MLincludedinApril2016M2C3volumes,forthepurposeoffillingsupplychannels(pers.comm.,OIC,2016).Aminorchanneloverflowoccurredaround21/22June2016,resultinginpoolingattheDW1GaugingStation.Thus, total losses from evaporation, seepage, channel filling and metering inaccuracy equate toapproximately4,014MLforthe2016dryseason,or32%ofsuppliedwater.Thisvolumeoflosses(4GL)shouldremainrelativelystableovertime,astheareairrigatedfromthesupplychannelsincreases.


Theremaining1,521ML(or11%)wasutilisedforconstructionpurposes–ie,dustsuppressionduringconstructionofadjoiningfarms–andformaintainingwaterlevelsinminorchannels(M2NandM2S1)toavoidstructuraldamagetothesechannels.Table3-Distributionsummary

GoomigWaterDistribution ML %Totalsuppliedtofarmlots 8,248.8 58%WaterCorporationchannelre-fillNovember2016 539.6 4%Totallossesfromevaporation,seepageandmeteringaccuracy 4,014 28%Constructionwater,dustsuppression,minorchannelre-fills 1,521.6 11%TotalsuppliedbyOICthroughM2C3 14,324 100%

3.0 Surfaceandtailwatermonitoring

3.1 Tailwaterquality2016Under the commitments given by the Proponent for environmental approvals on the Goomigfarmlands,andascontainedinrelatedapprovals,tailwateristoberetainedonfarmsduringthedryseason.Tailwaterrecyclingfacilitieshavebeenconstructedandareoperationalonlots14/17/18and3/5.Tailwaterquality ismonitoredregularlythroughoutthedryseasonto identifypatternsofchange inrelationtokeyanalytes.Inparticular,totalnitrogen(N),totalphosphorus(P),electricalconductivity(EC), pH and Atrazine are monitored. Pre-emergent herbicide Atrazine has been adopted as theindicator chemical for the Goomig farmlands due to its residual nature and annual use at thecommencementofeachdryseason.Tailwatersamplesaretakenfromdrainagewaterfromeachlotunderirrigation,aswellasfromOrdStage 1 water originating from the area immediately south of the Goomig development, knowncollectivelyas‘Pacseeds’,whichisheldadjacenttoKAI’sfarmingoperations.KAI ismonitoring tailwater over the dry season each year, in order to determine trends aswell asconcentrationsofthekeyanalytes.Notingthattherearenowaterqualitytriggersorstandardsforwaterheldonfarm,KAImonitorsforitsownrecordsandtoassistinriskcalculationinrelationtowaterqualityintheKeepRiver.IntheeventofeitheradryseasonflowtotheKeepRiver(veryunlikely)orrainfallresultinginstormwaterflowstotheKeepRiver,KAIseekstobeinapositiontocalculatelikelydownstreamdilutionandtodetermineappropriatemanagementresponses.UnderthetermsofapprovalEPBC2010/5491fortheGoomigdevelopment,anOperationalSurfaceWaterModel(OSWM)isrequired,forthepurposesofcalculatingdownstreamriskintheeventofaflow. In lieuof thecomplexOSWMdeveloped for theGoomig farmlands,KAI isusingactualwaterquality and flow data to assess downstream risk to listed Matters of National EnvironmentalSignificance(MNES)intheKeepRiver–thatis,sawtoothsharks.


3.1.2AtrazineThemaximumlimitforAtrazineintheKeepRiver,inlinewiththeANZECC/ARMCANZ99%standard,is0.7ug/L.KAItestsforAtrazinepresenceinitstailwaterasanindicatorofoverallchemicalpresence,duetotheresidualnatureofthisherbicideanditstoxicitytoaquaticfauna.Figures1and2showthedetectedAtrazineconcentrationsintailwatersamplestakenonGoomiglotsandfromOrdStage1(Pacseeds)tailwaterin2015and2016respectively.Figure1-Atrazinedetectionintailwater2015

Notethe6ug/Lmaximumdetectionin2015wasfoundinOrdStage1tailwater,whichhasanallowable13ug/Lconcentrationcomparedtothe0.7ug/LKeepRiverlimitforwateroriginatingontheGoomigfarmlands. Note also that the concentration of Atrazine inOrd Stage 1 tailwater had degraded to0.3ug/L by October 2015. This rate of degradation (under Kimberley conditions) is important forconsiderationsrelatingtoKeepRiverwaterqualityrisk.Similardegradationwasidentifiedin2016:Figure2-Atrazinedetectionintailwater2016

Aswiththe2015dryseason,detectedhigh(5-8ug/L)concentrationsofAtrazineintailwaterduringthefirsthalfoftheseasondegradedtobelowminimumrisklevels(<0.7ug/L)bytheendofAugust.This

01234567

26/05/2015 15/07/2015 3/09/2015 23/10/2015 12/12/2015 31/01/2016

Atrazine

ug/L

Atrazinedetec0on-GoomigandOrdStage1Pacseeds2015DrySeason

ATRAZINE

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

8.5

30/5/2016 19/6/2016 9/7/2016 29/7/2016 18/8/2016 7/9/2016 27/9/2016 17/10/2016

Atrazine

ug/L

Atrazinedetec0on-GoomigandOrdStage1Pacseeds2016DrySeason

ATRAZINE


againdemonstratesnaturaldegradationprocessesinrelationtothemostresidualofherbicidesandpesticidescurrentlyusedinKAI’sfarms.Theanalysisof2015and2016dryseasonAtrazineconcentrationsintailwatershowsthatbytheendofAugustinbothseasons,Atrazineconcentrationswerebelowthe0.7ug/LlimitallowableintheKeepRiver.ThismeansthatiftailwaterflowedundilutedtotheKeepRiverattheendofthedryseason,andwas undiluted in the river, it would not pose a risk to 99% of aquatic organisms (per theANZECC/ARMCANZguidelines)andnotbreachenvironmentalconditionsbasedonAtrazinealone.

3.1.3NitrogenandPhosphorusAswithAtrazine,therearenotargetsortriggersfornitrogenandphosphorusintailwaterheldon-farm.KAImonitorsforTotalNandtotalPinordertoinformriskassessmentintheeventthataflowtotheKeepRiveroccurred.Figure3depictsresults fromsampleanalysisacrossGoomigtailwaterandtheadjacentOrdStage1tailwater,forthe2015and2016seasons.UppertriggersfordryseasonconcentrationsofNandPintheKeepRiver(K3)poolare0.69mg/Land0.039mg/Lrespectively. ShouldaflowtotheKeepRiveroccurinthedryseason,thesefiguresarethemaximumdilutedconcentrationsoftotalNandtotalPwhichtriggerflushingrequirements.Figure3-Nitrogenandphosphorusintailwater2015-2016

AscanbeseeninFigure3,totalNandtotalPconcentrationsintailwaterrisemid-season,butbegintodeclinetowardstheendofthedryseason.Withoutstormwaterflowdilution,NandPconcentrationscouldpotentiallyposearisk,shouldtheretainedtailwatermeettheKeepRiverinalowflowperiod.Flushing(withM2channelwater)wouldberequired.NitrogenandphosphorusloadsareestimatedinSection4.0.

00.050.1

0.150.20.250.30.350.40.450.5

0.550.60.650.7

0.750.8

0.850.9

0.951

1.051.1

1.151.21.251.31.351.41.451.5

1.551.61.651.7

1.751.8

1.851.9

1.952

2.052.1

26/05/2015 15/07/2015 3/09/2015 23/10/2015 12/12/2015 31/01/2016 21/03/2016 10/05/2016 29/06/2016 18/08/2016 7/10/2016 26/11/2016

Concen

tra)

on-mg/L

SampleDate

TotalNandTotalP-GoomigandOrdStage1(Pacseeds)Tailwater2015-2016

TOTALN

TOTALP

Linear(TOTALN)

Linear(TOTALP)


3.1.4ECandpHTargetsalinity(electricalconductivity/EC)inalltailwatertestsarewellbelowKeepRiverK3triggers,withECrecordingsaveraging30-40mS/macrossalltestedsitesduringthedryseason,andloweroncewetseasonrainshadcommenced.KeepRiver(K3pool)dryseasontriggersforpHrangefrompH7.31(lowerlimit)topH9.11(upperlimit),withlowerandupperfocustriggersatpH7.7andpH8.2respectively.Thus,the‘ideal’rangeforpHfortheK3poolinthedryseasonisintherangeofpH7.7topH8.2.Aswithotheranalytes,therearenospecifictriggersfortailwater.However,thepHrangefortailwatersamplestakenoverthe2016dryseasonwaspH7.7topH8.7,withamodeofpH7.9andmeanofpH8.1.ThisrangeiswithintheallowableK3pool.IfaneattailwaterflowofvolumesufficienttoreachtheKeepRiverhadoccurredduringthedryseason,thepHwouldnothavebeenproblematicforaquaticfaunahealthintheriver.

3.2 DW1GaugingStationThe DW1 Gauging Station (DW1GS) is the stormwater flow metering point for the Goomigdevelopment.Forthemajorityofthe2016dryseason,andtothetimeofpreparationofthisreport (mid-January2017),telecommunicationsprovidingflowreportsfromtheDW1GSwerenotinoperation.Similarly,thetelecommunicationssystemoperatestheautomatedwatersamplerlocatedattheDW1GS,whichwasalsonotinoperationduringthistime.Asassetowner,theWAgovernmentisliaisingwithRubicon(assetbuilder)to(1)conductafullauditofallsitecommunications;and(2)undertaketherequiredrepairstothetelecommunicationstower(Tetra2orWooljimtower)toenabledatareportingfromtheDW1GS.KAIexpectstosignanassetmanagementagreementwiththeWAgovernmentinlate2016orearly2017,whichwillincludemaintenancearrangementsontelecommunicationsinfrastructure.Manualmonitoring of rainfallwithin the catchment of theDW1 drainage system, aswell as visualinspection of tailwater retention facilities to ensure no spillage, was undertaken on a daily basis.VerificationthroughthemonitoringofflowsatthedownstreamBorderCreekgaugingstationwasalsoundertaken(refertoSection3.3).


Plate1-DW1GS.29September2016

Plate2-UpstreamviewofBorderCreekfromDW1GS.29September2016

Plate3-'LakeChivers'-DW1/DW4intersection,upstreamofDW1GS.29September2016


Throughoutthedryseason,samplesofwaterpooledattheDW1GSwerecollectedandanalysedtoinformrisktotheKeepRiverintheeventthataflowoccurred.Table4-DW1GSwaterquality2016

Sampledate

21/6/16*

22/6/16*

5/9/16 K3pooldryseasonupperfocustrigger

10/11/16 22/11/16 23/11/16 15/12/16 K3poolwetseason

upperfocustrigger

EC 31.6 31.7 57.5 434 32 9.1 5.1 7.9 23

TotalN 0.5 0.45 2.5 0.39 0.52 1.1 1.6 1.6 0.5TotalP 0.044 0.027 0.22 0.013 0.024 0.29 0.16 0.1 0.038Turbidity 14 14 720 17 14 4700 8700 3100 190pH 8.2 8.2 7.9 8.2 8.2 7.9 7.7 7.9 8.06Atrazine <0.1 <0.1 <0.1 0.7 <0.1 <0.1 <0.1 <0.1 0.7 *M2Schanneloverflow

ExcludingflowarisingfromtheemptyingoftheM2Schannelfrom11November2016,the‘firstflush’canbeseentohaveoccurredonoraround22November2016(refertoSection3.3fordiscussion).Manual‘firstflush’samplestakenonNovember22and23,asreportedinTable4,indicatetotalNandtotalPinexcessoffocus(andactionandlimit)triggersfortheKeepRiverK3pool.TheseresultsneedtobeconsideredinrelationtofullKeepRiverflowsandpotentialdilution,andarediscussedfurtherinSection4.0.

3.3 BorderCreekGaugingStationLocateddownstreamoftheDW1GS,withintheNorthernTerritory,theBorderCreekGaugingStationprovides a supplementary source of flow data to verify information gathered at the DW1GS. ThisenablesverificationofDW1GSflowestimatesanddata.Figure4depictsBorderCreekflowfromApril2016untilJanuary2017.EarlydryseasonrainfallinMayresultedinaveryminorflow.RainfallalsooccurredinlateAugustbutnosubsequentflowwasrecorded(duetoinfiltration).From 10-16 November 2016, the Water Corporation engaged contractors to repair the M2SW5structureatthedownstreamendoftheM2Schannel.Duetothecommunicationsissuesassociatedwith theDW1GS also affecting other structures at the northern endof the development, accurateSCADAdatacannotbeprovidedfor thevolumeofwaterreleasedfromtheM2SW5or that flowingthroughtheDW1GS.CalculationofflowsthroughtheBorderCreekgaugeindicatesatotalof531MLflowing throughBorderCreekover theperiod11November2016 to21November2016 (NTDLRMGovernmentwaterdataportal).Asnotedearlier,basedonrainfalldata,firstflushcanbeconsideredtohaveoccurredon22November2016.AnalysisofNTDLRM(2016)detaileddataindicatesapproximately225MLtohaveflowedthroughBorderCreekbetween22November2016andthecessationofthefirstnaturalflowon12December2016.KAIobtainedwatersamplesfromtheDW1GSon22November,23Novemberand15December.KeepRiverpoolsampleswereobtainedon23Novemberand15December.


Figure4-BorderCreekFlowDataApril2016–January2017

MinorstormwaterflowcommencedatBorderCreekon22November2016(44MLx1day).Continuedstormwaterflowcommenced27November2016to9December2016–atotalof852MLover13days.FlowthroughBorderCreekre-commencedon19December,withaflowof215744MLover13daysto31December2016(or216GL).DuetothesaturationofBorderCreekpre-stormwaterflow(resultingfromtheM2channelreleaseinmid-November)andtheinabilitytoaccessDW1GSflowdataforthe2016-2017wetseason,percentagestormwatercontributionestimatesfrom2015,perTable5,willbeappliedtotheanalysiscontainedinSection4.0.Table5-DW1,BorderCreekandKeepRiverDilution1/9/2015-31/1/2016

GaugingStation TotalDischarge(ML) %ofBorderCreekVolume

%ofKeepRiverVolume

DW1GS 1,413 14.12% 1.27%BorderCreek 10,010 100.00% 9.02%KeepRiver 111,000 1108.89% 100.00%

Forthepurposeofthisassessmentandriskanalysis,itwillthusbeassumedthat,basedonthepreviousyears’actualdata,thecontributionoftheGoomigcatchmentarea(viatheDW1GS)is1.27%oftotalKeepRiverflowfollowingastormevent,withthewiderBorderCreekcatchmentcontributingatotalof9.02%offlows.ThisestimateisappliedinSection4.0

3.4 KeepRiverGaugingStationKeepRivergaugingstationflowdataispresentedinFigure5(source:NTDLRMwaterdataportal).FlowdatahasbeenutilisedtoestimateNandPloadsaspresentedinSection4.0.


Figure5-KeepRiverflowApril2016toJanuary2017

StormwaterflowthroughtheKeepRiverK4pooloccurredon22November(1dayflowonly;dischargetotal 432 cumecs or 0.43ML). Flow recommenced for a 13 day period from 27November until 9December,thenagainfrom19December.Atthetimeofpreparationofthisreport,theregionwasexperiencingabove-averagerainfallconditions,resultingincontinuedstormwaterinthroughtheKeepRiver.DilutionofstormwaterrunofffromtheGoomigfarmlandscontinues.

4.0 FirstflushanalysisAs previously noted, undiluted tailwater on the Goomig farmlands did not contain Atrazineconcentrations in excess of Keep River trigger levels, during the 2016 season. As such, the risk ofAtrazineharmtoaquaticfaunaintheKeepRiver,followingthefirstflush,isvirtuallynon-existent.WithoutexplicitflowdatafromtheDW1gaugingstation,proportionalvolumesderivedfromthe2015seasonhavebeenassumedtoapply for the2016season (seeFigure6). Notethat thecalculationscontainedwithinFigure7areindicativeonly,andarenotintendedtoreplacefullscientificanalysis.Figure6-Earlywetseason(firstflush)flowvolumes2016

Flowvolumes-earlywetseason(November-December2016) ML GL

TotalflowDW1GS22Nov2016-31Dec2016(estimate) 3122.12 3.12

TotalflowBorderCreek22Nov2016-31Dec2016(actual) 29240.18 29.24

TotalflowKeepRiver22Nov2016-31Dec2016(actual) 216596.25 216.60


Figure7-Nitrogenandphosphorusloadestimatesearlywetseason2016

2015equiv.

(seenote)

23/11/2016 Unit K3Pooluppertrigger

FirstFlushDW1waterquality-TotalN 1.7 1.6 mg/Lorkg/ML

0.55

FirstFlushDW1waterquality-TotalP 0.06 0.16 mg/Lorkg/ML

0.05

DW1volume22Nov2016to31Dec2016 1.41 2.75 GL

BorderCreekvolume(seenote)22Nov2016to31Dec2016

10.01 29.24 GL

Totalnon-tidalKeepRiverin-flow(KeepK4+BC)22Nov2016to31Dec2016

111.01 216.63 GL

GoomigNload(seeAssumption5) 2.4 4.4 tonnesN

GoomigPload(seeAssumption5) 0.09 0.44 tonnesP

TotalestimatedKeepRiverNload 61.06 119.14 tonnesN

TotalestimatedKeepRiverPload 5.55 10.83 tonnesP

%ofKeepRiverflowfromGoomig 1.27% 1.27% %ofKeepRiverNloadcomingfromGoomigin2015 3.93% 3.69% %ofKeepRiverPloadcomingfromGoomigin2015 1.63% 4.06% Redtext=actualBluetext=derived/extrapolated

Assumptions 1)K3Poolupperwetseasonlimittrigger(0.55mg/LtotalNand0.05mg/LP)usedtocalculateKeepRiverloadandBorderCreekloads.TherearenowaterqualitytriggersexplicitlyfortheDW1.

2)1.26GLofK4inflowissufficienttocompletelyflushtheKeepRiverPools(ref:Bathymetrystudies2014)3)Riskassessmentreliesonsufficientrainfall/runofftoflush1.26GLthroughKeepRiverPools,toreturntonaturallevels.4)121GLflowthroughK4andBorderCreekOct2015-Jan2016=100xflushingrequirementtoreturnKeepRiverpoolstonaturallevels.Poolshadreturnedtonormalqualityby6/1/2016.

5)AssumesNandPcontentoffirstflushisconsistentacrosssubsequentflows.Note:2015calculationsbasedonperiodtoendJanuary2016.

Asnotedearlier,ECandpHinGoomigtailwaterarenotconsideredtobeoutsideofacceptablerangesduringthedryseason,thusdilutedwetseasonstormwaterconcentrationsaretakentobeacceptable.The established wet season triggers for turbidity in the Keep River pools are considered to be aninaccuraterepresentationoftheactualwaterqualityinthewetseason.Itisassumedthisisduetothelimited number of wet season samples informing the triggers. Actual samples regularly indicatesignificantly higher turbidity readings than the existing triggers – caused by natural storm events.Ongoingdatacollection,whenwetseasonaccesstotheKeepRiverispossible,willoccur,inordertoinformfuturerevisionsoftriggersandanalysisGoomigstormwateraccordingly.


5.0 ConclusionsThe results and analysis contained in this report cannot be statistically validated given the limitedsampledata.Nonetheless,thedataarebeingaccumulatedtoinformtheriskassessmentandongoingmanagementandmonitoringrequirements.ReviewoftheactualandestimateddataforGoomigtailwater,theKeepRiverandBorderCreekindicatesthefollowing:

Ø FirstflowsthroughtheDW1gaugingstationinmid-November2016wereM2water,resultingfromchannelmaintenance(ie,nottailwaterorstormwater).

Ø ‘Firstflush’oftailwatercanbeconsideredtohaveoccurredonandafter22November2016.Ø Atrazineconcentrations inGoomigwaterwerenota risk toaquatic faunaafter July/August

2016,dilutedorotherwise,withlevelsbelowthe99%ANZECCtrigger(0.7ug/L).Ø N&PloadsinstormwateroriginatingfromtheGoomigfarmlandsareproportionatelyhigher

thanthoseoriginatingonpastoralland,andwillcontinuetobemonitored.Ø RemotemonitoringofflowsintheDW1drain,throughtheDW1gaugingstation,andremote

sampling,continuestoberestrictedbytelecommunicationsissues.Ø Collationof actual data from theGoomig farmlands and theKeepRiverpools continues to

informmanagementresponses.Ø Turbidityanalysisistobefurtherconsideredforwetseasonflows,basedonanincreasingset

ofdata(whenaccessispossible).

ThisreportiscomplementedbyKAI’ssurfacewaterdatabase,whichcanbeprovideduponrequest.


ReferencesKimberleyAgriculturalInvestmentPtyLtd,2014,Goomig-KnoxFarmAreasOperatingStrategy.PreparedasarequirementofwaterlicenceSWL179228,fortheDepartmentofWater,Kununurra.OrdIrrigationCooperative,2016,personalcommunicationfromMatDear,GeneralManager,toDebraPearceforKAI.NorthernTerritoryGovernmentWaterdataportal-https://nt.gov.au/environment/water/water-data-portal.SitesG8100106(BorderCreek)andG8100225(KeepRiver).Sunwater,2011,OperationalPhilosophyandBalancingStorageReview–PositionPaperPP015,containedinGHD,2011,Phase2DetailedDesignReport,preparedforLandCorp.

2017-01-17 goomig-knox surface water management report 2016

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