Anewapproachtomonitoringspatialdistributionanddyna

AnewapproachtomonitoringspatialdistributionanddynamicsofwetlandsandassociatedflowsofAustralianGreatArtesianBasinspringsusingQuickBirdsatelliteimageryDavinaC.White⇑,MeganM.LewisSchoolofEarthandEnvironmentalSciences,TheUniversityofAdelaide,Adelaide5064,AustraliaarticleinfoArticlehistory:Received11March2011Receivedinrevisedform28May2011Accepted23July2011Availableonline29July2011ThismanuscriptwashandledbyKonstantineP.Georgakakos,Editor-in-Chief,withtheassistanceofV.Lakshmi,AssociateEditorKeywords:GreatArtesianBasinspringsMoundspringsWetlandvegetationRemotesensingTemporaldynamicsQuickBirdsatelliteimagerysummaryThisstudydevelopsanexpedientdigitalmappingtechniqueusingVeryHighResolutionsatelliteimagerytomonitorthetemporalresponseofpermanentwetlandvegetationtochangesinspringflowratesfromtheAustralianGreatArtesianBasinatDalhousieSpringsComplex,SouthAustralia.ThreeepochsofQuickBirdsatellitemultispectralimageryacquiredbetween2006and2010wereanalysedusingtheNor-malisedDifferenceVegetationIndex(NDVI).Aregressionof2009NDVIvaluesagainstvegetationcoverfromfieldbotanicalsurveyplotsprovidedarelationshipofincreasingNDVIwithincreasedvegetationcover(R2=0.86;p0.001).Onthebasisofthisrelationshipavegetationthresholdwasdetermined(NDVIP0.35),whichdiscriminatedperennialandephemeralwetlandvegetationfromsurroundingdry-landvegetationintheimagery.TheextentofwetlandsfortheentireDalhousieSpringsComplexmappedfromtheimageryincreasedfrom607hainDecember2006to913hainMay2009and1285hainMay2010.ComparisonofthethreeNDVIimagesshowedconsiderablelocalisedchangeinwetlandvegetationgreenness,distributionandextentinresponsetofires,alienvegetationremoval,rainfallandfluctuationsinspringflow.Astrongdirectrelationship(R2=0.99;p0.001)wasexhibitedbetweenspringflowrateandtheareaofassociatedwetlandvegetationforeightindividualsprings.Thisrelationshipstronglyinfersthatwetlandareaisanindicatorofspringflowandcanbeusedformonitoringpurposes.Thismethodhasthepotentialtodeterminethesensitivityofspringwetlandvegetationextentanddistribu-tiontoassociatedchangesinspringflowratesduetolandmanagementandaquiferextractions.Further-more,thisapproachistimelyandprovidesreliableandrepeatablemonitoring,particularlyneededgiventheprojectedincreaseddemandforgroundwaterextractionsfromtheGABforminingoperations.CrownCopyright2011PublishedbyElsevierB.V.Allrightsreserved.1.IntroductionTheAustralianGreatArtesianBasin(GAB)isoneofthelargestartesianbasinsintheworld,containinganestimated64,900,000GLofwaterwithinaconfinedaquifer.TheGABunderliesapproxi-mately1.76millionkm2(22%)oftheAustraliancontinent,encom-passinganumberofstatesandterritories(Queensland,NewSouthWales,SouthAustraliaandtheNorthernTerritory)(Gotchetal.,2006).TheGABsupportsauniqueanddiverserangeofwetlandecosystemstermedGABsprings,formerlyknownasmoundsprings,whichcontainanumberofrareandrelicendemicfloraandfauna(FenshamandFairfax,2003;Framenauetal.,2006;Got-chetal.,2008;Ponder,2004).TheGABspringsareofgreatnationalandinternationalimportancefortheirecological,scientificandeconomicvalues,andareculturallysignificanttoindigenousAustralians(AhChee,2002).TheyalsoprovideavitalsourceofwaterinthearidinlandheartofAustralia(Badmanetal.,1996;Boyd,1990;Mudd,2000).TheGABspringsareconsideredthreatenedecosystemsandanumberoftheirendangeredplantandanimalspeciesareprotectedbyAustraliannationalenviron-mentalprotectionandconservationlegislation.InrecentdecadestheecologicalsustainabilityofthespringshasbecomeuncertainasdemandsontheGABforthispreciouswaterresourceincrease.Theeco-hydrogeologicalimpactsofexistingwaterextractionsforminingandpastoralactivities,alongwiththeirlanduseimpactsareunknown.Thissituationisfurthercompoundedbythelikeli-hoodoffutureincreasingdemandforextractions,particularlyfromproposedminingandpetroleumactivities.DespitetheimportanceoftheGABsprings,fewhavebeendoc-umentedintermsofwaterflowsorwetlandvegetationextentandcomposition:accurate,repeatableandcost-effectivemethodsforinventoryandmonitoringarerequiredfortheseremoteandspa-tiallydispersedecosystems.Previousmappingandmonitoringofwetlandvegetationassociatedwithselectedmoundspringsin0022-1694/$-seefrontmatterCrownCopyright2011PublishedbyElsevierB.V.Allrightsreserved.doi:10.1016/j.jhydrol.2011.07.032⇑Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](D.C.White).JournalofHydrology408(2011)140–152ContentslistsavailableatSciVerseScienceDirectJournalofHydrologyjournalhomepage:fica-tionofaerialphotography,combinedwithconsiderablefieldwork(BHPBilliton,2009).WilliamsandHolmes,(1978)developedamethodofestimatingdischargefromspringsattheDalhousieSpringsComplex(DSC)usingaerialphotography,currentmeterandbucketandstop-watchmeasurements.However,theseap-proachesaretimeconsumingandsitespecific,andalsoparticu-larlylimitingfordiscriminatingwetlandfromdrylandvegetation.Theadvancementinremotesensingtechnologiesmeansthatmap-pingandmonitoringusingsatelliteimageryisnowachievableandcosteffective.Are