What's up with our lakes - Welcome to WCOLA€¦ · • What’s in the groundwater matters. Basic...
Transcript of What's up with our lakes - Welcome to WCOLA€¦ · • What’s in the groundwater matters. Basic...
What’supwithourlakes?JohnA.Downing
LifetimeSeasonalResidentofWabana COLMinnesotaSeaGrantProgram
Duluth&St.Paul
Sometopics
•Geology– whyourCOLexists•Oxygendemand- Whatwe’reseeingandwhatitmeans
•Algaeblooms-• Invasivespecies•Humanissues
Glaciersformedourlandscape
Whyourchainoflakesexists
Tall,graveleskerattheSWofTroutLake
ViewoftheeskeronBluewater
FlowtotheCOLfromtheeskergroundwatersystem• ViaTroutLakechannels:
• 1/4m/second(4mwidex0.5mdeep)• 1m3/sec• 100,000gallons/hour
• ViaBluewaterchannel• 0.15m3/sec(3mwidex0.5mdeep)• 15,000gallons/hour
• Closetothisyear-round– notmuchinfluencedbyrainfallandrunoff• What’sinthegroundwatermatters
Basic limnology: summer stratification
Deepwateroxygen– whyitmatters
• Troutandciscos need4mg/Ltoliveandreproduce• Alsoneedtobebelow52degreesF(11degreesC)• Andtheyreproduceinfall
• Otherfishcan’tlivebelow2mg/L• Oxygeninspringisaround12mg/L
Whatusesdissolvedoxygen?
• Startshighinspringbecauselakemixestoptobottomandtakesinoxygenfromtheair
• Normally,oxygenistakenoutofthewaterbydecompositionofstuffgrowinginthelake
• Algae,fueledbynutrientistheusualthingthatdecomposes• Chemicalprocessescanaddtoit• Eutrophicationfromhumannutrientsmakesitincreaseveryfast
• OxygendepletioninthedeepwateroftheCOLis5-10timesfasterthanweexpectforaclearwaterlake
9sitessincemid-May
Oxygenconditionsnow
• ManyplacesintheCOL,nofishcansurvivebelow30-40feet• DeepwaterinsouthTroutlowerinoxygenthannorthTrout• Fishinasandwichbetweenwarmwaterandlowoxygen– andit’sgettingworse(need>4mg/Loxygenand<52degreesF
• DeepwaterinnorthBluewaterlowerinoxygenthaninsouthBluewater
• Interlochen(aka“LittleTrout”)hasnooxygenbelowabout35feet–nevermixes
• We’retryingtofigureoutthesourceofphenomenonfortheseandother“CiscoLakes”soitcanbefixed
• Seemsasifgroundwaterisinvolved
Hasthischanged?
• Ratesofoxygen“demand”5-10xtheamountseeninotherclear-wter lakes• SurveysIdid15yearsagoshowedsomelowoxygenbutnotasmuch• Roleofclimateandnewnutrients?• MyancestorscaughttroutinWabana• Iusedtofinddeadciscoesontheshore• The“ciscolakeproblem”isoneofthebigmysteriesDNRistryingtosolve
(Springoxygen)-(naturaldemand)-(demandduetonewnutrients)-(chemicaldemand)=(Augustoxygen)
Algaeblooms–why?
Thisyear’sspringbloom
• Ourspringbloomwasabluegreen algaespecies• Wabana warmedfromicetoswimmablein3weeksbeforeMemorialDay
• Whenlakesmixinspring,nutrientsfromthedeepwaterareavailabletoalgae
• I’mseeingmorealgaeinthewaternowthanI’veseeninthepast• We’veseenalotofglobsoffilamentousalgaewehaven’tseeninthepast
• Climateandincreasednutrientsthelikelycauseofincreasedalgae
Whyshouldwecareaboutthis
• Somespeciescanbetoxictopeople,pets,andaquaticlife• Theycanstinkandaddodorandflavor• Theyareasignofdecliningwaterquality
Invasivespecies
Howdotheygethere
• Mostlybyaccidentaltransportbyboatsvialandings• 3officialboatlandingsonthechainoflakes• Watercraftinspectionsarehelpful• Boatsarriveoutofinspectionhoursandatunofficiallandings,too• Nearbylakeshaveavarietyofspecies
• Zebraandquaggamussels• Didymo• Spinywaterflea• Starrystonewort
• “Cures”notinnear-futureso“prevention”iskey
Lot’sofwaystoincreasesafetyfromAIS
Boat-inCampsites
Concernaboutsanitaryconditions
GrowingnumberofcampsitesontheChain
Concernsaboutboat-incampsites
• Untreatedwaste• Nutrients(50peopleforadayproducesewageof1personfor2months)• 50%ofphosphorusoutputisasurine• Disease-causingmicrobes(bacteria,viruses,otherpathogens)
• Bigpartiesanddrunkenboating• Firehazards• Litter• “commonproperty”resourceproblem- whenitbelongstoeveryone,wholooksafterit?
GrowingnumberofcampsitesontheChain
Navigationisgettingcomplicated
Safetyofpeopleandtheresourceisimportant• Right-of-wayrulesseemunknowntoboaters
• Motorizedyieldtounmotorized• Upstreamtrafficyieldstodownstream• Morecollisionsinchannelsanddestructivenavigation
• IsthisaroleforWCOLA?
Wildfireprotection&waterquality
• Clearing100’diametercircleis7854sq feet
• 1/5acreperhouse• Cleartotheshoreandnearlytheentirewidthofa250’lot
• Perhapssafeforhousesbutnotforthewater
WhatistheroleforWCOLAin….
• Insuringgoodwaterqualityandhealthyfisheries• Protectingthegroundwaterresourcethatsustainsour“chain”• Algaebloommonitoringandprotection• Aquaticinvasivespecies• Safeuseofcampsites• Safenavigation