Lake Simcoe-the Need for Major Reductions in Phosphorus Loading - Aquatic Science Section-stb Bulletin No.aqss-3

10 Pages·1996·0.22 MB·English

by  Ontario Ministry of the Environment

Ontario
MINISTRY OF ENVIRONMENT AND ENERGY
SCIENCE AND TECHNOLOGY BRANCH
AQUATIC SCIENCE SECTION
STBTechnicalBulletinNo.AqSS-3
April 1996
LAKE SIMCOE THE NEED FOR
-
MAJOR REDUCTIONS
IN
PHOSPHORUS LOADING
B
ackground
Dissolvedoxygeninthedeep-waterzonesofthelakearedepleted
W'llhasoirfaceareaof725km\LakeSimcoeisthelargestlakein to levels that are lethal to cold-water fish like lake trout, lake
south-central Ontario, exclusive ofthe Great Lakes. It is the whitelishandherrmg(Fig. 1). Spawningshoalsareco\eredwith
drinkingwatersourceforfourmunicipahtiesandreceivestreated algae(Fig.2). Thelakenolongersupportsaself-reproducinglake
wastewatersfrom 14 sewagetreatmentfacihties. Thelakeisa trout population. Lake trout and lake whitefish stocks are
th;rilefmoefntdhoeusploypuvlaaltuiaobuleofrOenstoaurricoe.;iAtpipsr\o\xituhuiantoenleyh$o5u0r'0smdirUi^i'oenfoirs mmaaisnstiavienaendnubaylstthoeckMinmgisoftnfmgoefrUNnagtsuroaflthReesseosuprecceises.through a
spent annuallyontourismandrecreationalactivitiesintheLake
Suncoebasin. Anestimatedonemillionauglcr-hoursperyearis
spentonthelake. LakeSimcoeandmam ofitsri\er\'alleysare Stn K42 LakeS
miportantnaturalheritagefeaturesintheOntariolandscape. A \
healthy Lake Simcoe contributes significantly to the Ontario
ccononi)' and the physical and spiritual health ofhundreds of 10
thousandsofpeople. ThehumanpopulationintheLakeSimcoe
basin has grown exponentially since the 1940s and the 1991
population of about 280.000 was tAvice as high as the 1971 ^ 20
population.
T 30
heProblem
40
As aresultofalonghiston. ofnutrientloadingtothelakefrom
agricultural activities and urbanization, water qualiU has
deterioratedappreciabh.Municipalwatertreatmentfacihtiesnow
experiencecloggmgoffiltersfromLake Smicoealgae. Turbid
waterandma.s.sesofdeadanddecomposing\egetationcharacterize
somepartsofthelakedunnglatesummerandfall.

T
heSulutiun
Ihc LSfiMS Programme released a comprehensive set of
recommendations for Phase II. for which Provincial Cabinet
endorsement was gi\en in Febniar> ol 1995. The (ioalofthe
LSEMSprogrammeLs"tore-establishanaturallyreproducing
coldwatcrfishcummunityinLakeSimcoc" 1herestorationof
\\alerquablyis\italtotheattammentofthisgoalandremainsthe
pnman objectiveofPhaseIIoftheLSEMSProgramme.
Basedonuifomiationstoredinthelakesedimentsonphosphorus
concentrations and mass sedmientation rates over tmie. a pre-
180()'sphosphonisloadingrateofabout32metrictonshasbeen
determined 1\m)independentapproachestoowgen-phosphonis
modelling ha\c hindcast an end-of-sunmier dissohed oxygen
concentrationofabout 8nig/1. forcirca 1800AD(i.e..optimal
laketrouthabitate\i.stedpreHuropcau"mvasion") Areduction
inphosphonisloadingofabout25"/owillberequu-edtoachie\ean
incrca.seuitliccnd-of-sunuuerdeep-\\ateroxygento5mg/Lfrom
present-da) concentrationsofoidy3-3.5mg/L(Fig.4).
Figure 2 Accumulation of algae on a Ministry of Natural
Resourcestrapnetafteroneweek'sexposureonaLakeSimcoe
laketroutspawningshoalinOctober 1995.
fhe principal cause of this deteriorated state is excessive
phosphorusloading,estunatedatabout 100metrictonsperyear
forthe late 1980s-early 1990s. Themostmiportantsourcesare
agriculture and urban runofl"(Fig. 3). Under Phase 1 ofthe
LSEMSProgramme(LakeSimcoeEnvironmentalManagement
Strategy).phosphonisloadingtothelakewasdecreasedb> about
14metrictons/yearthroughchangesinagriculturalpracticesand
improvedsewagetreatment. However, theeffectswerelargely 30 40 50 60 70 80 90 100 110 120
undonebycontinuedpopulationgrowlhandincreasedphosphorus
TotalPhosphorus Loading (metricT/year)
loadingfromurbanniuolT
Figure 4 Ihe predicted end-of-summer \olume-\\eighted
Phosphorus Sources for Lake Simcoe dissolvedoxygenconcentrations in thedeep-\\ater/one(18 m-
bottom)inl.akeSimcoeoverarangeofphosphonisloadingfrom
30 to 120metrictonsperyear. Thedashedandsohd linesare
independentpredictionsfromempuicalanddeterministicmodels,
HollandMarshInt Agr, respectively. Arrowsindicatethepresent-dayloaduigrate(100
(5%) TA).aprojectedloadingrateofabout73T/yrequiredtoachieve
anend-of-summer-dLs,soKedox\genconcentrationof5mg/1,.and
Livestock(manure) aliindca.stend-of-summerconcentrationofabout8mg/1.resultmg
(14%
fromapre-settlementloadingrateof32T/y
LSEMS isone ofOntano's Finest examplesofpartnershipsfor
Atmosphenc UrbanStormwater emironmental stewardship. The list of collaborators includes
OM.AJ-R.A.. MOIT;. MNR. LSRCA. the SOS AUiance. 17
Figure3 Themostimportantsourcesofphosphorusloadingto mimicipahtiesandmiui> farmers. Still,aftirtherreductionof25%
LakeSuncoedunngthelate 1980s-early 1990s inphosphorusloading\mIIbeditTicuIttoachie\eintheabsenceof
capitalmcentncprogranunessuchasC'URlJ.LandSleuardship

and OSCEPAP for which funding has ended. An important
objectiveofPhaseIIofLSHMSwillthereforebetofindnewways
ofpartneiingstakeholderandspecialinterestgroupsintheLake
Simcoebasinsothatmeasurableprogresscanbemadetowardsthe
25"'o reductioninphosphorus loadingo\erthefiveyeartermof
PhaseII.
ThemostficxiuenUyaskcxiquestionbythepublicis"...isthelake-
gettingbetter?...". Itispossibletoansweriliisquestionaslong
as assessmentsofwaterqualityandbiological communities are
continuingtogeneratetrenddata. Phosphonisloading-lakewater
qualityrelationshipshavebeencompUcatedbytherecentin\'asions
of black crappie, zebra mussels and the spiny water flea. A
thoaiughunderstandingofbiological/limnologicalinteractionswill
benecessaryforfutureinterpretationoftimeseriesdata. Atthe
\eryminimum,theAquaticScienceSection'sresponsibilitiesto
Phase II ofLSHMS will include refinement ofphosphonis and
relatedcontaminantloadingstoLakeSimcoeandmeasurementof
trendsinthelakeandinflowingstreamsandrivers.
F
urtfaerInformation
Province ofOntario and LSRCA. 1995. Lake Simcoe - Our
Waters.OurHeritage LakeSimcoeF.miroimientalManagement
.
Strategy'ImplementationProgram. SunmiaryofPhaseIProgress
and Recommendations for Phase II. Lake Simcoe Region
Conser\'ationAuthority.Newmarket.Ontario. 109p.
NichoIIs.K.H. 1995. ALimnologicalBasisforaLakeSimcoe
Phosphorus Loading Obiccti\e. LSHMS Technical Report
IMP.B.17. Lake Simcoe Region Consersation Authority.
Newmarket,Ontario. 118p.
Forfurtherinformation,contact:
K.Xicholh
Phone: [phone]
Fax: [phone]
Email: nicholke'aepo.gov.on.ca