Lake Okeechobee: Current and Future Management Challenges Lake Okeechobee: Current and Future Management Challenges Paul V. McCormick, R. Thomas James, & Susan Gray Watershed Management Department, South Florida Water Management District Paul V. McCormick, R. Thomas James, & Susan Gray Watershed Management Department, South Florida Water Management District
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Lake Okeechobee: Current and Future Management ChallengesLake Okeechobee: Current and Future Management ChallengesPaul V. McCormick, R. Thomas James, & Susan GrayWatershed Management Department, South Florida Water Management District
Paul V. McCormick, R. Thomas James, & Susan GrayWatershed Management Department, South Florida Water Management District
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Lake Okeechobee – A RegionalMultipurpose Water ResourceLake Okeechobee – A RegionalMultipurpose Water Resource
Lake Uses:
Water SupplyFlood ProtectionNavigationFishingRecreationWildlife
33
Lake Okeechobee – The PastLake Okeechobee – The Past
44
Lake Okeechobee – The PresentLake Okeechobee – The Present
55
Rehabilitation, NOT RestorationRehabilitation, NOT Restoration
Extent of landscape change precludes true restorationRehabilitate lake to:• prevent water-quality impairments• improve in-lake biological conditions
• submerged and emergent vegetation • fisheries• wading birds• endangered species
Lake improvements benefit downstream ecosystems
66
Three Critical IssuesThree Critical Issues
Extreme Water Levels
Excessive Phosphorus Loads
Exotic Species
77
Year1970 1980 1990 2000
Lake
Sta
ge (f
t. N
GVD
)
8
10
12
14
16
18
20
Historic vs. Desirable Lake StagesHistoric vs. Desirable Lake Stages
88
Impacts of Extreme High Water LevelsImpacts of Extreme High Water Levels
Poor nearshore water qualityLoss of submerged vegetation (SAV)Stressed emergent vegetationAccumulation of organic bermAlgal blooms
Pelagic
Near-shore
Littoral
99
1010
Impacts of Extreme Low Water LevelsImpacts of Extreme Low Water Levels
Negative Impacts:Loss of littoral zone habitatLoss of key fauna Increased spread of exotic plants
Positive Impacts:Regeneration of emergent plant speciesOxidation, burning, and removal of accumulated detritusImproved control of exotic plants
1111
Water Level Extremes – SolutionWater Level Extremes – Solution
Options:Surface-water reservoirsAquifer Storage and Recovery (ASR)Private lands
Alternative storage for ~ 1 million acre-ft of water
1212
Phosphorus Loads and Concentrations:Historical TrendsPhosphorus Loads and Concentrations:Historical Trends
1970 1980 1990 2000 2010
Ann
ual T
P Lo
ad (m
t)
0
200
400
600
800
1000
1200
1400
TMDL
1970 1980 1990 2000 2010Cum
ulat
ive
Sedi
men
t Loa
d (m
t)
0
2000
4000
6000
8000
10000
12000
1970 1980 1990 2000 2010
Prop
ortio
n of
Lak
e M
ass
to S
edim
ents
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
1970 1980 1990 2000 2010
In-L
ake
TP (p
pb)
0
50
100
150
200
250
Target
1313
Phosphorus ImpactsPhosphorus Impacts
Increased in-Lake P concentrations and lower N:P ratiosIncreased frequency of cyanobacterial bloomsLoss of benthic invertebrate biodiversityExpansion of cattail in the lake’s wetlandIncreased P export downstream
1414
Phosphorus ControlPhosphorus Control
Lake Okeechobee TMDL• in-lake TP = 40 ppb• algal bloom frequency < 5%• External load = 140 mt P/yr
Watershed P Control ProgramsChallenges:• Legacy P
• 176,000 mt• ~50% potentially mobile
• Internal P Loading• 35,000 mt sediment P• Internal P load ~ external load
1515
Exotic Species – Success StoriesExotic Species – Success Stories
1616
Exotic Species – Success StoriesExotic Species – Success Stories
1717
Exotic Species – New InvadersExotic Species – New Invaders
The South American watergrass, Luziola subintegra
Welcome to south Florida!
1818
Exotic Animals – A Source of Concern?Exotic Animals – A Source of Concern?
Development and implementation of watershed P-reduction programs• Dairy buy-outs and remediation• BMPs• Dairy BATs
Critical construction projects (STAs)Control of exotic vegetationImprovements to Lake Regulation Schedule
2020
Performance Measures – A “Report Card”Performance Measures – A “Report Card”
25,602 acres>40,000 acresSAV cover
Not consistentlyattained
~15.5’ in Jan to~12.5’ in June
Spring recession
4.8% of samples<5% of samplesAlgal Bloom Frequency
114 ppb40 ppbNearshore TP
184 ppb40 ppbPelagic TP
558 mt/yr140 mt/yr(by 2015)
TP Load
WY’04-’08 AverageGoal
Performance Measure
2121
Future ChallengesFuture Challenges
Alternatives for water storage Achieve TMDL by 2015Sediment managementPopulation growth and urbanizationMaintaining a long-term commitment Confronting uncertainty and surprise