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Home My WebLink AboutLakeCornelia_Edina_UseAttainabilityAnalysis_Dec2018Nine Mile Creek Watershed District and City of EdinaDecember 13, 2018Lake Cornelia and Lake Edina Water Quality Evaluation and Restoration Measures Using the Use Attainability Analysis (UAA) Process The Challenges (and opportunities) of Urban Shallow LakesNutrient Rich SedimentsCurly-leaf Pondweed (Invasive)FishWatershed Runoff Characteristics of a Well Functioning Shallow Lake that Promote Good Water QualityBalanced Fishery Characteristics of a Well Functioning Shallow Lake that Promote Good Water QualitySmall FishSource: Ohio DNRSource: WikipediaZooplanktonPhytoplanktoneatseatsSource: Wikipediatoo many small fish = fewer zooplankton = more phytoplankton Characteristics of a Well Functioning Shallow Lake that Promote Good Water QualityBig Fish! Winterkill Drives Fish Population Dynamics in Lake CorneliaSpeciesNumber of fish caught in each category (inches)Total Fish/Net0-56-8 9-11black bullhead1481611676 225black crappie---2---20.67bluegill sunfish31------31 10.3common carp1------10.33goldfish9---93golden shiner6323---9030green sunfish20------206.7hybrid sunfish12------124pumpkinseed12------124painted turtle---------165.3snapping turtle---------113.7North Cornelia Fish Survey Winterkill Drives Fish Population Dynamics in Lake CorneliaSpeciesNumber of fish caught in each category (inches)Total Fish/Net0-56-8 9-11black bullhead75821159 53bluegill sunfish1231goldfish16165.3golden shiner161175.7painted turtle113.7snapping turtle103.3South Cornelia Fish Survey Upstream Ponds Serve as Nurseriesgoldfishcarp Aquatic Plants•Habitat for zooplankton and aquatic insects•Habitat for fish•Reduces phosphorus concentration in the lake when it grows•Increases lake clarity•May hinder specific boating activitiesA balanced aquatic plant population provides… Lake CorneliaMostly invasive curly-leaf pondweed Lake Cornelia- aquatic plant cycle with invasive curly-leaf pondweed•Invasive Curly-leaf grows under the ice in the winter•Grows rapidly in the spring and crowds out the native (all other) species•Dies in June or early-July•Followed by a turbid lake•In summer, native species not available to pull phosphorus out of the lake water column and prevent phytoplankton blooms with shading Lake Edina aquatic plant populationAugust 2017 Phosphorus release from lake bottom sediments (“internal loading”) Phosphorus release from lake bottom sediments (“internal loading”)1 2 3 4 5 6 7 8 9 10 11 12summerfallwinterspringphosphorus releasephosphorus accumulattionaccumulatereleaseaccumulate Lake Cornelia and Lake EdinaPhosphorus in sedimentsLakeMaximum Potential Internal P Load (mg/m2/d)Kohlman117.0Isles (pre-alum, deep hole)214.1Harriett (pre-alum, deep hole)211.1Calhoun (pre-alum, deep)210.8Fish E310.5Cedar (pre-alum)29.3Fish W38.1Como37.6North Cornelia7.6Calhoun (pre-alum, shallow)35.6Keller13.5Parkers33.5Phalen32.3McCarrons32.0Bryant31.5South Cornelia1.3Nokomis31.0Minnewashta30.2Edina0.0Christmas30.0 Watershed Runoff Measuring the effects of management efforts through modeling•Step 1: Develop lake models that simulate current lake function−Years modeled: 2015, 2016, 2017•Step 2: Estimate the phosphorus sources for each lake−Direct watershed (impervious pavements in watershed)−Internal loads (curly-leaf pondweed, sediment, fish)−Upstream lakes−Atmospheric deposition and groundwater inflow•Step 3: Develop management strategies and use lake model to predict impacts on lake water quality North Cornelia- where is the phosphorus coming from?Direct WatershedCurly-leaf PondweedInternal Sediment LoadUpstream LakesAtmospheric Deposition South Cornelia- where is the phosphorus coming from?Direct WatershedCurly-leaf PondweedInternal Sediment LoadUpstream LakesAtmospheric Deposition Lake Edina- where is the phosphorus coming from?Direct WatershedCurly-leaf PondweedInternal Sediment LoadUpstream LakesAtmospheric Deposition Summary of Major Phosphorus Sources –Lake Cornelia•North Cornelia1.Direct Watershed2.Internal Loads (sediment release)3.Curly-leaf pondweed decay•South Cornelia1.Upstream Lakes = North Cornelia2.Curly-leaf pondweed decay3.Internal Loads (sediment release and fish)4.Direct Watershed Summary of Major Phosphorus Sources –Lake Edina•Lake Edina1.Upstream Lakes = North and South Cornelia2.Direct Watershed Management Scenarios: In-Lake Treatments•In-lake Management−Alum treatment(s) reduce internal sediment loading−Fish Management carp, goldfish, bullhead−Herbicide treatments reduce curly-leaf recruitment Alum Treatment Curly-leaf pondweed management Management Scenarios: External Management•External Management−Infiltration/Filtration Best Management Practices (BMPs)Commercial land (re-development or retrofits)Residential land (re-development or retrofits)Right-of-Way Public land (e.g., parks)−Optimizing treatment from existing BMPsImproving performance/treatment from stormwater ponds Management Scenarios: External Management•External Management−Community EffortsRoutine street sweeping (public and/or private)Increasing buffer zonesReductions of phosphorus-based fertilizers−Residential EffortsShoreline restoration, rainwater gardensFall leaf clean-up, adopt-a-drain programMow high Modeling Management Alternatives+++++Assess Lake Response of In-Lake ManagementAssess Lake Response of External Management How much management of external sources is enough?•Modeling Approach for External Load Reduction:−Create a range of treatment scenariosInfiltrate runoff on commercial propertiesInfiltrate runoff on commercial and residential propertiesInfiltrate runoff in right-of-way−Incorporate community efforts (i.e., street sweeping) -70.00-60.00-50.00-40.00-30.00-20.00-10.000.0010.0020.0030.000.000.050.100.150.200.250.300.350.400.450.504/1/17 5/1/17 6/1/17 7/1/17 8/1/17 8/31/17 10/1/17 10/31/17Total Phosphorus (mg/L)North Cornelia - Modeling Year 2017Modeled TPMeasured TPDirect WatershedModeling Example – North Cornelia•Step 1: Develop current conditions models•Step 2: Analyze the major loads -70.00-60.00-50.00-40.00-30.00-20.00-10.000.0010.0020.0030.000.000.050.100.150.200.250.300.350.400.450.504/1/17 5/1/17 6/1/17 7/1/17 8/1/17 8/31/17 10/1/17 10/31/17Total Phosphorus (mg/L)North Cornelia - Modeling Year 2017Modeled TPMeasured TPDirect WatershedModeling Example – North Cornelia•Step 1: Develop current conditions models•Step 2: Analyze the major loadsCurly-leafEnhanced Internal LoadDirect Watershed Modeling Example•Step 3: Develop proposed modeling strategies to assess various management efforts Modeling Example•Step 3: Develop proposed modeling strategies to assess various management efforts Modeling Example•Step 3: Develop proposed modeling strategies to assess various management efforts+ Modeling Example•Step 3: Develop proposed modeling strategies to assess various management efforts+Commercial Modeling Example+CommercialAdd in External Loading Management•Scenario 2: Infiltrate 1.1” of runoff from commercialimpervious surfaces where soils allow •Infiltrating from approximately 148 acres from commercial parcels in North Cornelia watershed•Total North Cornelia watershed area = 831 acres•Step 3: Develop proposed modeling strategies to assess various management efforts Modeling Example•Step 3: Develop proposed modeling strategies to assess various management efforts+Commercial Modeling Example•Step 3: Develop proposed modeling strategies to assess various management efforts++Commercial Modeling Example++Commercial Loadings to North Cornelia per Management Strategy North Cornelia-- Lake Response per Management StrategyLake Conditions (2017)Summer Average Total Phosphorus Concentration (µg/L)Current Conditions191Alum Treatment114Curly-leaf Treatment164Alum & Curly-leaf Treatments87External & Alum Treatment116External & Curly-leaf Treatment167External & Alum & Curly-leaf Treatment80MPCA Water Quality Goal60 Loadings to Lake Edina per Management StrategyNote: Alum and Curly-leaf treatments are in Lake Cornelia Lake Edina -- Lake Response per Management StrategyLake Conditions (2017)Summer Average Total Phosphorus Concentration (µg/L)Current Conditions99Alum Treatment85Curly-leaf Treatment75Alum & Curly-leaf Treatments61External & Alum Treatment70External & Curly-leaf Treatment62External & Alum & Curly-leaf Treatment54MPCA Water Quality Goal60 Potential management activities-North & South CorneliaAlum treatment of nutrient-rich sedimentsInvasive Curly-leaf pondweed managementExternal phosphorus load reductionFishery management Potential management activities –North & South CorneliaFishery management considerations•Evaluate best method to remove and manage rough fish•Restock fish population: bass, pike, sunfish, perch, etc.•Installation of oxygen injection system to prevent winterkill and maintain predation of young carp & goldfish•Fish barrier between North Lake Cornelia and upstream ponds (?) Potential management activities- Lake EdinaImprove water quality in upstream Lake CorneliaContinue to promote diverse native aquatic plant population External phosphorus load reduction The Challenges (and opportunities) of Urban Shallow LakesNutrient Rich SedimentsCurly-leaf Pondweed (Invasive)FishWatershed Runoff Questions?