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Benton Lake TMDL (Total Maximum Daily Load)

Benton Lake TMDL (Total Maximum Daily Load). Water Quality in a Shallow Lake January 22 nd , 2008. Objectives of this Presentation. What is a TMDL?? Overview of Shallow Lake Ecology Water Quality in Benton Lake Watershed Characteristics Water Quality Plant and Fish Communities

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Benton Lake TMDL (Total Maximum Daily Load)

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  1. Benton Lake TMDL(Total Maximum Daily Load) Water Quality in a Shallow Lake January 22nd, 2008

  2. Objectives of this Presentation • What is a TMDL?? • Overview of Shallow Lake Ecology • Water Quality in Benton Lake • Watershed Characteristics • Water Quality • Plant and Fish Communities • Sources of Phosphorus • Water Quality Goal & How Do We Get There? • Questions????

  3. What is a TMDL?Total Maximum Daily Load TMDL ≡ LC = Σ LA + ΣWLA + MOS • A study that determines the maximum amount of a pollutant that a water body can receive and still meet water quality standards. • Originated from 303d of the Clean Water Act • Developed for waters not supporting designated uses

  4. What is a Shallow Lake? • MPCA definition: A lake with a maximum depth of 15 feet or less, or with 80% or more of the lake area shallow enough to support emergent and submerged rooted aquatic plants. • No thermal stratification- water column mixes.

  5. Clear and Turbid Water States • Clearwater State: • Abundant aquatic plant community • Low algal productivity • Large grazer (zooplankton) population • Turbid Water State: • High algal productivity • Low aquatic plant community • Low grazer population

  6. “Switches” • High levels of nutrients • Changes in hydrology • Maintained water levels • Flood control • Recreation • Destructive Fish • CARP! • Loss of top predators • Aquatic Vegetation Impacts • Herbicides, cutting and removal • boating

  7. Meuwissen Lake Watershed Developed: 8% Natural: 7% Water: 2% Agriculture: 77% Wetland: 5% Benton Direct Watershed Developed: 43% Natural: 20% Water: 1% Agriculture: 16% Wetland: 20%

  8. Total Phosphorus Total Phosphorus Goal: 90 ug/L

  9. Fish Populations 2003 MNDNR Rearing Pond Assessment: Fish Species found: 1. Black Bullhead-6 2. Carp- very abundant According to DNR survey, ~50 years ago northern pike were indicated to be present

  10. Aquatic Plant Surveys 2005 Survey Conducted by Carver County Staff • Cattail fringe around nearly entire lake • Very sparse sago pondweed Nearly entire lake bottom was void of aquatic plants!

  11. External Sources: Stormwater: Agricultural Animal waste Development Residential Degraded Wetlands SSTS Wastewater Discharge Precipitation Internal Sources: (Due to years of phosphorus build-up in the sediments) Rough Fish Carp, bullhead Wind Mixing Sediment Anoxia Phosphorus Sources

  12. 50% Meuwissen Lake 11% Direct inflow

  13. Goals **Quantitative: 90 ug/L Total Phosphorus Qualitative: increased aquatic plant coverage, zooplankton (algae eaters), low rough fish population- a clear water state.

  14. Benton Lake: What does the future hold??? • Improved Waterfowl Habitat • No or reduced populations of rough fish • Wildlife/waterfowl viewing opportunities • Canoeing, kayaking • Fishing opportunities

  15. Possible Projects • Focus first on EXTERNAL sources • Development load control (new and old) • Wetland protection/restorations • Reduce remaining agricultural runoff • Elimination of failing/direct discharge septic systems • Then on INTERNAL sources • Biomanipulation • Rough fish removal • Stocking of fish • Aquatic Plant establishment • Chemical Treatment

  16. Ways to Accomplish Our Goals What we can do: • County Water Plan and Water Rules • Cologne Stormwater Management Plan • Form partnerships (WWTP, DNR, USFW, ??)- to work on land and in-lake projects • What you can do: • Remain involved and informed

  17. Questions???

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