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Exploration of Enhanced Treatment Wetlands

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Exploration of Enhanced Treatment Wetlands

  1. 1. Exploration of Enhanced Treatment Wetlands Nicole Van Helden The Nature Conservancy Jeremy Freund Outagamie County
  2. 2. The Problem
  3. 3. Treatment Wetlands
  4. 4. One Goal Literature Review
  5. 5. Range in Studies ■ Total Nitrogen:  17% to 99% ■ Total Phosphorus:  -64% to 80% ■ Plant available Phosphorus:  -120% to 89%
  6. 6. Factors Influencing Retention • Retention Time • Hydraulic Loading • Mineral Content • Seasonality and Vegetation • Location of Wetland
  7. 7. and More Factors…  Retention Time  Hydraulic Loading  Mineral Content of the Soil  Seasonality and Vegetation  Location of wetland  Watershed to wetland ratio  Shape of wetland  Inflow type  Slope  Concentration of nutrient load  Soil pH  Soil particle size  Erosion off fields  Age of wetland  Presence of wildlife  Phosphorus concentration in pore water  Water depth  Temperature  Precipitation
  8. 8. Design Guiding Principles • Tile water input • Conventional farming • Watershed to wetland ratio: 20:1 or 5% • (10 acre watershed to ½ acre wetland) • Retention time: 1 inch runoff, 12” deep for 5-7 days • Flood storage: 24 hour release of 25 year event • Start Simple • Able to monitor
  9. 9. Monitoring • Phosphorus: Particulate, Dissolved and Total • Nitrogen: Total • TSS • Precipitation • Stage • Post-Trap • TNC: Soil samples, Sedimentation rates, Vegetation
  10. 10. Landowner Buy-In • Existing Relationship • Operator Relationship • Rent Offset • Access Improvement • Sunset • PR
  11. 11. Modeled Hydraulic Performance Hours
  12. 12. When a new element comes into your universe, there is only one thing you can possibly do…expand! ~unknown
  13. 13. Nicole Van Helden-TNC Jeremy Freund-Outagamie County LCD Questions?

Notas del editor

  • Exploration of the use of Enhanced Treatment Wetlands to manage both sediment and nutrients in agricultural runoff in Wisconsin.

    First Nicole will talk about understanding the science in how wetlands reduce/retain phosphorus and nitrogen
    Then Jeremy will talk about an on-the-ground example of where Outagamie Co and partners are working to construct treatment wetlands in an agricultural setting
  • Nitrogen and phosphorus are naturally occurring in waterways, but when there is an overabundance of nutrients threatens drinking water and wildlife, increases water treatment costs for communities and reduces nature’s resilience to climate change

    Dodds et al estimated that eutrophication costs the US economy U.S.$2.2 billion annually due to decreased recreational use of impaired waters, decrease value of waterfront properties, restoration efforts for threatened and endangered species, and providing alternative drinking water
  • Goal of project: reviewing literature to determine state of science. Can treatment wetlands be used to reduce phosphorus and nitrogen in an agricultural setting.

    Definition of treatment wetland: a created or re-established system that is man-made and designed to accomplish a reduction goal of pollutants.

    Review current policies and programs in nutrient management strategy
    Identify research needs – where is there unknown information on treatment wetlands?
    Give recommendations for moving forward with the project
  • Goal of going through the literature and attempting to come up with a golden number for the amount of phosphorus and nitrogen that wetlands are able to reduce/retain

  • See a large variation of the amount of reduction in phosphorus and nitrogen that a wetland can retain/reduce.

    Discuss the range of variation within and between the studies
    Large range – say the numbers
    Also talk about the differences between how the studies report their data

  • Retention Time
    Important for phosphorus and nitrogen retention
    As stated earlier in the presentation one of the main mechanisms in which phosphorus is retained within a wetland is by settling – the phosphorus that is attached to soil particles needs time to be able to settle out – this occurs when there is a long enough retention time within the wetland
    Think of it as a jar of water with sand in the bottom and when you shake up the jar the particles are all dispersed within a jar – time is needed without water movement in order for the sand particles to return to the bottom on the jar – the same is true for particulate phosphorus in a wetland
    Longer retention time lead to anaerobic conditions which are needed for denitrification – and if you remember from earlier in the presentation denitrification is one of the main mechanisms that remove nitrogen from the system all together
    Studies range from 16 hours to 2 days to 14 days to the ideal retention time

    Hydraulic Loading
    High flow events can reduce phosphorus retention – not enough retention time
    Might be more P retained but lower efficiency (% retained may be less)

    Aluminum and Iron Content
    One of the main ways phosphorus is removed from the water column is through the process of adsorption
    Presence of Fe, Al, and Ca will determine the number of adsorption sites available
    Adsorption is a finite process – a saturation point will be reached

    Seasonality and Vegetation
    Summer – growing season – wetlands act as a sink the majority of the time
    Spring – snowmelt and heavy rains as well as vegetation not established – there is more of a chance for nitrogen and phosphorus to be release
    Fall – plants dying – could result in an increase of N and P from the wetland – decaying plant material
    Temperature – denitrification
    Cannot be too cold or too warm
    Phosphorus release tended to occur in late spring and summer from wetlands constructed by lake Delavan
    Winter and spring at the highest nitrogen loads – Lake Bloomington
    Been cited to only be a sink of N and P if there is regular harvesting of the plants;
    Other roles: decrease flow and increases residence time
    Can account for 16-75% of the nitrogen removal in wetlands
    Study to understand how different plants will use more nitrogen and phosphorus therefore removing it from
    Root zone is where nitrification and denitrification take place

    Location of Wetland
    Modeling exercise in Walnut Creek, Iowa to understand importance of wetland location
    When placed and only receive 4% of the load, only reduced by 4%; when placed where they would receive 70% of the nutrient load coming into the waterbody, the load was reduced by 35%
    Understand this is just a modeling exercise – not sure how accurate it would be – need more on-the-ground research

  • Important to note here that these are complex systems and it is not possible to generalize with confidence on how well a wetland will perform
  • What now?
    GLRI grant o explore treatment wetlands more. 6 small treatment wetlands. Monitor 2 (hoping more). Look at tile water.