WETLAND RESTORATION: CAN IT IMPROVE THE QUALITY OF THE YAHARA LAKES?

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1 WETLAND RESTORATION: CAN IT IMPROVE THE QUALITY OF THE YAHARA LAKES? Ken Potter Department of Civil & Environmental Engineering Gaylord Nelson Institute for Environmental Studies University of Wisconsin Madison

2 WETLANDS A wetland is a landscape feature characterized by soils that are saturated all or part of the time. In addition to supporting very diverse ecosystems, wetlands can moderate floods and provide water quality benefits.

3 WETLAND DEGRADATION About half of the pre settlement wetlands in the lower 48 states were drained, mainly for agriculture. In the Upper Rock River Watershed, about 60% of the historical wetlands were drained. Most of the remaining wetlands in the U.S. have been severely degraded.

4 QUESTION Can restoration of drained or degraded wetlands be an effective strategy for improving water quality in the Yahara Lakes?

5 OUTLINE Dorn Creek wetland: degraded wetland in the Lake Mendota watershed Jackson Creek wetland: constructed wetland in the Delavan Lake watershed Everglades Stormwater Treatment Areas: stateof the art constructed wetlands Recommendations for wetland restoration as a strategy for improving water quality in the Yahara Lakes.

6 UPPER DORN CREEK WETLAND Upper Dorn Creek wetland (2.6% of watershed) Lake Mendota

7 MEASUREMENT LOCATIONS Dorn Gage Ripp Gage

8 Dorn Creek Peak Discharges Inflow (cms) Outflow(cms) ~2-yr. event Discharge (m 3 /s) Event

9 Innundation Area (above normal) 0.5 Fraction of Area Inundated Outflow Peak Flow (cms)

10 Dorn Creek Sediment Inflow Outflow Sediment (kg) Total Event

11 Dorn Creek Sediment: 6/ Sediment (kg/hr) Inflow Outflow Time (hrs)

12 Dorn Creek Sediment: 6/ Enhanced peak due to erosion of sediment in channel Sediment (kg/hr) Inflow Outflow Time (hrs)

13 DORN CREEK CHANNEL Channel

14 Dorn Creek Sediment: 6/ Sediment (kg/hr) Inflow Outflow Delayed pulse due to return of flow from ditches Time (hrs)

15 DITCH LOCATIONS Ditches Ditch

16 700 Dorn Creek Total Phosphorus Phosphorous (kg) TP In TP Out Total EVENT

17 Dorn Creek Dissolved Phosphorus Dissolved Phosphorous (kg) DP In DP Out -37% Total Event

18 SUMMARY SEDIMENT For the two largest events, which accounted for 96% of the sediment exported, the sediment outflow was about 100% greater than the inflow. Erosion of sediment in the main channel Erosion of sediment in the two primary ditches

19 SUMMARY PHOSPHORUS The wetland sequestered 47% of the dissolved phosphorus. The wetland released 34% more particulatebound phosphorus than it received. Overall, the wetland had no impact on the transport of total phosphorus.

20 RECOMMENDATIONS The treatment efficiency of the Dorn Creek wetland could be significantly enhanced by increasing connectivity: Eliminating the drainage ditches; Installing adiversion structure on the main channel at the head of the wetland. Otherwise most of the flow will bypass the wetland.

21 DORN CREEK WETLANDS Upper Dorn Creek wetland Lower Dorn Creek wetland Lake Mendota

22 JACKSON CREEK CONSTRUCTED WETLAND USGS Fact Sheet FS acre shallow prairie marsh with 3 sediment retention ponds (5.8 ac.); receives runoff from a 16.6 mi 2 watershed. (Wetland area is about 1% of watershed area.) Enlargement of a 15 ac. wetland Constructed as a component of a 5 year program to control nutrient delivery to Delavan Lake.

23 JACKSON CREEK CONSTRUCTED WETLAND USGS Fact Sheet FS

24 Jackson Creek Wetland Sediment Sediment inflow Sediment outflow -46% Sediment (tons) % % -31% Total Year

25 Jackson Creek Wetland Total Phosphorous TP inflow TP outflow -18% Total P (pounds) % -39% -12% Total Year

26 Jackson Creek Wetland Dissolved Phosphorous Dissolved P inflow Dissolved P outflow -11% Dissolved P (pounds) % -12% -13% Total Year

27 COMMENTS For the sampling period, the Jackson Creek constructed wetland removed about 50% of inflowing sediment, about 20% of inflowing phosphorous and about 10% of dissolved phosphorous. During late spring and early summer, the wetland tended to release excess dissolved phosphorous. The wetland removed less than 1% of nitrogen associated with nitrite and nitrate.

28 EVERGLADES STORMWATER TREATMENT AREAS South Florida Water Management District

29 STORMWATER TREATMENT AREA 2 South Florida Water Management District

30 EVERGLADES STORMWATER TREATMENT AREAS 65 mi 2 constructed to date Since 1994 the STA s have reduced total phosphorous loads by 70%, reducing the mean concentration from 145 parts per billion to 45 parts per billion.

31 Everglades Stormwater Treatment Area 1W (Data from Abtew, Gorforth, and Germain, 2004) % Total Phosphorous (metric tons) % Inflow TP Outflow TP -71% -75% Year

32 STA REHABILITATION EFFORTS Removal of the phosphorous rich accrued layer consisting largely of highly flocculent material Removal of plant material Ground leveling to reduce flow constriction and short circuiting Rice planting to stabilize soils Inoculation with submerged aquatic vegetation

33 CAN WETLAND RESTORATION IMPROVE THE QUALITY OF THE YAHARA LAKES? Yes, if Wetland restorations are carefully designed and maintained. The latter requires removal of vegetation and accumulated sediment. The regulating agencies are agreeable to tradeoffs that this will entail with respect to wetland habitat values.

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35 DOMESTICATED NATURE Humans have drastically altered landscapes and ecosystems throughout the world for the benefit of humanity. In such domesticated landscapes, the central scientific issues must address human interactions and interests. To quote from Kaveiva, et al. (2007): "The key scientific goals for the study of domesticated nature are to understand what tradeoffs exist between the promotion or selection of different ecosystem services and to determine to what extent we can change a negative tradeoff to a positive one by altering the details of our domestication process. Kareiva, Watts, McDonald, and Boucher, "Domesticated Nature: Shaping Landscapes and Ecosystems for Human Welfare," Science, 316(5833), , 2007.

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