1 / 34

DOC and THMP loads from a restored wetland in the Delta

DOC and THMP loads from a restored wetland in the Delta. Jacob A Fleck Steven J. Deverel Roger Fujii. DWR RD1601 CALFED CBDA staff USGS staff. Wetland restoration. Many thousands acres of wetland restoration All native wetland types: Tidal, non-tidal, mudflat Benefits

korene
Download Presentation

DOC and THMP loads from a restored wetland in the Delta

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. DOC and THMP loads from a restored wetland in the Delta Jacob A Fleck Steven J. Deverel Roger Fujii DWRRD1601 CALFED CBDA staff USGS staff

  2. Wetland restoration • Many thousands acres of wetland restoration • All native wetland types: Tidal, non-tidal, mudflat • Benefits • Provide habitat for native species • Improve ecosystem function • Flood protection • Subsidence mitigation on organic soils • Engineering difficulties (deep subsidence) • Island in-fill • Setback levees • Impounded, flow-through wetlands

  3. USGS/DWR wetland restoration demonstration project • Initially established in 1997 • Use of wetland restoration as subsidence mitigation technique on deeply subsided islands • Impounded, flow-through system • This study established in 2000 • To determine the effects that wetland restoration will have on DOC and THMP loads from subsided peat islands.

  4. Demo pond setting: Twitchell Island

  5. Twitchell Island • Deeply subsided • As much as 20 ft • Peat soils dominate • >10 ft remain • ~35% OM • Primarily agriculture • srsr corn • Water upwelling

  6. Twitchell Island drainage

  7. Demonstration pond

  8. Peat soil high in C Two layers Zone of drain influence Well-decomposed peat High hydraulic conductivity Deep peat Unaltered peat Low hydraulic conductivity Soils/drainage

  9. Twitchell pumping station

  10. WQ Effects?

  11. Drinking water concern OH O= C C X n CR 3 O= C C X n HOOC O O HC Cl Cl 2 OH X Trihalomethanes HC X 3 OH OH OH Haloacetic Acids O= C O C O= O O C -OCl C COOH OH OH OH Haloketones -OBr CH2 O=C H3C C=O OH Haloacetonitriles CX3CN CH3 DOC MX Halophenols DBPs

  12. Study design • Collect samples of surface and subsurface waters for DOC and THMFP analyses • Combine with water flux data to calculate loads

  13. Monitoring plan • Surface inflow and outflow • Continuously monitored for water flux • Weekly sampling for DOC and THMFP • Piezometers • Sampled soil water 2x/yr for seasonal extremes in 2 depths at 3 piers • Shallow soils (0.5-2 ft) • Deep peat (8-10 ft)

  14. Water flux out of the pond

  15. Water flux (2001-2002)

  16. Demo pond surface water DOC

  17. DOC concentrations in soil water underlying the pond

  18. DOC loads (2001-2002)

  19. THMP loads (2001-2002)

  20. Compare net loads to ag

  21. Temporal trends • Surface water fluxes show strong seasonal trend • Subsurface DOC concentrations are decreasing over time in some shallow soil water (2001-2004)

  22. DOC concentrations in surface water (2001-2002)

  23. Net DOC flux out of the pond (surface waters, 2001-2002)

  24. THMFP (surface water)

  25. Net THMP flux from the pond (surface waters, 2001-2002)

  26. Subsurface trends

  27. Subsurface fluxes (estimated) • Seepage governed by hydraulic head • ~240 m3/day • Concentration in shallow soils declined over time • Pier H (2001) = 60 mg/L ~ 200 g/m2-yr • Pier H (2004) = 25 mg/L ~ 85 g/m2-yr • Pier K ~ 160 mg/L ~ 440 g/m2-yr

  28. Temporal trend summary • Wetland net surface fluxes are seasonal • Higher in summer and lower in winter • Opposite trend of ag operations • Subsurface fluxes • No apparent seasonal trend (lack of data?) • Concentration (fluxes) have been decreasing over time for soils in flow path

  29. DOC “quality”? • DOC quality differs in source of DOC and processing in the environment • We would expect ag, wetland soil, and surface water DOC to differ in quality • Food source vs drinking water problem? • Different carbon structures react differently in DBP formation • Some DOC structures are tasty some are not

  30. DOC “quality”

  31. Conclusions • Demo pond contributes more DOC and THMPs to Delta waters than nearby ag fields (>10x) • Most of demo pond loads derived from seepage through the shallow soils • If contribution from shallow soils minimized… • Demo pond loads would be more comparable to ag operations (DOC ~2x, THMPs ~4x) • Timing of loads would be different from ag operations (benefits?) • Demo pond surface water DOC is more reactive, but also more likely beneficial for food web (?)

  32. Implications • Design of large-scale wetland restoration sites need to consider shallow soil contributions to drain flow • Need to consider the effect changing the DOC load timing from converted fields will have on Delta ecosystems and drinking water facilities? • Need to balance potential benefits for subsidence mitigation, habitat restoration and food web dynamics with potential threats to drinking water supply

  33. Future and ongoing work • Twitchell South pond • Using lessons from demo ponds to monitor loads before, during, and after conversion • Expand studies to include other priorities (ie: MeHg) • Rice project • Using water management lessons to help determine BMPs for reducing DOC loads from rice fields in Delta • Compare conversion of corn fields to rice with conversion to wetland

  34. Questions?

More Related