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Modeling Fecal Bacteria Fate and Transport to Address Pathogen Impairments in the United States

Modeling Fecal Bacteria Fate and Transport to Address Pathogen Impairments in the United States. Brian Benham Extension Specialist and Associate Professor, and Director, Center for Watershed Studies Biological Systems Engineering Virginia Tech. Center for Watershed Studies. Objectives .

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Modeling Fecal Bacteria Fate and Transport to Address Pathogen Impairments in the United States

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  1. Modeling Fecal Bacteria Fate and Transport to Address Pathogen Impairments in the United States Brian Benham Extension Specialist and Associate Professor, and Director, Center for Watershed Studies Biological Systems Engineering Virginia Tech Center for Watershed Studies

  2. Objectives • Background • What is watershed management? • What is a TMDL? • Review the VA TMDL process with generalizations • Impairment Designation • TMDL Development • Implementation • Discuss fecal indicator bacteria modeling for TMDL development in the U.S.

  3. What is Watershed Management? • Watershed management recognizes that the water quality of our streams, lakes, and estuaries results from… • human activities • watershed characteristics in upstream areas • The goal of watershed management is… • an environmentally and economically healthy watershed that benefits all stakeholders • Each watershed management plan includes… • unique goals • site-specific management strategies to achieve those goals

  4. Watershed Management: Historical Perspective • Nineteenth an early to mid-twentieth Century • Goal was to enhance value of water bodies for residential, agricultural, industrial, navigational, recreational, and power generating uses, and to reduce flooding • 1970’s • Increasing national concern with water quality. Clean Water Act (CWA) passed in 1972 – restore chemical, physical, and biological integrity of nation’s waters. • Focus on point sources, wastewater treatment • Major improvements in water quality • 1980’s to today • Broader concern with ecosystem management and restoration. Nonpoint source pollution control. Ambient water quality.

  5. What is a TMDL? • A Total Maximum Daily Load (TMDL) quantifies the amount of a particular pollutant a waterbody can receive and still meet water quality standards (pollutant budget). TMDL = WLA + LA + MOS Where: WLA = waste load allocation (point sources) LA = load allocation (nonpoint sources) MOS = Margin of safety • 3-phase process • Impairment Designation • TMDL Development • Implementation

  6. 6 Existing Condition TMDL Scenario Conceptual TMDL Concentration Water Quality Standard Concentration, C (mg/L) Time Center for Watershed Studies

  7. TMDL Process 7 Clean TMDL Development Study Impairment Designation Water quality standards met Water quality standards not met Adaptive management Monitoring Implementation Watershed study to determine needed pollutant reduction Implementation Planning How many and what type of ‘fixes’ are needed? Center for Watershed Studies

  8. Why is a bacterial impairment Bad? • Fecal indicator bacteria (FIB) are fecal coliforms originating from the feces of humans or animals • Presence of FIB indicate that other disease causing organisms may be present • Human Health Concern • Chance of gastrointestinal illness or infection during primary contact (e.g., water in mouth, nose, eyes, open wounds) • 14% of 76,000 currently listed impairments are bacterial impairments (USEPA, 2009)

  9. TMDL Process 9 Clean TMDL Development Study Impairment Designation Water quality standards met Water quality standards not met Adaptive management Monitoring Implementation Watershed study to determine needed pollutant reduction Implementation Planning How many and what type of ‘fixes’ are needed? Center for Watershed Studies

  10. TMDL Development Phase • Determine existing and potential future pollutant loads in the watershed • watershed characterization and pollutant source characterization (model inputs) • Link loads to waterbody water quality • pollutant fate and transport modeling • existing and future conditions • Define the pollutant load reductions required to achieve applicable water quality criteria • allocation analysis: use model(s) to allocation pollutant loads

  11. Link pollutant sources to water quality with aid of models • Watershed model • Watershed characterization • Source characterization • Climate variability • Fate and transport • Allocation analysis Models are used to predict how watersheds respond, and to evaluate pollutant reduction options = X Land use and Management Stream Network Source: EPA 841-B-05-005

  12. FIB modeling • Computer-based water quality simulation models used extensively to develop pathogen TMDLs • Models have the capability to estimate watershed-scale FIB loads over range of flow conditions and can evaluate effectiveness of proposed control measures (BMPs) • HSPF – Hydrological Simulation Program-FORTRAN • SWAT – Soil Water Assessment Tool

  13. HSPF – Hydrological Simulation Program-FORTRAN Supported by USEPA and Aqua-Terra consultants Watershed scale, process oriented, lumped parameter, continuous simulation Spatial variability represented in limited way by dividing watershed into subwatersheds and various land uses Land surface FIB loads determined externally and input as monthly varying loads Loads directly deposited into waterbody (e.g., sewage treatment, livestock, wildlife, etc) input as time series Groundwater and interflow are input as monthly varying loads

  14. Wildlife Livestock Crop land Forest Pasture Die off Residential In-stream Humans and Pets Watershed and Source Characterization Production and Distribution of Bacteria

  15. Bacteria Source Load Calculator (BSLC) BSLC: a tool for bacteria source characterization for watershed management. Applied Eng. Agric. 21(5): 879-889. Excel/Visual Basic program designed to facilitate watershed and bacteria source characterization data entry and analysis for HSPF

  16. HSPF cont. No specific modules to simulate FIB fate and transport, but PQUAL is used FIB simulated as free-phase constituent (also described as planktonic, water-column, “dissolved”) While HSPF can discriminate between free-phase and particle-associated FIB, data needed to parameterize particle-associated FIB simulation do not exist

  17. HSPF cont. • FIB fate and transport • On the land surface: die-off simulated by limiting “build-up” and specifying amount of runoff needed to “wash-off” accumulated load. Both build-up and wash-off can be land use specific. • In-stream: die-off simulate with 1st order temperature-dependent kinetics, Chick’s Law. Re-growth/re-suspension not simulated. • No distinction made between sources; FIB from all sources subject to same die-off and transport parameters • Representation of BMPs • Reduce loads to land surface • Performance efficiencies (i.e., average % load reduction factor)

  18. Die-off Die-off Direct Deposit Die-off In-stream Fate and Transport of Bacteria: Livestock Crops Storage Pasture

  19. Source Breakdown Center for Watershed Studies Center for TMDL and Watershed Studies

  20. SWAT • Supported by USDA-ARS • Conceptually similar to HSPF • Spatial variability represented in limited way by Hydrologic Response Units (HRU). Combination of soil land use, topography, etc. • Has specific FIB module • Allows for variable loading and partitioning to and between the waterbody, soil, and foliage • Allows for variable wash-off and attachment, and for differential die-off and re-growth in-stream and in the soil

  21. Consequences of limited confidence in FIB inputs and knowledge about fate and transport mechanisms (Novotny and Chesters 1981)

  22. Needed Advancements • Additional data to more accurately characterize fate and transport • FIB generation (fecal densities), die-off, attachment, re-growth, and re-suspension, etc. • Advancements in microbial source tracking (MST) • Improvements in technique accuracy • More consistency among methods • Advances in MST could allow for more effective prioritization i.e., addressing those impairments that pose most heath-related risk • Better understanding of how models handle extreme events (high and low flows)

  23. TMDL Process 23 Clean TMDL Development Study Impairment Designation Water quality standards met Water quality standards not met Adaptive management Monitoring Implementation Watershed study to determine needed pollutant reduction Implementation Planning How many and what type of ‘fixes’ are needed? Center for Watershed Studies

  24. 24 Identify and prioritize appropriate BMPs Center for Watershed Studies

  25. 25 Establish goals and milestones Center for Watershed Studies

  26. Flyer for pet waste education program – Courtesy Roanoke River Roundtable

  27. Fencing and Riparian Buffer Photos: Virginia Department of Conservation and Recreation

  28. Adaptive management www.epa.gov/nps/watershed_handbook/ EPA 841-B-08-002

  29. http://www.epa.gov/owow/tmdl/pathogen_all.pdf EPA 841-R-00-002

  30. Good resource www.epa.gov/nps/watershed_handbook/ EPA 841-B-08-002 http://www.epa.gov/owow/TMDL/pdf/draft_handbook.pdf

  31. Thank you감사합니다 Brian Benham, benham@vt.edu

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