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Gulf of Mexico Hypoxia Modeling and Monitoring
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Study Purpose: Support the goals of the Hypoxia Action Plan by providing the scientific framework to guide a reduction in the frequency, duration, size, and degree of oxygen depletion in the northern Gulf of Mexico.
Objective: Provide the science through the application of an integrated framework to set a nutrient loading cap, protective of the northern Gulf of Mexico which will reduce the hypoxic zone to 5000 sq.km by the year 2015. Aid water resource managers in making scientifically-defensible nutrient control decisions for reducing Gulf hypoxia and restoring habitats along the Gulf coast.
Framework: Provide strategic management support through the integration of monitoring, condition assessment, diagnosis, experimentation, and model forecasting.
Modeling Approach: Apply a multimedia, mathematical modeling construct, supported by a statistically-based sampling design, to develop a forecasting ability to reduce uncertainty associated with setting a nutrient loading cap. The mass balance modeling approach allows calculation of the multimedia nutrient load to the Gulf and provides a synthetic picture of the nutrient sources, losses, and processes by major source category. The forecast modeling permits examination of various load reduction scenarios, the environmental benefits of each, and the time to reach desired oxygen levels.
Modeling Construct: Assemble and apply a suite of linked and coupled atmospheric, meteorological, hydrodynamic, sediment resuspension and transport, water quality, and eutrophication models, which synthesize inputs, environmental data, and ecosystem dynamics to develop a forecasting capability. Modeling components under review are as follows: Atmospheric/Air deposition model (CMAQ), Hydrodynamic, MET, and wave model (IAS, PDOM, ECOM, ROM ), Sediment Transport and Fate model (IPX-MT, SEDZL, QUAL-ICM, ECOMSED), Water Quality Fate and Transport Model (WASP, CE-QUAL-ICM), and Eutrophication, Kinetics, and Dissolved Oxygen Model (WASP, CE-QUAL-ICM).
Expected Benefits/Outcomes: Examine and confirm the hypothesis that the total nitrogen load to the Gulf from the Mississippi River and other tributaries is the greatest risk and is controlling oxygen depletion. From the results of the integrated framework and modeling construct, determine the total aggregate load to the receiving water and the relative nitrogen contribution from all major sources (atmosphere, tributaries, and sediments). Modeling forecasts with known certainty will be used to examine different nitrogen reduction scenarios in a socioeconomic context, and to set a total nitrogen loading cap (total maximum daily load - TMDL) which guides the restoration of oxic conditions of Gulf bottom waters that are beneficial to multiple receptors. The Gulf loading cap can be allocated among all tributary inputs and can also serve as a target for watershed TMDLs and watershed restoration efforts. Cognizant of the loading cap, model forecasting will also determine the resultant nutrient criteria for the designated beneficial use of the northern Gulf. With modest modification and appropriate data, the framework and modeling construct can be applied to other contaminants such as mercury.
Progress, Actions and Timeframe: The field design and parameters to be measured for the base sampling years support the modeling effort; some adjustments to what is measured and what experimentation is to be conducted will be made. Much of the data collection has been completed aboard EPA vessels. The statistically-based field sampling, specifically designed to support the modeling framework included water, sediments, biota, and other physical-chemical characteristics. Sampling occurred across the Louisiana-Texas (LATEX) coastline and to approximately 100 km offshore to satisfy the latitude-longitude spatial resolution required and sampling of the Gulf south of the hypoxic zone. Through this project NHEERL is supporting the EPA Gulf of Mexico Program Office and the Hypoxia Action Plan. However, both internal and external networking has been extensive. A series of briefings and meetings have occurred with diverse groups for planning purposes, including the Gulf of Mexico Program Office, Department of Navy, NERL- RTP, NERL-Athens, NOAA, Regions 3, 4, 5, and 6, Office of Water, OWOW, MMR Task Force, and Louisiana State University. A major deliverable in the ORD Water Quality Multi-Year Plan (Goal 2) to is to deliver the database appropriate for modeling.
Partners: USEPA Gulf of Mexico Program Office, USEPA Office of Water, USEPA Office of Research and Development, USEPA Region 4, USEPA Region 6, and the Gulf States
Contacts:
Russell G. Kreis Jr., USEPA ORD NHEERL MED- Duluth, MN/Grosse Ile, MI
Richard M. Greene, USEPA ORD NHEERL GED- Gulf Breeze, FL
Publications:
Greene, R., R. Kreis, P. Eldridge, J. Hagy, M. Murrell, J. Lehrter, and G. Thursby. 2006. Tools Supporting Coastal Nutrient Criteria Development. Board of Scientific Counselors (BOSC) Review, Cincinnati, Ohio, January 25, 2006. (Poster and Abstract)
Greene, R.M., J. Hagy, M. Murrel, J. Kurtz, J. Lehrter, and R.G. Kreis, Jr. 2005. Multimedia Mass Balance Modeling and Seasonal Monitoring of Hypoxia in the Northern Gulf of Mexico. Mississippi River Basin Nutrients Science Workshop. Presenters: R.G. Kreis, Jr. and J. Kurtz. St. Louis, MO, October 4-6, 2005, p. 34 (Abstract)
Kreis, R.G., Jr. and R.M. Greene. 2004. Gulf of Mexico Hypoxia Monitoring and Modeling. USEPA Gulf of Mexico Program Review. New Orleans, LA, October 27-28, 2004.
Kreis, R.G., Jr., and R.M. Greene. 2002. Modeling and Field Sampling in the Gulf of Mexico. Briefing to the Gulf of Mexico Program Office and Regional Administrators of USEPA Regions 4, 5, 6, and 7. Gulf Breeze, Florida., December 5, 2002.