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Modeling the linkage of discharge and nutrients from the Mississippi River basin to Gulf of Mexico hypoxia


The objective of this task is the development of a modeling framework for predicting how nutrient management decisions and future climate change scenarios will impact the size, frequency, and duration of the low oxygen, i.e. hypoxia, area that forms every summer on the continental shelf of the northern Gulf of Mexico. The proposed modeling framework includes a northern Gulf ocean model and a Mississippi River basin model.

Rationale and Research Approach:

The proposed modeling framework includes a northern Gulf ocean model and a Mississippi River basin model. The ocean models consist of state-of-the-art linked hydrodynamic (EPACOM), eutrophication (GEM and GoMDOM), and nutrient air deposition (CMAQ) models, and have been developed by NHEERL Gulf Ecology Division (GED), NHEERL Mid-Continent Ecology Division (MED), EPA Office of Environmental Information/ Environmental Modeling and Visualization Lab (OEI/EMVL), NERL Atmospheric Modeling and Analysis Division (AMAD), and collaborators at the Naval Research Laboratory. The ocean model is based upon a decade of extensive oceanographic observations collected by GED. To help parameterize the complex 3-D models and to better understand the complex interactions between nutrient supply and the resultant lowering of oxygen levels in the Gulf of Mexico, one-dimensional (1-D) GEM and GoMDOM models have been constructed to allow for rapid model runs to calibrate and validate against the extensive set of process and time-series measurements made by GED at specific locations on the continental shelf. The results from this approach will be used in fully functional 3-D GEM and GoMDOM models. These calibrated 3-D models will provide the mechanistic connection between nutrient loadings and model-predicted hypoxia area, duration, and frequency, and will be used to assist the Mississippi River Gulf of Mexico Watershed Nutrient Task Force in achieving their goal, "to reduce or make significant progress toward reducing the five-year running average areal extent of the Gulf of Mexico hypoxic zone to less than 5,000 square kilometers by the year 2015" (Gulf Hypoxia Action Plan 2008). Currently, the hypoxia zone exceeds this maximum. We will model management scenarios as well as engineering sensitivity/uncertainty runs to help decision-makers, who are tasked with protecting this resource, gain a better understanding of the relationship between nutrient loading and hypoxic impact. The Mississippi River basin model will link the NERL AMAD suite of coupled atmospheric models to a pre-existing watershed and water quality model such as SWAT, LSPC, NEWS, or SPARROW. The coupled atmospheric suite of models is comprised of the WRF meteorological model (the standard driver for CMAQ), the VIC hydrologic model (a macroscale model from the University of Washington), and the CMAQ deposition/air quality model and is being produced by NERL AMAD. The WRF will be coupled with VIC through the flux coupler CP7 from the climate community in collaboration with the Pacific Northwest National Laboratory and Washington State University as part of ACE MDST-3 research. This is a critical part of the research. The watershed model for linkage to the atmospheric system will be chosen based on discussion with the SSWR agricultural land use change project, EPA Office of Water and SHC Nitrogen project external collaborators at Washington State University. The climate scenarios will be coordinated with ACE MDST-4 dynamic downscaling of WRF to produce decade long current and future climate scenarios. The coupled atmospheric system will be simulated with the downscaled climate scenarios and linked to the water quality model to deliver loads for the northern Gulf ocean model. Future nutrient management and agricultural modeling scenarios for the basin will be coordinated with EPA OW and the Gulf Hypoxia Task Force, chaired by EPA.

MED Scientists:

John Filkins
Kenneth Rygwelski
Russell Kreis
James Pauer


Hill, B.H., C.M. Elonen, L.E. Anderson, and J.C. Lehrter. Microbial respiration and extracellular enzyme activity in sediments from the Gulf of Mexico hypoxic zone. Aquatic Microbial Ecology, in press.

Pauer, J.J., T.J. Feist, A.M Anstead, W. Melendez, R.G. Kreis, Jr., and K.R. Rygwelski.  2012. Gulf of Mexico Dissolved Oxygen Model (GOMDOM) Research and Quality Assurance Project Plan.  U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Large Lakes and Rivers Forecasting Research Branch, Large Lakes Research Station, Grosse Ile, Michigan.  66 pp.

Expected Products:




Sep 30, 2014 2.3.D.2 Report on the GEM and GoMDOM predictions of the effects of nutrient load reduction and climate change scenarios on Gulf of Mexico hypoxia. Russell Kreis
Sep 30, 2013 2.3.D.1 Report on the Gulf Ecology Model (GEM) and the Gulf of Mexico Dissolved Oxygen Model (GoMDOM), state of the art hypoxia models that will be used to assess the relationship between freshwater discharge and nutrient loads from the Mississippi River Basin and the extent and frequency of hypoxia on the Louisiana continental shelf. Russell Kreis
Sep 30, 2016 2.3.D.3 Report on multi-media scenarios of air quality and deposition, watershed processing, water quantity and water quality using state of the science models to address sustainability of nutrient management in the face of changes in climate and land use. Russell Kreis

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