NERL Research Abstract
EPA's National Exposure Research Laboratory
GPRA Goal 8 - Sound Science
APM # 643
Significant Research Findings
A Simulation Strategy for Modeling of Nitrogen and
Sediment Loadings from the Lower Mississippi River Basin
into the Gulf of Mexico
Purpose A primary environmental focus for the Louisiana/Texas coast is
characterization of the role of nutrients and sediments from the Mississippi
River Basin on the hypoxia zone ("dead zone") along the inner continental shelf
off the Gulf of Mexico. The goal of this research is to characterize the relative
importance of sources of nutrients and sediments and their loadings from the
sub-basins of the lower Mississippi River basin, and, ultimately, evaluate their
impact on water quality in the Gulf of Mexico.
Research A strategy is presented to develop watershed hydrologic and water quality
Approach simulation models of the Mississippi Region. It describes the watershed
models that supply input loadings to the Mississippi River and the Gulf of
Mexico, as well as water quality models of the interior river basins intended to
be used to estimate local impacts of nutrient management activities and
practices. The proposed model(s) include watershed hydrologic and water
quality components based on the EPA Hydrological Simulation Program -
FORTRAN (HSPF) program; river hydraulic and water quality components
also based on HSPF; and lake/impoundment hydraulic and water quality
components based on the U.S. Army Corps CE-QUAL-W2 program. Estuarine
flow and water quality model components are being developed separately by
the U.S. Navy and others as part of efforts to model the mainstem of the
Mississippi River and circulation and water quality within the Gulf of Mexico.
The proposed watershed models will be designed to enable researchers and
regulators to evaluate the impacts human activities, agricultural practices, land
use changes and policies, regulatory actions, and wetland conversion and
restoration. This Simulation Strategy for the Mississippi Region is designed as
a demonstration of how the proposed models and modeling framework can be
used to address these issues not only within the Mississippi Region, but also as
a template for possible extension of the approach to other river Basins.
National Exposure Research Laboratory - September 2000
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Major A pilot program was conducted in the Lower Mississippi Basin to determine
Findings and whether local water quality problems because of excessive nutrient loading
Significance exist3 and, if so, to characterize them and determine their relationships to
nutrient loading. This demonstration was conducted by the application of the
recommended approach (i.e., HSPF/CE-QUAL-W2) for predicting changes in
nutrient budgets in response to changes in proposed watershed activities/land
use/land cover, resulting in specific recommendations for reducing nutrient load
in the Lower Mississippi River Basin. Results indicate that sediment and
nutrient loadings to the Gulf are primarily coming from overland flow, and that
once in the stream channel, the majority of the nutrients are not degraded before
entering the Gulf. Best Management Practices (BMPs) can be used reduce
nutrient and sediment loadings in the basin, including precision farming,
agricultural nutrient management, other traditional agricultural BMPs,
vegetative buffer strips, wetland restoration, and alternate crop buffers.
Riparian buffers seem to have a major influence on the hydrology and are a
potential sink for nitrogen/sediment. The development of a comprehensive
watershed scale riparian model should be a high priority for this research. The
land in parts of the Mississippi Basin is extremely flat, making HSPF model
simulations inadequate. A more robust hydrology model is needed for these
areas.
Research The simulation strategy was designed and conducted by a research team at the
Collaboration National Exposure Research Laboratory's Ecological Research Division
*tu1l1. . including Robert F. Carousel and Jeff Holland of the U.S. Army Corps of
Publications ° J 1
Engineers Waterways Experiment Station.
Carousel, R.F., Holland, J.P. Simulation Strategy for Reducing Nitrogen Loads in Mississippi
River Basin. U.S. Environmental Protection Agency. Internal Report. 1999.
This strategy has been adopted as the base documentation for the Modeling
Subcommittee from the Gulf of Mexico program. It will be expanded over the
next two years to include ecological, hypoxic, biological, land reclamation, air,
and framework components. At the end of this period the strategy will be
developed into a research plan that will be peer reviewed.
Inquiries concerning this research can be directed to:
Robert F. Carousel
U.S. Environmental Protection Agency
National Exposure Research Laboratory
Athens, GA 30605
Phone: (706)355-8065
E-mail: carousel.robert@epamail.epa.gov
Future
Research
National Exposure Research Laboratory - September 2000
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