Water Quality Model Passes Another Test
By Don Comis
February 24 , 2010
A test of the SWAT (Soil and Water Assessment Tool model on a
small watershed with poor water quality in Maryland showed that the model
accurately estimated pollutant levels on an annual basis, according to
Agricultural Research Service (ARS)
scientists and their University of Maryland cooperators.
Water resources engineer
Sexton and soil scientist
Sadeghi, at the
Hydrology and Remote Sensing Laboratory in Beltsville, Md., worked with
watershed hydrologic and water quality modeler Adel Shirmohammadi, at the
University of Maryland, College Park, on an
11-year study of the Warner Creek watershed in Frederick County, Md
Shirmohammadi and Hubert Montas, professor and associate professor,
respectively, in bioenvironmental and water resources engineering at the
University of Maryland, also worked with several graduate students and
post-doctoral researchers at the University, particularly during the first
seven years of the study. The U.S. Environmental
Protection Agency provided the major funding for this project with a grant
authorized by Section 319 of the Clean Water Act, which addresses non-point
sources of water pollution. ARS provided supplemental funding.
This approximately one-square-mile watershed drains into a tributary of the
Monocacy River. High levels of nitrogen and phosphorus flow from the
966-square-mile Monocacy River Basin into the Chesapeake Bay, mostly from
cattle manure and crop fertilizers. The Warner Creek watershed is a mix of
farm, forest, and urban lands.
Shirmohammadi, Sexton, Sadeghi, and other colleagues in the project found
the SWAT model to be satisfactory on an annual basis in mixed land use
watersheds in the Piedmont physiographic region studied, and thus suitable for
use in EPA's "Total Maximum Daily
Load(TMDL)" program. This program sets limits on water pollutants such
as silt, nitrogen, phosphorus, pesticides, mercury and bacteria for about
40,000 bodies of water that EPA has found to have poor water quality.
A team of ARS agricultural engineers in Temple, Texas, led by
Arnold,developed the SWAT model in the early 1990s.
ARS is the principal intramural scientific research agency in the
U.S. Department of Agriculture.