Section 319
NONPOINT SOURCE PROGRAM SUCCESS STORY
Installing Earth Embankments Improves Water Quality
Waterbodv Improved Channelization and non-irrigated crop production led to
y ^ increased erosion and siltation in an unnamed tributary to
Tennessee's Obion River. High sediment levels altered the substrate habitat and caused
a loss of biological integrity, prompting the Tennessee Department of Environment and
Conservation (TDEC) to add the 25.8-mile-long unnamed tributary to the state's 2002 Clean
Water Act (CWA) section 303(d) list of impaired waters. With support from the Tennessee
Agricultural Resources Conservation Fund (ARCF), local landowners installed dikes (earth
embankments) along the tributary. Water quality improved, and TDEC removed the Obion
River tributary from Tennessee's CWA section 303(d) list of impaired waters in 2008.
Problem
A 25.8-mile-long unnamed tributary to the Obion
River flows through Tennessee's Dyer and Obion
counties and the community of Miston (Figure 1).
The tributary is in Northern Mississippi Alluvial Plain
ecoregion 73a in northwest Tennessee. During the
last century, landowners channelized sections of
the Obion River and many of its small tributaries
to increase flow efficiency for agricultural uses.
Unfortunately, channelizing the waterways also
caused increased erosion, downstream flooding,
and a loss of wildlife habitat.
A 2001 macroinvertebrate survey of the unnamed
tributary to the Obion Riveryielded a biological
reconnaissance (biorecon) index score of poor.
Biorecon is one tool used to recognize stream
impairment as judged by species richness mea-
sures, emphasizing the presence or absence of
indicator organisms without regard to relative abun-
dance. The principal metrics used were the total
number of macroinvertebrate families (or genera),
the number of families of mayflies, stoneflies and
caddisflies (collectively referred to as EPT—short
for the order names Ephemeroptera, Plecoptera and
Trichoptera), and the number of pollution-intolerant
families found in the stream.
The 2001 biorecon score for the unnamed tributary
to the Obion River indicated that the tributary did
not support its designated use of fish and aquatic
life. Sediment contributed by non-irrigated crop
production and channelization physically altered the
substrate habitat and caused a loss of biological
Unnamed Tributary to the Obion River
TN08010202001-0100
BMPs
Unnamed Tributary to Obion River
— Streams
Tennessee Counties
Unnamed Tributary Watershed
ID
1
2
3
NRCS Code
356
356
356
Practice
Dike
Dike
Dike
TN Dept of Agriculture
8/14/2008
Figure 1. A 25.8-mile-long unnamed tributary flows into the Obion
River in western Tennessee. Landowners installed three dikes in
the watershed to reduce sedimentation from cropland.
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Results
Figure 2. Example of a dike, or earth embankment.
integrity. As a result, TDEC placed the unnamed
tributary to the Obion River on the state's CWA sec-
tion 303(d) list of impaired waters in 2002.
Project Highlights
Using funds provided by Tennessee's ARCF, local
landowners installed three dikes (embankments
constructed of earth and planted with crops or
grass) in the unnamed tributary's watershed (see
Figure 1 for project locations). One was installed in
2004 and the two others in 2005. The dikes control
water levels and protect against flooding, thereby
preventing damage to cropland and property
(Figure 2). During the winter and spring, the dikes
retain water from the cropland areas, trapping sedi-
ment and any nutrients or pesticide residues in the
outflow. The water is released slowly in the spring
through pipe outlets, helping to prevent further
erosion.
TDEC established a Semi-Quantitative Single
Habitat Assessment station at mile 1.6 near Spence
Spur Road and, in 2006, performed a biorecon eval-
uation at the station. Under the 73a biocriteria (73a
is the Northern Mississippi Alluvial Plain ecoregion),
the maximum biorecon score is 10. The biorecon
results for the unnamed tributary to the Obion
River show 1 EPT family, 18 total families, and a
habitat score of 97. The unnamed tributary received
a biorecon score of 8 out of 10, indicating that it
now supports its fish and aquatic life use. Because
these data suggest that the unnamed tributary to
the Obion River now meets the standards for this
subecoregion, TDEC removed the stream from the
state's CWA section 303(d) list of impaired waters
in 2008.
Partners and Funding
Projects for the unnamed tributary to the Obion
River received $3,295 in funding from the
Tennessee ARCF, with additional matching funds of
$6,498. Key partners included the Chickasaw-Shiloh
Resource Conservation and Development Council,
which helped to install the dikes, and landown-
ers, who contributed most of the in-kind matching
funds.
I
«r
*
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-10-001Z
September 2010
For additional information contact:
Sam Marshall
Tennessee Department of Agriculture
sam.marshall@tn.gov • 615-837-5306
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