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Section 319
NONPOINT SOURCE PIMGRAM SUCCESS STORY
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Implementing Agricultural Best Management Practices Reduces Siltation
» - / .111	i Erosion on non-irrigated cropland in Tennessee's Thompson Creek
aterDOay mprOV6Q watershed contributed sediment and reduced the creek's biological
integrity. As a result, the Tennessee Department of Environment and Conservation (TDEC) added
20.2-mile-long Thompson Creek to the state's Clean Water Act (CWA) section 303(d) list of impaired waters
in 2002. To improve water quality, landowners installed agricultural best management practices (BMPs)
that included water and sediment control basins and a runoff diversion. These BMPs improved water
quality, prompting TDEC to remove Thompson Creek from the state's list of impaired waters in 2008.
Problem
Thompson Creek, TN08010203001-1300
The 20.2-mile-long Thompson Creek drains portions
of Carroll and Gibson counties and empties into
the South Fork Obion River in western Tennessee
(Figure 1). Land use in the Thompson Creek water-
shed is primarily deciduous and evergreen forest,
row crops and hay/pastureland. Numerous streams
in the South Fork Obion River watershed, including
Thompson Creek, have been affected by habitat
alteration, which has included riparian loss and
stream bank disturbances attributed to agricultural
practices.
A 2001 macroinvertebrate survey of Thompson
Creek yielded a biological reconnaissance (biorecon)
index score of poor. Biorecon is one tool used to
recognize stream impairment as judged by species
richness measures, emphasizing the presence or
absence of indicator organisms without regard to
relative abundance. The biorecon index is scored on
a scale from 1 to 15. A score of less than 5 is consid-
ered very poor. A score over 10 is considered good.
The principal metrics used are the total number of
macroinvertebrate families (or genera); the number
of families (or genera) 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 (or genera) found in a stream.
The 2001 biorecon score of poor indicated that the
creek did not support its designated uses of fish and
aquatic life because of non-irrigated crop produc-
tion. Sediment from crop production areas resulted
in a loss of biological integrity caused by siltation
and alteration in streamside or littoral vegetative
cover. Because Thompson Creek received a poor
biorecon score in 2001, TDEC added it to the state's
CWA section 303(d) list of impaired waters in 2002.
r/L reek
South EM'k Obion River
Thompson
Creek
Weakley
County
Douin
Creek
ibson
Coun
Carroll
Coun
hompspn
Cree
DeMoss Creek

ID
NRCS Code
Practice
Size of Project
1
362
Diversion
725 feet
2
638
Water and Sediment Control
1 basin
3
638
Water and Sediment Control
1 basin
0	0.5 1	2 Miles
	1	i	i	i	I	i	i	i	I
TN Dept of Agriculture
8/14/2008
Figure 1. Thompson Creek flows into the South Fork Obion River
in western Tennessee. Landowners installed several BMPs in the
watershed to control erosion.

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Bubble outlet (pipe)
collects water and
decreases its
velocity to prev ent
erosion. Water is
I then allowed to
drain gradually.
Bubble outlet and sod chute)
Figure 2. During a rainstorm, runoff drains across
this field and collects in the water and sediment
control basin seen in the background (Gibson
County, Tennessee).
Project Highlights
Local landowners installed agricultural BMPs
along Thompson Creek using funds provided by
Tennessee's Agricultural Resources Conservation
Fund, or ARCF (see Figure 1 for project locations).
The BMPs include two water and sediment control
basins and one 725-foot runoff diversion. The water
and sediment control basins help to reduce and
retain runoff, as well as trap sediment (Figure 2).
The runoff diversion channels water across a slope
and away from sensitive habitat areas. The channel
ends at a bubble outlet (perforated pipe), which
slows the runoff and releases it gradually to reduce
the velocity of the flow across the ground surface
(Figure 3). A sod chute below the outlet helps to
stabilize the soil and prevent soil erosion.
Figure 3. Water in the runoff diversion channel exits
slowly through a perforated pipe and drains through
the sod-covered areas (the squares of sod shown in
the photo will eventually grow together).
Results
The combination of BMPs installed by landowners
decreased siltation and improved water quality
in Thompson Creek. In 2006 TDEC performed a
biorecon evaluation along Thompson Creek at
mile 3.0 (Highway 105). The results showed three
EPT families, two intolerant families and 13 total
families. The stream received a biorecon score of
11 (good) with a habitat score of 106, indicating
that it now supports its fish and aquatic life use. On
the basis of these data, TDEC removed Thompson
Creek from the state's CWA section 303(d) list of
impaired waters in 2008.
Partners and Funding
Projects for Thompson Creek received $10,619 in
funding from the Tennessee ARCF. with additional
matching funds of $3,540. Key partners include
the soil and water conservation district offices
of Gibson and Carroll counties for offering BMP
assistance and landowners for contributing most of
the in-kind matching funds.
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-F-10-001AA
September 2010
For additional information contact:
Sam Marshall
Tennessee Department of Agriculture
sam.marshall@tn.gov • 615-837-5306

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