Section 319
NONPOINT SOURCE PROGRAM SUCCESS STORY
BMPs Reduce Sediment and Restore Streams /
Waterbodv Improved Surface runoff from irr'9ated agriculture areas and poorly
1 "' * ^ designed water conveyance features caused erosion and
threatened the aquatic life uses of North Fork Shell Creek and South Fork Shell Creek
in northeastern Wyoming. The sediment issues prompted the Wyoming Department of
Environmental Quality (WDEQ) to place both streams (16.69 miles total) on the state's 2000
Clean Water Act (CWA) section 303(d) list of impaired waters as threatened for not support-
ing their aquatic life uses. In response, the Lake DeSmet Conservation District (LDCD) and
landowners implemented best management practices (BMPs), including updating irrigation
techniques, improving water conveyance and constructing sediment detention wetlands.
Subsequent WDEQ monitoring confirmed that the activities improved irrigation efficiency
and diminished sediment input to the creeks. As a result, WDEQ removed the two streams
from the Wyoming 2008 CWA section 303(d) list of impaired waters.
Problem
The headwaters of Wyoming's North Fork Shell
Creek and South Fork Shell Creek (Figure 1) are
in the Powder River basin (Figure 2), along the
foothills of the east slope of the Bighorn Mountain
Range. The creeks flow northeast into Shell Creek
Reservoir near the town of Story. The two forks of
Shell Creek are protected for agricultural, industrial,
recreational, wildlife, scenic value and aquatic life
(other than fish) uses.
Data collected by the LDCD in 2000 indicate that
the aquatic life (other than fish) use for the streams
was threatened because of sedimentation from
habitat degradation related to irrigation diversions
and conveyance. On the basis of that data, WDEQ
added a total of 16.69 miles of the north and south
forks of Shell Creek to the 2000 CWA section 303(d)
list of impaired waters for habitat degradation.
Project Highlights
Several landowners and LDCD implemented
multiple BMPs between 1999 and 2001 using fund-
ing from a CWA section 319 grant to address the
habitat issues affecting the two watersheds. BMPs
included replacing surface ditches with buried
pipelines, changing inefficient flood irrigation to
center pivot irrigation, constructing wetlands and
upgrading water conveyance control structures.
LDCD monitored the macroinvertebrate commu-
nity, water quality, and in-stream habitat in both
Figure 1. Photographs showing the North Fork (top)
and South Fork (bottom) of Shell Creek.
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Powder River Watershed
North Fork Shell Creek
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, Miles
Figure 2. This map shows the impaired portions of North Fork Shell
Creek and South Fork Shell Creek. These creeks are headwaters of
Wyoming's Clear River watershed (HUC 10090206), a tributary of
the Powder River.
waterbodies to assess how effectively the BMPs
mitigated sedimentation.
Results
LDCD's macroinvertebrate and in-stream habitat
surveys show a positive change in silt depth that
corresponds to BMP implementation. LDCD also
collected water quality data that show total sus-
pended solids, turbidity and temperature levels
decreased. However, LDCD had to classify the data
as inconclusive because it believes that a severe
drought in 2000 and 2001 might have confounded
study results. In 2005 and 2006 WDEQ conducted
an additional field assessment, which indicated that
the BMPs had mitigated irrigation and water convey-
ance issues. WDEQ found that macroinvertebrate
samples from both forks were comparable to the ref-
erence stream and therefore assigned a rating of full
support of aquatic life using the Wyoming Stream
Integrity Index and the River Invertebrate Prediction
and Classification System. On the basis of those
findings, WDEQ removed North Fork Shell Creek
and South Fork Shell Creek (a total of 16.69 miles)
from the Wyoming 2008 CWA section 303(d) list of
impaired waters.
Partners and Funding
LDCD received a total of $178,743 in CWA section
319 funding along with $285,687 of in-kind match-
ing funds. LDCD partnered with several landowners
to implement BMPs and monitor project results
at various locations throughout each of the two
watersheds.
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-09-001AA
September 2009
For additional information contact:
Richard Thorp
Wyoming Department of Environmental Quality
307-777-3501 • rthorp@wyo.gov
Nikki Lohse
Lake DeSmet Conservation District
307-684-2526 ext. 3 • Nikki.lohse@wy.nacdnet.net
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