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Best Management Practices Improve Water Quality and Benefit
Ranchers in North-Central Wyoming Watershed
Waterbody Improved Historic §raz'n§ practices resulted in degraded range land
conditions, stream channel instability, and poor stream biological
condition within the Grass Creek/Cottonwood Creek watershed in north-central Wyoming. The
Nature Conservancy (TNC) worked with ranchers and numerous other partners to implement
best management practices (BMPs) throughout the watershed to improve ranching operations
and promote rangeland, riparian and stream health. Data collected by TNC and partners indicate
that rangeland, riparian and stream biological conditions have continued to improve since project
implementation.
Problem
A 2007 Wyoming Water Development Level I
Watershed Management Study of the Grass Creek/
Cottonwood Creek watershed in the Big Horn Basin of
Wyoming concluded that intensive cattle and sheep
grazing in the late 1800s degraded rangeland condi-
tions (Figure 1). Although improved range manage-
ment over time led to some areas recovering from
these historic impacts, others remained degraded.
In particular, riparian zones and stream channels
remained degraded as a result of historical and current
disturbances from wildlife and livestock that con-
centrate in these areas for water, food and cover. In
addition, a history of fire suppression caused conifer
encroachment into aspen stands and riparian areas,
and noxious weed infestations degraded range and
riparian areas. Findings from water quality monitoring
completed by Wyoming Department of Environmental
Quality (WDEQ) in the late 1990s and mld-2000s
indicated streams were experiencing incision, bank
erosion, sedimentation, degraded riparian vegetation
and poor biological conditions.
Story Highlights
A Coordinated Resource Management group of
proactive stakeholders was formed in 2004 to address
resource concerns, interest in developing range moni-
toring programs prompted TNC to work with ranches
and other partners to coordinate broader watershed
restoration efforts that would improve range condi-
tions, wildlife habitat and water quality. As part of

Grass Creek/Cottonwood Creek Watershed, Wyoming
[ prospect C reek"
[^gSnhound'creeK]
Grass Creek/Cottonwood
Creek Watershed
WYOMING
Legend
Streams
C3 12-Digit Hydrologic Unit Boundary
20 Miles
Figure 1. Map of the Grass Creek/Cottonwood Creek watershed
and major project area streams.
this effort, TNC received Clean Water Act (CWA)
section 319 funding to implement BMPs to achieve
water quality restoration goals. TNC and partners
implemented the CWA section 319 project over three
phases and accomplished an impressive amount of
work between 2008 and 2016. Partners completed a
total of 30 off-channel water development projects,
including installation of 47 water tanks, to improve
livestock and wildlife distribution on more than 14,000
acres of rangeland whiie also reducing pressure on
riparian areas. Over 80 acres were protected through

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14 riparian, spring development and aspen stand
exclosures. Conifer encroachment and noxious weed
treatment, aspen stand regeneration, and willow and
cottonwood plantings occurred on over 600 acres. In
addition, over 20 miles of wildlife-unfriendly fencing
was taken down over the course of the project.
Results
Installing BMPs resulted in estimated reductions of
217 tons/year of sediment, 2,000 pounds (lbs)/year of
nitrogen and 270 lbs/year of phosphorus from over-
land runoff in the watershed. Moreover, an estimated
reduction of 1,479 tons/year of sediment from exces-
sive stream bank erosion throughout much of Grass,
Lefthand and Little Grass creeks had also been accom-
plished as a result of BMPs. Range monitoring indi-
cated improving trends in desirable plant species with
accompanying decreases in shrubs and bare ground
areas as a result of implemented BMPs. Water quality
monitoring revealed a coarsening of stream substrate
over time as well as an overall improving trend In
biological condition with respect to diversity and
abundance of sensitive aquatic macroinvertebrates
(Figure 2). The project also resulted in benefits to
livestock operations, Including Improved management
efficiency, better utilization of upland forage, secure
water sources, and wildlife-friendly fences requiring
less maintenance.
Partners and Funding
This project has been exemplary in its proactive
approach to addressing watershed degradation
through implementation of diverse BMPs, its focus on
finding solutions that benefited livestock operations
in addition to natural resources, its documentation
of benefits through monitoring, and its success-
ful coordination of numerous partners. Partners
included LU Ranch, Hi 11 berry Ranches, Hot Springs
Weed & Pest, Marathon Oil, Round River Conservation
Studies, Wyoming Conservation Corps, volunteers
from the general public, WDEQ, Wyoming Game
and Fish Department, Wyoming Department of
Agriculture, Wyoming Wildlife and Natural Resource
Trust, University of Wyoming Extension, Wyoming
Honor Farm, Natural Resources Conservation
Service, Wyoming State Forestry, and Bureau of Land
Management. TNC's leadership In this project was criti-
cal to its success. A total of $433,482 in CWA section
319 funds and $289,640 In state/private funds were
expended on this project.
GC1 Substrate Composition over Time
100%
90%
¦2010
•2011
80%
¦2012
70%
•2013
¦2014
60%
¦2015
50%
40%
30%
20%
10%
0%
rO
up
rvl
o
CT) 
O O O
Lfi
00
Substrate Size (mm)
Figure 2. The substrate composition in the Grass Creek/Cottonwood
Creek watershed has grown coarser over time.
^tDST:%
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PRO^°
s
©
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-F-18-Q01BB
October 2018
For additional information contact:
Jennifer Zygmunt
Wyoming Department of Environmental Quality
307-777-6080 • jennifer.zygmunt@wyo.gov

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