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I NONPOINT SOURCE SUCCESS STURY
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Bacteria and Turbidity Levels in Curl Creek are Reduced through
Voluntary Agricultural Conservation Programs
Waterbody Improved
Elevated bacteria arid turbidity leveis resulted in the impairment
of Curl Creek and placement on Oklahoma's Clean Water Act
(CWA) section 303(d) list of impaired waters in 2004. Grazing and hay production contributed to
these impairments, and implementation of conservation practice systems (CPs) to promote better-
quality grazing lands decreased bacteria and turbidity levels in the creek. As a result, Curl Creek was
removed from Oklahoma's 2010 CWA 303(d) list for Escherichia coli and from the 2012 CWA 303(d)
list for turbidity. Curl Creek now partially supports its fish and wildlife protection (FWP) and primary
body contact (PBC) beneficial uses.

Problem
Curl Creek is a 17.27--ml!e stream that flows through
Nowata and Washington counties in Oklahoma before
discharging to the Caney River (Figure 1). Land use
in the 30,896-acre watershed is primarily grasslands
(83 percent of total) for beef cattle and hay produc-
tion. About 5 percent of the watershed is developed
land (primarily for highways and roads), 13 percent is
forested, and less than 1 percent is cropland.
Grazing and hayland management contributed to
excess bacteria and turbidity in Curl Creek. It was
listed as impaired for turbidity in 2004 when 20 per-
cent of assessed baseflow turbidity samples violated
Oklahoma water quality standards. An Oklahoma
stream is considered to violate the turbidity standard
when more than 10 percent of baseflow samples are
higher than 50 nephelometric turbidity units (NTU).
Curl Creek was also listed for E coli bacteria in 2004
when 20 percent of individual samples violated the
individual sample maximum of 406 colony-forming
units per 100 milliliters of water (CFU/100 mL) during
the recreation season. In 2004 the PBC designated use
was considered impaired if more than 10 percent of
individual samples violated the sample maximum. In
2008 the assessment method changed and streams
were considered to be violating the standard If
the geometric mean during the recreation season
exceeded 126 CFU/100 ml_ for E. coli. On the basis of
these assessment results, Oklahoma added Curl Creek
(OK121400010270_00) to the 2004 303(d) list for
nonattainment of the FWP and PBC beneficial uses.
4"
Legend
• Monitoring Sites
* I
Oklahoma City

open water
open space development
low density development
| forested
grasslands
| pasture/hay lands
| crop lands
Figure 1. Curl Creek is in northeastern Oklahoma.
Project Highlights
Landowners in the watershed worked with the Nowata
County and Caney Valley Conservation Districts,
the U.S. Department of Agriculture (USDA) Natural
Resources Conservation Service (NRCS), and the
Oklahoma Conservation Commission (OCC) to imple-
ment CPs through Oklahoma NRCS's Environmental
Quality Incentives Program (EQIP), Conservation
Stewardship Program (CStwP), and general conserva-
tion technical assistance program, as well as through
the OCC's Locally Led Cost-Share Program (LLCP).
From 2004 to 2012, landowners improved grasslands,
pasture, hay meadows, and cropland, which reduced
runoff of sediment and other pollutants by decreasing
erosion and better using available grazing lands. From
2012 to 2017, landowners installed additional CPs that
helped to maintain improved water quality. Many

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Table 1. CPs installed in the watershed (2004-2017).
Notes: ac = acres; ft = feet
CPs were installed during both time periods (Table 1).
Some targeted CPs were installed only between 2004
and 2012, including critical area planting (1 acre [ac]),
upland wildlife management (83 ac), forage harvest
management (155 ac), heavy use area protection
(2 ac), and riparian forest buffer (28 ac). CPs installed
only between 2012 and 2017 included animal trails and
walkways (33 feet), split nitrogen application (171 ac),
better grazing management (461 ac), precision spray-
ing (1,165 ac), livestock watering pipeline (835 ac), and
rotation of supplement/feeding areas (583 ac).
Results
Through its statewide nonpoint source Rotating Basin
Ambient Monitoring Program, the OCC documented
improved water quality in Curl Creek due to landown-
ers implementing CPs. The CPs decreased erosion and
reduced turbidity and bacteria loading. Monitoring
data compiled for the 2004 Integrated Report showed
excessive turbidity in Curl Creek (when 20 percent of
baseflow samples exceeded 50 NTU). By 2012, turbid-
ity values had decreased such that fewer than 10 per-
cent of samples exceeded 50 NTU; this decreasing
trend has continued (Figure 2). In 2004, E. coli bacteria
violated state standards when 29 percent of samples
were higher than the individual sample maximum of
406 CFU/100 mL. In 2008, when standards assess-
ment was modified to consider the geometric mean,
the creek's value of 151 CFU/100 mL still exceeded
the criteria of 126 CFU/100 mL. However, by 2010,
the geometric mean during the recreation season had
dropped to 84 CFU/100 mL. It has remained support-
ing through 2016 (Figure 3).
On the basis of these data, Curl Creek was removed
from the Oklahoma CWA section 303(d) list for E. coli
in 2010 and for turbidity in 2012. This change resulted
in partial support of its FWP and PBC beneficial uses.
Monitoring in Curl Creek will continue in order to track
progress towards full support of these beneficial uses.
Partners and Funding
The OCC monitoring program is supported by the
U.S. Environmental Protection Agency's (EPA) CWA
section 319 funds at an average annual statewide
cost of $1 million. Approximately $500,000 in EPA 319
funds support statewide water quality educational
efforts through Blue Thumb. Working in partner-
ship with local conservation districts, NRCS supplied
approximately $525,000 for implementation of CPs in
the watershed through NRCS EQIP. The LLCP provided
$15,517 matched by $23,824 from landowners. A
large number of practices were funded by landowners
based on recommendations through NRCS general
technical assistance and conservation planning.
Practice type installed
Amount
2004-2012
2012-2017
Contour farming (ac)
80
80
Integrated pest management (ac)
3,258
1,120
Prescribed grazing (ac)
2,978
4,054
Forage and biomass planting (ac)
155
23
Watering facility
1
1
Cross fencing (ft)
1,190
18,802
Brush management (ac)
2,226
2,103
Ponds
6
11
Nutrient management (ac)
184
23
Herbaceous weed control (ac)
1,023
3,684
Curl Creek Turbidity
% exceedance: 20% 22% 21% 12% 9.5% 6%
760.00
i
I 40.00
5
20.00
0.00
I I
~ ~ ~ ~
2004 2006 2008 2010 2012 2014 2016
Figure 2. Turbidity decreased in Curl Creek as
producers focused on improving pasture management.
Curl Creek E. coli
Maximum -
Exceeds - 20%
Geomean -
1000
£ 900
§ 800
±!	700
s
M	600
E
E	500
o
>	400
.2	300
rr	200
® 100
Uj
II
2004 2006 2008 2010 2014 2016
Figure 3. E. coli decreased as pasture conditions improved.
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-F-17-001J
August 2017
For additional information contact:
Shanon Phillips
Oklahoma Conservation Commission
405-522-4500 • shanon.phillips@conservation.ok.gov

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