U.S. Environmental
Protection Agency Region 7
Little Tarkio Creek
Holt and Atchison Counties,
Missouri
Total Maximum Daily Load
September, 2006
Approved by:
10/13/2006
Date
/s/
William A. Spratlin
Director
Water, Wetlands, and Pesticides Division
-------
Total Maximum Daily Load (TMDL)
Little Tarkio Creek
Pollutant: Sediment
Name: Little Tarkio Creek
Downstream Location: Holt County
Upstream Location: Atchison County
Hydrologic Unit Code (HUC): 10240005
Water Body Identification (WBID): 248
Missouri Stream Classification: Class P1
Beneficial Uses2:
Livestock and Wildlife Watering
Protection of Warm Water Aquatic Life
Human Health Associated with Fish Consumption
Whole Body Contact Recreation (Category B)
Secondary Contact Recreation
Size of Impaired Segment: 17.5 miles
Location of Impaired Segment3: From the Mouth to 19, 63N, 38W (refer to Table H 10
CSR 20-7)
Pollutant: Sediment
Pollutant Source: Agricultural Nonpoint Source
TMDL Priority Ranking: High
1 Class P streams maintain permanent flow during drought conditions. See 10 CSR 20-7.031(1)(F)
2 For Beneficial Uses see 10 CSR 20-7.031(l)(C) and Table H.
3 See Table H 10 CSR 20-7.
Little Tarkio Creek TMDL
2
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1. Introduction
This Little Tarkio Creek Total Maximum Daily Load (TMDL) for sediment is
being established in accordance with Section 303(d) of the Clean Water Act, because the
State of Missouri determined on the 1998 and 2002 303(d) lists of impaired waters that
the water quality standards (WQS) for Little Tarkio Creek were exceeded due to
sediment. To meet the milestones of the 2001 Consent Decree, American Canoe
Association, et al. v. EPA, No. 98-1195-CV-W in consolidation with No. 98-4282-CV-
W, February 27, 2001, EPA is establishing this TMDL.
The purpose of a TMDL is to determine the pollutant loading a waterbody can
assimilate without exceeding the WQS for that pollutant. The TMDL also establishes the
pollutant load allocation necessary to meet the WQS established for each waterbody
based on the relationship between pollutant sources and in-stream water quality
conditions. The TMDL consists of a wasteload allocation (WLA), a load allocation (LA),
and margin of safety (MOS). The WLA is the fraction of the total pollutant load
apportioned to point sources. The LA is the fraction of the total pollutant load
apportioned to nonpoint sources. The MOS is a percentage of the TMDL that accounts
for the uncertainty associated with the model assumption and data inadequacies.
2. Background and Water Quality Problems
Little Tarkio Creek is located in the Tarkio River Basin. It flows from Atchison
County to Holt County, with 17.5 miles listed as impaired. Little Tarkio Creek watershed
is approximately 178 square miles and has predominant landuse of approximately 79%
cropland and 15% grassland (Figure 1). The primary cause of the sediment impairment
to Little Tarkio Creek has been identified as pollution caused by agricultural nonpoint
sources.
Little Tarkio Creek TMDL
3
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Figure 1. Land Use Map for Little Tarkio Creek Watershed
Nodaway County
Andrew County
Land Use Map
Little Tarkio Creek
State of Missouri
Legend
States
I I Counties
¦ Cities
C3 Watershed
Impaired Segments
A USGS Gages
NPDES Outfall
~ CAFO
~ Municipal
Non-Muntopal
Land Use
I I Impervious
High Density Urban
I I Low Intensity Urban
I I Barren or Sparsely Vegetated
F"l Cropland
M I Grassland
B Dedduous Forest
¦ i Evergreen Forest
I I Mixed Forest
¦I Deoduous Woody/Herbaceous
Evergreen Woddy/Herbaceous
¦¦ Woody-Dominated Wetland
Herbaceous-Domcnated Wetland
t -I Open Water
t inch equals 513 miles
1 335 000
7/2006
PARSONS
o
All waters of the State, as per Missouri WQS, must provide suitable conditions for
aquatic life. The conditions include both the physical habitat and the quality of the water.
TMDLs are not written to address habitat, but are written to correct water quality
conditions. Because the water body addressed by this TMDL was assessed as to its
biological function, many factors may have contributed to the impairment. The state of
Missouri continues to do field evaluation and in the future, may define the role sediment
is playing in the potential biological impairment of this waterbody. However, the water
quality condition for which Little Tarkio Creek is currently listed is sedimentation;
therefore, this TMDL addresses sediment. The state of Missouri may submit and EPA
may approve another TMDL or a modified 303d listing for this water at a later time to
address new information on the impairment.
A combination of natural geology and land use in the prairie portions of the state
(where Little Tarkio Creek is located) is believed to have reduced the amount and
impaired the quality of habitat for aquatic life. The major problems are excessive rates of
sediment deposition due to stream bank erosion and sheet erosion from agricultural lands,
loss of stream length and loss of stream channel heterogeneity due to channelization, and
changes in basin hydrology that have increased flood flows and prolonged low flow
conditions. Loss of tree cover in riparian zones has caused elevated water temperatures
in summer and a reduction in woody debris, a critical aquatic habitat component in
prairie streams. The most compelling evidence of loss or impairment of aquatic habitat is
Little Tarkio Creek TMDL
4
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the historical changes in the distribution of fishes in Missouri. Many species of fish no
longer appear in portions of the state where they once lived4.
Little Tarkio Creek was placed on the Missouri 303(d) list for sedimentation.
This was primarily based on best professional judgment because little sediment data
exists to directly document sediment impacts to the stream. General fisheries data and
the effect of sediment on fish were the initial data used to consider Little Tarkio Creek for
303(d) listing. For this TMDL, sediment targets were derived using generalized
information from the ecological drainage unit (EDU).
Since the 303(d) listing, MDNR has developed a sediment protocol to determine
if sediment is actually the pollutant in the streams listed and to arrive at a standard way to
measure sediment. The first step of that protocol is a biological assessment to see if the
biological community is actually impaired. A biological assessment was not available for
this waterbody.
3. Description of Sources
3.1 Point Sources
There are five facilities with permits through the National Pollutions Discharge
Elimination System (NPDES) within the watershed (Table 1). Craig Sanitary Sewer
Lagoon is the only facility that has a discharge to a stream, with a design flow of 0.08
MGD. All other permitted facilities either land apply stormwater (Golden Triangle
Energy), do not discharge (Craig WTP and Yocum Terminal), or discharge to sanitary
| sewers (MDNR Big Lake State Park).
Table 1: Permitted facilities within Little Tarkio Creek Watershed.
Facility
Permit Number
County
Design Flow (MGD)
Yocum Terminal
MO-R240306
Holt
storm water only
Craig Sanitary Sewer Lagoon
MO-0107042
Holt
0.08
Golden Triangle Energy LL
(Outfall 01, 02 and 03)
MO-0126161
Holt
0.192, Land-applied
only
Craig WTP
MO-G640128
Holt
Non-discharging
MDNR Big Lake State Park
MO-0129259
Holt
outfall 01 - Non-
discharging
outfall 02 - discharge
to sanitary sewer
4 Total Maximum Daily Load (TMDL) Information Sheet For Streams with Aquatic Habitat Loss that are
Listed for Sediment, Missouri Department of Natural Resources, 2005,
http://www.dnr.mo.gov/env/wpp/tmdl/info/habitat-info.pdf.
Little Tarkio Creek TMDL
5
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3.2 Non-Point Sources
Agriculture dominates the watershed, extending throughout the area as well as
adjacent to the impaired segment of Little Tarkio Creek. Cropland that is adjacent to and
drains into Little Tarkio Creek, could contribute to the sediment impairment. There are
no NPDES-permitted livestock facilities in the watershed; however, there are other
livestock (Table 2). Overland runoff can easily carry sediment from these agricultural
lands into the stream. Soil from exposed land runs into the creek, increasing the turbidity
and concentration of total suspended solids and decreasing the transparency. Background
levels of total suspended solids come from natural fluvial processes. Sediment becomes
suspended during high flow events as soil along the banks is eroded and bed sediment is
resuspended. Sediment loading in Little Tarkio Creek comes predominantly from
nonpoint source pollution.
Table 2: Livestock Estimates for Holt County5
Livestock and Poultry
Animal Units
Cattle
Beef
(D)
Milk
(D)
Cow/Calf
7,407
Hogs/Pigs
9,992
Sheep/Lambs
230
Poultry
Layers
348
Broilers
780,000
(D) Withheld to avoid disclosing data for individual farms.
4. Description of the Applicable WQS and Water Quality Targets
4.1 Beneficial Uses
Little Tarkio Creek has the following beneficial uses:
Livestock and Wildlife Watering
Protection of Warm Water Aquatic Life
Human Health Associated with Fish Consumption
Whole Body Contact Recreation (Category B)
Secondary Contact Recreation
The stream classifications and designated uses may be found at 10 CSR20-
7.031(1)(C) and (F) and Table H.
Use that is impaired:
5 USDA- NASS Quick Stats (Livestock) 2002 Census of Agriculture, Volume 1 Chapter 2: Missouri
County Level Data http://www.nass.usda.gov/census/census02/volumel/mo/st29_2_001_001.pdf
Little Tarkio Creek TMDL
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Protection of Warm Water Aquatic Life
4.2 Anti-degradation Policy
Missouri's WQS include the U.S. Environmental Protection Agency (EPA)
"three-tiered" approach to anti-degradation, and may be found at 10 CSR 20-7.031(2).
Tier 1 - Protects existing uses and provides the absolute floor of water quality for
all waters of the United States. Existing instream water uses are those uses that were
attained on or after November 29, 1975, the date of EPA's first WQS Regulation, or uses
for which existing water quality is suitable unless prevented by physical problems such
as substrate or flow.
Tier 2 - Protects the level of water quality necessary to support the propagation of
fish, shellfish, and wildlife and recreation in and on the water in waters that are currently
of higher quality than required to support these uses. Before water quality in Tier 2
caters can be lowered, there must be an antidegradation review consisting of: (1) a
finding that it is necessary to accommodate important economical or social development
in the area where the waters are located; (2) full satisfaction of all intergovernmental
coordination and public participation provisions; and (3) assurance that the highest
statutory and regulatory requirements for point sources and best management practices
for non-point sources are achieved. Furthermore, water quality may not be lowered to
less than the level necessary to fully protect the "fishable/swimmable" uses and other
existing uses.
Tier 3 - Protects the quality of outstanding national resources, such as waters of
national and state parks, wildlife refuges and waters of exceptional recreational or
ecological significance. There may be no new or increased discharges to these waters
and no new or increased discharges to tributaries of these waters that would result in
lower water quality (with the exception of some limited activities that result in temporary
and short-term changes in water quality).
4.3 Narrative Criteria
General or narrative criteria contained in Missouri's Water Quality Standards
(WQS) 10 CSR 20-7.030 (3)(A)(C) and (G). These criteria state:
(A) Waters shall be free from substances in sufficient amounts to cause the formation
of putrescent, unsightly or harmful bottom deposits or prevent full maintenance
of beneficial uses;
(B) Waters shall be free from substances in sufficient amounts to cause unsightly
color or turbidity, offensive odor or prevent full maintenance of beneficial uses;
(G) Waters shall be free from physical, chemical or hydrologic changes that would
impair the natural biological community.
When the WQS is expressed as a narrative value, a measurable indicator of the
pollutant may be selected to express the narrative as a numeric value. There are many
Little Tarkio Creek TMDL
1
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quantitative indicators of sediment, such as, TSS, turbidity, and bedload sediment, which
are appropriate to describe sediment in rivers and streams6. TSS was selected as the
numeric target for this TMDL because it enables the use of the highest quality data
available, including permit conditions and monitoring data.
5. Calculation of Load Capacity
Load capacity (LC) is defined as the maximum pollutant load that a waterbody can
assimilate and still attain WQS. This total load is then divided among a Wasteload
Allocation (WLA) for point sources, a Load Allocation (LA) for non-point sources and a
Margin of Safety (MOS). The LC for this TMDL has been defined as a curve over the
range of flows for Little Tarkio Creek, see Figure 2, where the solid (red) curve is the
TMDL. Turbidity measurements were used to estimate TSS concentrations using
relationships developed by Doisey and Rabeni (2004)7. These estimates are shown in
Figure 2, where the solid (black) points are loads calculated from the estimated
concentrations and the corresponding horizontal (red) bars are percent reduction to meet
the TMDL.
Figure 2. TMDL and Percent Reduction for Little Tarkio Creek
10000
1000
>.
<0
¦u
100
10
0.1
0.01
Little Tarkio Creek Sediment Load
_ ~
1
--
»
--
1
--
Q>- Q>-
> * OO* Qy
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
& c?
t% &
O' O' °>
o
Low Row Percentile Row High Row
6 Framework for Developing Suspended and Bedded Sediments (SABS) Water Quality Criteria, U.S.
Environmental Protection Agency, EPA-822-R-06-001, May 2006.
7 Effects of Suspended Sediment on Native Missouri Fishes: A Literature Review and Synthesis, K.E.
Doisey and C.F. Rabeni, 2004, University of Missouri.
Little Tarkio Creek TMDL
8
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5.1 Modeling Approaches
In cases where pollutant data for the impaired stream is not available a reference
approach is used. In this approach, the target for pollutant loading is the 25th percentile
of the current EDU condition calculated from all data available within the EDU in which
the waterbody is located. Therefore, the 25th percentile is targeted as the TMDL load
duration curve. For a list of sites used to develop the TMDL, please refer to Appendix B,
for a full description of the development of suspended sediment targets using reference
| load duration curves see Appendix C. Table 3 translates percentile of flow to segment
flow in cubic feet per second.
Table 3. Estimated Flow for Range of Percentiles at the Impaired Segment
Outlet
Flow Estimate for Little
Percent of Flow
Discharge
(cubic feet per second)
Tarkio Creek Based on
10
4.7
Drainage Area and
30
13.9
Synthetic Ecological
50
30.3
Drainage Unit Flow
70
67.3
90
2234
6. Waste Load Allocation (Point Source Loads)
WLA is the allowable amount of the pollutant that can be assigned to point
sources. The WLA is set to the lesser of current permit limits or technology based
effluent limits (TBELs). TBELs are defined in a permit based on facility type.
Mechanical WWTFs' permit limits are a weekly average TSS concentration of 45 mg/L
and a monthly average TSS concentration of 30 mg/L. Secondary equivalent WWTFs'
permit limits are a weekly average TSS concentration of 60 mg/L and a monthly average
TSS concentration of 45 mg/L. Waste water treatment lagoon facilities' permit limits are
up to a weekly average TSS concentration of 120 mg/L and a monthly average TSS
concentration of 80 mg/L. Additionally, permits can be written to target lower limits if
the specific facility is capable of performance exceeding TBELs. Table 4 lists the
permitted point sources in the watershed and WLAs based on their current permit limits
and permitted design flows. In addition any general permits need evaluation to determine
if a site specific permit is needed to address sediment loading. Based on the assessment
of sources, point sources do not contribute to water quality impairment relative to
sediment impacts on stream biology. Thus, the WLAs are zero percentage net reduction
in sediment load. These facilities' WLAs are set at the current permit limits and
conditions. The WLAs listed in this TMDL do not preclude the establishment of future
point sources of sediment loading in the watershed. Any future point sources should be
evaluated in light of the TMDL established and the range of flows into which any
additional load will impact.
Little Tarkio Creek TMDL
9
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There are five NPDES-permitted facilities in Little Tarkio Creek watershed, but
only one of the facilities has discharge that is a potential point sources of pollution.
Because this discharge is small, it likely does not substantially impact sediment loading of
Little Tarkio Creek. The WLA is set at the current permit limits and conditions based on
the design flow of the facility and the final effluent limits for TSS, as stated in the
individual permit, see Table 4. Facilities with only storm water or land-applied discharge
are not expected to significantly contribute to the sediment impairment if they follow a
well conceived sediment control plan. BMPs should clearly be implemented as part of the
permit conditions. Therefore, the WLAs for those facilities are set to include site-specific
BMPs (Table 4).
Table 4. WLAs for NPDES-permitted facilities in Little Tarkio Creek
watershed.
Facility
Permit Number
WLA (tons/day)
d/w/m*
+- ( Formatted: Centered
Yocum Terminal
MO-R240306
site specific BMPs
Craig Sanitary Sewer Lagoon
MO-0107042
NA / 0.04/ 0.02
Golden Triangle Energy LL
(Outfall 01, 02 and 03)
MO-0126161
current permit
concentration limits
Craig WTP
MO-G640128
site specific BMPs
MDNR Big Lake State Park
MO-0129259
0/0/0
¦*- ( Formatted: Centered
*Permit limits based on current design loads where d=daily, w=weekly average, m=monthly average.
7. Load Allocation (Non-point Source Loads)
LA is the allowable amount of the pollutant that can be assigned to non-point
sources. The LA is set at 90% of the TMDL defined in Figure 2. Based on Figure 2, the
percentage of reduction in measured sediment load ranges between 4% and 97% over the
ranges of flows.
8. Margin of Safety
A MOS is added to a TMDL to account for the uncertainties inherent in the
calculations and data gathering. The MOS is intended to account for such uncertainties
in a conservative manner. Based on EPA guidance, the MOS can be achieved through
one of two approaches:
(C) Explicit - Reserve a numeric portion of the loading capacity as a separate term in
the TMDL.
Little Tarkio Creek TMDL
10
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(D) Implicit - Incorporate the MOS as part of the critical conditions for the waste
load allocation and the load allocation calculations by making conservative
assumptions in the analysis.
Available data for Little Tarkio Creek shows instances where load exceeds the
TMDL (Figure 2). To account for uncertainties in the modeling an explicit 10% MOS is
assigned to this TMDL. For example, at the flow probability of 0.7, the TMDL is
approximately 8.6 tons/day. The LA would therefore be 7.7 tons/day and the MOS
would by 0.86 tons/day.
9. Seasonal Variation
The TMDL curve represents flow under all seasonal conditions. The LA and
TMDL (expressed as concentrations) are applicable at all flow conditions, hence all
seasons. The advantage of a load duration curve approach is to avoid the constraints
associated with using a single-flow critical condition during the development of a TMDL.
Therefore, all flow conditions are taken into account for TMDL calculations.
10. Monitoring
The department conducted a biocriteria study on Little Tarkio Creek in the fall of
2005 and the spring of 2006. No future monitoring has been scheduled for Little Tarkio
Creek at this time. However, the department will routinely examine physical habitat,
water quality, invertebrate community, and fish community data collected by the
Missouri Department of Conservation under its Resource Assessment and Monitoring
(RAM) Program. This program randomly samples streams across Missouri on a five to
six year rotating schedule.
11. Public Participation
EPA regulations require that TMDLs be subject to public review (40 CFR 130.7).
EPA is providing public notice of this TMDL for Little Tarkio Creek on the EPA, Region
7, TMDL website: http://www.epa.gov/region07/water/tmdl public notice.htm. The
response to comments and final TMDL will be available at:
http://www.epa.gOv/region07/water/apprtmdl.htm#Missouri.
This water quality limited segment of Little Tarkio Creek in Holt and Atchison
Counties, Missouri, is included on the EPA approved 1998 and 2002 303(d) lists for
Missouri. This TMDL is being produced by EPA to meet the requirements of the 2001
Consent Decree, American Canoe Association, et al. v. EPA, No. 98-1195-CV-W in
consolidation with No. 98-4282-CV-W, February 27, 2001. EPA is developing this
TMDL in cooperation with the State of Missouri, and EPA is establishing this TMDL at
Little Tarkio Creek TMDL
11
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this time to fulfill the American Canoe consent decree obligations. Missouri may submit
and EPA may approve another TMDL for this water at a later time.
As part of the public notice process, MDNR assists EPA by providing a
distribution list of interested persons to which EPA will provide an announcement of the
Little Tarkio Creek TMDL. Groups that receive the public notice announcement include
the Missouri Clean Water Commission, the Missouri Water Quality Coordinating
Committee, Stream Team Volunteers in the county, county legislators, and potentially
impacted cities, towns and facilities. The EPA public noticed this TMDL from August
25, to September 25, 2006, and the Summary of Response to Comment(s) is posted on
the EPA website: http://www.epa.gOv/region07/water/apprtmdl.htm#Missouri.
12. References
Effects of Suspended Sediment on Native Missouri Fishes: A Literature Review and
Synthesis, K.E. Doisey and C.F. Rabeni, University of Missouri, 2004.
NASS Quick Stats (Livestock) Census of Agriculture, Volume 1 Chapter 2: Missouri
County Level Data, USDA 2002,
http://www.nass.usda.gov/census/census02/volumel/mo/st29 2 001 001.pdf.
Quality Assurance Project Plan for Wasteload Allocations/Special Studies, Missouri
Department of Natural Resources, 2007.
Total Maximum Daily Load (TMDL) Information Sheet For Streams with Aquatic
Habitat Loss that are Listed for Sediment, Missouri Department of Natural
Resources, 2005, http://www.dnr.mo.gov/env/wpp/tmdl/info/habitat-info.pdf.
Upper Wakarusa River TMDL (Sediment Impact on Aquatic Life), Kansas Department
of Health and Environment, 2000, http://www.kdheks.gov/tmdl/klr/UpWakaTSS.pdf
and Little Arkansas River TMDL (Sediment Impact on Aquatic Life),
http://www.kdheks.gov/tmdl/la/LittleArkSed.pdf.
13. Appendices
Appendix A - Location Map for Little Tarkio Creek
Appendix B - Source Data for Reference EDU
Appendix C - Development of Suspended Sediment Targets using Reference Load
Duration Curves
Little Tarkio Creek TMDL
12
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Appendix A: Location Map for Little Tarkio Creek
Atchison County,
'cjOimTv
1246/162
Nodaway,- .Gornty
f . ^--.^-31^
'j fJllSGS 0631 7700 |
&Z¦' N.
Little Tarkio Creek
USGS 06815575
JUSGS 0681 5555
\\ 248 j6 .3 Uj^Holt County.
1 - *'. 1^75Q.1 j A iV
f: \§/\fhodtej_
:j 248 fl .71
V i'f v s
4-B^ti Slat-V,
.A ndre w' County.
-4lUSGS 06816000
,7ti; -v
12S0 J3H]
Location Map
Little Tarkio Creek
Holt County, Missouri
Legend
| States
[ Counties
j | County with Impaired Segment
¦~Af" Impaired Segments
0 Sampling Locations
A US OS Gages
~j*v. Streams
Waterbodies
0 2 4 8
Mies
1 inch equals 3.95 miles
Little Tarkio Creek TMDL
Appendix A
-------
Appendix B
Source Data for Reference EDU
USGS stream gages used to generate synthetic flow
Platte River nr Agency 06820500
Nodaway River nr Graham 06817700
Squaw Creek 06815575
One Hundred and Two River at Maryville 06819500
USGS stream sample sites used to generate EDU TMDL
Nodaway River nr Graham 06817700
Little Platte River nr Osborn 06821065
Little Platte River nr Plattsburg 06821080
Platte River nr Sharps Station 06821190
Little Tarkio Creek TMDL
Appendix B
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Appendix C
Development of Suspended Sediment Targets using
Reference Load Duration Curves
Overview
This procedure is used when a lotic system is placed on the 303(d) impaired
waterbody list for a pollutant and the designated use being addressed is aquatic life. In
cases where pollutant data for the impaired stream is not available a reference approach is
used. The target for pollutant loading is the 25th percentile calculated from all data
available within the ecological drainage unit (EDU) in which the waterbody is located.
Additionally, it is also unlikely that a flow record for the impaired stream is available. If
this is the case a synthetic flow record is needed. In order to develop a synthetic flow
record calculate an average of the log discharge per square mile of USGS gaged rivers for
which the drainage area is entirely contained within the EDU. From this synthetic record
develop a flow duration from which to build a load duration curve for the pollutant within
the EDU.
From this population of load durations follow the reference method used in setting
nutrient targets in lakes and reservoirs. In this methodology the average concentration of
either the 75th percentile of reference lakes or the 25 th percentile of all lakes in the region
is targeted in the TMDL. For most cases available pollutant data for reference streams is
also not likely to be available. Therefore follow the alternative method and target the 25th
percentile of load duration of the available data within the EDU as the TMDL load
duration curve. During periods of low flow the actual pollutant concentration may be
more important than load. To account for this during periods of low flow the load
duration curve uses the 25th percentile of EDU concentration at flows where surface
runoff is less than 1% of the stream flow. This result in an inflection point in the curve
below which the TMDL is calculated using load calculated with this reference
concentration.
Methodology
The first step in this procedure is to locate available pollutant data within the EDU
of interest. These data along with the instantaneous flow measurement taken at the time
of sample collection for the specific date are recorded to create the population from
which to develop the load duration. Both the date and pollutant concentration are needed
in order to match the measured data to the synthetic EDU flow record.
Secondly, collect average daily flow data for gages with a variety of drainage
areas for a period of time to cover the pollutant record. From these flow records
normalize the flow to a per square mile basis. Average the log transformations of the
average daily discharge for each day in the period of record. For each gage record used to
build this synthetic flow record calculate the Nash-Sutcliffe statistic to determine if the
Little Tarkio Creek TMDL
Appendix C
-------
relationship is valid for each record. This relationship must be valid in order to use this
methodology. This new synthetic record of flow per square mile is used to develop the
load duration for the EDU. The flow record should be of sufficient length to be able to
calculate percentiles of flow.
The following examples show the application of the approach to one Missouri
EDU.
The watershed-size normalized data for the individual gages in the EDU were calculated
and compared to a pooled data set including all of the gages. The results of this analysis
are displayed in the following figure and table:
100
0.001 -I 1 1 1 1 1 1 1 1 1
0 0.2 0.4 0.6 0.8 1
1760mi2 1380mi2 - - '62.7mi2 -515mi2 log Mn
Gage
gage
area (mi")
normal Nash-
Sutcliffe
lognormal
Nash-Sutcliffe
Platte River
06820500
1760
80%
99%
Nodaway River
06817700
1380
90%
96%
Squaw Creek
06815575
62.7
86%
95%
102 River
06819500
515
99%
96%
This demonstrates the pooled data set can confidently be used as a surrogate for
the EDU analyses.
Little Tarkio Creek TMDL
Appendix C
-------
The next step is to calculate pollutant-discharge relationships for the EDU, these
are log transformed data for the yield (tons/mi2/day) and the instantaneous flow (cfs/mi2.)
The following graph shows the EDU relationship:
10
£
I 0
0
> -5
+-
c
CD
^ -10
-------
A resulting pooled TMDL of all data in the watershed is shown in the following
graph:
Enter EDU designation here - Sediment Loading
.£
>
<0
TS
<0
c
o
100
10
1
0.1
0.01
0.001
0.0001
0.00001
» O' O' O'O'
Low Row Percentile Row High Row
To apply this process to a specific watershed would entail using the individual watershed
data compared to the above TMDL curve that has been multiplied by the watershed area.
Data from the impaired segment is then plotted as a load (tons/day) for the y-axis and as
the percentile of flow for the EDU on the day the sample was taken for the x-axis.
For more information contact:
Environmental Protection Agency, Region 7
Water, Wetlands, and Pesticides Division
Total Maximum Daily Load Program
901 North 5th Street
Kansas City, Kansas 66101
Website: http://www.epa.gov/region07/water/tmdl.htm
Little Tarkio Creek TMDL
Appendix C
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