Unit Source Area Monitoring with Grade Control Pipe

InstrumentationSeth Dabney, Glenn Wilson, J.R. Rigby, and James Bonta

USDA-ARS National Sedimentation Laboratory

Oxford, MS, US

Goodwin Creek Experimental Watershed•Area - 21.3 sq. km

•Operation 1981-pres.•Instrumentation:

30 rain gauges13 supercritical flumes5 pump sampler sites3 edge-of-field sites

Land Use Change by Decade

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Fractio

n of W

atershed

 Area

Year

Grassland

Forestland

Cropland

Edge-of-field sample locations

Timber 29 acres

Cropland 3 acres

Pasture 11 acres

Station #2 4420 acres

Primary Research Objectives

• Assess hydrologic, sediment, and turbidity responses to land management and scale.

Instrument “sled” fabricated from stainless steel, slips into grade control pipe

Turbidity

Sampler intake

Depth and velocity

Weir

y = 1.035xR² = 0.982

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Discharge from

 Con

tinuity (cfs)

Discharge from V Notch Weir (cfs)

1 on 1

+‐10%

1.5% Slope

3.5% Slope

5.5% Slope

Linear (all data)

Station #16 Cropland

Station #16 Cropland

Station 15 Forest / Timber

Station #17 Pasture

Station #17 Pasture

Supercritical grade control flumeStation #2 (as built)

Turbidity gauge deployed on a strut from catwalk at Station #2

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6/12/2014 19:12 6/12/2014 21:36 6/13/2014 0:00 6/13/2014 2:24 6/13/2014 4:48 6/13/2014 7:12 6/13/2014 9:36 6/13/2014 12:00

Trub

idity

 (mV)

Discharge (cfs)

Discharge fines Turbidity

y = 7.028x ‐ 501R² = 0.980

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Fine

s Con

centratio

n (ppm

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Turbidity (mV)

Station #2, 12‐13 June 2014 

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Feb-82 Aug-87 Jan-93 Jul-98 Jan-04 Jul-09

Fine

s C

once

ntra

tion

(ppm

w)

Date

Dec to Mar

Aug to Nov

Apr to Jul

Four-month average concentrations of sediment < 53 µm at Station 2

CEAP

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6/12/2014 19:00 6/12/2014 21:24 6/12/2014 23:48 6/13/2014 2:12 6/13/2014 4:36 6/13/2014 7:00 6/13/2014 9:24 6/13/2014 11:48

Concen

tration (ppm

)

Discharge (in

/hr) and

 Sed

imen

t Disc

harge (to

ns/acre ho

ur)

Discharge

Fine Sediment Discharge

Concentration of Fines

Fines Sample Concentration

y = 3.4468x ‐ 71.889R² = 0.9353

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Fine

s Con

centratio

n (ppm

)

Average Turbidity (mV)

Station 15, 16, 17 combined

Station 17

Station 15

Station 16

Linear (All Data)

y = 7.0275x ‐ 501.01R² = 0.9803

y = 3.4468x ‐ 71.889R² = 0.9353

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Fine

s Con

centratio

n (ppm

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Average Turbidity (mV)

Edge of Field Sites and Station 2

Station 2

Edge of Field Sites

Linear (Station 2)

Linear (Edge of Field Sites)

4 % of sediment from upland sources

96% of sediment from gully and

channel erosion

Station Drainage Area (acres) Drainage Area (sq_ft) NOTES1 5266.8 2294218082 4421.6 1926048963 2145 934362004 893.7 389295725 1033.3 4501054813 303.4 1321610414 411.9 1794236415 28.859 1257098 Original estimate for Andrea Bowen's work16 2.87 125017 This is an estimate based on Darlene's work with an area removed by Mick Ursic based on what is known from the field.17 11.01 479595.6 This is an estimate from Darlene's work

April 2005 Simon site

2006

1513

14

3

4

2

Steady Pond Construction

y = ‐0.0145x2 + 58.82x ‐ 59375R² = 0.9947

y = 0.4192x ‐ 811.18R² = 0.9877

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Pond

 Surface Area (ha)

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ber o

f Pon

ds

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NumberArea

Conclusions

Instrumentation to measure depth, velocity and turbidity, sample runoff, and quantify sediment yield from grade control conduits was described.

Turbidity was well correlated with concentrations of sediment <53 µm.

Runoff from cropland and grassland areas was flashier than from a timberland source areas.

Analysis suggests that most (>90 %) sediment originated from channel and gully sources.

QUESTIONS?

y = 0.911xR² = 0.977

y = 0.204xR² = 0.298

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Fine

s sed

imen

t con

centratio

n (ppm

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Total sediment concentration (ppm)

Station #15Station #16Station #17uplandStation #2Linear (upland)Linear (Station #2)