Measuring Success of Targeted BMP Implementation, and Getting Smarter about Ephemeral Gully Sediment...

Measuring Success of Targeted BMP Implementation, and Getting Smarter about

Ephemeral Gully Sediment and Nutrient Sources and BMPs

A. Sheshukov, R. Graber, N. Nelson, T. Keane, D. Devlin Kansas State University

2016 USDA-NIFA Project Directors MeetingWashington, DC

Project 2011-51130-31128

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Sedimentation and Soil Erosion

• Contribution of EG erosion– U.S.: 17 to 73% – Central Kansas: 42%

• EG erosion rates (in kg/m2/yr)– U.S.: 0.27 to 2.87

(1.1 to 11.9 t/ac/yr)

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Study Area• Little Arkansas River watershed (HUC-8

11030012) – 3,600 km2 in south-central Kansas– Five targeted HUC-12 subwatersheds

• Agricultural watershed– 68% cropland, 19% grazing land

• 52% of stream segments required TMDLs– Water quality concerns include bacteria, nutrients,

sediment, and pesticides (atrazine herbicide)• Drinking water source for city of Wichita and

numerous smaller cities and towns• Source for aquifer recharge

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Project Goal and ObjectivesGoal: Demonstrate that sediment & nutrient export from a watershed can be reduced by planned BMP implementation.

Objective 1 — Measure Water-Quality Success of Installed BMPs.

Objective 2 — Target New Ephemeral Gully BMPs.

Objective 3 — Educate Producers and Stakeholders.

Objective 4 — Expand Higher Education.

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• Data collection– 1m LiDAR DEM– Sub-CLU LULC layer– EG CLU-based map– 12 stream monitoring sites

• Annual surveys– 2010-15: BMP, Tillage, Crop

surveys (409 fields – 29,335 acres)

– 2012-14: EG survey

No EG; Grass waterwayEG observed

Objective 1: Water-Quality Success of Prior BMPs

Watershed Assessment

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KANSAS

Running Turkey

Dry Turkey

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Sheet & Rill Erosion• SWAT model – Field –scale results

– Top 10% fields produce 71.2% TSS yields– Top 10% fields occupy 38.3% area

• Running Turkey (undisturbed)– Area of Med-High S&R erosion – 607 ha– Average Med-High S&R erosion load – 4.4 tn/ha

• Dry Turkey (disturbed)– Area of Med-High S&R erosion – 757 ha– Average Med-High S&R erosion load – 4.2 tn/ha

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Objective 2: Target Ephemeral Gully BMPs

Location and Length of Ephemeral Gullies

• Topographic Index models– 2433 catchments in Running Turkey– 2151 catchments in Dry Turkey– 38 grassed waterways in Running Turkey– 25.1% fields had ephemeral gullies

• Compared predicted and observed gully occurrence in each catchment

• Error matrix approach for location analysis• NSE and RMSE for length analysis• Drainage density error for headwater and mainstem

gullies

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Six Topographic Index models

1. T = SAs Slope Area Index (SA)2. T = SAs

b Slope Area Power Index (SAP) 3. T = SAPLANC Compound TI (CTI) 4. T = ln(As/S) Topographic Wetness Index (TWI)5. T = 3.3nLS-1/2 Kinematic Wave (nLS) Model6. T = 3.3nLτc

-1S-1/2 Modified Kinematic Wave (nLSCSS) Model

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Topographic Index AnalysisKernel Density Estimate

Cohen’s Kappa

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Soil Erosion Risk Maps

Parameter Dry Turkey Running TurkeyArea (ha) 9,525 9,137Land under agriculture (%) 77 % 79 %Total Cropland fields 584 476Number of Cropland fields with EGs 115 109Total EG length on fields (m) 8,543 22,600Area of med-high S&R erosion (ha) 757 607Ave med-high S&R erosion load (tn/ha) 4.2 4.4

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Mgmt No-till (>10 yrs)

Crop Sorghum

Soil Silty Clay Loam

Slope 1÷3 %Area 1/8 sec

No-TillMgmt Conv-till

(>10 yrs)Crop Wheat

Soil Clay Loam

Slope 3÷7 %Area 5.2 ha

Tilled

Objective 2: Target Ephemeral Gully BMPs

Gully Surveying

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No-Till Tilled

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• Gully channels experienced fluctuations of erosion and deposition• Gully channel was net depositional, but smaller headwater gullies grew • Greatest rates of deposition at confluence of main channels, but heavy rains of spring

2015 flushed sediment • Statistics showed factors other than rainfall depth, intensity, etc. can be important

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Field Monitoring

• 3.2 acre catchment– No-till last 10 years– No contour farming– Wheat-corn-sorghum rotation– Crete silt loam soil, 1-3% slope

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Field Study of Gully Erosion

Flow7/11/2013

7/11/20149/15/2013

• EG vs. S-R erosion rates:– 2013 EG Headcut: 122 kg (0.1 tn/ha)– 2013 Sheet-Rill: 1,560 kg (1.3 tn/ha)– 2014 EG Headcut: 274 kg (0.23 tn/ha)– 2014 Sheet-Rill: 1,344 kg (1.1 tn/ha)

2013

2014

• Antecedent soil moisture prior to event extremely important• No-till needs to be complemented with other conservation

practices (Contour farming, terraces, cover crops)

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Field vs. Headcut vs. Channel Erosion• Sheet-Rill erosion by WEPP• Headcut erosion by pin-frame• Channel erosion by pin-frame and interpolation

7/11

/201

3

8/6/

2013

8/21

/201

3

9/19

/201

3

10/1

7/20

13

11/7

/201

3

4/9/

2014

5/9/

2014

5/31

/201

4

6/27

/201

4

7/11

/201

4

8/5/

2014

8/12

/201

4

9/15

/201

4

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

Sheet-Rill Headcut Channel

Soil

loss

(tn)

Sheet-Rill Headcut Channel

2013 1.29 0.08 0.092014 3.06 0.18 -0.08

Total (tn/ha) 4.35 0.26 0.01

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Numerical Model for Channel Development

Precipitation

Hard pan

Chan

neliz

ed

flow

Soil of higher drainage rate

Symmetry line

𝜕𝜃𝜕𝑡 = 𝜕

𝜕 𝑧 [𝐾 (h ) h𝑑𝑑𝑧 ]− 𝜕𝐾 (h )

𝜕 𝑧 + 𝜕𝜕 𝑥 [𝐾 (h ) h𝑑

𝑑𝑥 ]Moving boundary

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Soil water pressure: initially dry soil vs. wet soil

hinitial = - 100 cm hinitial = - 10 cm

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Soil water pressure: initially dry soil vs. wet soil

hinitial = - 100 cm hinitial = - 10 cm

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The dynamics of channel erosion

hinitial = - 100 cm hinitial = - 10 cm

Constant () Variable ()Dry soil

Variable ()Wet soil

hinitial = - 100 cm

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Channel geometryat time = 160 min

hinitial = - 100 cm hinitial = - 10 cm

Constant () Variable ()Dry soil

Variable ()Wet soil

hinitial = - 100 cm

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Channel erosion rates

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Objective 2: Target New Ephemeral Gully BMPs

Soil P Content and P Sorption on EG Field

Wedel(no-till, sorghum)

Goering(conv till, wheat)

Schmidt(no-till, wheat)

• Equilibrium P concentration (EPC0) drops quickly with depth• P desorbing from sheet-rill and adsorbing on to EG sediments • EGs contributed less P compared to topsoil sediment due to P stratification• Enrichment of surface soils eroded through sheet and rill erosion.

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P Loss with Reduction of EG Erosion

• Reducing EG erosion could decrease total P loss over 90%• However dissolved P loss could increase up to 6 times• EG BMPs should be combined with P management BMPs to fully control

dissolved P loss

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Objective 3: Educate Producers and Stakeholders

1. Quarterly WRAPS SLT meetings and presentations (2011-2016)

2. Three field days on soil health and ephemeral gullies (2014-2016)

3. JET workshop (2015)4. Continuous stream monitoring network 5. Newspaper and radio presence6. Numerous updates/reports to state &

local groups (LA BAC, SWAB, Equus Beds GMD, CD’s, etc.)

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Objectives 4: Expand Higher Education

• Trained graduate students– 2 PhD Students– 3 MS students– Several undergrad students

• Watershed and Fluvial Ecosystem Resources (WaFER) Graduate Certificate Program– Conducted employer survey to determine target professionals and jobs– Multi-disciplinary course content with involvement of three colleges– Core and specialization courses– Presently, curriculum approved but Global Campus recommended

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Products and Outcomes• Products

– SWAT model and EG-related materials– S-R erosion rates at most vulnerable fields– Locations and lengths of EGs in two HUC-12 watersheds– P-loss estimates for EG vs. S-R erosion– 6 peer-reviewed publications (2 in review)– 16 conference presentations – 3 MS theses (Coover, Stout, Sekaluvu); 1+1 PhD dissertation (Burke, Karimov)

• Outcomes– Established connection with local SLT– Increased awareness among growers including utilizing nonstructural BMP’s such as

cover crops– 3 watershed field days, workshop on Jet Erosion Test– Continuous stream sampling and field annual surveying– Off-site BMP Implementation Program approved by the city of Wichita– 2 PhD and 3 MS Students– WaFER Graduate Certificate program

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Thank You!

• Acknowledgements– Graduate students: • V. Karimov, K. Burke, J. Coover, L. Sekaluvu, B. Stout

– Watershed stakeholders and Rick Schlender– Owners of four crop fields– USDA-NIFA NIWQP for funding