WIND EROSION EQUATION Recent Changes (NAM) USDA-NRCS

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WIND EROSION EQUATIONRecent Changes
(NAM)USDA-NRCS
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• Wind Erosion continues to be a serious problem in
  the semiarid and arid regions of the US.

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The Good Old Days
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The Good Old Days cont.
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WEQ Changes made!

• WEQ has been updated to account for irrigation
  effects, random roughness and I Factor
  adjustments.
• WEQ changes are outlined in the new edition of
  the National Agronomy Manual.

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Introduction WEQ Excel Spreadsheet

• Cover NAM changes
• Changes to Ridge Roughness
• Addition of Random Roughness
• Quick intro to the Excel spreadsheet
• Demo how to edit and make changes
• Answer Questions

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Spreadsheet History

• Began as a spreadsheet by Tom Keep
• Then Circular 2, NAM amendment Sept. 12, 1997 was
  incorporated
• SGe calculations added, 1998
• Krd-Ridge Roughness formulas added in 1998

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Circular 2 Changes

• I Adjustment for Irrigation
• -Above 180 no adjustment
• -180 or less, reduce one I class
• IF Irr. Factor reduces Erosive Wind Energy
  (EWE) for mgt period
• Random Roughness (Krr) combined with Ridge
  Roughness (Krd)

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ADJUSTMENTS TO I

• Irrigation adjustment (IF)
• -adjustment applies to all soils

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EWE IRRIGATION ADJUSTMENT

• Effects of wet soil is accounted for by adjusting
  the EWE for the mgt period
• Bare wet soil remains non-erodible wet
• 1 day for coarse textured soils
• 2 days for medium textured soils
• 3 days for fine textured soils
• See sheet WEG tab for table

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ADJUSTMENTS TO I - IRRIGATION
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Krr RANDOM ROUGHNESS FACTOR

• Soil cloddiness raises the threshold wind speed
  at which erosion begins
• Provides sheltered area among clods where moving
  soil can be trapped
• Spreadsheet reduces RR (clodsize) by one half
  after 15 days.

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Krr RANDOM ROUGHNESS FACTOR

• Non-oriented surface roughness
• Cloddiness
• Usually created by tillage implements
• Values represented as standard deviation, in
  inches, of roughness heights
• Use Random Roughness-Guidance sheet
• Roughness assigned to each tillage implement
  (ideal conditions)

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Random Roughness - Krr
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Ridge Roughness- Krd

• Revised NAM has new tables
• Based on I values and Preponderance
• Low Preponderance values indicate less of the
  erosive wind is from the prevailing wind
  direction.
• Higher Krd values indicate that ridges are less
  effective
• Krd can be lower than 0.5 now

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Irrigation Input Requirements

• Enter the number of Irrigations, including
  pre-plant and post harvest irrigation
• Non-erodible wet days will be calculated based
  on soil texture (WEG)
• Drip irrigation poses a problem. Need to
  estimate the of surface that is non-erodible
  wet

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Circle Irrigation
The soil texture determines the number of
non-erodible wet days (1,2,or 3) per irrigation
It takes this system 96 hours to make one
complete circle. For WEQ this is one irrigation.
Day 3-24 hrs
Day 4-24 hrs
Day 1-24 hrs
Day 2-24 hrs
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Field Width

• With the WEQ Speadsheet, field width is the
  distance across the short side of the field or
  average short side of a polygon.

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Field Width vs Unsheltered Distance
Field Width
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Field Width vs Unsheltered Distance

• The Excel Spreadsheet model will determine L
  using the length/width ratio of the field, the
  angle of deviation, wind preponderance and the
  resulting wind erosion direction factor.

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Computer Requirements

• Need 486 minimum.
• 586 is better
• Windows 95, 98, or NT
• Excel version 7.0
• 16 mg of RAM or better
• File name WEQvs8.01.xls

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INSTR sheet
Read this sheet first.

• Wind Erosion Model Worksheet Legend
• -Definitions
• Describes input data and column headings
• New-Krd, Krr, IF, No. of Irr, and TWF

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Res WKS sheetRequired Inputs

• Operation Dates
• Crop Names
• Operations
• Percent Flat Residue
• Number of irrigation per mgt period
• Yield adjustment
• Prod., Farm, Tract, Field, C, I, Field Width, LW
  ratio, Tillage Dir, Field Dir, Irr (y/n)

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Calc sheet

• Detailed calculations by Mgt Period
• Note Krd, Krr, and IF factors added here
• No inputs needed or allowed

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Data Tables

• Crop table
• -Need to maintain crop data
• residue produced and green growth
• Tillage table
• -Residue reduction
• -Random roughness assigned to tillage

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Data Tables cont.

• Climate data, the wind direction, EWE, and
  Preponderance must be added for climate stations
  in your state.

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Summary

• If Users have a basic understanding of the EXCEL
  spreadsheet, they can use this model.
• State Agronomist should become familiar with the
  wind data (climate file), crop data, and
  operation (tillage) files before beginning use in
  a new state.

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Limitations

• We can not change tillage direction in each mgt
  period.
• Need to create templates and save for later use.
• It does not allow for crusting (no I factor
  adjustment for a period of crusting).

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Limitations

• Growth curve data is limited
• Do not have SGe curves for all crops both green
  and dry

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Where to get more information

• Call State Agronomists for assistance
• State Agronomists can call
• Mike Sporcic, michael.sporcic_at_nm.usda.gov ,
  505-761-442
• or,

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Where to get more information

• Gary Tibke [phone]
• tibke_at_weru.ksu.edu
• Lorenz Sutherland--[phone]
  lorenz.sutherland_at_co.usda.gov
• Websites for WEQ www.nm.nrcs.usda.gov/techserv
  or www.weru.ksu.edu/nrcs

Were Done
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Questions Short Demo END
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The End