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WIND EROSION EQUATION Recent Changes (NAM) USDA-NRCS. Wind Erosion continues to be a serious problem in the semiarid and arid regions of the US. The Good Old Days. The Good Old Days cont. WEQ Changes made!.

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Wind Erosion continues to be a serious problem in the semiarid and arid regions of the US.

weq changes made
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.
introduction weq excel spreadsheet
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
spreadsheet history
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
circular 2 changes
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)
adjustments to i
  • Irrigation adjustment (IF)

-adjustment applies to all soils

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
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.
krr random roughness factor13
  • 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)
ridge roughness krd
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
irrigation input requirements
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
circle irrigation
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

field width
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.
field width vs unsheltered distance20
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.
computer requirements
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
instr sheet
INSTR sheet
  • Wind Erosion Model Worksheet Legend


  • Describes input data and column headings
  • New-Krd, Krr, IF, No. of Irr, and TWF

Read this sheet first.

res wks sheet required inputs
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)
calc sheet
Calc sheet
  • Detailed calculations by Mgt Period
  • Note Krd, Krr, and IF factors added here
  • No inputs needed or allowed
data tables
Data Tables
  • Crop table

-Need to maintain crop data;

residue produced and green growth

  • Tillage table

-Residue reduction

-Random roughness assigned to tillage

data tables cont
Data Tables cont.
  • Climate data, the wind direction, EWE, and Preponderance must be added for climate stations in your state.
  • 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.
  • 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).
  • Growth curve data is limited
  • Do not have SGe curves for all crops both green and dry
where to get more information
Where to get more information
  • Call State Agronomists for assistance:
  • State Agronomists can call:

Mike Sporcic, , 505-761-442


where to get more information31
Where to get more information
  • Gary Tibke– (785)537-5541

  • Lorenz Sutherland--(719)384-5408
  • Websites for WEQ or

We’re Done