ABE 527 – WEPP Laboratory 1

 

  1. Publicly available NSERL and WEPP information and software:
    1. Open Internet Explorer or Netscape
    2. Connect to: http://topsoil.nserl.purdue.edu
    3. To reach the WEPP information, click on the “Software” link
    4. From the list of software, select the “WEPP” link.
    5. Examine the available documentation and software links. This page is where one would come for the most up-to-date WEPP info. The current direct URL for this page is: http://topsoil.nserl.purdue.edu/nserlweb/weppmain/wepp.html
  2. Web-browser interface for WEPP – ARS (Agricultural & Rangeland applications)
    1. From main FS page click on ARS link, or from the NSERL WEPP page, click on “A Web-browser interface to WEPP model” link or enter the direct URL; http://octagon.nserl.purdue.edu/weppV1
    2. The ARS WEPP browser interface allows simulation of a single hillslope profile for cropland or rangeland management, or a worksheet with a list of managements that can be chosen for a location, soil and slope configuration. Select to run a single hillslope simulation for cropland conditions.

 

    1. Conduct a simulation with the interface. For example, first try a 1 year simulation for West Lafayette, Indiana, 120 ft. long S-shaped slope, average steepness 10%, Miami silt loam soil, and corn-fall moldboard plow management. Examine the text and graphics outputs. If the tolerable soil loss (T) value for this soil is 2 tons/acre/year, is there a problem with the current management? Do you think that a 1 year simulation period is adequate to assess long-term average annual soil loss? Rerun the simulation for longer periods (5, 10, 20 or 30 years) and record the results – what happens to the average annual soil loss value? Why?

 

Run

# Years

Avg. Annual Precip (in)

Avg. Annual Runoff (in)

Avg. Annual Soil Loss (t/A)

Avg. Annual Sed. Yield (t/A)

1

1

 

 

 

 

2

2

 

 

 

 

3

5

 

 

 

 

4

10

 

 

 

 

5

20

 

 

 

 

6

30

 

 

 

 

 

    1. Click on the “Cropland Worksheet” option at the top of the screen. In this view you have all of the available managements to choose from, and can make comparative simulation runs for a single location, soil, and slope shape. Conduct a set of 10 year simulations in the worksheet for Indianola, Iowa, for an 86 ft long, S-shaped profile with an average 5% slope and a Monona silt loam soil. Report the simulation results in terms of average annual runoff, soil loss and sediment yield. If the tolerable soil loss value for this soil was 5 tons/acre/yr, what management practices would be recommended?

 

e.   The browser interface can also be used to examine the impact of filter strips and buffer strips on a hillslope profile. Click on the “WEPP Cropland” option at the top of the screen, then under additional tools select “Filter Strip”. This option will set up a simulation with 2 OFE’s – a top strip (typically conventionally cropped), and a bottom strip (typically shorter with permanent vegetative cover). Filter strips can be used to decrease the amount of sediment predicted to travel off-site of a field.

 

For this exercise, simulate a field location in Moorhead, MS on an Alligator silt loam soil. The slope is convex with an average steepness of 5% and a total length of 125 ft. The normal management on the profile is a soybean crop under a fall mulch till system. Conduct 10 year model simulations. What is the predicted soil loss with no filter strip? What is the effect of adding a 10 ft. filter strip at the bottom in permanent grass vegetation? If the sediment yield from this field must be reduced to 6 ton/A/yr, what is the minimum grass filter strip length? Is the use of a filter strip practical as a sediment control practice for this field? Explain.

 

Run

Grass Strip Length (ft)

Avg. Annual Precip (in)

Avg. Annual Runoff (in)

Avg. Annual Soil Loss (t/A)

Avg. Annual Sed. Yield (t/A)

1

0

 

 

 

 

2

10

 

 

 

 

3

 

 

 

 

 

4

 

 

 

 

 

5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  1. WEPP Windows interface for hillslope applications
    1. Exit the Web-browser. Follow the class instructors to start up WEPP on your PC. You will need to specify a location for the WEPP files to be stored, either C:\TEMP or somewhere on your personal account (~50 Mbytes space required).

    1. For this class we will go through the Windows interface basics, then do some fairly simple hillslope exercises. In the next lab period, we will go into the watershed options, and do some more complex activities.
    2. From the Start menu, in Programs, under ABE software select “WEPP Interface”. You will be prompted to select a working directory – one option would be C:\TEMP (if you select this, the program will run faster, but any new runs, data, etc. will be lost after logging off). You can also select a directory on your personal account (program may run slower, but new info will be retained on your account).
    3. Once the WEPP program comes up, a Welcome screen will appear. You can select from several options, or can make this screen disappear permanently. Choose to “Use the default WEPP project”, then click on the “Start Task” button.

 

 

    1. The WEPP model will run for a default situation – a nonuniform profile, on a Duncanon soil, continuous corn fall plow management, near Des Moines, Iowa for a 1 year period. The predicted soil loss results will be displayed in summary form in a table at the upper right of the screen, as well as graphically in the center profile layer in shades of red, white and green. Red displays show the relatively highest rates of soil loss, white regions are zero or low soil loss or deposition, and green displays are predicted areas of deposition. Hover the mouse cursor over the various regions of the slope layer to see the predicted rates of soil loss.

 

    1. Now, follow the instructors and reference the tutorial to learn more about the Windows interface software, run modifications, input file selection and modification, and output interpretation. You should gain a basic understanding of how to setup and run hillslope projects, run project sets, create new climate inputs, locate and modify soil inputs, create site-specific slope inputs, and modify and use different management inputs.

 

    1. After learning the basics of the working with the model interface, complete the exercise on the separate handout.

 

  1. Web-browser interfaces for WEPP – Forest Service (Forest Road Design)
    1. From WEPP page, click on “Forest Service WEPP Interfaces” or go directly to URL: http://forest.moscowfsl.wsu.edu/fswepp
    2. In this lab, we'll run X-DRAIN and WEPP:Road:

 

 

                                                               i.      X-DRAIN – basically a look-up table from 130,000+ WEPP model simulations, to help with design of cross-drain spacings for forest roads, depending upon road and buffer location, soil, size, and slope steepness. With a target sediment yield in mind, a user can quickly find out what spacing (and perhaps buffer length) are needed to reach the target goals.

 

Exercise: Use the X-DRAIN program to examine the sediment generation characteristics of a forest road site near Blacksburg, Virginia. The soil type is a graveled sand, road width is 14 ft., buffer length is 330 ft. and buffer gradient is 4%.. What single cross drain spacing would you recommend to prevent average annual sediment yield from exceeding 20 lbs from the contributing road area (for any slope steepness from 2-16%)? Is the X-DRAIN program sufficient for designing cross drain spacings? If not, why not?

 

                                                             ii.      WEPP:ROAD – allows more detailed direct WEPP model simulations for a road-fillslope-buffer system for different types of road designs and surfaces, and different locations, soils, and system lengths and steepnesses. The types of road designs available are shown below.

 

  

Exercise: Use the WEPP:ROAD program to determine the sediment that may potentially reach a forest stream below a road near Charleston, West Virginia. The soil is a loam, the road is insloped with a bare ditch, and a native surface, 250 ft long, 15 ft. wide, and on an average 5% grade. The fill is at 40% slope and 20 ft long, and the buffer zone at 20% slope and 100 ft. long. How much sediment is predicted to leave the buffer on an average annual basis, based upon a 10 year simulation? What would be the impact of changing the ditch type to vegetated/rocked? Additionally, how would using gravel on the road impact sediment yield? Additionally, if the forest buffer region was instead 300 ft. long, what would be predicted? And finally, if the road design was altered to reduce the road length (cross-drain spacing) to 100 ft, what would the predicted average annual sediment loss leaving the buffer be? What are the advantages of WEPP:Road as compared to the X-Drain program?

 

Run

Description

Avg. Annual Precip (in)

Avg. Annual Runoff (in)

Soill Loss from Road Prism (lb/year)

Sediment Leav. Buffer (lb/year)

1

Initial design

 

 

 

 

2

+ veg/rock chnl

 

 

 

 

3

+ graveled road

 

 

 

 

4

+ longer buffer

 

 

 

 

5

+ decr. road lgth (drain spacing)

 

 

 

 

 

                                                            iii.      Disturbed WEPP – for simulation of disturbed forest and rangeland conditions, due to timber harvesting activities or fire (not roads). This has been used a lot by forest managers to assess the impacts of recent forest fires in the western U.S., and how buffer areas might help in sediment reduction. There is not time in this lab to go into this program, however, you are encouraged to look it over on your own.