Soil Loss in ton/acre or ton/hectares in EPIC windows

[Oluwatuyi Olowoyeye]

Good day Dr Luca!

I wanted to confirm if the soil loss is in ton/acre or ton/hectares.

Usually I can set the model to either a metric or English, on filling the field for metrics, the area is in hectares while filling the field for English, the area is in acres. I decided to use them in both cases to check my output, what I found is that the output values of the soil loss were the same for both English unit and metrics.

So I want to know if it does automatic conversion to a particular unit and what that unit is, because the output are the same for both. I would love to know if the soil loss is in ton/acre or ton/hectares. 

Again, as you can see in the output, I am getting zero soil loss in some years, and values seems to very low. do you have suggestions on what maybe wrong here.

[Luca]

Hi there,

All the outputs provided by the model and printed in the text files are reported in metric units. If you set the different unit, it means that you are using a user interface and the conversion is performed by the interface itself and not by the model.

Because I don't have the source code of the user interface, I cannot provide you with more information. I would suggest to use metric units in the input files too.

About the low soil losses, check if you have runoff first. Low or none runoff would be the main reason for a low soil losses.

Best,

Luca

[Oluwatuyi Olowoyeye]

Dear Luca,

Thank you so much for sharing with me.

I would look into it, however, like I had said, both metric unit and the English unit gives the same output without variation.

The runoff are okay to a very great extent. So I don't know why it still gives that low soil loss.

[Luca]

It is difficult to understand the reason of the low sediment losses without having the output files. It can be because of the setting of the parameters or because of the condition of the simulation. For instance, high soil cover can result in runoff with low sediment.

Look at the OUT file to see if you can find any clue and let me know.

Luca

[Oluwatuyi Olowoyeye]

Thank you so much!

I am using the win-EPIC actually.

[Luca]

Since you are using WinEPIC, you can find the OUT file in the folder WinEPIC/EPIC.

Let me know if you need more information.

Luca

[Oluwatuyi Olowoyeye]

Dear Luca,

We had discussion around low soil loss and in some years flat out zero.

You said you would need to check the output.

https://iastate.box.com/s/ge9nyvn75dwomprzk5dcutctrjwe7uia

I would appreciate any insight looking into the output. 

[Luca]

Hi,

I tried to download the files from the link you provided, but I got a message that the shared file or folder has been removed or it is not accessible to me.

Best,

Luca

[Oluwatuyi Olowoyeye]

Thank you!

https://iastate.box.com/s/ge9nyvn75dwomprzk5dcutctrjwe7uia

[Luca]

I don't see anything that is obviously wrong in the OUT file.

A few things you can check are:

• PEC in the control table. It should be set to 1 for a full estimation of soil erosion. Small values reduce the soil erosion, PEC=0 turn off the soil erosion.
• You can try using different approach for soil erosion (you are using MUSL) now, and adjust some specific parameters such as
  
  • PARM(23)
  • PARM(26)
  • PARM(60)
• You can also look at the soil cover. Maybe you have a lot of crop residues that are preventing soil erosion. If this is the case, you can change some parameters to increase the residues decomposition.

Let me know how this goes.

Best,

Luca

[Oluwatuyi Olowoyeye]

Thank you so much.

The PEC has always been in 1 for all my simulations. I have tried all the approach as you can see in the figure attached, they all had very minimal effect on the general output, I changed the PARM like you said, I realized it is the C but it does not make much difference in terms of the result am getting at the moment. From the figure as well, you could see the crop residue did not make any significant effect on the result. Cover should actually impact the runoff because of CN but they are all flat out, I was wondering why this could be happening! As you can see from the figures, on the average they are still mostly in the zone of zero!

I want to also know if you know a better way to carry out sensitivity analysis for all the parameters such that I can indicate range(0-15t/ha) and it runs those range, and also for the Control table, without doing them manually as it were.

[Luca]

It is difficult to understand why this happening. If you can share your input files with me, I will try to save some time to look at them and see if I can figure something out.

We do not have a tool for sensitivity analysis in EPIC.

Best,

Luca

[Oluwatuyi Olowoyeye]

Thank you so much!

I have some of the out in this link https://iastate.box.com/s/t33m9zpn77eqjx0yebuskbpz2w72w48y

Basically changed the erosion equation and made crop reside zero all through in this case!

[Luca]

Can you share the input files instead of the output files?

[Oluwatuyi Olowoyeye]

Thank you, I added the input files

https://iastate.box.com/s/t33m9zpn77eqjx0yebuskbpz2w72w48y

However, I needed to let you know, I am using WinEPIC! Thank you

[Luca]

The following input files are missing:

EPICFILE.DAT

EPICCONT.DAT

AYEAR.DAT

Before uploading the folder, put the executable in it and try to run it to see if all the files are included.

Luca

[Oluwatuyi Olowoyeye]

All is included now

https://iastate.box.com/s/t33m9zpn77eqjx0yebuskbpz2w72w48y

Thank you

[Luca]

I am now able to run the model. Probably I am not the exact same version you are using, but the model is running fine and completing the simulation.

I did a simple test using the USLE to simulate soil erosion and running the model with the management you provided me (continuous corn) and replacing corn with fallow. With corn, average simulate soil erosion was 6.6 Mg/ha while with fallow soil erosion was 32.15 Mg/ha.

Can you provide me some information on the average observed runoff (you already told me that the model is giving good results with it) and the observed sediment yield? Also, is the simulated crop biomass close to the observations?

Thanks,

Luca

[Oluwatuyi Olowoyeye]

Thank you so much!

Yes, most likely different, WinEPIC is currently 0810, do we have have an earlier version of WinEPIC other than that!

I don't know if that average soil loss you got is for a year and average about 40 years of weather Data, I provided!

I added the output I am getting specifically for each of the years in the https://iastate.box.com/s/dfyml2170jk3f47ea5ptzc6u70hz96o2

There are few concerns here, If I am simulating erosion for 40 years with it's weather data, should the soil erosion reduce down or follow a progression of increase, should increase theoretically with the exception of some extremely dry years. Again like I showed in the boxplot, I did sensitivity analysis for some of the soil parameters like crop residue, bulk residue etc..most of them didn't reveal any significant difference at various level of those parameter. For example if am using 0 crop residue, I should generate a distinct soil erosion than when I have decided on using 150!

I think Biomass is relatively okay for the area, could be better! I added that to the output as well.

[Luca Doro]

The average value I obtained is the annual average soil erosion calculated for the entire period of the simulation.

There is no unique answer to your question. The soil erosion depends on the weather and management. If both weather and management are constant, the soil erosion remains constant, or it can be reduced after the topsoil layers are eroded. Having zero crop residue at the beginning of the simulation might have a limited impact on the entire simulation since the residues are then estimated during the simulation. So, the soil cover is affect in part by the initial crop residues and then the biomass produced by the crop plays a role. I don't have the time to reproduce the test where you did a sort of sensitivity analysis.

Again, can you provide me some data on the observed soil erosion? What do you mean with "the biomass could be better"? Could it be higher? Lower?