Average annual reference evapotranspiration (ET0)

Science, Research & Data
1

Dear NCP team:
I used the modified Hargreaves equation to calculate the ET0, but the result I got is higher than annual precipitation.

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The figure above indicates that the ET couldn’t be higher than precipitation. Is the modified Hargreaves equation not suitable for my area or are there some details that I ignored?

2

Hi @frank,

It’s possible that your calculations are correct as ET0 is reference evapotranspiration. ET0 refers to the evaporative power of the atmosphere, assuming water is not scarce. InVEST models calculate ACTUAL ET (AET) based on ET0 and the precipitation input data.

-Jesse

1 Like
3

Thanks, I’ve read about articles that ET0 is higher than precipitation.

But I met a problem when I ran the model, as you can see in the uploaded file.InVEST-Hydropower-Water-Yield-log-2021-08-27–16_14_41.txt (199 Bytes)

4

I also tried the sample data. Here is the file.InVEST-Sediment-Delivery-Ratio-Model-(SDR)-log-2021-08-28–15_16_59.txt (192 Bytes)

5

Hi @frank,
From the log files it looks like the model isn’t even starting. What happens in the InVEST window when you run it? Does it appear to do anything? Does it hang forever? Are you using the latest version of InVEST (3.9.0)?

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6

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It seems like the model is stuck, and it could stop at this window for hours even a whole day. Not only my own data but also the sample data is like this.

7

@esoth Hi
Could u please check my last reply with the screenshot ? I tied .TIFF data type and .IMG type, they were not working.

8

Hi @frank,

I noticed in your logfile that you’re linking to a F drive. Is this an external hard drive? Could you try running the sample data locally on your C drive and seeing if that makes a difference?

Doug

9

Hi @dcdenu4
Thanks for your reply! I’ve worked out the problem. I just need to press the ENTER in the pure black woindow and then the model ran successfully

10

Hi @dcdenu4
I think I have a question about the resuslt. I used the sample data to run the model with different Borselli k Parameter (one is 2 and the other is 4), but the usle.tif outputs are the same. It seems not right according to the user guideline which inllustrated that the k parameter is for calibration. Does it means that different k parameters would contribute to different outputs?

11

Hi @frank -

The Borselli k parameter is used for calculating sediment export, not USLE (see equation 49 in the User Guide). Does sediment export change with different k values?

~ Stacie

12

Hi @swolny

Thanks for your reply. My results show that sediment export does change with different k values.

I’m confused about how to calculate the total retention of the area, should I plus the sediment deposition and soil retention or should I use the rkls minus the total export?

13

Hi @frank -

If you search this forum, you’ll find that this is a recurring topic, and I’m not sure that it has a definitive answer yet, but I think we’re closing in on using sed_deposition to represent sediment retention (which means that we should probably remove or at least rename the sed_retention outputs). The sed_retention outputs should not be interpreted quantitatively, but sed_deposition can be.

Here’s one of those threads, which I suggest reading through. In it, the software developer of this model says this: “I suspect you actually want the downslope sediment deposition raster. It gives a good estimate of where sediment that has run off from a pixel has been retained downstream by the vegetation on the landscape: SDR Sediment Deposition User’s Guide Section .”

~ Stacie

1 Like
14

Hi @swolny

Thanks a lot for your reply. It really help a lot for my research.

I’m going to read some references and see how other researchers deal with the result.

Kind regards.