Hi! I keep encountering problems while trying to figure out the value of Z parameter for my Annual Water Yield model.
Here’s what I have done yet and the data I’m using:
I used the ISRIC SoilGrids 2017 AWC data and used the treatment suggested in the user guide. I have both a version that’s a fraction and one that’s on a 1-100 scale as percents.
For the root restricting layer depth, I used the ISRIC SoilGrids250m 2017-03 - Depth to bedrock as suggested by user Esoth here.
I used local monthly precipitations data and combined the rasters to get the annual value per pixel.
I used figure 3A from this article referenced in the user guide to estimate the ϖ value.
I’m not sure I understand correctly what to do with these data. Do I just get the mean for my AOI for all the parameters and then proceed to do the equation presented in the user guide?
Here are the mean values I get for my AOI
Annual precipitations: 842 mm
PAWC: 0.205361
AWC: 1878.1066
ϖ: 1.6
I’m not an expert in the Annual Water Yield model so I will gladly defer to others on the forums here who have used it, but as I understand the Z parameter section of the AWY user’s guide chapter, yes, I think you could just take these values you have collected and then place them into those equations to calculate the Z parameter. There are also some other methods for estimating the Z parameter described in the paragraph, and it’s possible that the literature might also contain an equation for calculating Z parameter for your study area.
Note that, as mentioned in the UG chapter, it would also be a really good idea to compare the modeled outputs with real-world outputs and then calibrate the parameter if needed to make the outputs align more closely with reality.
