A Question About Infiltration Capacity Calculation in the Model

[huangwm29]

Dear professors,
I’m a hydrology student currently learning about the CWatM model and its fundamental principles. I noticed that the code in the program is inconsistent with the formula in the published article.

Specifically, the code currently calculates saturated area fraction as:
satAreaFrac = np.maximum(1 - (1 - relSat), 0) ** self.var.arnoBeta[No]
But based on the paper, I believe it should instead be:
satAreaFrac = np.maximum(1 - (1 - relSat) ** self.var.arnoBeta[No], 0)

Could this be an actual inconsistency, or might I have misunderstood the formula?
Thank you all very much for your help!

The code in /cwatm/hydrological_modules/water_demand/irrigation.py :

The equation in the paper:

[dof1985]

Dear @huangwm29

Thank you for this post. You have spotted this mistake correctly. It should actually be written as you have suggested:
satAreaFrac = np.maximum(1 - (1 - relSat) ** self.var.arnoBeta[No], 0)

The infiltration capacity is calculated twice in CWatM:

1. in soil.py (lines 421-444) in order to simulate the infiltration.
2. in water_demand/irrigaiton.py (lines 142-153) in order to limit irrigation demand.

It follows that this error affects the irrigation withdrawal estimates. We have already identified this error and provided a fix in the develop branch which will be made publicly available in the next release.

I hope this makes it clear.

Best
Dor Fridman

[huangwm29]

Thank you for the clear explanation and confirmation!