Soil Moisture

[Hannibal]

Hi there,

I have a few questions about the calculation of retention parameter
(S) based on soil profile water content.

According to page 100 of the Manual, soil water (SW) used in the
calculation of S is the soil water content of the ENTIRE profile
EXCLUDING the amount of water held in the profile at wilting point
(WP). To calulcate the shape factors w1 and w2, parameters WP, FC and
SAT are to be determined for the ENTIRE soil profile.

1) Parameters such as Clay%, AWC, Buld density are determined for each
layer. How does SWAT generate the WP FC and SAT of the entire soil
profile?

2) Does the SW exactly equals to the SW_INIT in the output.hru? Or
SW_INIT - WP?

3) How to get the SW of each soil layer? The values in the soilst.out
are consistent with the SW_INIT or SW_END in the output.hru. In
addition, there is always an excessive layer for each HRU.

Thanks so much for your kind consideration!

Stephen

[Yan Yang]

Hi stephen:

    I also met such confused problem.

    However, I do some try on the calculation of my basins.

    I fully output all the items in the HRU and extracted the value from "SW_END" column for each HRU.

    Then I calculated the Wilting Point (WP) mannually based on the equation:

    WP=0.4*ClayPercent*BulkDensity/100

   

    One thing shocked me is that, my SW_END value in somedays are lower than the WP value.

    So I guess, high probebly that the SW_IN and SW_END here is the true Water Contnent minus the WP value.

    I will do further confirmation.

   I am also looking forward to the new message from you