Comparing Analytical solution to comsol Solution

Hello comsolers,

I defined a 2D model in subsurface flow model-using richards' equation for simple rectangle (226*1.2 meter) with imposing upper BC inward flux (because of rainfall) in homogenous, and bottom of rectangle no flow, and for the left and right of the rectangle hydraulic head B.C. with stationary condition. Attached pic1.

Analytical solution that I used is Forchheimer’s equation, attached pic2.
I run this model and I compared the analytical solution with Comsol solution, But it seems that comsol is underestimating the hydraulic conductivity than analytical solution(attached pic3). However, it was expected to have same solution for both method.

Does anybody know where is the problem and what should I do to fit the comsol solution to analytical solution, please?

Thanks in advance for your help.
Sepideh