Optimization in Inverse problem

[fsahmed119@gmail.com]

Hello,

I am doing an inverse solution problem with a soil column. In my final solution, Hydrus tells me that the solution has converged and the mass balance error in FE solution during the final run was 0.0001 %. Before ending, it said that no further reduction in SSQ obtained, optimization stopped. However, when I see my plot between observed and predicted it shows a significant difference. I have attached the plot here and I request to kindly advise which one is valid for inverse solutions.

Faisal