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I've been using both semi steady(i.e. infiltration data)and transient flow (i.e. drainage data) to figure out the unsaturated hydraulic parameters of a waste material. From the inverse modeling results I get Diffusivity values and I'd like to know how these are calculated in Hydrus 1-D. I've been checking the manual but could not find something clearin this sense. Does anyone know where can I find the procedure/method used by the program or the underlying equations?
HYDRUS does not use diffusivities as it solves the mixed-formulation of the Richards equation. Diffusivity is used only in the water content based Richards equation. However, you can obtain diffusivity simply from its definition, which is (if I remember well) D=K dh/dTheta = K/C. You should be able to derive it by converting pressure head based Richards equation into the water content based equation. You can calculate it from values of K and C given in the I_Check.out file.
Thanks for your answer. A silly question regarding the fitting results: what are the 'Diffus' values that the program gives me along the other parameters (Pressure, log P, etc.)in the FIT.OUT file?
Thanks for your previous replies. One more query: is there any reason in particular to get only 'Soil Hyd. Properties' and 'Inverse Solution Information' as post-processing results after one inverse modelling exercise? I've been doing an inverse modelling exercise with several similar data (almost the same experiment) but once in a while I get one that doesnt show all the post-processing results (and in the DOS screen the process do not finish - and close this window - when I hit enter)
That's probably due to some nonconvergence. There can be many reasons for that. Code can take unreasonable parameters if you do not constrain them (.e.g, n>1, etc). J.
Inverse modelling: calculation of parameters
Posted - 07/21/2010 : 18:21:41
