Estimation of Parameters by Inverse Modelling

The column is divided in elementary cells with constant porosity and constant hydraulic conductivity. The modelling can be done two- or three-dimensional. A two-dimensional model demands the values of porosity (P(x,y)) and hydraulic resistance (R x,y)), which corresponds with the inverse of the hydraulic conductivity, for each elementary cell (x,y). 

The parameter sets P(x,y) and R(x,y) can be determined from the local tracer concentration and velocity distributions measured in each cross section of the column. 

The following equations are used to determine the parameters for a two-dimensional model 

If the parameter sets R x,y) and P(x,y) are determined, a modelling of the hydrodynamics with wellknown numerical algorithm is possible. 

The dimension of the elementary cells should be chosen in relation to the general aim of the soil column experiment. The minimal size of the cell is determined by the spatial resolution of the tomographic method (3x3x3 mm ). Generally it will be nec- 

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