interpolation function

Hi,

I have a problem with the interpolation function. I want to use a spatial (x,y) interpolation function for me conductivitu in the model. I import a spreadshit in the format of:
% Description: Electric conductivity, xx component
% x y ec.sigmaxx (S/m)
30 0 0.4609549171364282

but when I plot the function I get a 3D function (pic included) and the model only uses one value out of all th values.

I dont know what to do.

Please help me

Shirely