The influence of distance between OH groups and lattice disorder of silica surface on the peak characteristics in the TPD (temperature programmed desorption) spectra of water desorption as well as on the coverage dependence of desorption activation energy has been investigated by the Monte Carlo simulation. The experimental TPD spectra of water desorption from different silica samples and coverage dependencies of desorption activation energy have been compared. The BOC-MP approach has been used to calculate the activation energies for possible associative desorption reactions which are realized during the dehydroxylation. It was established that most activation energies for associative desorption lie in the same region as those estimated from the TPD spectra.