In this paper we analyze the interference between lines of the IR spectra of water vapor, as well as the relations between intramolecular resonances (such as Coriolis, Fermi, Darling-Dennison, and more complex resonances) and nonlinear pressure dependence of line shift. Calculated results on the broadening and shift coefficients, as well as the parameters of cross-relaxation in the H2O-air, H2O-N2, and H2O-O2 mixtures at temperatures of 200 to 300 K, are given for two lines in the 0.8 mm region (634 541, 8v2 band centered at 12414.2027 cm-1 and 652 541, 3v1 + v2 band centered at 12413.9720 cm-1).