The value of the adiabatic correction to the Born-Oppenheimer electron
ic energy is calculated as a function of geometry for water using SCF
wavefunctions. A mass-dependent adiabatic function is combined with hi
gh-accuracy ab initio electronic structure calculations due to Partrid
ge and Schwenke. Vibrational band origins for H2O, D2O, T2O, HDO, HTO
and DTO are analysed. Unlike previous calculations on the H-3(+) syste
m, it is suggested that non-adiabatic effects are more important than
adiabatic ones in determining accurate isotope dependence of the vibra
tional band origins of water. Use of the adiabatic surface and effecti
ve masses of the heavy particles intermediate between the nuclear and
atomic masses is found to significantly improve predictions of rotatio
nal term values. The adiabatic correction is found to be of particular
importance for rotational levels with high K-a.