The dipole moment of a water molecule according to ab initio calculations can vary depending on the level of theory and basis set used in the calculation. However, a typical value obtained from high-level ab initio calculations is around 1.85 Debye.The experimental value of the dipole moment of a water molecule is 1.85 Debye. Thus, the ab initio calculations provide a reasonably accurate estimate of the dipole moment, which is in good agreement with the experimental value.