  Theoretical rotational quenching cross sections and rate coefficients of
ortho- and para-H$_2$O due to collisions with He atoms are presented. The
complete angular momentum close-coupling approach as well as the coupled-states
approximation for angular momentum decoupling were applied to solve the
scattering problem for a large range of rotationally-excited states of water.
Results are obtained for quenching from initial levels 1$_{1,0}$, 2$_{1,2}$,
2$_{2,1}$, 3$_{0,3}$, 3$_{1,2}$, 3$_{2,1}$, 4$_{1,4}$, 3$_{3,0}$, and 4$_{2,3}$
of ortho-H$_2$O and from initial levels 1$_{1,1}$, 2$_{0,2}$, 2$_{1,1}$,
2$_{2,0}$, 3$_{1,3}$, 3$_{2,2}$, 4$_{0,4}$, 4$_{1,3}$, and 3$_{3,1}$ of
para-H$_2$O for kinetic energies from 10$^{-5}$ to 10$^4$ cm$^{-1}$.
State-to-state and total deexcitation cross sections and rate coefficients for
temperatures between 0.1 and 3000 K are reported. The present state-to-state
rate coefficients are found to be in good agreement with previous results
obtained by Green and coworkers at high temperatures, but significant
discrepancies are obtained at lower temperatures likely due to differences in
the adopted potential energy surfaces. Astrophysical applications of the
current rate coefficients are briefly discussed.
