  Radiative transfer equations are derived and solved for the stimulated Raman
scattering of water maser lines in the astrophysical plasmas with electron
density of about 10^6 - 10^7 cm-3. In stimulated Raman scattering, the energy
of water maser line is transferred to the side band modes: Stokes mode and
anti-Stokes mode. The Stokes mode is easily produced by backward Raman
scattering while the anti-Stokes mode is created by the interacting
intersecting masers in the plasma. The intensity of the Stokes mode is higher
than that of the anti-Stokes mode. These side band modes are proposed as
explanation for the extreme velocity features observed in the galaxy NGC 4258.
The threshold value of the brightness temperature for the Raman scattering is
about 10^16 - 10^19 K, and it is satisfied in the case of NGC 4258.
