  In this paper, we study harmonic Riemannian submersions from 3-dimensional
geometries using the ( generalized) integrability data associated to an
orthonormal frame natural to a Riemannian submersion. We give complete
classifications of harmonic Riemannian submersions from Thurston's
3-dimensional geometries, 3-dimensional BCV spaces and Berger sphere into a
surface. We also give some explicit constructions of these harmonic Riemannian
submersions.
