  In the hydrodynamic approximation we obtain analytic solutions to the
Gross-Pitaevskii equation with positive scattering length which describe
expansions of the Bose-Einstein condensates in quasi-one and quasi-two
dimensional geometries. The expansion laws are expressed in terms of the
initial sizes of the condensate and the trap frequencies before release, that
is in terms of experimentally measurable parameters only. Three-dimensional
effects are estimated with the use of variational approach. The analytical
formulae show good agreement with available experimental data.
