  Some topological properties of stochastic flow $\varphi_t(x)$ generated by
stochastic differential equation in a ${\mathbb R}^d_+$ with normal reflection
at the boundary are investigated. Sobolev differentiability in initial
condition is received. The absolute continuity of the measure-valued process
$\mu\circ\varphi_t^{-1}$, where $\mu\ll\lambda^d,$ is studied.
