A molecular outflow is one of the most conspicuous active phenomena associated with protostars, and the kinetic energy of its outflowing mass is as large as that of random motions of ambient molecular cloud, which suggests that outflow has dynamically influence on ambient molecular gas. Possible observational evidence which suggests the existence of dynamical interaction between molecular outflow and ambient molecular cloud has been detected in several star forming regions (Fukui et al. 1986; Iwata et al. 1988). Recent detections of H2O maser emission associated with low-mass protostars (e.g. Comoretto et al. 1990) also suggest that there still exist active phenomena in the low-mass star forming regions.

Molecular outflow ρ Oph-East, discovered toward a low-mass protostar IRAS 16293-2422 (Fukui et al. 1986), has been known as a site of dynamical interaction between molecular outflowing gas and ambient molecular cloud by CO and NH3 observation (Mizuno et al. 1990). Existence of several strong H2O maser spots (Wilking & Claussen 1987; Wotten 1989; Terebey et al. 1992) also suggests that active phenomena are occurring in this region. In this paper, we report our result of H2O maser observation for molecular outflow ρ Oph-East with milli-arcsecond resolution by VLBI.