The change in ground stresses in a rock mass has a significant influence on the aperture of rock joints, and therefore, on the water inflow to mining excavations. In this . paper, the distinct element code UDEC (Itasca Consulting Group, 1993) has been applied to simulate water flow through simplified joint geometries, considering appropriate joint apertures and in-situ stress ratios. For a rectangular excavation, a fully coupled hydro-mechanical analysis has been conducted. where joint conductivity is dependent on the change in apertures under applied stress, and conversely, the domain water pressures affect the deformation behaviour of the rock mass around the excavation. The numerical results verify that the joint aperture depends upon the magnitude of normal stress acting on the joint surface, and consequently, affects the flow through joints. This study also shows that the ratio of in-situ horizontal to vertical stress plays a major role in controlling the volume of total inflow towards the excavation.