We use numerical simulations to examine the variability of flow patterns in representative fracture intersection geometries. In contrast to existing studies of perfectly orthogonal intersections, we demonstrate that more realistic geometries lead to a rich spectrum of flow patterns. Moreover, numerical solutions of the Navier-Stokes equations in these fracture intersections indicate that non-linear inertial effects become important for Reynolds numbers as low as 1--100. Such Reynolds numbers often exist in naturally fractured formations, particularly in karst systems and in the vicinity of wells during pump tests. ¿ 1999 American Geophysical Union