The ground water movement in response to hydrological and metrological processes is simulated with saturated-unsaturated flow model for typical dyke foundation of double layers in lower and mid
dle Yangtze River. 2D model simulation results show the ground water regime of the unconfined & confined aquifer, and the regime differences under conditions with and without cut-off wall. The confined aquifer cut by the river thalweg keeps closely hydraulic relationship with the river. The cut-off wall of closure type would restrict and lower the influence of the river water level fluctuation on the ground water regime of the aquifer in the area protected by the dyke. The higher the ermeability of the confined aquifer, the more greatly the cut-off wall would change the ground water regime.The cut-off wall of closure type would make the unconfined aquifer respond less to the river water level change. 3D model simulation results demonstrate the influence of water flow moving around the lateral ends of the cut-off wall. It would lower the influence of the cut off wall on the ground water regime of confined aquifer near the ends. The more permeable the confined aquifer, the more great the by-pass flow would appear. The influence of the by-pass flow on the unconfined aquifer is little and even could be neglected.