Chaozhou City zone is affected by the immersion caused by reservoir project built. According to numerical analysis, mono direct percolation between the two rivers is the characteristic of seepage field of the city zone. Considering this characteristic, some engineering measures such as a suspended cut off wall and relief wells were adopted and the groundwater monitoring system was set up. The monitored data and operation log since impounding are carefully analyzed. The result shows that working effect of the relief wells and the groundwater level of the old city zone are basically close to predictive state. Analysis and disposition are also given to the water overflow or confined phenomena existed in some regions of the suburb area.