Optimal Control of Salt Water Wedge by Recharge of Fresh Water

In order to develop water resources in coastal areas, reservoirs have been planed and built on river mouth. Salt water intrusion through an aquifer due to the drawdown of water level in these reservoirs should be taken into consideration when reservoirs are constructed. One of the possible approaches for the prevention of salt water intrusion is to control its movement by artificial groundwater recharge. In the present paper, state equation which describes the movement of the tip of salt water wedge is derived through the boundary element method. And the optimal groundwater recharge rate from a culvert placed within the aquifer is determined by the optimal control theory. Some examples are demonstrated to confirm the availability of the proposed method.