Nowadays, population growth, environmental constraints and climate change can adversely affect our water supply systems' ability to keep up with demand. Due to lack of unsuitable distribution and dispersion of water resources, precipitation, soil resources, etc., inter-basin transfers of water could be a solution in order to balancing between supply and demand water in different areas. In this study, the optimal designing of water conveyance from basin No-1 to basin No-2 is investigated. Water is transferred between these two dams by tunnel structure. Since the water flow through the tunnel is under pressure, increasing dam height will cause the decrease of tunnel diameter for constant water conveyance efficiency. The purpose of this study is transferring 95 % of water flow between two basins after supplying the agriculture consumption and environmental needs. Therefore, the mathematical program was developed first to solve the governing equations of water balance of reservoir and hydraulic of tunnel. Then, various strategies including different diameters of tunnel and dam height were considered and finally the best strategy from economic and technical viewpoint was proposed. The results showed that dam height of 151.2 m and tunnel diameter of 3.2 m are the economic options to convey of 95 % of the water.