The development of urban communities and as a consequence of that the water necessity increment causes the construction of long water conveyance tunnels are inevitable. The Rozieh Water Conveyance tunnel with a length of 3200 meters has been excavated to transfer water from the springs' Rozieh to the Semnan province and it is planned to be a part of project to transfer water from the Caspian Sea. Due to the water leakage into the tunnel during the construction and afterwards, determination the quantity and controlling of that is of great importance. Therefore, in this research at first in accordance with hydraulic and geological consideration the tunnel route has been broken up into zones. Then, depending on the quantity of seepage into the tunnel during the construction of that the host rock permeability coefficient in each zone were determined using two-dimensional finite difference numerical simulation and the achieved results were compared to the Schleiss and Pablobarinova-Koshina analytical methods. Following, a sensitivity analysis was done on the thickness and permeability of injection zone and the permeability of concrete lining and in accordance with the quantity of seepage after cement injection, the thickness of injection region in each zone was calculated. Based on the results of sensitivity analysis, the effect of injection zone thickness variation form 3 to 6 meters on the seepage amount is negligible. However, when the difference between the permeability of the concrete lining and injection zone raises, it affects the seepage quantity more and by increasing the injection thickness from 3 to 6 meters the seepage rate will decrease up to 28 percent. The effects of hydro-mechanical coupling on the seepage rate were examined and according to achieved results the quantity of seepage into the tunnel deceases compared to the hydraulic analysis. If the cross section area of tunnel increases up to 40 percent, the seepage rate will increases up to 94.4 percent and according to the pore pressure consideration behind the injection region in each zone, the increment of injection thickness region in two zones is essential.