Abstarct: Most of the tunnels, especially the water conveyance tunnels are partly drilled below the water level. When the permeability of host rocks of tunnel is low, the inflow of water into the tunnel is low, and hydrogeological problems for surronding aquifers will be low. It the host rocks of tunnel has high permeability, a large volume of water enters into the tunnel during drilling, and this causes decreasing of the ground water level resulting in changing in discharge of ground water resources across the tunnel. All areas in which tunnel is being drilled below the ground water level, have not high sudden invasion potential of large volume of water into the drilling space. The potential exists in places where the rock mass permeability is extremely high. This occurs in intense porous fault zones and karstic horizons. The study area is located in south west of shahrekord, Chahar mahal and Bakhtiari province. In order to assess hydrogeologic status of the area and determining hydraulic connection between the surficial and deep parts across the tunnel, data and information related to the area were collected. Field works were carried out for structural studies. For this purpose, according to the field studies in different stops, status of joints and fractures was determined. Also by investigating of exploration boreholes drilled through the tunnel route, lithologic status and order of stratigraphic units of the area were determined. baxsed on the hydrogeochemical results obtained from boreholes and groundwater resources of the area, source of ground water was recognized. According to the lithology in different parts of the area and also by using results obtained from Lozhan and pumping tests, permeability in all parts are determined. In addition to determining the stratigraphy of the area, hydrogeological permeability has been investigated with boreholes informetion in different depths in relation to permeability. In hydrological studies according to available pizometers in the area, the general direction of ground water is determined and isopotential map is also plotted. According to the different rock units and formations recognized in the area and interpretation of structural factors and of the permeability, critical areas of groundwater invasion and hydraulic connection between surface areas and the surrounding cross tunnel area have been recognized. Entirely, the study area is divided into seven zones (3 karstic and 4 alluvial aquifers). Results from this study indicate that in some areas such as fault zones and karstic horizons, high permeability of the rock mass and the invasion of groundwater into the tunnel is more likely compared to the alluvial areas with low permeability. These studies indicate that in karstic aquifers according to the high permeability and uniform source of supply for shallow and deeper groundwater and also due to the large number of fractures and fractured zones in this section, hydraulic connection between the two part are more likely, while in other parts due to low permeability and different chemical composition of water, the possibility of the two parts begin separated, is high.