The role of geological structures on water leakage from the karst dam sites in Zagros Region, Iran

In the Zagros Region, alternative karst and non-karst formations have been folded into a series of cylindrical synclines and anticlines. Some of folds are dissected by rivers oriented approximately perpendicular to the axes, forming excellent deep valleys for dam construction. Due to an ineffective site detection and inappropriate design and construction of grout curtain, some of the dams constructed on the folds in Zagros are facing with leakage problem or have been remediated. At this research, six schematic models for probable leakage route from the reservoirs constructed in synclines and anticlines are presented by considering fold characters and dam location. Results show that in synclines, the most important leakage controlling factors are thickness and permeability of the non-karst formations located at the floor or/and abutments of the reservoir. In case of anticlines, hydraulic relation between the limbs is the most important controlling factor. It was concluded that the precise problem appears at dam sites in which the anticline limbs are hydraulically connected and karst rocks are directly exposed on the surface or covered by a thin layer of permeable sediments at the floor or abutments of the reservoir. This kind of geological setting involves a high risk of leakage problem and reservoir needs an extended water-tightening system.