Application of the Geostatistics to Identification of the High Water Escape Potential Locations in the Tangab Dam

Tangab Dam is located 90 km south of Shiraz city and 12 km northwest of Firuzabad city on the Firuzabad river. This dam is constructed in the Zagros zone on the Podenow limestone anticline. Evidence shows that there is a possibility of water escaping from the reservoir and abutments. In this research, the exploratory data analysis includes: distribution maps, histogram, statistical parameters, and variogram was performed on the variables of RQD, Lugeon and cementing. Moreover, geostatistical modeling is used to recognize the permeable zones. These variables have high variation in the different elevations. According to omnidirection variograms, the spatial continuity of cementing estimated 100 m while pursuant to idirection variograms for RQD and Lugeon it ranged between 200-400 and 40-160 respectively. Finally, according to the simulation and uncertainty maps of the variables of Lugeon, RQD and cementing it observed that there are areas with high permeability in two locations in the center of the reservoir and northwest of the dam. Therefore, the potential of escaping is higher in these places. The study of faults in the study area showed that the density of faults is higher on the right abutment of the dam and this can increase the permeability.